JP4466049B2 - Water flow control method for reforming steam - Google Patents

Description

  The present invention relates to a reformed steam water flow rate control method for controlling the flow rate of reformed steam water in a fuel cell power generator, and in particular, a fuel cell that generates power using hydrogen-rich reformed gas and a hydrogen-rich fuel from raw fuel. A fuel comprising a reforming section that generates reformed gas and supplies it to the fuel cell, and a steam generating section that generates steam from the mixed raw fuel and reformed steam water and supplies the steam to the reforming section The present invention relates to a reforming steam water flow rate control method for controlling the flow rate of reforming steam water in a battery power generation device.

  A fuel cell is a device that converts chemical energy of fuel directly into electrical energy without passing through mechanical energy or thermal energy, and is a device that can achieve high energy efficiency. As a generally well-known form of a fuel cell, there is a form in which a pair of electrodes are arranged with an electrolyte interposed therebetween. In this embodiment, a fuel gas having hydrogen is supplied to one electrode (anode) side of a pair of electrodes, and an oxidizing gas having oxygen is supplied to the other electrode (cathode: cathode) side. An electromotive force can be obtained by using an electrochemical reaction occurring between the two. The electrochemical reaction formula that occurs in the fuel cell is shown below.

H ₂ → 2H ⁺ + 2e ⁻ (1)
(1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

  Equation (1) is a reaction equation showing the reaction on the anode side, Equation (2) is a reaction equation showing the reaction on the cathode side, and Equation (3) is a reaction equation showing the entire reaction of the entire fuel cell.

  Fuel cells (fuel cell power generators) are classified according to the type of electrolyte used. Among fuel cells, polymer electrolyte fuel cell or polymer electrolyte fuel cell (PEFC) using polymer electrolyte membrane, phosphoric acid fuel cell using phosphoric acid as electrolyte (Phosphoric) Acid Fuel Cell (PAFC), Molten Carbonate Fuel Cell (MCFC) that uses an electrolyte with carbonate ions as a charge carrier, etc., due to the nature of the electrolyte used, oxidizing gas or carbon dioxide containing carbon dioxide. It is possible to use gas. Therefore, in these fuel cells, normally, air is used as an oxidizing gas, and a gas containing hydrogen generated by steam reforming a hydrocarbon-based raw fuel such as natural gas is used as a fuel gas.

  For this reason, in a fuel cell power generation device (fuel cell system) provided with the fuel cell as described above, for example, a fuel cell power generation device as disclosed in Patent Document 1 or 2, a reformer and a steam reforming reaction are accompanied. And a carbon monoxide modifier for reducing the concentration of the remaining carbon monoxide. In this reformer and carbon monoxide modifier, the raw fuel is reformed to produce fuel gas. Formula (4) is a reaction formula showing the reforming reaction of methane (steam reforming reaction) in the reformer when methane is used as the fuel.

CH ₄ + H ₂ O → CO + 3H ₂ (+206.14 KJ / mol: endothermic reaction) (4)

  As shown in Equation (4), the reforming reaction of methane is an endothermic reaction that requires an endotherm equal to the heat of vaporization and the heat of reforming. In order to cover this endotherm, water is added to methane, and then the granular reforming catalyst is kept at 600 to 700 ° C. using combustion exhaust gas obtained by burning fuel off-gas from the fuel cell. It produces reformed gas (hydrogen-rich).

  The reformed gas exiting the reformer is supplied to the carbon monoxide modifier in order to reduce the carbon monoxide concentration in the reformed gas. With this carbon monoxide modifier, the carbon monoxide concentration is reduced to 1% or less, so in a phosphoric acid fuel cell (PAFC) that needs to have a carbon monoxide concentration of 1% or less to prevent deterioration of the platinum catalyst. If there is, this gas can be introduced into the PAFC body to generate electricity.

  On the other hand, the polymer electrolyte fuel cell (PEFC) has a low operating temperature of 60 to 80 ° C. because the resistance of the polymer electrolyte membrane is small. For this reason, platinum is used as an electrode catalyst so that the reaction of both electrodes proceeds rapidly. However, if carbon monoxide is present in the reformed gas, the activity is lowered due to catalyst poisoning by the carbon monoxide, so that it is necessary to further reduce the carbon monoxide concentration. Therefore, the reformed gas is supplied to a carbon monoxide modifier, where the carbon monoxide concentration is reduced to 10 ppm or less.

  As described above, since the polymer electrolyte fuel cell (PEFC) has a low operating temperature (reaction temperature), it differs from a phosphoric acid fuel cell (PAFC) with a reaction temperature of about 180 ° C., and its calorific value is used for reforming. Of water vapor cannot be generated. For this reason, it is necessary to generate water vapor in the reforming equipment. The amount of heat (vaporization heat) for generating water vapor is obtained by heat exchange with the residual heat inside the reformer or the combustion exhaust gas after leaving the reformer. In other words, the reforming steam is obtained by supplying the reforming steam water to the steam generating section inside or outside the reformer by the reforming steam water supply pump and vaporizing it.

  FIG. 4 shows a schematic configuration of a conventional fuel cell power generator 80. In FIG. 4, reference numeral 3 is a reformer, 4 is a carbon monoxide (CO) modifier that reduces the concentration of carbon monoxide in the reformed gas exiting from the reformer, and 5 is a reformer that exits from the CO modifier 4. A carbon monoxide (CO) remover for removing carbon monoxide contained in the gaseous gas by converting it into carbon dioxide, 6 is a fuel cell, and for the sake of convenience of the drawing, only the anode 16, the cathode 17 and the cathode side flow path CW18 are shown. . Reference numeral 11 is a combustion air blower for supplying air 30 to the burner 20 of the reformer 3, 10 is a raw fuel gas blower for supplying raw fuel 32 to the desulfurizer 1, and 1 is a raw fuel 32 supplied by the raw fuel gas blower 10. A desulfurizer for desulfurizing contained sulfur, 7 is a reformed steam water tank storing reformed steam water, and 8 is supplied with reformed steam water stored in the reformed steam water tank 7 to the steam generator 2. A reforming steam water supply pump 2 is a steam generator for generating steam from the reforming steam water supplied by the reforming steam water supply pump 8 mixed with the raw fuel 32 desulfurized by the desulfurizer 1, and 25 is A reforming steam water flow meter that measures the flow rate of the reforming steam water supplied to the steam generator 2 by the reforming steam water supply pump 8, and 13 is the reforming steam water measured by the reforming steam water flow meter 25. Modified steam based on flow rate A control device for controlling the water supply pump 8. Control signals and the like between the control device 13, the reforming steam water flow meter 25, and the reforming steam water supply pump 8 are indicated by dotted lines.

  Next, the operation of the conventional fuel cell power generator 80 will be described. The raw fuel 32 from which the sulfur content has been removed in the desulfurizer 1 is mixed with the reforming steam water supplied by the reforming steam water supply pump 8 and then supplied to the steam generator 2 to be vaporized. 3 is supplied. In the reformer 3, a hydrogen-rich reformed gas is generated by the steam reforming reaction represented by the formula (4). In order to carry out the endothermic reaction as described above, the fuel off gas 33 from the fuel cell 6 is supplied to the burner 20 and burned in the furnace 22 to raise the temperature of the catalyst layer 21. The combustion exhaust gas 9 is discharged out of the reformer 3.

The reformed gas exiting from the reformer 3 is supplied to the CO reformer 4 and the hydrogen concentration is increased by the carbon monoxide reaction. Thereafter, the carbon monoxide concentration is reduced to 10 ppm or less by a carbon monoxide selective oxidation reaction that is supplied to the CO remover 5 together with a certain amount of air (not shown) and converted to carbon dioxide. As described above, the reformed gas having a low carbon monoxide concentration is also supplied to the anode 16 of the fuel cell 6.
JP 2003-86210 A JP-A-6-176787

  In the conventional fuel cell power generator 80 described above, the reformed steam water needs to be supplied at an accurate ratio to the flow rate of the raw fuel 32. If the reforming steam water is supplied at a ratio that is too small, the steam reforming reaction will not be performed normally, and problems such as carbon deposition on the catalyst layer 21 of the reformer 3 will occur. On the other hand, when the water for reforming steam is supplied at an excessively large ratio, there is a problem in that the heat efficiency is reduced because extra energy is consumed for evaporation. Furthermore, since the flow rate of the reforming steam water supply pump 8 changes due to a pressure change on the downstream side or a change in performance over time even if the input voltage to the reforming steam is constant, it is necessary to always monitor and control the flow rate. In addition, the reforming steam water flow meter 25 is indispensable. However, the reformed steam water flow meter 25 is generally expensive, and there is a problem that a malfunction may occur due to malfunction of the reformed steam water flow meter 25 itself.

  Accordingly, an object of the present invention has been made to solve the above-described problem, and without using a reforming steam water flow meter that is expensive and may cause a malfunction, on the downstream side of the reforming steam water supply pump. It is an object of the present invention to provide a method for controlling the flow rate of reforming steam water in a fuel cell, which can control the flow rate of reforming steam water without being affected by the pressure change or performance change over time.

The method for controlling the flow rate of water for reforming steam according to the present invention includes a fuel cell that generates power using hydrogen-rich reformed gas, and a reformer that generates hydrogen-rich reformed gas from raw fuel and supplies the reformed gas to the fuel cell. The reformed steam of the fuel cell power generation apparatus comprising: a steam generating unit that generates steam from the mixed raw fuel and the reformed steam water supplied by the reformed steam water supply pump and supplies the steam to the reformed unit a reforming steam water flow control method for controlling the flow rate of the water, by controlling the flow rate of the reforming steam water supplied to the steam generator by increasing or decreasing the voltage of the reforming steam water supply pump, the vapor The temperature measured inside the generator is maintained at a constant temperature determined by a predetermined load factor .

  Here, in the method for controlling the flow rate of water for reforming steam according to the present invention, the steam generating section may be installed inside the reformer.

The method for controlling the flow rate of water for reforming steam according to the present invention includes a fuel cell that generates power using hydrogen-rich reformed gas, and a reformer that generates hydrogen-rich reformed gas from raw fuel and supplies the reformed gas to the fuel cell. A steam generation unit installed in the reforming unit for generating steam from the mixed raw fuel and the reforming steam water supplied by the reforming steam water supply pump and supplying the steam to the reforming unit. A reformed steam water flow rate control method for controlling the flow rate of reformed steam water in a fuel cell power generator, wherein the reformed steam water is supplied to the steam generator by increasing or decreasing the voltage of the reformed steam water supply pump. The temperature measured at the inlet of the reforming section is maintained at a constant temperature determined by a predetermined load factor .

The method for controlling the flow rate of water for reforming steam according to the present invention includes a fuel cell that generates power using hydrogen-rich reformed gas, and a reformer that generates hydrogen-rich reformed gas from raw fuel and supplies the reformed gas to the fuel cell. The reformed steam of the fuel cell power generation apparatus comprising: a steam generating unit that generates steam from the mixed raw fuel and the reformed steam water supplied by the reformed steam water supply pump and supplies the steam to the reformed unit A reformed steam water flow rate control method for controlling the flow rate of water for use, wherein the voltage of the reformed steam water supply pump is set based on a predetermined load factor, and the temperature measured inside the steam generating unit Alternatively, the steam generation unit is installed inside the reforming unit, and the voltage of the reforming steam water supply pump is corrected based on the temperature measured at the inlet of the reforming unit.

  After removing the reformed steam water flow meter 25 in the conventional fuel cell power generator 80, a temperature control point is provided in the steam generator 2. The control device 13 measures the temperature of the temperature control point with a temperature measuring device, and increases or decreases the voltage of the reforming steam water supply pump 8 so that the temperature becomes a constant temperature determined by a predetermined load factor. As a result, without using the reforming steam water flow meter 25 that is expensive and may cause a malfunction, it is not affected by the pressure change on the downstream side of the reforming steam water supply pump 8 or the performance change over time, A method for controlling the flow rate of water for reforming steam of the fuel cell 6 that can control the flow rate of water for reforming steam can be provided.

  Hereinafter, each embodiment will be described in detail with reference to the drawings.

  FIG. 1 shows an outline of the configuration of a fuel cell power generator 50 according to Embodiment 1 of the present invention. In FIG. 1, the portions denoted by the same reference numerals as those of the conventional fuel cell power generation device 80 of FIG. The difference between the fuel cell power generation device 50 of the first embodiment and the conventional fuel cell power generation device 80 is that the reformer steam water flow meter 25 is removed as shown in FIG. 2) The temperature control point 14 is provided in 2. The control device 13 measures the temperature of the temperature control point 14 with the temperature measuring device 19, and the reforming steam water supply pump (supply unit) 8 is configured so that the temperature becomes a constant temperature determined by a predetermined load factor. Increase or decrease the voltage (control input). The temperature around the reformer (reformer) 3 of the fuel cell power generator 50 is always controlled to a temperature corresponding to the load. Therefore, if the temperature of the steam generator 2 is kept constant by increasing / decreasing the voltage of the reforming steam water supply pump 88 as described above, the pressure change downstream of the reforming steam water supply pump 8 or The flow rate of the water for reforming steam can be controlled without being affected by the change in performance over time.

  As described above, according to the first embodiment of the present invention, the temperature control point 14 is provided in the steam generator 2 after removing the reformed steam water flow meter 25 in the conventional fuel cell power generator 80. The control device 13 measures the temperature of the temperature control point 14 by the temperature measuring device 19 and increases or decreases the voltage of the reforming steam water supply pump 8 so that the temperature becomes a constant temperature determined by a predetermined load factor. Can do. As a result, without using the reforming steam water flow meter 25 that is expensive and may cause a malfunction, it is not affected by the pressure change on the downstream side of the reforming steam water supply pump 8 or the performance change over time, A method for controlling the flow rate of water for reforming steam of the fuel cell 6 that can control the flow rate of water for reforming steam can be provided.

  FIG. 2 shows an outline of the configuration of the fuel cell power generator 60 according to Embodiment 2 of the present invention. In FIG. 2, portions denoted by the same reference numerals as those of the fuel cell power generation device 50 of FIG. The difference between the fuel cell power generation device 60 in the first embodiment and the fuel cell power generation device 50 is that the steam generator 2 is installed inside the reformer 3 as shown in FIG. As in the first embodiment, the control device 13 measures the temperature of the temperature control point 14 inside the reformer 3 with the temperature measuring device 19 so that the temperature becomes a constant temperature determined by a predetermined load factor. Furthermore, the voltage of the reforming steam water supply pump 8 can be increased or decreased. For this reason, the flow rate of the reforming steam water can be controlled without being influenced by the pressure change or the performance change with time on the downstream side of the reforming steam water supply pump 8 as in the first embodiment.

  As described above, according to the second embodiment of the present invention, the steam generator 2 is installed inside the reformer 3, and the control device 13 determines the temperature at the temperature control point 14 inside the reformer 3 as a temperature measuring device. The voltage of the reforming steam water supply pump 8 can be increased or decreased so that the temperature measured at 19 becomes a constant temperature determined by a predetermined load factor. As a result, even when the steam generator 2 is installed inside the reformer 3, as in the first embodiment, without using the reformed steam water flow meter 25 which may be expensive and cause malfunction, Provided is a method for controlling the flow rate of water for reforming steam of a fuel cell 6 that can control the flow rate of water for reforming steam without being affected by the pressure change or the change in performance over time of the water supply pump for reforming steam 8. be able to.

  FIG. 3 shows an outline of the configuration of the fuel cell power generator 70 according to Embodiment 3 of the present invention. In FIG. 3, the portions denoted by the same reference numerals as those of the fuel cell power generation device 60 of FIG. The difference between the fuel cell power generation device 70 and the fuel cell power generation device 60 in the third embodiment is that the temperature control point 14 is not the inside of the steam generator 2 but the catalyst layer of the reformer 3 as shown in FIG. It is in the point installed in 21 entrances (reformer entrance). As in the second embodiment, the control device 13 measures the temperature of the temperature control point 14 at the inlet of the catalyst layer 21 of the reformer 3 with the temperature measuring device 19, and the temperature is a constant determined by a predetermined load factor. The voltage of the reforming steam water supply pump 8 can be increased or decreased to reach the temperature. For this reason, similarly to the second embodiment, the flow rate of the reforming steam water can be controlled without being influenced by the pressure change on the downstream side of the reforming steam water supply pump 8 or the performance change with time.

  As described above, according to the third embodiment of the present invention, the temperature control point 14 is installed at the inlet of the catalyst layer 21 of the reformer 3, and the control device 13 sets the temperature of the temperature control point 14 at the inlet of the catalyst layer 21. The voltage of the reforming steam water supply pump 8 can be increased or decreased so that the temperature is measured by the temperature measuring device 19 and the temperature becomes a constant temperature determined by a predetermined load factor. As a result, even when the temperature control point 14 is installed at the inlet of the catalyst layer 21 of the reformer 3, the reformed steam water flow meter 25, which is expensive and may cause malfunction, as in the second embodiment. Control of the flow rate of water for reforming steam of the fuel cell 6 that can control the flow rate of water for reforming steam without using it and without being influenced by the pressure change on the downstream side of the water supply pump for reforming steam 8 or the change in performance over time. A method can be provided.

  In the above-described Examples 1 to 3, the water for reforming steam is set so that the temperature inside the steam generator 2 or the temperature of the inlet of the catalyst layer 21 of the reformer 3 becomes a constant value determined by a predetermined load factor. The method for increasing or decreasing the voltage of the supply pump 8 has been described. As another method, first, the voltage of the reforming steam water supply pump 8 is determined by a predetermined load factor. That is, the supply capacity of the reforming steam water supply pump 8 is determined by a predetermined load factor. In addition, a method of correcting the voltage while measuring the temperature inside the steam generator 2 or the temperature of the inlet of the catalyst layer 21 of the reformer 3 with the temperature measuring device 19 can also be used.

  As an application example of the present invention, application to a fuel cell power generator using a polymer electrolyte fuel cell (PEFC) is particularly mentioned.

It is a figure which shows the outline | summary of a structure of the fuel cell electric power generating apparatus 50 in Example 1 of this invention. It is a figure which shows the outline | summary of a structure of the fuel cell electric power generating apparatus 60 in Example 2 of this invention. It is a figure which shows the outline | summary of a structure of the fuel cell electric power generating apparatus 70 in Example 3 of this invention. It is a figure which shows the outline of a structure of the conventional fuel cell power generator 80. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Desulfurizer, 2 Steam generator, 3 Reformer, 4 CO modifier, 5 CO remover, 6 Fuel cell, 7 Water tank for reformed steam, 8 Water supply pump for reformed steam, 9 Combustion exhaust gas, 10 Raw fuel Gas blower, 11 Combustion air blower, 13 Control device, 14 Temperature control point, 16 Anode, 17 Cathode, 18 CW (cooling water), 19 Temperature measuring device, 20 Burner, 21 Catalyst layer, 22 In-furnace, 25 Water for reforming steam Flow meter, 30 air, 33 fuel off-gas, 50, 60, 70 fuel cell power generator, 80 conventional fuel cell power generator.

Claims (4)

A fuel cell that generates power using hydrogen-rich reformed gas, a reforming unit that generates hydrogen-rich reformed gas from raw fuel and supplies the reformed gas to the fuel cell, and a mixed raw fuel and water supply for reformed steam Water flow control for reforming steam for controlling the flow rate of reforming steam water of a fuel cell power generation device comprising steam for generating steam from reforming steam water supplied by a pump and supplying the steam to the reforming unit A method,
The flow rate of the reforming steam water supplied to the steam generating unit is controlled by increasing or decreasing the voltage of the reforming steam water supply pump, and the temperature measured inside the steam generating unit is determined by a predetermined load factor. A method for controlling the flow rate of water for reforming steam, characterized by maintaining a constant temperature .   The method for controlling the flow rate of water for reforming steam according to claim 1, wherein the steam generator is installed inside the reformer. A fuel cell that generates power using hydrogen-rich reformed gas, a reforming unit that generates hydrogen-rich reformed gas from raw fuel and supplies the reformed gas to the fuel cell, and a mixed raw fuel and water supply for reformed steam A flow rate of water for reforming steam of a fuel cell power generator comprising steam for generating steam from reformed steam water supplied by a pump and supplying the steam to the reforming unit. A water flow rate control method for reforming steam for controlling
The flow rate of the reforming steam water supplied to the steam generating unit is controlled by increasing or decreasing the voltage of the reforming steam water supply pump, and the temperature measured at the inlet of the reforming unit is determined by a predetermined load factor. A method for controlling the flow rate of water for reforming steam, characterized by maintaining a constant temperature . A fuel cell that generates power using hydrogen-rich reformed gas, a reforming unit that generates hydrogen-rich reformed gas from raw fuel and supplies the reformed gas to the fuel cell, and a mixed raw fuel and water supply for reformed steam Water flow control for reforming steam for controlling the flow rate of reforming steam water of a fuel cell power generation device comprising steam for generating steam from reforming steam water supplied by a pump and supplying the steam to the reforming unit A method,
  The voltage of the reforming steam water supply pump is set based on a predetermined load factor,
The reformed steam water supply pump based on the temperature measured inside the steam generating section or the temperature measured at the inlet of the reforming section when the steam generating section is installed inside the reforming section A method for controlling the flow rate of water for reforming steam, which corrects the voltage of the steam.

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