United Technologies Corporation

International Fuel Cells, LLC

Other

Harold R Kunz

Richard A Sederquist

Gary A Gruver

Ole L Olesen

Richard D Breault

Carl Anthony Reiser

Francis J Luczak

Murray Katz

Calvin L Bushnell

Paul J Damiano

Stephen J Szymanski

During operation of a fuel cell stack, electrolyte within individual fuel cells migrates between the cathode side and the anode side, and across the separator plate between the cathode side and the anode side electrolyte reservoir plate of a second cell. An electrochemical sensor comprised of wires, a sheath, and a porous conduit having a pore size distribution which is similar to that of the electrolyte reservoir plate in which the electrochemical sensor is located, is capable of determining the electrolyte content during fuel cell operation by measuring the electrical resistance between the wires. The conduit wicks electrolyte into its pores to a content similar to that of the electrolyte reservoir plate. This electrolyte establishes electrical contact between the wires such that the measure of the electrical resistance between the wires is related to the electrolyte content of the electrolyte reservoir plate.

Electrochemical sensor for monitoring electrolyte content

Sulfur compounds poison catalysts, such as the anode catalysts and reformer catalysts within molten carbonate fuel cell systems. This poisoning is eliminated using a sulfur scrubber 29 located prior to the inlet of the cathode chamber 13. Anode exhaust 19 which contains water, carbon dioxide and possibly sulfur impurities, is combined with a cathode exhaust recycle stream 22 and an oxidant stream 25 and burned in a burner 33 to produce water, carbon dioxide. If sulfur compounds are present in either the anode exhaust, cathode exhaust stream, or oxidant stream, sulfur trioxide and sulfur dioxide are produced. The combined oxidant-combustion stream 27 from the burner 33 is then directed through a sulfur scrubber 29 prior to entering the cathode chamber 13. The sulfur scrubber 29 absorbs sulfur compounds from the combined oxidant-combustion stream 27. Removal of the sulfur compounds at this point prevents concentration of the sulfur in the molten carbonate fuel cell system. Therefore, neither the reformer catalysts nor the anode 17 experience sulfur poisoning.

Molten carbonate fuel cell sulfur scrubber and method using same

An electrochemical sensor comprised of wires, a sheath, and a conduit can be utilized to monitor fuel cell component electric potentials during fuel cell shut down or steady state. The electrochemical sensor contacts an electrolyte reservoir plate such that the conduit wicks electrolyte through capillary action to the wires to provide water necessary for the electrolysis reaction which occurs thereon. A voltage is applied across the wires of the electrochemical sensor until hydrogen evolution occurs at the surface of one of the wires, thereby forming a hydrogen reference electrode. The voltage of the fuel cell component is then determined with relation to the hydrogen reference electrode.

Electrochemical sensor for monitoring electrochemical potentials of fuel

Sulfur compounds poison catalysts, such as the anode catalysts and reformer catalysts within molten carbonate fuel cell systems. This poisoning is eliminated using a sulfur scrubber 29 located prior to the inlet of the cathode chamber 13. Anode exhaust 19 which contains water, carbon dioxide and possibly sulfur impurities, is combined with a cathode exhaust recycle stream 22 and an oxidant stream 25 and burned in a burner 33 to produce water, carbon dioxide. If sulfur compounds are present in either the anode exhaust, cathode exhaust stream, or oxidant stream, sulfur trioxide and sulfur dioxide are produced. The combined oxidant-combustion stream 27 from the burner 33 is then directed through a sulfur scrubber 29 prior to entering the cathode chamber 13. The sulfur scrubber 29 absorbs sulfur compounds from the combined oxidant-combustion stream 27. Removal of the sulfur compounds at this point prevents concentration of the sulfur in the molten carbonate fuel cell system. Therefore, neither the reformer catalyst nor the anode 17 experience sulfur poisoning.

Molten carbonate fuel cell sulfur scrubber

Carbon monoxide poisoning of anode catalysts in phosphoric acid fuel cells reduces the cell performance. The carbon monoxide absorbs onto the catalyst, blocking hydrogen oxidation sites. A carbon monoxide tolerant platinum-tantalum alloyed catalyst includes between about 2 wt % and about 50 wt % platinum, between about 2 atom % and 10 atom % tantalum deposited on a support. This catalyst is particularly useful in fuel cell system applications where the fuel stream may contain carbon monoxide.

Carbon monoxide tolerant platinum-tantalum alloyed catalyst

A fuel cell is cooled by circulating a stream through the cell, the stream containing a reactive material which undergoes an endothermic reaction within the fuel cell, absorbing waste heat. The material, upon leaving the fuel cell, passes through a regenerative heat exchanger where heat is removed. The reacted material then undergoes an exothermic reaction, releasing the waste heat absorbed within the fuel cell. After the exothermic reaction, the material is returned to the fuel cell to repeat the cooling cycle. Utilizing a reactive cooling system based on the heat of reaction as a means for removing waste heat allows reducing the amount of gases supplied to the fuel cell, thus reducing the size of the internal gas passages and consequently, the overall size of the fuel cell while maintaining a high power output.

Fuel cell cooling using heat of reaction

A composite hydrogen purification membrane comprises an anode for hydrogen oxidation, a cathode for hydrogen reduction, with a proton conductor disposed between and in contact with the anode and the cathode. Electrons are conducted between the anode and cathode through an external connection, with the electron flow generated by the difference in hydrogen partial pressure between the anode and cathode sides of the membrane. Thus the composite hydrogen purification membrane provides high hydrogen permeability and selectivity relative to the impurities in a feed gas, producing pure hydrogen without requiring an external voltage source.

Composite hydrogen purification membrane and method for purifying

A fuel cell or fuel cell stack of the type utilizing a solid polymer electrolyte membrane is cooled by evaporation of water in the hydrogen reactant chamber of the cells. A porous graphite plate or water permeated membrane is disposed in the hydrogen reactant chamber adjacent to the electrolyte membrane. If a graphite plate is used, it is preferably grooved on the surface facing the electrolyte. The resultant lands preferably contact the supported catalyst layer on the membrane to cool the latter. Water is forced into the pores of the plate or membrane from the edge thereof, and the water vapor is carried out of the cells in the hydrogen reactant exhaust stream. A separate cooling system is thus avoided.

Solid polymer electrolyte fuel cell system with porous plate evaporative

Gas depolarized cathodes having hydrophobic barrier layers for circulation electrolyte electrochemical cells; methods of making said cathodes; and methods of electrolyzing solutions of halide containing compounds using said electrodes. Typically, in electrochemical cells cathodes are oriented vertically resulting in significant electrolyte pressure against the cathode. The barrier layer comprising fluorocarbon polymer and carbon results in substantially no electrolyte leakage through the cathode when the electrolyte pressure is up to three pounds per square inch above ambient.

Method of making circulating electrolyte electrochemical cell having gas

Electrolyte lost from a fuel cell, such as by evaporation, is replenished by introducing electrolyte from an external source into a reactant gas stream being delivered into the cell. The fresh electrolyte is vaporized or formed into droplets as it enters the cell such as by spraying the fresh electrolyte into the gas stream. If the electrolyte vapor pressure in the entering gas stream is made high enough, evaporation of the electrolyte from the cell can be halted or electrolyte can even be added to the cell from the gas stream.

Method for replacing lost electrolyte in fuel cells

Molten carbonate fuel cells having anodes, cathodes, and matrices of specific characteristics result in improved cell performance as electrolyte is lost due to evaporation, reaction, etc. The anode has a mean pore diameter less than that of the cathode, a porosity sufficient to contain enough electrolyte to provide for the electrolyte lost, and a ratio of maximum pore diameter at 90% electrolyte fill to maximum pore diameter at 10% electrolyte fill of less than about three. The cathode has a larger mean pore size than that of the anode, a thickness greater than about 0.050 cm, a porosity greater than about 78%, and pore-size distribution such that, when the anode electrolyte content changes from 90% to 10% fill, the cathode electrolyte content changes from about 40% to about 25% fill. In addition, the cathode has about 20% of its pore volumes in pores less than about 0.5.mu. resulting in a surface area of the cathode above about 1 m.sup.2 /g. The matrix has a pore size distribution such that greater than 98% of the matrix is filled with electrolyte when the anode is 10% filled with electrolyte.

Molten carbonate fuel cell with improved electrolyte storage

A binary electrolyte for a molten carbonate fuel cell is disclosed. The electrolyte is approximately 72 m % Li.sub.2 CO.sub.3 and 28 m % K.sub.2 CO.sub.3 and displays a uniform lithium to potassium in molar ratio during operation along the length of the fuel cell stack.

Binary electrolyte for molten carbonate fuel cells

Circulating electrolyte electrochemical cell having gas depolarized

A continuous process of removing ammonia gas from a gas stream is disclosed. A bed of solid porous material is provided which is wetted with an acid and the ammonia gas is removed by reacting with the acid to form an ammoniated salt. The porous material containing the acid is held at an electrochemical potential sufficient to oxidize the ammoniated salt of the acid to produce nitrogen gas regardless of the content of the gas stream. The porous substrate can be flooded with an insulating layer to permit entry of only the formed salt and a barrier to the, for example, reducing gas, thereby improving the efficiency of the system.

Continuous electrochemical ammonia scrubber

An electrolyte reservoir layer disposed behind and adjacent one of the catalyst layers of a fuel cell is porous and hydrophilic to the electrolyte. In one embodiment the reservoir layer includes impregnations of hydrophobic material on the catalyst facing surface thereof and holes leading from the other surface to the impregnations for providing reactant gas passages through the reservoir layer to the catalyst layer. The impregnations of hydrophobic material are designed to provide good distribution of the reactant gas into the catalyst layer without consuming a large volume of the reservoir. In a preferred embodiment the reservoir is also the electrode substrate whereby the catalyst layer is bonded to the surface thereof.

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Vernon, CT, United States of America

Harold R Kunz