CA1144229A - Fuel cell thermal control and reforming of process gas hydrocarbons - Google Patents

Abstract

Abstract Thermal control and fuel processing in fuel cell opera-tion is effected through sensible heat of process gas and hydro-carbon reforming by supplying process gas in common to a flow pas-sage in communication with the cell electrolyte and an additional gas flow passage which is isolated from the cell electrolyte and includes catalyst promoting endothermic reforming of hydrocarbon content of the process gas. Flow level in the electrolyte-communication flow passage is selected based on desired output electrical energy and flow level in the additional gas flow pas-sage is selected in accordance with desired cell operating tempera-ture and desired extent of fuel processing.

Description

1~44;~29 This invention relates to fuel cells wherein reactant or product gas is conducted to or from the cells.
The invention relates more particularly to thermal control and fuel processing in such cells.
In the design of fuel cells and like electrical energy producing devices involving reactant or product gas undergoing electrochemical reaction (process gas), thermal control is a dominant parameter. The electrochemical reactions in such devices are invariably accompanied by heat generation or heat absorption because of entropy changes accompanying the reation and irreversibilities caused by diffusion and activation overpotentials and ohmic resistance. In the accomodation of thermal control, the art has looked to various techniques, none of which are entirely satisfactory.
The thermal control technique seemingly most desirable takes advantage of the sensible heat of the process gas itself as a vehicle for thermal control. Thus, if removal of heat from the cell is desired, the incoming process gas may be supplied to the cell at a temperature lower than the cell operating temperature such that exiting gas removes heat simply by increase in temperature thereof in passage through the cell. In this technique, one adjusts the process gas flow level above the flow level required for production of preselected measure of electrical energy, such additional process gas serving the heat removal function. Disadvantages attending this practice include undesirable pressure drops based on the increased process gas flow, auxiliary power penalty and loss of electrolyte through vaporization or entrainment. By auxiliary power is meant the power requirements of apparatus accessory to the *

~42Z9 fuel cell proper, e.g., gas pumps, pressurizing systems and the like. As respects electrolyte loss, all process gas in this gas sensible heat technique is in communication with the cell electrolyte in its passage through the cell and, where substantial additional gas is required for thermal control, a very high electrolyte loss due to saturating of the gas with electrolyte vapor is observed in electrolyte gas resulting in quite high electrolyte loss.
In a second thermal control technique, the art has looked to limiting the temperature gradients inside fuel cells by employment of a bipolar plate having an extended fin dis-posed outside the cell proper, as shown in u.S. patent No.
3,623,913 to Adlhart et al. While this technique provides a somewhat more uniform cell temperature, high gas flow passing directly through the cell can result in high electrolyte loss and increased auxiliary power.
A third thermal control technique relies on the sensible heat of a dielectric liquid. Such sensible-like liquid approach requires much lower auxiliary power as com-20 pared to the gaseous heat transfer medium, but requires a separate heat transfer loop and an electrically isolated mani-folding system. To avoid shunt currents between stacked cells, dielectric fluids such as fluorocarbon or silicon-based oils have ~een traditionally used as the heat transfer media. Be-cause the catalyst material may by poisoned severely by even a trace amount of these dielectric fluids, a small leak from the heat transfer loop may be fatal to the cell. Also, the dielectric liquids are flammable and have toxic reaction products.
In a fourth technique for thermal control, the art - 1~442Z9 has relied on the latent heat o~ liquids. Latent heat liquids (U.S. patents Nos. 3,498,844 and 3,507,702 to Sanderson; U.S.
patent No. 3,761,316 to Stedman; and U.S. patent No. 3,969,145 to Grevstad et al.) can provide at heat transfer at nearly uniform temperature, although there may be some temperature gradients in the stacking direction if the heat transfer plate is placed between a group of cells. The auxiliary power re-quirements are expected to be extremely low. Suitable di-electric fluids having boiling points in the range of cell operating temperature can be used, but the disadvantages of the sensible-heat liquid approach apply here also. To over-come these disadvantages, non-dielectric media, such as water, can be used. If water is used, a suitable quality steam can be generated for use in other parts of the plant. External heat exchange also is expected to be efficient because of high heat transfer coefficients. Unfortunately, the use of a non-dielectric liquid necessitates elaborate corrosion protection schemes ~U.S. patent No. 3,969,145 to Grevstand et al.; U.S. patent No.
3,923,546 to Katz et al.; U.S. patent No. 3,940,285 to Nickols et al.) and/or the use of an extremely low conductivity liquid During operation, the conductivity may increase, so means to restore the low conductivity may also be required. If the cooling loop is under pressure, good seals are necessary. If a leak develops during the life of the stack because of pin-holes caused by corrosion or deterioration of seals, it could paralyze the entire system. Because of the corrosion protec-tion requirements and intricate manifolding, the cost of the heat transfer subsystem operating on dielectric coolant could be substantial.
In a first U.S. patent No. 4,192,906 of July 9, T .

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~144Z~:9 1979, commonly-assigne~ herewith, a fundamentally different approach to thermal control of fuel cells is set forth which provides for supplementing the flow of process gas through an electrochemical cell, in measure required for thermal control by sensible heat of process gas, in manner both avoiding electrolyte loss and pressure drop increase across the cell. In implementing this process gas sensible-heat technique, the invention of such commonly-assigned application introduces, in addition to the customary process gas passage in communication with the cell electrolyte, a process gas passage in the cell which is isolated from the cell electrolyte and in thermal communication with a heat-generating surface of the cell. Such electrolyte-communicative and electrolyte-isolated passages are commonly manifolded to a pressurized supply of process gas~ The flow levels in the respective passages are set individually by passage parameters to provide both for desired level electrical energy cell output and desired heat removal.
In a second U.S. patent No. 4,169,917 of October

2, 1979, also commonly-assigned herewith, electrochemical cell structure is set forth for im-plementing the thermal control technique of said first U.S.
patent herein such electrolyte-isolated passages are so arranged as to have gas-confining walls contiguous with the electrode served with process gas by the electrolyte-commur cative passages. Integral sheet material is preferably corruge to define channels opening into the electrode and successive alternate channels closed from the electrode by the sheet material.
Apart from the foregoing thermal control techniques, 2Z~

applicants herein have considered the desirability of so-called "reforming" of hydrocarbon content of process gas. Fuel cell gas streams frequently contain methane and other hydrocarbons.
The heat value, and hence electrical energy producing potential of methane is about three to four times greater than that of hydrogen. Since methance itself is relatively electrochemically inactive, it is very desirable to reform methane to form hydro-gen and carbon monoxide in accordance with the reaction: CH4 + H20 3H + CO. The hydrogen and carbon monoxide can then participate in the fuel cell reaction either directly or by further water-gas shift. An incentive for carrying out such reforming reaction in a fuel cell is that the reaction is endothermic and would serve to offset heat generated in fuel cell operation due to inherent irreversibility. Accordingly, internal reforming of fuel can reduce the load on the fuel cell cooling system. Instroduction of a reforming catalyst in the path of reactive process gas would serve to realize the fore-going advantages. However, since the reforming reac'ion is endothermic, it creates cold spots for the electrolyte vapor to condense and, in turn, catalyst activity in promoting reforming would be substantially reduced.
It is an object of the present invention to provide for efficient use of hydrocarbon reforming in the thermal control of fuel cells.
It is a further object of the inven~ion to provide for in situ hydrocarbon reforming in fuel cells in manner preventing catalyst deactivation by condensation of fuel cell electrolyte vapor.
In attaining the foregoing and other objects, the in-vention provides thermal control in an electrochemical cell jointly through sensible heat of process gas and hydrocarbonreforming by conducting process gas through a passage formed in or juxtaposition with the cell which is isolated from the cell electrolyte and which includes catalyst promotive of re-forming process gas hydrocarbon content. Other customary passage in communication with the electrolyte is provided in the cell and supplied with process gas for reaction purposes.
Output gas from both passages is cooled prior to recirculation through the cell, with the gas exiting from the reforming pas-sage being subjected to treatment removing substance therefrom(e.g. condensing the carbonates vapor) which retards promotive reforming activity of the catalyst.
In series cell application, the invention conveys the products of hydrocarbon reforming in a prior cell to a subseq-uent cell for entry thereof into process gas reaction producing electrical energy.
The foregoing and other objects and features of the invention will be further understood from the following detailed discussion thereof and from the drawings wherein like reference numerals identify like parts throughout.
Fig. 1 is a sectional drawing of an explanatory em-bodiment of an electrochemical cell in accordance with the invention, as seen along plane I-I of Fig. 2.
Fig. 2 is a plan elevation of the Fig. 1 fuel cell, shown together with accessory process gas supply and treatment apparatus.
Fig. 3 is a sectional view of the Fig. 1 fuel cell, as seen along plane iII_III of Fig. 1.
Fig. 4 is perspective illustrations of fuel cell stacks in accordance with the invention.

~44229 Fig. 5, sheet 2, is a sectional drawing of a further explanatory embodiment of an electrochemical cell in accordance with the invention, as seen from plane VI-VI of Fig. 6.
Fig. 6, sheet 2, is a side elevation of the Fig. 5 cell.
Fig. 7 is a perspective showing of the separator plate employed in the cell of Figs. 5 and 6.
Figs. 8 and 9 are perspective showings of bipolar separator plates for practicing the invention.
Fig. 10 is a sectional drawing of a fuel cell stack in accordance with the invention.
Fig. 11 (a)-(d) are schematic showings of other em-bodiments of separator plates for practicing the invention.
In Figs. l and 3, fuel cell 10 includes anode and cathode electrodes 12 and 14, of customary gas diffusion type, and electrolyte matrix or layer 16 therebetween. Separator plates 18 and 20 are shown in the explanatory Fig. 1 single cell embodiment as being of unipolar character, defining channel pas-sages 18a, for supplying fuel/process gas to anode electrode 1 and passaqes 20a, for supplying oxidant/process gas to cathode electrode 14. Based on the gas diffusion character of electrodes 12 and 14, passages 18a and 20a constitute elctrolyte-communi-cative passages.
In accordance with the invention, thermal control plate 22, having reforming catalyst layers or packings 23, is stacked on separator plate 18. Plate 22 includes conduit passage 22a extending in like direction, i.e., across the plane of Fig. 1, with passages 18a and is commonly connected therewith by input anode gas manifold ~6 and output anode gas manifold 28.
Thermal control plate 24, constructed as in the first mentioned U.S. patent 4,192,906 above, includes conduit passage 24a 5,,, ,,~
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-11i4~Z9 , not containing catalyst and extending in like direction, i.e., into the plane of Fig. l, with passages 20a and is commonly con-nected therewith by input cathode gas manifold 30 (Fig. 2) and output cathode gas manifold 32. Since separator plates 18 and 20 are essentially gas-impermeable, thermal control plate pas-sages 22a and 24a constitute electrolyte-isolated passages. Thus, process gases, i.e., fuel gas supplied from manifold 26 and oxidant gas supplied from manifold 30, present in passages 22a and 24a can be conducted through the fuel cell to serve thermal control purposes and, in the case of reforming passage 22a, with-out contributing to el!ectrolyte loss and without resulting in electrolyte blockage due to condensation of electrolyte vapor on cold spots resulting from the endothermic reforming reaction in the fuel gas passage. To the contrary, process gases conducted through channels 18a and 20a give rise to exit gas unavoidably partially or fully saturated with electrolyte vapor. If catalyst is applied in channels 18a, reforming cold spots can result therein, as above discussed.
As is noted below fuel cells may employ thermal control plates for one or the other of the process gases. Where desired, exit admixing of process gas conducted through electrolyte-communicative and electrlyte-isolated passages may be dispens~d with in favor of common manifolding solely of input process gas supplied to such diverse character passages. Also, as discussed below, the present invention contemplates the introduction of electrolyte-isolated, catalyst-containing process gas passages, commonly input manifolded with a process gas supply, individually per plural cells in a stack of fuel cells.
Referring again to Fig. 2, input anode gas manifold 26 is supplied through feed conduit 34, which is in turn fed from pressurized input anode gaq supply 36. Process gas from supply 36 may be admixed with, and thus supplemented by, process gas theretofore conducted through the fuel cell. For this purpose, output gas fxom manifold 28 is conducted through conduit 38 to unit 40, which serves both heat exchange and the removal of catalyst-contaminating substances, and thence to a mixing valve in supply 36. By operation of valve 42, gas may be funneled to purge conduit 44, as desired. To remove heat from gas cond-ucted through conduit 38 prior to recirculation, as is typical, unit 40 is of heat reducing type whereby gas supplied from unit 40 to supply 36 is of temperature lower than the cell oper-ating temperature.
For thermal treatment, purging and recirculation of cathode process gas, counterpart components include feed conduit 46, pressurized input cathode gase supply 48, input gas conduit 50, purge valve 52, purge conduit 54 and unit 46, which corres-ponds to unit 40 in terms of cooling the process gas.
In implementation of methods of the invention, process gas flow is established at a level or levls, as respects elec-trolyte-communicative passages 18a and/or 20a, tc attain pre-determined electrical energy to be produced by the electrochem-ical cell. Even assuming reversibility of electrochemical rea-ctions in fuel cells, a recognized minimum amount of heat is liberated. Also, as alluded to above, irreversibility in fuel cells, resultant from activation, concentration and ohmic over-potentials, results in additional heat generation. Typically, in fuel cells, about fifty per cent of input enthalpy shows up as heat and the remainder as such predetermined electrical energy.
The heat energy may be ascribed as about one-fifth reversible heat and four-fifths heat due to irreversibility.

1~44229 With process gas flow in passages 18a and 20a set in accordance with such predetermined desired electrical energy cell output, process gas flow in electrolyte-isolated passages, 22a and/or 24a, and catalyst content of passages 22a are now set to obtain a predetermined operating temperature range for the electrochemical cell. No completely analytical procedure applies, since input and exit orifice geometry, conduit sknin friction, conduit length, manifold geometries and catalyst packing demand empirical test. The practice of achieving desired flows in the respective passages may include the placement of fixed or variably-settable constrictions in either or both passages.
Referring to Fig. 4, a preferred embodiment of cell stack 56 is shown without assiciated electrical output connect-ions and encasements. Electrolyte layers and gas diffusion anodes and cathodes are identified jointly as cell assemblies 58a-58j.
The top separator plate 60 is of unipolar type habing electrolyte-communicative channel passages 60a, as in the case of separator plate 18 of Fig. 1, and overlies the anode of top cell assembly 58a. Separator plate 62 is of biopolar type, defining electro-lyte-communicative channel passages 62a, which underlie the cathode of top cell assembly 58a, and 62b which overlie the anode of second cell assembly 58b. Bipolar plates 64,66 and 68 separ-ate cell assemblies 58b, 58c and 58d, with plate 68 gas passages 68b overlying the anode of cell assembly 58e. Separator plate 70 is of unipolar type, having passages 70a underlying the cathode of cell assembly 58e. A sub-stack of five fuel cells is thus provided. Thermal control plate 72 is diposed beneath such sub-stack with its catalyst-containing conduit passage 72a in communication with heat-generating surface of the sub-stack ~M2Z~3 namely, the undersuface of separator plate 70. A like sub-stack of five fuel cells, inclusive of cell assemblies 58f-~8j, is disposed beneath plate 72. Unipolar separator plates 74 and 76 are endwise of the sub-stack and bipolar separator plates 78, 80 and 82 are intermediate the sub-stack. Thermal control plate 84 is arranged with its catalyst-containing conduit passage 84a in communication with the under-surface of separator plate 76.
Input anode and cathode gas manifolds 86 and 88 are shown schematically and separated from stack 56. Based on the inclusion of thermal control plates 70 and 84 with anode gas con-duit passages 72a and 84a, manifold 86 supplies process gas com-monly to and through electrolyte-communicative and electrolyte-isolated, catalyst-containing passages. Cathode oxidant flow from manifold 88 is limited to electorlyte-communlcative passages in this showing. In the illustrated arrangement, one electrolyte-isolated, catalyst-containing passage is associated with each sub-stack of five fuel cells. Where a thermal control plate is located between sub-stacks, as in the case of plate 72, it will serve to cool both such sub-stacks. Other assignment of thermal control plates per fuel cells may be made as desired. Stiffening elements 73 may be introduced in plate 72, as shown in Fig. 4, to strengthen the stack and increase heat transfer surface area.
Such members are desirably electrically conductive to further enhance electrical current passage through plate 72.
The thermal control method and arrangement of the in-vention will be seen to provide several important benefits. Heat transfer is accomplished through sensible heat of process gas and hydrocarbon reforming by using an additional flow of process gas without requiring any separate manifolding system, as is necessary in case of liquid heat transfer medium. Possibility -li44~

of corrosion by shunt currents and any harmful effects by leakage are completely eliminated. The system reliability is, therefore much greater than that for liquid heat transfer media. The elec-trolyte losses by carry-over or vaporization to the process gases are minimized because only a limited amount of process gases contact the electrolyte. Process gases passing through the thermal control plates do not contact the electrolyte, so vapor losses due to flow of heat transfer gases are absent. Electro-lyte blockage is averted since all catalyst-promoted reforming takes place in an electrolyte-isolated environment. The thermal control plates can serve as stiffening members, providing addi-tional strength to the stack assembly. Further, if it is re-quired to replace some defective cells during operation, a group of cells between two thermal control plates can easily be removed and new cells can be replaced.
The invention is particularly adapted for use in molten carbonate fuel cells wherein the process gas used also in thermal control is air/carbon dioxide cathode gas mixture and~or hydrogen-rich anode gas mixture containing hydrocarbons and water. Where the hydrocarbon content is methane, a suitable steam-reforming catalyst is nickel or nickel based. A commercially available ver-sion of such catalyst is *Girdler G-56 and is provided in pellet form for packing in fixed bed type reactors. Suitable nickel catalyst for this purpose and method for making the same is fur-ther set forth in U.S. patent No. 3,488,266, in which hydrocarbon reforming is carried out in heat exchange relationship to a fuel cell, however in electrolyte-communicative environment.
Various changes in the methods of operation and in the illustrated systems of Figs. 1-4 may be introduced. By way of example, one may elect to supplement process gas furnished by *Trademark . . , ~

supply 36 and/or supply 48 (Fig. l) solely with process gas con-ducted through electrolyte-isolated passages, rather than the des-cribed admixture of gases conducted through both electrolyte-communicative and electrolyte-isolated passages. To implement this variation, cell output gases are not manifolded but, rather, are separately issued with the issuance of the electrolyte-iso-lated passage being placed in communication with the input mani-fold serving both types of passages.
In cascade arrangement of cells constructed as above discussed, the reforming passage gas exiting the first of the series of cells may be supplied to the reaction passage of the second cell. In turn, the reforming passage gas exiting such second cell may be furnished to the reaction passage of the third cell, etc. Gas exiting the reaction passage of such first cell may be admixed with gas exiting the reforming passage, as shown in Figs. 1-3, or may be separately conducted to the reforming pas-sage of the second cell, etc. Fresh fuel supplied to the first cell may be introduced in any passage in subsequent cells. This method of cascading has the advantage of using product water from previous cells to enhance the steam-reforming of the hydrocarbons.
This is particulary important when the entire system is pressuri-zed and the resulting equilibrium favors the formation of hydro-carbons, particularly methane. Another advantage of such cascad-ing is to maintain a higher partial pressure of hydrogen in the fuel cell, thereby allowing more reversible operation.
Referring to Figs. 5 and 6, fuel cell llO includes anode and cathode electrodes 114 and 112, of gas diffusion type, and electrolyte matrix or layer 116 therebetween. Separator plate 118 is of design having channel passages 118a, for supply-ing process gas to cathode electrode 112. Separator plate 120 is ~4ZZ9 constructed to implement this alternate embodiment of the inven-tion and, as shown in explanatory Fig. 5 single cell embodiment is of unipolar character, defining channel passages 120a, for supplying fuel gas to anode electrode 114. sased on the gas diffusion character of electrodes 112 and 114, passages 118a and 120a constitute electrolyte communicative passages.
Passages 120b of separator plate 120 are in flow iso-lation with respect to anode electrode 114, the boundary walls 120c, 120d and 120e of the passages being essentially impermeable to gas and having catalyst coating 121. Wall 120d is contguous with electrode 114. Plate 120f is juxtaposed with passages 120b to close the same. Accordingly, passages 120b are in flow isola-tion with respect to electrolyte 116, and process gas supplied to passages 120b can be conducted through the fuel cell to serve thermal control purposes, by hydrocarbon reforming and sensible heat, without contributing to electrlyte loss or blockage. To the contrary, process gases conducted through passages 118a and 120a give rise to exit gas unavoidably partially saturated with elec-trolyte vapor. In the illustrated embodiment, passages 120a and 120b are alternately successive in a common plate location as one progresses across that surface of electrode 114 which is contig-uous with the crests 120d of electrolyte-isolated catalyst-con-taining passage 120b.
In the systems of Figs. 1-4, unipolar separator plates, such as plate 18 are used adjacent each of the cell electrodes of a fuel cell. Supplemental process gas to be conducted through electrolyte-isolated passages for thermal control is fed through conduits of further plates which are spaced from the electrodes by the unipolar separator plates. Such conduit-defining further plates are employed in one cell in a succession of cells forming ~442Z9 a stack. Since heat removal thus is affected by endothermic re-forming reaction and sensible heat of supplemental process gas at somewhat spaced sites, the possibility exists for thermal gradients to be present in substantial measure. Such disadvantage is overcome in the embodiments of Figs. 5-11, wherein thermal gradients are reduced since heat removal may be accomplished, as desired, from heat-generating surface of each cell.
The unipolar embodiment of separator plate 120 is read-ily formed by the use of integral sheet material and corrugation of same to form channels defining the respectively diverse pas-sages. While the channels are shown as symmetric in Figs. 5-7, they can be preselected to have different cross-sectional areas in accordance with the ratio of flows therethrough needed to achieve intended heat removal and electrical energy output. The practice of achieving desired flows in the respective passages may include variation of siae and geometry of the flow passages and/or the placement of fixed or variably-settable constrictions in either or both passages. As is shown by way of example in Fig.
7, a partial end wall 120g may be formed in channel 120a, or block type obstacle 122 may be included therein.
Referring to Figs. 8 and 9, bipolar plates are shown for implementing the invention. In Fig. 8, bipolar plate 124 includes a corrugated sheet member 126 disposed atop a plate 128 which defines channel passages 128a for process gas. Member 126 has passages 126a (electrolyte-communicative) and 126b (electrolyte-isolated and catalyst-containing).
In bipolar plate 130 of Fig. 9, backing plate 132 sup-ports corrugated sheet members 134 and 136 and closes the elec-trolyte-isolated passages 134b and 136b thereof. Crisscross 30 electrolyte-communicative passages 134a and 136a serve electrodes ~14~

juxtaposed therewith (not shown) with process gases. Such Fig. 8 plate is shown in stack usage in the fuel cell stack of Fig. 10.
As the hydrocarbon content of the process gas increases, the in situ reforming predominates the thermal balance in the sys-tem and the benefits of higher thermal efficiency of system oper-ation accrue.
The invention will be recognized as providing a highly efficient vehicle for reforming of process gas, separate and apart from thermal control.
As will be appreciated, various changes may be intro-duced in the foregoing embodiments without departing from the in-vention. Thus, passage geometry may be varied extensively, as is shown by corrugated sheet members 138-144 illustrated sche-matically in Figs. 11 (a)-(d). The particularly disclosed embodi-ments and practices are thus intended in an illustrative and not in a limiting sense. The true spirit and scope of the invention is set forth in the following claims9

Claims (30)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for operating an electrochemical cell to produce electrical energy from electrochemical reaction between a cell electrolyte and a gas containing a hydrocarbon supplied from a gas supply to a flow passage in said cell in flow communication with said electrolyte, including the steps of:
(a) establishing a further flow passage for gas from said supply through said cell isolated from said electrolyte and in thermal communication with a heat-generating surface of said cell, (b) disposing catalyst promoting endothermic reforming of such hydrocarbon content of said gas in such electrolyte-isolated passage, and (c) conducting gas from said supply through both such electrolyte-communicative passage and said electrolyte-isolated passage.

2. The method claimed in claim 1 wherein gas conducted through said electrolyte-communicative passage and through said electrolyte-isolated passage is commonly admixed after conductance thereof through said cell.

3. The method claimed in claim 2 including the further step of employing at least part of such common admixture of gas for further supplying of gas to said electrolyte-communicative passage and said electrolyte-isolated passage.

4. The method claimed in claim 3 including the further step of subjecting said common admixture of gas to thermal change prior to such further supplying thereof.

5. The method claimed in claim 4 wherein such thermal change step involves reduction of temperature of said common admixture of gas.

6. The method claimed in claim 1 including the further step of employing at least part of such gas conducted through said electrolyte-isolated passage for further supplying of gas to said electrolyte-communicative passage and said electrolyte-isolated passage.

7. The method claimed in claim 6 including the further step of subjecting such gas part to thermal change prior to such further supplying thereof.

8. The method claimed in claim 7 wherein such thermal change step involves reduction of temperature of said gas part.

9. The method claimed in claim 3 including the further step of removing substance retarding promotive reforming activity of said catalyst from said common admixture of gas prior to said further supplying thereof.

10. The method claimed in claim 6 including the further step of removing substance retarding promotive reforming activity of said catalyst from such gas part prior to said further supplying thereof.

11. The method claimed in claim 1 wherein gas flow level through said cell for gas conducted through such electrolyte-communicative passage is set in accordance with predetermined electrical energy to be produced by said cell and wherein gas flow level through said cell for gas conducted through said electrolyte-isolated passage is set to obtain a predetermined operating temperature range for said cell;

12. An electrochemical cell operative to produce out-put electrical energy by electrochemical reaction with a process gas containing a hydrocarbon, comprising an elec-trolyte layer, a gas diffusion electrode, first passage means in said cell for conducting gaseous medium to said gas diffusion electrode for reaction with said electrolyte, second passage means in said cell for conducting gaseous medium through said cell both in isolation from said electrolyte and in thermal communication with a heat-generating surface of said cell, said second passage means including catalyst promotive of endothermic reforming of such hydrocarbon content of said process gas, and input manifold means in communication with both said first and second passage means for supplying said process gas thereto.

13. The system claimed in claim 13 further including output manifold means in communication with both said first and second passage means for admixing gas conducted there-through.

14. The system claimed in claim 13 including conduit means for providing communication between said output manifold means and said input manifold means.

15. The system claimed in claim 14 further including means for affecting thermal change in gas conducted through said output manifold means.

16. A system comprising the cell claimed in claim 12 and output conduit means in communication with said second passage means for receiving gas conducted therethrough.

17. The system claimed in claim 16 including further conduit means for providing communication between said output conduit means and said input manifold means.

18. The system claimed in claim 17 further including means for affecting thermal change in gas conducted through said output conduit means.

19. The system claimed in claim 15 wherein such thermal change affecting means comprises heat removal means.

20. The system claimed in claim 18 wherein such thermal change affecting means comprises heat removal means.

21. The system claimed in claim 14 further including means for removing substance retarding promotive reforming activity of said catalyst from gas conducted through said output manifold means.

22. The system claimed in claim 17 further including means for removing substance retarding promotive reforming activity of said catalyst from gas conducted through said output conduit means.

23. The cell claimed in claim 12 wherein said second passage means has a surface thereof contiguous with said electrolyte layer.

24. The cell claimed in claim 23 wherein such first and second flow passage means comprise respective pluralities of first and second flow passages, such first flow passages being separated from one another by such second flow passages alternately progressively across a surface of said electrode with which said second flow passages have such contiguous surface.

25. The cell claimed in claim 24 wherein integral sheet material defines both said first and second flow passages.

26. The cell claimed in claim 25 wherein a corrugated sheet member defines first channels open with respect to said electrode and juxtaposed therewith to constitute said first flow passages and defines second channels successive to said first channels having crests continguous with said electrode to constitute said second flow passages.

27. The cell claimed in claim 26 further including a plate member contiguous with the crests of said first channels and serving to close said channels along the length thereof.

28. The method claimed in claim 1 including the further steps of operating a second such electrochemical cell by repeating said steps (a) and (b) for said second cell and by conducting gas exiting said electrolyte-isolated passage of said first-mentioned cell to the electrolyte-communicative passage of said second cell.

29. The method claimed in claim 28 including further step of conducting gas exiting said electrolyte-communicative passage of said first-mentioned cell to said electrolyte-communicative passage of said second cell.

30. The method claimed in claim 28 including the further step of conducting gas exiting said electrolyte-communicative passage of said first-mentioned cell to the electrolyte-isolated passage of said second cell.