EXAMENSARBETE INOM MATERIALTEKNIK, AVANCERAD NIVÅ, 30 HP
STOCKHOLM, SVERIGE 2016
NOVEL CONCEPT TO TREAT
WEEE FOR ENERGY AND METALS
RECYCLE BASING ON PYROLYSIS
PROCESS KHILOD SHILTAGH
KTH
SKOLAN FÖR TEKNIKVETENSKAP
www.kth.se
1
Khilod Shiltagh. Novel concept to treat weee for energy and metals
recycle basing on pyrolysis process
Supervisors:
Dr. Weihong Yang
PhD student Panagiotis Evangelopoulos
Royal Institute of Technology
School of Industrial Engineering and Management
Department of Material Science and Engineering
Division of Energy and Furnace Technology
SE-100 44 Stockholm
Sweden
2
Abstract: For the time different challenges are facing the world to stop the environment impacts and availability
of vital resources. Electrical and electronical Equipment (EEE) are contained harmful compounds which
considered to be a major threat for living organisms and might cause long term impacts on environment
(Md. Abdur Rakib, 2014). Furthermore, evolution of technology leads to production of a huge amount
of electronic waste globally, which need to be treated by innovative technologies in order to minimize
their environmental impact and simultaneously maximize their recovery rates.
Pyrolysis is a promising method for treating these fractions of waste because it can potentially convert
these waste into energy and metals.
Waste of Electrical and electronical Equipment (WEEE) contains both valuable and harmful materials,
industrial waste are various physically and chemically from household waste. To avoid the opposite
influence on environment and human health, presuppose particular recycling and treatment technique
depending on the waste type (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009).
Two types of WEEE have been processed using typical pyrolysis (Nitrogen) and pyrolysis (steam) at
600 °C, Fixed bed reactor was used in addition to a separate boiler for producing steam. Two samples
were investigated Printed circuit board- main body and -sockets.
The main focus of this work was to investigate the influence of steam presence on pyrolysis for
recovering energy and metals from recycling WEEE.
The comparison between pyrolysis at inert atmosphere and steam pyrolysis results of two various
fractions of E-Waste were prepared, in addition to literature investigation related to recycling of E- waste
and traditional routes which are followed in recovering materials nowadays was done. The results of this
study provides the incentive to continue experiments around pyrolysis process by using other methods.
Key words: WEEE. PCB. Pyrolysis. Steam. Nitrogen. Recycling metal & plastics
Acknowledgements This work is dedicated to the soul of my dear father.
I would especially like to thank my supervisors Dr. Weihong Yang and PhD student Panagiotis
Evangelopoulos from the Royal Institute of Technology (KTH) for their generous support and
precious guidance which were extremely valuable for my study both theoretically and
practically.
To my brother who encouraged me to go back to study after interruption about 25 years, to you
Ghassan, thank you. I would like to thank my family and friends.
To all of you thank a lot for the unlimited support given to me.
Khilod Shiltagh
Stockholm October 2016
3
Contents Abstract: .............................................................................................................................................................................. 2 Acknowledgements ............................................................................................................................................................ 2 Contents .............................................................................................................................................................................. 3
TABLE OF DIAGRAMS ...................................................................................................................................................... 4
LIST OF TABLES .................................................................................................................................................................... 4 1. INTRODUCTION ............................................................................................................................................................... 5 2. OBJECTIVES OF THIS WORK ............................................................................................................................................. 8 3. WASTE OF ELECTRIC AND ELECTRONIC EQUIPMENT ..................................................................................................... 8
3.1 Polymers High Complex Fraction .................................................................................................................... 10
3.2 Printed Circuit Boards...................................................................................................................................... 10
3.3 Compositions of WEEE .................................................................................................................................... 12
3.4 Flame retardants ............................................................................................................................................. 13
4. TRADITIONAL METALLURGICAL PROCESSES FOR THE RECOVERY OF METALS FROM E-WASTE .................................. 15 4.1 WEEE Standard Mechanical Pre-processing ...................................................................................................... 16
4.1.1 Boliden .................................................................................................................................................... 17
4.2 Pyro- metallurgical process (Thermal treatment) .......................................................................................... 18
4.2.1 Disadvantages of pyro-metallurgical process......................................................................................... 18
4.2.2 Copper smelting route ............................................................................................................................ 19
4.3 Hydro- metallurgical process ..................................................................................................................... 20
4.3.1 Disadvantage of hydrometallurgy .......................................................................................................... 21
4.4 Electrochemical treatment ............................................................................................................................. 21
5. THERMAL DEGRADATION OF PLASTICS ........................................................................................................................ 22 5.1 The Mechanism of Thermal Degradation of plastics ...................................................................................... 22
5.2 Gasification ...................................................................................................................................................... 23
5.2.1 Advantages of gasification...................................................................................................................... 24
5.3 Pyrolysis technology ........................................................................................................................................ 25
5.3.4 Advantage of pyrolysis............................................................................................................................ 27
5.3.5 Pyrolysis technology and reactors .......................................................................................................... 29
5.3.6 Degradation levels .................................................................................................................................. 30
5.3.7 Dehalogenation ...................................................................................................................................... 31
6. EXPERIMENT INVESTIGATION ....................................................................................................................................... 33 6.1 Experimental Methodology for PCB s pyrolysis .............................................................................................. 33
6.2 Characteristics of the pyrolysed WEEE sample ............................................................................................... 33
6.3 Sample preparation ......................................................................................................................................... 33
6.5 Experimental facility ........................................................................................................................................ 35
6.6 The Procedure of Typical Pyrolysis .................................................................................................................. 37
6.7 The procedure of steam pyrolysis ................................................................................................................... 39
6.8 The procedure of Measurement ..................................................................................................................... 41
6.9 Dichloromethane CH2Cl2 ................................................................................................................................ 43
6.10 Data collection.................................................................................................................................................. 44
7. RESULTS & DISCUSSION ................................................................................................................................................ 46
7.1 Mass loss (solid residue).................................................................................................................................. 47
4
7.2 Analysis of process outcome gases ................................................................................................................. 47
7.2.1 Composition of outcome gases .............................................................................................................. 48
7.3 Analysis of process outcome Liquids............................................................................................................... 50
7.3.1 Comparison the amount of produced liquid .......................................................................................... 51
7.4 Mass balance ................................................................................................................................................... 52
8. CONCLUSION ................................................................................................................................................................. 55 References:........................................................................................................................................................................ 56
TABLE OF DIAGRAMS
Figure 1- Estimated global quantity of E-waste between 2010 and 2018 .......................................................................... 6 Figure 2- Saving energy for making certain elements by using recycling ......................................................................... 7 Figure 3- Classification of E-waste generated globally in 2014 (UNU-IAS, 2014) ........................................................... 9 Figure 4- Average composition of the plastics fraction in EU-2012 .............................................................................. 10 Figure 5- Composition of typical Printed Circuit board and the metal fraction .............................................................. 11 Figure 6- Composition of collected E-waste (Evangelopoulos, ....................................................................................... 12 Figure 7- Composition of critical material in collected E-waste ..................................................................................... 13 Figure 8- The traditional ways for recovering metals from E-scrap ................................................................................ 15 Figure 9- Thermal decomposition of organic material in differ temperature .................................................................. 22 Figure 10- Required feedback energy loop for sustained burning ................................................................................... 23 Figure 11- Closing the loop by recovering energy and metals through pyrolysis process .............................................. 27 Figure 12- An image of experiment facility ...................................................................................................................... 35 Figure 13- Sketch of laboratory pyrolysis facility ............................................................................................................ 36 Figure 14- Vertical semi-batch type cylinder reactor covered by electrical heater utilized in experiments ..................... 37 Figure 15- Image of Balance scale that used for samples and tar measurement vessels .................................................. 37 Figure 16-Image of tar collection equipment ................................................................................................................... 38 Figure 17- Weight scale used for tar measurement vessel in steam pyrolysis ................................................................. 40 Figure 18- Gas measuring vessels connected to other buckets ......................................................................................... 40 Figure 19- Agilent 490 micro- GC ................................................................................................................................... 41 Figure 20- Schematic drawing shows increasing temp of samples according to time...................................................... 42 Figure 21- The GC-FID/MS analyzer used for liquid analysis ........................................................................................ 42 Figure 22- A separatory funnel ........................................................................................................................................ 44 Figure 23- Results of Pyrolysed PCB mb by N2 and steam ............................................................................................. 46 Figure 24- Products of treating PCB sockets by N2 & steam pyrolysis ........................................................................... 46 Figure 25- Amount of outcome gases is different according to sample & experiment type............................................. 48 Figure 26- Comparison of gases produced by pyrolysis PCB - mb using N2 & steal ..................................................... 48 Figure 27- Comparison of gases produced by pyrolysis PCB sockets using N2 & steam................................................ 49 Figure 28- Amount of produced oil from pyrolysis PCB- mb .......................................................................................... 50 Figure 29- Amount of produced oil from pyrolysis PCB- sockets ................................................................................... 50 Figure 30- Comparison of amount of phenol as shared product among all experiments ................................................. 51 Figure 31- Differ in products amount was resulted from typical & novel pyrolysis ........................................................ 52 Figure 32- Illustrate differ dominate phase in the four experiments ................................................................................. 53 Figure 33- Different in amount of pyrolysis products according to experiment´s type .................................................... 54
LIST OF TABLES Table 1- Technique halogenated fire retardant (Diaz & Friedrich, 2015) ........................................................................ 14 Table 2- Proximate composition analysis of printed circuit boards both samples ............................................................ 34 Table 3- Required time to approach elevated temp in both pyrolysis............................................................................... 41 Table 4- Different agents used to prepare liquid samples before GC-FID/MS analyzer .................................................. 43 Table 5- Experimental conditions for the two types of pyrolysis ..................................................................................... 45 Table 6- The difference in mass loss percentage of solid residue at 600 °C .................................................................... 47 Table 7- Mass balance of the four experiments ................................................................................................................ 52 Table 8- Illustrates proportion of higher yield according to sample- and experiment –type ............................................ 54
5
1. INTRODUCTION A great deal of interest is generated by combination pyrolysis as thermal process to recover energy and
metals from the recycling of Electrical and Electronical Equipment (Tuncuk, Yazici, Akcil, & Deveci.,
2012). Acording to previous studies, pyrolysis process has higher potential for decreasing air pollution
and increasing resource recovery compared with the existing recycling techniques which help to recover
a limit number of metals (Lewis, 1967). Furthermore these conventional ways are incapable in
recovering critical high-tech metals like gallium (Ga), germanium (Ge) and tantalum (Ta). (Hense, Reh,
& Franke, 2015).
As a result of the revolution of informatics technology, the innovation cycles become shorter and hence
high amount of Electrical and Electronic Equipment are produced over the world. Moreover the variation
in user patterns, economic growth and the expansion of markets in differ parts of the world, is the reason
that the useful life of these devices become shorter and thus globally increasing in quantities of E- waste
is generated. (Abdul Khaliq, 2014) (Hense, Reh, & Franke, 2015)
In the industrial countries the amount of WEEE is growing faster, since the collected amount of WEEE
in the EU-27 is increased in about 7 wt. % per year between 2007 and 2012 (Hense, Reh, & Franke,
2015). In Sweden the amount of collected E-waste was 697,500 tons from 2004 to 2008 with increasing
about 39 % between these two years (Elretur, 2009). The production of E-waste is expected to increase
by 45% in Europe between 1995 and 2020. (Abdul Khaliq, 2014).
The total global quantity of WEEE that generated in 2014 is estimated by 41.8 million metric tons (Mt)
and the essential materials value of gold, copper and plastics contents in this WEEE is evaluated to be
48 billion euro (UNU-IAS, 2014).
According to previous studies, different metals, critical metals and polymers are found in collected
WEEE, in addition to complex compounds which are hazardous to both environment and human health
(Hense, Reh, & Franke, 2015).
That´s why huge challenges are facing proposed process of pyrolysis such as made better both of the
recovery of valuable metals as well as the process control, increasing recycling capacity and better
control of hazardous substances. (Diaz & Friedrich, 2015)
Printed circuit boards (PCBs) are common part in different electric systems that create for various usages
(Jinhui Li, 2010). The volume of PCB in the mobile phone represent between 2% and 30% of the total
weight. (Tangea Lein, 2004)
The characteristics of plastic such as toughness, easy fabrication, flexibility, physical properties, low
electrical and thermal conductivity, make them in the beginning of rival materials that employed in
important applications (Singh & Sharma, 2007) (Bhaskar, 2004). In this case the environmental impact
is higher if these materials end up on landfills (Bhaskar, 2004).
6
Negative or positive effects are associated with the way of handling E-waste (Md. Abdur Rakib, 2014).
In other words the treatment ways of E-waste has an important role to decrease the impact of pollutants
elements on environment for instance dioxins that produced by burning a cable at low temperature is
higher 100 times than household waste combustion (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009).
The traditional recycling routes that followed during last two decades leads to loss the precious metals
and that influence the process economy (Abdul Khaliq, 2014). Some of critical metals such are Tungsten
(W), Gallium (Ga), Palladium (Pd) and Cobalt (Co) are not recovered yet which means losing a
secondary resource to supply these metals from E-waste (Abdul Khaliq, 2014). While base metals like
Iron (Fe), Aluminium (Al) and Copper (Cu) are recovered by different routes (Hense, Reh, & Franke,
2015). The total demand in the EU to the critical metals is about 2000 ton/year that can be covered by
recovery E-waste. The value of amount of Pd and Co that find in E-waste according to current market
data in 2014 is equivalent to 215 Mio. €. (Hense, Reh, & Franke, 2015)
Precious metals (PMs) available in E-waste is more than that found in their primary ores for instance the
recovered gold from one tonne of personal computers classified as scrap is more than that extracted from
17 tonne of gold ore. I.e.The recovery of PMs is the vital reason to encourage the recycling of all amount
of E- waste (Abdul Khaliq, 2014). In this case recycling of WEEE has been chosen as beneficial way
for recovering metals and saving energy compared to the extraction of virgin ore (Kantarelis,
Evangelopoulos, & Yang, 2015).
Diagram (1) below shows estimated global quantity of E-waste in Mt between 2010 and 2018, according
to the United Nation University report 2014, a great challenge is facing both developed and developing
countries for creating the particular E-waste collection and treatment systems (UNU-IAS, 2014).
Figure 1- Estimated global quantity of E-waste between 2010 and 2018 (UNU-IAS, 2014)
33,8 35,8 37,8 39,8 41,8 43,8 45,747,8 49,8
0
10
20
30
40
50
60
10 11 12 13 14 15 16 17 18
E-w
aste
(M
t)
year
GLOBAL QUANTITY OF E- WASTE
7
The total amount of E-waste that declared is not included the E- waste that are discarded along with
household. Which means actually higher amount of WEEE is generated over the world (Md. Abdur
Rakib, 2014), and environmental problems are exacerbated (Gkaidatzis, Aggelakoglou, & Aktsoglou,
2009).
The purpose of this report is to create awareness among the importance of pyrolysis as process that can
be more effective compared with current applied techniques such as incineration, acidic leaching or
direct leaching for small electronic devices after mechanical separation process (Lewis, 1967). Pyrolysis
is a thermo-chemical conversion process (Hense, Reh, & Franke, 2015), the thermal decomposition is
happened by using the action of heat in absence of oxygen. The organic compounds yields from the
process are Char, liquids, fuel gas and water in liquid or gaseous phase depends on the process final
conditions. (Lewis, 1967)
Typical pyrolysis is a lab scale process and not applied in the industrial sector yet. Some of the reasons
behind that is that the use of inert gas (nitrogen) required can increase the cost as well as the
technological demands are hard to overcome (Jasminská, Brestovič, & Čarnogurská, 2013); Nitrogen
loss its feature as inert gas after 1000 °C (Wojkiewicz, 2015). In addition to perform the process
compare with the value of outcome products, the process was applied in fixed bed reactor, i.e low
capacity and high cost. That´s why there is an urgent need to develop a new pyrolysis process with
less cost and higher value products (Jasminská, Brestovič, &
Čarnogurská, 2013).
According to the U.S Environmental Protection Agency using recycled materials is an important manner
to save energy compared to extraction of virgin materials. The diagram (2) below shows percentage of
saved energy for certain metals and materials (Abdul Khaliq, 2014).
Figure 2- Saving energy for making certain elements by using recycling (Abdul Khaliq, 2014)
Aluminum copper Iron & steel
Lead Zinc Paper Plastics
1 2 3 4 5 6 7
Energy saving (%) 95 85 74 65 60 64 80
0 10 20 30 40 50 60 70 80 90
100
The percentage of energy saving from recycling compare with
extraction of virgin materials
Energy saving (%)
8
2. OBJECTIVES OF THIS WORK 1) Literature investigation including recycling of WEEE as well as the traditional methods that are
followed nowadays in recovering metals.
2) Making a comparison between the results of using Nitrogen and Steam during thermal treatment
(Pyrolysis) for two various fractions of PCBs- main body and -sockets in 600°C is the another
aim of this work. The following tasks are taken into consideration:
Experimental investigation for the two types of pyrolysis to enhance the understanding of the
fundamentals of WEEE thermal conversions.
Make mass balance for two processes of pyrolysis to determine composition of pyrolysis
products.
Experiments performed at low temperature 600°C, nevertheless the usage of steam is considered
as pyrolysis.
3. WASTE OF ELECTRIC AND ELECTRONIC EQUIPMENT WEEE includes a wide range of electric and electronic equipment with different sizes, purposes and
applications, which are worthless to their owner. (Abdul Khaliq, 2014) Diagram (3) in the next page
shows various devices generated globally in 2014 (UNU-IAS, 2014). All items of electrical and
electronic equipment (EEE) that unwanted by their owner as well as not intend to re-use them are
classified as E-waste.
In general, the term E-waste covers ten categories provided by the Directive 2002/96/EC on E-waste as
in bellow (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009) (Kantarelis, Evangelopoulos, & Yang, 2015):
I. Large household appliances (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009), including
cooling and freezing equipment (refrigerators, freezers, heat pumps and air conditioners
(Abdul Khaliq, 2014) as well as washing machines are also the typical equipment)
(Kantarelis, Evangelopoulos, & Yang, 2015).
II. Lighting equipment (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009) (Kantarelis,
Evangelopoulos, & Yang, 2015). Typical equipment comprises straight fluorescent,
fluorescent lamps, compact fluorescent lamps, LED lamps (light-emitting diode) and high
intensity discharge lamps.) (Abdul Khaliq, 2014)
III. Consumer equipment and photovoltaic panels (Gkaidatzis, Aggelakoglou, & Aktsoglou,
2009) (Kantarelis, Evangelopoulos, & Yang, 2015).
9
(Typical equipments are copying equipment, photovoltaic panels and clothes dryers (Abdul
Khaliq, 2014). Added to these Products and equipments for the purpose of recording,
reproducing sound or images (Kantarelis, Evangelopoulos, & Yang, 2015).
IV. Small household appliances (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Typical
equipment microwaves, toasters, electric kettles, radio sets, small electrical and electronic
tools and electric shavers (Abdul Khaliq, 2014). In addition to appliances that are used for
sewing, knitting, and weaving (Kantarelis, Evangelopoulos, & Yang, 2015).
V. IT telecommunication equipment (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009).
Typical equipment are comprises mobile phones and televisions, personal computers,
pocket calculators, telephones and printers (UNU-IAS, 2014) (Kantarelis,
Evangelopoulos, & Yang, 2015) (Abdul Khaliq, 2014).
VI. Electrical and electronic tools, stationary industrial tools are accepted from this category
(Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009) As well as tools for welding, shearing,
screwing and nailing (Kantarelis, Evangelopoulos, & Yang, 2015).
VII. Automatic dispensers (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Include all
appliances that used in this sector (Kantarelis, Evangelopoulos, & Yang, 2015).
VIII. Medical appliances (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Devices that used in
medical employment (Kantarelis, Evangelopoulos, & Yang, 2015).
IX. Toys and sports equipment (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Including all
electrical toys and video games (Kantarelis, Evangelopoulos, & Yang, 2015).
X. Monitoring and control devices (Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Different
appliances that used in household and industrial installations such as adjusting devices,
heating regulators, smoke detectors, and measuring weight (Kantarelis, Evangelopoulos,
& Yang, 2015).
Figure 3- Classification of E-waste generated globally in 2014 (UNU-IAS, 2014)
Lamps Screens Small ITSmall
equipmentLarge
equipment
Cooling &freezing
equipment
1 6,3 3 12,8 11,8 7
02468
101214
Am
ou
nt i
n M
T
E-waste type
Amount of global E-waste 2014
10
3.1 Polymers High Complex Fraction The complex fraction of polymers that can be associated with environmental and health hazards
(Richards, 2015) is consist of different kinds of plastic components such as polycarbonate-ABS
(PCABS), polystyrene (PS), polyethylene (PE), acrylonitrile-butadiene-styrene (ABS), styrene
acrylonitrile (SAN), polyvinyl chloride (PVC) or ethylene-propylene-diene monomer (EPDM) as in
diagram (4) below which shows collected WEEE in Europe for year 2012 contains plastics in about 22
wt. % of the total amount (Hense, Reh, & Franke, 2015). The polymeric matrix also includes quantities
of halogen compounds which employed as flame retardants (Diaz & Friedrich, 2015).
Figure 4- Average composition of the plastics fraction in EU-2012 (Hense, Reh, & Franke, 2015)
3.2 Printed Circuit Boards PCBs are a common part in all Electronics Equipment and have the most complex fraction of the waste
electrical and electronic equipment.
Production of PCBs is increased over the past several decades according to the rapid development and
expansion in the electronic industry (Jinhui Li, 2010). For that reason the importance of recovering PCBs
is increased in time hence the volume of PCBs is growing worldwide from 90,000 metric tons (mtons)
in 2003 up to 156,000 mtons in 2009 (Tangea Lein, 2004).
PCBs scraps are generally classified into three groups according to type of precious metal content. They
are indicated in H (high-grade), M (medium-grade) and L (low grade) scrap (Goosey & Kellner, 2002):
1- Low grade material (L): include television boards, laminate Offcuts and power supply units that
structured of heavy ferrite transformers and large aluminum heat sink.
8 , 9
6 , 3
1 3 ,
, 7 1
1 , 1
9 0 ,
0 , 6 , 0 5
, 0 3 1 , 2
Composition of the plastics fraction in collected E - waste
ABS
PS
PCABS
PE
PVC
PP
SAN
PC
EPDM
11
2- Medium grade scrap (M): high precision apparatus that content precious metal with little
aluminum.
3- High grade material covers high precious metal content boards, optoelectronic devices,
integrated circuits (ICs) with gold-containing and special components such as gold pin boards,
palladium pin boards and thermally coupled modules from mainframes (Goosey & Kellner,
2002).
According to the recycling process, PCBs are divided into two various fractions, the main body of the
printed circuit boards (PCBs mb), this part contains metals used for connecting the different components
of the PCBs, plastic resign used to enhance the strength of the PCBs and the ceramic base of the PCB
(Evangelopoulos, 2015). The high conductivity of tin, silver and copper is the reason for using them in
coating the PCBs (Abdul Khaliq, 2014).
The second fraction is plastic sockets (PCBs sockets) which is used for connecting the independent
elements and components of the computers” conductors, CPU and ram memory” (Evangelopoulos,
2015). Pyrolysis is used as a pre-processing method for both fractions of PCBs to allow a better
separation of the metallic and non-metallic fraction. (Diaz & Friedrich, 2015)
The waste of PCBs consist of various hazardous components in addition to the precious metals that is
why the treatment and recycling of PCBs by using traditional methods cause a negative impact for the
environment (Mankhand, Singh, Gupta, & Das, 2012). The various in types of electric and electronic
appliances, manufacturers and ages of these devices have the main role for the differences in
composition of PCBs. The typical PCBs as in diagram (5) below includes 40% of metals, 30% of
organics and 30% ceramics (Luda, 2011). In addition the metallic fractions in PCBs are being made up
of about 16% copper, 4% solder (tin-lead), 2% nickel along with 3% iron and ferrite, precious metals:
0.03% gold, 0.05% silver, and 0.01% palladium, while tantalum are usually linked with plastic cover or
ceramic (Diaz & Friedrich, 2015) (Luda, 2011).
Figure 5- Composition of typical Printed Circuit board and the metal fraction (Abdul Khaliq, 2014)
(Luda, 2011)
% 40
% 30
% 30
Printed circuit boards
contents
metals plastics ceramics 0 % % 5 10 % 15 % 20 %
Copper
Solder
Nickel
Iron
Gold
Silver
Palladium
Composition of metal fraction in PCB
12
3.3 Compositions of WEEE Different metals, critical metals and polymers are found in collected WEEE that is profitable when they
are recycled, in addition to complex compounds which are hazardous for both environment and human
health (Hense, Reh, & Franke, 2015).
The type and age of the electronic equipment lead to change chemical composition of E-waste
(Gkaidatzis, Aggelakoglou, & Aktsoglou, 2009). Diagram (6) below illustrates the average composition
of the collected WEEE according to Swedish Environmental Protection Agency, 2011 (Evangelopoulos,
Efthymios, & Yang, 2015).
Figure 6- Composition of collected E-waste (Evangelopoulos, Efthymios, & Yang, 2015)
The analysis of E-waste components shows that different compounds are present such as plastic and
other organic polymers as well as the metals like lead, iron, copper, aluminium, nickel, cadmium,
chromium, selenium etc. Some electronic components such as [resistors, transistors] were found to be
suitable for reuse and other metals can be converted by separation from solid residue (Antrekowitsch &
al, 2006).
Metallic fraction in WEEE includes a mixture of different metals; Diagram (7) in the next bage shows
the proportion of these metals as well as plastic fraction and amount of refractory oxides that found in
collected E-waste (Gramatyka, Nowosielski, & Sakiewicz., 2006).
13
Figure 7- Composition of critical material in collected E-waste (Gramatyka, Nowosielski, &
Sakiewicz., 2006)
3.4 Flame retardants Problems that occur in recycling process of E-waste are related to flame retardants which represent about
one quarter of E-waste plastics. One third of quantity amount of these flame retarded are based on
halogens. The amounts of halogens Br & Cl in plastic fraction represent about 10.9 wt. % and 57.8 wt.
% respectively of the total plastic weight of WEEE.
Different toxic substances such as poly-brominated dibenzo dioxins and furans (PBDD/F),
polyhalogenated aromatic hydrocarbons (PHAH) and polycyclic aromatic hydrocarbons (PAH), are
created by degradation of those halogenated flame retardants (Hense, Reh, & Franke, 2015).
The use of poly-brominated biphenyls (PBB) and poly-brominated diphenyl ethers (PBDE) as flame
retardant in producing EEE are limited in Europe according to the Directive 2011/65/EU. Despite many
materials which mainly phosphorous- or nitrogen -based are developed to replace hazardous substances,
however the fabrication of halogenated flame retardants is growing (Hense, Reh, & Franke, 2015).
The use of flame retardants is necessary and the reason is when solid polymers are heating, thermal
degradation is currying out which is equivalent to burning of non-organic materials. Smaller molecules
in the gas phase are resulted from this degradation;
14
This reaction would be exothermic in presence of oxygen. The purpose of adding flame retardants
elements to polymer is hydrogen halides are released in gas phase and thus it captures the active radicals
and replaces them by less active halogen radicals. This procedure leads to regenerating of hydrogen
halides as shows in table (1) below (Diaz & Friedrich, 2015):
Table 1- Technique halogenated fire retardant (Diaz & Friedrich, 2015)
𝑓𝑙𝑎𝑚𝑚𝑎𝑏𝑙𝑒 𝑔𝑎𝑠𝑒𝑠
?→𝐻°+𝑂𝐻°→ 𝐻𝑒𝑎𝑡
Halogenated fire retardant HXg X=Br, Cl
HX + H° H2 + 𝑋° flame poisoning
HX + OH° H2O + °𝑋 flame poisoning
RH + 𝑋° 𝑅°+ HX regeneration
Increasing the temperature leads to thermal decomposition of halogenated flame retardants (Hense, Reh,
& Franke, 2015) and form toxic PBDD/F from the poly-brominate diphenyl ethers (DBPE and TBPC)
which form a part of the additive flame retardants (Diaz & Friedrich, 2015), that causes the formation
of highly toxic hydrocarbons and dioxins (Hense, Reh, & Franke, 2015).
The substrate and pyrolysis conditions decide if halogens Br and Cl plus antimony are collected in
pyrolysis products (gas, oil and solid residue). (Diaz & Friedrich, 2015)
Inorganic compounds like antimony trioxide (Sb2O3) and magnesium hydroxide Mg(OH)2, or aluminium
hydroxide Al(OH)3, are often incorporated with the halogenated flame retardants. For example,
catalysts for recombination of hydroxyl, hydrogen and oxygen are formed by the decomposition of
Sb2O3. In both the condensed and the gaseous phase of a flame, (Sb2O3) is working as synergist (Hense,
Reh, & Franke, 2015).
15
4. TRADITIONAL METALLURGICAL PROCESSES FOR THE
RECOVERY OF METALS FROM E-WASTE At present time industrial processes of recycling of E-waste are divided into two main routes pyro-
metallurgical- and combined pyro- hydrometallurgical -process (Navazo, Méndez, & Peiró., 2013).
Energy needed to recover metals by using pyro-metallurgical and combined pyro-hydrometallurgical is
7,763 and 7,568 MJ/tone of mobile phones, respectively. The both methods are consumed almost the
same amount of energy (Navazo, Méndez, & Peiró., 2013). Various treatments are proposed for recovery
of metals from WEEE, because this type of west are heterogeneous and complex (Tuncuk, Yazici, Akcil,
& Deveci., 2012).
Recycling facilities are choosing carefully with highest level of development in order to recover precious
metals as well as to isolate dangerous materials professionally. In this case choosing a suitable recycling
facility leads to close the loop of precious metals in addition to minimize the environmental impact that
appeared from large quantities of E- waste (Abdul Khaliq, 2014). Diagram (8) below shows traditional
methods that followed in recovery of metals from E- waste (Tuncuk, Yazici, Akcil, & Deveci., 2012).
To take out pure metals from BMs, better to combine both of pyro- and hydro- metallurgical process,
starting with pyro. where partial recovery and purity take place then followed by hydro and
electrochemical methods (Abdul Khaliq, 2014).
Figure 8- The traditional ways for recovering metals from E-scrap (Tuncuk, Yazici, Akcil, & Deveci.,
2012)
16
4.1 WEEE Standard Mechanical Pre-processing Mechanical pre-treatment step is needed for the recycling of valuable metals from E-scrap by
hydrometallurgic methods (Tuncuk, Yazici, Akcil, & Deveci., 2012). Recycling and recovering metals
that the E- waste contains requires special pre-processing techniques because of the diversity and
complexity of WEEE materials (Diaz & Friedrich, 2015).
In general, Through recycling of E-waste mechanical separation occurs to segregate Iron, Aluminum,
and Plastic parts, this operation leads to higher a risk of losing the PMs, because the PCBs are designed
that PMs is fixed with non-ferrous metals and plastics. In this case, better recovering of PMs obtains
when pieces of Fe, Al, and plastics are taking with the copper fraction.
Higher environmental efficiency creates when the mobile phones is direct smelting comparing with
fragmented mobile phones components. ( i.e smelt PCBs in furnace directly will leads to increase the
recovered PMs because PMs are mostly treated in copper smelters, moreover combustion of plastic will
supply energy that will replace coke partially in addition this will be a good reason to recycle Ewaste
and in this case the loop of metal will be closed. Take into account separating batteries in both cases to
release hazardous materials that emit from batteries (Abdul Khaliq, 2014).
In other words it is not favourable to apply standard mechanical pre-processing in case of recovery
precious metals from PCBs because under strong shredding process these metals are converted to dust
(Diaz & Friedrich, 2015).
During mechanical processing the metals fraction is separated from E-waste. To regain the residual
metals, the major processes such as Hydro- Pyro- and electro- metallurgical methods are utilized after
mechanical separation (Abdul Khaliq, 2014). Standard Mechanical Pre-processing is doing according to
the following steps:
1- First step is dismantling and sorting processes (Kantarelis, Evangelopoulos, & Yang, 2015) is
covered of E-waste sorting and separating into various fractions such as hazardous elements
(capacitors, batteries, LCDs, PCB), plastic, metals (iron, aluminum, copper, etc.) (Diaz &
Friedrich, 2015) (Tuncuk, Yazici, Akcil, & Deveci., 2012). This step is important to improve
recycling capacity, increase of economic potential of E-waste by pre-concentrating of precious
metals as well as to get rid of hazardous components (Tuncuk, Yazici, Akcil, & Deveci., 2012).
2- Shredding and Grinding (Kantarelis, Evangelopoulos, & Yang, 2015) or Size reduction stage to
tear and fragment E-waste by using shredders, mills (ball or hummer) (Diaz & Friedrich, 2015)
(Tuncuk, Yazici, Akcil, & Deveci., 2012). The size of shredded E-waste is generally below 5
mm or 10 mm (Kantarelis, Evangelopoulos, & Yang, 2015); the second step is performed to
collect metal bearing components before metal recovery process (Tuncuk, Yazici, Akcil, &
Deveci., 2012). Type of recovery route determines the extent of size reduction in second stage.
17
Hydro-metallurgical method is probable to use for fine size reduction to get efficient recovery
of metals from E-waste. On the other hand pyro-metallurgical is appropriate for relatively coarse
metals (Tuncuk, Yazici, Akcil, & Deveci., 2012).
3- Physical separation or mechanical separation is subsequent stage where depends on principle
that various materials have differ physical properties (Diaz & Friedrich, 2015) (Tuncuk, Yazici,
Akcil, & Deveci., 2012). The physical characteristics such as shape, density, weight, magnetic
characteristics and electric conductivity are performed in the E-waste sorting during this step
(Kantarelis, Evangelopoulos, & Yang, 2015). The traditional methods that used for separation
of material are (Diaz & Friedrich, 2015) (Tuncuk, Yazici, Akcil, & Deveci., 2012):
a) Magnetic separation to separate ferrous parts from nonferrous materials.
b) Eddy current separation, this route is used to release nonmagnetic metals.
c) The third method step is gravity or density separation to separate heavier materials from lighter.
4.1.1 Boliden Extraction of metals from WEEE has been done by using the traditional routes through the Rönnskär
Smelters and the Kaldo furnace at Boliden, Sweden. (Abdul Khaliq, 2014) The process that followed in
Boliden is pyro- metallurgical process, which includes a smelter, and converter, then anode furnace, and
electrolytic refining (Navazo, Méndez, & Peiró., 2013). During process is used differ scrap consist of
electrical industry and nonferrous, that added in different stages according to the purity and the final
product requirement (Abdul Khaliq, 2014).
The Kaldo furnace is utilized to combust PCB and nonferrous fraction of WEEE while the electric
smelting furnace is used to treat the copper rich concentrate fraction of crushed WEEE (Kantarelis,
Evangelopoulos, & Yang, 2015). Drying, roasting, smelting, converting and refining are the main steps
in the Rönnskär Smelter (Abdul Khaliq, 2014).
The required process energy is gained from degradation of plastic. A mixture of elements such as Cu,
Ag, Au, Pt, Pd, Ni, Se, and Zn, are produced through the Kaldo furnace (Kantarelis, Evangelopoulos,
& Yang, 2015).
Utilized farther treatments are done through the anode casting plant, the electro-refinery, and the
precious metals plant to recover these elements (Kantarelis, Evangelopoulos, & Yang, 2015). More than
100,000 tons/year of waste (including E-waste) are recycled at Boliden. Scrap contain high copper
content is fed into converter directly, while in Kaldo furnace is fed E-waste with low grade. Kaldo
furnace feed are mix lead concentrate and E- waste, they combusted with the supply of oxygen and oil
(Abdul Khaliq, 2014).
18
4.2 Pyro- metallurgical process (Thermal treatment) Pyro- metallurgical process has been utilized as traditional technology for recovering metals from
different waste materials in last two decades (Abdul Khaliq, 2014). This route consists of pre-treatment
of E-waste (Tuncuk, Yazici, Akcil, & Deveci., 2012) then incineration and smelting of enriched metal
by using blast furnace or plasma arc furnace (Gramatyka, Nowosielski, & Sakiewicz., 2006) to obtain
copper bullion, (Tuncuk, Yazici, Akcil, & Deveci., 2012) thereafter to get high purity copper the last
product undergo to electrolytic refining and then collect slims from copper electro- refining.
While recovering of precious metals such as Ag, Au, Pt, Pd, Ru, Ir and Rh is done after that (Tuncuk,
Yazici, Akcil, & Deveci., 2012), the process is followed by further refining through drossing, sintering,
melting and high temperature reactions in a gas face (Gramatyka, Nowosielski, & Sakiewicz., 2006) in
order to reduce environmental problems that creates from halogenated flame retardants which utilized
in production of PCBs (Tuncuk, Yazici, Akcil, & Deveci., 2012).
The process includes a combustion in a furnace to get rid of plastics and other organic materials which
are converted to volatile compounds or slag in refractory oxides, in addition to generate a solid residue
with concentrate metal in it. Only alloys are obtained by pyro- metallurgical process (Havlik, o.a.,
2010).
The strong oxidation tendency of Aluminum is the reason to ending it in slag when the metallurgical
process of copper is used in recovering metals. In this case recovery of Al is not viable because it
should recovered from Cu before melting by using mechanical separating ways, to prevent losing Al
element with slag as oxides (Diaz & Friedrich, 2015).
Treatment of E-waste by using pyro- metallurgical process can be considered appropriate where
organic constituents are exploited to replace coke that used as fuel and reducing agent (Tuncuk, Yazici,
Akcil, & Deveci., 2012). The energy recovery by incinerating of plastic in a mobile phone to replace
fuel is about 10% and the residue is utilized in metal recovery process (Tangea Lein, 2004).
Degradation of halogens that form a part of plastics in E-waste occurs at high temperature. In this case
the presence of Oxygen causes a high temperature combustion which is a reason of hazardous gaseous
emissions during this process (Havlik, o.a., 2010).
The releasing of valuable metals in Pyro- metallurgical process achieved by smelting in furnace at
high temperature compare with hydrometallurgical process which is done through leaching by using
strong acids, crushing or grinding. (Abdul Khaliq, 2014)
4.2.1 Disadvantages of pyro-metallurgical process • Not easy to recover Iron and Aluminum because they transform to oxides and change to slag phase
(Abdul Khaliq, 2014) (Kantarelis, Evangelopoulos, & Yang, 2015).
19
• Particular mechanisms of isolating hazardous are required to reduce environmental contamination
that take place by emission of hazardous. During smelting of feed materials generate dioxins
(Kantarelis, Evangelopoulos, & Yang, 2015), when halogenated flame retardants in plastics are
burned (Abdul Khaliq, 2014). One tone of shredded mobile phone waste during smelting process
generates approximately 440 kg emission. Organic and plastic matters represent 44% of E- waste
which means high amount of hazardous (Navazo, Méndez, & Peiró., 2013). Therefore not possible
to recover plastic by using pyro- metallurgical process (Abdul Khaliq, 2014).
• Pyro-metallurgical route is applied in large scale for economy point of view because the process
required large facilities such as integrated smelters (Navazo, Méndez, & Peiró., 2013).
• Fine dust of E- waste non- metallic fraction is burning immediately before reaching the metal bath
in blast furnace. To employ energy content and reduce health risk created by fine dust particles,
forming pellets by agglomerating these fractions is necessary (Abdul Khaliq, 2014). Which
influences the total cost.
• The risk of losing PMs (Au, Ag and Pd) from the base metals BMs (Cu, Al, Ni, Sn, Zn,Pb and Fe)
occurs by increasing the volume of slag in furnace that generated by feed material from ceramic
components (Abdul Khaliq, 2014).
• The feedstock (E- waste) are compound and that causes difficulty to manage the process of smelting
and refining (Abdul Khaliq, 2014).
4.2.2 Copper smelting route Solid residue outlet from combinations of pyro- and hydro- metallurgical processes is applied in copper
smelter in order to recover copper cathodes as the main product. Copper smelters are used in Boliden,
Sweden to recover precious metals ((CRI), 2014). E-waste recycling is dominating by copper smelting
route because PMs are collected in copper matte or black copper (Abdul Khaliq, 2014). The recycle and
extract PMs from E-waste occur by utilizing primary and secondary copper smelting routes. Lead
smelting routes is generated toxic gases, which mean copper smelting is more environmentally friendly.
In this case the facilities of copper smelting can put near populations that is enhanced the recycling
economy by reducing the cost of WEEE transportation (Abdul Khaliq, 2014). Recovering of PMs occurs
in this process where they segregated in slims by using conventional electrorefining process (Abdul
Khaliq, 2014). The input of smelting process is copper ore, WEEE and copper scrap ((CRI), 2014)
Primary copper smelting or called sulfur- based route, is utilized to produce 40% of copper matte and
98.5% of blister copper.
20
At the end to produce pure copper using fire refining of blister copper. Secondary copper smelting or
called the black copper route, take place through reduction process form crude copper and used a
converter to refine it by oxidation.
Secondary copper route is important because there used oxidation to remove high levels of impurities
consist of Iron (Fe), Zinc (Zn), and Tenn (Sn). Secondary smelting process contain reduction and
oxidation cycles. The separations of impurities into vapor phase occur to settle them later in the off gas
(Abdul Khaliq, 2014).
4.3 Hydro- metallurgical process Extraction of Au, Ag, Cu, Pb, and Zn from WEEE is done by traditional technologies of
Hydrometallurgical process. Processing of E- waste includes two main stage of extraction by using
leaching, first the base metals are extracted and then valuable metals. Hydrometallurgical process steps
are starting with mechanical pre-treatment in order to granulate the total fraction (Kantarelis,
Evangelopoulos, & Yang, 2015) of E- waste since plastic or ceramic materials cover the metallic
elements in PCBs (Tuncuk, Yazici, Akcil, & Deveci., 2012), leaching of wanted dissolution of metals
by using appropriate filter (Tuncuk, Yazici, Akcil, & Deveci., 2012) (Abdul Khaliq, 2014) to isolate the
interest metal from the solution (Gramatyka, Nowosielski, & Sakiewicz., 2006).
The utilized acid or caustic leaching solvents are mainly HCl, NaOH, H2SO4 and H2O2 or HNO3. In
order to increase the metal yield, a small grain size is required in this process (Gramatyka, Nowosielski,
& Sakiewicz., 2006). Followed by purification through separating the pregnant solution and removing
impurities (Abdul Khaliq, 2014) (Tuncuk, Yazici, Akcil, & Deveci., 2012), where the enrichment of
metal content is a result. Then using the solvent extraction to separate (Abdul Khaliq, 2014), and to
concentrate this metal (Gramatyka, Nowosielski, & Sakiewicz., 2006) followed by adsorption and ion
exchange enrichment process (Abdul Khaliq, 2014).
Extra benefits of hydro- compare with pyro- metallurgical are getting more exact, expectable results,
and easy to control the process, (Abdul Khaliq, 2014) no hazardous gases or dusts that result from
incinerating of E- waste which means less environmental impact, add to that the process is applied in
small scale (small facilities) with low capital cost while leads to high metal recoveries (Tuncuk, Yazici,
Akcil, & Deveci., 2012).
The leaching solvent that used to recover PMs from their primary ores is consisting of halides, cyanides
(CN), thiourea (CH4N2S) and thiosulfates (S2O32- ). Metals dissolution from their primarily ores are
controlled by amount of PH, Temperature, and stirring of the process (Abdul Khaliq, 2014).
21
To recover PMs from E-waste a hydro metallurgical method was suggested by previous study, utilizing
Aqua regia (HNO3 + 3 HCl) as leaching agent with choosing ratio of metals to leachant is 1 / 20. During
the first stage recovered 98% of Silver and 93% of Palladium. To extract gold applied liquid - liquid
extraction method with toluene to recover 97% of gold (Abdul Khaliq, 2014).
4.3.1 Disadvantage of hydrometallurgy • Recovering in all hydrometallurgical methods go slow and thus takes longer time (Abdul
Khaliq, 2014). Relatively high voltage (3 V) is needed which means high electricity is required
(Navazo, Méndez, & Peiró., 2013), that influence the recycling economy (Abdul Khaliq, 2014),
in addition to the overall recycling scheme (Kantarelis, Evangelopoulos, & Yang, 2015).
• To obtain an efficient dissolution, takes longer time to reduce feedstock size by applying
mechanical process on E- waste. (Abdul Khaliq, 2014) Furthermore 20% of precious metals
are lost during this process (Kantarelis, Evangelopoulos, & Yang, 2015).
• The extracting of gold from E- waste need special equipment that made of Al and rubber
because the process is performed by using a Halide leaching. Where strong corrosive acids and
oxidizing conditions are applied, difficult to use ordinary metals. (Abdul Khaliq, 2014)
• High safety standards should take into account when using a hazardous leachant such as
Cyanide. Problems of environment contamination and human health are causing by this
leachant. (Abdul Khaliq, 2014) (Kantarelis, Evangelopoulos, & Yang, 2015).
• The overall recovered metals are susceptible to loss during dissolution and later steps. (Abdul
Khaliq, 2014) and that also influence the process Economist (Kantarelis, Evangelopoulos, &
Yang, 2015).
4.4 Electrochemical treatment At the end utilized electro-refining or chemical reduction process (Abdul Khaliq, 2014). The method is
done in aqueous electrolytes or in molten salts to refine the metal that recovered via hydro-metallurgical
treatment (Gramatyka, Nowosielski, & Sakiewicz., 2006). The small voltage that´s needed in the process
is from 0,2 to 0,3 V (Navazo, Méndez, & Peiró., 2013).
22
5. THERMAL DEGRADATION OF PLASTICS 5.1 The Mechanism of Thermal Degradation of plastics Flammable volatiles are generated through chemical processes while decomposition and variation of
material burning characteristics for instance melting and charring is considered as physical changes (L.
& Hieschler, 2002). Diagram (9) illustrates organics suffer various thermal cracking at high temp.
Figure 9- Thermal decomposition of organic material in differ temperature (Diaz & Friedrich, 2015)
Through the pyrolysis process, mechanism of degradation (thermal cracking) is done by the following
four steps:
I) End-chain scission (depolymerisation): Consider as the main method for plastic pyrolysis
(Diaz & Friedrich, 2015), the split of polymer occurs at the end groups consecutively and
the corresponding monomers are yielding as a result of the breaking up (Buekens & Huang,
1998) (Diaz & Friedrich, 2015). In this step input energy as a result from heat is a reason to
loss hydrogen atom from the polymer chain which cause unstable polymer (Zeus &
technical whitepaper, 2005).
II) Random-chain scission. Fragments of unequal length are formed when the polymer chain is
split up (Buekens & Huang, 1998)(Diaz & Friedrich, 2015) randomly along the chain (Diaz
& Friedrich, 2015).
III) Chain-stripping. Different reactions are involved in this step (Zeus & technical whitepaper,
2005). A Cracking product and charring the polymer are resulted when side group and
reactive substitutes are eliminated from the polymer chain (Buekens & Huang, 1998) (Diaz
& Friedrich, 2015).
IV) Cross-linking. The cross link and polymer embrittlement are a result when two polymer
chain become linked together (Zeus & technical whitepaper, 2005). Increasing the
temperature, a chain network is formed for thermosetting polymers (Buekens & Huang,
1998) (Diaz & Friedrich, 2015).
23
Gaseous fuel vapours that generated by the chemical decomposition of solid material, can burn above
the solid material and cause thermal decomposition. Self- sustaining process can approach when the
production of volatile or gaseous fuel vapour is continued as well as the burning of material is
uninterrupted, in this case a sufficient heat from burning gases feed back to the material is necessary (L.
& Hieschler, 2002).
Flammable volatiles are generated when heat is transferred to the polymer. The reaction between the
oxygen in the air above the polymer and volatiles causes heat generation. The process continues when a
part of generated heat is transferred back to the polymer (L. & Hieschler, 2002). Diagram (10) below is
a schematic sketch illustrated that:
Figure 10- Required feedback energy loop for sustained burning (L. & Hieschler, 2002)
5.2 Gasification Thermal degradation Process of material that takes place in exists of air, oxygen and steam as oxidizing
medium. The purposes of gasification process are: (Richards, 2015)
o An intermediate gas is produced which has many usages.
o Carbon conversion degree is increased during gasification.
To perform stoichiometric combustion (the ideal combustion process where fuel is burned completely)
during gasification process, one important thing is keeping the equivalent ratio at the right level to avoid
excess oxygen in the outgoing gases when producing CO2 and H2O from incoming fuel.
The equivalent ratio is the amount of oxygen supplied in relation to what is needed for a theoretical
combustion (Richards, 2015).
24
To increase the incoming fuel temperature and to prevent the happening of endothermic reactions, the
needed heat is generated by exothermic reaction or supplied externally.
When the material is heated, pyrolysis process occurs first regardless the present of an oxidizing medium
(Richards, 2015).
In case of using polymers as feedstock, basically the original material of solid polymer is volatile. For
easily vaporized smaller molecules are needed and they maintained by breaking down large molecules.
A number of differ chemical species form the smaller molecular fragments with differ equilibrium
vapour pressure for each fragment. The vaporization of lighter molecular fragments are occurred
immediately after their creation, while for some time will stay the heavier molecules in the condensed
phase (solid or liquid). During this time further decomposition of these heavier molecules are taken place
to create lighter fragments.
Virtually the solid residue will not remain when polymers decompose completely. In case when solid
residues are left, not all the original fuel becomes fuel vapour. The solid residue divided into char
(carbonaceous), inorganic or a mixture of the two. The physical properties of original materials and their
chemical composition are the main factors that influence the rate, mechanism, and product composition
of thermal decomposition processes (L. & Hieschler, 2002).
5.2.1 Advantages of gasification
Liquid product (oil) is more suitable for using in Otto engine, gas turbine, and Rankine cycle,
since it produced during second stage which takes place with a low presence of contaminants.
Lower emission levels can be reached.
Applying high temp is the reason to produce less amount of slag.
As a result of the above, minimized the possibility to form toxic substances (such as dioxins and
furans) (Richards, 2015).
25
5.3 Pyrolysis technology Chemical and thermal reaction utilizes to degrading organic materials (Hense, Reh, & Franke, 2015) in
absence of oxygen with ratio of air content in the system to the total stoichiometric combustion require
air 𝜆 is equal to zero (Diaz & Friedrich, 2015). Inert gas for instance nitrogen is used in typical pyrolysis
in order to create a non-oxidative atmosphere (Jasminská, Brestovič, & Čarnogurská, 2013). Pyrolysis
leads to separate valuable metals from plastic matrix as well as produce gaseous and liquid fuel at the
same time (Hense, Reh, & Franke, 2015).
In general Pyrolysis is carried out at temperature range from 250 °C to 1100 °C, and can be classified
into three categories according to the temperature during running the process as follows (Jasminská,
Brestovič, & Čarnogurská, 2013):
1- Low temperature pyrolysis, process temperature is from 250 °C up to 500 °C.
2- Middle temperature pyrolysis, reaction occurs when temperature between 500 °C and 800 °C.
3- High temperature pyrolysis, when reaction temps higher than 800 °C.
The pyrolysis process employs to degrading organic materials in absence of oxygen (Hense, Reh, &
Franke, 2015) at temperature in between 450°C to 750 °C (Tangea Lein, 2004). Applying pyrolysis in
recycling plastics leads to convert solid organic into solid cokes and gaseous components. Condensable
gases will transfer into liquid (oil state) and non- condensable gases are form gaseous components (Diaz
& Friedrich, 2015).
Primary output products of pyrolysis process are char coal, oil and gas. There are three intervals during
pyrolysis process (Jasminská, Brestovič, & Čarnogurská, 2013):
1- Endothermic process at temp up to 200 °C, where water steam is formed while samples materials are
being dried.
2- Dry distillation occurs between 200°C and 500 °C when side chains are split off from high-molecular
organic matters and leads to convert macromolecular structures into liquid and gas organic products
in addition to solid carbon.
3- Temp range of last interval is from 500°C up to 1200 °C to fission and transform the second interval
products and create gas from differ compounds such as H2, H2S, CO, CO2, CH4, C2H4, C3H6 and
other light hydrocarbons in addition to non-condensed organic elements .
At low temperature pyrolysis is endothermic and becomes exothermic at higher temperature. The sum
of the heating value in the original material and the added energy during pyrolysis process represents
the pyrolysis heating value (Lewis, 1967).
According to the desired product, the technology of pyrolysis is divided into slow and fast pyrolysis
(Richards, 2015).
26
5.3.1 Slow pyrolysis: Low heating rate with a long residence time is applied in this process for the solid material in order to
guarantees a mild treatment that causes converting of low amount of material into gas phase. The process
results in a solid char contain a higher amount of oxygen and hydrogen.
Low energy is required when low temperature process at around 500 °C is applied, as well as during gas
de-volatilization, less violent reaction than in high temperature process.
The gas phase contains fewer amounts of tars when applying the process at higher temperature above
700 °C as well outcome char is more rich carbon.
Both the low- and high-temperature processes start with pyrolysis as first stage. First the separating of
solid residue occurs directly after pyrolysis and then treating of solid takes place separately from other
products. While in the later continue applying higher regular temperature on the solid that also separated
from gas phase to guarantee the complete melting.
Rotary furnace is suitable to carry out the slow pyrolysis and in case of utilizing a tube furnace, an
external force is necessary for better transportation (Richards, 2015).
5.3.2 Fast pyrolysis: Fast pyrolysis is applied at 510°C in order to obtain the highest liquid yield, thereafter the yield is
decreased by lifting up the temp.
Actually there are no large-scale workshops that employed in order to focus on producing oil pyrolysis.
In this case only slow pyrolysis is working at this time (Richards, 2015).
5.3.3 Pyrolysis Factors: Pyrolysis outcome composition of the solid, liquid, and gas products and final yield, (Kantarelis,
Evangelopoulos, & Yang, 2015)(Lewis, 1967) as well as amount of emission, are influenced by number
of variables (Hense, Reh, & Franke, 2015).
Chemical composition of material (Lewis, 1967) the composition of raw materials as well
thermal decomposition of polymer influence the outcome from pyrolysis process (Kantarelis,
Evangelopoulos, & Yang, 2015).
Pyrolysis temperature and heating rate (Lewis, 1967) Formation of smaller molecules
frequently take place at higher- heating rates and –temperatures (Kantarelis, Evangelopoulos, &
Yang, 2015).
27
Residence time Gas yields, coke, and tar formation are increased during secondary reaction
at longer residence time.
Reactor type Type of reactor has major role in setting the rate of heat and mass transfer as
well the residence time of the products.
Pressure less coke and heavy ends formation are created at lower pressure as a result of
reducing the condensation reactions between the reactive vapours (Kantarelis, Evangelopoulos,
& Yang, 2015).
5.3.4 Advantage of pyrolysis
The process has a max thermal efficiency, That related to combustion of fuel gases is done in a
separated chamber from the E-waste, which result in a complete combustion at high temp and
low excess oxygen (Lewis, 1967)
The three products of the process are: Solid residue includes concentrated metals, liquid tar and
volatile metal compounds are stayed in the gaseous fraction. (Havlik, o.a., 2010) I.e. thermal
treatment of E waste leads to reduce the mass and volume of WEEE and hence reduce landfill
space, and the environmental load will be decreased by demolition the organic contaminants
and saving resources (Richards, 2015).
Figure 11- Closing the loop by recovering energy and metals through pyrolysis process (Evangelopoulos, Efthymios, & Yang, 2015)
Pyrolysis is a promising method to recover the critical metals that are not recovered yet such as
gallium (Ga), germanium (Ge) and tantalum (Ta) in addition to that, the pyrolysis is used to
generate energy through producing high calorific gases and liquids (Hense, Reh, & Franke,
2015).
28
Another advantage of pyrolysis is the liquid products can be utilized for chemical or power
industry (Abdul Khaliq, 2014). In other words, enable an energetic utilization of organic
materials (Hense, Reh, & Franke, 2015)
During this thermo-chemical process contained metals are not oxidized due to the inert
atmosphere (Hense, Reh, & Franke, 2015). I.e. they stay in their original form where they were
in E-waste. (Havlik, o.a., 2010)
Since the two phases (liquid oil & gaseous output) have homogeneous composition, the thermal
energy that formed by these phases is performed easily and in better environmental conditions
compare with direct incineration by using e.g. a blast furnace (Tangea Lein, 2004).
Lower potential for air pollution compared with traditional methods of thermal processing
(Lewis, 1967).
During pyrolysis process lower unsaturated hydrocarbons are created while the higher saturated
hydrocarbons are cleaved. (Havlik, o.a., 2010)
Pyrolysis process does not produce slag (Evangelopoulos, Efthymios, & Yang, 2015), while
using traditional method (smelter) resilts 396 kg of slag from treatment 1 tonne of mobile phones
(Navazo, Méndez, & Peiró., 2013).
Laboratory research shows that a problem of incomplete combustion is occurred in case of
applying thermal treatment in presence of oxygen (Havlik, o.a., 2010).
Pyrolysis is promising method to recover material and energy from polymer scrap, since the
energy needed to convert plastic waste into valuable hydrocarbon products is estimated by about
10% of available energy in the waste plastic (Bhaskar, 2004).
The need for pre-treatment of liquid product is reduced by using pyrolysis process before
combustion as well as increasing the opportunity to separate solid residue for instance refining
more iron and aluminium before the combustion at high temperature (Richards, 2015).
Pyrolysis is used as a pre-processing method to separate two different fractions e.g metallic and
non-metallic in case of PCB. (Diaz & Friedrich, 2015)
29
5.3.5 Pyrolysis technology and reactors Different types of technologies and reactors are employed to perform pyrolysis process relying upon the
required output (Richards, 2015). Due to the difference of heat and mass transfer with time, the residence
time of the products is altered according to the type of utilized reactor (Kantarelis, Evangelopoulos, &
Yang, 2015). Depending on the method of operating, these reactors divided into:
Fixed bed, fluidized bed, or entrained flow. A high quality syngas is produced by using the entrained
flow type but the operation is done in large scale (i.e. not laboratory scale) and the pre-treatment needs
to be in high level (Richards, 2015).
5.3.5.1 Fixed bed gasification The direction of gas flow inside the fixed bed reactor is the reason to divide operation systems into
updraft or downdraft. In both type of gasifier the feedstock is added from the top.
Downdraft when the flow of gas is in same direction to the solid material. Higher quality gases are
produced as well as the damage of gas turbine is avoided by utilizing this type which is easy to clean,
while the complex design and more control are required. The opposite direction is used for updraft kind
which produces gases with high amount of tars since the reactor is suitable for treating different qualities
of feedstock. In general advantages of updraft gasifier are considered as a high energy efficiency unit
and the produced gases are cleaned first then cooled.
The difficulty of controlling gases outcome from large diameter reactor is the reason of using this type
of reactor to produce small amount of products (Richards, 2015).
5.3.5.2 Fluidized Bed (FBR) (Richards, 2015) Fast and efficient heat and mass transfer inside the reactor is the reason to distribute the fuel and raises
mixing in this type of reactors.Utilized bed material is formed from sand in small particles that needed
to add in FBR as well as the largest dimension of used west (feedstock) is around 5 cm. i.e. The feedstock
should prepare before the adding.
Two types of fluidized bed gasifiers are representing by either circulating (CFB) or bubbling (BFB)
fluidized bed according to the velocity of gas flow.
Certain minimum amounts of fluidizing medium such as air, steam, or oxygen are needed to apply during
fluidization. Sand with smaller size around 0.25 mm is used in case of bubbling (BFB) than in circulating
fluidized bed (CFB). Smaller sands particles are easier entrained and the gas flow will be more uniform
and not being channeled.
30
The effect of gas flow is the reason that, the size of the sand partials are reduced by attrition and thus
part of the bed material (sand) is easily entrained together with the fly ashes. The most of sands is
removed later in a cyclone after gasifier, however the remained sand cause increasing amount of
produced landfill in addition to more treating of the ash is needed.
Bubbling gasifier works with high velocity about 5 to 6 m/s, which leads to uniform distribution of
temperature among different phases, good mixing in the free board area and most of the sand particles
are entrained by the effect of high flow gases.
The technology of FBR that´s utilized at this time is employed gas flow velocity between 1 m/s and 3
m/s in keeping particles diameter around 1mm. This operation will keep sands particle close to the bed
and hence reduce the amount of sand that need to be taken away in the cyclone. The important thing by
applying this idea is an efficient mixing is obtained.
The efficiency of fluidization is reduced when growing in size of sand particles are occurs by running
the process around melting temp of inorganic material of feedstock which causes agglomeration.
Important factors that influence this process from efficiency and economical perspectives are quality of
feedstock (west) and amount of west that takes part in operation (Richards, 2015).
5.3.6 Degradation levels According to previous study the pyrolysis behaviour of Tetrabromobisphenol A (TBBPA) as brominated
flame retardant containing paper phenol Resin laminated PWB was investigated. Experiment
degradation was performed in temp range between 50°C and 800°C by using Thermal gravimetric
analyses (TGA). The samples were found degraded through three following levels. (Hense, Reh, &
Franke, 2015)
1- The first level was in temp range between 272 °C and 280 °C, lead to decompose of cellulose
and thus evaporate H2O & CO2.
2- The second level was occurred in temp from 270°C to 370°C, in this level Br- products was
formed when the contained fire retardants degraded.
3- At temp 370°C started the third level then char was formed from decomposition of phenol resins.
At temp range between 270°C and 400°C was happened the generation of brominated aromatic
compounds. While temp above 400°C forming HBr from Br-products.
When Temp equal to 450°C generated phenol products with low concentration of Br.
31
The conclusion was that HBr is the main product of pyrolysis when temp equivalent to 450 °C. The
characteristic of HBr is easily separable in a water trap; as well as the generation of PBDD/F could take
place by just a small yield of brominated aromatic compounds. (Hense, Reh, & Franke, 2015) The
following reactions that take place through pyrolysis process to form various compounds of MexXy-Brz
depending on the temp during thermal treatment of WEEE are forming an important aspect around
pyrolysis. (Hense, Reh, & Franke, 2015)
I- Br- stabilization reaction is the reason to vaporize metals as Mex-Xy-Brz compounds, which
is means metal become enriched in liquid/gaseous phase of pyrolysis outcome. That
influences the yield of gas, liquid and solid outcome, in addition change the degradation
levels which explained earlier and thus affect Br containing products.
II- Existence of metals and metals oxides (Me & MeO) affect the production of brominated
compounds which work as precursors for generation of PBDD/F.
In applying the process , important to go beyond heating temp between 260°C and 430°C and cooling
temp from 450°C to 250°C as fast as possible to avoid formation of toxic substances (Dibenzo-p-dioxins
and furans (PCDD/F) and PBDD/F).
The total yield of PCDD/F and PBDD/F can be decreased by applying pyrolysis process at a temperature
above 850 °C. The high molecular weights and low vapour pressure of PCDD/F and PBDD/F is a reason
to find a small amount of these toxics substances in flue gas, while solid residues (char) is soaked up
these components. (Hense, Reh, & Franke, 2015)
5.3.7 Dehalogenation Dehalogenation is needed to apply on liquid products of Pyrolysis which commercially unusable because
they contain a mixed of halogenated waste plastics (Vasile & etal, 2006). Thus maximum yield of the
process is achieved when the halogens are released from liquid oil (Kantarelis, Evangelopoulos, & Yang,
2015).
The thermo- chemical treatment of WEEE are faced a problem of existence amount of halogens in
pyrolysis liquid products, the high yields of halogens prevent energetic utilization of these products. In
this case reducing the amount of halogens are important to get the maximum yield of the pyrolysis
process (Hense, Reh, & Franke, 2015) that can achieved only when the liquid product can be used for
fueling recycling plant or is marketable (Kantarelis, Evangelopoulos, & Yang, 2015), as well as to reduce
emission of toxic substances (Hense, Reh, & Franke, 2015). Dehalogenation of the liquid phase can be
done through different routes, either during, or after the pyrolysis process (Kantarelis, Evangelopoulos,
& Yang, 2015).
32
Few methods and techniques that followed in dehalogenation of liquid phase are classified as below
(Hense, Reh, & Franke, 2015):
5.3.7.1 Pyromaat (two stage process) This developed process was combined pyrolysis and gasification to recover Br and Cl from WEEE. At
550°C WEEE is pyrolysis for 15 minutes as the first stage. Pyro-metallurgical process was used to
recover metals from the solid residue product, while used the second stage for treating uncondensed gas
fraction at 1230 °C through a high temperature gasifier.
The last stage was important to crack tars and to produce a syngas. The cleaning of syngas was done by
using Sodium hydroxide (NaOH) filters downstream reactor to remove and recover halogens as NaBr /
NaCl. Neutralization agent Ammonia (NH3) was injected in a combustion chamber to refine the syngas
from the remaining halogenated compounds (Hense, Reh, & Franke, 2015).
5.3.7.2 Two stages pyrolysis Thermal degradation take place in different levels related to the composition of the WEEE and the use
of additives. The degradation of thermoplastics takes place at higher temp than the dehydrohalogenation,
that was investigated by previous study. Corresponding to these two degradation stages, it was possible
to separate pyrolysis products in fractions, one containing halogens while another fraction is halogen
free. The two-stage processes are used to decrease the amount of halogens, mainly in the pyrolysis oil
(Hense, Reh, & Franke, 2015).
The two stages were done under nitrogen atmosphere. The first stage pyrolysis was worked at 350 °C
and the second stag operated at 450 °C and each process took about two hours. (Hense, Reh, & Franke,
2015). Chlorine (Cl) could be released with the lower temp stage as Hydrochloric acid (HCl), while
needed synergistic Antimony oxide (Sb2O3) to release Br (Kantarelis, Evangelopoulos, & Yang, 2015).
The solid residues resulted from this two stags process was with the lowest yields of PBDD/F. While
where HBr was produced, polypropylene-reactor was used later to refine oil product from halogens.
The same process was done with differ Ca- based additives by using TGA. Decomposition of PVC
samples were examined in two stages, first one took place between 280 and 400 °C with a maximum at
320 °C, while the other one operated between 400 and 560 °C with a maximum at 482 °C.
The results showed that HCl was released through the first stage, and the second one used to get rid of
hydrocarbons. It was observed that the yield of CaCl2 increased by adding Calicium (Ca) – based
additives, while decreased the yield of HCl. (Hense, Reh, & Franke, 2015)
33
6. EXPERIMENT INVESTIGATION 6.1 Experimental Methodology for PCB s pyrolysis At Royal’s Institute of Technology (KTH) - Department of Energy and Furnace Technology-
laboratories in Stockholm, Sweden, was the place where the experiments took place.
A Stainless steel fixed bed batch reactor is employed in lab-scale pyrolysis process. The reactor length
is 100 cm, inner diameter D=2, 54 cm.
Two types of materials were used in these experiments, main body and sockets of Printed Circuit Board.
The typical pyrolysis (using N2) was run for 10 g (PSB- mb) and for 5 g (PCB- sockets), while the novel
pyrolysis (using steam) was run for 7 g (PCB- mb) and for 5 g (PCB- sockets). The particles size of
WEEE some used in all experiment of PCB- mb and sockets are > 0.71mm.
6.2 Characteristics of the pyrolysed WEEE sample The selected samples of WEEE were PCB- main body and PCB- sockets. The prepared samples were
provided by KTH. The elemental composition of using samples are showed through table (2). The
analysis and composition of both samples were determine out of KTH by Belab AB company. The
Samples were prepared according to the following process.
6.3 Sample preparation Samples are already prepared in the laboratory of KTH as in followed steps (Evangelopoulos, 2015):
1- Clean the sample from dust.
2- Remove hazardous components from PCBs (batteries, external PCI cards, and capacitors).
3- Remove the plastic sockets from the surface of PCBs, to be studied separately as varies fraction.
4- Shred and crash the fractions separately to minimize the size as well as to increase the
homogenization of components which leads to minimize the heat that needed to start the
reaction.
34
6.4 Components and Elemental Analysis of Printed Circuit Board Samples: Table 2- Proximate composition analysis of printed circuit boards both samples
proximate analysis Ultimate analysis
PCB
mb
PCB
sockets
PCB
mb
PCB
sockets
Moisture 105 °C 0,20 % 0,60 % Carbon (C) 18,90% 43,10%
Ash 550 °C 68,41% 32,90% Hydrogen (H) 1,90 % 4,60 %
Volatile 20,15% 63,30% Nitrogen (N) 0,57 % 3,14 %
Fixed Carbon 11,43% 3,8 % Chlorine (Cl) 0,09 % 0,08 %
Sulphur (S) 0,06 % 0,73 %
Bromine (Br) 3,91 % 0,56 %
Oxygen (O) 5,96 % 15,50%
Elemental Analysis
PCB
mb
PCB
sockets
PCB
mb
PCB
sockets
Element Symbol ppm Element Symbol ppm
Gold Au 6,61 <0,5 Barium Ba 1645 691
Palladium Pd 11,6 <0,5 Lead Pb 49611 1070
Platinum Pt 0,0101 <0,5 Boron B 2470 2030
Silicon Si 101855 58200 Cadmium Cd 0,23 39,4
Aluminium Al 25700 15100 Cobalt Co 3,23 5,04
Calcium Ca 34000 29900 Copper Cu 338690 15700
Iron Fe 10300 4030 Chromium Cr 237 920
Potassium K 300 492 Mercury Hg 3,65 0,0553
Magnesium Mg 530 5790 Molybdenum Mo 0,187 0,137
Manganese Mn 78 105 Nickel Ni 1340 1060
Sodium Na 852 809 Tin Sn 1530 695
Phosphorus P 99,5 290 Vanadium V 14,8 21,3
Titanium Ti 1372 1460 Zinc Zn 9410 9790
Antimony Sb 40,8 24600 Silver Ag 398 0,682
Arsenic As 0,264 22,8
Table (2) above shows an analysis of the two samples that have got by Belab Ab Company. It is clear
that Carbon, Hydrogen, Bromine and Oxygen are the most important fraction in the PCBs. Silicon,
Aluminium, Calcium, Iron, Nickel, Lead and Copper with many other elements is found in different
proportions, hence high amount of metals leads to form high percentage of ash through heat treatment
of main body. It is clear from the above table that metallic fraction is very heterogeneous material[ (Diaz
& Friedrich, 2015)
In case of using PCBs sockets, high diversity of plastic fractions with flame retardants lead to high
volatile that caused by burning of the plastic fractions. Thermal-degradation happened of organic with
absence of oxygen during Typical Pyrolysis process and leads to make more than 60% volatile.
35
High amount of low molecular weight products result from decomposition of these subjects to form
liquid oil and gases. About 33 % ash or solid residue (inorganic components) can be recycled to recover
metals while the rest soot (fixed carbon) approximately 3 % throwing in landfill (Jasminská, Brestovič,
& Čarnogurská, 2013).
6.5 Experimental facility At laboratory of Division of Energy and Furnace Technology located on the Campus of Royal Institute
of Technology in Stockholm, the experiments were performed by using lab – scale facility as shown in
diagram (12) below. This unit was used to experiment different types of materials. The utilized reactor
was vertical semi-batch type cylinder reactor.
Figure 12- An image of experiment facility
Individual elements of the experiment facility illustrate in the diagram (13) in the next page
are:” 1 – nitrogen supply, 2 – gas regulator, 3 – flow meter, 4 – three way valve, 5 – reactor
(length L=100 cm, inner diameter D=2,33 cm), 6 – sample and mesh support, 7 – electrical
heater (power output P=1 kW), 8 – insulation, 9 – tar measurement vessels, 10 – cooling system,
11 – gas measuring vessels, 12 – exhaust gases output (in case of steam pyrolysis), 13 – heater
controller, 14 – analog-to-digital converter, 15 – data recording, T1, T2 – thermocouples Ktype,
I – pyrolysis line with N2, II – pyrolysis line with steam” (Wojkiewicz, 2015).
36
Figure 13- Sketch of laboratory pyrolysis facility
Red hidden line surrounded a source of nitrogen and used green hidden line around steam source.
High temperature and corrosive resistant three-way valve was used to switch between the two
gases or to lock the system at the end of experiment.
Reactor tube was threaded in both ends and made of heat resistant steel in dimension of 1000 mm
length and 25 mm inner diameter.
Two thermocouples K-type were used; one attached with solid sample inside the reactor, and the
other was placed to measure the temperature of the electric heater, (the region that surrounded the
sample). In order to convert the physical parameters into digital values, the ends of thermocouples
were connected to the analog-to-digital converter (A/D). The A/D was connected to the PC where
data was being collected.
Triple circle shape mesh with appropriate diameter about 30 mm were used, The mesh is working
as stand for the sample and preventing it from leaving the initial position before reaching the
specified temperature of the process. Since a vertical reactor was utilized in the experiment, fine
grid put in between two coarser grids to avoid falling down parts from the sample before starting
the process.
An electrical heater (7) with power output P=1 kW, (connected with electricity socket), was used
to supply thermal energy that needed for a thermal decomposition.
About 25 cm of lower part of the reactor is covered by an insolation (8) to prevent heat loss as
shown in diagram (14) in the next page.
37
Figure 14- Vertical semi-batch type cylinder reactor covered by electrical heater utilized in experiments
6.6 The Procedure of Typical Pyrolysis The facility should prepare before experiment to get high accurate results. Acetone (C3H6O) was
used to clean the reactor´s tube. Stuck oil drops that accumulated on the inner wall of the reactor
from previous experiments were removed.
Weight the prepared samples before the running of each experiment by using the high precision
balance scale of an accuracy of 0.0001 g, diagram (15) below.
Figure 15- Image of Balance scale that used for samples and tar measurement vessels (Wojkiewicz,
2015)
38
Prepared tar collection equipment (9), Tar measurement group was consist of two gas washing
bottles and two pipe line with connectors set ( plastic- and metallic –pipe with connectors) as shown
in the diagram (16) below. Preparation included washing carefully the pieces of tar measurement
group with deionized water and acetone, then dry the parts well, weight the parts separately by using
a high precision balance scale, and record the results.
Set vessels in the cooling system (10). The third bottle was filled with water so as to catch the tar as
well as to remove inclusions which exist in the gas mixture. Pipe lines was Connected tightly with
each other and with the end of reactor.
An additional load was used to keep tar measurement vessels immersed in cooling system. Water
cooled system was used in cooling the produced gases. For the purpose of condensing all produced
gases that condensable, cooling system water should kept below 10oC.
Figure 16-Image of tar collection equipment (Wojkiewicz, 2015)
Place the mesh inside the reactor tube in a place equivalent to reactor centre (6). Set the tube inside
the electrical heater and then add the sample. Reactor unit is connected to two thermometer type K
(T1/T2) in order to measure accurately the change in temperature of the sample and reactor as a
function of time.
The Nitrogen was opened, increased Nitrogen flowrate gradually about 10 ml/min every 5 minutes
to avoid changing the position of the mesh support, and then waited 30 minutes until removed all
Oxygen and created an inert atmosphere inside the system.
A measurement was taken by using micro - GC to check if there was any Oxygen remained in the
system.
The unit was started to control nitrogen flowrate (3). Nitrogen flowrate that used in experiment was
50 ml/min.
Between cooling unit and the micro- GC, was put a bottle half filled with an aqueous Sodium
hydroxide (NaOH) in order to capture flame retardants elements hydrogen bromide (HBr) and
hydrogen chloride (HCl).
Collecting
flask
Drechsel
Bottle Head
Connectors
39
Seal the reactor tightly from both ends and place insulation (8) around the bottom of the reactor (5)
to prevent heat leaking.
Run a high temperature and corrosive resistant three-way valve (4) in direction of Nitrogen and let
the Nitrogen pass through the facility about 10 minutes for eliminating atmospheric air that entered
the system after locating the sample into the reactor chamber.
In case of typical pyrolysis, Nitrogen would be dilute with syngas; no gas collection equipment was
used. All gases pass directly through micro- GC analyser and later to the atmosphere.
After sampling Tar washing bottle should be dried from the moisture by using a paper to get accurate
weight of liquid product.
6.7 The procedure of steam pyrolysis The steam pyrolysis experiments were carried out using the same facility that described in above.
But in this case an extra boiler was used in the bottom of lab to produce steam at 140 oC. This steam
would go inside the reactor with the same temp.
The same previous way was used in preparing the two samples.
There is no an apartment to measure steam flow rate. In this case the flow of steam will condense
first and gathered every five minutes to measure the amount of steam flow rate per minute. The
experiment was started when the steam flow rate was stable; an average of last three measurements
was considered as steam flowrate.
Steam flowrate that was used in experiment was 9.25 ml/min.
Before starting the heating process, nitrogen was used for two minutes to remove all oxygen from
the system, then turned the three way- valve to stop flowing of Nitrogen and steam flow was opened.
In case of using steam, higher amount of condensable liquid was expected. So tar measurement
group was consist of two gas washing bottles with accessories and the first bottle was the larger one.
The same way of Preparation as in typical pyrolysis was followed here, two pieces of tar
measurement group were washed carefully while the third one was filled with water. Weight parts
separately by using a high precision balance scale while for first bottle was used a weight scale
diagram (17) in the next page, and the results were written down.
40
Figure 17- Weight scale used for tar measurement vessel in steam pyrolysis (weight scale, u.d.)
No dilution of gases in case of steam pyrolysis, output gases from the process were accumulated in
gas measuring vessels.. To calculate volume of these gases, the vessels were filled with water and
connected by using plastic tubes to other buckets as shown in diagram (18) below. The water in gas
vessels was being replaced by syngas. Weight of the water that go out and replaced by gas was
measured and hence measure the volume of syngas.
Figure 18- Gas measuring vessels connected to other buckets
After finishing experiments steam was switched off and the three ways valve turned in direction of
nitrogen for ten minutes. This route was used to fill the reactor with an inert gas that not react with material
of samples (a kind of flow should be always inside the reactor) in addition to cool down the reactor that
had high temp at that time of experiment.
Micro GC analyzer (Agilent 490 micro GC quad) connected with a computer diagram (19) in
the next page, was used at the end of experiment to analysis the composition of syngas. The
micro GC consists of four columns and thermal conductivity detectors with a silky tube of around
12- 14 meter length was used in this type of analysis. Gases H2 , He, O2 , N2 , CH4 , CO, CO2 ,
H2 S and hydrocarbons up to C6 can be detected by thermal conductivity detectors (Kantarelis
E. , 2014).
41
Figure 19- Agilent 490 micro- GC (micro- GC analyzer, u.d.)
6.8 The procedure of Measurement A time when temperature of sample reach 100 °C was considered a process starting time. Process of
data registration was started at that moment. This temperature was selected to be sure no water in
the system.
Table (3) illustrates actual time needed for reactor, PCBs- mb and PCBs- sockets samples to
approach 600 °C during both of typical and novel -process.
Table 3- Required time to approach elevated temp in both pyrolysis
Pyrolysis Type
Time (min) to reach
600 °C
PCBs mb
Time (min) to reach
600 °C
PCBs sockets
Typical pyrolysis
reactor 13,5 13
samples 15 14
Steam pyrolysis
reactor 18,5 15,5
Samples 21 35
Residence time for samples at 600 °C was 75 seconds.
In concerning with steam pyrolysis, difficult to calculate accurately the residence time for both
samples because samples temp was increased rapidly when reactor´s temp approched 600 °C. The
42
Diagram (20) below shows the differing in temp of the samples as a function of time inside the
reactor during operation processes.
Figure 20- Schematic drawing shows increasing temp of samples according to time
In case of steam pyrolysis, the volume of produced syngas was getting by weighting the water in the
buckets.
Used nitrogen for a while, in order to get rid of all oxygen that was inside reactor in the beginning
of experiment. Then start heating, nitrogen went out to atmosphere.
In case of steam pyrolysis, was changed to N2 after 47 minutes. Thereafter continue ten minutes
with nitrogen to be sure that all gases were removed from the furnace and connections.
Waiting until cooling the system completely before sampling the products.
An another GC apparatus has been put in the lab diagram (21) below, CTC Analytics auto-sampler
was used to inject separately the produced liquids from the four experiments in the GC-FID/MS
analyzer which was provided with DB 1701 (60 m x 0,25 mm) column. (Wojkiewicz, 2015).
Figure 21- The GC-FID/MS analyzer used for liquid analysis (Wojkiewicz, 2015)
0
100 200
300
400
500
600
700
0 10 20 30 40 50 60
TIME/ MIN
SAMPLES TEMP CHANGED WITH TIME IN
THE TWO PROCESSES
PCBs mb/N2 PCBs sockets/N2 PCB mb/steam PCB sockets/steam
43
Before sampling the oils, gas washing bottle should be dried from the moisture by using a paper to
get accurate weight of liquid products. Filtering liquid sample is done before analysis to remove
unwanted large particles that influence the result by connects a syringe with special filter of
permeability 0.45um.
Liquidious phase is diluted with water in case of using steam pyrolysis while for using GC-FID/MS
analyzer not allowed to have water, therefore Liquid sample is prepared to analysis by using
methanol (CH4O) and dichloromethane (CH2Cl2) in differ concentration according to the samples
type and process agent as in table (4):
Table 4- Different agents used to prepare liquid samples before GC-FID/MS analyzer
Experiment Sample CH4O
Typical
Pyrolysis
Sample CH2Cl2 steam
pyrolysis
PCBs mb 0,1 mlg 10 mlg 30 mlg 10 mlg
PCBs sockets 0,1 mlg 10 mlg 40 mlg 10 mlg
Small containers are filled with prepared liquid samples that produced from the four experiments
after filtering to be analyzed in GC-FID/MS analyzer.
In case of steam pyrolysis, liquid product left few days in order to stagnate the mixture and filtering
process became more active. By using the analyzer the whole process is done automatically and it
takes about 50 minutes to get analyzing result of each experiment.
The products solid and liquid yields were weighing their amount separately, while the gas yield was
determined by micro- GC analyser.
6.9 Dichloromethane CH2Cl2 As mentioned before, liquid oil that resulted from steam pyrolysis was diluted with water and GC-
analyzer not allowed to be used with water. In this case, liquid product was keeping few days in bottles
in order to precipitate water in the bottom. Oil has higher solubility in dichloromethane than in water,
so was used liquid – liquid extraction with dichloromethane (Chemistry\\ord, 2014) as solvent to
separate produced oil. The concentrations of solvent were added as in table (4) above.
44
Dichloromethane with the formula CH2Cl2 is colorless, an organic volatile liquid, immiscible with water
and has low boiling point (wikipedia, 2016), Most organic compounds are much more soluble in organic
solvents than in water (Madnel set, 2011).
Prepared of liquid samples was done by taking amount of liquid oil through a small syringe and put it in
separating funnel diagram (22) then add dichloromethane. Shake funnel for a moment to blend the
mixture well, oil will dissolve in dichloromethane then let the compound settle. The same steps were
followed for the four experiments, but methane with a formula CH4O was used to prepare liquids
outcome from pyrolysis the two fractions of PCBs by using typical process. The organic phase and
aqueous phase form layers in the separatory funnel. Most organic solvents are less dense than water but
dichloromethane has higher density than water so they will be the lower layer in sep funnel. At the end
a separating funnel is used to separate organic layer from water, oil is remained when the
solvent is evaporated (Madnel set, 2011).
Figure 22- A separatory funnel (Madnel set, 2011)
6.10 Data collection The remaining solid mass were weighting after each experiment to evaluate the mass data as a function
of time. A stopwatch was used to measure the run time of each experiment. The gas composition along the time was recorded during operation of nitrogen pyrolysis by using
simultaneous micro-GC analysis at the reactor outlet, while in case of steam pyrolysis, collected gases
(in the gas washing bottles) detected by the micro-GC after experiments. Results of the first gas
measurement vessel that was shown through Micro- GC were:
1- Some Nitrogen was existed that related to Nitrogen was in the reactor when the experiment was
began before steam flowed out in the system.
45
2- A little bit of Oxygen because even the bottles were filled with water there were still some
oxygen in addition to the oxygen in the connection between the bottles and Micro- GC analyzer.
The sampling of tar was performed by using 100 ml syringe. A laboratory located in the Campus of
KTH- matrial department, was utilized to curry out the analysis of liquid fraction.
Table (5) below illustrates the collected data that utilized in the four experiments.
Table 5- Experimental conditions for the two types of pyrolysis
Process data Typical Pyrolysis Novel pyrolysis
Temperature 600 °C 600 °C
Oxidizing agent N2 Steam
Flowrate of gases 50 ml/min 9,25 ml/min
Mass of PCB mb sample 10 g 7,3556 g
Mass of PCB sockets sample 5 g 5 g
Time residue 75 sec 75 sec
Heating rate °C/min 32 24
46
7. RESULTS & DISCUSSION In this part influence of using steam in pyrolysis process alongside with applying nitrogen gas was
analyzed. High ash content in PCBs- mb (80 %), was the reason that the samples were transformed to
(75.20, 82.43 wt. %) solid, (19.99, 12.97 wt. %) liquid, and (1.50, 1.24 wt. %) gas products respectively.
High amount of solids residue were remained as shown in diagram (23).
Figure 23- Results of Pyrolysed PCB mb by N2 and steam
Different proportions of solid, liquid and gas were produced in case of pyrolysis the sockets of PCB by
employing nitrogen or steam. The samples were converted into (39.70, 34.59 wt.%) solid, (31.94, 36.60
wt. %) oil, and (3.17, 3.02 wt. %) gas respectively.
It is clear in diagram (24) below that producing of liquid and gas were doubled than in case of pyrolysis
the main body of PCB. That referred to the plastic as the main material of sockets which contains volitile
components (> 60%) of total weight, was converted into solid cokes and gaseous components,then the
condensible part was transformed into liquid and uncondensable gases are formed gaseous components.
Figure 24- Products of treating PCB sockets by N2 & steam pyrolysis
0 10 20 30 40 50 60 70 80 90
solid %
liquid %
gas %
Copmarsion of output of PCB mb from N2 & steam - pyrolysis
PCB mb/steam PCB mb/N2
,00% 0 5 ,00% 10 ,00% 15 ,00% 20 ,00% ,00% 25 30 ,00% 35 ,00% ,00% 40 45 ,00%
Solid residue
Oil
Gas
Comparsion of results of PCB sockets from N2 & steam - pyrolysis
PCB sockets 600°C steam PCB sockets 600°C N2
47
7.1 Mass loss (solid residue) The comparison between mass loss in case of employing steam- or typical -pyrolysis at 600 °C is done
in this section. The convergent residence time was tried to apply in the four experiments to get perfect
results. In both cases the solid residue is dry and not need an extra step. The obtained results are
illustrated in the table (6):
Table 6- The difference in mass loss percentage of solid residue at 600 °C
It is clear from table (6) above, that in case of PCB mb, percentage of mass loss per g of sample that was
got by using steam was (1,2926g) which was less compare with (2,5023g) in case of typical process, i.e.
large mass of solid was residual after steam pyrolysis then that from typical process. That´s related to
the high temp of system was the reason to start melting few elements which have lower melting temp
and lead to form oxides. It´s known that oxides are heavier than their pure metals which causes heavier
solid residual.
In case that the previous opinion was not correct; According to the results of mass loss, through nitrogen
process the increasing in weight of sample by 40% was faced by lossing double amount of mass. That
means using large amount of feedstock lead to more decomposition which is more beneficial in
economical and environmental point of view. Which process is more profitable can be decided when
the solid residues of both processes are analysed.
In the other hand almost the convergent proportions of mass loss were got in case of pyrolys the sockets
of PCBs by applying both processes. That mean´s almost the same reactions took place for solid part of
PCBs- sockets reagardless oxidising agent.
7.2 Analysis of process outcome gases The detected gases by the micro- GC analyzer are: O2, CO, CO2, CH4, N2, and H2 in addition to
hydrocarbons C2H2, C2H4, and C2H6. The analyzer would not work if water attendant with incoming
gases. A filter filled up with Phosphorus pentoxide (P4O10) as dehydrating agent was connected in
between micro- GC and produced gases to absorb water that accompanying gases.
48
In other hand a half filled bottle with sodium hydroxide NaOH was used to capture flame restarted
elements Br & Cl that escort with outcome gases before Micro GC.
Diagram (25) below illustrates a comparison for the produced gases from the four experiments, it is clear
that higher mass of output gases was created by treating the sockets of PCB by both N2 & steam
pyrolysis. While through nitrogen pyrolysis for the PCB mb was resultet the lowest mass of gases.
Figure 25- Amount of outcome gases is different according to sample & experiment type
7.2.1 Composition of outcome gases According to the diagram (26) below, it is clear that differ mass of gases are resulted by treating mb of
PCB according to process type. Both pyrolysis are favorable in producing carbon dioxide (CO2). While
higher amount of carbon monoxide (CO), Methane (CH4), Ethane (C2H6) and Acetylene (C2H2) were
resulted from nitrogen pyrolysis. Almost the same amount of hydrogen was created by the two processes.
Figure 26- Comparison of gases produced by pyrolysis PCB - mb using N2 & steal
-0,02
0
0,02
0,04
0,06
H2 CH4 CO CO2 C2H4 C2H6 C2H2
Experiments outcome gases
PCB sockets 600°C steam
PCB sockets 600°C N2
0,00% 20,00% 40,00% 60,00% 80,00%
H2
CH4
CO
CO2
C2H4
C2H6
C2H2
Analysis of resulted gases from all
experiments
PCB sockets 600°C Steam PCB sockets 600°C N2
PCB mb 600°C Steam PCB mb 600°C N2
49
In case of pyrolysis the sockets of PCB higher total mass of gases were produced (almost the double)
compared with the outcome mass of gases that created from treating PCB mb as shown in diagram (27)
below. Carbon dioxide was also dominated in state of experiment the sockets, the same previous
situation is working for CO, CH4, and C2H6 while higher amount of hydrogen was produced from steam
pyrolysis.
Figure 27- Comparison of gases produced by pyrolysis PCB sockets using N2 & steam
The conclusion is CO2 gas is dominated in this temperature in all experiments followed by CO, whereas
higher mass of hydrogen were produced through experiments the sockets of PCB that related to ”Gas
evolution phase”, where the hydrocarbons decompose into stable gases such as CO2, CO, H2 and CH4,
when temp access 600°C and following reactions take place (Richards, 2015):
CO2 + C 2CO Boudouard reaction
C + H2O CO + H2 Water gas reaction
50
7.3 Analysis of process outcome Liquids Liquid products obtained from pyrolysis are analyzed during this part. Different types of liquids were
resulted according to the difference in sample material and process. According to diagram (28) below
higher amount of liquid oil was produced from pyrolysis the mb of PCB by nitrogen.
Figure 28- Amount of produced oil from pyrolysis PCB- mb
Figure 29- Amount of produced oil from pyrolysis PCB- sockets
0
5000000
10000000
15000000
20000000
25000000
Comparison between typical- & steam -pyrolysis oil analysis for PCBs mb
Typical pyrolysis Steam pyrolysis
0500000
100000015000002000000250000030000003500000400000045000005000000
Comparison between typical- & steam -pyrolysis oil analysis for PCBs Sockets
Typical pyrolysis Steam pyrolysis
51
From diagram (29) in former page, it is clear that higher amount of liquid was created by using steam.
That´s related to exicting of steam was the reason to convert volatile which performs 63% of total sockets
weight into liquid oil and gaseous components (Diaz & Friedrich, 2015).
In comparison between results of the two previous diagrams deduces that low activity of steam pyrolysis
in producing oil occurs when there are low volatile components in materials of feed stock.
In general liquid product is created from condensable fraction but using steam which reacts with other
elements and transfer to water was the reason that liquid was diluted with water in case of steam
pyrolysis. The complexity of separating between water and oil makes it difficult to estimate the real
yields of oil.
7.3.1 Comparison the amount of produced liquid Diagram (30) below shows that higher amount of phenol was created by treating the main body of PCB
with nitrogen pyrolysis, while the lowest amount was generated from pyrolysis PCB sockets with
nitrogen.
Figure 30- Comparison of amount of phenol as shared product among all experiments
0 5000000 10000000 15000000 20000000 25000000
PCB mb/ N2
PCB mb/steam
PCB sockets/N2
PCB sockets/ stram
Amount of phenol
Amount of produced phenol from all experiments
phenol
52
7.4 Mass balance The mass balance of solid, liquid and gas products of nitrogen- and steam –pyrolysis at 600°C are shown
in table (7). The outcome proportion was calculated per one gram of sample.
Table 7- Mass balance of the four experiments
Experiment
Sample Solid residue Oil Gas Total
PCB mb 600°C N2
10,0911 75,20% 19,99% 1,50 % 96,69%
PCB mb 600°C steam
7,3556 82,43% 12,97% 1,24 % 96,64%
PCB sockets 600°C N2
5,0021 39,70% 31,94% 3,17 % 74,81%
PCB sockets 600°C steam
5,0578 34,59% 36,60% 3,02 % 74,21%
According to the mass balance table, the calculated total mass in case of PCB- sockets were near 75%
for both processes. That´s related to the polymers is complex materials and it represents the
fundamental material in the sockets of PCBs which was the reason to produce amount of an organic
compounds (wax). The wax melting in different temp depending on chemical composition.
Almost 25 cm long of reactor´s lower end was covered by some kind of insolation, and was not
possible to measure the temperature there, probably the temp of this region would be less than 100 °C.
That means some products would stuck on the inner wall of the reactor because the cool region caused
to condense these products. The overall result that has been got was by weighing solid residue and
liquid while gas volume that detected by micro –GC was converted to mass by using ideal gas law
(PV = nRT) but the difference was never measured.
Figure 31- Differ in products amount was resulted from typical & novel pyrolysis
0,00% 10,00% 20,00% 30,00% 40,00% 50,00% 60,00% 70,00% 80,00% 90,00%
PCB mb 600°C N2
PCB mb 600°C steam
PCB sockets 600°C N2
PCB sockets 600°C steam
Outcome prodicts from the four experiments
Gas Oil Solid residue
53
It is clear according to diagram (31) in former page, that the solid residue is dominate in both experiments
when the samples was PCBs- main body, that´s related to the metal fraction was represented the majority
of main body total weight.
In case of PCBs sockets, solid residue and liquid oil results were equivalent with various proportions
according to the type of gas that used during experiments, that´s clear in diagram (32) in below. Higher
amount of solid residue was resulted from treating PCB- sockets through nitrogen process compare with
liquid oil, and the opposite works when steam was used with small difference between liquid phase and
solid residue amount was created.
Higher amount of gases were produced from treating sockets (3%) compare with (1.5%) of gas was
resulted from pyrolysis of PCBs- main body.
The main reason as mentioned before is refered to when pyrolysis is applyed in recycling plastics leads
to convert solid organic into solid cokes and gaseous components. Condensable gases will transfer into
liquid (oil state) and non- condensable gases are formed gaseous components (Diaz & Friedrich, 2015).
Figure 32- Illustrate differ dominate phase in the four experiments
The cumulative material balance for the four experiments is illustrated in figure (33) in the next page.
When steam was utilized in process, it is clear that more solid has got from treating of main body of
PCB even when less weight of sample was used.
Resulted solid residue was 0,82 g of solid/g of sample, while the outcome was 0,75 g of solid /g of main
body sample in case of nitrogen pyrolysis.
0 ,00% 10 ,00%
,00% 20
,00% 30
40 ,00% ,00% 50
,00% 60
,00% 70 ,00% 80
90 ,00%
Solid residue Oil Gas
Differ proportions of outcome
PCB mb 600°C N2 PCB mb 600°C steam
PCB sockets 600°C N2 PCB sockets 600°C steam
54
As mentioned before, the process was done under higher temperature than in case of using nitrogen.
Higher temperature was a reason to more oxidation of elements when oxygen is existed in the system
by reacting steam with other elements.
In case of sockets which are mainly made of plastics, mass balance table indicates that almost 75 % of
material was recovered from the total weight of samples.
Figure 33- Different in amount of pyrolysis products according to experiment´s type
The original contents of the two fractions PCB- main body and sockets have the main role in variation
of both the dominate phase as well as the amount of differ process´s products. That´s clear in table (8)
below, applying nitrogen- and steam process for the main body of PCBs are preferred in producing solid
residues, while higher yield of oil and gaseous phases have created by treating PCBs sockets through
the both pyrolysis process.
Table 8- Illustrates proportion of higher yield according to sample- and experiment –type
Type of product First yield proportion Second yield proportion
Solid residue Mb/ steam 82,43 % mb/ N2 75,20 %
Gas Sockets / N2 3,17 % Sockets / steam 3,2 %
Oil Sockets /stem 36,60 % Sockets / N2 31,94 %
In other wordes, through recycling process of WEEE, choosing the desired product among solid,
liquid or gas, is a reasonable way to determine which are most appropriate E- waste fraction as well
as an oxidizing agent that utilized to get rid of these serious materials.
0,00%
10,00%
20,00%
30,00%
40,00%
50,00%
60,00%
70,00%
80,00%
90,00%
Solid residue Oil Gas
Outcome result from the four experiments
PCB mb 600°C N2 PCB mb 600°C steam PCB sockets 600°C N2 PCB sockets 600°C steam
55
8. CONCLUSION From the present investigation, the following conclusions can be drawn:
Pyrolysis is a separation process and it is a promising method to recovery metal and energy.
Outcome of experiments are solid residue liquid and gas phases. All pyrolysis products are
useful besides they are easy to storage and transport.
Thermal decomposition during process is the reason to reduce mass of solid residue.
High efficiency of steam pyrolysis in producing liquid oil and gaseous components, can attain
when plastics waste is recycled. Take into account that an evolution for separation process of
outcome liquid from water is needed.
From the above concludes that utilizing steam pyrolysis can recommends in recycling plastic
fraction of E- waste, since nitrogen as inert gas causes increasing overall cost in addition to high
technology demands are needed during operation the process. Furthermore low yield of solid
residue is a solid coke not contains precious metals and can be considered as secondary product.
Low efficiency of steam pyrolysis when applied in materials contain low volatile compounds.
Nitrogen pyrolysis is favourable in producing solid residue and liquid oil.
Steam pyrolysis outcome higher weight of solid residue than nitrogen process. That’s related to
PCBs mb contains metal and exciting of Steam leads to oxides those metals.
Carbon dioxide (CO2) is the dominant gas which resulted from steam- and nitrogen -process for
both samples at 600°C.
More decomposition of light hydrocarbon and methane (CH4) lead to increase the amount of
produced H2.
The process of steam pyrolysis needs longer time than typical process.
No flow meter to measure steam flow rate, more time is needed to be stable, inaccurate results
was followed.
Syngas produced by typical pyrolysis (nitrogen) was diluted in nitrogen.
Temperature of system is higher in case of Steam pyrolysis, keep cooling of the connection
tubes between reactor and tar measurement vessel are important.
Both processes were applied in fixed bed reactor, i.e. low capacity and high cost.
Environmental problems would be minimized through Pyrolysis many types of waste.
56
References:
(CRI), C. R. (2014). Present and potential future recycling of critical metals in WEEE.
Abdul Khaliq, M. A. (2014). Metal Extraction Processes for Electronic Waste and Existing
Industrial Routes. Resources 2014, 3.
Antrekowitsch, H. P., & al, e. (2006). Metallurgical recycling of electronic scrap, Proceedings
of EPD Congress, 899-908.
Bhaskar, M. B. (2004). The individual and cumulative effect of (BFR) and (PVC) on thermal
degradation of acrylonitrile–butadiene– tyrene (ABS) copolymer.
Buekens, A., & Huang, H. (1998). Catalytic plastics cracking for recovery of gasoline-range.
Chemistry\\ord. (den 9 April 2014). Dichloromethane. Hämtat från
https://www.chemistryworld.com/podcasts/dichloromethane/7254.article
Diaz, F. ,., & Friedrich, B. (2015). Substract of High recoveryrecycling route of WEEE: The
potential of pyrolysis.
Elretur. (2009). Sweden – world leader in weee collection and treatment.
Evangelopoulos, P. (2015). Pyrolysis of PCBs through a TGA experiments.
Evangelopoulos, P., Efthymios, K., & Yang, W. (2015). Challenge and Opportunity of
Recovery energy and materials from WEEE. Stockholm: Royal Institute of Technology
– KTH.
GC-FID/MS analyzer. (u.d.). Images. Hämtat från
https://www.google.se/search?q=micro+GC&biw=1280&bih=619&source=lnms&tb
m=isch&sa=X&ved=0ahUKEwix3v2GrovNAhVBQpoKHdQXBk4Q_AUIBigB&dpr
=1.5#tbm=isch&q=GC-FID%2FMS+analyzer&imgrc=tyfJwV50GxE6gM%3A
Gkaidatzis, G., Aggelakoglou, K., & Aktsoglou, D. (2009). E-waste – Environmental
Problems and Current Management.
Goosey, M., & Kellner, R. (2002). A Scoping Study End-of-Life PCBs.
Gramatyka, P., Nowosielski, R., & Sakiewicz., P. (2006). Recycling of WEEE.
H. Antrekowitsch, M. P. (2006). Metallurgical recycling of electronic scrap, Proceedings of
EPD Congress, 899-908.
Havlik, T., Orac, D., Petranikova, M., Miskufova,, A., Kukurugya,, F., & Takacova, Z.
(2010). Hazardous Materials Journal. Journal of Hazardous Materials.
Hense, P., Reh, K., & Franke, M. (2015). pyrolysis of WEEE for recovering metals. Jasminská, N., Brestovič, T., & Čarnogurská, M. (2013). The effect of temperature pyrolysis
process of used tires on the quality of output products.
Jinhui Li, H. D. (2010). Characteristic of low-temperature pyrolysis of PCBs.
Kantarelis, E. (2014). Catalytic Steam Pyrolysis of Biomass for Production of Liquid Feedstock.
Stockholm: Royal Institute of Technology.
Kantarelis, E., Evangelopoulos, P., & Yang, W. (2015). Material and Energy.
L., C., & Hieschler, M. M. (2002). Thermal decomposition of polymers- chapter 7 .
Lewis, F. M. (1967). Thermodynamic fundamentals for the pyrolysis of refuse.
Luda, M. P. (2011). Recycling of Printed Circuit Boards. Italy.
Madnel set. (den 19 July 2011). Extraction and Determination of a Distribution Coefficient
(Kd). Hämtat från
http://www.mendelset.com/articles/685/extraction_and_determination_distribution_co
efficient_kd
Mankhand, T. R., Singh, K. K., Gupta, S. K., & Das, S. (2012). Pyrolysis of PCBs.
57
Md. Abdur Rakib, M. A. (2014). Electronic Waste Generation. International Journal of
Scientific Research in Knowledge, 2(10), , pp. 470-479, 2014.
micro- GC analyzer. (u.d.). Images. Hämtat från
https://www.google.se/search?q=micro+gc+analyzer&espv=2&biw=1266&bih=591&
source=lnms&tbm=isch&sa=X&ved=0ahUKEwjg87zF6fzOAhXGGCwKHXUpDFQ
Q_AUIBigB#imgrc=Baq69uaJhavdfM%3A
Navazo, J. M., Méndez, G. V., & Peiró., L. T. (2013). Material flow analysis and energy
requirements of mobile phone material recovery processes.
Richards, T. (2015). Recent Developments in the Gasification and Pyrolysis of Waste.
Singh, B., & Sharma, N. (2007). Mechanistic implications of plastic degradation.
Tangea Lein, D. D. (2004). WEEE plastics with brominated flame retardants - from legislation
to separate treatment - thermal processes.
Tuncuk, A., Yazici, E. Y., Akcil, A., & Deveci., H. (2012). Aqueous metal recovery .
UNU-IAS, I. f. (2014). The global E -waste Monitor .
Vasile, C., & etal. (2006). Feedstock recycling from plastic and thermoset fractions of used
computers (I): Pyrolysis.
weight scale. (u.d.). Images. Hämtat från
https://www.google.se/search?q=weight+scale&espv=2&biw=1280&bih=619&source
=lnms&tbm=isch&sa=X&ved=0ahUKEwigvaG7h_DOAhXFWywKHYvABgQ_AUI
BigB&dpr=1.5
wikipedia. (den 21 October 2016). Dichloromethane. Hämtat från
https://en.wikipedia.org/wiki/Dichloromethane
Wojkiewicz, M. (2015). Pyrolysis and gasification of WEEE.
Zeus, & technical whitepaper. (2005). Thermal Degradation of Plastics.
