This is my pre-Ph.D thesis presentation. DEA in Spanish academic system. Thought it's been long since I finished, I'd love of assisting you!

1. Design of an advanced integrated energy
system based on micro gas turbines for
waste water treatment plants
DEA Work. Ph-D. in Chemical and Process Engineering
Academic years 2003-2005.
Universitat Rovira i Virgili
Víctor Ortega-López
Tutor: Joan Carles Bruno
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2. Summary
1. Biogas
2. Applied technology
3. WWTP Reus
4. Base case
5. Biogas Pretreatment
6. MGT configurations only with biogas
7. MGT NG + Biogas
8. Chillers configurations
9. Economical analysys
10. Performance analysis
11. Conclusions
12. Back-up
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005
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3. Project motivation
Development of using Biogas must cover the 13% of all
renewable energy sources renewable energy sources by 2010*
Improvement of Waste water Cost reduction of treated water and
treatment plants reliable use of by-products (biogas)
Application of new technologies Most common technology
that simultaneously produced (Reciprocating engines) seems to have
not further development
electricity and thermal energy
“BIOPROM – Overcoming the Non-technical Barriers of Project-
implementation for Bioenergy in Condensed Urban Environments”
Intelligent Energy - Europe Programme, EIE/04/100/S07.38585.
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005
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4. Objective
“The objective of this DEA work is to design advanced
integrated energy system (AIES) to cover the heating demand of
a waste water treatment plant and to co-produce simultaneously
power and cooling.
The AIES is based on MGTs technology for heat and electricity
production, and on absorption chillers for cooling production.
The generated electricity will contribute to reduce the electrical
bill, and the cooling will be used to cool the biogas to reduce its
moisture content and the air inlet to MGTs.”
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005
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5. Characteristics of biogas
Primary energy source
Produced by anaerobic digestion of the organic
matter suspended in waste water by mesophilic
and thermophilic microorganism
Low Methane content (50-70%) Low heating power
Natural Gas: 49600 kJ/kg Hard to be used by
Biogas (65%CH4): 20800 kJ/kg commercial engines
Its main use in Europe is to be burned in flares
The EU energy potential of converting waste water’s
sludge’s is given as 20,000 GWh/year
High content of impurities: siloxanes, sulphides, etc.
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005
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6. Micro Gas Turbine Technology
Main technical characteristics of MGTs
Operates as a Brayton cycle
Low compression ratio ( 3 < r < 5 )
One stage centrifugal compressor of
axial flux coupled to a turbine
High speed alternator (75000-100000
rpm) directly coupled to the turbine
rotor
Combustion chamber
Regenerator
Commercial debut in 1998
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005
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7. Micro Gas Turbine Technology
Advantages and disadvantages
Power range: 20 – 200 kW
Low maintenance cost
Very compact
High reliability
Low emissions
High exhaust gas temperatures
Flexible to use different fuels
Lower efficiency in its basic configuration than
an equal power output reciprocating engine.
Efficiency decreases significantly at part load
High qualified maintenance workforce
Need of fuel conditioning systems
High investments
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005
5

8. MGT Performance
32,00 30,00
29,00
30,00
28,00
Net elect. efficiency (%)
27,00
28,00
Wnet (kW)
26,00
26,00 25,00
24,00
24,00
23,00
22,00
22,00 W net
Net eff. 21,00
20,00 20,00
0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00
Ambient Temperature
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005
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9. Reus Waste Water Treatment Plant
BIOGAS
105 Nm3/h, at 35ºC and 1,2 bar
Annual capacity 6 millions of m3 Average.
Component
water (110.000 equivalent-inhabitants) value
CH4 % 64
Nominal capacity 25000 m3/day CO2 % 31,4
Treated water flow 17000 m3/day H2O % 3
Treated sludge flow 220 Tm/day
H2 % 0,2
Sludge dryness 25 %
Sludge Temp inlet to H2S ppm 100
35 ºC Siloxanes ppm 50
2nd digester
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

10. Case Study
Reus Waste Water Treatment Plant
600,0 600,0
500,0 500,0
400,0 400,0
kWth
kWe
300,0 300,0
200,0 200,0
Heating demand
100,0 Electric demand 100,0
0,0 0,0
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DEA Work – Víctor Ortega-López * Heating demand calculated according
Ph-D. in process engineering 2003-2005 to ambient temperature

11. Design model of the AIES
MGT Capstone C30 for Biogas and Natural Gas
Electricity Reduction of electrical bill
Exhaust Heat Exchanger
Hot Water Heating of 1st and 2nd digesters
Absorption chiller
- Single effect water driven LiBr/water Absorption chiller
- Exhaust direct fired ammonia/water Absorption chiller
- Double effect exhaust direct fired LiBr/water Abs.
chiller
Cooling of air to MGTs
Cooling
Moisture condensation in biogas
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

12. AIES configuration
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

13. Design model of the AIES
Performance
Q total + W net,system + Q cooling
Fuel Utilization Factor FUF =
H NG + H biogas
= η Heating + η electric + η cooling
H biogas
Biogas utilization fraction BioUF =
H NG + H biogas
W net, system - W bio,comp
Electric coverage (%) EC = ·100
W grid
Economics
(Differential inversion cost respect to the base case)
Payback coefficient PBP=
(differential benefit respect to the base case)
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

14. Raw biogas
input
Biogas pre-treatment
Sediment
trap
Removal of Siloxanes (max. 5ppb) Adsorption on
Removal of Sulphides activated carbon Liquid/gas
separator
Drying
Dryer
Compressor
Moisture
condenser
High O&M cost (35000€/year)
Siloxanes/H2S
MGT O&M Co&m,mgt 0,005 €/kWh removal
Rest of installation M&O Co&m,rest 0,005 €/kWh
Biogas pretreatment Co&m,rest 0,01 €/kWh
MGT
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

15. Base case configuration
Current situation
600,0 50,00
45,00
500,0
40,00
Kg/h Additional Natural gas
35,00
400,0
Flare 30,00
kW (th)
300,0 25,00
Natural Gas Additional NG Heating 20,00
200,0 Overall Heat demand
15,00
Heat produced by biogas
Biogas 10,00
Boiler 100,0
5,00
0,0 0,00
Digesters
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% Biogas = 86,4
DEA Work – Víctor Ortega-López
Electric coverage = 0%
Ph-D. in process engineering 2003-2005 FUF = 80 %

16. AIES configuration
Case 1(a): MGT with biogas + Boiler with NG
Cooling Cooling is provided by
standard electric
Exhaust refrigeration
recuperator
Biogas
%Electric coverage = 37,2 %
Biogas %Biogas = 63,52%
pretreatment
MGTs Elec. FUF = 72,75%
MGTs
MGTs
Air Air cooling
NG Boiler
Digesters
Heating
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

17. AIES configuration
Case 1(b): MGT with biogas + Boiler with NG + Water driven Absorp. chiller
Absorp.
Chiller All biogas is consumed in
MGT
Cooling Exhaust Cooling is provided by an
recuperator
Biogas
absorp. Chiller
Biogas
pretreatment
MGTs Elec. %Electric coverage = 38,4 %
MGTs
MGTs %Biogas = 62,06%
Air Air cooling FUF = 72,8%
NG Boiler
Digesters
Heating
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

18. AIES configuration
Case 1(c-d): MGT with biogas + Boiler with NG + direct fired Absorp. chiller
Absorp.
Chiller All biogas is consumed in
MGT
Cooling Exhaust Cooling is provided by a
recuperator
Biogas
direct fired absorp. Chiller
Biogas
pretreatment
MGTs Elec. %Electric coverage = 38,4 %
MGTs
MGTs %Biogas* = 62%
Air Air cooling FUF = 72,7%
NG Boiler
Digesters
Heating
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

19. AIES configuration
Case 2 (b): MGT with biogas + MGT with NG + water driven Absorp. chiller
Absorp. All biogas is consumed in
Chiller MGT
Cooling Exhaust
Some MGTs with NG shall be
recuperator powered off during summer
Biogas
Biogas
season
pretreatment Higher number of MGT,
MGTs
MGTs
MGTs
Elec. higher cooling demand for
Air Air cooling air conditioning
MGTs
MGTs
MGTs
Elec. %Electric coverage = 86,5 %
NG
Digesters %Biogas = 47%
FUF = 69,3%
Heating
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

20. AIES configuration
Case 2 (c-d): MGT with biogas + MGT with NG + direct fired Absorp. chiller
All biogas is consumed in
Absorp.
Absorp. MGT
Chiller
Chiller Some MGTs with NG shall be
Cooling Exhaust
powered off during summer
recuperator season
Biogas
Biogas
Higher number of MGT,
pretreatment higher cooling demand for
MGTs
MGTs
MGTs
Elec. air conditioning
Air Air cooling
One chiller cannot afford the
cooling requirements,
MGTs
MGTs
MGTs
Elec. therefore efficiency losses
NG
Digesters are admitted
Heating %Electric coverage = 87,8 %
%Biogas = 47%
DEA Work – Víctor Ortega-López
FUF = 69,4%
Ph-D. in process engineering 2003-2005

21. Chillers configuration
450,00
Vent
Vent
Auxiliary
400,00 Abs. MGT Abs.
MGT Waste Heat
Chiller Chiller
Boiler
350,00
MGT Waste
MGT Waste Heat MGT Heat
MGT Boiler Boiler
300,00
MGT
MGT
kW NG
(b) Absorption chiller connected exclusively to one MGT,
(a)250,00
Absorption chiller connected exclusively to one MGT
recovering the exhaust gas heat (160ºC) in an auxiliary
venting the exhaust gases boiler
200,00
Vent Abs. Vent
Abs.
Chiller Chiller
150,00 Chiller to one MGT
venting exhaust gas (a)
Waste MGT Waste
MGT Chiller to one MGT with
100,00
MGT Heat MGT Heat
auxiliary boiler (b)
Boiler MGT Boiler
MGT MGT
MGT Chiller in exhaust gas net
50,00 (c)
(c) Absorption chiller connected in bypass with the exhaust
(d) Absorption chiller connected to the exhaust gas collector,
gas collector
venting the exhaust fraction used.
0,00
1 2 3 4 5 6 7 8 9 10 11 12
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

22. Economical analysis
Best Economical Case
Absorp. Capital
O&M
Chiller Fix Cost Variable cost Total cost PBP
amortization
€/year €/year €/year €/year €/year %
Cooling Exhaust
Case 0 19091 1632
recuperator 10111 268535 278646
Case 1-A 58511 41310 49789 237973 287762 130
Biogas1-B
Case 58511 42347 50826 236910 287736 129
Biogas
Case 1-C (a) 58511
pretreatment 42500 50979 243163 294142 161
Case 1-C (b) 58511 42636
MGTs 51115
Elec. 239439 290554 141
Case 1-D (a) 58511 MGTs
MGTs
43197 51676 242451 294127 159
Case 1-D (b)
Air 58511
Air cooling 43197 51676 237663 289339 135
Case 1-D (c) 58511 44268 52747 237155 289902 136
Case 2-A 65315 63937 72416 170008 242424 63
MGTs
MGTs Elec.
Case 2-B 65315
NG 65297
MGTs 73776 158243 232020 58
Digesters
Case 2-C (b) 65315 65042 73521 160609 234131 59
Case 2-D (b) 65315 66997 75476 158510 233986 59
Heating
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

23. Economical analysis
25000
20000
15000
€/month
Electricity
O&M
NG
10000 Fix cost
5000
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DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

24. Economical analysis
Influence of tariff conditions
350000
300000
250000
€/year
200000
0,022 €/kWh
150000 Case 0
Case 1-B
Case 2-B
100000
0,01 0,015 0,02 0,025 0,03
NG Tariff [€/kWh]
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

25. Economical analysis
% electrical coverage
Case 1A
120,00 Case 1B
Case 1C
Case 1D
100,00 Case 2A
Case 2B
Case 2C'
80,00 Case 2D
% coverage
60,00
40,00
20,00
0,00
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DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

26. Conclusions
Current production rates of biogas are not enough to cover the heating
demand. Additional NG have to be burned.
AIES using MGT exclusively biogas are not economically optimal due
to the high cost of biogas pre-treatments.
Tariff situation encourages the use of MGT with NG to produce as
much electricity as possible
AIES (MGTs) at part load (during warm season) has worse performance
than full load.
Direct fired water/ammonia chiller has the worst performance due to
the high heat lost. Double effect chillers with higher COP value
improve this performance.
Parallel connection of absorption chillers are better than direct vented
or coupled to one MGT.
MGT’s has a promising future as far as the technology improve
efficiencies.

27. Design of an advanced integrated energy
system based on micro gas turbines for
waste water treatment plants
DEA Work. Ph-D. in Chemical and Process Engineering
Academic years 2003-2005.
Universitat Rovira i Virgili
Víctor Ortega-López
Tutor: Joan Carles Bruno

28. Back-up
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005

29. References
The European Renewable Energy Study: Prospects for
Renewable Energy in the European Community and Eastern
Europe up to 2010, DG XVII, 1994
DEA Work – Víctor Ortega-López
Ph-D. in process engineering 2003-2005
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