800

0 0.1 02 0.3 0.4 0.5 0.6 0.7 0.8 09 1 Reactor dlmenslonless length

A model to calculate the gas composition, the adiabatic temperature and its longitudinal profile along a reactor for the CSPOM has been developed, in f order to design a 5 Nm3 syngas/h reactor, and thereafter to scale-up towards larger units of a size typically needed to supply gases to a 50-200 kW Fuel Cell Power Plant The model allows sensitivity studies to be performed for a variety of reactor designs in the capacity range of 1-200 Nm3 syngas/h or so. These sensitivity analyses have two significant design implications: (i) to provide the reactants and products composition profile in the catalytic bed and (ii) to provide the operating conditions

(preheating temperature, pressure, GHSV, catalyst particle size, air/methane ratio, inert/catalyst ratio, etc.). Thereafter the optimal reactor configuration, to assure quasi-isothermal conditions, higher methane conversion and H, and CO selectivities, may be consequently individualised.

The proposed approximate version of the model provides useful information in this regard; the complete model takes radial effects into account and better fits the experimental values.

[1] E.Singer and RH. Wilhelm, Ind.Eng.Chem., 46 (1950), 343.

[2] K.Hashimoto, N.Taneda, Y.Horiguchi and S.Nagata, J.ResJnst.Catalysis, Hokkaido Univ., (1968), 541-563.

[3] W.B.Argo and J.MSmith, Chem.Eng.Progr., 50, No.10 (1954), 504-510.

[4] A.K.Bhattacharya, J.A.Breach, S.Chand, D.K.Ghorai, AJHartridge, J.Keary and K.K.Mallick, Applied Catalysis A: General, 80 (1992), LI.

[5] O.A.Hougen and K.M.Watson, Chemical Process Principles. John Wiley & Sons Ed., New York, 1957.

[6] P.B.Weisz, Z.Physik.Chem., Neve Folge, II, 1-15, 1957.

[7] W.J.M.Vermeiren, E.Blomsma and P.A.Jacobs, Catalysis Today, 13 (1992), 427-436.

[8] J.K.Hockmuth, Applied Catalysis B: Environmental, 1 (1992), 89-100.

[9] H.Vershoor and G.C.A.Schuit, Appl.Scientific Research 42, A2, No.2, (1950), 97.

References

OPERATION OF THE 25 kW NASA LEWIS SOLAR REGENERATIVE FUEL CELL TESTBED FACILITY

G. E. Voecks. N. K. Rohatgi, S. H. Moore, D. L. Jan. and N. W. Ferraro Jet Propulsion Laboratory 4800 Oak Grove Dr. Pasadena, CA 91109 M. Warshay and P. R. Prokopius (Consultant) NASA Lewis Research Center 28000 Brookpark Road

Cleveland, OH H. S. Edwards, G. Smith Naval Air Weapons Center China Lake, CA 93555

Assembly of the NASA Lewis Research Center Solar Regenerative Fuel Cell Testbed Facility has recently been completed and system testing is in progress. This facility includes the integration of 50 kW photovoltaic solar cell arrays, a 25 kW proton exchange membrane (PEM) electrolysis unit, four 5 kW PEM fuel cells, high pressure hydrogen and oxygen storage vessels, high purity water storage containers, and computer monitoring, control and data acquisition. The purpose of this facility is multi-faceted, but was originally intended to serve as a testbed for evaluating a closed-loop powerplant for future NASA extended life support operations, such as a Lunar outpost, and also as a terrestrial powerplant example for remote or continuous back-up support operations. The fuel cell and electrolyzer subsystems' design and assembly were conducted by the Jet Propulsion Laboratory (JPL), the photovoltaic arrays and electrical interconnect to the electrolyzer were provided by the U. S. Navy/China Lake Naval Weapons Center, and testing and operations are being carried out by JPL.

This testbed facility allows for separate operation of each subsystem, i.e., photovoltaic arrays, electrolyzer, fuel cells, support equipment, as well as integrated operation to simulate expected electrical demand profiles. During the course of operations, many important technical points have been learned. The interconnect between the photovoltaic arrays and the PEM electrolyzer, which can deliver both hydrogen and oxygen at nearly 20,600 kPa (3000 psi), has been designed to allow operation of the electrolyzer (1) separately from the grid, (2) entirely from the photovoltaic arrays, or (3) from the grid in a back-up mode. The four fuel cells have been connected in such a manner that they may be operated separately or combined to evaluate their performance coincidentally with duty cycles commensurate with different demands to reflect NASA requirements for isolated operations. All the operating data and energy and mass balances are being performed in order to determine where system and subsystems inefficiencies exist, what technical improvements are most important, and how such a system can best be integrated for future NASA missions where thermal and electrical energy conservation are ofextreme importance.

From operating data and experience, control strategies and equipment design will be determined that will enable automated operation, a key goal for both NASA and terrestrial users. Start up, shut down, and load following to efficiently meet prescribed duty cycles impact the choice of equipment and the system design as well as the control strategy.

The system description and performance data constitute Phase I of multiple activities planned to take place in the next few years. System modeling is being performed in parallel with the experimental testing and will be used to determine the most efficient system design, from the standpoint of weight, volume and cost of electrical power.

In addition to detailed facility and system layout and operations, performance data, mass and energy determinations and modeling analyses will be presented to illustrate the capabilities of the testbed facility and basis for advanced designs.

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