JPH10172595A - Method and device for monitoring carbon deposit of molten carbonate type fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To respond quickly to carbon deposit by monitoring carbon deposit automatically. SOLUTION: Flow meters 9 and 10 and concentration meters for CO2 , H2 O, CH4 11 and 12 are arranged in a gas supply path 7 and exhaust path 8 leading to/from the anode 3 of a fuel cell FC. The rates of gas flow at the inlet to and outlet from the anode 3 are determined by a gas rate-of-flow measuring gauge 13 on the basis of the flow signals 9a and 10a given by the flow meters 9 and 10. The concentrations of CO2 , H2 O, CH4 are determined by a concentration measuring gauge 14 on the basis of the concentration signals 11a and 12a given by the concentration meters 11 and 12. The carbon deposition reaction time and carbon eliminating reaction time are determined from the obtained data of the rates of gas flow and the concentration, and on the basis of these reaction times the carbon eduction time is determined by a calculation device 15. A positive carbon deposit time indicates occurrence of carbon deposition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for monitoring carbon deposition of a molten carbonate fuel cell among fuel cells used in an energy sector for directly converting chemical energy of fuel into electric energy. .

[0002]

2. Description of the Related Art Among molten fuel cells, a molten carbonate type fuel cell, as schematically shown in FIG. 5, is an electrolyte plate (tile) 1 in which a molten carbonate as an electrolyte is impregnated into a porous material.
The cathode (oxygen electrode) 2 and anode (fuel electrode) 3
The cells I sandwiched between the two electrodes are stacked in a multilayer structure with a separator 4 interposed therebetween to form a stack. An oxidizing gas OG is supplied to a gas passage 5 formed on the cathode 2 side of each cell I, and the cell I is supplied to the anode 3 side. The fuel gas F passes through the formed gas passage 6.
G is supplied, and on the cathode 2 side, a reaction of CO ₂ + 1 / 2O ₂ + 2e ⁻ → CO ₃ ⁻ is performed, and the generated carbonate ion CO ₃ ⁻ migrates through the electrolyte plate 1 to form an anode. Then, on the anode 3 side, a reaction of CO ₃ ⁻ + H ₂ → CO ₂ + H ₂ O + 2e ⁻ CO ₃ ⁻ + CO → 2CO ₂ + 2e ⁻ is performed by the supplied fuel gas. A voltage is generated between the anodes 3 to generate power.

In the reaction on the anode 3 side of the molten carbonate fuel cell through which such a carbon, oxygen, and hydrogen based gas flows, when carbon deposition occurs, the anode-side gas passage 6 in each cell of the fuel cell is opened. Blockage or porous anode electrode 3
There is a problem that battery performance is reduced due to blockage of the battery.

Hitherto, it has not been practiced to monitor such carbon deposition and to prevent the occurrence of carbon deposition so as not to cause a decrease in battery performance. Actually, carbon deposition has been confirmed after the problem of deterioration in battery performance due to blockage, electrode blockage, and the like.

[0005] As a method for preventing carbon deposition, a steam injection method, an anode exhaust gas recirculation method, and the like are known, but it is necessary to know the presence or absence of carbon deposition as a premise.

Conventionally, as a method of predicting the occurrence of carbon deposition, a Boudouard reaction: 2CO → C + CO ₂ caulking reaction: CO + H ₂ → C + H ₂ which is a basic reaction formula involving carbon deposition of C, O and H-based gases. O 4 methane production reaction: C + 2H ₂ → CH ₄ was used to predict the occurrence of carbon deposition by equilibrium calculation from the gas composition (initial gas composition) flowing to the anode side of the fuel cell.

[0007]

However, in the conventional method of predicting the occurrence of carbon precipitation by the above-mentioned equilibrium calculation, a composition that finally settles under given constant temperature and pressure conditions is given as an initial gas composition. However, the carbon deposition phenomenon actually occurring is a heterogeneous reaction under a temperature gradient. Therefore, it is necessary to measure how much the above reaction has progressed in the fuel cell, that is, to measure the reaction rate of each reaction actually occurring in the fuel cell and evaluate carbon deposition.

Accordingly, the present invention measures the reaction rate when the above-mentioned basic reaction formula relating to carbon deposition occurs in a fuel cell, and automatically monitors the presence or absence of carbon deposition.
They want to be able to respond quickly.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a fuel cell in which the flow rate of gas supplied to the anode side of each cell at the anode inlet and the anode outlet, CO ₂ , H ₂ O, determine the carbon deposition reaction rate and carbon disappearance kinetics at the anode side and a concentration of CH _4,
Then, the rate of carbon deposition generated on the anode side in the cell is obtained and output from the rate of carbon deposition reaction and the rate of carbon disappearance, and the presence or absence of carbon deposition is monitored by judging whether the rate of carbon deposition is positive or negative. In addition, a flow meter and CO ₂ , H ₂ O, and CH ₄ are respectively provided in the gas flow path on the anode inlet side and the gas flow path on the anode outlet side of each cell of the fuel cell.
A gas flow rate measuring device that measures the gas flow rate at the anode inlet and the anode outlet based on a flow signal from a flow meter provided in the gas flow path on the anode inlet side and the anode outlet side. , CO ₂ , H ₂ O, and C _{2 based on} concentration signals from the concentration meters on the anode inlet side and the anode outlet side.
A concentration measuring device for measuring the concentration of H ₄ , and further, gas flow rates at the anode inlet and outlet measured by the gas flow measuring device and CO ₂ , H ₂ O, C measured by the concentration measuring device.
An arithmetic unit for obtaining and outputting the carbon deposition rate generated on the anode side based on the carbon deposition reaction rate and the carbon elimination reaction rate obtained from the H ₄ concentration data, and whether the carbon deposition rate output from the arithmetic unit is correct. It is configured to include a comparator for determining whether it is negative.

When the gas flow rates at the anode inlet and the anode outlet and the concentrations of CO ₂ , H ₂ O and CH ₄ are obtained, the carbon deposition reaction rate and the carbon elimination reaction rate can be measured based on the obtained gas flow rates. Since the carbon deposition rate generated in the fuel cell is determined from the above, if this carbon deposition rate is positive,
It indicates the occurrence of carbon deposition, and if negative, it can be confirmed that there is no carbon deposition. Therefore, the carbon deposition rate can be obtained and the carbon deposition can be monitored, and measures such as changing the inlet gas composition by increasing CO ₂ or H ₂ O can be taken promptly.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. As shown in FIG. 5, both surfaces of an electrolyte plate 1 are sandwiched between a cathode 2 and an anode 3 and oxidized to the cathode 2 side. A gas is supplied, a fuel gas is supplied to the anode 3 side, and a cell I that causes a reaction on each of the cathode 2 side and the anode 3 side is stacked via a separator to form a stack. In the carbonate fuel cell FC, flow meters 9 and 10 are provided in the supply gas flow path 7 of the anode 3 and the discharge gas flow path 8 of the anode 3.
Concentration meters 11 and 12 for CO ₂ , H ₂ O, and CH ₄ are provided, respectively, and a flow signal 9a from a flow meter 9 in the supply gas flow path 7 and a flow signal 9 from a flow meter 10 in the discharge gas flow path 8 are provided. A gas flow rate measuring device 13 for inputting the flow rate signal 10a and obtaining the total gas flow rate at the anode inlet and the outlet from the flow rate ratio between the inlet side and the outlet side is provided. The concentration signal 11a from the exhaust gas flow path 11 and the concentration signal 12a from the concentration meter 12 in the discharge side gas flow path 8 are input to obtain the concentrations of CO ₂ , H ₂ O, and CH ₄ in the above basic reaction formula. A fuel cell FC is provided based on the total gas flow rate at the anode inlet and outlet from the gas flow rate measuring device 13 and the concentration values of CO ₂ , H ₂ O, and CH ₄ from the concentration measuring device 14. Of the above basic reaction formula and the reaction of carbon deposition応速degree _{R (CO 2), R (} H
₂ O), the reaction rate of carbon elimination R (CH ₄ )
And the carbon deposition rate RC = R (CO ₂ ) + R (H
Comprises ₂ O) -R (CH ₄₎ arithmetic unit 15 for outputting. Further, a comparator 16 for comparing whether the carbon deposition rate RC output from the arithmetic unit 15 is positive or negative is provided. When the carbon deposition rate RC is RC> 0, the occurrence of carbon deposition is indicated. Zero indicates no carbon deposition.

When monitoring carbon deposition according to the present invention, the inlet and outlet of the anode 3 of the fuel cell are determined based on the reaction rates of the respective reactions of the above-mentioned basic reaction involving carbon deposition in the fuel cell FC. The flow rates and concentrations of CO ₂ , H ₂ O, and CH ₄ are constantly sampled so that the occurrence of carbon deposition is known.

That is, the flow signal 9a from the flow meter 9 on the inlet side of the anode 3 of the fuel cell FC and the flow signal 10a from the flow meter 10 on the outlet side of the anode 3 are input to the gas flow rate measuring device 13, And outlet CO ₂ , H ₂ O, CH ₄
Is determined. Further, a concentration signal 11a from the concentration meter 11 on the inlet side of the anode 3 and a concentration signal 12a from the concentration meter 12 on the exit side are input to the concentration measuring device 14, and CO 2 is supplied.
_2. Measure the concentrations of H ₂ O and CH ₄ .

As described above, the total gas flow rates at the inlet and outlet of the anode 3 of the fuel cell FC, CO ₂ , H ₂ O, CH
_When the concentration data of ₄ is obtained, these values are input to the arithmetic unit 15, and among the basic reaction formulas described above, the carbon deposition reaction rate R in and out of the fuel cell FC is calculated.
(CO ₂ ), R (H ₂ O), and the carbon elimination reaction rate R (CH ₄ ) due to the reaction in the fuel cell FC are determined by the following equation.

R (CO ₂ ) = Ux · Vx (CO ₂ ) −Uy · Vy (CO ₂ ) (g / min) R (H ₂ O) = Ux · Vx (H ₂ O) −Uy · Vy (H _{2 O) (g / min)} R (CH 4) = Ux · Vx (CH 4) -Uy · Vy (CH 4) (g / min) here, U is the total flow rate, V is the concentration, x is the outlet, y indicates an entrance.

FIG. 2 shows the relationship between the carbon deposition reaction rate and the time determined by the above equation. In the figure, a circle indicates R (CO ₂ ) which is 2CO → C + CO ₂ in the basic reaction equation. ● indicates CO + H ₂ → C + H ₂ O in the basic reaction formula.
In it indicates R (H ₂ O), also, □ mark indicates the R (CH ₄₎ is a C + 2H ₂ → CH ₄ in the basic reaction scheme.

Further, in the arithmetic unit 15, the carbon deposition reaction rate R (CO ₂ ), R (H ₂ O) and the carbon elimination reaction rate R (CH ₄ ) are generated in the fuel cell FC based on the above. The carbon deposition rate RC is obtained by RC = R (CO ₂ ) + R (H ₂ O) −R (CH ₄ ) (g / min) and output to the comparator 16.

FIG. 3 shows an example of the results of monitoring the carbon deposition. When the carbon deposition rate RC is positive (RC>
If 0), it indicates the occurrence of carbon deposition, and in this case, the amount of carbon deposition can be obtained by integrating over the measurement interval time. If the carbon deposition rate RC in FIG. 3 is RC <0, it means that there is no carbon deposition, that is, decarbonization of the fuel cell constituent material.

The occurrence and absence of carbon deposition in such a fuel cell can be detected and monitored online.

[0021] Thus, it is possible to constantly monitor the carbon deposition in the fuel cell FC, or increase the CO _2, H ₂
It is possible to quickly deal with changing the gas composition at the inlet of the anode 3 by increasing O, thereby preventing carbon deposition.

As a basic reaction formula for carbon deposition, C + 2H ₂ → CH ₄ is shown for carbon elimination. The general formula is C + (n / 2m) H ₂ → (1 / m) CmHn, In this case, m = 1 and n = 4.

Next, FIG. 4 shows another embodiment of the present invention, and the flow meters 9 and 1 in the embodiment shown in FIG.
From the flow rate ratio between the inlet side and the outlet side based on the flow signals 9a and 10a from 0, the total gas flow velocity at the inlet and the outlet is determined by the gas flow rate measuring device
The gas flow velocity is measured by the differential pressure between the inlet side and the outlet side instead of the one obtained in step 3. That is, instead of the flow meters 9 and 10 in FIG.
And 18 are provided, and the gas flow rate measuring device 13 is
And 18, the gas flow velocity can be measured by the differential pressure between the inlet and the outlet, and the other configuration is the same as that shown in FIG.

In this embodiment, as in the embodiment of FIG. 1, the occurrence of carbon deposition can be constantly monitored.
A quick response to the occurrence of carbon deposition is possible.

[0025]

As described above, according to the method and apparatus for monitoring carbon deposition of a fuel cell according to the present invention, the flow rate of gas flowing on the cathode side in the fuel cell and the C
From the concentrations of O ₂ , H ₂ O and CH ₄ in the carbon elimination reaction, the carbon deposition kinetics and the carbon elimination kinetics are determined, and the carbon deposition kinetics are determined and output. If the carbon deposition kinetics are positive, the carbon deposition kinetics are determined. The carbon deposition can be automatically monitored by indicating the occurrence of carbon deposition, so that carbon deposition can be monitored at all times, and if carbon deposition occurs, it can be quickly addressed to prevent carbon generation. And an excellent effect of not lowering the battery performance can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention.

FIG. 2 is a view showing a result of measuring a carbon deposition reaction rate.

FIG. 3 is a view showing a result of monitoring carbon deposition.

FIG. 4 is a schematic diagram showing another embodiment of the present invention.

FIG. 5 is a sectional view showing an outline of an example of a molten carbonate fuel cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrolyte plate 2 Cathode 3 Anode 7 Supply-side gas flow path 8 Discharge-side gas flow path 9 Flow meter 10 Flow meter 11 Densitometer 12 Densitometer 13 Gas flow rate measuring instrument 14 Concentration measuring instrument 15 Arithmetic unit 16 Comparator I Cell FC fuel battery

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Kenichiro Kondo 3-1-1-15 Toyosu, Koto-ku, Tokyo Inside Ishikawajima Harima Heavy Industries Co., Ltd.Higashiji Technical Center (72) Inventor Joji Shinohara Toyosu-san, Koto-ku, Tokyo Ichikawajima Harima Heavy Industries, Ltd.

Claims (3)

[Claims] 1. A carbon deposition reaction on the anode side based on the flow rates of gas supplied to the anode side of each cell of the fuel cell at the anode inlet and the anode outlet and the concentrations of CO ₂ , H ₂ O, and CH _4. Determine the rate and the rate of carbon elimination reaction,
Then, the rate of carbon deposition generated on the anode side in the cell is obtained and output from the rate of carbon deposition reaction and the rate of carbon disappearance, and the presence or absence of carbon deposition is monitored by judging whether the rate of carbon deposition is positive or negative. A method for monitoring carbon deposition in a molten carbonate fuel cell. 2. A flow meter and a CO ₂ , H ₂ O, and CH ₄ concentration meter are provided in a gas flow path on the anode inlet side and a gas flow path on the anode outlet side of each cell of the fuel cell, respectively. A gas flow rate measuring device for measuring a gas flow rate at the anode inlet and the anode outlet based on a flow signal from a flow meter provided in a gas flow path at the anode inlet side and the anode outlet side; and the anode inlet side and the anode outlet side A concentration measuring device for measuring the concentration of CO ₂ , H ₂ O, and CH _{4 based on} a concentration signal from a concentration meter from the above. Further, the gas flow rates at the anode inlet and the outlet measured by the gas flow rate measuring device and the concentration An arithmetic unit for obtaining and outputting a carbon deposition rate generated on the anode side from a carbon deposition reaction rate and a carbon elimination reaction rate obtained from CO ₂ , H ₂ O, and CH ₄ concentration data measured by a measuring device; From the computing device An apparatus for monitoring carbon deposition of a molten carbonate fuel cell, comprising a comparator for determining whether the applied carbon deposition rate is positive or negative. 3. A gas pressure gauge is provided in place of the flow meter, and a gas flow rate between the anode inlet and the anode outlet is obtained from a difference in gas pressure between the anode inlet and the anode outlet.
The apparatus for monitoring carbon deposition of a molten carbonate fuel cell as described in the above.