JP2006335623A - Reforming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reforming system capable of eliminating a large amount of raw material gas purge required after steam purge when stopping the reforming system. <P>SOLUTION: The reforming system is provided with a reformer 1 for generating a hydrogen-rich reformed gas by the steam-reforming reaction of a raw material-steam mixture, and a controller 14. The reformer 1 has a vessel 90 and a catalyst layer arranged therein, and a heating part 91 is arranged so as to surround the vessel 90. When stopping the operation of the reformer 1, the controller 14 controls heating by the heating part 91 so as to prevent dew condensation by cooling of the steam remaining in the vessel 90. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reforming system including a reformer that generates a hydrogen-rich reformed gas by a steam reforming reaction of a raw material-steam mixture, and a control device, and particularly when the reformer is stopped The present invention relates to a reforming system that prevents the occurrence of water vapor condensation.

Conventionally, a reformer that steam-reforms a raw material gas and steam in the presence of a steam reforming catalyst to generate a hydrogen-rich reformed gas is known. The hydrogen-rich reformed gas obtained by the reformer is suitably used as fuel for the fuel cell. As the source gas, hydrocarbons such as methane, aliphatic alcohols such as methanol, ethers such as dimethyl ether, city gas, and the like are used. The reaction formula of steam reforming when methane is used as the raw material gas in the reformer can be expressed as CH ₄ + 2H ₂ O → CO ₂ + 4H ₂ , and the preferred reforming reaction temperature is in the range of 650 to 750 ° C. .

  There are an external heating type and an internal heating type as a system for supplying heat necessary for the reaction of the steam reformer. The external heating type reforming apparatus is an apparatus that generates a reformed gas by providing a heating unit outside and reacting a raw material gas and water vapor with a heat source. The internal heating type reformer is provided with a partial oxidation reaction layer on the supply side (upstream side), and the steam reforming reaction layer disposed on the downstream side using the heat generated in the partial oxidation reaction layer is subjected to a steam reforming reaction. Heating to a temperature is performed, and a steam reforming reaction is performed in the heated steam reforming catalyst layer to generate a hydrogen-rich reformed gas.

The partial oxidation reaction can be represented by CH ₄ + 1 / 2O ₂ → CO + 2H ₂ , and the preferred partial oxidation reaction temperature is in the range of 250 ° C. or higher. As an improvement of the internal heating type reformer, a self-oxidation internal heating type steam reformer is described in Patent Document 1, for example. The reforming apparatus of Patent Document 1 includes a pre-reforming chamber and a main reforming chamber. The pre-reforming chamber is provided with a raw material-steam mixture supply unit, a reforming catalyst layer, and a discharge unit. Are provided with a supply portion communicating with the discharge portion, an oxygen-containing gas supply portion, a mixed catalyst layer in which the reforming catalyst and the oxidation catalyst are mixed, a shift catalyst layer, and a discharge portion.

  Then, when a mixture of raw material gas and steam (hereinafter referred to as raw material-steam mixture) is supplied to the pre-reforming chamber, a part of the raw material gas is reformed (pre-reformed) by the reforming catalyst layer, and the generated reforming is performed. A quality gas and an unreacted raw material-steam mixture flow out of the discharge section and are supplied to the main reforming chamber. In the mixed catalyst layer of the main reforming chamber, a reforming reaction (main reforming) is performed by heat generated by the oxidation reaction, and the resulting reformed gas then flows into the shift catalyst layer, where the reformed gas with reduced CO Is discharged from the discharge section.

  Conventionally, in both the external heating type reformer and the self-oxidation internal heating type reformer, when the system is stopped, in order to prevent catalyst deterioration due to carbon deposition or condensation in the reformer. The inside is purged with nitrogen gas. However, in a reformer that supplies reformed gas to a fuel cell for home use or a vehicle, it is not desirable to provide a nitrogen cylinder with a large weight and space.

  Therefore, for example, Patent Document 2 and Patent Document 3 propose a method of stopping the system in a system that does not perform nitrogen gas purge (nitrogen-less system). In the method of Patent Document 2, in the stop operation, the heat source supply to the heating unit of the reformer is stopped to terminate the reforming reaction, and the internal temperature is set to a predetermined value while continuing the supply of the raw material gas and water vapor to the reformer. The temperature is lowered to the value, and then the supply of water vapor is stopped, and then the inside residual moisture is purged with the raw material gas that is continuously supplied. In the stopping method of Patent Document 3, first, the supply of the raw material gas to the reformer is stopped in the stopping operation, and then the supply of water vapor is stopped when the internal temperature is lowered to a predetermined temperature. Is purged with the source gas.

JP 2004-175582 A JP 2000-95504 A JP 2002-151124 A

  In all of the conventional reforming system stop methods, the water vapor remaining in the apparatus after the water vapor purge is further removed by the raw material gas purge. That is, if the steam purging is left as it is, the water vapor remaining in the apparatus is condensed when the reforming apparatus is cooled, causing internal corrosion of the apparatus and catalyst deterioration. Therefore, in order to completely remove the water vapor remaining in the apparatus, the water vapor is completely removed by purging with a source gas at least 3 to 5 times the internal volume of the apparatus.

  However, this method of purging a large amount of source gas is not preferable because it reduces the energy efficiency of the reforming system. In particular, in the case of a reforming system that performs a system stop operation once a day, the amount of raw material gas consumed for purging annually becomes considerably large. In addition, when a large amount of source gas purge is performed, the internal temperature of the reformer rapidly decreases. For example, even in the case of a reforming system that performs a stop operation once a day, the internal temperature of the reformer is close to room temperature at the end of the stop period. May fall to.

  For this reason, there is a problem that the temperature raising time (and start-up time) of the reformer becomes long when the system is restarted. Furthermore, the heat energy consumption required for temperature rise also increases. Therefore, an object of the present invention is to solve these problems in the conventional reforming system, particularly various problems at the time of stopping.

  The present invention that solves the above-described problems is a reforming system that includes a reformer that generates a hydrogen-rich reformed gas by subjecting a raw material-steam mixture to a steam reforming reaction, and a control device. The reformer includes a container and a catalyst layer disposed therein, and a heating unit is disposed so as to surround the container. When the reformer stops operation, the control device The heating unit is controlled so as to prevent dew condensation of water vapor remaining in the water (claim 1).

  In the reforming system, the heating unit may be a heating method using an electric heater, and the outside of the electric heater may be covered with a heat insulating layer.

  In any one of the above reforming systems, the reforming apparatus is a self-oxidation internal heating type, and includes a pre-reforming chamber and a main reforming chamber in the container, and a reforming catalyst layer is disposed in the pre-reforming chamber, A mixed catalyst layer in which a reforming catalyst and an oxidation catalyst are mixed and a shift catalyst layer can be disposed in the reforming chamber (claim 3).

  Further, in any of the above reforming systems, the reformer includes a steam generating means for supplying steam to the reformer, and a fuel cell to which the reformed gas generated by the reformer is supplied, and the control device includes the fuel cell. Control can be performed to supply the reformed gas generated in the reformer as the fuel for the water vapor generating means when the engine is stopped.

  In the reforming system provided with the steam generating means, a load facility for consuming excess steam generated by the steam generating means can be provided.

  In the reforming system of the present invention described in claim 1, the heating unit is disposed so as to surround the container constituting the reforming apparatus, and when the reforming apparatus stops operation, the control apparatus remains in the container. The heating unit is controlled to prevent condensation of water vapor. According to this system, even if the steam used for the steam purge remains in the container when the reformer is stopped, the steam condensation in the container can be reliably prevented. There is no need to perform a large amount of source gas purge.

  Even if it is necessary to carry out the raw material gas purge after the water vapor purge, a small amount of the raw material gas purge sufficient to allow some water vapor to remain in the container is sufficient. There is no need to completely remove water vapor from the container by flowing ~ 5 times the raw material gas. For this reason, it is possible to avoid or significantly reduce the consumption of a large amount of raw material gas required for each stop operation in the conventional reforming system, and to shorten the time required for the stop operation of the reforming system. The surplus of the source gas used for purging is discharged from the container, but the surplus source gas can be recycled as fuel for the water vapor generating means.

  Furthermore, since the temperature inside the container when the reformer is stopped is considerably high, the heat energy required to keep the container warm from the surroundings is sufficient during the period when the reformer is stopped. The amount of energy is very small. Further, when the reforming system is restarted, the start-up time is shortened because the inside of the container of the reformer is maintained at a high temperature.

  In the above reforming system, as described in claim 2, when the heating unit is a heating system using an electric heater and the outside of the electric heater is covered with a heat insulating layer, accurate temperature control by a control device is performed. While being able to carry out, the heat dissipation to the outside can be reduced by the heat insulating layer.

In any one of the above reforming systems, as described in claim 3, the reforming apparatus is a self-oxidation internal heating type, and a pre-reforming chamber and a main reforming chamber are provided in the container, and the pre-reforming chamber is provided. If a reforming catalyst layer is placed in the reforming chamber, and a mixed catalyst layer and a shift catalyst layer in which the reforming catalyst and oxidation catalyst are mixed are placed in the main reforming chamber, all of the catalyst layers placed in the container are condensed with water vapor. Therefore, the catalyst can be reliably prevented from being deteriorated. Further, in the conventional reforming system, a long time is required for raising the temperature of the shift catalyst layer to a predetermined level at the time of restarting. However, according to the above configuration, the time can be remarkably shortened.
Furthermore, in any one of the above reforming systems, as described in claim 4, a steam generating means for supplying steam to the reformer, and a fuel cell to which the reformed gas generated by the reformer is supplied. And when the control device is configured to perform control to supply the reformed gas generated by the reformer as fuel for the water vapor generating means when the fuel cell is stopped, the reforming is performed when the fuel cell is stopped. Excess reformed gas flowing out of the reformed gas from the apparatus can be used for steam generation without being discarded.

  In the above reforming system, as described in claim 5, when providing a load facility that consumes surplus steam generated by the steam generating means, surplus steam can be effectively utilized.

  Next, the best mode for carrying out the present invention will be described. FIG. 1 is a process flow diagram of the reforming system of the present invention. In the present embodiment, a self-oxidation internal heating type reformer is used as the reformer constituting the reforming system.

  In FIG. 1, the water vapor generating means 2 includes a combustion section 2a and a suction mixing means 6. The combustion section 2a is provided with a burner (not shown) for burning the air-fuel mixture supplied from the suction mixing means 6. It is done. The suction mixing means 6 is composed of, for example, an ejector, details of which will be described later.

  A pipe 108 for supplying water or pure water from the water tank 10 and a pipe 109 a for supplying water vapor to the mixing means 4 are connected to the water vapor generating means 2. Note that the mixing means 4 can be constituted by, for example, a confluence pipe having a slightly larger diameter than the pipe 109a. The mixing means 4 can also be constituted by an ejector similar to the suction mixing means 6. The pipe 108 is provided with a flow rate adjusting valve 32, and the pipe 109a is provided with a flow rate adjusting valve 39. These flow rate adjusting valves can be remotely operated, for example, driven pneumatically, hydraulically, or electrically, and are controlled by the control device 14. (When it is described as a flow control valve below, it is not specified, but it can be remotely operated in the same manner and controlled by the control device 14.) However, the flow control valves 32 and 39 are remote controls such as electromagnetic valves. It may be a possible on-off valve (when it is described as an on-off valve below, it is not particularly specified, but can be remotely operated in the same manner and controlled by the control device 14). Further, instead of providing the flow rate adjustment valve 32 or the flow rate adjustment valve 33, a pump may be provided in the pipe 108 or 109a, and the rotation speed operation or start-stop operation of the pump may be performed by the control device 14.

  Further, the water vapor generating means 2 is provided with a water level detecting means 40 for detecting the water level of the water reservoir (water drum) and a pressure detector 41 for detecting the pressure of the water vapor generated in the water reservoir, and is proportional to each detected value. An electrical signal (detection signal) to be input is input to the control device 14.

  The control device 14 receives the detection values of the water level detection means 40 and the pressure detection means 41 or an operation command from another operation panel or the like to control each flow rate adjusting valve and the like, and further the reforming system which is a characteristic part of the present invention. Perform stop control. The control device 14 is constituted by a computer device, for example. The computer device includes a CPU (Central Processing Unit) that performs various control operations, an operating system (OS), a storage unit such as a ROM or RAM that stores a control program, a keyboard, a mouse, or an input unit such as an operation panel. Further, an output unit such as a display or a printer is added if necessary. The control device 14 may be installed at a location away from the system, and the control may be performed using a communication line.

  A pipe 113 for discharging combustion exhaust gas is connected to the combustion section 2a. The pipe 113 communicates with the pipe 114 through the heat exchanging means 13, and the tip end of the pipe 114 opens to the outside of the system. The heat exchange means 13 is connected to a pipe 101a for supplying gas fuel such as anode exhaust gas and reformed gas of the fuel cell, or liquid fuel. The pipe 101a communicates with the pipe 101b via the heat exchange means 13, and the pipe 101b. Is connected to the suction mixing means 6.

  A pipe 112 is further connected to the combustion unit 2a. The pipe 112 communicates with the pipe 102 extending from the pressurized air supply system 7 provided with an air compressor through the flow rate adjusting valve 34. The air supplied by the pipe 112 is used as secondary air for the combustion section 2a or as purge air when the operation of the combustion section 2a is started. That is, in response to the operation start signal (start signal), a control signal for opening the flow rate adjustment valve 34 is output from the control device 14 for a set time, whereby the inside of the combustion section 2a is purged with air.

  A raw material gas supply pipe 111 extending from the raw material supply system 8 having a storage tank is connected to the inlet side of the desulfurization apparatus 9, and a pipe 103 through which the desulfurized raw material gas flows out is connected to the outlet side of the desulfurization apparatus 9. The The pipe 103 is provided with a flow control valve 31 that can be remotely operated. The downstream side of the flow control valve 31 communicates with the pipe 109 through the heat exchanging means 13, and the tip of the pipe 109 is connected to the mixing means 4. .

  Further, a pipe 102b for supplying combustion air is connected to the suction mixing means 6, and the pipe 102b communicates with the pipe 102a through a heat exchange means 12 described later. The pipe 102 a is provided with a flow rate adjustment valve 37, and the tip of the pipe 102 a communicates with the pressurized air supply system 7. Further, a pipe 111a branched from the raw material gas supply pipe 111 is connected to the fuel supply pipe 101a, and a flow control valve 33a capable of being remotely operated is provided in the pipe 111a.

  Connected to the reformer 1 are a pipe 104 for supplying a raw material-steam mixture flowing out from the mixing means 4 and a pipe 102d for supplying a pressurized oxygen-containing gas such as pressurized air. The pipe 102d communicates with the pipe 102c provided with the flow rate adjusting valve 36 via the heat exchange means 12, and the tip end of the pipe 102c is connected to the pressurized air supply system 7. A temperature detecting means 42 and a pressure detecting means 43 are provided in the upper part of the reformer 1, and their measurement signals are input to the control device 14. And the heating part 91 is arrange | positioned so that the circumference | surroundings of the reformer 1 may be covered.

  Further, a preheater 80 is connected to the reformer 1. The preheater 80 is provided to quickly raise the reforming apparatus 1 to the reforming reaction temperature when the system is started up or to reduce the reforming catalyst constituting the mixed catalyst layer. The preheater 80 has an electric heater disposed therein and is filled with an oxidation catalyst such as platinum (Pt) or palladium (Pd). A pipe 81 for supplying the raw material-water vapor mixture from the mixing means 4 and a pipe 82 for supplying an oxygen-containing gas from the pressurized air supply system 7 are connected to the preheater 80, and the pipes 81 and 82 have flow rates respectively. Regulating valves 83 and 84 are provided. The flow rate adjustment valve 83 may be an on-off valve.

  In the preheater 80, a part of the supplied raw material gas reacts with oxygen in the presence of an oxidation catalyst by combustion and is partially oxidized to generate hydrogen, and the remaining raw material-steam mixture is heated by the oxidation heat. Then, a mixture of the high-temperature raw material gas, the oxygen-containing gas and the generated hydrogen gas is supplied from the pipe 85 to the reformer 1.

  A reformed gas discharge pipe 105 is connected to the discharge section 69 of the reformer 1, the pipe 105 is connected to the pipe 106 through the heat exchange means 12, and the tip of the pipe 106 is mixed to mix oxidizing air. Connected to means 5. The outlet side of the mixing means 5 is connected to the CO reduction means 3, and the outlet pipe 107 is branched into a pipe 301 to the fuel cell 300 and a pipe 302 to the suction mixing means 6, and the flow rate is adjusted to the pipes 301 and 302, respectively. Flow path switching valves 303 and 304 configured with valves or on-off valves are provided.

  The oxidation catalyst of the CO reduction means 3 is, for example, a pellet type in which a noble metal catalyst such as Pt or Pd is supported on ceramic particles, or a metal honeycomb structure or a ceramic honeycomb structure on which a noble metal catalyst such as Pt or Pd is supported. Can be used. The mixing means 5 for the CO reduction means 3 is connected to a pressurized air supply pipe 110 provided with a flow rate adjusting valve 38, and the tip of the pipe 110 is connected to the pressurized air supply system 7. As will be described later, the reforming means 1 is provided with a preliminary reforming chamber 61a and a main reforming chamber 62a (see FIG. 3) communicating therewith, and the temperature of the mixed catalyst layer 72a provided in the main reforming chamber 62a is It is detected by the temperature detecting means 42.

  FIG. 2 shows an example of the structure of the suction mixing means 6 that supplies the fuel-air mixture to the combustion section 2a. In the present embodiment, the suction mixing means 6 is composed of an ejector 20. The ejector 20 includes a fixed portion 21, an internal nozzle structure 22 and an external nozzle structure 23 extending from the fixed portion 21, and openings 24 and 25 and a throttle portion 26 are provided in the external nozzle structure 23.

  Next, the operation of the ejector 20 will be described. When the air flow as the main fluid is supplied to the internal nozzle structure 22 as shown by the arrow, the throttle portion 26 is decompressed by the venturi effect of the air flow. When the fuel gas, which is a sub-fluid, is supplied from the opening 24 as shown by the arrow, the fuel gas is sucked and uniformly mixed with the air flow and ejected from the opening 25. Accordingly, the fuel gas is uniformly mixed with air without using special power means, and a homogeneous fuel-air mixture is obtained.

  FIG. 3 is a diagram showing a specific configuration of the reformer 1. The reformer 1 includes a vertically long outer cylinder 61 whose cross section is substantially rectangular and whose top and bottom are closed, and two inner cylinders 62 whose cross section is substantially rectangular and whose vertically long shape is double. A container 90 of the quality device 1 is constructed. And the heating part 91 is arrange | positioned so that the outer surface and bottom face of the container 90 may be covered. The heating unit 91 is preferably an electric heating method using an electric heater, but may be a fluid heating method using a pipe through which a heating fluid is circulated. In any case, it is desirable that the heating unit has a structure in which the outside is covered with a heat insulating layer 91a such as glass wool.

  The two inner cylinders 62 are disposed inside the outer cylinder 61. A space between the outer cylinder 61 and the outer side of the inner cylinder 62 and an inner space of the inner cylinder 62 communicate with each other to form a preliminary reforming chamber 61 a, and a main reforming chamber 62 a is formed between the two inner cylinders 62. Is done. The side wall of the inner cylinder 62 is made of a metal such as stainless steel having corrosion resistance and good heat conductivity. Therefore, the preliminary reforming chamber 61a and the main reforming chamber 62a are partitioned by a partition wall 62b having good heat conductivity. It is in a state.

  A supply unit 68 for supplying the raw material-steam mixture is provided at one end (lower side in FIG. 3) of the pre-reforming chamber 61a, and a discharge unit 68a is provided at the other end (upper side in FIG. 3). Further, support plates 73a, 73c, 73e having a large number of minute through portions are provided in the preliminary reforming chamber 61a in this order from the discharge portion 68a side, and reforming that performs steam reforming between the support plates 73a and 73c. The catalyst layer 71a is filled, and the heat transfer particle layer 71b is filled between the support plates 73c and 73e.

  A supply portion 69a communicating with the discharge portion 68a of the preliminary reforming chamber 61a is provided at one end (upper side in FIG. 3) of the main reforming chamber 62a, and an oxygen-containing gas such as air is introduced into the supply portion 69a. The manifolds 64 and 65 of the oxygen-containing gas introduction part 63 to be communicated with each other. A discharge portion 69 having a manifold 66 is provided at the other end (lower side in FIG. 3) of the main reforming chamber 62a.

  Furthermore, support plates 73a, 73b, 73c, 73d, 73e having a large number of minute through portions are provided in the main reforming chamber 62a in order from the supply portion 69a side. In the illustrated example, the support plate 73c provided in the preliminary reforming chamber 61a has the same height as the support plate 73c provided in the main reforming chamber 62a, but it is also possible to provide both at different heights.

  The mixed catalyst layer 72a in which the reforming catalyst and the oxidation catalyst are mixed is filled between the support plates 73a and 73b of the main reforming chamber 62a, and the heat transfer particle layer 72b is filled between the support plates 73b and 73c. The high temperature shift catalyst layer 72c is filled between 73c and 73d, and the low temperature shift catalyst layer 72d is filled between the support plates 73d and 73e. The shift catalyst layer 72e is constituted by both the high temperature shift catalyst layer 72c and the low temperature shift catalyst layer 72d. The peripheral wall existing between the support plates 73a and 73b arranged in the main reforming chamber 62a is a heat insulating wall 70, and the oxidation reaction heat by the oxidation catalyst is directly transmitted from the portion to the pre-reforming chamber 61a side. It is preventing.

The reforming catalyst layer 71a filled in the preliminary reforming chamber 61a is a catalyst layer for steam reforming the raw material gas, and can specify a Ni-based reforming reaction catalyst such as NiO—SiO ₂ · Al ₂ O _3. . A reforming catalyst such as WO ₂ —SiO ₂ · Al ₂ O ₃ or NiO—WO ₂ · SiO ₂ · Al ₂ O ₃ can also be used.

  As the reforming catalyst which is a main component constituting the mixed catalyst layer 72a, the same reforming catalyst as that filled in the preliminary reforming chamber 61a can be used. The amount of the reforming catalyst used is a value sufficient to complete the steam reforming reaction while the raw material-steam mixture passes through the mixed catalyst layer 72a, but the value varies depending on the type of raw material gas used. Therefore, it is desirable to determine the optimum range by experiments or the like.

  The oxidation catalyst uniformly dispersed in the mixed catalyst layer 72a partially oxidizes the raw material gas in the raw material-steam mixture and raises the temperature to a temperature necessary for the steam reforming reaction. As described above, platinum (Pt) Or a noble metal catalyst such as palladium (Pd) can be used. The mixing ratio of the oxidation catalyst to the reforming catalyst is selected in the range of about 1 to 5% depending on the type of raw material gas to be steam reformed. For example, when methane is used as the raw material gas, it is desirable that the mixing ratio be about 3% ± 2%, and for methanol, the mixing ratio is about 2% ± 1%.

  The heat transfer particle layer 71b in the pre-reforming chamber 61a and the heat transfer particle layer 72b in the main reforming chamber 62a efficiently transfer the heat energy of the main reforming chamber 62a to the pre-reforming chamber 61a via the partition wall 62b. Provided. That is, the heat transfer particle layer 72b filled in the main reforming chamber 62a heats the portion of the reforming catalyst layer 71a that fills the pre-reforming chamber 61a with the thermal energy of the high temperature effluent from the mixed catalyst layer 72a, and preliminarily reforms. The heat transfer particle layer 71b filled in the chamber 61a heats the raw material-steam mixture flowing from the supply unit 68 with the thermal energy from the shift catalyst layer 72e, which is an exothermic reaction unit, and preliminarily reforms both by transferring the thermal energy. The temperature in the reforming catalyst layer 71a portion of the chamber 61a is raised to the steam reforming reaction temperature. The heat transfer particles constituting the heat transfer particle layer 71b and the heat transfer particle layer 72b can be formed of ceramic particles such as alumina or silicon carbide or a metal honeycomb structure.

  The shift catalyst layer 72e constituted by both the high temperature shift catalyst layer 72c and the low temperature shift catalyst layer 72d oxidizes carbon monoxide contained in the reformed gas to generate hydrogen. That is, a mixture of water vapor and carbon monoxide remaining in the reformed gas is shift-converted into hydrogen and carbon dioxide gas in the presence of a shift catalyst to generate hydrogen, and the hydrogen concentration in the reformed gas is further increased, resulting in higher monoxide. Reduce the carbon concentration accordingly.

As a shift catalyst for forming the high temperature shift catalyst layer 72c and the low temperature shift catalyst layer 72d, CuO—ZnO ₂ , Fe ₂ O ₃ , Fe ₃ O _4, a mixture of copper oxides, or the like can be used. However, when the reaction is carried out at 400 ° C. or higher, it is desirable to use Cr ₂ O ₃ .

  In the plurality of partition walls 62b, the end portions on the supply portion 68 and discharge portion 69 side are connected to each other at the portion a to be fixed ends, and the opposite end portions are not connected to each other and become free ends. ing. For this reason, when a difference in thermal expansion occurs between the pre-reforming chamber 61a and the main reforming chamber 62a that are brought to a high temperature state by the reforming reaction, particularly when the main reforming chamber 62a has a large thermal expansion, the main reforming due to the thermal expansion occurs. The expansion of the chamber 62a can be absorbed by the free end and the occurrence of distortion can be prevented.

Next, a normal operation method in the steam reforming system of FIG. 1 will be described.
(Water vapor generation operation)
When the water level of the water reservoir (water drum) of the water vapor generating means 2 is detected by the water level detecting means 40 and the detected value is smaller than a preset value, a control signal for opening the flow rate adjusting valve 32 is output from the control device 14. Thus, the water level of the water reservoir is always maintained within a predetermined range. The control device 14 outputs a control signal for starting the burner of the combustion section 2a of the steam generating means 2, and controls the flow rate adjusting valves 37, 33 (or 33a) to supply a predetermined flow rate of the fuel-air mixture to the combustion section 2a. Supply. That is, the control device 14 controls the flow rate adjusting valve 37 of the pipe 102b for flowing the pressurized air to the suction mixing unit 6 so that the water vapor pressure detection value from the pressure detection unit 41 becomes a preset value. Note that the flow rate adjustment valve 39 is an on-off valve, which is controlled to be fully opened by the control device 14 during operation, and the required amount of water vapor is adjusted by controlling the amount of fuel and air in the combustion section 2a from the control device 14. It can also comprise.

  When the controlled air flow flows into the suction mixing means 6, the fuel is sucked at a predetermined rate with respect to the flow rate, and both are uniformly mixed. Therefore, it is not necessary to provide a boosting means such as a special power unit in the fuel supply system, and there is no region where the temperature is locally high in the combustion section 2a due to uniform mixing, and the generation of NOx is kept low by good combustion progress. And environmentally friendly combustion exhaust gas can be discharged.

  When the suction mixing means 6 is used, the control device 14 may control the valve opening degree of the flow rate adjustment valve 33 so that the maximum allowable flow rate of fuel can be set. It can also be controlled to be approximately proportional to the flow rate. Further, by setting the pressure of the pressurized air supplied to the suction mixing means 6 to a value slightly higher than the normal pressure, for example, about 0.02 MPa, a negative pressure at a level at which the fuel gas can be sucked into the suction mixing means 6. Can be generated.

  By opening the flow rate adjusting valve 33, gas fuel such as anode exhaust gas of the fuel cell, city gas, propane gas, natural gas, or liquid fuel such as kerosene is supplied to the suction mixing means 6 from the pipe 101 a. Further, by opening the flow control valve 33a, gas fuel is supplied from the pipe 111a such as methane, ethane, propane and other hydrocarbons, methanol and other alcohols, dimethyl ether and other fuels, and anode gas of fuel cells containing residual hydrogen. Can be supplied to the suction mixing means 6 as well.

  The selection of the flow rate adjusting valves 33 and 33a can be performed by a fuel selection command to the control device 14, for example. The combustion exhaust gas from the combustion section 2a is supplied from the pipe 113 to the heat exchange means 13, cooled there, and then discharged to the outside through the pipe 114. On the other hand, the fuel supplied from the pipe 101 a or 111 a is heated by the heat exchange means 13 and then supplied to the suction mixing means 6.

(Raw material-steam mixing operation)
The water vapor generated by the water vapor generating means 2 is adjusted in flow rate by the flow rate adjusting valve 39 and supplied to the mixing means 4, and the flow rate adjustment is performed by a control signal from the control device 14. That is, when the set value of the raw material supply flow rate to the reforming unit 1 is input from the input means provided in the control device 14, the control device 14 outputs a control signal for maintaining a predetermined valve opening degree to the flow rate adjustment valve 39. A suitable mixing ratio of the raw material gas and water vapor is based on the carbon C contained in the raw material gas, for example, in the case of hydrocarbon, a range of H ₂ O / C = 2.5 to 3.5 is preferable, In the case of an aliphatic alcohol, a range of H ₂ O / C = 2 to 3 is preferable. The flow control valve 39 is controlled by the control device 14 so that the necessary water vapor is generated.

  As described above, the mixing means 4 includes a fuel cell anode exhaust gas containing hydrocarbons such as methane, ethane, and propane, alcohols such as methanol, ethers such as dimethyl ether, or residual hydrogen, in a predetermined ratio with respect to the water vapor flow rate. Is mixed with a source gas such as city gas, propane gas or natural gas from the pipe 109. A uniform raw material-steam mixture flows out of the mixing means 4 and is supplied to the reforming means 1.

  The raw material gas supplied from the raw material supply system 8 flows into the pipe 109 through the pipe 111, the desulfurization device 9, the flow rate adjusting valve 31 and the heat exchange means 13. The source gas is supplied to the mixing unit 4 after its maximum allowable flow rate is limited by a flow rate adjusting valve 31 maintained at a predetermined opening by a control signal from the control device 14 and heated to a predetermined temperature by the heat exchange unit 13. The

(Reforming reaction operation)
As described above, the raw material-steam mixture flowing out from the mixing unit 4 to the pipe 104 flows into the preliminary reforming chamber 61a through the supply unit 68 (FIG. 3) of the reforming unit 1. During normal operation, the temperature of the heat transfer particle layer 71b charged in the preliminary reforming chamber 61a is raised by the heat energy transferred from the main reforming chamber 62a through the partition wall 62b. The inflowing raw material-water vapor mixture is heated to the reforming reaction temperature while passing through the heat transfer particle layer 71b.

  The raw material-steam mixture that has reached the reforming reaction temperature then passes through the reforming catalyst layer 71a, during which part of the raw material-steam mixture undergoes a steam reforming reaction and is converted into a hydrogen-rich reformed gas. In particular, high carbon hydrocarbons such as propane are converted to methane in high yield. And the remaining raw material-steam mixture which did not react with the reformed gas containing hydrogen is discharged | emitted integrally from the discharge part 68a.

  The reformed gas and the raw material-steam mixture discharged from the discharge portion 68a of the preliminary reforming chamber 61a flow into the mixed catalyst layer 72a from the supply portion 69a of the main reforming chamber 62a. At that time, air is supplied as oxygen-containing gas from the oxygen-containing gas introduction portion 63 to the supply portion 69a, and the air is mixed into the raw material-water vapor mixture flowing into the mixed catalyst layer 72a.

  The flow rate of air supplied from the oxygen-containing gas introduction unit 63 is adjusted by a flow rate adjustment valve 36 controlled by the control device 14. That is, control information of the flow rate adjusting valve 35 for adjusting the water vapor flow rate is stored in the control device 14, and the water vapor flow rate is correlated with the flow rate of the raw material-water vapor mixture. And an optimal control signal is output to the flow rate adjusting valve 36.

  As described above, the raw material-steam mixture flows into the mixed catalyst layer 72a, but a part of the raw material gas constituting the raw material-steam mixture reacts with oxygen in the flowing air and is oxidized (partial oxidation), The raw material-steam mixture is heated to the level necessary for the reforming reaction by the heat of reaction. That is, auto-oxidation heating is performed. The average temperature in the mixed catalyst layer 72a is maintained at a temperature suitable for the steam reforming reaction, for example, about 650 ° C. to 750 ° C., and typically around 700 ° C.

  On the other hand, it is important that the temperature in the mixed catalyst layer 72a is in a range suitable for the steam reforming reaction, and at the same time, the temperature at the boundary with the downstream heat transfer particle layer 72b can be maintained at a predetermined level. Management is also important. For example, the average temperature in the mixed catalyst layer 72a is controlled by controlling the oxygen-containing gas for oxidation to an appropriate amount so that the temperature at the boundary with the heat transfer particle layer 72b is 650 ° C. or higher, preferably 700 ° C. or higher. If managed, the temperature of the heat transfer particle layer 71b in the preliminary reforming chamber 61a can be maintained at least 500 ° C. or more, thereby sufficiently promoting the steam reforming reaction in the preliminary reforming chamber 61a.

  The hydrogen-rich reformed gas flows from the mixed catalyst layer 72a into the heat transfer particle layer 72b on the downstream side, and the temperature is desirably 650 ° C. or higher, preferably 700 ° C. or higher. As described above, while the introduced reformed gas passes through the heat transfer particle layer 72b, a part of the sensible heat moves to the heat transfer particle layer 71b of the preliminary reforming chamber 61a through the partition wall 62b and is suitably set. In this case, the reformed gas temperature when flowing from the heat transfer particle layer 72b into the high temperature shift catalyst layer 72c on the downstream side can be lowered to 500 ° C. or less suitable for the shift reaction.

  Most of the carbon monoxide contained in the reformed gas that has flowed into the high temperature shift catalyst layer 72c is converted into carbon dioxide by the shift reaction. That is, as described above, water vapor and carbon monoxide remaining in the reformed gas are shift-converted into hydrogen and carbon dioxide gas in the presence of the shift catalyst to generate hydrogen.

  Next, the reformed gas flows from the high temperature shift catalyst layer 72c to the downstream low temperature shift catalyst layer 72d, where most of the remaining carbon monoxide is converted to hydrogen. By performing the two-stage shift reaction in this manner, carbon monoxide can be sufficiently reduced and more hydrogen can be generated. The shift reaction in the high temperature shift catalyst layer 72c and the low temperature shift catalyst layer 72d is an exothermic reaction, and part of the reaction heat moves to the heat transfer particle layer 71b in the auxiliary reforming chamber 61a through the partition wall 62b as described above.

  The reformed gas that has passed through the low temperature shift catalyst layer 72d flows out from the discharge part 69 of the main reforming chamber 62a into the pipe 105 (FIG. 1). However, the temperature of the reformed gas is usually as high as about 180 ° C. Then, after cooling by the heat exchanging means 12, it is made to flow into the mixing means 5. The reformed gas that has flowed into the mixing unit 5 is mixed with the air supplied from the pipe 110 and then flows into the CO reduction unit 3. The carbon monoxide remaining in the reformed gas is reduced to a very small level (for example, 1 to 10 ppm) in the CO reduction means 3 and supplied to the fuel cell 300 through the pipe 107 and the pipe 303.

  The flow rate of the air supplied from the pipe 110 to the mixing means 5 is adjusted by changing the opening degree of the flow rate adjusting valve 38 by a control signal from the control device 14. That is, the control device 14 stores the control information of the flow rate adjusting valve 35 for adjusting the water vapor flow rate, and the water vapor flow rate is correlated with the reformed gas flow rate, so that the required air flow rate is calculated from the control information. Thus, an appropriate control signal is output to the flow rate adjustment valve 38.

  4 is a front view illustrating the heating unit 91 in the reformer 1 shown in FIG. 1, and FIG. 5 is a bottom view thereof. The heating unit 91 of the present embodiment is an electric heating method, and an electric heater 92 such as a nichrome wire is spirally wound on the side surface of the reformer 1 from the lower end portion to a height of about 2/3, and further on the bottom surface. The linear electric heater 92 is two-dimensionally arranged.

  In order to form the heating unit 91, first, the electric heater 92 is fixed to the outer peripheral surface and the bottom surface of the container 90 (outer cylinder 61) of the reformer 1 at a predetermined interval by the fixture 93. The fixture 93 is made of, for example, a thin stainless steel plate processed into a rectangular shape, and is pressed from above the electric heater 92 and fixed to the outside of the container 90 by spot welding, for example. Next, in a state where the electric heater 92 is fixed to the outer peripheral surface and the bottom surface of the container 90, the heating portion 91 is completed by fixing the heat insulating layer 91a to the entire outside of the container 90.

  In the embodiment shown in FIG. 4 (FIG. 5), the electric heater 92 on the outer peripheral surface of the container 90 is at a height from the lower end portion to the middle portion of the outer cylinder 61 (for example, from the lower end portion to the vicinity of the upper end of the shift catalyst layer 72e). Although provided, the electric heater 92 on the outer peripheral surface can be provided up to the upper end of the container 90. Thus, even if the electric heater 92 is provided up to the middle portion of the outer peripheral surface of the container 90, the effect of keeping the container 90 warm can be sufficiently exhibited. That is, the entire outside of the container 90 is covered with the heat insulating layer 91a, and the fluid such as water vapor in the container 1 heated by the electric heater 92 circulates in the container 90 in the vertical direction by the convection action. The temperature inside is kept uniform.

  Next, the method for stopping the reforming system and the heat insulation control of the container 90 according to the present invention will be described with reference to the flowchart of FIG. In the following description, the reformed gas generated by the reformer 1 is supplied to the fuel cell 300. First, when a stop signal from the control means of the fuel cell 300 is transmitted to the control device 14, the control device 14 performs control to close the flow rate adjustment valve 36 and stop the supply of the oxygen-containing gas to the reforming device 1 ( Step S1). However, since the supply of the raw material-steam mixture to the reformer 1 is not stopped, the steam reforming reaction continues.

  When the supply of the oxygen-containing gas to the reformer 1 is stopped, the generation of oxidation heat in the mixed catalyst layer 72a is stopped, and the steam reforming reaction is an endothermic reaction. Therefore, the steam reforming catalyst layer 71a shown in FIG. The catalyst layer 72b rapidly decreases in temperature (accelerated temperature decrease) (step S2). The reformer 1 is provided with the temperature detection means 42 as described above, and the controller 14 sets the temperature detection value to a preset value, that is, the temperature at which the interior of the reformer 1 shifts to the steam purge ( For example, it is determined whether or not the temperature has decreased to about 470 ° C. (step S3).

  When the inside of the reformer 1 is lowered to the above temperature, the controller 14 closes the flow rate adjustment valve 31 and stops the supply of the raw material gas to the reformer 1 (step S4). By this operation, the reformer 1 shifts to the steam purge, and the raw material gas and the reformed gas remaining in the container 90 are discharged from the pipe 105. Instead of determining the transition timing to the water vapor purge by detecting the temperature, it is also possible to obtain the time for cooling to that temperature by an experiment and set the time (for example, about 3 minutes) in the control device 14 to determine it. . In that case, when the set time is reached, the control device 14 closes the flow rate adjustment valve 31 and stops the supply of the raw material gas to the reforming device 1.

  Although the internal temperature of the reformer 1 gradually decreases due to the steam purge, the controller 14 determines whether or not the temperature has decreased to a temperature at which no carbon is deposited, for example, about 400 ° C., preferably about 300 ° C. (step S5). When the temperature is reached, the controller 14 closes the regulating valve 39 in step S6 and stops the steam purge of the reformer 1. Since the raw material gas in the container 90 is discharged to the outside by this steam purge, the steam purge can be stopped as described above even if the container 90 is in a temperature region where carbon is deposited. The portion where carbon is deposited in the reformer 1 is the portion where the highest temperature continues during the stopping operation, and is generally the portion of the mixed catalyst layer 72a. Therefore, it is desirable that the temperature detecting means 42 shown in FIG. 1 detect the temperature of the portion.

  After the steam purge is stopped, the temperature inside the container 1 is lowered by natural cooling as it is, so that the temperature of the steam filling the inside is condensed or near (condensation temperature or a temperature slightly higher than that in view of safety, for example, around 120 ° C. ), The control device 14 controls the heating unit 91 (in the case of the electric heating method, controls the amount of current supplied to the electric heater) to keep the container 90 warm from the outside (step S7). In the reformer 1, the portion where condensation occurs first is the portion where the temperature becomes the earliest during the stop operation, and it is desirable to provide temperature control means for monitoring condensation in this portion. The internal pressure of the container 90 may drop due to a temperature drop after the steam purge, but in that case, a small amount of source gas may be sealed so as to maintain the pressure when the temperature in the container 90 becomes lower than the temperature at which carbon does not precipitate. it can.

  The temperature control of the heating unit 91 is continued during the stop period of the reforming system. And if the restart signal (step S8) of a reforming system is given, heating control of the heating part 91 will be stopped (step S9), and a heat retention process will be complete | finished. The reforming system is restarted by a normal procedure by the restart signal.

On the other hand, when the operation of the fuel cell 300 is stopped, the control device 14 performs control to close the adjustment valve 303 shown in FIG. 1 and open the adjustment valve 304 (step S10). By this control, the reformed gas flowing out from the reformer 1 is disconnected from the fuel cell 300, switched to the suction mixing means 6 and consumed as at least a part of the fuel of the steam generating means 2 (step S11).
By operating in this way, the reformed gas and the raw material gas flowing out from the reformer 1 during the stop operation can be used effectively, so that the fuel use efficiency of the reforming system is improved. With the additional supply of reformed gas to the steam generating means 2, it is desirable to adjust (reduce) the other fuel supply to an amount corresponding to the amount of steam to be generated.

  When the steam purge of the reformer 1 is stopped in step S6, the controller 14 further shuts off the fuel to the combustion section 2a of the steam generating means 2 and stops steam generation (step S12). Next, the control device 14 stops supplying air to the combustion unit 2a when the in-furnace purge of the water vapor generating means is completed (step S13).

  As described above, when the reformed gas flowing out of the reformer 1 is switched from the fuel cell 300 to the fuel of the steam generating means 2, surplus steam may be generated from the steam generating means 2. In order to make effective use of surplus steam in such a case, for example, a branch pipe and a flow control valve are provided in the outlet side pipe 109a of the steam generating means 2, and a load facility that consumes surplus steam such as a cogeneration system in the branch pipe. It is desirable to connect.

  The reforming system of the present invention can be suitably used for, for example, a reforming system in which operation and stop operation are alternately repeated.

The process flow figure of the reforming system of the present invention. Sectional drawing which shows the structure of the suction mixing means 6 which supplies a fuel-air mixture. The figure which shows the specific structure of the reforming apparatus 1 shown in FIG. The front view explaining the heating part 91 arrange | positioned in the container 90 of the reformer 1. FIG. The bottom view of FIG. The flowchart which shows the stop procedure in the reforming system of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reforming apparatus 2 Water vapor generation means 2a Combustion part 3 CO reduction means 4 Mixing means 6 Suction mixing means 7 Pressurized air supply system 8 Raw material supply system 9 Desulfurization apparatus 10 Water tank 12, 13 Heat exchange means 14 Control apparatus

20 Ejector 21 Fixed part 22 Internal nozzle structure 23 External nozzle structure 24, 25 Opening 26 Restriction part

31-39 Flow control valve 40 Water level detection means 41 Pressure detection means 42 Temperature detection means

61 Outer cylinder 61a Preliminary reforming chamber 62 Inner cylinder 62a Main reforming chamber 62b Partition wall 63 Oxygen-containing gas introduction section 64, 65, 66 Manifold

68 Supply part 68a Discharge part 69 Discharge part 69a Supply part 70 Thermal insulation wall

71a reforming catalyst layer 71b heat transfer particle layer 72a mixed catalyst layer 72b heat transfer particle layer 72c high temperature shift catalyst layer 72d low temperature shift catalyst layer 72e shift catalyst layer 73a to 73e support plate

80 Preheater 81, 82 Piping 83, 84 Flow control valve 85 Piping 90 Container

91 Heating part 92 Electric heater 93 Fixing tool 101a-114 Piping 300 Fuel cell 301, 302 Piping 303, 304 Flow path switching valve

Claims (5)

  In a reforming system comprising a reformer 1 that generates a hydrogen-rich reformed gas by subjecting a raw material-steam mixture to a steam reforming reaction, and a control device 14, the reformer 1 includes a container 90 and an interior thereof. When the heating unit 91 is disposed so as to surround the container 90 and has the disposed catalyst layer, and the reformer 1 stops operation, the controller 14 causes the dew condensation of water vapor remaining in the container 90. The reforming system is characterized in that the heating unit 91 is controlled so as to prevent the above.   2. The reforming system according to claim 1, wherein the heating unit 91 is a heating method using an electric heater 92, and an outer side of the electric heater 92 is covered with a heat insulating layer.   3. The reforming apparatus 1 according to claim 1 or 2, wherein the reformer 1 is a self-oxidation internal heating type, and includes a preliminary reforming chamber 61a and a main reforming chamber 62a in the container 90, and the reforming chamber 61a is reformed. A reforming system, wherein a catalyst layer 71a is disposed, and a mixed catalyst layer 72a and a shift catalyst layer 72e in which a reforming catalyst and an oxidation catalyst are mixed are disposed in the reforming chamber 62a.   4. The fuel cell 300 according to claim 1, further comprising: a steam generator 2 that supplies steam to the reformer 1; and a fuel cell 300 that is supplied with the reformed gas generated by the reformer 1. The controller 14 controls the supply of the reformed gas generated by the reformer 1 as the fuel for the steam generating means 2 when the fuel cell 300 is stopped.   The reforming system according to claim 4, further comprising a load facility that consumes surplus steam generated by the steam generating means 2.

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