A proof-of-concept test for a gas-cooled pressurized phosphoric acid fuel cell is described. After initial feasibility studies in short stacks, two 10 kW stacks are tested. Progress includes: (1) completion of design of the test stations with a recirculating gas cooling loop; (2) atmospheric testing of the baseline stack

Farooque, M.

Hooper, M.

Maru, H.

English

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DOE/NASA/0201 /2
NASA CR-165303
EVALUATION OF DISTRIBUTED
GAS COOLING OF PRESSURIZED PAFC
FOR UTILITY POWER GENERATION
Second Quarterly Report
Dec. 1980 - Feb. 1981
M. Farooque, M. Hooper, H. Maru
ENERGY RESEARCH CORPORATION
3 Great Pasture Road
Danbury, CT 06810
March, 1981
Prepared for
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
Lewis Research Center
Under Contract DEN3-201
r For	 ni
F	 U.S. DEPARTMENT OF ENERGY	 v	 ^' <^'
Energy Technology	 9^
Division of Fossil Fuel Utilization
Under Interagency Agreement DEAI-03-80E717088
(NASA-CR-165303) EVALUATION OF DISTRIBUTED
	 N81-23600
GAS COOLING OF PRESSURIZED PAFC FOR UTILITY
POWER GENERATION Quarterly Report, Dec.
1980 - Feb. 1981 (Enorgy Research Corp.,
	 49	 Unclas
Danbury, Conn.) 19 p HC A02/!!F A01 CSCL 10B MW44 42261
NOTICE
This report was prepared as an account of work sponsored by
an agency of the United States Government. Neither the
United States nor any agency thereof, nor any of their
employees, makes any warranty, expressed or implied,
or assumes any legal liability or responsibility for any
third party's use or the results of such use of any informa-
tion, apparatus, product or process disclosed in this report
or represents that its use by such third party would not in-
fringe privately owned rights.
s
ENERGY nassARCM CORPORATION
TABLE OF CONTENTS
Page No.
	
1.	 EXECUTIVE SUMMARY ...............	 1
	
2.	 TECHNICAL PROGRESS ......... .... 	 1
TASK I. DESIGN AND CONSTRUCTION OF TEST FOUIPMENT FOR
	
x 17 in. (1200 cm)STACK TESTING...... 	 1
	
I.1 RECIRCULATION LOOP ....................... 	 2
I.2	 PRESSURE. VESSEL .......................... 	 2
I.3	 HEAT EXCHANGER ........................... 	 6
	
I.4 DATA ACQUISITION SYSTEM (DAS)............ 	 6
TASK II. TESTING AND EVALUATION OF 5 x 15 in. (350 cm2)
SHORT STACKS	 ..................	 9
	
II.1 TEST STAND MODIFICA'TIONS ................	 9
	
II.2 'T'ESTINr OF STACK P5-1 ...................	 9
	
II.3 TESTING OF STACK P5-2 ................... 	 10
	
3.	 PROBLEMS ......................... 	 12
	
4.	 PLANS ............................	 12
Page No. i
ENERGY RESEARCH CORPORATION
LIST OF FIGURES
FIG. NO.	 Page No.
I.1 A Schematic View of the Recirculation Loop..	 3
I .2 PAFC Pressure Vessel ..........................
	 4
I.3 PAFC Pressure Vessel hole Locations...........	 5
I .4	 Heat Exchanger ................................
	
7
1.5 Data Acquisition Information Flow Dia g ram For
12 x 17 in. (1200 cm ` ) Pressurized Test FaciliLy g
II.1 Lifecranh Of Stack P5-2 ......................	 13
Page No. i i

1. EXECUTIVE SUMMARY
ENERGY RESEARCH C^iRORATRaN
The objective of this program is to provide a proof-
of-concept test of a gas-cooled pressurized phosphoric acid
fuel cell (PAFC). After initial feasibility tests in shorter
stacks, two 10-kW stacks will be tested. Progress made in
different task areas during the second quarter of the program
is summarized below:
Design and Construction of Test Equipment for 12 x 17 in.
cm2 stack Testing
The design of the test station with a recirculating gas-
cooling loop to test 1200 cm 2 short stacks is complete.
Purchase orders for all important subsystem. components are
also placed. Construction of the test station will soon
initiate.
Testina and Evaluation of 5 x 15 in. (350 cm 2 ) Short Stacks
Pressure testin g of Stack P5-1 was not possible because
all the cells devleoped irreversible cross-leaks. However,
stack r5-2 shoes excellent atmospheric performance and pressure
testing of this stack will start shortly.
2. TECHNICAL PROGRESS
TASK I. DESIGN AND CONSTRUCTION OF TEST EnUiP"4ENT FOR
If X 17 IN. STACK TESTING
Task efforts are being closely coordinated with NASD
Contract DEN3-205. Several of the subsystems are similar
and therefore are being designed jointly. The design of the
lone] lead time subsystem components have been finalized and
the purchase orders have also been placed.
Page No.]
;4
Page No-2
INEAOY AESEAACN COM IMNATH M
Construction of the pressurized laboratory and the
setting up of facilities will be completed shortly. The
overhead crane has been installed. Design details of some
of the loner-lead time subsystem components are discussed
below:
I.1 RECIRCULATION LOOP
The final design of the recirculation loop is completed
and is shown in Ficrure 1. A mass flowmeter (Thermal Instrument,
?Model 60) with z. DC signal output will be used to measure the
recirculated qas flow rate in the loop. If need arises in
the future, the coolant flow can be controlled by usin g an
electronic controller. A Rotron Pximax 3 blower_ will be used to
recirculate the coolant flow. The speed of the blower motor
will be varied by a power supply (Volkmann Electric Drives) which
will provide a variable frequency output with tracking voltage.
The speed control can be either manual or computer set. A
butterfly valve will be used to manually close the recircula-
tion flow or to cause some additional pressure drop at lower
flow rates to meet blower. stability _equirements.
I.2 PRESSURE VFSSEL
A pressure vessel with a flat elate bottom (favored over
the shallow, round bottom conf.inuratioh be:-ause of cost
considerations) was desi gned (see Figure I.2). It will accommo-
date the 69 x 53 x 35 cTr (27 x 23 x 14 in.) fuel cell stack
for pressurized operation. The vessel will be made of carbon
steel. On1v the cell bottom and the flan ges will be faced with
SS-316. The pressure vessel dimensions and the hole lavout are
described in Fi gures I.2 and I.3, respectively. A purchase order
has been placed with Norwalk Fabricators of Norwalk, CT for this
pressure vessel alonq with two ether condenser vessels. These
vessels are ex:?ected to he delivered durino the month of !!arch 1951.
PAGE N 0.3
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Page No. 5
Page No.ro
IMMV IMISM" COFAroMT M
I,3 NEAT EXCHANGER
Design of a shell and tube heat exchanger that would
remove neat from the fuel cell recirculation loop is also
completed. Some design details of the heat exchancer are
furnished in Figure 1.4. Hot recirculated cas passes
throuch the shell side which has four passes (equipped
with 3 baffles). Air has been favored over water as the
cooling medium because of contrcl considerations; steam
that could form in the coolant water stream mi ght interfere
with the operations of the coolant flow control valve.
This control valve will interact with the stack temperature
controller and dill regulate the heat removal rate from the
heat exchanger.
Price ouotes for this heat exchan ger were r-btained
from different vendor:, and a purchase order was placed to the
lowest bidder.
I.4 DATA ACQUISITION SYSTI''I WAS)
A floc: diag ram of the DAS to be used for data handling
is shown in riaure I.5. The scanner will be responsible for
reading the measured variables (current, flow rates, temper-
atures, voltaoc s, Pressure and differential pressures). The
microcomputer will record data, control the flow of recircu-
lated stream, and manipulate data. After a detailed examination
of the various available data acquisition and control systems,
a simple, cost effective syste- was selected. This system
is comprised of a Ka ,,re Instru-ents' scanner and an Apple lI Plus
microcomputer. The sm.tem uses flo-anj lsks for data sto rape.
Coolant Air In	 Coolant Air Out
-94_..._^
Recirculating
Stream In
SHELL:
16.8 cm OD x 41 cm L
6-5/8" OD x 16" L
TUBES : - --
0.95 cm OD
3/8" OD -----
(30 U-bends)
All SS-316 construction
Condensate
Drainage 7" mpt
Recirculating
Stream Out
D1439
FIGURE 1.4 HEAT EXCHANGER
Page too. 7
F0
w
DATA ACQUISITION INFORT",ATION FLOW DIAGRAM
FOR 12 x 17 gin. (1200 cm A ) PRESSURIZED TEST FACILITY
C 1448A
. ,
Paqe No. 8
TASK II. TESTING AND EVALUATION OF 5 x 15 in. (350 cm 2 ) SHORT
STACKS
II.1 TEST STAND MODIFICATIONS
The available test stand required some modification to
test 6 cell, 350 cm  stacks. All instruments were received
inspected and installed. Plumbing modifications were also
completed. Anode and cathode lines were successfully leak tested.
Unstabilities in the control operation were observed in both
the fuel and the oxidant control loop. Problems were traced
to a need for larger proportional band width and smaller re-
set time in the pneumatic controllers. TF:o defective synchros
also required replacement. Corrective actions are under way
and after that stack P5-2 will be pressure tested.
I-.2 TESTING OF STACK P5-1
All cells in this stack developed irreversible cross-
leaks which could not be arrested b y fresh acid additions.
After 1.600 hours of testing, stack performance dropped an
average of 140 mV/cell. This stack was disassembled after
1600 hours of testing for diagnostic post-test inspection.
A significant portion of the bipolar plates on the air exit
side were found to be wet. Significant electrochemical
corrosion was also noticed on the wet portion of the cathode
side of the plates. The causes of plate wetting are not well
understood at present; further information is required for
better insight. Howerver excessive acid in the stack coupled
with acid weetwe from the acid channels is a pktential
cause of Mate wetting.
As a precautionary measure, a conservative acid addition
cycle will be followed in future stacks.
Page No. 9
ENEAOII aESEAACH COIMORAUM
II.3 TESTING OF STACK P5-2
The assembly of Stack PS -2 is completed. The special
features of P5-2 which differ from Stack P5-1 are:
• Cooling channel dimensions are 0.43 x 0.27 cm*
(compared to cooling plate dimensions of 0.43 x 0.54
cm for Stack P5-1).
• All three cells on one side of the cooling plate are
assembled with AICMs (acid inventory control members)
Cells on the other side of the cooling plate are
assembled with standard anode backing paper. The
acid addition channels for these two crou ps are
also separated.
• Stack P5-2 has tantalum shims to prevent blockage
at the process aas channel entrace caused by sagging
of the backing paper.
Atmospheric testing of the stack has started and the initial
performance is summarized in Table II.1.
The initial performance of all cells, including the ones
with AICMs, is comparable to the performance of the present
ERC state-of-the-art stacks.
The cells with AICMs have low OCVs. The reasons and im-
plications of this observation are not presently known. Further
experimental results are required for a better understanding.
Furthermore, excellent oxygen gains, 62mV @ 33% oxidant
utilization, and a performance difference of 6mV between 15%
CO2/85% Fie and 100% H 2
 in fuel indicate that the diffusion
polarization at both anode and cathode are ne g ligible in all
the cells; includin g the ones with AICM's.
*	 Dimensions taken before heat-treament
Page No. 10
ENERGY RESEARCH CORPORATION
TABLE. I I .1
PERFORMANCE OF STACK P5-2
PERFOR?V\NCE* V
SELL N0.
Alter 95 hours OCV
1 0.68 0.83
uses
2 AICMs
j
0.67 0.80
3 I	 0.68 0.80
4 0.67 0.85
5 0.58 0.86
6 0.67 0.89
ITOTALL I	 4.05 5.03
* At atmos pheric con
Stack resistance:
Air ter-)erature:
H; temperature:
Stack temperature:
Air flow rate:
H,, flow rate:
Aitions, at 100 mA/cm`'
6 m5?
108°C (in), 181°C (out)
118°C (in), 156°C (out)
183°C
33 lhm ( 9 stoich, 2 stoich thru process channel)
1.5 1pm (80% Hz utilization)
Page No. 11
ENERGY REMARCH CORPORATION
A lifeqraph of the stack (Figure II.1) PS-2, representing
the first 750 hours indicate that the performance of this 	 5
stack is also quite stable with time. Shortly this stack
will be pressure tested.
3. PROBLEMS
Control unstabilities observed in Task II are discussed
in the main text. Crossleak problems were encountered in
Stack P5-1 as described in the text under "Technical Progress".
Apparently the crossleak is associated with some damage caused
durinq back-pressure testing. A more conservative testing
procedure will be used in future experiments.
4. PLANS
TASK I.
• Station assembly
TASK H.
• Pressure testing of stack P5-2, P5-3, and P5-4.
Establishment of baseline pressurized performance
data, start tin/shut dorm procedures and temperature
profiles.
TASK ITI.
• Completion of design of Stack P12-1.
Page No. 12
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Evaluation of distributed gas cooling of pressurized PAFC for utility power generation

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