JP2001256993A - Fuel cell laminate using high-concentration hydrogen gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell laminate using a high-concentration hydrogen gas aiming at improving efficiency of the generating apparatus by raising the fuel utilization rate in the fuel cell laminate without fuel gas recycling and enabling composition simplification and cost reduction for the generating apparatus. SOLUTION: The fuel cell laminate 13 is split into a plural number of blocks having a different number of cell to the laminating direction. The fuel gas is sent first to blocks having a larger number of the splits and its exhaust gas is sent to blocks having a smaller number of the splits. A high-concentration hydrogen gas is used as the fuel gas. In splitting the blocks, the ratio of cell numbers, m:n, is determined so that the hydrogen utilization rate for each of a plural number of blocks is the same as the others. For example, in the case of splitting the block into 2 stages to the laminating direction, the ratio of cell numbers for splitting the block into 2 stages is determined by m:n=1:(1-UH2/100), wherein the number of cells of a first lower block 14 having a larger number of cells is m, wherein the number of cells of a second upper block 15 having a smaller number of cells is n and wherein the hydrogen utilizing rate (%) is UH2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel cell stack using high-concentration hydrogen gas as a fuel gas.

[0002]

2. Description of the Related Art As is well known, a phosphoric acid type fuel cell and a polymer electrolyte fuel cell are provided with a fuel gas (for example, hydrogen) and an oxidant gas (for example, air) as reaction gases and an electrode catalyst layer. The fuel is continuously supplied to the fuel electrode and the oxidant electrode, and the energy of the fuel is electrochemically converted into electric energy. FIG. 5 shows an example of a schematic configuration of a conventional cell stack of a phosphoric acid type fuel cell.

In FIG. 5, a single cell 31 includes a fuel electrode and an oxidant electrode each having an electrode catalyst layer (not shown), an electrolyte layer 32 disposed between the two electrodes, and a fuel gas as a reaction gas. A unit cell comprising a porous ribbed fuel electrode base material 33 and a ribbed oxidizer electrode base material 34 provided with reaction gas flow grooves 36 and 37 for supplying gas and oxidizing gas, and a gas shielding plate And a separator 35. A plurality of the single cells 31 are stacked, and a manifold 38
The fuel cell stack 13 is configured so as to supply and discharge the reaction gas via the and 39.

[0004] As one of the uses of fuel cells, recently, fuel cells utilizing so-called by-product hydrogen for the purpose of effectively utilizing hydrogen generated as a by-product in chemical plants and the like have been attracting attention. For specific examples of the above usage,
It is described below.

First, an example of the soda industry will be described.
FIG. 7 shows an example of a flowchart of the soda electrolysis process. The location where hydrogen is generated is the electrolytic layer of salt water. Theoretically, there is 280 m ³ of hydrogen generated per ton of caustic soda. The feature of the soda electrolysis process is that the hydrogen concentration is extremely high at 99.9% or more, and the consumption of by-product hydrogen in the process of the own factory is small, so many of them are sold to nearby plants via pipelines etc. is there. However, since hydrogen consumption is limited by the location conditions, many factories consume a part of surplus hydrogen as boiler fuel for self-generation.
Therefore, it is conceivable to replace the surplus hydrogen with efficient fuel cell power generation, and specific experiments are being conducted.

In addition to the above, use in the petrochemical industry is conceivable. FIG. 8 shows an example of a flowchart of a process in a petrochemical factory. Hydrogen is mainly generated from the demethanization cryogenic separator during the naphtha cracking and refining process.

[0007] By-product hydrogen in this industry has a high purity of 95% and a large amount of generated (theoretically, about 400 m3 / ton-ethylene), but it is often used for hydrogen consumption in plants (mainly for outflow). Therefore, much of the surplus hydrogen is consumed. However, according to industrial statistics, most petrochemical plants use in-house power generation with a mixture of heavy oil and off-gas (excess hydrogen), suggesting that there is considerable potential for the amount of hydrogen that can be generated by fuel cells.

As described above, an example of a system diagram of a conventional fuel cell power generator using by-produced hydrogen (high-concentration hydrogen gas and a hydrogen component of 95% or more) generated in excess in a chemical plant is described below. Shown in FIG.

In FIG. 6, fuel gas is supplied from the ejector 2 to the fuel cell stack 3 by controlling the flow rate required for power generation of the fuel cell by the flow control valve 1. Here, the supply gas is mixed with the recycle gas 8 in the ejector, and supplies this mixed gas to the fuel electrode 4 of the fuel cell stack 3. At this time, the amount of recycled gas is controlled by the control valve 7 so that the ratio of the amount of gas supplied to the fuel cell stack 3 to the amount of fuel gas consumed in the fuel cell stack becomes constant.

Since the off-gas from the fuel electrode 4 after being used for power generation in the fuel cell stack 3 contains moisture, if it is supplied to the recycle gas system as it is, it will interfere with the control valve 7 and the like. Once cooled, the water in the gas is removed and then reheated by the heat exchanger 9 to return to the recycled gas system. Reference numeral 11 denotes a cooling water supply line, and reference numeral 12 denotes a generated water recovery tank.

In this system, a small amount of gas is exhausted from a flow suppression orifice 30 attached to a purge line 27 in order to prevent impurity gas concentration due to recycling. The exhaust gas from the purge line 27 is supplied to the blower 6
Is diluted with the exhaust gas 28 of the air supplied to the air electrode 5 of the fuel cell stack 3 from the fuel cell stack 3, and is discharged to the atmosphere through a pipe 29.

As described above, in the fuel cell power generator using high-concentration hydrogen gas as fuel gas, the fact that the hydrogen concentration of the fuel outlet side gas in the fuel cell stack is high (the hydrogen partial pressure is high) is utilized. In order to reuse this gas, a recycling line is provided to perform recycling using an ejector, and the efficiency of the apparatus is improved by increasing the fuel utilization rate of the apparatus.

[0013]

As described above, in a conventional fuel cell power generator using high-concentration hydrogen gas as fuel gas, efficiency is improved by recycling fuel gas. It is necessary to recycle the battery exhaust gas after removing a large amount of water and impurities generated from the electrolyte.Moreover, many devices are required to control the flow rate of the recycle. There is a problem that is high.

The present invention has been made in view of the above problems, and an object of the present invention is to improve the efficiency of a power generator by increasing the fuel utilization rate in a fuel cell stack without recycling fuel gas. It is another object of the present invention to provide a fuel cell stack using a high-concentration hydrogen gas capable of simplifying the configuration of a power generation device and reducing costs.

[0015]

In order to solve the above-mentioned problems, the present invention provides a fuel electrode having an electrode catalyst layer, an oxidant electrode, an electrolyte layer disposed between the two electrodes, A unit cell comprising a porous ribbed fuel electrode base material and a ribbed oxidant electrode base material provided with a reaction gas channel groove for supplying a fuel gas and a oxidant gas as a reaction gas to each electrode, A plurality of unit cells are stacked by stacking separators, which are gas shielding plates, and a reaction gas is supplied to and discharged from the reaction gas space via a manifold. It is divided into a plurality of blocks with different numbers of cells in the stacking direction, the fuel gas is supplied first to the block with a large number of divisions, and the exhaust gas is supplied to the block with a small number of divisions, and further as the fuel gas High concentration water In the fuel cell stack using gas, the fuel cell stack is divided by determining the cell number ratio so that the ratio (hydrogen utilization rate) between the fuel gas hydrogen supply amount and the hydrogen consumption amount for each of the plurality of blocks is the same. (Claim 1).

Specifically, in the fuel cell stack according to the first aspect, when the fuel cell is divided into two stages in the stacking direction, the number of cells in the first block having a large number of cells is m, and the number of cells in the first block having a small number of cells is m. The number of cells in block 2 is n, and the hydrogen utilization rate (%) is
When UH ₂ is set, the cell number ratio of the two-stage division is m: n = 1:
(1-UH _2/100) determined by (claim 2).

As described above, as described later in detail, the hydrogen utilization rate in each block can be operated without difficulty at the utilization rate of 80%, which is considered to be the best in terms of fuel efficiency, and the total hydrogen utilization rate of the fuel cell stack is Can be improved.

In order to improve the total hydrogen utilization of the fuel cell stack, three-stage division is more preferable than two-stage division. In this case, the number of cells may be increased. Determine the ratio. That is, in the fuel cell stack according to claim 1, in the case of three-stage division in the stacking direction, the number of cells of the first block having a large number of cells is m, and the number of cells of the second block having a smaller number of cells than the first block is m. the number of cells is n, and further the number of cells s of the second blocks from the cell number less third block, when hydrogen utilization rate (%) and UH _2, the cell number ratio of 3-stage division, m : n: s = 1: ( 1-UH 2/100):
Determined by _{(1-UH 2/100)} 2.

Further, in order to improve the hydrogen utilization rate of the fuel cell stack as a whole, the invention according to claim 4 can be adopted. That is, in the fuel cell stack according to the first aspect, the blocks having a small number of divisions are configured so that the fuel gas returns in the cell plane, and the gas flow space on the downstream side in the plane is reduced. And the cell width ratio (L ₁ : L ₂ ) in the plane is determined so that the hydrogen utilization rate of each divided cell plane section is the same.

Specifically, the fuel cell according to claim 4
In the case of a two-stage division in the stacking direction,
Let m be the number of cells in the first block which is large, and
And the number of cells of the second block having the return configuration is n
And the hydrogen utilization rate (%) is UH _TwoWhen the two-stage split
The cell number ratio m: n and the cell width ratio (L₁: L_Two) To
Determined. m: n = 1: (1-UH_Two/ 100) + (1-UH_Two/ 100)^Two L₁: L_Two= 1: (1-UH_Two/ 100)

Further, when carrying out the above invention, it is necessary to consider the following. When the output of the fuel cell power generation system fluctuates rapidly, or when the fuel gas system is replaced with an inert gas in a short time at the time of stoppage, etc. As a result, the pressure loss increases, and the gas pressure in the block on the inlet side may become excessive. Excessive pressure applied to the fuel electrode and the air electrode of the fuel cell causes an abnormality in the fuel cell. Therefore, it is necessary to adopt a structure that does not apply the excessive pressure. From this viewpoint, the following is preferable.

That is, in the fuel cell stack according to the first aspect, the groove height of the fuel gas flow channel inside the cell in the block with a small number of divisions is larger than the groove height in the block with a large number of divisions. (Claim 6).

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings (FIGS. 1 to 4). In addition,
In the drawings shown below, the same members as those of the related art (FIG. 5) are assigned the same reference numerals, and description thereof will be omitted.

(Configuration of Fuel Cell Stack) (First Embodiment) FIG. 1 is a conceptual perspective view of an embodiment of a fuel cell stack according to the first and second aspects of the present invention. In FIG. 1, 13 is a battery stack, 14 is a lower block, 15 is an upper block, 16 is a fuel gas supply manifold, 17 is a fuel gas discharge manifold, 18 is a fuel gas upper and lower block return manifold, 19 is a fuel gas supply pipe, 2
Numeral 0 denotes a fuel gas discharge pipe, numeral 21 denotes a fuel gas flow path, and the fuel cell stack 13 is divided into an upper block 15 and a lower block 14 by different numbers of cells m and n in the vertical direction.

An upper and lower manifold 18 is provided so that fuel gas is supplied from the manifold 16 to the lower block 14 having a large number of divisions and exhaust gas is supplied to the upper block 15 having a small number of divisions. A manifold 17 for exhausting the exhaust gas of No. 15 is provided. Thereby, the fuel gas flows as indicated by the arrow in the fuel gas flow path 21.

In FIG. 1, the configuration relating to the oxidizing gas system path is not shown, but when air is used as the oxidizing gas, the flow path of the air is low because the oxygen concentration is low. Same as the conventional device. When the oxygen concentration is high, it can be divided similarly to the fuel gas system.

As described above, the division ratio (m: n) of the number of cells of the upper block 15 and the lower block 14 divided by different numbers of cells is set so that the fuel utilization rate for each divided section is the same. to, when the hydrogen utilization rate (%) and UH _2,
m: n = 1: calculated by _{(1-UH 2/100)} , is divided by this ratio. This point will be described in detail later, including the case of division into three or more stages.

(Embodiment 2) FIG. 2 is a conceptual perspective view of an embodiment of a fuel cell stack according to the fourth and fifth aspects of the present invention. In FIG. 2, a fuel gas discharge manifold partition 22 is provided at a fuel gas outlet side portion of a block in which the upper block 15 has a return structure in an in-plane direction in the manifold 18, and an inlet side portion of the upper block 15 is provided. The fuel gas upper block return manifold 23 is provided to allow the fuel gas to flow as indicated by the arrow in the fuel gas flow path 21.

In the embodiment shown in FIG. 2, the cell number ratio m: n and the cell width ratio (L ₁ : L ₂ ) of the two-stage division are determined as follows. This point will be described later in detail.

[0030] m: n = 1: (1 -UH 2/100) + (1-UH 2
_{^{/ 100) 2 L 1: L}} 2 = 1: the _{(1-UH 2/100)} ( Example 3) Figure 3 shows a conceptual perspective view of an embodiment according to the invention of claim 6. In the embodiment of FIG. 3, the heights of the base material grooves 41 and 42 as fuel gas flow grooves provided in the fuel electrode base material 33 among the constituent members of the single cell 31 are as shown in the figure. The groove height D2 in the upper block with a smaller number of divisions is made higher than the groove height D1 in the lower block with a larger number of divisions.

Thus, when the output of the fuel cell power generation system fluctuates rapidly, or when the fuel gas system is replaced with an inert gas in a short time when the fuel cell is stopped, the number of stacked blocks on the gas outlet side is reduced. It is possible to prevent excessive pressure from being generated due to surplus gas or replacement gas generated due to the small amount.

(Selection of Cell Number Ratio and Cell Width Ratio) The cell number ratio of the multi-stage division, the cell width ratio of the in-plane division, and the like will be described below with reference to the selection basis and specific examples.
Now, in the fuel cell stack, m: n:
The ratio is divided into s ratios, and the supply amounts of hydrogen gas to the m, n, and s blocks are F1, F2, and F3, respectively. First, a two-stage division in the stacking direction (selection of m: n) according to claim 2 will be described. Here, assuming that k: the amount of hydrogen used per cell, i: the current UH _{2 of the} fuel cell, and the hydrogen utilization rate (%) to be unified, the utilization rate in the m-cell section is represented by the following equation 1.

UH ₂ = (m · k · i / F1) · 100 (Equation 1) The utilization rate of the n-cell section is similarly expressed by the following Equation 2.

[0034] _{UH 2 = (n · k ·} i / F2) · 100 ( Equation 2) where so is F2 = F1 · (1-UH 2/100), when it is substituted into the above equation 2, UH ₂ = become (n · k · i) · 100 / [F1 · (1-UH 2/100)] ( equation 3).

In order to make the hydrogen utilization rates in the m-cell section and the n-cell section the same, if Equation 1 = Equation 3, then (m · ki · F1) · 100 = (n · ki) · 100 / [F1
_{· (1-UH 2/100} )] next, removing the intersection of both sides in the above formula, m =
n / a becomes _{(1-UH 2/100)} . That is, m: n = 1: (1
-UH _2/100) to become.

Next, a case of a three-stage division in which a third-stage s-cell exists will be described. n: s = 1: Because (1-UH _2/100) and may be familiar, n replaces the 1 _{(1-UH 2/100)} : When you calculate the s is as follows. n: s = (1-UH 2/100) :( 1-UH 2/100) 2 Thus, m: n: the ratio of s is the following expression. That is,
m: n: s = 1: (1-UH 2/100) :( 1-UH 2/100) 2
The general formula when the fuel cell stack is divided into n stages is as follows.

[0037] N1: N2: N3 ··· Nn = 1: (1-UH 2/100) :( 1-UH
^{_{2/100) 2: ··· (}} 1-UH 2/100) (n-1) Further, it is possible to similarly considered by replacing the number of cells N ratio also split plane direction in the cell width L ratio , the general formula, L1: L2: L3 ··· Ln = 1: (1-UH 2/100) :( 1-UH 2/100) 2: ·
To become _{·· (1-UH 2/100} ) (n-1).

Next, a case where the second-stage block has a return structure in the in-plane direction will be described. The second-stage in-plane direction distribution is calculated by the above formula, and the ratio in the stacking direction is first corrected as follows in consideration of the fact that the second-stage block has a return structure in the in-plane direction. I do.

[0039] m: n = 1: (1 -UH 2/100) · (L1 + L2) / L1 ( Equation 4) where the constant part in Equation 4 is calculated as follows.

[0040] (L1 + L2) / L1 = [1+ (1-UH 2/100)]
/ 1 = 1 + (1- UH 2/100) If this is substituted into equation 4, m: n = 1: (1-UH 2/100) · [1+ (1-UH 2/100)] Thus, m: n = 1: the _{(1-UH 2/100)} + (1-UH 2/100) 2.

(Example of division and calculation of transition of hydrogen concentration) FIG.
Next, a trial calculation example of the transition of the hydrogen concentration in the fuel cell stack using the high-concentration hydrogen gas according to the embodiment of the present invention,
It is shown in comparison with the normal concentration (when the hydrogen concentration is 75% with methane reformed gas). 4A shows a case where the hydrogen concentration at the inlet to the fuel cell stack is 97%, and FIG. 4B shows a case where the hydrogen concentration is 95%.
(C) shows the case of 75%. In the trial calculation, the hydrogen utilization rate (UH ₂ ) was assumed to be 80% except for the first stage of the comparative example (FIG. 4C). Generally, it is said that the optimum hydrogen utilization is about 80%. Although the higher the hydrogen utilization rate, the higher the system efficiency, the battery voltage is reduced, which leads to a reduction in efficiency and damage to the cell.

As shown in FIG. 4A, for example, when the fuel cell stack is divided into 100 cells, 20 cells and 4 cells, and the hydrogen concentration at the inlet of by-product hydrogen is 97%, the second stage is used. Even at the outlet, the hydrogen concentration is close to 60%, which is a range that can be sufficiently used even if the third stage is provided. Further, according to the present invention, all the cell blocks are operated at a hydrogen utilization of 80%, and hydrogen is uniformly used in all the cells.
The best fuel efficiency can be obtained without damaging the cell. The total hydrogen utilization in this case is 99.2%.

As shown in FIG. 4B, when the inlet hydrogen concentration is 95%, the hydrogen concentration at the second stage outlet is 50%.
The third stage is difficult to use because it cuts the percentage, but the second stage can be operated without difficulty. In this case, the total hydrogen charge utilization rate up to the second stage is 96%.

As a comparative example with respect to the above, a methane reformed gas (hydrogen concentration 7
FIG. 4C shows the transition of the hydrogen concentration when the cell is divided by the cell number of 2: 1 using about 5%). Here, the second stage hydrogen utilization rate is determined to be 80% so that the best hydrogen utilization rate can be obtained with a division ratio of 80 cells and 40 cells.

In this case, the inlet hydrogen concentration is 75%,
It can be seen that the remaining 25% of the gas goes downstream as it is, so that passing through the fuel cell greatly reduces the hydrogen concentration. Even at the outlet of the first stage, it is as low as about 54%, and the power generation of the second stage is a low hydrogen concentration operation, which deteriorates the characteristics of the fuel cell and damages the electrode itself. Further, at the outlet of the second stage, the hydrogen concentration is reduced to about 19%, so that the fuel cell cannot generate power thereafter.

Further, in this example, it is not possible to set all cells considered to be the best in terms of hydrogen fuel efficiency to 80% utilization, and the first stage is reduced to 61%. Further, the total hydrogen utilization rate is only 93.7%.
Further, even if the division is performed by using the division ratio formula of the present invention, when the hydrogen concentration at the inlet is about 75%, the hydrogen concentration at the outlet is low, and it is impossible to generate power by providing the second stage. In addition, it is impossible to provide a third stage for power generation.

[0047]

As described above, according to the present invention, the electrode
A fuel electrode and an oxidant electrode provided with a catalyst layer, and both electrodes
The electrolyte layer disposed between the electrodes and each electrode
Reactant gas flow for supplying fuel gas and oxidant gas
Porous ribbed fuel electrode substrate with channel grooves and ribbed
A gas shield plate for a unit cell consisting of an oxidizer electrode base material
Laminate multiple single cells with the separator stacked,
The reaction gas is supplied to the reaction gas space via a manifold.
Supply and discharge, and said plurality of stacked
Blocks with different numbers of cells in the stacking direction
And supply fuel gas first to blocks with a large number of divisions
And supply the exhaust gas to blocks with a small number of divisions.
High-concentration hydrogen gas as the fuel gas.
In a fuel cell stack using a plurality of fuel cells,
Ratio of fuel gas hydrogen supply to hydrogen consumption per lock (water
(Cell utilization ratio)
For example, in the case of two-stage division in the stacking direction
, M is the number of cells in the first block having a large number of cells,
The number of cells in the second block having a small number of cells is n, and hydrogen
UH Utilization rate (%)_TwoAnd the cell ratio of the two-stage division
M: n = 1: (1-UH _Two/ 100), and
In the case of three-stage division in the stacking direction, the first block having a large number of cells
Is the number of cells of m, and the number of cells is smaller than that of the first block.
Let n be the number of cells in the second block,
S is the number of cells in the third block having fewer cells than
And UH for hydrogen utilization (%)_TwoAnd the three-stage division
The number ratio is expressed as m: n: s = 1: (1-UH_Two/ 100): (1-U
H_Two/ 100)^TwoThe fuel cell stack will be
The hydrogen utilization in the block is considered to be the best in terms of fuel efficiency.
Operation is possible with a utilization rate of 80% and fuel
It is possible to improve the overall hydrogen utilization rate of the battery stack.
Wear. This allows fuel gas recycling as before.
Cell using high-concentration hydrogen gas without performing
The fuel efficiency of the stack can be increased,
Improve device efficiency, simplify configuration and reduce costs
Can be

[Brief description of the drawings]

FIG. 1 is a conceptual perspective view of an embodiment relating to a fuel cell stack of the present invention.

FIG. 2 is a conceptual perspective view of an embodiment different from FIG. 1 of the present invention.

FIG. 3 is a conceptual perspective view of still another embodiment of the present invention.

FIG. 4 is a diagram showing a trial calculation example of a change in hydrogen concentration in a fuel cell stack using a high-concentration hydrogen gas according to an embodiment of the present invention and a comparative example.

FIG. 5 is a conceptual perspective view of a conventional fuel cell stack.

FIG. 6 is a system diagram of a conventional fuel cell power generator using by-product hydrogen gas.

FIG. 7 is a diagram showing an example of a flowchart of a soda electrolysis process.

FIG. 8 is a diagram showing an example of a process flowchart of a petrochemical plant.

[Explanation of symbols]

13: battery stack, 14: lower block, 15: upper block, 16: fuel gas supply manifold, 17: fuel gas discharge manifold, 18: fuel gas upper and lower block return manifold, 19: fuel gas supply pipe, 20: fuel gas Discharge pipe, 21: fuel gas flow path, 22: partition part for fuel gas discharge manifold, 23: fuel gas upper block return manifold, 41: lower block fuel electrode base material groove,
42: Upper block fuel electrode substrate groove.

Claims (6)

[Claims] 1. A fuel electrode and an oxidant electrode having an electrode catalyst layer, an electrolyte layer disposed between the two electrodes, and a fuel gas and an oxidant gas as reaction gases supplied to each electrode. A plurality of single cells, each of which is formed by stacking a separator as a gas shielding plate on a unit cell including a porous ribbed fuel electrode base material and a ribbed oxidant electrode base material provided with a reaction gas flow channel groove of The reaction gas is supplied to and discharged from the reaction gas space via a manifold, and the stacked single cells are divided into a plurality of blocks with different numbers of cells in the stacking direction. A fuel gas is supplied first to a block having a large number of fuel cells, and the exhaust gas is supplied to a block having a small number of divisions. Further, in a fuel cell stack using a high-concentration hydrogen gas as the fuel gas, Bro Fuel using high-concentration hydrogen gas, characterized in that the fuel cell is divided by determining the cell number ratio so that the ratio of the hydrogen supply amount to the hydrogen consumption amount (hydrogen utilization rate) is the same for each fuel cell. Battery stack. 2. The fuel cell stack according to claim 1, wherein when the division is a two-stage division in the stacking direction, the number of cells of the first block having a large number of cells is m, and the second block having a small number of cells is a second block. The number of cells in a block is n, and the hydrogen utilization rate (%) is UH
When a _2, cell number ratio of 2-stage split m: n of the fuel cell stack using the hydrogen-rich gas, characterized in that determined by the following. m: n = 1: (1 -UH 2/100) 3. The fuel cell stack according to claim 1, wherein when the division is a three-stage division in the stacking direction, the number of cells in the first block having a large number of cells is m, and the number of cells in the first block is larger than the number of cells in the first block. Where n is the number of cells in the second block where the number of cells is smaller, s is the number of cells in the third block where the number of cells is smaller than the second block, and UH ₂ is the hydrogen utilization rate (%). Wherein the cell number ratio m: n: s is determined as follows: m: n: s = 1: (1-UH 2/100) :( 1-UH 2/100) 2 4. The fuel cell stack according to claim 1, wherein the blocks having a small number of divisions are configured so that the fuel gas returns in the cell plane, and the gas flow space on the downstream side in the plane is small. And an in-plane cell width ratio (L ₁ : L ₂ ) is determined so that the hydrogen utilization rate of each of the divided cell plane sections is the same. A fuel cell stack using hydrogen gas at a high concentration. 5. The fuel cell stack according to claim 4, wherein
Therefore, in the case of two-stage division in the stacking direction, the first block having a large number of cells
The number of lock cells is m, the number of cells is small and return
The number of cells in the second block having the configuration is n, and hydrogen
Usage rate (%) UH _TwoAnd the cell number ratio m of the two-stage division:
n and the cell width ratio (L₁: L_Two) Is defined as follows
Fuel cell stack using high concentration hydrogen gas
body. m: n = 1: (1-UH_Two/ 100) + (1-UH_Two/ 100)^Two L₁: L_Two= 1: (1-UH_Two/ 100) 6. The fuel cell stack according to claim 1, wherein the height of the fuel gas passage groove in the cell in the block having a small number of divisions is larger than the height of the groove in the block having a large number of divisions. A fuel cell stack using high-concentration hydrogen gas.