JP2005174644A - Fuel reforming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell system which can prevent a catalyst layer from excessive rise in temperature with superior responsiveness in the case the entrance gas composition may be deviated from a prescribed control range and the catalyst layer is in danger of excessive rise of temperature. <P>SOLUTION: In a fuel reforming system which is provided with a fuel reforming reactor that can reform a fuel gas into a reformed gas rich in hydrogen, a temperature measuring means 18 that either detects or estimates the temperature of a catalyst layer 12 of the reforming reactor 1 and a water injection means 15 that injects water onto the catalyst layer 12 are provided, and in the case the temperature of the catalyst layer exceeds or is estimated to exceed a prescribed value, water is injected to the catalyst layer by the water injection means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel reforming system provided with a reforming reactor.

In a fuel reforming system that reforms a fuel to obtain a hydrogen-rich reformed gas, generation of hydrogen from the fuel, removal of carbon monoxide, and the like are generally performed by a chemical reaction in a catalytic reactor.
In these reactors, the gas composition at the outlet changes depending on the temperature of the catalyst layer, and when the temperature rises excessively, the catalyst deteriorates. Therefore, it is necessary to keep the catalyst layer in a certain temperature range. In addition, since the catalyst layer temperature is greatly affected by the heat of reaction, it is important to appropriately control the inflowing gas composition that affects the catalyst layer temperature.

  For this reason, conventionally, the gas composition at the inlet, particularly the oxygen concentration, is detected and controlled, thereby controlling the temperature of the catalyst layer (see Patent Document 1).

  For example, a gasoline reforming reactor, which is an example of a catalytic reactor, generates hydrogen-rich reformed gas by catalytic action from gasoline vapor, water vapor, and air mixed at an appropriate ratio and temperature. At this time, partial oxidation reaction (exothermic reaction) with gasoline vapor and air and steam reforming reaction (endothermic reaction) with gasoline vapor and steam occur in the reforming reactor, and balance the heat balance of both reactions. The temperature is controlled by.

The reaction of the reactor is affected by the temperature of the catalyst layer, and the outlet gas composition of the reactor changes. Therefore, in order to obtain a reformed gas having a desired composition, it is necessary to keep the entire catalyst layer within a certain temperature range. In particular, if the temperature rises excessively, the problem arises that the catalyst deteriorates. Therefore, it is necessary to keep the maximum temperature below the allowable temperature of the reforming catalyst. For this reason, usually, gasoline vapor, water vapor, and air are controlled at a certain ratio so as to keep the catalyst layer temperature within a certain range.
JP 2002-179405 A

  However, although the method of controlling the catalyst layer temperature by this inlet gas composition can be controlled when the gas composition is relatively stable during steady operation or the like, the reformed gas flow rate can be controlled according to transient load fluctuations. When the air flow is changed, it is difficult to keep this ratio constant within a constant range when the air volume increases transiently and is outside the control range. Even if this is corrected based on the flow rate adjustment on the upstream side, Until it reaches the catalyst layer, a gas having a composition out of the control range continues to flow.

  Here, the oxidation reaction mainly affecting the temperature of the catalyst layer has a high reaction rate, and the temperature rapidly increases when oxygen is supplied excessively even for a short time. Furthermore, as described above, the catalytic reactor used in the fuel reforming system has a problem that its performance deteriorates when the temperature rises above a certain level, and once the deterioration occurs, the reactor itself needs to be replaced. The efficiency of the reforming system will be reduced and the maintenance cost will be increased.

  An object of the present invention is to provide a fuel cell system that prevents overheating of a catalyst layer with good responsiveness when an inlet gas composition is out of a control range and there is a risk of overheating of the catalyst layer. .

  The present invention provides a fuel reforming system including a reforming reactor that generates a hydrogen-rich reformed gas by reforming a fuel gas with a catalyst layer, and detects / estimates the temperature of the catalyst layer of the reforming reactor. And a water injection means for injecting water into the catalyst layer, and when the temperature of the catalyst layer exceeds a predetermined value or when it is estimated that the temperature exceeds a predetermined value, the water injection means To inject water into the catalyst layer.

  In the present invention, the temperature of the catalyst layer cools the catalyst layer efficiently and responsively by vaporization of water, prevents overheating of the catalyst layer during a transient, and prevents deterioration of the catalyst due to overheating. .

  The catalytic reactor of the present embodiment has a particularly high temperature among the components in a fuel reforming system that reforms gasoline as a fuel to obtain a hydrogen-rich reformed gas for use in power generation in a fuel cell. A gasoline reforming reactor is taken as an example. In addition, you may apply to the reforming system provided with the reforming reactor using the other fuels, such as methanol, ethanol, methane, and the reforming reactor.

  FIG. 1 shows the structure of a gasoline reforming reactor to which the present invention is applied.

  The gasoline reforming reactor 1 includes a cylindrical container 11 that houses a catalyst layer 12 that generates reformed gas from gasoline vapor or the like, and flange portions 13 and 14 are provided at both ends thereof. The flange portions 13 and 14 are connected to a duct (not shown) for supplying gasoline vapor or discharging reformed gas. The catalyst layer 12 housed inside is divided into two catalysts (upstream catalyst layer 12b and downstream catalyst layer 12c) at a predetermined distance L from the inlet 12a, and the divided catalyst layer 12b, Between 12c, the water injection pipe 15 which sprays water on the catalyst layer 12 for temperature adjustment is installed.

  Here, the distance L corresponds to the position where the temperature of the catalyst layer becomes the maximum temperature during the transient operation of the reforming reactor 1 in FIG. Actually, the position where the maximum temperature is reached fluctuates depending on the gasoline flow rate or the like, so it is desirable to install the water injection pipe 15 near the center of the range where the maximum temperature is reached. It should be noted that the region where the maximum temperature of the catalyst layer 12 is reached is the reaction gas (gasoline) in the vicinity of the downstream where the reaction gas (gasoline vapor) from the upstream of the catalyst layer starts to start reaction upon contact with the catalyst after flowing into the catalyst layer. It is in the vicinity of the place where the reaction of the vapor) starts to be carried out stably, and is only a predetermined distance downstream from the upstream end of the catalyst layer.

  The water injection pipe 15 is arranged facing the gas flow in the reforming reactor 1 and is formed in a spiral shape. Further, the water injection pipe 15 is provided with a plurality of water injection holes 16 penetrating in parallel with the gas flow direction. The water injection holes 16 are arranged so that water can be uniformly injected onto the cross section of the catalyst layer. In the vicinity of the position where the catalyst layer temperature becomes maximum, a temperature detecting means 18 for detecting the temperature of the catalyst layer 12 is installed via the fixing member 17 to detect the temperature of the catalyst layer 12.

  Gasoline vapor, water vapor, and air are heated and mixed from the upstream side of the reforming reactor 1 and supplied into the reforming reactor 1, and the hydrogen-rich reformed gas is generated by catalytic reaction while passing through the catalyst layer 12. And discharged downstream. On the other hand, water is supplied from a pure water tank (not shown) in the reforming system to one end of the water injection pipe 15 via the pump 20, passes through the pipe, and is discharged from the other end. At this time, since the water injection hole 16 is always open, the water passing therethrough can flow out toward the catalyst layer 12, but the throttle valve 9 is opened and flows through the water injection pipe 15 during steady operation. Since water is not particularly pressurized, the pressure difference with the catalyst layer 12 is small, and the supplied water hardly flows out to the catalyst layer 12 side, most of which passes through the pipe and is discharged from the other end. At this time, the amount of water vapor supplied from the upstream side of the reactor is set smaller than the amount required for the reforming reaction by the amount of water flowing out from the water injection pipe 15 to the catalyst layer 12. As a result, the total water supply amount can be suppressed to the same level as that of the conventional reforming reactor, so that an increase in the capacity of auxiliary equipment such as a pump accompanying an increase in the water amount can be avoided.

  Further, the relationship between the amount of water supplied to the water injection pipe 15, the length of the pipe, and the diameter of the pipe is such that the temperature of the water does not rise to the boiling point due to the amount of heat received from the reformed gas when the supplied water passes through the pipe. Set to. This is because it is necessary to always fill the pipe with liquid water so that water can be ejected from all the water ejection holes 16.

  In this embodiment, the catalyst layer 12 is divided into the front and the back to provide a certain space, and the water injection pipe 15 is installed in this space. The space is filled and the front and rear catalyst layers 12 are brought into contact with the water injection pipe 15. It is also possible to make it. In this way, although there is a disadvantage that spraying of water is difficult to spread, a certain cooling effect can be obtained by heat transfer even in a portion where the spray is not directly applied, and the reactor can be made more compact. Furthermore, when using a foam metal for the support | carrier of the catalyst layer 12, the space efficiency can be improved more compactly by casting the water injection pipe 15 when shape | molding this foam metal.

  FIG. 2 is a configuration diagram of a gasoline reforming system to which the present invention is applied.

  The reforming system includes three types of reactors, that is, a reforming reactor 1, a shift reactor 2, and a carbon monoxide removal reactor 3 from the upstream side. The reforming reactor 1 is supplied with steam that has passed through the water injection pipe 15 and the heat exchanger 4 and air that has passed through the heat exchanger 4 together with gasoline vapor. Gas is generated. Water supplied to the water injection pipe 15 of the fuel reformer 1 is pumped to the water injection pipe 15 by a water pump 20, and the amount of water is controlled by a flow control valve 7 and a throttle valve 9 installed in the water flow path 10. Is done.

  The air supplied to the heat exchanger 4 and the CO removal reactor 3 is controlled by flow control valves 5 and 6 installed in the air flow path, respectively. The water supplied to the shift reactor 2 is controlled by a flow control valve 8 installed in the water flow path 10. These control valves 5 to 9 and the water pump 20 are controlled by a controller (not shown). Note that the controller receives a detection signal from the temperature detection means 18 for detecting the temperature of the catalyst layer 12 described above.

  The reformed gas that has flowed out of the reforming reactor 1 contains high-concentration carbon monoxide (hereinafter referred to as CO). Therefore, in the shift reactor 2, water is added to the reformed gas and hydrogen and carbon dioxide are formed by the shift reaction. Convert to carbon. Downstream of that, air is further added to the reformed gas, and the remaining CO is oxidized by the CO removal reactor 3 to be converted into carbon dioxide, and the CO concentration in the reformed gas is reduced to a predetermined concentration or lower, for example, not shown. Supply to the fuel cell.

  Here, the steam supplied to the reforming reactor 1 is usually generated by heating water from the pure water tank by the heat exchanger 4, but in this embodiment, water from a pure water tank (not shown) is used. The water is once supplied to the water injection pipe 15 in the reforming reactor 1, passed through the water injection pipe 15, evaporated in the heat exchanger 4, and supplied to the reforming reactor 1 through the water channel 21. In addition, the amount of water supplied at this time is jetted in consideration of the leakage from the water jet pipe 15 as described above.

  For this reason, the temperature of the water supplied to the heat exchanger 4 is increased by the amount heated in the reforming reactor 1, and the temperature of water vapor at the inlet of the reforming reactor 1 is also increased by the amount of heat. . However, since this is offset by the heat lost when the water vapor contacts the water injection pipe 15, the outlet temperature does not change. In terms of heat balance, the heat transferred from the reformed gas to the water passing through the water injection pipe 15 is returned to the inlet of the reforming reactor 1 through the heat exchanger. System efficiency can be prevented from decreasing.

  On the other hand, as described above, the amount of water passing through the water injection pipe 15 is set to a flow rate at which water does not boil due to a temperature rise when water passes, and the normal water temperature is about 50 to 60 ° C. For this reason, in consideration of the specific heat and heat capacity of the mixed fluid of gasoline vapor / steam / air at the inlet of the reforming reactor 1, the allowance for increasing the inlet temperature of the reforming reactor 1 by the mixed fluid is about 10 to 20 ° C. There is no significant influence on the margin of allowance (about 200 ° C.) between the heat resistant temperature of the catalyst and the maximum temperature during steady operation.

  Next, an operation method of the water injection pipe 15 when the catalyst layer temperature of the fuel reformer 1 rises will be described with reference to the flowchart of FIG. This control is performed at predetermined intervals by the controller.

  First, in step 1, it is determined whether the system is in a steady operation state. If the system is in a steady operation state, the process proceeds to step 2, and the throttle valve 9 provided in the water flow path 10 on the outlet side of the water injection pipe 15 is fully opened to perform control. finish. On the other hand, if it is in a transient state, the process proceeds to Step 3.

  In the subsequent step 3, the temperature of the catalyst layer 12 is detected by using the temperature detecting means 18, the temperature 4 in the vicinity of the portion where the maximum temperature of the catalyst layer 12 is read, and the temperature change rate ΔT is calculated. When the absolute value of the temperature T read in step 4 is not less than the first predetermined value T1 ° C. and the rate of change ΔT is not less than a constant value ΔT1 ° C./second, if this condition is satisfied, step 5 The throttle valve 9 is throttled. Under this condition, if the rate of change in temperature at a certain temperature T1 is equal to or greater than ΔT1, it is estimated that the temperature is such that the catalyst layer 12 is deteriorated (second predetermined value T2). Therefore, water injection is performed. The throttle valve 9 may be throttled when the absolute value of the detected temperature of the catalyst layer 12 is equal to or higher than a second predetermined value T2 ° C. that is higher than T1.

  By restricting the throttle valve 9, the pressure in the water injection pipe 15 is increased and water is injected into the catalyst layer 12, and the increase in the temperature of the catalyst layer 12 is suppressed by the heat of vaporization. Prevent deterioration. At the same time, the flow control valve 5 may be closed to reduce the amount of air supplied to the reforming reactor 1 to suppress heat generation. Then, returning to step 4, the temperature determination of the catalyst layer 12 is repeated again. On the other hand, if the detected temperature T does not satisfy the above condition in step 4, the process returns to step 1 to repeat the temperature detection.

  By such control, it is possible to suppress overheating of the catalyst layer 12 and prevent the catalyst layer 12 from deteriorating. Further, when the opening of the throttle valve 9 is adjusted according to the catalyst layer temperature and the reformed gas flow rate when water is injected, the injection amount can be minimized, so that the catalyst layer 12 is excessively cooled. It is possible to suppress the deterioration of the reforming efficiency due to. On the contrary, when the overcooling of the catalyst layer 12 can be allowed, the opening degree adjustment is not necessary and the control can be simplified by replacing the throttle valve 9 with a simpler on-off valve. Note that this control assumes an unsteady (transient) time, but even in the steady state, when the temperature of the catalyst layer 12 may be excessively increased, the throttle valve 9 is throttled and the water injection pipe is Water may be sprayed from 15 to the catalyst layer 12.

  In the present embodiment, the water that has passed through the water injection pipe 15 is supplied to the reforming reactor 1, but it is also possible to supply this to the shift reactor 2 as shown in FIG. Further, the present invention can be applied to the CO removal reactor 3 in addition to the reforming reactor 1. Also in this case, the water that has passed through the water injection pipe 15 installed in the CO removal reactor 3 can be supplied to the reforming reactor 1 or the shift reactor 2.

  Therefore, according to the present invention, the temperature detection means 18 for detecting or estimating the temperature of the catalyst layer 12 of the catalyst reactor 1 and the water injection means 15 for injecting water to the catalyst layer are provided, and the temperature of the catalyst layer 12 is provided. When water exceeds a predetermined value, or when it is estimated that it exceeds the predetermined value, water is injected into the catalyst layer by the water injection means 15, so that the catalyst layer can be cooled efficiently and responsively by vaporization of water. I can do it.

  Further, the catalyst layer 12 is composed of a plurality of catalyst layers 12b and 12c divided at predetermined positions, and the water injection means directly cools the highest temperature portion of the catalyst layer 12, so that the catalyst layer is efficient and responsive. The layer can be cooled.

  Moreover, since the position where the temperature detection means 18 is installed is in the vicinity of the portion where the temperature of the catalyst layer 12 becomes the highest temperature, a space for installing the water injection means 15 in the catalyst layer of the catalyst reactor 1 is secured. Since it is not necessary, an increase in the volume of the catalytic reactor 1 can be suppressed.

  Since the water injection means 15 is composed of a tubular member having a plurality of holes 16 facing the fuel gas flow, water is injected from the many water injection holes 16 into the catalyst layer 12, so that water can be injected over a wide range. In addition, it is not necessary to secure a wide space for spreading the spray unlike a normal injection valve, and the expansion of the reactor volume can be suppressed. In addition, since the spray distance until reaching the catalyst layer 12 can be shortened, it is possible to suppress the vaporization before the spray reaches the catalyst layer 12 to reduce the cooling effect.

  The temperature detection means 18 is installed in the vicinity of the region where the maximum temperature of the catalytic reactor is reached, and when the detected temperature is the first predetermined temperature T1 or more and the change rate of the detected temperature is the predetermined value ΔT1 or more, Alternatively, when the detected temperature is equal to or higher than the second predetermined temperature T2 (> T1), the water injection means 15 injects water onto the catalyst layer 12, so that the temperature in the maximum temperature region can be detected and accurate water injection is performed. Can be controlled. Furthermore, by determining the necessity of water injection by combining the absolute temperature of the catalyst and the temperature change rate, it is possible to prevent the catalyst from being overheated more accurately.

  A pump 20 for supplying water to the water injection means 15 and a control valve 9 for controlling the flow of water downstream of the water injection means 15 are provided, and when the temperature of the catalyst layer 12 exceeds a predetermined value T2, or Since the control valve 9 is closed when estimated to exceed, water can be ejected from the large number of water ejection holes 16 to the catalyst layer 12 with a simple structure and good response. Further, by constantly flowing water, it becomes possible to suppress the vaporization of water in the pipe, and since the inside of the pipe can be always filled with liquid water, it is possible to inject with good response as necessary.

  Since the water supply means 21 for supplying the water flowing out from the water injection means 15 to the catalytic reactor 1 is provided, the reforming raw fuel is heated by the heat taken from the reformed gas by the water passing through the tubular water injection means 15. Since it can be used again for the reaction, it is possible to avoid a decrease in the efficiency of the system.

  The water supply means 21 calculates the difference between the reforming reaction raw fuel amount set according to the load of the catalyst reactor 1 and the amount of water that flows out from the water injection means 15 into the catalyst layer when the system is steady. Therefore, it is possible to supply the optimum amount of water necessary for the reforming reaction to the reforming reactor 1, so that it is not necessary to increase the capacity of auxiliary equipment such as a pump accompanying excessive water supply.

  Since the control valve 9 is an on / off valve, a dedicated flow rate adjusting means is not required, and can be controlled with a simple configuration.

  Since the control valve 9 is a flow rate control valve capable of adjusting the flow rate, the amount of water injection is minimized according to the degree of temperature rise of the catalyst layer 12, and the reforming efficiency by excessively cooling the catalyst layer 12 is improved. Deterioration can be suppressed.

  The reforming reactor to which the present invention is applied can prevent deterioration of the catalyst of the reforming reactor, and is useful for a fuel reforming fuel cell system.

1 is a structural diagram of a gasoline reforming reactor to which the present invention is applied. It is a figure explaining the structure of fuel reforming. It is a flowchart explaining the control content of this invention. It is another block diagram of the gasoline reforming system to which this invention is applied. It is a figure which shows the temperature distribution of a gasoline reforming reactor.

Explanation of symbols

1: Reforming reactor 2: Shift reactor 3: CO removal reactor 4: Heat exchanger 5: Air flow control valve 6: Air flow control valve 7: Water flow control valve 8: Water flow control valve 9: Throttle valve 10: water flow path 11: cylindrical container 12: catalyst layer 13: flange part 14: flange part 15: water injection pipe 16: water injection hole 17: fixing member 18: temperature detection means

Claims (11)

In a fuel reforming system including a reforming reactor that reforms a fuel gas to obtain a hydrogen-rich reformed gas,
Temperature detecting means for detecting or estimating the temperature of the catalyst layer of the reforming reactor;
Water injection means for injecting water to the catalyst layer,
When the temperature of the catalyst layer exceeds a predetermined value or when it is estimated that the temperature exceeds a predetermined value, water is injected into the catalyst layer by the water injection means.   2. The fuel reforming system according to claim 1, wherein the catalyst layer includes a plurality of catalyst layers divided at predetermined positions, and the water injection unit is provided between the plurality of catalyst layers. .   The fuel reforming system according to claim 2, wherein the predetermined position is near a portion where the temperature of the catalyst layer is the highest.   The fuel reforming system according to any one of claims 1 to 3, wherein the water injection means is formed of a tubular member provided with a plurality of holes parallel to the fuel gas flow.   The temperature detecting means is installed in the vicinity of the region where the maximum temperature of the reforming reactor is reached, and when the detected temperature is equal to or higher than the first predetermined temperature and the rising change rate of the detected temperature is equal to or higher than a predetermined value, The fuel reforming system according to claim 1, wherein the water injection unit injects water.   The temperature detection means is installed in the vicinity of the region where the maximum temperature of the reforming reactor is reached, and when the detected temperature is equal to or higher than a second predetermined temperature at which the catalyst layer deteriorates, the water injection means The fuel reforming system according to claim 1, wherein the fuel is reformed. A pump for supplying water to the water injection means;
A control valve for controlling the flow of water on the downstream side of the water injection means,
3. The fuel reforming system according to claim 1, wherein the control valve is closed when the temperature of the catalyst layer exceeds or is estimated to exceed a predetermined value. 4.   The fuel reforming system according to claim 2, further comprising water supply means for supplying water flowing out from the water injection means to the reforming reactor.   The water supply means supplies the reforming reactor with a difference between the amount of water set according to the load of the reforming reactor and the amount of water leaking into the catalyst layer from the water injection means when the system is stationary. The fuel reforming system according to claim 8.   The fuel reforming system according to claim 7, wherein the control valve is an on / off valve. The fuel reforming system according to claim 7, wherein the control valve is a flow rate control valve capable of adjusting a flow rate.

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