JPH04188567A - Power generation device of fuel cell with molten carbonate - Google Patents

Abstract

PURPOSE:To enhance the rate of fuel utilization as a whole by removing the fuel cell reaction heat through heat absorption with the indirect internal modification action in each fuel cell. CONSTITUTION:Aa plurality of molten carbonate fuel cells of indirect internal modification type are arranged and connected serially, and a modification crude gas supply line is furnished so as to supply the modification crude gas to a modifying chamber 5a of an external modifier 5 via a modifying chamber 4 in a fuel cell or cells situated upstream and a one 4 in a fuel cell or cells situated downstream. The outlet from the modifying chamber 5a of the external modifier 5 is connected with the inlet to the anode 3 of fuel cell upstream, and the outlets from the anode 3 and cathode 2 of fuel cell downstream are connected with the inlet to the combustion gas chamber 5b of the modifier 5 through a catalyst combustor 11. Thereby the heat generated through cell reaction per fuel cell can be removed with modification reactions due to heat absorption in modifying chamber and sensible heat of the cathode exhaust gas. This leads to enhancement of the rate of fuel utilization as a whole.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is particularly applicable to molten carbonate fuel cells among fuel cell power generation devices used in the energy sector that directly converts the chemical energy of fuel into electrical energy. This relates to power generation equipment.

[Prior Art] Molten carbonate fuel cells sandwich an electrolyte plate, which is made by impregnating a porous material with molten carbonate as an electrolyte, between two electrodes: a cathode (oxygen electrode) and an anode (fuel electrode).
One cell is a cell in which power is generated by supplying oxidizing gas to the cathode side and fuel gas to the anode side so that reactions occur on both the cathode side and the anode side. This is done by laminating multiple layers with separators in between to form a stack.

When natural gas is used as the fuel, the fuel gas supplied to the anode of such a molten carbonate fuel cell is one obtained by reforming natural gas in a reformer. As a reformer for reforming raw material gas such as natural gas,
Consisting of a reforming chamber filled with a reforming catalyst, a combustion gas chamber placed between the reforming chamber and a heat transfer partition, and a catalytic combustor filled with a combustion catalyst, the combustion heat generated in the catalytic combustor is transferred. In addition to the external reformer, which absorbs heat into the reforming chamber side through a partition wall and reforms the reforming raw material gas through an endothermic reaction in the reforming chamber, we also have a reforming chamber filled with a reforming catalyst. , an indirect internal structure that is inserted every few cells in a fuel cell stack, absorbs the heat generated by the cell reaction to reform the reforming raw material gas, and supplies the fuel gas to the anode of each cell. There is a reformer.

In a conventional molten carbonate fuel cell power generation device that combines the above-mentioned external reformer and indirect internal reformer, as shown in the outline in FIG. A reforming catalyst is filled in every few cells of a stack consisting of stacked cells sandwiched from both sides with a separator in between so as to supply oxidizing gas to the cathode 2 side and supply fuel gas to the anode 3 side. An indirect internal reforming type in which a reforming chamber 4 is inserted so that the reforming raw material gas flows in from one end and is discharged from the other end after contacting the reforming catalyst. A fuel cell I, a catalytic combustor 11, and an external reformer 5 in which a reforming chamber 5a and a combustion gas chamber 5b are arranged via a heat transfer partition wall are installed, and natural gas as a reforming raw material gas is installed. After NG is desulfurized by the desulfurizer 7 on the natural gas supply line 6, it is supplied to the reforming chamber 4 of the fuel cell I through the natural gas preheater 8 together with superheated steam supplied from the steam supply line 29. After some reforming is performed by absorbing the heat generated by the reaction in the fuel cell I in the reforming chamber 4, the reforming chamber 4 is supplied to the reforming chamber 5a of the external reformer 5. A fuel gas supply line 9 is connected to the inlet side of the anode 3 of the fuel cell I so that the fuel gas FG reformed in the reforming chamber 5a of the reformer 5 is supplied to the anode 3 of the fuel cell I. The discharged anode exhaust gas is supplied to the combustion gas chamber 5b of the reformer 5 via the catalytic combustor 11 in the hair node exhaust gas line lO. On the other hand, air A as an oxidizing gas supplied to the cathode 2 of the fuel cell I
After passing through the filter 12 and being pressurized by the air blower 14 on the air supply line 13, the combustion exhaust gas and air preheat in the combustion exhaust gas line 15 connected to the combustion gas chamber 5b outlet side of the reformer 5. The vessel I6 exchanges heat and is heated and supplied to the cathode 2, and the discharged water from the cathode 2 is
A portion of the cathode exhaust gas is recycled from the cathode exhaust gas line 17 to the cathode 2 via a recycle line 18, a recycling gas blower 19, and an air supply line 13, and a portion of the cathode exhaust gas is recycled to the cathode 2 via an outlet branch line. 20 to the combustion gas chamber 5b of the reformer 5 via the catalytic combustor 11, and the remaining cathode exhaust gas is introduced from the cathode exhaust gas line 17 to the steam superheater 21, the steam generator 22, and for reforming. The steam is discharged into the atmosphere through a steam generator 23. Further, the combustion exhaust gas from the combustion gas chamber 5h of the reformer 5 used for preheating the air is passed through the condenser 30 to the gas-liquid separator 24.
The gas-liquid separator 24 is treated with clean water H,0 by a water treatment device 25 and supplied to the gas-liquid separator 24.
The water separated in the gas-liquid separator 24 is pressurized with the water supply pump 26 together with the clean water H20, and is led to the steam generator 22 and the reforming steam generator 23 through the water treatment device 27, and The steam generated in the steam generator 22 can be recovered from the steam recovery line 28, and the steam generated in the reforming steam generator 23 can be collected in the steam superheater 21.
The excess reforming steam is led to the condenser 30 together with the combustion exhaust gas from the combustion gas chamber 5b of the reformer 5 and condensed. That's how it is.

In the case of the above-mentioned indirect internal reforming type fuel cell, fuel
In the case of a fuel cell without an internal reforming chamber 4, the heat generated by the cell reaction in the cell I is removed by the endothermic reforming action of the reforming chamber 4, and at the same time by the sensible heat of the cathode exhaust gas. The amount of gas needed to remove heat from the battery can be reduced compared to the previous model.

[Problems to be Solved by the Invention] However, in the conventional molten carbonate fuel cell power generation device shown in FIG. Is it necessary? In the cell stacking direction of the battery, as shown in Figure 4, the flow rate of cells in each stage is not necessarily uniform, and
Even within one cell, as shown in FIG. 5, if the electrode area becomes large, the fuel flow rate distribution may become uneven. The smaller the flow rate flowing through the cell, the more likely it is that non-uniform flow distribution will occur.

These non-uniform flow rates cause a fuel shortage in a portion of the cell under conditions of high fuel utilization, causing a voltage drop.

Therefore, conventionally, in order to operate a battery in a stable state, the fuel utilization rate had to be lower than a certain value. Moreover, in conventional power generation devices, the heat generated by the battery is removed by the reforming reaction due to endothermic absorption in the reforming chamber 4 and the cooling effect due to the sensible heat of the cathode exhaust gas, so the gas supplied to the fuel cell is removed. Due to the amount of heat, the amount of gas flowing into the fuel cell is small, and the minimum flow rate is determined by the utilization rate of C02,0□.When considering multiple cell stacks, conventional fuel cells are arranged in parallel. It is not possible to increase the amount of gas passing through the battery cells, and
However, the temperature difference between the inlet and outlet sides of the battery becomes large, making it impossible to increase the temperature at the inlet side of the battery cell, making it impossible to raise the battery operating temperature and improving power generation efficiency. .

In addition, since the temperature on the inlet side of the battery cell cannot be raised, there is a concern that carbon precipitation will occur at the anode entrance [-1], and it is not possible to reduce the S/C ratio (steam/carbon molar ratio) to prevent this. In reality, S/C=about 3 is normally adopted at a battery insertion temperature of about 570°C.

Even if an attempt is made to raise the anode inlet temperature by increasing only the anode supply gas temperature while the cell operating temperature is low in order to prevent the above-mentioned carbon precipitation, as shown in Figure 7, the low temperature on the cathode side in the cell Since the temperature drops immediately after being cooled by the gas, the problem of carbon precipitation remains and is not very effective.At the same time, the temperature difference between the anode and the cathode becomes large at the time of input 1, which causes a problem in terms of thermal stress.

Therefore, the present invention improves the total fuel utilization rate even if the one-pass fuel utilization rate in a fuel cell power generation device is low, and increases the transmission end efficiency.
The fuel flow distribution can be improved, and the operating temperature of the battery cell can be increased to improve the efficiency of the cell.
The purpose is to make it possible to lower C.

"Means for Solving the Problems" In order to solve the above problems, the present invention arranges a plurality of indirect internal reforming molten carbonate fuel cells and connects them in series, and converts the reforming raw material gas into reforming chamber in the upstream fuel cell,
A reforming raw material gas supply line is provided to supply the reforming chamber of the external reformer through the reforming chamber of the downstream fuel cell, and the outlet side of the reforming chamber of the reformer is connected to the upstream fuel cell. The anode inlet side of the reformer is connected to the anode inlet side of the reformer, and the outlet sides of the anode and cathode of the downstream fuel cell are connected to the combustion gas chamber inlet side of the reformer via a catalytic combustor.

Alternatively, an external reforming type molten carbonate fuel cell and an indirect internal reforming type molten carbonate fuel cell may be arranged and connected in series, with the indirect internal reforming type fuel cell serving as the upstream or downstream side. , a reforming material gas supply line is provided to supply the reforming material gas to the reforming chamber of the external reformer through the reforming chamber of the indirect internal reforming type fuel cell; Connect the outlet side of the fuel cell to the anode inlet side of the upstream fuel cell,
In addition, a configuration may be adopted in which the outlet sides of the anode and cathode of the downstream fuel cell are connected to the combustion gas chamber inlet side of the reformer via a catalytic combustor.

``When multiple indirect internal reforming fuel cells are connected in series,
The heat generated by the cell reaction for each fuel cell can be removed by a reforming reaction based on the sensible heat of the cathode exhaust gas and heat absorption in the reforming chamber, so the amount of gas flowing to each fuel cell can be reduced. Considering the battery as a whole, the required amount of CO2,02 is constant, so when fuel cells are connected in series, the amount of gas flowing to each fuel cell when multiple fuel cells are connected in parallel is It is necessary to flow an amount equal to the total amount of gas into the upstream fuel cell. This increases the amount of gas passing through the anode, improving the gas flow distribution, and also reduces the temperature difference between the battery inlet and outlet, increasing the battery inlet temperature, which in turn increases the battery inlet temperature. If the operating temperature can be raised, power generation efficiency can be improved, and if the cell inlet temperature can be raised, the carbon deposition conditions can be relaxed, so the S/C can be reduced and the fuel concentration at the anode can be reduced. This can increase the efficiency of the system. Moreover, since the amount of steam consumed decreases due to the decrease in S/C, the amount of recovered steam increases. In addition, since multiple fuel cells are connected in series, even if the fuel utilization rate is low at the anode of the upstream fuel cell, the unused fuel is used at the anode of the downstream fuel cell, resulting in a total The fuel utilization rate can be increased as a result.

Also, among the upstream and downstream fuel cells connected in series,
For example, if only the upstream fuel cell is of the indirect internal reforming type, the reaction heat of the downstream fuel cell cannot be used for reforming, and as a result, the required amount of heat removal from the upstream fuel cell becomes extremely large. Decrease. Since the gas necessary for all fuel cells flows there, the temperature difference between the gas inlet and outlet becomes small, and the operating temperature of the fuel cells approaches the outlet side temperature when arranged in parallel. In other words, the operating temperature of a fuel cell is extremely high, so the cell performance is improved and at the same time the S
Even if /C is low, carbon precipitation can be prevented. If the number of cells on the upstream side is further reduced and moved to the downstream side, the required heat removal amount of the upstream fuel cell becomes negative, and the gas flowing is used for heating instead of heat removal. This is effective in preventing electrolyte volatilization. Also, since H2O and 002 are generated by the anode reaction of the upstream fuel cell and are supplied to the anode of the downstream fuel cell, the problem of carbon precipitation at the downstream anode inlet does not occur, and therefore the S /C can be made smaller.

On the other hand, of the upstream and downstream fuel cells connected in series, if the downstream fuel cell is of the indirect internal reforming type, the heat removal amount of the downstream fuel cell will decrease, and depending on the balance, it may be negative. This allows the exhaust gas from the upstream fuel cell to be directly fed into the downstream fuel cell without being cooled.

[Implementation example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which a molten carbonate fuel cell of indirect internal reforming type is used in a configuration similar to the conventional molten carbonate fuel cell power generation device shown in FIG. The case where two are connected in series is shown.

That is, a cell is shown in which the electrolyte plate 1 is sandwiched between the cathode 2 and anode 3 picture electrodes, and air A is supplied as an oxidizing gas to the cathode 2 side, and fuel gas FG is supplied to the anode 3 side. When forming a stack by stacking multiple layers with a separator in between, for example, for every five layers of cells stacked, a reforming catalyst is filled inside so that the reforming raw material gas can pass through the inside. A reforming chamber 4 is interposed to form a 5-cell/1 reforming chamber type, and the heat generated in the cell reaction is absorbed to carry out the reforming reaction.This is an indirect internal reforming type fuel cell. , and connect the reforming chamber 4 of the upstream indirect internal reforming fuel cell I and the reforming chamber 4 of the downstream indirect internal reforming fuel cell ■ in series. After passing through the reforming chambers 4 and 4 on the downstream side, the partially quantified natural gas NG as the raw material gas is supplied to the reforming chamber 5a of the external reformer 5, and the indirect internal gas on the upstream side is supplied. The anode 3 of the reforming fuel cell I and the anode 3 of the indirect internal reforming fuel cell (2) on the downstream side are connected in series to produce fuel gas reformed in the reforming chamber 5a of the external reformer 5. When the fuel is supplied to the anode 3 of the indirect internal reforming fuel cell (■) on the upstream side, the fuel is used in the order of that anode 3 and the anode 3 of the indirect internal reforming fuel cell (■) on the downstream side. The anode exhaust gas discharged from the anode 3 of the indirect internal reforming fuel cell ■ flows into the catalytic combustor 11 together with a portion of the cathode exhaust gas discharged from the cathode 2 of the downstream indirect internal reforming fuel cell ■. The combustion scum chamber 5b of the reformer 5
be supplied to On the other hand, the cathode 2 of the upstream indirect internal reforming fuel cell I and the cathode 2 of the downstream indirect internal reforming fuel cell 2 are connected via a cooler 31,
The cathode exhaust gas exiting the cathode 2 of the indirect internal reforming fuel cell (2) on the upstream side is cooled by the cooler 31 and then supplied to the cathode 2 of the indirect internal reforming fuel cell (2) on the downstream side. A portion of the cathode exhaust gas discharged from the downstream indirect internal reforming fuel cell is transferred to the recycling line 18.
, is recycled to the cathode 2 on the upstream side via the recycling gas blower 19, and some other cathode exhaust gas is sent from the outlet branch line 20 to the reformer 5 via the catalytic combustor II.
The remaining cathode exhaust gas is led to the steam superheater 21 through the cathode exhaust gas line I7.

The other configurations are the same as those in FIG. 6, and the same components are given the same reference numerals.

After passing through the desulfurizer 7, the natural gas NG is supplied together with the superheated steam supplied from the steam line 29 to the inlet side of the reforming chamber 4 of the indirect internal reforming fuel cell I on the upstream side via the natural gas preheater 8. After the reforming reaction is carried out in the reforming chamber 4, it is guided to the reforming chamber 4 of the indirect internal reforming fuel cell H on the downstream side, where the reforming reaction is also carried out and the reformer 5 is supplied to the reforming chamber 5a. The fuel gas FG finally reformed in the reforming chamber 5a of the reformer 5 is supplied to the anode 3 of the indirect internal reforming fuel cell I on the upstream side. On the other hand, high-temperature air A is supplied from an air supply line 13 to the cathode 2 of the indirect internal reforming fuel cell (2) on the upstream side. On the cathode 2 side, a reaction of CO2+ 1/202 +2e-4COs- is carried out to generate carbonate ions C01-, which pass through the electrolyte plate 1 and reach the anode 3 side. On the side, the fuel gas FG comes into contact with the carbonate ion CO%-, so COi--+ H2→CO2+ H20+ 2 e''
A reaction of COs-+ CO-2CO2+ 2 e- is carried out to utilize the fuel. The anode exhaust gas discharged from the anode 3 of the indirect internal reforming fuel cell I on the upstream side is directly supplied to the anode 3 of the indirect internal reforming fuel cell H on the downstream side. A reaction using unused fuel is performed at the anode 3 and the fuel is discharged, and is supplied to the combustion gas chamber 5b of the reformer 5 via the catalytic combustor 11.

In the above, upstream and downstream fuel cells T, I
Since both I are of the indirect internal reforming type, the heat generated by the battery reaction can be removed by the sensible heat of the cathode exhaust gas and the endothermic action of the reforming reaction in the reforming chamber 4. As a result, the amount of gas for heat removal can basically be reduced compared to the case of a normal fuel cell where heat is removed only by the sensible heat of the cathode exhaust gas. The absolute amount is also small for basic fishing. However, in this case, when multiple fuel cells are arranged in parallel, the amount of gas flowing to each fuel cell is half of the amount of gas that would be required to remove cell heat using only the sensible heat of the cathode exhaust gas, that is, If the fuel cells are arranged in series, it is possible to flow the total amount of gas that would flow in the case of the above-mentioned parallel arrangement, and 0.5 + 0.5 = 1.
amount can be flowed. In particular, since the amount of gas supplied to the anode of the fuel cell is usually smaller than the cathode exhaust gas, the uniformity of the flow distribution is poor, but the fuel type Ml.

When (1) is connected in series, the amount of anode exhaust gas that passes through each cell increases in the series arrangement compared to the case where the fuel cells are arranged in parallel, improving the flow distribution of the anode exhaust gas. It turns out. Furthermore, when the fuel cells I and (2) are arranged in series, a cooler 31 is installed on the outlet side of the cathode 2 of the indirect internal reforming fuel cell (2) on the upstream side.
By supplying the cooled cathode exhaust gas to the cathode 2 of the indirect internal reforming fuel cell H on the downstream side, the amount of cathode exhaust gas on the upstream side can flow directly to the cathode 2 on the downstream side, so when the fuel cells are arranged in parallel. compared to the total amount of gas when flowing gas to each cathode individually.
, 02 can be secured, and as the amount of cathode exhaust gas decreases, the CO2 concentration in the cathode exhaust gas increases, the battery voltage increases, and the recycling gas blower 1
9's power consumption can also be reduced. Furthermore, if fuel cells ■ and ■ are arranged in series, and the fuel cells are arranged in parallel and the cathode exhaust gas flow rate is the same as the total amount of gas flowing to each fuel cell, then as mentioned above, the series arrangement is better. Gas flow increases. At this time, if the amount of heat generated in each cell is the same, the temperature difference between the inlet side and the outlet side of the battery cell can be reduced by increasing the gas flow rate. Increasing the outlet temperature of the battery cells is undesirable due to the loss of electrolyte, so if the outlet temperature of the battery cells is kept the same, if the fuel cells are arranged in series, the temperature on the inlet side can be increased, The operating temperature of the battery can be increased, the battery voltage can be increased, and power generation efficiency can be improved.

In addition, if the operating temperature of the battery is increased, the carbon precipitation reaction (2CO4C'02 +C) at the anode inlet is less likely to occur, so the S/C ratio can be lowered by increasing the operating temperature of the battery, and as a result, the S/C ratio can be lowered. Even if the S/C is reduced by reducing the amount of steam required for reforming, there is no concern about carbon precipitation at the anode inlet, so the amount of reforming steam can be reduced, increasing fuel concentration and improving system performance. Efficiency can be improved and the amount of recovered steam can be increased. Furthermore, an indirect internal reforming type fuel cell system and (2) are connected in series, and the anode exhaust gas from the anode 3 of the fuel cell I on the upstream side is directly supplied to the anode 3 of the fuel cell (2) on the downstream side. Since the unused fuel at the upstream anode is used to cause a reaction at the downstream anode, for example, the fuel utilization rate at the anode 3 of each fuel cell I, H on the upstream and downstream sides is Assuming both are 70%, for fuel cell I, In%xil, 7=70% for fuel cell ■, (100-,70)%x Q, ? =21%
Therefore, a high fuel utilization rate of 91% can be obtained in total. Since the fuel utilization rate can be increased in this way, it is possible to increase the transmission end efficiency of the system, but in this case, multiple fuel cells connected in series.

The one-pass fuel utilization rate of H does not need to be as high as described above, so even if there is unevenness in the fuel flow distribution in the cell stacking direction and within the cell plane, as shown in Figures 4 and 5, , there will be no voltage drop due to partial fuel shortage.

Next, FIG. 2 shows another embodiment of the present invention, in which a cell consisting of an electrolyte plate 1 sandwiched between cathode 2 and anode 3 picture electrodes is laminated in multiple layers via separators. Instead of the 5-cell/1 reforming chamber type in which a reforming chamber 4 is interposed between every five layers of cells in the embodiment shown in FIG. 1, one reforming chamber is inserted every three layers of cells. Indirect internal reforming fuel cell I, which is a 3-cell/1-reforming-chamber type fuel cell with a stacked structure with The fuel cell ■ and ML are installed separately, both fuel cells ■ and ■ are connected in series, and the indirect internal reforming fuel cell ■ is placed on the upstream side. The fuel gas FG reformed in the reforming chamber 5a of the reformer 5 is supplied through the reforming chamber 4 of the indirect internal reforming fuel cell I to the reforming chamber 5a of the reformer 5. ” - supplied to the anode 3 of the upstream fuel cell I, from which it was led to the anode 3 of the downstream fuel cell (2), and also supplied to the cathode 2 of the upstream fuel cell (2). Air A is
When discharged from the cathode 2, it is cooled by a cooler 31 and supplied to the cathode 2 of the fuel cell (2) on the downstream side, and the other configuration is the same as that in Fig. 1. be.

In this example, the upstream fuel cell 2 has a relatively large number of reformers compared to the indirect internal reforming fuel cell shown in FIG. Only a small amount is removed by sensible heat, and most of it is removed by heat absorption in the reforming reaction in the reforming chamber 4. Therefore, the amount of heat removed from the cathode 2 is limited to the extent that the necessary co, , o, :it can be secured. It is possible to reduce the amount of gas supplied.

In this case, in the upstream fuel cell ■, the number of cells should be reduced (
Therefore, the calorific value is correspondingly smaller, and from the viewpoint of securing the necessary CO2, 02, if the gas flow rate is constant, the temperature difference between the inlet side and the outlet [-1 side will be It can be made smaller and the temperature on the cell inlet side can be increased. On the other hand, since the downstream fuel cell ■ is not of the indirect internal reforming type, the cell heat must be removed only by the sensible heat of the cathode exhaust gas, and for this purpose it is necessary to create a temperature difference between the cell inlet side and the exit side. However, there is a fuel cell on the downstream side■
Since the reaction amount is smaller than that on the upstream side, and the cathode exhaust gas emitted from the upstream cathode 2 is cooled by the cooler 3I before being supplied to the downstream cathode 2, battery heat can be removed sufficiently. can be done. On the other hand, the gas discharged from the anode 3 of the upstream fuel cell I contains unused fuel in addition to CO2 and H2O generated by the reaction at the anode 3. At the anode 3, a reaction using unused fuel on the upstream side is performed and the fuel is discharged, and the fuel is introduced into the combustion gas chamber 5b of the reformer 5 via the catalytic combustor 11 together with the cathode exhaust gas. The anode exhaust gas that enters the anode 3 of the downstream fuel cell (■) contains a large amount of CO2 and H2O generated by the reaction at the upstream anode 3 as described above, and has a gas composition that is difficult to cause carbon deposition reactions. Therefore, there is no need to increase the temperature on the anode inlet side, and therefore, operation can be performed with a smaller S/C of the raw material gas supplied to the reformer.

FIG. 3 shows still another embodiment of the present invention, in which the upstream and downstream fuel cells are reversed in the embodiment shown in FIG. A normal fuel cell ■, and an indirect internal reforming fuel cell I on the downstream side
are arranged and connected in series, and natural gas NG is supplied to the reforming chamber 5a of the reformer 5 through the reforming chamber 4 of the fuel cell I on the downstream side via the natural gas supply line 6 (7, where it is reformed). The purified fuel gas FG is supplied to the anode 3 of the fuel cell (2) on the upstream side through the fuel gas supply line 9, and on the other hand,
The air A as oxidation residue is supplied to the cathode 2 of the fuel cell (1) on the upstream side, and the gas discharged from the -T flow side is supplied as is to the cathode 2 and anode 3 of the fuel cell (1) on the downstream side. The other configuration is the same as that shown in FIG.

In the case of this example, the upstream fuel cell (1) removes heat by cooling the cell only with the sensible heat of the cathode exhaust gas, so it is necessary to create a temperature difference between the cathode input and output. In addition, since the downstream fuel cell is an indirect internal reforming type fuel cell, most of the heat generated by the cell reaction is removed by heat absorption during reforming in the reforming chamber 4, so that the cathode exhaust gas is not sensitive. The amount of heat removed by heat is reduced, which makes it possible to omit a cooler provided between the upstream cathode 2 and the downstream cathode 2, and by adjusting the distribution of the number of upstream and downstream cells, Downstream cathode 2
It is also possible to lower the outlet temperature than the inlet temperature, which is effective in preventing electrolyte loss.

It should be noted that the present invention is not limited to the above-described embodiments; for example, although two fuel cells are shown as a plurality of fuel cells, three or more fuel cells may be connected in series. Of course, various changes can be made without departing from the gist of the invention.

[Effects of the Invention] As described above, according to the molten carbonate fuel cell power generation device of the present invention, a plurality of indirect internal reforming type fuel cells are connected in series, and the reforming raw material gas is supplied to the upstream side. The fuel gas is supplied to the reforming chamber of the external reformer via the reforming chamber of the fuel cell and the reforming chamber of the downstream fuel cell, and the fuel gas reformed in the reforming chamber of the external reformer. is used by flowing it to the anode of the upstream fuel cell and then to the anode of the downstream fuel cell, and the air as oxidizing gas is passed to the cathode of the upstream fuel cell and then to the cathode of the downstream fuel cell. Since the anode exhaust gas from the anode on the downstream side and the cathode exhaust gas from the cathode are introduced into the combustion gas chamber of the external reformer, each fuel cell has an indirect internal reforming effect. Since battery reaction heat can be removed by heat absorption, the rate of heat removal due to sensible heat of the cathode exhaust gas can be reduced, and the absolute amount of gas flowing to the cathode can be reduced. Furthermore, since multiple fuel cells are arranged in series, the total fuel utilization rate can be increased without increasing the fuel utilization rate at the anode of each fuel cell, thereby increasing the power generation efficiency. In addition, the amount of anode exhaust gas that passes through each battery cell is larger when the fuel cells are arranged in series than when they are arranged in parallel, so the flow rate is usually smaller than that of the cathode exhaust gas and the uniformity of the flow distribution is reduced. The poor anode exhaust gas flow distribution can be improved. Also, if the fuel cells are arranged in series and a cooler is placed between the upstream and downstream cathodes, the total amount of gas passing through each battery cell will be lower than when the fuel cells are arranged in parallel. As the amount of gas decreases, the concentration of CO2 in the gas increases, making it possible to increase the battery voltage.
The power of the recycling gas blower can also be reduced, and if the amount of cathode exhaust gas that is the same as the total amount of cathode exhaust gas when the fuel cells are arranged in series is made to flow through each battery cell, As a result, the battery inlet temperature can be increased, the temperature difference between the inlet and the outlet can be reduced, and the battery operating temperature can be increased, which in turn can increase the battery voltage and improve efficiency. I can figure it out. In addition, if the S/C (steam/carbon) ratio is reduced by reducing the water vapor required for reforming, in the conventional method, there is a risk that a carbon precipitation reaction will occur at the inlet of the fuel cell anode. Increase the temperature to high (
This makes it difficult for carbon precipitation reactions to occur, making it possible to reduce the S/C ratio, increasing the fuel concentration at the anode, increasing system efficiency, and reducing steam consumption in the reformer. This increases the amount of recovered steam. In addition, if the series-connected downstream fuel cell is an external reforming type fuel cell, in addition to the excellent effects associated with the series arrangement of fuel cells described above, the upstream indirect internal reforming type fuel cell Since the amount of gas for heat is further reduced, the above effect is further increased. The downstream anode has
Since a large amount of CO□ and H2C generated by the reaction at the upstream anode enters, carbon precipitation reaction is less likely to occur at the anode inlet, and S/C can be further reduced. Furthermore, if the upstream fuel cell is of the external reforming type and is connected in series with the downstream indirect internal reforming type fuel cell, in addition to the above-mentioned excellent effects of arranging the fuel cells in series, Since the heat generated in the downstream fuel cell can be removed by endothermic absorption through internal reforming, the use of sensible heat in the cathode exhaust gas can be reduced, and the need for a cooler to cool the gas entering the downstream cathode can be omitted. The output 1-] temperature of the downstream cathode can be lowered than the input [] temperature, which is effective in preventing loss of electrolyte.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an outline of one embodiment of the molten carbonate fuel cell power generation device of the present invention, Fig. 2 is a system diagram showing an outline of another embodiment of the invention, and Fig. 3 is a system diagram showing an outline of another embodiment of the invention. Fig. 4 is a diagram showing the uneven distribution of fuel flow in each stage of the fuel cell, and Fig. 5 shows the flow rate of fuel in the first stage of cells. Figure 6 is a schematic diagram showing an example of the system configuration of a conventional natural gas reforming molten carbonate fuel cell power generation system. FIG. I, IN...Indirect internal reforming fuel cell, ■...
Fuel cell, 1... Electrolyte plate, 2... Cathode, 3.
... Anode, 4... Reforming chamber, 5... External reformer, 5
a... Reforming chamber, 5b... Combustion gas chamber, 6... Natural gas supply line, 9... Fuel gas supply line, 10.
・Anode exhaust gas line, 11...Catalytic combustor, 13
・Air supply line, 16... Air preheater, 17... Cathode 1 waste line, 18... Recycle line,
19... Gas blower for recycling, A... Air, NG
...Natural scum (reformed raw material gas), FG...Fuel gas.

Claims (3)

[Claims] (1) A plurality of indirect internal reforming molten carbonate fuel cells are installed and connected in series, and the reforming raw material gas is transferred to the reforming chamber of the upstream fuel cell and the reforming chamber of the downstream fuel cell. In addition to supplying the reforming chamber of the external reformer through
The reforming chamber outlet side of the external reformer and the anode inlet side of the upstream fuel cell are connected by a fuel gas supply line, and the anode exhaust gas from the anode and the cathode exhaust gas from the cathode of the downstream fuel cell are connected. A molten carbonate fuel cell power generation device characterized in that a part of the fuel cell is introduced into the combustion gas chamber inlet side of the external reformer through a catalytic combustor. (2) An indirect internal reforming type molten carbonate fuel cell and an external reforming type molten carbonate fuel cell are arranged and connected in series,
With the indirect internal reforming type fuel cell as the upstream side, the reforming raw material gas is supplied to the reforming chamber of the external reformer via the reforming chamber of the fuel cell, and The reforming chamber outlet side and the anode inlet side of the upstream fuel cell are connected by a fuel gas supply line, and part of the anode exhaust gas from the anode and cathode exhaust gas from the cathode of the downstream fuel cell is catalytically combusted. A molten carbonate fuel cell power generation device characterized in that the fuel cell is introduced into the combustion gas chamber inlet side of the external reformer through a vessel. (3) An external reforming type molten carbonate fuel cell and an indirect internal reforming type molten carbonate fuel cell are arranged and connected in series,
Claim (
2) The molten carbonate fuel cell power generation device described above.