Rodolfo  Taccani  Robert  Radu    

DEPARTMENT  OF  ENGINEERING  AND  ARCHITECTURE  -­‐  UNIVERSITY  OF  TRIESTE,  ITALY  

 Mauro  ScaglioE  Carmen  Valli  

POWER  GENERATION  SYSTEM  DEPARTMENT,  RSE  SPA,  MILANO,  ITALY    

EFC  2013  –  R.  Taccani  

Assess  the  possibility  to  use  fuel  cells  in  small  scale  biogas  plants  (<10  kWe)    Contents  

Aim of the work and contents

o  IntroducVon  o  Experimental  set  up  

•    Biofilter  •    Fuel  cell  

o  Experimental  results  o  Conclusions  

EFC  2013  –  R.  Taccani  

RSE mobile laboratory at ETRA Biotreatment Centre

Mobile laboratory set up for field tests with real biogas (fuel cells, clean up systems, …).

Up to 40 Nm3day-1 of raw biogas from ETRA (Padua – Italy) for experiments.

Unmanned remotely controlled operation. Safety sensors. Interlocked biogas shut off valve.

Anaerobic digester, Linde “wet” type, thermophilic (55 °C ±1 °C).

≈3 MNm3 biogas/year

≈170 Nm3 biogas/tons processed wastes

Gas engines (2 x 1 MW) for onsite thermal and electric power co-generation

Digester

Gas tank

Mobile lab

EFC  2013  –  R.  Taccani  

Experimental set-up

Digester Gas tank

Electronic  load  

Biotrickling filter Fuel processor

Fuel cell

BIOGAS BIOGAS No H2S

H2 RICH GAS

DC CURRENT

CONTROL SYSTEM

EFC  2013  –  R.  Taccani  

Digester process & biogas output: key parameters

Typical Hydraulic Retention Time (HRT) and Organic Loading Rate (OLR) week patterns.

During the working days higher feeding flow rate and less time to metabolise.

Volatile Fat Acid (VFA) accumulation, acidification and partial inhibition of methanogenic flora.

During the weekend less matter and more time available. Weekly periodicity in CH4 concentration.

M.  ScaglioE,  C.  Valli,  S.  Gallo,  M.  Giomo,    A.M.  Maragnin,  G.  Cicchiello  and  W.  Schnitzhofer,  Biotrickling  filter  for  H2S  treatment  of  a  biogas  fed  fuel  cell:  field  test  results,  Proceed.  21th  European  Biomass  Conference  and  ExhibiVon,  Copenhagen,  3-­‐7  June  2013,    

EFC  2013  –  R.  Taccani  

CH4 and H2S concentration in raw biogas

Sulphur rich agro-food industry wastes feed during weekend.

Sulphate Reducing Bacteria (SRB) less sensible than Methane Producing Bacteria (MPB) to pH (acidification) H2S peak usually comes out before the CH4.

In this digester reactor larger fractions of both CH4 and H2S in weekend raw biogas reveals no competition between MPB vs SRB.

EFC  2013  –  R.  Taccani  

Biotrickling filter features

Inoculum: Thiobacillus sp.

Volume: 260 L (100 L bed)

Temperature: 30°C (20°C÷35°C)

pH: 1.4 (1÷2)

H2S in max: 500 ppmv

H2S out: ≤1 ppmv

Biogas Qmax: 2 Nm3h-1

Sulphur load (LS): 15 gSm-3h-1

Design based on digester historical data and strict requirements of reformer catalysts and fuel cell anode: H2S down to 1 ppm level!

Gas in

Gas out

Acid solution

Bed

Pump

EFC  2013  –  R.  Taccani  

Biofilter operation – Results

Removal Efficiency (RE) > 95%

RE underestimated for low H2S content (<30 ppmv) in raw biogas.

Awite sensor unreliable for very low H2S contents at the biofilter outlet for drift and accuracy.

Despite of high RE sulphur shock loads critical for fuel cell applications.

H2S peaks exceeding 1000 ppmv in raw biogas required fuel cell test to be stopped. Some overload data on biofilter outlet (Awite f.s. 200 ppmv).

Biofilter full recovery within 24 ÷ 48 hrs max.

EFC  2013  –  R.  Taccani  

Why High Temperature PEM Fuel Cells ?

Low  temperature  PEM  technology:  

Catalyst  layer:  Pt  or  Pt-­‐alloy  on  carbon  black  

Gas  diffusion  layer:  (non)woven  carbon  backing  +  microporous  carbon  layer  

Membrane:  Fluoropolymer  with  –SO3H  groups  +  water    

Membrane:  Polybenzimidazole  (PBI)  +  H3PO4  

Catalyst  layer:  Pt  or  Pt-­‐alloy  on  carbon  black  

Gas  diffusion  layer:  (non)woven  carbon  backing  +  microporous  carbon  layer  

High    temperature  PEM  technology:  

EFC  2013  –  R.  Taccani  

Why High Temperature PEM Fuel Cells ?

l  Tolerance  to  fuel  impuriVes  

–  CO  up  to  3%  (~  1%)  

–  H2S  up  to  10  ppm  

l  Simplified  system  at  reformate  

l  Independent  of  humidificaVon  

l  High  chemical  stability  of  membrane  (20.000  hr)  

l  EffecVve  co-­‐  and  tri-­‐generaVon,  direct  use  of  heat  possible  

l  Tolerance  to  fuel  impuriVes  

–  CO  below  100ppm    

–  H2S  below  0.1  ppm  

l  Hydrogen  or  complex  reformer  required  

l  HumidificaVon  required!  

l  Membrane  stability  issue  

l  Complex  co-­‐  and  tri-­‐generaVon    

HT PEMFC (120-180°C)

LT PEMFC (<90°C)

EFC  2013  –  R.  Taccani  

FC and reformer

Fuel  cells  characteristcs  

N.  of  cells   22  

AcVve  area   45  cm2  

Type  of  MEA   PBI  HT  PEM  

Power  @  11.1V,  H2   321  W  

Cooling   Air  

EFC  2013  –  R.  Taccani  

FC and reformer P&I

EFC  2013  –  R.  Taccani  

Results

Time  history  of  the  burner  (Tburn),  reformer  and  shih  stages  (Tref,  Tshi+)  temperatures  during  start-­‐up  and  normal  operaVon.  Fuel:  biogas.  

Water  injecVon  

EFC  2013  –  R.  Taccani  

Results

[Robert  Radu,  Rodolfo  Taccani,  Mauro  ScaglioE,    Carmen  Valli,  HT  PEM  fuel  cell  system  fed  with  biogas:  experimental  characterizaVons,  Proceedings  of  ECOS  2013,  JULY  16-­‐19,  2013,  GUILIN,  CHINA.]  

EFC  2013  –  R.  Taccani  

Results

Stack  performance  curves  obtained  with  pure  hydrogen  and  simulated  reformate  (160°C).  

Simulated  reformate  (SimRef)  containing:  56%  hydrogen,  0.5%  carbon  monoxide  and  the  rest  carbon  dioxide.  

EFC  2013  –  R.  Taccani  

Results

Single  cell  performance  comparison  (BioRef  =  biogas  reformate,  SimRef  =  syntheVc  ref.).    

OperaVng  temperature:  160  °C.  

Effect  of  fuel  composiVon  on  stack  and  single  cell  performance.    

EFC  2013  –  R.  Taccani  

Effect of fuel composition

9

11

13

15

17

19

21

0 5 10 15 20 25 30

stack  volta

ge  [V

]

stack  current  [A]

biogas,  140  °CH2,  160  °CMIX,  160  °C

EFC  2013  –  R.  Taccani  

Effect of load on cell voltage distribution

300

400

500

600

700

800

900

1000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

mV

cell  number

10  A

5  A

OCV

EFC  2013  –  R.  Taccani  

 Stack  and  reformer  efficiency   Biogas.    

Anode-­‐off  rec. Biogas.    

No  anode-­‐off  rec. Stack  electrical  efficiency   𝜂↓𝐹𝐶     [%]

23.2 23.2

Fuel  processor  efficiency   𝜂↓𝐹𝑃   [%] 60.0 47.7

Results

MEA  DegradaTon  

Single  cell  (821h  biogas)   60  µV/h  

Stack  (471h  biogas)   66  µV/h  

Producer  data    (H2  const.  Load,  18.000h)  

6  µV/h    

EFC  2013  –  R.  Taccani  

•  HTPEM  FC  have  proven  to  be  a  viable  opVon  for  biogas  uVlizaVon  even  in  small  scale  plants.  

•  The  variaVon  in  the  quality  of  the  biogas  is  not  affecVng  the  reformer  and  fuel  cell  operaVon  

•  H2S,  using  a  biofilter,  has  not  affected  FC  operaVon.  

•  The  degradaVon,  when  using  biogas,  is  higher  than  that  measured  with  H2,  but  sVll  low  enough  to  allow  thousands  of  hours  of  operaVon.  

Conclusions

   

Thanks  for  your  aVenTon!        

ENESYSLAB    Engineering  and  Architecture  department  University  of  Trieste,  Via  A.  Valerio  10  

34127  Trieste    

taccani@units.it