Waste to Energy System Based on Solid Oxide Fuel Cells: Department - - PowerPoint PPT Presentation

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Waste to Energy System Based on Solid Oxide Fuel Cells: Department Store Case Marvin Mikael Rokni Thermal Energy Section, Technical University of Denmark (DTU) SSMW7 2019 Conference, Heraklion, Greece 26 29 June 2019 DTU Mechanical

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SLIDE 1 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Marvin Mikael Rokni Thermal Energy Section, Technical University of Denmark (DTU)

Waste to Energy System Based on Solid Oxide Fuel Cells: Department Store Case

1 SSMW7 – 2019 Conference, Heraklion, Greece
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SLIDE 2 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Motivation
  • Municipal waste dispose is increasing significantly and must be taken care of.
  • Waste to Energy after basic recycling and producing fuel through waste gasification.
  • Multi generation systems is the most effective way from energetic/exergetic view.
  • Decentralized trigeneration plants for producing electricity, cooling and freshwater.
Waste Gasifier Absorption Freshwater SOFC
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SLIDE 3 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Introduction SOFC = Solid Oxide Fuel Cell Municipal Waste Gasification Plant Syngas Ash Air & Steam Impurities SOFC Plant Electric Power Air Heat Exhaust gases Fresh water Membrane Desalination Absorption chiller Domestic Cool
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SLIDE 4 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Gasifier Plant and its Modelling
  • Waste is dried and pyrolysis and then fed to the gasifier.
  • Drying is made by steam generator (SG) in a steam–loop.
  • Air is preheated in a gasifier preheater (GP) using the product gases from the gasifier.
  • Preheated air and some of the steam from the drying process is fed to the gasifier
  • Gasifier outlet temperature assumed 800°C, while inside temperature is around 1300°C.
  • Syngas is cleaned in a gas cleaner system (such as sulfur and chlorine).
Scrubber Ash Gasifier Steam loop Air GAP Waste Dryer SG Syngas Impurities (Sulfur, chlorine, etc.) Cleaned gas Steam Blower Gas Pump Flare Gas Cleaning System GAP = Gasification Air Preheater SG = Steam Generator
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SLIDE 5 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Modeling Gasifier (cont.)
  • Equilibrium condition at outlet.
  • Mixture of perfect gases.
  • Minimizing the Gibbs energy at outlet, as described in Smith et al. (2005).
  • Introduction of a parameter to account for methane bypass without undergoing
chemical reactions (about 1%). Parameter Value Waste temperature, (˚C) 15 Drying inlet temperature, (˚C) 150 Gasifier temperature, (˚C) 800 Gasifier pressure drop, (bar) 0.005 Gasifier carbon conversion factor 1 Gasifier non-equilibrium methane 0.01 Steam blower isentropic efficiency 0.8 Steam blower mechanical efficiency 0.98 Steam temperature in steam loop, (˚C) 150 Gas blower isentropic efficiency 0.7 Gas blower mechanical efficiency 0.95 Gasifier inlet
  • utet
ash
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SLIDE 6 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Parameter Waste Parameter Syngas C (vol %) 45.39 H2 (vol %) 29.31 Ash (vol %) 20.26 N2 (vol %) 32.39 S (vol %) 0.08 CO (vol %) 25.28 Cl (vol %) 0.08 CO2 (vol %) 5.54 O (vol %) 26.56 H2O (vol %) 5.67 H (vol %) 6.21 CH4(vol %) 1.07 N (vol %) 1.42 Ar (vol %) 0.38 Moisture 18.12 HCl (ppmv) < 10 Cp (kJ/kg) 1.84 H2S (ppmv) < 1 HHV (kW), dry basis 19990 Modeling Gasifier (cont.) Aij ; element j (H, C, O, N) entering in i (H2, CH4, CO, CO2, H2O, O2, N2 and Ar) Amj: element j of leaving compound m (H2, CH4, CO, CO2, H2O, N2 and Ar)          k i i i i p n RT g n G 1 ln                   N j k i w m mj in m ij
  • ut
i j
  • ut
tot A n A n G 1 1 1 , , ,     k i p n RT g k i n G n N j ij j
  • ut
  • ut
i
  • ut
i N j ij j
  • ut
i
  • ut
tot
  • ut
i , 1 for ln , 1 for 1 , , 1 , , ,                     A A    ,N j n n w m mj
  • ut
m k i ij in i 1 for 1 , 1 ,       A A
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SLIDE 7 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy 7 Modelling of SOFC
  • For planar SOFCs developed by DTU – Risø and TOPSØE Fuel Cell (Denmark).
  • Zero-dimensional model allowing to be used for complex energy systems.
  • Calibrated against experimental in the range of 650 to 800°C
  • Keegan et al. (2002), Holtappels et al (1999), Kim and Virkar (1999), Peterson et al.
(2005). t = thickness, σ = conductivity id = current density, ias = anode limiting current conc
  • hm
act Nernst FC E E E E E                      4 1 x10 096 . 1 087 . 13 2 sinh 254 . 1 001698 . T i F T RT E d act d ca ca el el an an
  • hm
i t t t E                                              as d as O H d H conc i i i p i p B E 1 ln 1 ln 2 2
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SLIDE 8 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy 8 Design of SOFC Plant Fed by Syngas
  • Gas cleaner (Desulfurization)
  • Gas pump
  • Anode preheater (AP)
  • Anode side of SOFC
  • Burner
  • Air compressor
  • Cathode preheating (CP)
  • Burner
Air CP AP Burner SOFC Gas Cleaner Off air Off fuel Parameter Value Fuel utilization factor 0.7 Number of cells in stack 75 Number of stacks 160 Cathode pressure drop ratio, [bar] 0.04 Anode pressure drop ratio, [bar] 0.01 Cathode inlet temperature, [°C] 600 Anode inlet temperature, [°C] 650 Outlet temperatures [°C] 780 DC/AC convertor efficiency 0.97 A / c m 2 V o l t a g e 0 . 2 0 . 4 0 . 6 0 . 8 1 1 . 2 1 . 4 1 . 6 1 . 8 2 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6 0 . 7 0 . 8 0 . 9 1 1 . 1 6 5 0 C 7 0 0 C 7 5 0 C 8 0 0 C

E x p e r im e n t M

  • d

e l

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SLIDE 9 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy 9 Absorption Chiller
  • LiBr (Lithium Bromide) is used as
absorbent. Refrigerant (Water/Steam) Pump Valve 1 EVAPORATOR Cooling (return) Cooling (supply) Hot gas in Hot gas out DESORBER 1 LiBr water Weak solution SHX Liquid in e.g. water ABSORBER Cooling demand DESORBER 2 Pump LiBr water CONDENSER Liquid out Valve 4 Valve 2 Valve 3 Parameter Value Desorber gas outlet temp. (°C) 90 Rich solution (–) 0.6195 Week solution (–) 0.548 Condenser outlet temp. (°C) 32 Pressure after valve 1 (bar) 0.008 Pressure after valve 3 (bar) 0.05 Absorber cooling inlet temp. (˚C) 20 Absorber cooling inlet pressure (bar) 16 Hot side outlet temp. for SHX (˚C) 70 Solution pump pressure high/low (bar) 0.8/0.05 SHX = Solution Heat eXchanger
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SLIDE 10 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy 10 DCMD (Membrane Desalination)
  • LiBr (Lithium Bromide) is used as
absorbent. Fresh water DCMD SwP2 Sea Water SwP1 Pump Pump Heat Source Parameter Value Fiber length 0.4 m Inner diameter of fiber 0.3 mm Membrane thickness 60 μm Porosity 75% Membrane conductivity 0.25 W/mK Shell diameter 0.003 m Number of fibers 3000 Packing density 60% Inlet temperature 80°C Ck (individual contribution of Knudsen diffusion) 15.18 × 10–4 [–] Cm (individual contribution of Molecular diffusion ) 5.1 × 103 m–1 Cp (individual contribution of Poiseuille flow) 12.97 × 10–11 m SwP = Sea Water Preheater
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SLIDE 11 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy 11 The Complete Plant Evaporator SHX Absorber Dstrict Cooling Condenser Desorber 1 Desorber 2 Cooling liquid in Cooling liquid out Off Gases Ash Gasifier Steam loop Air GAP Waste Dryer and Pyrolysis SG Gas Cleaner AP SOFC Burner CP Air Off air Off fuel Fres h water DCM D SwP2 Sea Water SwP1 Pump Off Gases
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SLIDE 12 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy 12 Parameter Value MW mass flow (kg/h) 105.3 MW temperature (°C) 15 Drying temperature (°C) 150 Gasifier outlet temperature (°C) 800 Gasifier pressure (bar) 1 Gasifier pressure drop (bar) 0.005 Gasifier carbon conversion factor 1 Gasifier non-equilibrium methane 0.01 Steam blower isentropic efficiency 0.8 Steam blower mechanical efficiency 0.98 Air temperature into gasifier (°C) 15 Syngas blower isentropic efficiency 0.7 Syngas blower mechanical efficiency 0.95 Syngas cleaner pressure drop 0.0049 Blower air intake temperature (°C) 15 Blower isentropic efficiency 0.7 Blower mechanical efficiency 0.95 Gas heat exchangers pressure drop (bar) 0.01 Cathode preheater pressure drop (bar) 0.04 Anode preheater pressure drop (bar) 0.01 Burner inlet-outlet pressure ratio (efficiency) 0.95 Parameter Values Net electric production (kW) 146.56 Freshwater production (kg/h) 179.94 Heat input to DCMD, QFW (kJ/s) 125.66 DCMD efficiency (%) 59.30 Cooling production (kJ/s) 145.34 Fuel consumption (LHV) (kW) 433.35 Total power consumption (kW) 16.394 Off-gases temp. (°C) 90 Electric efficiency, Eq. (2) (%) 33.82 Plant energy efficiency, Eq. (1) (%) 84.55 Plant Performance
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SLIDE 13 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy 13 Effect of SOFC Utilization Factor
  • There exist a point where plant efficiency
and power maximizes.
  • This optimum value is 0.7.
S O F C u t i l i z a t i o n f a c t o r [ ] E f f i c i e n c y & C e l l v o l t a g e N e t p o w e r 0 . 6 0 . 6 5 0 . 7 0 . 7 5 0 . 8 0 . 8 5 0 . 0 8 1 5 0 . 1 6 3 0 0 . 2 4 4 5 0 . 3 2 6 0 0 . 4 7 5 0 . 4 8 9 0 0 . 5 6 1 0 5 0 . 6 4 1 2 0 0 . 7 2 1 3 5 0 . 8 1 5 0

C e ll v

  • lt

a g e [ V ] E le c t r ic a l e f f ic e in c y , E q . ( 2 ) N e t p

  • w

e r [ k W ]

  • Increasing utilization factor increases
current density.
  • At a certain current density, the
concentration losses increases exponentially and thereby decreases cell voltage as ell as power. S O F C u t i l i z a t i o n f a c t o r [ ] C u r r e n t d e n s i t y P o l a r i z a t i o n s 0 . 6 0 . 6 5 0 . 7 0 . 7 5 0 . 8 0 . 8 5 1 1 0 0 1 1 5 0 0 . 0 3 1 2 0 0 0 . 0 6 1 2 5 0 0 . 0 9 1 3 0 0 0 . 1 2 1 3 5 0 0 . 1 5 1 4 0 0 0 . 1 8 1 4 5 0 0 . 2 1 1 5 0 0 0 . 2 4 1 5 5 0 0 . 2 7 1 6 0 0 0 . 3

C u r r e n t d e n c it y [ m A / c m

2

] C

  • n

c e n t r a t io n [ V ]

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SLIDE 14 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy 14 Effect of SOFC Operating Temperature and Utilization Factor
  • Opening the valve for chiller increases
cooling production (more off-gases to chiller);
  • Thereby, freshwater production
decreases.
  • Opening the valve beyond 95% , then the
freshwater device (DCMD) must be
  • decoupled. This is due to the pinch temp
associated with the DCMD heat exchanger. S p l i t t e r f r a c t i o n [ ] F r e s h w a t e r a n d C o o l i n g 0 . 2 0 . 4 0 . 6 0 . 8 1 5 2 5 0 5 6 1 0 0 6 0 1 5 0 6 4 2 0 0 6 8 2 5 0 7 2 3 0 0 7 6 3 5 0 8 0

F r e s h w a t e r [ k g / h ] C

  • lin

g [ k J / s ] T S w P 2 , h o t i n T S w P 2 , c o l d o u t

  • Opening the valve for chiller increases
plant efficiency because chiller performance is higher than the desalination performance.
  • Even though desalination performances
increases with opening the chiller valve. S p l i t t e r f r a c t i o n [ ] E f f i c i e n c y [ ] a n d C O P [ ] 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6 0 . 7 0 . 8 0 . 9 1 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6 0 . 7 0 . 8 0 . 9 1 1 . 1 1 . 2  D C M D

C O PA C C O PD C M D

p l a n t

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SLIDE 15 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Effect of Moisture Content
  • Waste moisture may changes significantly from day to day.
  • Increasing moisture content results in decreasing plant performance. All production
decreases.
  • Higher moisture content means also lower fuel energy (LHV) and therefore plant
performance remains unchanged. M o i s t u r e c o n t e n t [ % ] E f f e c t [ k W ] F r e s h w a t e r [ k g / h ] 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8 3 0 1 1 0 1 3 0 1 2 0 1 4 0 1 3 0 1 5 0 1 4 0 1 6 0 1 5 0 1 7 0 1 6 0 1 8 0 1 7 0 1 9 0

C

  • lin

g F r e s h w a t e r N e t p

  • w

e r

M o i s t u r e c o n t e n t [ % ] E f f i c i e n c y [ ] T e m p e r a t u r e [ C ] 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8 3 0 4 0 0 0 . 1 4 0 5 0 . 2 4 1 0 0 . 3 4 1 5 0 . 4 4 2 0 0 . 5 4 2 5 0 . 6 4 3 0 0 . 7 4 3 5 0 . 8 4 4 0 0 . 9 4 4 5 1 4 5 0

E n e r g y e f f ic ie n c y , E q . ( 1 ) E le c t r ic a l e f f ic ie n c y , E q . ( 2 ) B u r n e r t e m p e r a t u r e

(1) (2) ` net FW plant fuel fuel P Q Cool m LHV η + + =
  • &
` net plant fuel fuel P m LHV η =
  • &
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SLIDE 16 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Conclusions
  • The electrical efficiency of the plant is about 34% with a net power of 145 kW.
  • Connecting the absorption chiller and seawater desalination systems in parallel as
bottoming cycle for the fuel cell plant then freshwater and cooling productions will be about 180 liter/hour and 145 kW respectively when waste heat from SOFC plant divides equally between AC and DCMD plants.
  • The suggested designs offer the possibility to regulate freshwater and cooling
productions after demand.
  • Effect production (electricity, cooling and freshwater) depends on the moisture of
the feed waste while plant total efficiencies (electrical and energy) does not change significantly.
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SLIDE 17 DTU Mechanical Engineering 26 – 29 June 2019
  • Dr. M. M. Rokni
SSWM7 – 2019 Heraklion Waste to Energy Thank you for your attention.