KR20060057023A - Electrolyte migration control for large area mcfc stacks - Google Patents

Abstract

The present invention relates to a new strategy against the electrolyte migration through the gasket in externally manifolded MCFC stacks. This is obtained by endowing a stack of molten carbonate fuel cells (MCFCs) of an electrolyte management tool separated from the cells by an electronically conductive material which is impervious to gas, characterised by the combination of the following elements: - a positive reservoir component external to the cathode of the first cell on the positive side of the battery, wherein said reservoir consists of one ore more porous layers of electronically conductive material and comprises at least one gas distributor, and - a negative reservoir component external to the anode of the last cell on the negative side of the battery, wherein said reservoir consists of one ore more porous layers of electronically conductive material.

Description

ELECTROLYTE MIGRATION CONTROL FOR LARGE AREA MCFC STACKS}

The present invention relates to a molten carbonate fuel cell device that achieves active control of electrolyte movement through a gasket in an externally manifolded stack. It is an object of the present invention to provide a large stack (more than 50) of large area (3500 cm ²⁾ The above is to minimize the effect of this effect on the performance when constructed by the battery. Such a strategy does not require modification to a particular cell, but all cells can be made by the same component.

Fuel cells are devices that produce electricity by electrochemical processes using hydrogen (or hydrogen-rich fuel) and oxygen.

A single fuel cell consists of an electrolyte sandwiched between two thin electrodes (porous cathode and anode). Different fuel cell types exist, nevertheless hydrogen or hydrogen-rich fuel is supplied to the cathode and oxygen or air is supplied to the anode.

For example, in the case of a polymer exchange membrane (PEM) and a phosphate fuel cell, protons generated by a cathode reaction move to an anode through an electrolyte and combine with oxygen and electrons to generate water and heat.

In the case of alkaline molten carbonate and solid oxide fuel cells, anions travel through the electrolyte to the cathode where they combine with hydrogen to produce water and electrons. Electrons originating from the negative side of the cell cannot move past the membrane to the positively charged positive electrode; These electrons must travel around the membrane through an electrical circuit to reach the other side of the cell. This movement of the electrons is the current.

Molten Carbonate Fuel Cells (MCFCs) are a class of high temperature fuel cells. Higher operating temperatures allow these cells to directly use natural gas without the need for a fuel processor, and have also been used with low-Btu fuel gases resulting from industrial processing of other sources and fuels. . Such molten carbonate fuel cells were developed in the mid-1960s, and many improvements have been made in manufacturing methods, performance and durability.

MCFCs operate in a very different way from other fuel cells. These cells use an electrolyte consisting of a molten mixture of carbonates. Two kinds of mixtures are currently used: lithium carbonate and potassium carbonate, or lithium carbonate and sodium carbonate. MCFCs operate at high temperatures (650 ° C.) to melt carbonates and achieve high-ion mobility through the electrolyte.

When heated to a temperature of about 650 ° C., these salts melt to become conductive to carbonate ions (C0 ₃ ^{2 −} ). In operation of the cell, these ions are produced by the anodic reaction and flow from the anode to the cathode where they combine with hydrogen to produce water, carbon dioxide and electrons. These electrons are sent back to the anode through an external circuit, producing electricity and heat, a byproduct. The reactions that occur in this process are as follows:

Cathode ^{_{reaction: CO 3 2 - + H 2}} ⇒ H 2 O + CO 2 + 2e -

Anode Reaction: C0 _{2 ^{+ 1/2 O 2 + 2e - ⇒}} CO 3 2 -

Total cell reaction: H ₂ (g) + 1/2 0 ₂ (g) + CO ₂ (anode) ⇒ H ₂ 0 (g) + C0 ₂ (cathode)

The high temperature operating temperatures of MCFCs have both advantages and disadvantages over low temperature PAFCs and PEFCs. At higher operating temperatures, CO acts as a fuel rather than a poison, with extraordinary advantages in terms of both fuel source tolerance and methane reforming. Moreover, with regard to the reforming of natural gas, this advantage can be achieved by directly using the MCFC's waste heat itself as a heat source. An additional advantage is that standard materials such as stainless steel sheets can be used in the fabrication, and the use of nickel-based catalysts on the electrodes is allowed. Heat, a by-product from MCFC, can be used to generate high pressure steam, which can be used for a variety of industrial and commercial applications.

With regard to the main functional requirements, it is key to completely fill all the gaps in the porous ceramic component (electrolyte matrix) inserted between the cathode and anode. This filling is not only a barrier to prevent gas composition lowering of performance (in fact, in the vacancies of electrolyte, the CO ² generated by the cathode ₃ ^- do the transport of the ion of the negative electrode occur). For both electrodes, the essential property for the completion of the reaction is the presence of a triphasic contact surface, ie gas / CO ₃ ^{2 -} ions / electrons. Thus, it is evident that performance depends on the access / removal of gas and CO ₃ ^{2 −} ions from the reaction site, in addition to the electro-catalytic properties of the electrode material. Therefore, performance is also unacceptable when the electrode is flooded, such as when the amount of electrolyte is insufficient.

For each of the two electrodes, there is an optimal fill to enhance performance: that is, a reduction in efficacy that deviates from the optimal fill. In any case, there are certain ranges in which such filling can still be tolerated and the cell characteristics can be utilized in any case.

In the operating state, the amount of carbonate gradually decreases, so that the filling degree fluctuates with time. To maintain a fill level above the minimum required, it is necessary to start at a fill level above the optimum level.

Carbonates spontaneously distribute in pores with relatively high capillary retention properties.

In order to control the distribution of electrolytes between components, it is necessary to select the correct volume in the cell design and to consider a strict ranking system based on their retention characteristics.

Since the matrix is in any case required to remain in a full state, the conversion of filling must take into account the electrode exclusively. The reaction at the cathode is less penalized by the filling which deviates significantly from the optimum value, compared to the reaction at the anode. Thus, cell designs tend to use a negative electrode by concentrating an initial excess of electrolyte on the negative electrode and then emptying it first. The form of a single cell consists of a triple layer "sandwich" (cathode, matrix of electrolyte, anode) disposed between metal pieces for the purpose of distributing gas and transporting current. In practice, molten carbonate fuel cells (typically denoted by the term "stack") are modular structures that are electrically connected in series but constituted by a number of unit cells parallel to the gas inlet. Electrical connection between cells is achieved with a metal separator (electron conductor) between the negative compartment of one cell and the positive compartment of an adjacent cell. At each end of the cell there is a metal plate; These are usually denoted as "end plates", with one at the cathode and one at the anode.

To provide gas to a single cell, two commonly used approaches are: external manifold and internal manifold. In the case of an external manifold, each of the four sides has a specific function: fuel inlet, fuel outlet, oxidant inlet, oxidant outlet. The first and second couple of faces are located opposite each other. Typically, on each side a manifold is placed directly relative to the side of the battery pack. From the interior region to the manifold, the gas reaches directly to the part to which they are assigned.

In the case of an internal manifold, gas injection into a single cell is achieved through a composite groove in the bipolar plate that separates the cell from the cell.

Prior art

The prior art still suffers from problems associated with the use of an external manifold for electrolyte transfer through the gasket of the manifold. In the case of an external manifold, the airtightness necessary to keep the gas separated from the external environment requires the use of a gasket around the surface of the battery pack that is in contact with the manifold.

For technical reasons, the use of metallic o-rings is not possible: a practical solution considers the use of different materials, such as tissues or caulks, which are generally mixtures of ceramic powder, for example with the addition of fluidization means. . In any case, a porous structure is obtained that is permeable to the electrolyte and in communication with the electrolyte of all cells. As a result, the gasket of the manifold represents the possible passage of electrolyte between the cells, so a single cell cannot be considered independent.

In a stack, the cells are electronically connected in series: as a result there is a potential gradient along the stack between the two ends. This potential hardness causes the migration of alkali ions of the electrolyte through the gasket from the cell located on the positive extremity to the cell connected to the negative extremity, and thus in the "negative" cell. In the "excess production" and "positive" cells of the CO ₃ ^{2 -} ions are accompanied by corresponding "depletion". Cells on the positive end of the stack show a loss of electrolyte in addition to the losses caused by the depletion mechanism.

By changing the gasket properties, even the amount of electrolyte transferred from the anode side to the cathode side of the stack is different. This property does not depend on the number of cells contained in the stack: the movement involves only the cells at both ends and the cells inside.

The result for the cell at the positive end is always the same: the expected discharge causes a decrease in performance, and the amount of electrolyte in the electrode is insufficient, so when the discharge process reaches a critical level, the electrolyte matrix becomes a challenge to the gas. Loss of airtightness and mixing of fuel and oxidant occurs directly into the cell, resulting in a rapid deterioration of the hardware.

Depending on the surface of the cell, its internal structure and the shape of the gasket, the time required to reach the critical condition varies, but the dynamics of the mechanism always remain as described above. For the battery on the negative electrode side, there is a risk of flooding of the electrode with a significant drop in performance. Thus, this mechanism extends to a larger number of cells, depending on the overflow level of the end cells. Moreover, if no particular composition is used, the mobility of alkali ions in the electrolyte is different (e.g., ion Li for binary eutectic at 62 mol% Li and 38 mol% K, which are always the reference composition). Like one of ⁺ and K ⁺ ).

This differs in the rate of movement by the gasket, so that on the cathode side the electrolyte shows a higher concentration of the most mobile ions (K ⁺ in the example cited above) and less mobile ions on the anode side (Li in the above example). ⁺ ) This phenomenon further denatures the cell performance at both ends, and in special cases may lead to solidification of the electrolyte at operating temperature (650 ° C.).

In the case of a cell on the negative side of the stack, the kinetics of the mechanism will change rapidly depending on different factors, in particular the surface of the cell, its internal structure, the composition of the electrolyte in the cell and the shape of the gasket.

In order to avoid the effects of electrolyte migration in molten carbonate fuel cells with an external manifold, known solutions used in the prior art have been developed to cover the internal structure of some cells connected to the positive side of the stack and other cells connected to the negative side. Differentiation.

Thus, the solution first uses a relatively thick electrode having a larger volume than the volume of one of the conventional in-cell electrodes “inside” to the stack, so that the electrolyte is placed inside the electrode, and secondly, It is contemplated to use the electrolyte in different loads in the cell "outside" so that the cell on the positive side has a greater amount of electrolyte.

Regardless, even with the best gaskets, in order to produce a stack that should last 40,000 hours, the electrode must be 8 to 10 times thicker than the electrode of a conventional cell in a “outer” cell. It is necessary to use

With an internal structure that is too different from the optimal one, the functionality of such a "reservoir cell" is so impaired that, in particular, operating conditions may also consume energy rather than produce energy. Moreover, the presence of non-standard components will have a negative impact on manufacturing costs; In particular, it is necessary to print and process the separator separately.

 In addition, in the start-up cycle of the stack, the presence of a "storage cell" slows down the whole process, resulting in technical and economic disadvantages.

Another approach is to limit the effect of movement through the control of certain properties of the gasket. For example, US Pat. No. 5,110,692 to Farooque et al. Is such a case. The solution lies in introducing different barriers to the gasket components involved in the migration process. This barrier slows electrolyte flow. The application of this solution is expensive and quite difficult to apply: there is also a problem of very weak efficiency, which is affected by the movement of parts that are very difficult to control during the operation.

Another approach is to limit electrolyte transfer from the cell to the gasket by modifying the porous nature of the components in the cell corner region where contact with the gasket occurs. In these areas, it is necessary to create a drying section of the electrolyte that must be organized into a "labyrinth" structure because separation between the cathode and anode gases must be maintained.

Examples of solutions of this kind are disclosed in US Pat. No. 4,659,635 to Raiser et al. And US Pat. No. 5,478,663 to Cipollini et al. The above modifications should be reflected in all cells as well as the outer cells (ie, cells typically involved in the migration process). Otherwise, on the positive side, the first cell to be evacuated will be a non-protected cell instead of the protected cell, whereas on the negative side the first cell to be flooded will be a non-protected cell instead of the protected cell. Will be. Such solutions appear to be too expensive to apply.

As a result, all the solutions mentioned above are characterized by weak commercial convenience and technical inefficiency.

Another solution proposed by the prior art is to limit the concentration of K ₂ CO ₃ by the cell at the negative electrode. How to achieve this is disclosed in US Pat. No. 4,591,538. When the molar fraction of Li ₂ CO _{3 in} the binary electrolyte Li ₂ CO ₃ / K ₂ CO ₃ is 72%, the ions Li ⁺ and K ⁺ have the same mobility; Therefore, in order to prevent the migration process, the mole fraction of Li ₂ CO ₃ consisting of 70 to 73% is claimed.

However, this solution remains completely inefficient against dry / flooding of the end cells in the absence of complementary tools.

Another method of limiting electrolyte migration without compromising gas exchange and current transport is proposed in Kunz US Pat. No. 4,761,348.

The solution lies in a combination of three factors:

A first porous layer (reservoir) at the cathode of the stack, wherein at least a portion of the side surface is exposed to the oxidant gas and in communication with the gasket through the electrolyte and separated from the last cell by a conducting plate impermeable to the electrolyte;

A second porous layer (reservoir) at the anode of the stack, wherein at least a portion of the side portion is exposed to the fuel gas and in communication with the gasket through the electrolyte and separated from the first cell by a conducting plate impermeable to the electrolyte;

The use of a gasket thicker than that used between the manifold and the cell, between the manifold and the outermost plate.

The obvious limitation of the patent lies in the fact that in both reservoirs, gas access is only allowed through the porosity of the layers forming the reservoir itself, so that the performance of the complete process is severely reduced.

A method for avoiding such limitations is disclosed in US Pat. No. 5,019,464 to Mitsada et al. And describes the following combinations:

A reservoir exposed on the fuel manifold on the anode side, constructed by one or more cathodes and endowed with a current collector / gas distributor, and

A reservoir exposed at the cathode side to the oxidant manifold, constructed by one or more anodes and endowed with a current collector / gas distributor.

The main limitation of the solution described by this patent relates to the resistive losses produced by the stack current through the anode of the "cathode" reservoir. In general, this disadvantage is greater than the benefit for that cell area for commercial applications.

Scope of Invention

Thus, the scope of the present invention is to seek a convenient method for controlling the electrolyte migration process in large area MCFC stacks without incurring the disadvantages of the prior art.

The solution to this problem is to impart electrolyte maintenance tools to molten carbonate fuel cell (MCFCs) stacks based on slightly different combinations of external reservoirs, but this approach provides an essentially different approach to compensating for electrolyte transfer processes. do.

That is, such a tool is based on a combination of two reservoirs, one for each side of the stack, both separated from the active cell by an electrically conductive material that is impermeable to gas; The main feature of this innovative solution is that both reservoirs are exclusively exposed to the fuel gas environment and do not have access to oxidant gas.

More specifically, such electrolyte maintenance tools are characterized by a combination of the following elements:

An anode storage component external to the anode of the first cell on the anode side of the battery, consisting of at least one porous layer of electrically conductive material and comprising at least one gas distributor;

A negative electrode storage component present external to the negative electrode of the last cell on the negative side of the battery and consisting of one or more porous layers of electrically conductive material.

Both reservoirs are exclusively exposed to the fuel gas environment and have no access to the oxidant gas.

A gas impermeable electrically conductive material separates the positive electrode reservoir from the positive cell of the first cell on the positive side of the stack and the negative electrode reservoir from the negative cell of the last cell on the negative side of the stack, respectively. The anode storage element is accessible to at least one of the faces formed by the outer face of the cell in which the fuel gas is present and separated from the oxidant gas. In other words, for example when the anode reservoir is exposed to the fuel inlet region, the remaining three sides formed by the outer side of the cell are each

Oxidant gas supplied to the stack,

-Spent oxidant gas outlet area and

Exposed to spent fuel gas outlet area.

That is, as a standard for a stack with a manifold on the outside, each face contains gas in an area separated from the outside environment by a gasket attached around the face, and certain parts of the gasket contact part of the cell matrix. do.

The positive and negative reservoirs are also in communication with the gasket in contact with the matrix of the cell, via the electrolyte. Both porous layers of the positive and negative reservoirs contain at least 50% Ni; In particular, additionally, in one or both of the reservoirs, the porous layer may further comprise elements consisting of the same negative electrode as the negative electrode of the cell.

The porous gasket is compressed around each of the four sides so that the initial available pore volume is significantly reduced. In a preferred embodiment, inside the strip connecting the matrix of the first cell on the positive electrode side with the matrix of the last cell on the negative electrode side, the volume of residual porosity is less than 4%. Such porosity is available for electrolytes for migration. All cells in the stack consist of a cathode, an electrically conductive fuel gas distributor, an anode, an electrically conductive oxidant gas distributor, and an electrolyte containing matrix. Preferably, the number of cells is greater than 50 and their area is greater than 3500 cm ² .

The main features of the innovative combination are:

An anode reservoir exposed to the fuel environment and endowed with a gas distributor, and

Cathode reservoirs exclusively exposed to the fuel environment (with or without gas distributors).

This combination, which is fully effective for drying the cell adjacent to the positive electrode, gives up completely preventing the "last" cell from overflowing the negative end of the stack. Its purpose is to "stabilize" flooding at the limit values and consequently completely prevent the spread of flooding into other cells.

The main advantage is that there is a negligible loss of resistance across the reservoir. For stacks of large surface cells, this advantage is greater than the performance penalty resulting from the essentially delayed (and partial) flooding of one single cell over the lifetime of the stack.

In other words, reducing the discharge rate of the "first" cell on the positive side is necessary to make the positive electrode reservoir competitive as a "source" of cations to the gasket.

This CO ₃ ^{2 -} means that the reaction of the gas and for the removal of ions as compared with the "first" alternative to the cell inside, must be able to occur without penalties inside the positive electrode storage. This is only possible in the presence of two coexistence factors:

An anode reservoir operating in a fuel environment, and

Anode reservoir with gas distributor.

Symmetrically, increasing the overflow rate of the "last" cell on the negative side is necessary to make the negative electrode reservoir competitive as a "current collector" of cations from the gasket.

This means promoting the formation of CO ₃ ^{2 -} ions inside the cathode reservoir. This process is only possible in the presence of two coexistence factors:

A cathode reservoir operating in an anode environment, and

Cathode reservoir with gas distributor.

The decrease in resistance in the anode environment is quite high and negligible in the fuel environment; Thus, it is apparent that efforts to completely prevent flooding of the cell at the negative electrode end by the "anode" reservoir result in a loss of resistance.

Instead, the reduction in resistance produced by the passage of stack current through an "extra-cathode" reservoir (a reservoir exclusively exposed to the fuel environment) is negligible and stable over time.

 For example, a positive electrode reservoir divided into sections each consisting of two redundant cathodes and one current collector / divider exhibits a resistive loss in the range of 1-2 mV across each section.

In order to meet the increased lifespan goal, it is possible to increase the volume available for storing electrolyte in the positive electrode reservoir by simply increasing the number of conductive porous layers and ultimately also the number of distributors in the reservoir. One current collector and associated set of porous layers is the “section” of the reservoir.

Different sections are separated by metal sheets. By imparting multiple sections to the anode reservoir, cation transfer to the gasket occurs at the same rate in all sections. That is, such a low voltage drop between sections does not produce enough counter fields to affect the efficacy of the farthest sections, so that even for positive electrode storage with 5 to 10 sections, not all Is consistent with comparable efficiency.

By changing the gasket, the amount of electrolyte delivered at certain time intervals from the anode side to the cathode side of the stack is varied. However, when using the same gasket, this amount does not depend on the number of cells or the area of the cells. In contrast, the effect of the migration effect on a particular cell is directly dependent on the cell surface: For small area cells, at short time laps, the amount of electrolyte delivered is already relative to the carbonate content of the cell. Instead, for large "commercial" cells, thousands of hours are needed to see the effect.

 By the MCFC apparatus of the present invention, it is possible to avoid the expected discharge of the battery at the positive electrode, which can lead to the mixing of the negative electrode and the positive electrode gas causing power drop and destructive hardware degradation.

Protecting the positive cell with a reservoir of surplus negative electrode, given a current collector / gas distributor, can reach 40,000 hours of operation time for a 125 kW stack with only 0.02% of power dissipation in its overall useful life.

By using an excess-cathode reservoir at the cathode, as well as being exclusively exposed to the fuel environment, under operating conditions, Li and K ions from the gasket enter the final cathode cell, because the formation of CO ₃ ^{2 −} This occurs more easily at the battery's positive electrode than at. Thus, a mechanism for activating the flooding of the final "cathode" cell is not avoided. Nevertheless, the negative reservoir communicates with the final cell through the electrolyte, and both the cell and the reservoir in the fuel environment are at the same voltage. In such conditions, with the gradual flooding of the cell, the gradual filling of always larger pores by the electrolyte does not activate the driving force for capillary delivery of the electrolyte into the large volume of smaller glass pores available in the reservoir.

By this process, the systematic removal of the electrolyte from the final cell creates a mechanical flow that limits the flooding level of the cell at the most negative side, resulting in effective "protection" of all other cells. The protection time can be easily extended by varying the number of surplus-electrodes in the negative electrode reservoir to impart a larger volume to accommodate higher amounts of electrolyte. In the negative electrode reservoir, as the electrolyte is collected by capillary forces, the presence of a gas distributor is not essential.

Resistor losses run through the lifetime of the stack and increase in proportion to the reservoir size. Instead, the polarization loss caused by flooding proceeds only after the flooding begins. In the case of large-area cells, no overflow occurs for at least about 10,000 hours even in the anode side battery. According to the proposed solution, the resistance loss is negligible even with increasing the reservoir size; Only one cell is affected by the loss of polarization due to flooding, and moreover this flooding remains incomplete and once the threshold is reached, the protection mechanism of the negative electrode reservoir is activated.

Thus, the use of redundant cathodes is a technically and economically convenient solution in any case; In addition, the use of redundant cathodes leads to an absolutely unrelated amount of power loss during the entire operating time of the stack.

The following examples of the present invention are illustrated for illustrative purposes only and should not be construed as limiting the general inventive idea.

1 is a schematic diagram of components disclosed in the present invention.

2 shows a possible embodiment of the reservoir on the anode side of the stack. The reservoir is located between the positive plate 13 and the positive side of the positive side first cell, where the cells are separated by a separator 14 of the same type as the plate used to separate the cells in the stack. Also shown is the current collector / gas distributor 15, the positive electrode 16 and the matrix 18 of the first cell.

In this example, the anode reservoir is subdivided into two sections, each section consisting of two surplus-cathodes 11 and a current collector / gas distributor 12. The two sections are separated by a monopolar plate 17. If there are two or more sections in the reservoir, all the inner sections are separated by a monopolar plate similar to 17. Separation with the anode gas can be achieved through the matrix strip 19 filled with electrolyte.

Similar to FIG. 2, FIG. 3 shows a possible embodiment of a reservoir on the cathode side of the stack. This reservoir is inserted between the terminal negative electrode plate 23 and the negative electrode of the negative electrode last cell, where the cells are separated by a separator plate 24. Also shown is the current collector / gas distributor 25, negative electrode 26 and matrix 28 of the last cell in the stack.

In this example, the anode reservoir is subdivided into two sections, each section consisting of two surplus-cathodes 21 and a current collector / gas distributor 22. The two sections are separated by a monopolar plate 24. Separation with the anode gas can be achieved through the matrix strip 29 filled with electrolyte.

If there are two or more sections in the reservoir, the inner sections are separated by a monopolar plate similar to 24.

In such a reservoir, the current collector / gas distributor can be omitted.

Claims (15)

A molten carbonate fuel cell stack comprising a plurality of cells separated by an electrically conductive material impermeable to gas, comprising: An anode reservoir component external to the anode of the first cell on the anode side of the stack, consisting of at least one porous layer of electrically conductive material and comprising at least one gas distributor; Characterized by a combination of negative electrode components, which are external to the negative electrode of the last cell on the negative side of the stack and consist of one or more porous layers of electrically conductive material, both of which are exclusively exposed to the fuel gas environment. A molten carbonate fuel cell stack that is used intact and is a reservoir inaccessible to oxidant gas. The method of claim 1, And wherein the anode reservoir is separated from the anode of the first cell on the anode side of the stack by an electrically conductive material that is impermeable to the gas. The method of claim 1, And wherein the cathode reservoir is separated from the cathode of the last cell on the cathode side of the stack by an electrically conductive material that is impermeable to the gas. The method according to claim 1 or 2, And wherein the anode storage element is used to access the gas at at least one of the surfaces formed by the outer surface of the cell in which the fuel gas is present and separated from the oxidant gas. The method according to any one of claims 1 to 4, And the anode and cathode reservoirs are used in communication with a gasket in contact with a matrix of the cell through an electrolyte. The method according to any one of claims 1 to 5, The anode and cathode reservoirs are used with fuel gas accessible at the fuel inlet side, while the remaining three sides formed by the outer side of the cell are each Oxidant gas supplied to the stack, Consumed oxidant gas outlet area, and A molten carbonate fuel cell stack, wherein the molten carbonate fuel cell stack is used exposed to the spent fuel gas outlet area. The method according to any one of claims 1 to 5, The anode and cathode reservoirs are used with access to fuel gas at the spent fuel outlet side, while the remaining three sides formed by the outer side of the cell are each Oxidant gas supplied to the stack, Consumed oxidant gas outlet area, and A molten carbonate fuel cell stack, wherein the molten carbonate fuel cell stack is used exposed to fuel gas supplied to the stack. The method according to claim 6 or 7, A molten carbonate fuel cell stack, wherein a gasket is attached around the face, a portion of the gasket is in contact with a portion of the cell matrix, and in use on all sides of the cell stack, the gas is contained in an area separate from the external environment. . The method according to any one of claims 1 to 8, And wherein all of the cells in the stack include a cathode, an electrically conductive fuel gas distributor, an anode, an electrically conductive oxidant gas distributor, and an electrolyte containing matrix. The method according to any one of claims 1 to 9, In a porous gasket compressed around the sides, the molten carbonate fuel cell characterized in that the portion connecting the matrix of the first cell on the anode side with the matrix of the last cell on the cathode side has a volume of residual porosity in the gasket that is less than 4%. stack. The method according to any one of claims 1 to 10, And wherein the porous layers of the anode and cathode reservoirs comprise at least 50% Ni. The method according to any one of claims 1 to 10, At least 50 wt% of Cu or Ni + Cu in the porous layer of the positive and negative reservoirs is molten carbonate fuel cell stack. The method of claim 12, A molten carbonate fuel cell stack, wherein the porous layer of the negative electrode reservoir comprises an element comprised of the same negative electrode as that of the cell. The method of claim 13, A molten carbonate fuel cell stack, wherein the porous layer of the negative electrode reservoir comprises an element comprised of the same negative electrode as that of the cell. The method according to any one of claims 1 to 14, A molten carbonate fuel cell stack, wherein the number of cells is greater than 50 and the area of the cells is greater than 3500 cm ² .

Images