Fakultät für Ingenieurwissenschaften
FB Maschinenbau / Verfahrens- und
Umwelttechnik
Prof. Dr.-Ing. Wolfgang Pfeiffer
E-Mail: [email protected]
www.hs-wismar.de
Energy Production in WWT
Thermal disintegration of surplus sludge – results of pilot and full scale
investigations at WWTP Grevesmühlen with the Haarslev HCHS system
IWAMA 2nd International Capacity Development Workshop
14. Februar 2017, DWA Nordost, Boltenhagen
Utility company „Zweckverband Grevesmühlen“
Thermal sewage sludge disintegration
Results of bench scale experiments
Results of pilot scale investigations
Full scale results
Results of dewatering in full scale
Influence on sludge drying
Potential savings
Summary and conclusions
Table of contents
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
DBU research project (AZ 31037-23)
Quelle: ZVG; Ausbauzustand des Klärwerks 2002
WWTP Grevesmühlen
Capacity 45.000 PE (current extencion to 65.000 PE)
central sludge treatment plant for 100.000 PE (also for
external WWTPs Dassow, Lüdersdorf, Boltenhagen, …)
Co-fermentation of sludges from grid traps (hotels,
restaurants) and industrial pre-treatment plants (mainly food
industry – i.e. dairy and bread)
Production of 200% of electricity of WWTP consumption
Coverage of the power consumption of pumping stations
and water work Wotenitz of Grevesmühlen
Savings of some 100.000 €/a electricity costs
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Energy balance – WWTP Grevesmühlen
4
Quelle:
Zweckverband
Grevesmühlen
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Basics of sewage sludge disposal
5
A WWTP, that can not dispose its sewage sludge environ-
mentally sound, does not make sense (Karl Imhoff, 1925)
Dried digested sludge is the ideal initial situation for an
environmentally sound and cost optimal solution for sewage
sludge disposal as dried digested sludge is:
almost indefinitely storable
most reduced in quantity –weight and volume
high in calorific value
but:
Drying of digested sludge is energy intensive
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Basics of sewage sludge treatment
6
Tasks of the optimization of the sewage sludge treatment are:
Increase of the degree of degradation in anaerobic
digestion
Less dry matter, more biogas
Improval of the dewatering characteristics
Less sludge mass, less water to evaporate
An approach to optimize sewage sludge treatment is:
Thermal sewage sludge disintegration
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer 7
Basics of sewage sludge disintegration
Tasks of the thermal sewage sludge disintegration are:
Destruction of (intact) cells
making available the cell juice for anaerobic degradation,
improving the dewatering characteristics of the sludge
Decomposition of sewage sludge components
making sewage sludge components available for anaerobic
degradation,
improving the dewaterability due to a reduction of the water
binding capacity of the sludge components
Pinnekamp observed already in the 1980 an improval of the biogas
production due to thermal disintegration and demonstrated the
potential of thermal sewage sludge disintegration.
(Treatment at 120 – 170 °C for 0,5 h +40% biogas from SS)
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Bench scale experiments
2014
Discontinuos and continuos experiments
for several month investigating the effects
of thermal disintegration of SS on
anaerobic digestion
8
2006
First experiments in the wastewater lab of
Hochschule Wismar
Investigation of the influence of a thermal
pre-treatment of SS (surplus sludge) on
anaerobic digestion
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Disintegration at 120 °C
No significant effects on
biogas production in
anaerobic sewage sludge
digestion
9
Mehranfall an Faulgas (120 °C)
-2000
-1500
-1000
-500
0
500
1000
28.1
1.01
30.1
1.01
02.1
2.01
04.1
2.01
06.1
2.01
08.1
2.01
10.1
2.01
12.1
2.01
14.1
2.01
16.1
2.01
18.1
2.01
20.1
2.01
22.1
2.01
24.1
2.01
26.1
2.01
28.1
2.01
30.1
2.01
01.0
1.02
03.0
1.02
Datum
Me
hra
nfa
ll in
ml/d
Fermenter 1
Fermenter 2
Fermenter 3
Mehranfall an Faulgas (140 °C)
-1000
-800
-600
-400
-200
0
200
400
600
800
1000
01.0
9.0
1
03.0
9.0
1
05.0
9.0
1
07.0
9.0
1
09.0
9.0
1
11.0
9.0
1
13.0
9.0
1
15.0
9.0
1
17.0
9.0
1
19.0
9.0
1
21.0
9.0
1
23.0
9.0
1
25.0
9.0
1
27.0
9.0
1
29.0
9.0
1
01.1
0.0
1
03.1
0.0
1
05.1
0.0
1
07.1
0.0
1
09.1
0.0
1
11.1
0.0
1
13.1
0.0
1
15.1
0.0
1
17.1
0.0
1
19.1
0.0
1
21.1
0.0
1
23.1
0.0
1
25.1
0.0
1
27.1
0.0
1
29.1
0.0
1
31.1
0.0
1
Datum
Me
hra
nfa
ll i
n m
l/d
Fermenter 1
Fermenter 2
Fermenter 3
Disintegration at 140 °C
Significant effects on the
anaerobic digestion
20 % increase in biogas
production
0
5000
10000
15000
20000
25000
30000
35000
40000
Fau
lgasan
fall
in
ml
Datum
Faulgasanfall akuum. (120 °C)
Fermenter 0
Fermenter 1
Fermenter 2
Fermenter 3
0
10000
20000
30000
40000
50000
60000
70000
akku
m. F
au
lgasan
fall (
ml)
Datum
Faulgasanfall akkumuliert (140 °C)
Fermenter 0
Fermenter 1
Fermenter 2
Fermenter 3
Bench scale experiments 2006
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Full scale HCHS at WWTP Grevesmühlen
10
Preheater
Steam-
generator
dewatering
HCHS
Cooler
Economiser
Throughput 1 - 2 t/h dewatered SS
15 – 20% DM
Pressuriser
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer 11
HCHS-plant at WWTP Grevesmühlen
Fig. 1-3: WWTP
Grevesmühlen
Fig. 4: WWTP
Wola Dalza,
Łancut, Polen
1 2
3 4
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Results – bench scale - discontinuous
12
Discontinuous experiments with dewatered SS
Biogas production is +30% as a result of disintegration with 160 °C
2014
t Ref/70°C
d ml/g VSS ml/g VSS % ml/g VSS % ml/g VSS %
1 14 215 338 157
2 9 360 412 114 432 120
4 13 315 358 114 447 142
5 14 330 440 133 436 132
6 16 378 500 132
sludge
sample
140°C 150°C 160°C
biogasproduction
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Bench scale continuous experiments – series I
13
continuous bench scale experiments with app. 10% DM for 60 days
Increase in biogas production is +40 % with 160 °C disintegration
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Continuous bench scale experiments - series II + III
14
Continuous bench scale experiments with app. 5% DM
Increase in biogas production is +28% with 160 °C disintegration
and HRT = 16 d
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Pilot scale investigations
15
Operation of 4 pilot scale digesters
with Veff = 500 l
Investigation of the influence of thermal
disintegration on specific biogas
production [l/kg DMadded]
ht-FB1 – mixed sludge*
ht-FB2 – mixed sludge*
ht-FB3 – un-pre-treated surplus sludge
ht-FB4 – thermal disintegrated SS
* Mixture of primary sludge, Co-substrates, thermal
disintegrated and un-pre-treated surplus sludge
Increase of the portion of the thermal disintegrated
surplus sludge in 3 phases of 33% each
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Pilot scale experiments - results
16
Continuous operation over 100 days with app. 5% DM
Increase in biogas production is +28% with 150 – 160 °C and HRT = 18 d
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Pilot scale experiments - results
17
Increase in biogas production +28 %
Increase in oDM degradation +11 %-points (40,3 % 51,4 %)
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Full scale operation – results – biogas production
18
Operation of digester FT2 with mixed sludge with
increasing portions of thermal disintegrated surplus
sludge in 3 phases
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Full scale operation – results – ammonia conc.
19
Modest increase in NH4-N due to increased protein degradation
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Full scale operation – results – COD in solution
20
Increase in COD in solution is app. 500 mg/l in centrate of centrifuge
Increase in COD in WWTP effluent is app. 5 mg/l
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Full scale operation – results - dewatering
Dewatering was investigated with
a full scale HILLER centrifuge
Results:
Digested sludge with thermal
disintegrated surplus sludge
(FT2): 33% TR
Digested sludge with un-pre-
treated surplus sludge
(FT1): 25 % TR
Increase in DM is 8 %-points
Slightly less flocculant
consumption 14 kg/tDM with
25 m³/h throughput
Centrate with good quality
21
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Belt dryer BD 3000/x
22
Partial / full drying
Granular product
Direct heating
Indirect heating
Fexible heat resource
Easy accessibility
Heat recovery
Modular units
Small waste gas flow
Feed of dewatered
slugde
Upper belt
Heat recuperator
Hot air feed to drying chambers
Dried sludge
Condensator
Waste
air
Incinerator
Drying chambers
Lower Belt
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Einsparpotenziale
24
dewatering 1
Thermal Disintegration Belt dryer
PS
Co-generator
Biogas
Etherm
digester
Biogas-
production
+25%
dewatering 2
dewaterability
+8%-points -35% less
dewatered
diegested
sludge
Digester
volume
-37%
- 44% less water
evaporation
30% DM
95% DM
3,5% DM
~20% DM
SS
digested
sludge
Hochschule Wismar – Prof. Dr.-Ing. Wolfgang Pfeiffer
Summary and conclusions
25
The quantity of dewatered digested sludge for disposal is reduced
by 35 %.
In combination with a thermal surplus sludge disintegration a full
drying of the sewage sludge becomes possible with the WWTP
internally produced heat with moderate digestion of co-substrates.
The required drying capacity and the required thermal energy for the
drying can be reduced by thermal surplus sludge disintegration by
almost 50 %.
For disinfection thermopilic digestion instead of disintegration of all
sludge might be considered
The research was finanically supported by DBU (German national
foundation for environmental protection) and Haarslev Industries
Thank you very much for your attention