Waste to Energy Initiatives
• National importance
• Shall be very popular soon
MSW
Mass Burning
Steam / Power
landfill Gas recovery Burn in Boiler
RDF Burning
Anaerobic digestion
Thermochemical Decomposition
Incineration of Municipal Solid Waste
(MSW)
Waste /CoalPreparation
Waste /CoalFeeding FURNACE
Bottom Ash Heat Recovery
Particle Removal
Acidic Gas Removal
STACK
Waste/Coal Aux Fuel
ID Fan
FD Fan
Heat
Flue Gas
For treatment & disposal
Gas out
TYPES FURNACES
• Stocker / Grates Type• Rotary Kiln Type• Fixed Hearth• Multiple Hearth• Cyclonic• Fluidized Bed
• MSW Mass Burning• Any type of waste• Biomedical wastes• Sewage Sludge• High heat content• Any kind of waste
Fluidized BedA bed of fine solids(usually sand)suspended in air
The gas from thebottom of thecolumn via a gasdistributor causesthe particles tofluidize
Ways of Heat Recovery
• Use a boiler to produce steam / hot water• Use a heat exchanger to pre-heat the
ambient air which can be used for combustion
• Use a heat exchanger for drying solid wastes/ concentrating liquid waste
• Use water-wall to generate steam / hot water
Heat Exchangers• To exchange heat from one fluid to another• Heat flow higher temperature side to lower
temperature• Usually no mixing up of fluids (sometimes,
they get mixed up)• Enough heat transfer area to be provided for
the heat to transfer• There are different designs / types available
Counter Current
EMISSIONS FROM INCINERATION,The emission from incineration are as follows:
1. PARTICULATE MATTERS
2. OXIDES OF NITROGEN
3. OXIDES OF SULPHUR
4. Heavy Metals
5. HCl, HF
6. CHLORINATED HYDROCARBONS (Dioxins & Furans)
7. PAH (Poly Aromatic Hydrocarbons)
8. CO
9. CO2
14
Equipment Pollutant Removed % Removal Pressure DropInches of Water Column
Settling Chamber Large particles 0 to 30 % 0.5 to 1
Multiple Cyclones Particles 30 to 80 % 3 to 4 (single cyclone: about 1)
Venturi Scrubber Particles & acidic gases like HCl, SO2
80 to 96 % 10 to 50
Packed scrubber Aerosols & acidic gases
80 to 96 % 6 to 8
ESP Fine particles 90 to 97 % 0.5 to 1
Fabric Filter bag House
Fine particles 97 to 99.9 % 1 to 8
15
Air Pollution Control
• Normally air pollution control involves more than one unit depending upon the flue gas and the requirements of the law
Removal ofcoarse particles
Removal ofFine Particles
Removal ofAcidic Gases
16
17
18
Basic Principle of Electrostatic Precipitator (ESP)19
Bag Filter House
20
21
Venturi Scrubber
22
Packed Scrubber
23
TIMARPR PLANT - MASS BURNING OF MSW - 1987
• Danish Design (Mukund-Volund)• Rs. 25 Crores• To generate 3.56 MW power from 300tones
MSW /day
• It was a failure
TIMARPUR INCINERATION FACILITY
Reasons for Failure
Wrong assumption of the heat contentHeat content assumed: 1462 Kcal/kgActual heat content: 700-900 kcal/kg
Wrong assumption of the inert contentInert content assumed: 10% by wtActual inert content: 30-50%
MSW Characteristic Vs time
• Heat content increases (avg. now 1200-1300 kCal/kg)– More paper / cardboard– More plastics– More cloths– More rubber / leather
Moisture & Inert content decreases: Less glass / metals / C&D waste
New Incineration Initiatives for MSW
• The Okhla MSW Mass Firing Incineration facility
• The Ghazipur MSW RDF-Incineration facility
Okhla MSW Mass Firing Incineration facility
• Burning raw MSW• Private –Public Partnership initiation• Jindal Urban Infrastructure Ltd
• Average calorific value 1200kcal / kg
• 1350 tons of raw MSW 14 MW
Ghazipur RDF-Incineration Facility
• 1300 tones of raw MSW / day 12 MW
• Based on DST-TIFAC technology
• First RDF (Refuse Derived Fuel) generated
• Then burning of RDF to generate Power
RDF Initiatives
• DST RDF Plant in Deonar, Bombay in 1990’s
• SELCO RDF Plant near Hyderabad, Andhra Pradesh in 2000’s – not in operation now ???
• Bangalore plant
REFUSE DERIVED FUEL
• Dry the MSW• The burnable fraction of the waste
is separated, shredded• then made pellets (using die) or
briquettes by pressing. • The pellets are made with or
without a binding agent
• Heat content of RDF is more or less uniform.– For Fluff – 3500kCal /kg– for pellets – 4000 kCal/kg
• RDF can be burnt to produce power or can be used along with conventional fuels
• In India, there are a few RDF plants at present
Co-Incineration
Co-incineration
• Co-incineration of MSW with ????• Co-incineration with Biomedical waste• Co-incineration with agro-wastes• Co-incineration with Hazardous wastes• Co-incineration in cement kilns
Co-Processing
Co-processing in cement industry refers to thesubstitution of primary fuel and raw material bywaste, recovering energy and material from waste.
Waste materials used for co-processing are referredto as alternative fuels and raw materials (AFR).
Cement Kiln Suitability
High temperatures (1400 O C) and residence time of 4 – 5seconds in an oxygen–rich atmosphere ensure the destructionof organic compounds.
Any acid gases formed during combustion are neutralized bythe alkaline raw material and are incorporated into the cementclinker.
Interaction of the flue gases and the raw material present inthe kiln ensures that the non–combustible part of the residueis held back in the process and is incorporated into the clinkerin a practically irreversible manner.
No waste is generated that requires subsequent processing.
Benefits of Co-processing
Reduction in Green House gases emission& related benefit of carbon trading
Conversion of waste into energy / as araw mix component
Conservation of fossil fuel resource
Reduction in energy / cement productioncosts
Final Disposal
• Land-dumps
• Engineered Landfills (Dry Tomb)
• Bioreactor landfills
DRY TOMB CONCEPT OF LANDFILLS
• As per the MSW (Management and Handling) Rules of 2000– No biodegradable waste ban be land-filled– Biodegradable waste should be processed for
some recovery• Composting - compost• Vermi-composting - vermi-compost• Incineration - steam / hot water / power• Biomethanation - fuel gas
– Wastes good for nothing goes to a landfill
‘Dry tomb’ engineered landfills for wastes
Landfill Construction
Final cover
Daily cover
Intermediate cover
Liner For MSW Landfill (India)
Leachate is then sent to Treatment and/or Storage Facility
Landfill
PumpStation
Gravity Drainage
LeachateStorage
Treatment
Landfill Gas is Typically Extracted to a Blower-Flare Station
Landfill
Note:Must DrainCondensate
BlowerFlare
Station
Gas Wells
MSW Landfill (India)
Economics / Cost involved
• Cost of geo-membrane: 50 cents to 1$ per square feet
• Cost of geo-textiles: 50 cents per square feet• Cost of geo-nets: 1$ per square feet• Tipping fee in US: 20$ to 50$ per tonne of
MSW• Landfilling cost in India: Rs. 200 to 500per
tonne of MSW, Rs. 2000 per tonne of Hazardous Wastes
Are you happy with Dry Tomb Landfills ???
• MSW is to be processed first for recovery• Composting or vermi-composting
• Long time for stabilization of waste• Landfill area is blocked for about a century• Leachate is to be treated and managed
• Any alternative ?? Yes…………. Go for another concept
BIOREACTOR LANDFILLS
• Landfill is considered to be a big bioreactor• No processing of biodegradables• Leachate is collected; but circulated back to
the landfill• Waste stabilization is much faster
• Aerobic – 5 to 8 years• Anaerobic – 8 to 12 years
• Landfill area is available for re-use quickly• Landfill becomes ‘sustainable’
Against the rules ?
• YES. Bioreactor landfills are not allowed in India now
• But there are on-going attempts to make bioreactor landfills in India
• Research is on in this area:• University of Florida• Anna University• IIT Delhi
Waste+ Water
+ Microorganisms
ExhaustGas
Vertical Injection Cluster Wells
Use multiple smalldiameter wells.
Subsurface Application of LeachateVertical Systems
Essential Needs for a Bioreactor
• Composite liner• Appropriate density of MSW• Appropriate daily cover• Leachate recirculation system• Active gas collection system• Appropriate final cover system• Competent landfill operator
Benefit: Leachate Management
• Important factors:
– Storm water management
– Leachate storage
Benefit: More Feasible Gas-to-Energy
• Increased gas production during a shorter time frame may make the economics of landfill gas to energy more attractive
0 10 20 30 40Time (Years)
Gas
Vol
ume Bioreactor Landfill
Traditional Landfill
Time (Years)
Concern: Uncontrolled Liquids Addition
• If leachate is added at too great of a rate, leachate breakouts and seeps can occur.
• Even under normal operating conditions, seeps can occur because of nature of waste and cover soil in a landfill
Concern: Uncontrolled Liquids Addition
• Problems with seeps:– Off-site leachate
migration
– Odors
– Vectors
– Path for gas emission
Landfill Seeps
High PermeabilityCover Soil
Leachate Seep(Outbreak)
Interception of leachate by highpermeability cover layers and subsequent transmission of leachateto the side slopeof the landfill can resultin seeps
Lesson 9, Slide 63
Landfill Seeps
Low PermeabilityCover Soil
Leachate Seep(Outbreak)
Interception of leachate by lowpermeability cover layers and subsequenttransmission of leachate to the side slopeof the landfill can result in seeps
Concern: Slope Stability
• Excessive pore water pressures in a landfill can lead to instability problems.
• Strength of waste may become reduced following decomposition.
Concern: Increased Gas Emissions• If uncontrolled, increased gas
production from bioreactor operation
• Bioreactor landfills may require different types of gas collection systems compared to traditional landfills (wells can become flooded).
• When methane is mixed with the right amount of oxygen, an ignited flame can be sustained.
• Most landfill gas as it exists in the landfill, a gas well or an extraction pipe (≈ 50% CH4, 50% CO2), does not contain enough oxygen to support a flame. It is not explosive.
• Only when the gas is mixed with the appropriate amount of air can a flame occur (5 to 15 % by Volume)
Flammability of Landfill Gases
• Initial capital costs and operation costs may be greater for bioreactor landfills compared to those of traditional landfills
• At most operations this can be offset by the gains as described previously
Concern Costs
Bioreactor Challenges• Long-term sustainability• Liquids management• Airspace recovery• Aerobic vs. anaerobic• Heterogeneity of waste• Geotechnical Stability
Public Acceptability
• Very difficult• Mostly there is much truth in the public
allegations• What is the solution ???
To sum up...................
• Technological innovations and infrastructure development in the area of solid waste management have been remarkable in the recent past
• These are mostly aimed at coping up with the rapid urbanisation and population growth
• Biological treatment techniques like composting has been getting the priority
• Innovations in composting have been mostly to reduce the time required.
• Still has not achieved the required speed
• Waste to energy initiatives are always welcome in India
• Thermal techniques will come only after biological techniques
• There are scenarios where thermal techniques are a must or preferred
• Go for them only if sufficient funds are available
• Incineration is the most popular of the thermal techniques at present
• As a technology, there is nothing wrong with incineration
• In fact incineration is very helpful to dispose of different wastes in a rapid way
• Also, this technology becomes useful in the situations where other techniques fail
• This is relatively fool proof and needs less space
• On the other hand, it is a costly technique
• Power generation is not the primary objective of incineration
• Safe waste destruction is the primary objective
• Choose the technology based on the type of waste and the destruction requirements
• Never burn chlorinated plastics (like PVC)
• Ensure enough funds for operating the facilities
• Make it economically and environmentally sustainable
• Choose the appropriate technology based on:-
• the type and characteristics of waste• destruction requirements• suitability to the locality• Long term viability
• More waste to energy plants are expected to come up in India
Thanks to
Dr. Dinesh KumarMunicipal Corporation of Delhi
Prof. Manoj DattaIndian Institute of Technology, Delhi
Prof. Timothy G. TownsendUniversity of Florida
Dr. Kurian JosephAnna University, Madras