JP2007145637A - Method for starting reformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of rapidly starting an auto-oxidation internal heating type reformer without keeping the temperature during halting the reformer. <P>SOLUTION: The self-oxidation internal heating type reformer 1 is equipped with an inner main reforming chamber 3 and an outer auxiliary reforming chamber 2, wherein the auxiliary reforming chamber 2 is provided with a supply part 4 of a source material-steam mixture and a reforming catalyst layer 5, the main reforming chamber 3 is provided with a mixture catalyst layer 6 comprising a mixture of a reforming catalyst and an oxidation catalyst, a shift catalyst layer 7 and a discharge part 10 of a hydrogen-rich reformed gas successively, and upon starting, a high temperature gas is supplied from a first preheater 11 to the mixture catalyst layer 6. The starting process of the reformer 1 is characterized in that, upon starting, a high temperature gas is further supplied to the supply part 4 of the auxiliary reforming chamber 2 from a second preheater 21. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a starter of a reformer that generates hydrogen for a fuel cell, and has a mixed catalyst layer in which a steam reforming catalyst and an oxidation catalyst are mixed.

2. Description of the Related Art Conventionally, there is known a reformer that generates a hydrogen-rich reformed gas by steam reforming a mixture of a source gas and steam (hereinafter referred to as a source-steam mixture) in the presence of a reforming catalyst.
The hydrogen-rich reformed gas obtained in the reformer is converted into CO ₂ by reacting a small amount of CO (carbon monoxide) contained in the reformer with an oxygen-containing gas in the presence of a catalyst by a CO reduction means, In particular, solid polymer electrolyte fuel cells and the like that operate at low temperatures are suitably used as fuel for fuel cells after reducing CO to several ppm level. 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. In the reformer, the reaction formula of steam reforming when methane is used as a raw material gas can be expressed as CH ₄ + 2H ₂ O → CO ₂ + 4H ₂ , and the preferred reforming reaction temperature is 650 to 750 ° C. It is a range.

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

The partial oxidation reaction can be represented by CH ₄ + 1/2 · 0 ₂ → CO + 2H ₂ , and the preferred partial oxidation reaction temperature is in the range of 250 ° C. or higher. For example, Patent Documents 1 and 2 describe a self-oxidation internal heating type reformer as an improvement of the internal heating type reformer. The reformers of Patent Documents 1 and 2 are provided with a so-called pre-reformation chamber and a main reforming chamber. The pre-reforming chamber is provided with a feed part of the raw material-steam mixture, a reforming catalyst layer, and a discharge part. The quality chamber is provided with a supply portion for receiving the effluent from 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 reforming gas discharge portion. Yes.

  FIG. 2 is a cross-sectional view schematically showing an example of a self-oxidation internal heating type reformer developed by the present inventors prior to the present invention. The reformer 1 has a double cylinder structure having an outer preliminary reforming chamber 2 and an inner main reforming chamber 3, and the preliminary reforming chamber 2 and the main reforming chamber 3 are thermally conductive boundary walls. Are arranged adjacent to each other. The preliminary reforming chamber 2 is provided with a raw material-steam mixture supply unit 4 and a reforming catalyst layer 5, and the main reforming chamber 3 is a mixed catalyst layer 6 in which a reforming catalyst and an oxidation catalyst are mixed, and a shift catalyst layer 7. The hydrogen-rich reformed gas discharge unit 10 is sequentially provided. The shift catalyst layer 7 includes a high temperature shift catalyst layer 8 and a low temperature shift catalyst layer 9.

The reforming catalyst is a steam reforming of the raw material gas. For example, a Ni-based reforming reaction catalyst such as NiO—A1 ₂ O or NiO—SiO ₂ .A1 ₂ O ₃ or WO ₂ —SiO ₂ .A1 ₂ O ₃ NiO-WO ₂ · SiO ₂ · A1 ₂ O ₃ or the like is used. The reforming catalyst constituting the mixed catalyst layer 5 is the same as described above, and the oxidation catalyst uniformly dispersed therein is the temperature required for the steam reforming reaction by oxidizing the raw material gas in the raw material-steam mixture. For example, platinum (Pt), rhodium (Rh), ruthenium (Ru), or palladium (Pd) is used. The mixing ratio of the oxidation catalyst to the reforming catalyst is selected in the range of about 1 to 15% according to the type of the raw material gas to be steam reformed. For example, when methane is used as the raw material gas, it is about 5% ± 2%. In the case of methanol, the mixing ratio is about 2% ± 1%.

  A first preheater 11 is connected to the upper part (upstream side) of the main reforming chamber 3, and a supply pipe 12 that supplies an oxygen-containing gas such as air to the center of the main reforming chamber 3 is extended. The first pre-heater 11 rapidly raises the mixed catalyst layer 6 to the oxidation reaction temperature when the system is started up. An electric heater 13 is disposed inside the first pre-heater 11, and platinum (Pt), palladium (Pd), etc. An oxidation catalyst layer 14 is provided.

  Into the fluid introduction part of the suction mixing means 15 constituted by an ejector, water vapor from a water vapor generating means (not shown), raw material gas from a raw material supply part, start air from an air compressor, and the like can be introduced. The discharge part of the suction mixing means 15 is communicated with the first preheater 11 via a pipe 17 provided with a flow rate adjusting valve 16 and also supplied to the preliminary reforming chamber 2 via a pipe 19 provided with a flow rate adjusting valve 18. The unit 4 communicates with the unit 4.

  A heating unit 20 made of an electric heater is provided at the lower part of the preliminary reforming chamber 2, and the shift catalyst layer 7 is kept at a temperature of, for example, about 200 ° C. by heat transfer from the heating unit 20 during the stop period of the reformer 1. To prevent condensation. If the reformer 1 is operated while dew condensation is generated on the shift catalyst layer 7, it becomes one of the causes of the deterioration of the performance and life of the shift catalyst in the initial stage. Keep the temperature at about 200 ° C.

  When starting up such a self-oxidation internal heating type reformer 1, first, the mixed catalyst layer 6 is heated to the oxidation reaction temperature. For this reason, when the reformer 1 is started, first, the operation of the steam generating means (not shown) is started, and the heat retention of the shift catalyst layer 7 by the heating unit 20 is stopped. Further, the oxidation catalyst layer 14 in the first preheater 11 is heated to a predetermined temperature by the electric heater 13. When the oxidation catalyst of the first preheater 11 reaches the oxidation reaction temperature, the flow rate adjustment valve 16 of the pipe 17 is opened, and the mixed fluid of start air and source gas is supplied from the suction mixing means 15 to the first preheater 11. . Before starting the supply of water vapor from the water vapor generating means, for example, the raw material gas can be pressurized with a pump and supplied to the suction mixing means 15.

  The raw material gas and the start air supplied to the first preheater 11 are high-temperature gases that are produced by a reaction (oxidation reaction or combustion) of a part of the raw material gas with oxygen contained in the start air in the presence of the oxidation catalyst. The mixed catalyst layer 6 is heated. Next, when water vapor having a predetermined pressure is generated in the water vapor generating means, the water vapor is supplied to the suction mixing means 15. At the same time, when the source gas supply is switched from the pressurized pump line to the bypass line, the source gas is efficiently sucked and mixed into the suction mixing means 15 by the suction force of the steam, and the mixed fluid of the source-steam mixture and the start air is discharged from the discharge part. Flows out and is supplied to the first preheater 11.

  The flow rate of the mixed fluid of the raw material-steam mixture and the start air can be adjusted by increasing / decreasing the steam flow rate by a flow rate regulating valve (not shown) provided in the steam supply pipe. Usually, in order to accelerate the temperature rise of the mixed catalyst layer 5, It is adjusted so that the flow rates of the source gas and the start air are increased before the water vapor is supplied to the suction mixing means 15. When the source gas and the start air whose flow rates are increased are supplied to the first preheater 11, the heat of oxidation due to the oxidation reaction increases, and the temperature increase rate of the mixed catalyst layer 6 is also accelerated. A part of the raw material gas not burned by the first preheater 11 flows into the mixed catalyst layer 6 as the remaining raw material gas.

  When the mixed catalyst layer 6 reaches the oxidation reaction temperature, when oxidizing air is supplied from the supply pipe 12, the remaining raw material gas supplied from the first preheater 11 also reacts with oxygen contained in the oxidizing air (oxidation reaction). Or the mixed catalyst layer 6 is further heated by the oxidation heat. Next, when the mixed catalyst layer 6 reaches the reforming reaction temperature, the flow rate adjusting valve 18 is opened, and the raw material-steam mixture is supplied from the suction mixing means 15 to the preliminary reforming chamber 2. Next, the supply of the starting air to the suction mixing means 15 is stopped, and the flow rate adjustment valve 16 is closed to stop the operation of the first preheater 11. Thereafter, the normal operation state is gradually entered when each part of the reformer 1 reaches the operation temperature.

JP 2001-192201 A JP-A-2005-149860

  In the conventional starting method, the outer peripheral portion of the preliminary reforming chamber 2 is kept warm by the heating unit 20 while the reformer 1 is stopped. For this reason, there is a problem that if the stop period of the reformer 1 is prolonged, the heat energy consumption required for heat retention increases. Further, when the heating unit 20 is installed outside the reformer 1, there is a problem that the structure of the reformer 1 becomes complicated and maintenance is difficult to perform. Accordingly, an object of the present invention is to solve such a problem in the conventional self-oxidation internal heating type reformer, and an object of the present invention is to provide a new reformer starting method.

  A method for starting a reformer of the present invention that solves the above-described problem includes an inner main reforming chamber and an outer pre-reforming chamber, and a raw-steam mixture supply unit and a reforming catalyst layer are provided in the pre-reforming chamber. A mixed catalyst layer in which the reforming catalyst and the oxidation catalyst are mixed, a shift catalyst layer, and a hydrogen-rich reformed gas discharge unit are sequentially provided in the main reforming chamber. In the start-up method of the self-oxidation internal heating type reformer configured to supply the high-temperature gas, the high-temperature gas is further supplied from the second preheater to the supply portion of the preliminary reforming chamber at the start-up ( Claim 1).

  In the start-up method, the second preheater includes an oxidation catalyst layer, and a raw material gas and start air are supplied to the oxidation catalyst layer, and a high temperature gas can be generated by oxidation of the raw material gas.

  In the start-up method, an electric heater is provided in the second preheater, and the oxidation catalyst layer is preheated by the electric heater at the start-up, and when the oxidation catalyst reaches the oxidation reaction temperature, the raw material gas and start air are supplied to the second preheater. Supply from the suction mixing means, stop the remaining heat by the electric heater, and when the supply of water vapor to the suction mixing means becomes possible, supply water vapor to the suction mixing means and start with the raw material gas to the second preheater By increasing the supply amount of air, the amount of hot gas generated by the second preheater can be increased (claim 3).

  In the start-up method, when the mixed catalyst layer reaches the oxidation reaction temperature, the supply of the start air to the second preheater is stopped and the reformer goes through the second preheater even after shifting to the normal operation state. Thus, the raw material-steam mixture can be supplied to the supply part (Claim 4).

  In the start-up method of the reformer according to the present invention, the hot gas is supplied from the first preheater to the mixed catalyst layer at the time of start-up, and the hot gas is further supplied from the second preheater to the supply portion of the preliminary reforming chamber. It is characterized by doing so. Therefore, the temperature of the mixed catalyst layer is rapidly raised by the high temperature gas supplied from the first preheater at the time of start-up, and the heat of the high temperature gas supplied from the second preheater is the boundary between the preliminary reforming chamber and the main reforming chamber. The temperature of the shift catalyst layer in the main reforming chamber is raised through the wall.

  On the other hand, the high temperature gas supplied from the second preheater to the preliminary reforming chamber raises the temperature of the preliminary reforming chamber and the reforming catalyst layer provided there, and is mixed by the high temperature gas flowing out from the preliminary reforming chamber. The catalyst layer and the shift catalyst layer provided downstream thereof are heated. For this reason, the shift catalyst layer is heated to the operating temperature rapidly at the start-up by combining indirect heating from the pre-reforming chamber and direct heating by the high-temperature gas flowing out from the pre-reforming chamber. Further, even if condensation occurs in the shift catalyst layer while the reformer is stopped, the condensation is quickly removed at startup. Furthermore, since the high temperature gas supplied from the second preheater to the preliminary reforming chamber heats the interior of the preliminary reforming chamber and the main reforming chamber, the start-up time of the reformer can be shortened.

  In the above start-up method, as described in claim 2, the second pre-heater includes an oxidation catalyst layer, supplies a raw material gas and start air to the oxidation catalyst layer, and generates a high temperature gas by oxidizing the raw material gas. Can do. If comprised in this way, a high temperature gas can be easily produced | generated using some raw material gas for a reforming, and it can supply to a 2nd preheater.

  In the start-up method, as described in claim 3, the second pre-heater is provided with an electric heater, the oxidation catalyst layer is preheated with the electric heater at the start-up, and the second time when the oxidation catalyst reaches the oxidation reaction temperature. The raw material gas and the start air are supplied to the preheater from the suction mixing means, and the remaining heat by the electric heater is stopped, and when the steam supply to the suction mixing means becomes possible, the steam is supplied to the suction mixing means to By increasing the amount of raw material gas supplied to the two preheaters, the amount of high-temperature gas generated by the second preheater can be increased. If comprised in this way, while starting a 2nd pre-heater can be performed rapidly and reliably, a shift catalyst layer can be heated up more than a dew point temperature rapidly.

  In the start-up method, as described in claim 4, when the mixed catalyst layer reaches the oxidation reaction temperature, supply of the start air to the second pre-heater is stopped, and the reformer shifts to a normal operation state. After that, the raw material-water vapor mixture can be supplied to the supply section via the second preheater. If comprised in this way, since it is not necessary to switch a 2nd preheater at the time of starting and operation | movement of a reformer, the structure of a reforming system becomes simpler and driving | operation becomes easy.

  Next, the best embodiment of the start-up method of the reformer according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing a self-oxidation internal heating type reformer of the present invention. The same parts as those of the previous reformer of FIG. 2 described above are denoted by the same reference numerals, and redundant description of the structure and operation is omitted as much as possible.

  The embodiment of FIG. 1 is different from the example of FIG. 2 in that a second pre-heater 21 is provided in the pipe 19 instead of providing the heating unit 20 for keeping the preliminary reforming chamber 2 from the outside. Are constructed similarly. The second preheater 21 of the present embodiment includes an electric heater 22 and an oxidation catalyst layer 23 similar to those of the first preheater 11, and the inlet side thereof communicates with the outlet side of the suction mixing means 15 through the pipe 19. A flow rate adjusting valve 18 is provided. The outlet side of the second preheater 21 communicates with the supply unit 4 of the preliminary reforming chamber 2.

  Next, a method for starting the reformer 1 of FIG. 1 will be described. First, water vapor generation means such as a small boiler (not shown) is activated to prepare for the generation of water vapor. Further, the oxidation catalyst layer 14 is heated by energizing the electric heater 13 of the first preheater 11, and the oxidation catalyst layer 23 is heated by energizing the electric heater 22 of the second preheater 21.

  When the oxidation catalyst 14 of the first preheater 11 rises to the oxidation reaction temperature, the flow rate adjustment valve 16 is opened and the mixture of the raw material gas and the start air is supplied from the suction mixing means 15 to the first preheater 11. The raw material gas supplied to the first preheater 11 reacts with oxygen in the air in the presence of the oxidation catalyst 14, and the generated high temperature gas and a slight amount of unreacted raw material gas are supplied to the mixed catalyst layer 6. The temperature of the layer 5 is gradually increased by the hot gas. In addition, after supplying the mixture of source gas and start air to the 1st preheater 11, since the oxidation reaction temperature is maintained by the heat_generation | fever by the oxidation reaction of source gas, electricity supply of the electric heater 13 is stopped.

  Further, when the oxidation catalyst 23 of the second preheater 21 is heated to the oxidation reaction temperature, the flow rate adjusting valve 18 is opened and the mixture of the raw material gas and the start air is supplied from the suction mixing means 15 to the second preheater 21. . The raw material gas supplied to the second preheater 21 reacts with oxygen in the air in the presence of the oxidation catalyst 23, and the generated high-temperature gas and a small amount of unreacted raw material gas pass through the supply unit 4 and the pre-reforming chamber 2. To be supplied. The temperature of the shift catalyst layer 7 rapidly rises to the dew point or higher (for example, 90 ° C. or higher) due to the heat transfer of the high temperature gas. Also in the second preheater 21, after supplying the mixture of the source gas and the start air, the oxidation reaction temperature is maintained by the heat generated by the oxidation reaction of the source gas, so that the electric heater 22 is deenergized. A small amount of unreacted source gas supplied to the supply unit 4 flows out to the mixed catalyst layer 6 through the reforming catalyst layer 5 of the preliminary reforming chamber 2.

  When water vapor supply from a water vapor generating means (not shown) becomes possible, the water vapor is supplied to the suction mixing means 15 to increase the outflow amount of the mixture of the raw material and the start air, and thereby the first preheater 11 and the second preheater 11 are supplied. The flow rate of the hot gas generated by the heater 21 is increased to accelerate the temperature rise of the mixed catalyst layer 5 and the shift catalyst layer 7.

  Oxidized air is supplied to the supply pipe 12 when the mixed catalyst layer 5 rises to the oxidation reaction temperature. The unreacted source gas flowing in the mixed catalyst layer 5 through the first preheater 11 or the second preheater 21 is oxidized by the air supplied from the supply pipe 12, and the mixed catalyst layer 5 is further raised by the oxidation heat. Warm up. When the mixed catalyst layer 6 reaches the reforming reaction temperature (for example, about 700 ° C.), the supply of the start air to the suction mixing means 15 is stopped, and the flow rate adjustment valve 16 is closed to operate the first preheater 11. Stop. Then, the temperature of the mixed catalyst layer 5 is further increased, and the reformer 1 is shifted to an operating state.

  When the reformer 1 reaches the operating state, the flow rate of the raw material-steam mixture supplied from the suction mixing means 15 to the supply unit 4 is adjusted to a desired flow rate of the reformed gas to be generated and the normal operation is started. . In this embodiment, no special switching means is provided, and the raw material-water vapor mixture is supplied to the supply unit 4 via the second preheater 21 even during normal operation. Since no start air is supplied, the oxidation reaction does not occur in this part. If the method in which the line of the second pre-heater 21 is not switched between when the reformer 1 is started and when it is operated as described above, the configuration and operation of the reforming system become easier.

  The reformer and the starting method thereof of the present invention can be used for starting a self-oxidation internal heating type reformer.

Sectional drawing which shows typically an example of the self-oxidation internal heating type reformer of this invention. Sectional drawing which shows typically the auto-oxidation internal heating type reformer by this inventor before this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reformer 2 Preliminary reforming chamber 3 Main reforming chamber 4 Supply unit 5 Reforming catalyst layer 6 Mixed catalyst layer 7 Shift catalyst layer 8 High temperature shift catalyst layer 9 Low temperature shift catalyst layer 10 Discharge unit 11 First preheater 12 supply Pipe 13 Electric heater 14 Oxidation catalyst layer 15 Suction mixing means 16 Flow rate adjustment valve 17 Pipe 18 Flow rate adjustment valve 19 Pipe 20 Heating part 21 Second preheater 22 Electric heater 23 Oxidation catalyst layer

Claims (4)

  An inner main reforming chamber 3 and an outer pre-reforming chamber 2 are provided. The pre-reforming chamber 2 is provided with a raw material-steam mixture supply unit 4 and a reforming catalyst layer 5, and the main reforming chamber 3 is reformed. A mixed catalyst layer 6 in which a catalyst and an oxidation catalyst are mixed, a shift catalyst layer 7 and a hydrogen-rich reformed gas discharge unit 10 are sequentially provided, and a high temperature gas is supplied from the first preheater 11 to the mixed catalyst layer 6 at the time of startup. In the start-up method of the auto-oxidation internal heating type reformer 1 as described above, the reforming is characterized in that a high-temperature gas is further supplied from the second pre-heater 21 to the supply unit 4 of the preliminary reforming chamber 2 at the start-up. How to start the vessel.   2. The reformer according to claim 1, wherein the second pre-heater 21 includes an oxidation catalyst layer 23, supplies a raw material gas and start air to the oxidation catalyst layer 23, and generates a high-temperature gas by oxidizing the raw material gas. How to start the instrument.   3. The electric heater 22 is provided in the second pre-heater 21, and the oxidation catalyst layer 23 is preheated by the electric heater 22 at the time of start-up, and when the oxidation catalyst layer 23 reaches the oxidation reaction temperature, the second pre-heater 21 is preheated. The raw material gas and the start air are supplied to the heater 21 from the suction mixing unit 15 and the residual heat by the electric heater 22 is stopped, and when the supply of water vapor to the suction mixing unit 15 becomes possible, the water vapor is supplied to the suction mixing unit 15. To increase the amount of raw material gas supplied to the second preheater 21, thereby increasing the amount of high-temperature gas generated in the second preheater 21.   In claim 3, when the mixed catalyst layer 6 reaches the oxidation reaction temperature, the supply of the start air to the second pre-heater 21 is stopped and the second pre-heater 21 is moved to the normal operation state. A starting method for a reformer, characterized in that a raw material-steam mixture is supplied to the supply unit 10 via a heater 21.

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