JP2018104731A - Electrochemical apparatus and operation method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a decrease in hydrogen separation performance due to carbon precipitation in an electrochemical device 100 as compared with the conventional one. An electrochemical device 100 is provided on one main surface of an electrolyte membrane 1a that conducts protons and the electrolyte membrane 1a, and separates hydrogen in a hydrogen-containing gas generated from a fuel into protons and electrons. An electrochemical cell 1 provided on the other main surface of the electrolyte membrane 1a and having a cathode electrode 1c for generating hydrogen from protons and electrons, the cathode electrode 1c and the anode electrode 1b. The upper limit of the current value flowing between the current controller 2 and the anode electrode 1c and the anode electrode 1b is positive with respect to a change in at least one of the temperature and the flow rate of the hydrogen-containing gas. It is provided with an upper limit changer 3 that changes so as to have a correlation. [Selection diagram] Fig. 1

Description

  The present invention relates to an electrochemical device including an electrochemical cell using an electrolyte membrane that conducts protons, and an operation method thereof.

  Conventionally, methods of Patent Documents 1 and 2 are known as methods for separating hydrogen from a hydrogen-containing gas produced by a hydrocarbon reforming reaction.

  In the method of Patent Document 1, an electrochemical cell including a cathode chamber, an anode chamber, and a high-temperature proton conductive solid electrolyte membrane provided therebetween is used. By supplying a reformed gas (hydrogen-containing gas) to the anode chamber, supplying water vapor to the cathode chamber, and passing a current through the membrane through the anode and the cathode, the reactions shown in (Formula 1) and (Formula 2) Advances and hydrogen is separated from the reformed gas.

Anode electrode: H ₂ → 2H ⁺ + 2e ⁻ (Formula 1)
Cathode electrode: 2H ⁺ + 2e ⁻ → H ₂ (Formula 2)
Moreover, in the method of patent document 2, the hydrogen separation cell provided with a cathode, an anode, and the proton conductor provided among these is used. The anode is disposed in a reactor provided with a steam reforming catalyst, and the cathode is disposed in a hydrogen separation chamber. An electric current is passed through the proton conductor through the cathode and the anode to electrochemically transfer hydrogen from the reactor to the hydrogen separation chamber. Thereby, hydrogen is separated from the reformed gas (hydrogen-containing gas) generated by the reforming reaction in the reactor.

  By the way, it is known that when hydrocarbon is reformed, carbon deposition occurs depending on conditions. When carbon deposits in the electrochemical cell, the ability to separate hydrogen from the hydrogen-containing gas by the deposited carbon decreases. The occurrence of such carbon deposition is determined, for example, by performing thermodynamic equilibrium calculation using the ratio of carbon, hydrogen, and oxygen and pressure as parameters, as shown in Non-Patent Document 1.

JP 2003-2610 A JP 2004-31159 A

A. D. Tevebaugh, E. J. Cairns, “Carbon Deposition Boundaries in the CHO System at Several Pressures”, J. Chem. Eng. Data, 10, 359-362 (1965)

  However, the conventional techniques described in Patent Documents 1 and 2 still have room for improvement from the viewpoint of a decrease in hydrogen separation performance due to carbon deposition. This invention solves such a problem, and it aims at providing the electrochemical apparatus by which the fall of the hydrogen separation performance by carbon precipitation compared with the past is reduced, and its operating method.

  An electrochemical device according to an aspect of the present invention includes an electrolyte membrane that conducts protons, and hydrogen in a hydrogen-containing gas that is provided on one main surface of the electrolyte membrane and that is generated from fuel, into protons and electrons. An anode electrode, an electrochemical cell provided on the other main surface of the electrolyte membrane and including a cathode electrode that generates hydrogen from protons and electrons, and current control for passing a current to the cathode electrode and the anode electrode And an upper limit changer that changes an upper limit value of a current flowing between the cathode electrode and the anode electrode so as to have a positive correlation with a change in at least one of the temperature and flow rate of the hydrogen-containing gas. With.

  According to the electrochemical device of the present invention, a decrease in hydrogen separation performance due to carbon deposition is reduced as compared with the conventional apparatus.

  The above object, other objects, features, and advantages of the present invention will become apparent from the following detailed description of embodiments with reference to the accompanying drawings.

1 is a block diagram schematically showing a configuration of an electrochemical device according to an embodiment of the present invention. It is a C-H-O ternary diagram in which changes in anode gas composition and carbon deposition limit are plotted when methane is used as fuel and S / C = 2.0. It is a flowchart which shows an example of the operation | movement method of the electrochemical apparatus of FIG. It is a block diagram which shows roughly the structure of the electrochemical apparatus which concerns on the modification 1 of embodiment of this invention. It is a block diagram which shows roughly the structure of the electrochemical apparatus which concerns on the modification 2 of embodiment of this invention. It is a block diagram which shows roughly the structure of the electrochemical apparatus which concerns on the modification 3 of embodiment of this invention.

(Knowledge that is the basis of the present invention)
The present inventors diligently studied the electrochemical device in order to reduce the hydrogen separation performance due to carbon deposition. As a result, the present inventors have found that the prior art has the following problems.

  In the electrochemical device, hydrogen is separated from the hydrogen-containing gas by the reactions of the above (formula 1) and (formula 2) occurring at the anode electrode and the cathode electrode.

  In addition, it is known that methane, which is a hydrocarbon, precipitates carbon according to (Equation 3). It is also known that carbon may be deposited by carbon monoxide disproportionation (Formula 4).

CH ₄ ← → C + 2H ₂ (Formula 3)
2CO ← → C + CO ₂ (Formula 4)
When carbon deposits in the electrochemical cell, the deposited carbon closes the catalyst layer of the anode electrode. Thereby, the gas diffusibility in an anode electrode falls and the hydrogen separation performance in an electrochemical cell will fall.

  A gas containing hydrocarbon and water vapor is supplied to the anode electrode. When the molar ratio (S / C) between water vapor and carbon in the gas supplied to the anode is low, carbon deposition tends to occur. However, the higher the S / C, the greater the thermal energy for generating water vapor from the water, so the efficiency of the entire hydrogen production apparatus decreases. For this reason, considering efficiency and carbon deposition, for example, S / C is set to about 2.0 to 3.0.

  Even in such a state where S / C is set, carbon may be deposited when hydrogen separation is performed in a state where the temperature of the electrochemical cell is not sufficiently raised, such as at the time of startup.

  On the other hand, neither of Patent Documents 1 and 2 describes that carbon deposition is reduced and reduction in hydrogen separation performance due to carbon deposition is reduced as compared with the prior art.

  One aspect of the present invention has been made on the basis of the above knowledge, and the upper limit value of the current value flowing between the anode electrode and the cathode electrode is determined with respect to a change in at least one of the temperature and the flow rate of the hydrogen-containing gas. Change to a positive correlation. Thereby, carbon deposition is reduced, and a decrease in hydrogen separation performance due to carbon deposition is reduced as compared with the prior art.

  An electrochemical device according to a first embodiment of the present invention includes an electrolyte membrane that conducts protons, and hydrogen in a hydrogen-containing gas that is provided on one main surface of the electrolyte membrane and that is generated from fuel. An electrochemical cell comprising an anode electrode that separates electrons, a cathode electrode that is provided on the other main surface of the electrolyte membrane and generates hydrogen from protons and electrons, and a current to the cathode electrode and the anode electrode A current controller to flow, and an upper limit value of a current value flowing between the cathode electrode and the anode electrode is changed so as to have a positive correlation with a change in at least one of the temperature and flow rate of the hydrogen-containing gas. And an upper limit changer.

  According to this configuration, even if the temperature and / or flow rate of the hydrogen-containing gas changes, the upper limit value of the current value is changed according to this change. By limiting the current value below this upper limit, carbon deposition due to the hydrogen-containing gas is reduced. Therefore, a decrease in hydrogen separation performance due to carbon deposition is reduced as compared with the conventional case.

  In the electrochemical device according to the second aspect of the present invention, in the first aspect, the upper limit changer changes the upper limit value to a value larger than the value before the change when the temperature of the hydrogen-containing gas increases. May be. According to this configuration, when the temperature of the hydrogen-containing gas rises and carbon deposition hardly occurs, the upper limit value is increased. As a result, the amount of hydrogen separated from the hydrogen-containing gas is increased while reducing carbon deposition due to the hydrogen-containing gas, and the hydrogen separation performance is improved.

  The electrochemical device according to a third aspect of the present invention is the electrochemical device according to the first aspect, wherein when the temperature of the hydrogen-containing gas decreases, the upper limit changer changes the upper limit value to a value smaller than the value before the change. May be. According to this configuration, even if the temperature of the hydrogen-containing gas decreases and carbon deposition is likely to occur, the carbon deposition due to the hydrogen-containing gas is reduced by reducing the upper limit value.

  The electrochemical device according to a fourth aspect of the present invention is the electrochemical device according to the first aspect, wherein the upper limit changer changes the upper limit value to a value larger than the value before the change when the flow rate of the hydrogen-containing gas increases. May be. According to this configuration, when the flow rate of the hydrogen-containing gas increases and carbon deposition is difficult to occur, the upper limit value is increased. As a result, the hydrogen separation performance can be improved while reducing carbon deposition due to the hydrogen-containing gas.

  In an electrochemical device according to a fifth aspect of the present invention, in the first aspect, the upper limit changer changes the upper limit value to a value smaller than a value before the change when the flow rate of the hydrogen-containing gas decreases. May be. According to this configuration, even if the flow rate of the hydrogen-containing gas is reduced and carbon deposition is likely to occur, the carbon deposition due to the hydrogen-containing gas is reduced by lowering the upper limit value.

  The electrochemical device according to a sixth aspect of the present invention is the electrochemical device according to the first aspect, wherein the upper limit changer changes the upper limit value so as to have a negative correlation with a change in the pressure of the hydrogen-containing gas. Also good. According to this configuration, even when the pressure of the hydrogen-containing gas changes, the upper limit value of the current value is changed according to this change. By limiting the current value below this upper limit, carbon deposition due to the hydrogen-containing gas is reduced. Therefore, a decrease in hydrogen separation performance due to carbon deposition is reduced as compared with the conventional case.

  In an electrochemical device according to a seventh aspect of the present invention, in the sixth aspect, when the pressure of the hydrogen-containing gas increases, the upper limit changer changes the upper limit value to a value smaller than the value before the change. May be. According to this configuration, even if the pressure of the hydrogen-containing gas increases and carbon deposition is likely to occur, the carbon deposition due to the hydrogen-containing gas is reduced by lowering the upper limit value.

  In an electrochemical device according to an eighth aspect of the present invention, in the sixth aspect, when the pressure of the hydrogen-containing gas decreases, the upper limit changer changes the upper limit value to a value greater than the value before the change. May be. According to this configuration, the upper limit value is increased when the pressure of the hydrogen-containing gas decreases and carbon deposition hardly occurs. As a result, the hydrogen separation performance can be improved while reducing carbon deposition due to the hydrogen-containing gas.

  The electrochemical device according to a ninth aspect of the present invention is the electrochemical device according to any one of the first to eighth aspects, wherein the temperature of the hydrogen-containing gas passes through the temperature of the hydrogen-containing gas on the anode electrode and the anode electrode. The lower one of the temperatures of the hydrogen-containing gas may be used. According to this configuration, for example, even when the temperature of the hydrogen-containing gas is decreased due to heat dissipation after passing through the anode electrode, the upper limit value of the current value is changed based on this low temperature. By limiting the current value below this upper limit, carbon deposition in the flow path of the hydrogen-containing gas after passing through the anode electrode is reduced. Therefore, a decrease in hydrogen separation performance due to carbon deposition is reduced as compared with the conventional case.

  The electrochemical device according to a tenth aspect of the present invention may further include a reformer that reforms the fuel to generate the hydrogen-containing gas in any one of the first to ninth aspects. According to this configuration, even when the hydrogen-containing gas generated by the reformer is supplied to the electrochemical cell, the upper limit value of the current value is changed according to a change in the temperature or the like of the hydrogen-containing gas. By limiting the current value below this upper limit, carbon deposition in the electrochemical cell is reduced.

  An electrochemical device operating method according to an eleventh embodiment of the present invention is provided on one main surface of an electrolyte membrane that conducts protons, and hydrogen in a hydrogen-containing gas generated from fuel is converted into protons and electrons. A step (a) of supplying a current to an anode electrode to be separated and a cathode electrode which is provided on the other main surface of the electrolyte membrane and generates hydrogen from protons and electrons; and an upper limit value of a current value is set to the hydrogen-containing gas. (B) which changes so that it may become a positive correlation with respect to the change of at least any one of temperature and flow volume of this. According to this method, even if the temperature and / or flow rate of the hydrogen-containing gas changes, the upper limit value of the current value is changed according to this change. By limiting the current value below this upper limit value, carbon deposition due to the hydrogen-containing gas is reduced, and a decrease in hydrogen separation performance due to carbon deposition is mitigated compared to the conventional case.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout all the drawings, and redundant description thereof is omitted.

(Embodiment)
FIG. 1 is a block diagram schematically showing a configuration of an electrochemical device 100 according to an embodiment. The electrochemical device 100 includes an electrochemical cell 1, a controller 2, and an upper limit changer 3. The electrochemical device 100 also includes a first supply path 4, a fuel supply unit 5, a second supply path 6, a water supply unit 7, an evaporator 8, a first discharge path 9, a combustor 10, an air supply unit 11, 3 supply path 12, second discharge path 13, first temperature detector 14, and voltage application line 15 may be provided.

  The electrochemical cell 1 includes an electrolyte membrane 1a, an anode electrode 1b, and a cathode electrode 1c. The electrolyte membrane 1a is a proton conducting membrane (proton conducting membrane). The anode electrode 1b is an electrode that is provided on one main surface of the electrolyte membrane 1a and separates hydrogen in the hydrogen-containing gas generated from the fuel into protons and electrons. The anode electrode 1b has a reforming function of reforming the fuel to generate a hydrogen-containing gas containing hydrogen. The cathode electrode 1c is an electrode that is provided on the other main surface of the electrolyte membrane 1a and generates hydrogen from protons and electrons. The electrolyte membrane 1a, cathode electrode 1c and anode electrode 1b constitute a membrane electrode assembly.

  The first supply path 4 has an upstream end connected to a fuel supply source (not shown) and a downstream end connected to a flow path of the anode electrode 1 b of the electrochemical cell 1. Examples of the fuel supply source include a fuel cylinder and a fuel infrastructure. Examples of the fuel include hydrocarbon fuels such as natural gas (city gas) and propane gas, and a hydrogen-containing gas obtained by a reformer provided outside.

  The fuel supplier 5 is provided in the first supply path 4 and supplies fuel to the electrochemical cell 1. The fuel supply device 5 has a function of adjusting the flow rate (supply amount) of the fuel supplied to the anode electrode 1b. For example, the fuel supply device 5 includes a booster and a flow rate adjustment valve. May be. As the booster, for example, a constant displacement pump is used, but is not limited thereto.

  The second supply path 6 has an upstream end connected to a water supply source (not shown) and a downstream end connected to the first supply path 4 on the downstream side of the fuel supplier 5. Examples of the water supply source include water supply. When tap water is used as a water supply source, a configuration for removing contained ions, such as using an ion exchange resin, may be employed.

  The water supplier 7 is provided in the second supply path 6 and supplies water. The water supplier 7 has a function of adjusting the flow rate (supply amount) of water. The evaporator 8 is provided in the second supply path 6 on the downstream side of the water supplier 7 and evaporates the water supplied from the water supplier 7.

  The first discharge path 9 has an upstream end connected to the flow path of the anode electrode 1b, and discharges the anode off-gas discharged from the anode electrode 1b. The anode off gas includes a fuel remaining without being reformed by the anode electrode 1b and a combustible gas such as hydrogen remaining without being separated from the hydrogen-containing gas.

  The air supply unit 11 supplies air to the combustor 10 from an air supply source (not shown) such as the atmosphere. The air supply device 11 has a function of adjusting the flow rate (supply amount) of air supplied to the combustor 10.

  The combustor 10 is provided in the first discharge path 9. The combustor 10 burns the anode off gas supplied via the first discharge path 9 with the air supplied from the air supply device 11, and heats the electrochemical cell 1. A heater for heating the electrochemical cell 1 may be provided together with or in place of the combustor 10.

  The third supply path 12 has an upstream end connected to the sweep gas supply source and a downstream end connected to the flow path of the cathode electrode 1 c of the electrochemical cell 1. In order to efficiently transport the hydrogen generated in the cathode electrode 1c, the sweep gas is supplied to the cathode electrode 1c through the third supply path 12. Examples of the sweep gas include water vapor and nitrogen, but are not limited thereto.

  The second discharge path 13 has an upstream end connected to the flow path of the cathode electrode 1c, and a downstream end connected to devices (not shown) such as a hydrogen utilization device and a hydrogen storage device. The hydrogen separated from the hydrogen-containing gas is discharged from the cathode electrode 1c and supplied to the device through the second discharge path 13.

  The first temperature detector 14 detects the temperature of the hydrogen-containing gas in the anode electrode 1 b of the electrochemical cell 1. In the present embodiment, the first temperature detector 14 is disposed on the flow path of the anode electrode 1 b of the electrochemical cell 1. The first temperature detector 14 may have any configuration as long as the temperature of the hydrogen-containing gas can be detected directly or indirectly. That is, the first temperature detector 14 may be provided in the flow path of the anode electrode 1b to directly detect the temperature of the hydrogen-containing gas. Or the 1st temperature detector 14 is provided in the predetermined location (for example, the surface of the piping which forms the flow path of the anode electrode 1b, or its periphery) correlated with the temperature of hydrogen-containing gas, and the temperature of anode gas is indirectly set. It does not matter if it is detected. As the first temperature detector 14, a thermocouple or a thermistor is exemplified.

  The voltage application line 15 is connected to the anode electrode 1b and the cathode electrode 1c and a power source (not shown). A voltage is applied between the anode electrode 1 b and the cathode electrode 1 c by the voltage application line 15. In this embodiment, the power source is an external power source provided outside the electrochemical device 100, but may be provided in the electrochemical device 100. A voltage regulator (not shown) for adjusting a voltage applied between the anode electrode 1b and the cathode electrode 1c is connected to the power source. The voltage applicator (not shown) includes a voltage regulator and a voltage application line 15. The amount of current flowing between the anode electrode 1b and the cathode electrode 1c is adjusted by adjusting the voltage value applied between both electrodes by the voltage applicator. That is, the voltage applicator functions as a current regulator (not shown). The current regulator is not limited to such a form, and a current regulator that regulates the amount of current flowing between both electrodes may be provided separately from the voltage applicator. Examples of such a current regulator include a converter and an inverter. At this time, the voltage applied between the two powers by the voltage applicator is constant, and the amount of current flowing between the two electrodes may be adjusted by a current regulator such as a converter.

  The controller 2 controls each component of the electrochemical device 100. The controller 2 may have any configuration as long as it has a control function. The controller 2 includes, for example, an arithmetic circuit and a storage circuit that stores a control program. Examples of the arithmetic circuit include an MPU and a CPU. An example of the memory circuit is a memory. The controller 2 may be composed of a single controller that performs centralized control, or may be composed of a plurality of controllers that perform distributed control in cooperation with each other.

  The controller 2 outputs signals to the fuel supply unit 5, the water supply unit 7, and the air supply unit 11, and adjusts the supply amount of each supply unit by controlling the current pulse and voltage of the signal.

  The controller 2 also functions as a current controller that allows current to flow from the cathode electrode 1c to the anode electrode 1b. The controller 2 controls the current value of the current flowing from the cathode electrode 1c to the anode electrode 1b by the power source by controlling the current regulator. The current controller is provided in the controller 2 as one function of the controller 2, but may be provided separately from the controller 2.

  The upper limit changer 3 changes the upper limit value of the current flowing between the anode electrode 1b and the cathode electrode 1c so as to have a positive correlation with a change in at least one of the temperature and flow rate of the hydrogen-containing gas. The upper limit changer 3 includes, for example, an arithmetic circuit and a storage circuit that stores a program. Examples of the arithmetic circuit include an MPU and a CPU. An example of the memory circuit is a memory. Although the upper limit changer 3 is provided separately from the controller 2, the upper limit changer 3 may be provided in the controller 2 as one function of the controller 2.

  Next, an operation method of the electrochemical device 100 according to the embodiment will be described with reference to FIGS. This operation method is controlled by the controller 2.

  1 is output (step S1: YES), the fuel is supplied to the combustor 10 by the fuel supplier 5, and the air is supplied to the combustor 10 by the air supplier 11. (Step S2). In the combustor 10, fuel is combusted by air, and the electrochemical cell 1 is heated by this combustion heat.

  When the electrochemical cell 1 reaches a predetermined temperature, water is supplied by the water supplier 7 (step S3). This water is converted into water vapor by the evaporator 8, and the water vapor is mixed with fuel and supplied to the anode electrode 1 b of the electrochemical cell 1. Then, the controller 2 causes a current to flow from the anode electrode 1b to the cathode electrode 1c via the voltage application line 15 (step S4).

  Thereby, the fuel is reformed in the anode electrode 1b, and a hydrogen-containing gas containing hydrogen is generated. Hydrogen in the hydrogen-containing gas becomes hydrogen ions (protons) at the anode electrode 1b, and electrons are emitted at this time (the above formula 1). Protons pass through the electrolyte membrane 1a and react with electrons at the cathode electrode 1c to generate hydrogen (formula 2 above). As a result, hydrogen is separated from the hydrogen-containing gas, and is supplied to the hydrogen utilization device or the like through the second discharge path 13 together with the sweep gas from the third supply path 12.

  Here, if the temperature and / or flow rate of the hydrogen-containing gas of the anode 1b changes (step S5: YES), carbon may be deposited. The temperature of the hydrogen-containing gas is acquired from the first temperature detector 14. Further, the flow rate of the hydrogen-containing gas varies depending on the amount of fuel supplied by the fuel supplier 5 and the amount of water supplied by the water supplier 7. For this reason, the flow rate of the hydrogen-containing gas is determined by at least one of the supply amount of fuel supplied from the fuel supply device 5 and the supply amount of water supplied from the water supply device 7.

  In step S5, the controller 2 changes at least one of the temperature and flow rate of the hydrogen-containing gas based on a value detected by a detector that detects at least one of the temperature and flow rate of the hydrogen-containing gas. It may be determined whether or not. In other words, a flow rate detector that detects the flow rate of the hydrogen-containing gas may be provided in the flow path of the hydrogen-containing gas of the electrochemical device 100. In this case, the controller 2 determines the change based on the flow rate of the hydrogen-containing gas detected by the flow rate detector and / or the temperature of the hydrogen-containing gas detected by the first temperature detector 14.

  In step S5, the controller 2 determines whether the controller 2 changes the control amount that correlates with the temperature of the hydrogen-containing gas and the control amount that correlates with the flow rate. It may be determined whether or not one of them has changed. Here, the temperature of the hydrogen-containing gas is proportional to the flow rate of the hydrogen-containing gas. For this reason, the control amount correlated with the temperature of the hydrogen-containing gas is at least one of the supply amount of fuel supplied by the fuel supply device 5 and the supply amount of water supplied by the water supply device 7. The control amount correlated with the flow rate of the hydrogen-containing gas is, for example, at least one of the supply amount of fuel supplied by the fuel supply device 5 and the supply amount of water supplied by the water supply device 7.

  Therefore, in order to reduce carbon deposition, the upper limit changer 3 changes the upper limit value Im of the current value flowing between the anode electrode 1b and the cathode electrode 1c to a change in at least one of the temperature and flow rate of the hydrogen-containing gas. To a positive correlation (step S6). And the controller 2 controls the electric current value sent through the electrochemical cell 1 below to upper limit Im (step S7).

  Specifically, first, the upper limit changer 3 acquires the fuel supply amount and the water vapor supply amount from the controller 2. The fuel composition is determined in advance according to the fuel supply source.

  And the upper limit changer 3 is based on the composition of the fuel and the supply amounts of the fuel and water vapor, and the amount of carbon atoms X contained in the supply amount (flow rate) of the hydrogen-containing gas per unit time in the anode electrode 1b, The hydrogen atomic weight Y and the oxygen atomic weight Z are calculated. The upper limit changer 3 acquires the temperature of the hydrogen-containing gas at the anode electrode 1 b from the first temperature detector 14.

  And the upper limit changer 3 fixes the parameters (carbon atom weight X, oxygen atom weight Z, the temperature of the hydrogen-containing gas at the anode electrode 1b, and the pressure P0 of the hydrogen-containing gas at the anode electrode 1b) for calculation. Note that the pressure P0 of the hydrogen-containing gas in the anode electrode 1b is obtained in advance by experiments and calculations according to the amount of hydrogen separated in the electrochemical cell 1 and the like.

  Then, the upper limit changer 3 reduces the hydrogen atom amount Y and performs thermodynamic equilibrium calculation for the hydrogen-containing gas. Thereby, the upper limit changer 3 calculates | requires the minimum amount of hydrogen atoms in which carbon deposition does not occur as a limit amount YL of hydrogen atoms for the amount of hydrogen atoms Y included in the flow rate of the hydrogen-containing gas.

  The upper limit changer 3 may perform thermodynamic equilibrium calculation each time the limit amount YL of hydrogen atoms is obtained. Further, the upper limit changer 3 may obtain the limit amount YL of hydrogen atoms by referring to a table obtained in advance by thermodynamic equilibrium calculation instead of the thermodynamic equilibrium calculation.

Further, when the proton conductor exhibits proton conductivity by incorporating H ₂ O, an amount of H ₂ O (two hydrogen atoms) according to the temperature of the proton conductor and the pressure of the hydrogen-containing gas in the proton conductor. , One oxygen atom) is reduced. For this reason, the hydrogen partial pressure and oxygen partial pressure in the hydrogen-containing gas are reduced. Therefore, these pressures may be subtracted from the pressure P0 of the hydrogen-containing gas to determine the limit amount YL of hydrogen atoms. However, since H ₂ O is often taken into the proton conductor before the hydrogen separation is possible in the electrochemical cell 1, the decrease in hydrogen partial pressure and oxygen partial pressure may be ignored. .

  As another method for obtaining the limit amount YL of hydrogen atoms, for example, there is a method using the C-H-O ternary diagram of FIG. FIG. 2 is a C—H—O ternary diagram (C: H: O ratio information) showing carbon deposition regions at 500 ° C. and 600 ° C. FIG. This C-H-O ternary diagram plots the composition (boundary line) of the hydrogen-containing gas when hydrogen is separated under a predetermined pressure with methane as the fuel and S / C at 2.0. Has been. In addition, although the case where methane is used for fuel is demonstrated below, since it is the same also when the other fuel is used, the description is abbreviate | omitted.

  In the C—H—O ternary diagram of FIG. 2, the solid lines indicate the amount of carbon atoms, the amount of hydrogen atoms, and the amount of oxygen atoms contained in the supply amount (flow rate) of the hydrogen-containing gas per unit time in the anode electrode 1 b of the electrochemical cell 1. % (Composition of hydrogen-containing gas) (%). Moreover, a dotted line is a line (boundary line) which shows the composition of the hydrogen-containing gas in which carbon deposition occurs at 500 ° C. A one-dot chain line is a line (boundary line) indicating a composition of a hydrogen-containing gas in which carbon deposition occurs at 600 ° C. Carbon is deposited thermodynamically in the region (carbon deposition region) above these lines (the side where the carbon atom ratio is large).

  For example, the hydrogen-containing gas having the composition of point X on the solid line in FIG. 2 is located in the carbon deposition region above the 500 ° C. boundary line and below the 600 ° C. boundary line. For this reason, when the temperature of the hydrogen-containing gas in the anode electrode 1b of the electrochemical cell 1 is 600 ° C. or higher, carbon deposition does not occur in the anode electrode 1b. However, when the temperature of the hydrogen-containing gas is 500 ° C. or lower, carbon deposition occurs on the anode electrode 1b.

  On the other hand, the composition of the hydrogen-containing gas is changed in the direction in which the proportion of hydrogen increases on the solid line. Thereby, the composition of the hydrogen-containing gas is located below the boundary line of the carbon deposition region at 500 ° C., and carbon deposition is avoided.

  Thus, the flow rate of the hydrogen-containing gas at which carbon deposition occurs is determined by the C—H—O ternary diagram (carbon deposition limit C: H: O ratio information) indicating the carbon deposition region and the temperature of the hydrogen-containing gas. . Therefore, the upper limit changer 3 acquires the temperature of the hydrogen-containing gas at the anode electrode 1 b from the first temperature detector 14. And the upper limit changer 3 calculates | requires the hydrogen atom amount which carbon does not precipitate as the limit amount YL of a hydrogen atom based on the C: H: O ratio information of a carbon deposition limit, and the temperature of hydrogen-containing gas.

  When the limit amount YL of hydrogen atoms is determined in this way, the upper limit changer 3 determines a value obtained by subtracting the limit amount YL of hydrogen atoms from the hydrogen atom amount Y as the upper limit amount of hydrogen separation that can avoid carbon deposition. The upper limit changer 3 determines the upper limit value of the number of electrons given to the electrochemical cell 1 from the upper limit amount in consideration of the time for the hydrogen-containing gas to pass through the anode electrode 1b. The correspondence between the upper limit amount and the upper limit value of the number of electrons is obtained in advance by calculation or the like in the form of a table or the like. Then, the upper limit changer 3 converts the upper limit value of the number of electrons into an upper limit value Im of the current value, and changes the upper limit value of the current value to this value (step S6).

  For example, the controller 2 controls the current regulator to limit the current value flowing from the anode electrode 1b to the cathode electrode 1c via the voltage application line 15 to be equal to or lower than the upper limit value Im of the current value (step S7). Note that a current value obtained by multiplying the upper limit value of the current value converted from the upper limit value of the number of electrons by a predetermined safety factor may be set as the upper limit value Im.

  The upper limit value Im of this current value has a positive correlation with changes in at least one of the temperature and flow rate of the hydrogen-containing gas. For example, in the case shown in FIG. 2, when the amount of hydrogen atoms is 80% or less, the higher the temperature of the hydrogen-containing gas, the lower the limit amount YL of hydrogen atoms that cause carbon deposition. Further, when the current value is the same, as the flow rate of the hydrogen-containing gas increases, the rate at which the composition of the hydrogen-containing gas changes due to hydrogen separation decreases, and the limit amount YL of hydrogen atoms that cause carbon deposition decreases. Thus, as the limit amount YL decreases, the upper limit amount of hydrogen separation that can avoid carbon deposition increases, and the upper limit value of the number of electrons given to the electrochemical cell 1 and thus the upper limit value Im of the current value increases. .

  As described above, the upper limit changer 3 changes the upper limit value Im of the current value so as to have a positive correlation with the change in the temperature of the hydrogen-containing gas. Accordingly, even when the temperature of the hydrogen-containing gas changes, carbon deposition due to the hydrogen-containing gas is reduced at the anode electrode 1b, so that the performance degradation of the electrochemical cell 1 is mitigated compared to the conventional case.

  That is, when the temperature of the hydrogen-containing gas rises, the upper limit changer 3 changes the upper limit value Im of the current value to a value larger than the value before the change. According to this, when the temperature of the hydrogen-containing gas rises and carbon deposition hardly occurs, the upper limit value is increased. As a result, the amount of hydrogen separated from the hydrogen-containing gas is increased while reducing carbon deposition due to the hydrogen-containing gas, and the hydrogen separation performance is improved.

  On the other hand, when the temperature of the hydrogen-containing gas decreases, the upper limit changer 3 changes the upper limit value Im of the current value to a value smaller than the value before the change. According to this, even if the temperature of the hydrogen-containing gas decreases and carbon deposition is likely to occur, the carbon deposition due to the hydrogen-containing gas is reduced by reducing the upper limit value.

  Further, the upper limit changer 3 changes the upper limit value Im of the current value so as to have a positive correlation with the change in the flow rate of the hydrogen-containing gas. Thereby, even when the flow rate of the hydrogen-containing gas changes, carbon deposition due to the hydrogen-containing gas at the anode electrode 1b is reduced, so that the performance degradation of the electrochemical cell 1 is reduced as compared with the conventional case.

  That is, when the flow rate of the hydrogen-containing gas increases, the upper limit changer 3 changes the upper limit value Im of the current value to a value larger than the value before the change. According to this, when the flow rate of the hydrogen-containing gas increases and the carbon deposition hardly occurs, the upper limit value is increased. As a result, the hydrogen separation performance can be improved while reducing carbon deposition due to the hydrogen-containing gas.

  On the other hand, when the flow rate of the hydrogen-containing gas decreases, the upper limit changer 3 changes the upper limit value Im of the current value to a value smaller than the value before the change. According to this, even if the flow rate of the hydrogen-containing gas decreases and carbon deposition is likely to occur, the carbon deposition due to the hydrogen-containing gas is reduced by lowering the upper limit value.

  In the above example, the upper limit changer 3 includes the carbon atom weight X, the hydrogen atom weight Y, and the oxygen atom weight Z, the temperature of the hydrogen-containing gas obtained from the first temperature detector 14, and the thermodynamic equilibrium calculation or shown in FIG. Although the upper limit amount of hydrogen separation was calculated based on the C-H-O ternary diagram and the upper limit value of the current was finally calculated, the present invention is not limited to this example.

  For example, the upper limit changer 3 stores a table in which at least one of the temperature of the hydrogen-containing gas and the flow rate of the hydrogen-containing gas is associated with the upper limit value of the current value in the storage unit of the upper limit changer 3. May be. In this case, the upper limit value of the current selected based on at least one of the temperature of the hydrogen-containing gas after the change and the flow rate of the hydrogen-containing gas and the above table may be set.

(Modification 1)
The electrochemical device 100 according to the first modification of the embodiment may further include a pressure detector 16 as shown in FIG. The pressure detector 16 detects the pressure of the hydrogen-containing gas on the anode electrode 1 b of the electrochemical cell 1. The pressure detector 16 may have any configuration as long as it can directly or indirectly detect the pressure of the hydrogen-containing gas on the anode electrode 1b.

  The upper limit changer 3 acquires the pressure of the hydrogen-containing gas on the anode electrode 1 b detected by the pressure detector 16. Then, the upper limit changer 3 changes the upper limit value Im so as to have a negative correlation with the change in the pressure of the hydrogen-containing gas. According to this, even if the pressure of the hydrogen-containing gas changes, the upper limit value of the current value is changed according to this change. By limiting the current value below this upper limit, carbon deposition due to the hydrogen-containing gas is reduced. Therefore, a decrease in hydrogen separation performance due to carbon deposition is reduced as compared with the conventional case.

  That is, when the pressure of the hydrogen-containing gas increases, the upper limit changer 3 changes the upper limit value to a value smaller than the value before the change. According to this, even if the pressure of the hydrogen-containing gas increases and carbon deposition is likely to occur, the carbon deposition due to the hydrogen-containing gas is reduced by lowering the upper limit value.

  On the other hand, when the pressure of the hydrogen-containing gas decreases, the upper limit changer 3 changes the upper limit value to a value larger than the value before the change. According to this, the upper limit value is increased when the pressure of the hydrogen-containing gas decreases and carbon deposition hardly occurs. As a result, the hydrogen separation performance can be improved while reducing carbon deposition due to the hydrogen-containing gas.

(Modification 2)
The electrochemical device 100 according to the second modification of the embodiment may include a second temperature detector 17 as shown in FIG. The second temperature detector 17 detects the temperature of the hydrogen-containing gas that has passed through the anode electrode 1b. For example, the second temperature detector 17 is provided in the first discharge path 9. The second temperature detector 17 may have any configuration similar to the first temperature detector 14 as long as it can directly or indirectly detect the temperature of the hydrogen-containing gas that has passed through the anode electrode 1b. As the second temperature detector 17, a thermocouple or a thermistor is exemplified.

  The hydrogen-containing gas that has passed through the anode electrode 1b also contains hydrocarbons such as fuel and carbon monoxide. For this reason, if the temperature of the hydrogen-containing gas in the first discharge path 9 is lowered due to heat dissipation or the like, carbon may also be deposited in the first discharge path 9.

  Therefore, the upper limit changer 3 changes the upper limit value of the current flowing between the cathode electrode 1c and the anode electrode 1b so as to be positively correlated with the change in the temperature and flow rate of the hydrogen-containing gas. To do. The temperature of the hydrogen-containing gas is the lower one of the temperature of the hydrogen-containing gas on the anode electrode 1b and the temperature of the hydrogen-containing gas that has passed through the anode electrode 1b.

  In this example, it is assumed that the temperature of the hydrogen-containing gas that has passed through the anode electrode 1b is lower than the temperature of the hydrogen-containing gas on the anode electrode 1b, and the temperature detected by the second temperature detector 17 is hydrogen-containing. It is used as the gas temperature. When the temperature of the hydrogen-containing gas on the anode electrode 1b is lower than the temperature of the hydrogen-containing gas that has passed through the anode electrode 1b, the temperature was detected by the first temperature detector 14 described in the above embodiment shown in FIG. The temperature is used as the temperature of the hydrogen-containing gas.

  Thus, the upper limit changer 3 sets the upper limit value of the current value to the lower temperature change of the temperature of the hydrogen-containing gas on the anode electrode 1b and the temperature of the hydrogen-containing gas that has passed through the anode electrode 1b. Change to a positive correlation. Alternatively, the upper limit changer 3 may change the upper limit value of the current value so as to have a positive correlation with the change between the lower temperature of the hydrogen-containing gas and the flow rate of the hydrogen-containing gas. Thereby, even if the pressure of the hydrogen-containing gas changes, carbon deposition in the anode electrode 1b and the first discharge path 9 is reduced, and reduction in performance of the electrochemical device 100 can be reduced compared to the conventional case.

  The electrochemical device 100 in FIG. 5 may further include the pressure detector 16 in FIG. In this case, the electrochemical device 100 shown in FIG. 5 has the same configuration as the electrochemical device 100 shown in FIG.

(Modification 3)
The electrochemical device 100 according to the third modification of the embodiment may further include a reformer 18 as shown in FIG. The reformer 18 reforms the fuel to generate a hydrogen-containing gas. The reforming reaction in the reformer 18 may take any form, and examples thereof include a steam reforming reaction, an autothermal reaction, and a partial oxidation reaction. In addition, equipment (not shown) required for each reforming reaction is provided as appropriate.

  Also in this case, the electrochemical device 100 shown in FIG. 6 has the same configuration as the electrochemical device 100 shown in FIG.

  Note that the electrochemical device 100 of FIG. 6 may further include the pressure detector 16 of FIG. In this case, the electrochemical device 100 of FIG. 6 has the same configuration as the electrochemical device 100 of FIG.

  Moreover, the electrochemical device 100 of FIG. 6 may further include the second temperature detector 17 of FIG. Also in this case, by having the same configuration as the electrochemical device 100 of FIG. 5, the same operation and effect as the electrochemical device 100 of FIG.

  Furthermore, the electrochemical device 100 of FIG. 6 may further include a pressure detector 16 of FIG. 4 and a second temperature detector 17 of FIG.

  From the foregoing description, many modifications and other embodiments of the present invention are apparent to persons skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

  The electrochemical device and the operation method thereof according to the present invention are useful as an electrochemical device and an operation method thereof, etc., in which a decrease in power generation performance due to carbon deposition is reduced as compared with the conventional one.

1: Electrochemical cell 1a: Electrolyte membrane 1b: Anode electrode 1c: Cathode electrode 2: Controller (current controller)
3: Upper limit changer 18: Reformer 100: Electrochemical device

Claims (11)

An electrolyte membrane that conducts protons, an anode electrode that is provided on one main surface of the electrolyte membrane and separates hydrogen in the hydrogen-containing gas generated from the fuel into protons and electrons, and the other main electrode of the electrolyte membrane An electrochemical cell comprising a cathode electrode provided on a surface and generating hydrogen from protons and electrons;
A current controller for flowing current to the cathode electrode and the anode electrode;
An upper limit changer for changing an upper limit value of a current flowing between the cathode electrode and the anode electrode so as to have a positive correlation with a change in at least one of the temperature and the flow rate of the hydrogen-containing gas. , Electrochemical equipment.   The electrochemical device according to claim 1, wherein the upper limit changer changes the upper limit value to a value larger than a value before the change when the temperature of the hydrogen-containing gas rises.   The electrochemical device according to claim 1, wherein the upper limit changer changes the upper limit value to a value smaller than a value before the change when the temperature of the hydrogen-containing gas decreases.   The electrochemical device according to claim 1, wherein the upper limit changer changes the upper limit value to a value larger than a value before the change when the flow rate of the hydrogen-containing gas increases.   The electrochemical device according to claim 1, wherein the upper limit changer changes the upper limit value to a value smaller than a value before the change when the flow rate of the hydrogen-containing gas decreases.   The electrochemical device according to claim 1, wherein the upper limit changer changes the upper limit value so as to have a negative correlation with a change in the pressure of the hydrogen-containing gas.   The said upper limit changer is an electrochemical apparatus of Claim 6 which changes the said upper limit to a value smaller than the value before a change, if the pressure of the said hydrogen containing gas rises.   The said upper limit changer is an electrochemical apparatus of Claim 6 which changes the said upper limit to a value larger than the value before a change, if the pressure of the said hydrogen containing gas falls.   The temperature of the hydrogen-containing gas is the lower one of the temperature of the hydrogen-containing gas on the anode electrode and the temperature of the hydrogen-containing gas that has passed through the anode electrode, according to any one of claims 1 to 8. The described electrochemical apparatus.   The electrochemical device according to any one of claims 1 to 9, further comprising a reformer that reforms the fuel to generate the hydrogen-containing gas. Provided on one main surface of the electrolyte membrane that conducts protons, and provided on the other main surface of the electrolyte membrane, an anode electrode that separates hydrogen in the hydrogen-containing gas generated from the fuel into protons and electrons, And passing a current through a cathode electrode that generates hydrogen from protons and electrons (a);
A method of operating an electrochemical device comprising: (b) changing an upper limit value of the current value so as to have a positive correlation with respect to a change in at least one of the temperature and flow rate of the hydrogen-containing gas.

Images