JP4620947B2 - Auto-oxidation internally heated steam reforming system - Google Patents

Description

  The present invention relates to a self-oxidation internal heating steam reforming system configured to generate a hydrogen-rich reformed gas by subjecting a raw material gas to auto-oxidation and reforming in the presence of steam and oxygen.

  Steam reforming a mixture of raw material gas such as hydrocarbons such as methane, aliphatic alcohols such as methanol, or ethers such as dimethyl ether and steam (hereinafter referred to as raw material-steam mixture) in the presence of a steam reforming catalyst. Systems for generating hydrogen-rich reformed gas have been conventionally known.

The hydrogen-rich reformed gas obtained by the reforming system is suitably used as fuel for the fuel cell. The reforming reactor, which is a main component of the reforming system, is classified into an external heating type and an internal heating type when classified from the supply form of the amount of heat necessary for the steam reforming reaction. In addition, 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 a preferable reforming reaction temperature is in the range of 700 to 750 ° C.

  The former external heating type heats the wall surface of the reforming reaction apparatus from the outside with combustion gas generated by a burner or the like, and supplies heat necessary for the reforming reaction to the internal reaction chamber through the wall. The internal heating type is an improvement of the external heating type described above, and is equipped with a partial oxidation catalyst layer on the supply side (upstream side) of the raw material-steam mixture in the reforming reaction apparatus, and the heat generated in the partial oxidation catalyst layer is The steam reforming catalyst layer disposed on the downstream side is heated to the steam reforming reaction temperature.

The heated steam reforming catalyst layer is configured to react the raw material gas and steam to generate a hydrogen-rich reformed gas.
The partial oxidation reaction can be represented by CH ₄ +1/2 O ₂ → CO + 2H ₂ , and the preferred partial oxidation reaction temperature is in the range of 250 ° C. or higher.

  However, in the conventional reforming reaction apparatus in the external heating type and the internal heating type, since the temperature of the heating unit is higher than the reforming temperature level of about 700 ° C., for example, 1000 ° C., energy loss due to heat dissipation is large, There was a problem that high temperature deterioration occurred in the members constituting the apparatus and the life was short.

  As an improved version of the internal heating type, a self-oxidation internal heating type reformer is proposed in Patent Document 1. Conventionally, the function of the steam reforming catalyst has been impeded in the presence of oxygen, but the conventional technology proposed in this publication solves this problem by coexisting an oxidation catalyst, and even in the presence of oxygen. It is possible to effectively maintain the original function of the steam reforming catalyst.

JP 2001-192201 A

  In the improved technique proposed in Patent Document 1, the heat generated by the oxidation reaction and the steam reforming reaction are simultaneously performed in a mixed catalyst layer in which an oxidation catalyst and a steam reforming catalyst are mixed. That is, the coexistence of the exothermic layer due to oxidation and the endothermic reaction layer due to steam reforming makes it possible to keep the temperature of the exothermic part and the temperature of the endothermic part equal. Further, the temperature of the constituent member such as the catalyst layer can be suppressed to a predetermined reforming reaction temperature or lower, for example, in the vicinity of 700 ° C., thereby increasing the life of the constituent member. Moreover, since it has the function to collect | recover the heat | fever inside a reformer effectively, high reforming efficiency is obtained.

  In the above-described prior art self-oxidation internal heating type reformer, water supplied from a water supply pump is heated with a reformer by heat exchange with a reformed gas, and further heat exchanged with a reforming reactor to produce steam. Is generated. The steam is mixed with the raw material gas in a mixer.

  However, in a system in which water is heat-exchanged with reformed gas to generate steam, the amount of steam generated depends on the flow rate and temperature of the reformed gas, and it is difficult to accurately control the required amount. Furthermore, it is difficult to provide a heat exchange section for generating steam with relatively large dimensions in the reforming reaction apparatus, and there is a problem that the apparatus configuration becomes complicated. Further, as described above, the hydrogen-rich reformed gas generated by the reformer can be used as fuel for the fuel cell. However, in the configuration of the above prior art, the anode exhaust gas of the fuel cell cannot be reused as fuel for generating steam. .

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the problem of the self-oxidation internal heating type reformer disclosed in the above-mentioned prior art, and an object thereof is to provide a new self-oxidation internal heating type steam reforming system. To do. It is another object of the present invention to provide a system for recycling anode exhaust gas containing hydrogen discharged from a fuel cell as a reforming raw material gas when the reformed gas to be produced is supplied to the fuel cell.

The present invention that solves the above-mentioned problem is a self-oxidation internal heating steam reforming system configured to generate a hydrogen-rich reformed gas by auto-oxidizing the raw material gas in the presence of oxygen and steam reforming,
Mixing means 123 for mixing the raw material gas and the water vapor generated by the water vapor generating means 2 to obtain a raw material-water vapor mixture;
A reforming means 1 is provided that oxidizes a source gas contained in a source-steam mixture with an oxygen-containing gas supplied from the outside and generates a hydrogen-rich reformed gas by performing steam reforming of the source gas with reaction heat due to oxidation. ,
The reformed gas is supplied to the fuel cell 300,
Recycling means 122 for supplying at least part of the anode exhaust gas discharged from the fuel cell 300 to the reforming means 1 as the raw material gas is provided,
The steam generating means 2 includes a combustion part 2a for combusting an air-fuel mixture obtained by mixing combustion air and fuel, and at least a part of the anode exhaust gas as the fuel is a combustion part of the steam generating means 2. Configured to supply to 2a ,
When surplus is generated in the water vapor generated by the water vapor generating means 2, the supply amount of the anode exhaust gas to the combustion unit 2 a is decreased so as to reduce the surplus, and the supply amount of the anode exhaust gas to the mixing means 123. This is a self-oxidation internal heating steam reforming system characterized in that a control means 14 is provided for performing control to increase the amount (Claim 1).

  In the above system, the mixing means 123 includes first suction mixing means 4 that sucks a raw material gas into a steam flow to obtain a raw material-water vapor mixture, and the anode exhaust gas is sucked into the first suction mixing means 4. (Claim 2).

In the above system, the air - to obtain a fuel mixture can be provided with second suction means 6 for sucking fuel into air for combustion (claim 3).

In the above system, the pressure detecting means 41 for detecting the pressure of the water vapor generated by the water vapor generating means is provided, and when the detected pressure rises from a preset value, the increased value is used as the surplus water vapor in the control means 14. type, control means 14 so that the detected pressure decreases the supply amount of the anode exhaust gas into the combustion section 2a so that the set value is controlled to increase the supply amount of the anode exhaust gas into the mixing means ( Claim 4 ).

Since the reforming system of the present invention is provided with the anode exhaust gas recycling means 122, the surplus anode exhaust gas can be effectively used as a raw material. Further, the hydrogen concentration in the reformed gas is reduced by N ₂ and CO ₂ in the anode exhaust gas, and the hydrogen conversion rate of methane and the like can be increased. Furthermore, since it becomes possible to supply more hydrogen than necessary to the fuel cell body, the flow rate of the reformed gas flowing in the fuel cell can be increased. When the flow velocity in the fuel cell is increased, it is possible to prevent water droplets generated at the portion from being blown off and a water curtain to be formed on the electrode, thereby reducing power generation efficiency.
And, since at least a part of the anode exhaust gas is supplied as fuel to the combustion part 2a of the water vapor generating means 2, water vapor can be generated with high efficiency by hydrogen contained together with effective use of the anode exhaust gas. The system can be made compact.
Further, when surplus water vapor is generated, the control means 14 is provided for performing control for reducing the supply amount of the anode exhaust gas to the combustion unit 2a and increasing the supply amount of the anode exhaust gas to the mixing means 123. The effective use form of water vapor can be optimally and automatically changed according to the load condition, whereby the system can be continuously operated with high energy efficiency .

  In the above system, when the first suction mixing unit 4 is used as the mixing unit 123, the common first suction mixing unit 4 can simultaneously mix other raw materials and anode exhaust gas with water vapor. Also, by switching the raw material system to the suction mixing means 4 on day 1, other raw materials and anode exhaust gas can be selectively mixed with water vapor. Furthermore, a mixture of anode exhaust gas and water vapor can be easily obtained without using a special power unit. Furthermore, since the pressure of the raw material system becomes extremely low, there is little risk of leakage of other raw material gases and anode exhaust gas from the pipe joints and the like.

  Further, in order to obtain an air-fuel mixture to be supplied to the water vapor generating means 2, if the second suction means 6 for sucking the fuel into the combustion air is provided, the air-fuel (anode exhaust gas) can be used without using a special power unit. ) The mixture is obtained with high mixing efficiency and uniform mixing form. Furthermore, since the pressure of the fuel system becomes extremely low, there is little risk of fuel leaking outside from a pipe joint or the like.

  In the above-described system, if the excess water vapor amount is controlled by detecting the pressure of the water vapor generated by the water vapor generation means, the excess water vapor amount can be detected by the pressure detection means with high measurement accuracy, so that the accuracy and reliability are high. High control can be performed.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a process flow diagram showing the basic configuration of a self-oxidation internal heating steam reforming system. In FIG. 1, reference numeral 80 denotes a package structure of a self-oxidation internal heating steam reforming system, which is designed to satisfy the interface conditions with peripheral devices. In other words, the devices that make up each system are united and detachably attached to a common base, rack, container, or case using fasteners such as bolts, and the devices are arranged compactly and the piping between them The heat dissipation loss is reduced as much as possible.

  The water vapor generating means 2 includes a combustion section 2a and a second suction means 6, and a burner (not shown) for burning the air-fuel mixture supplied from the second suction mixing means 6 is provided in the combustion section 2a. Provided. Further, a pipe 108 for supplying water or pure water from the water tank 10 and a pipe 109 for supplying water vapor to the first suction mixing means 4 are connected to the water vapor generating means 2. The pipe 108 is provided with a flow control valve 32 that can be remotely operated (for example, a control valve driven by a pneumatic, hydraulic or electric type, and the same applies to other flow control valves hereinafter). A flow rate adjustment valve 39 is provided.

  Further, the water vapor generation means 2 is provided with a water level detection means 40 for detecting the water level of the water storage part (water drum) and a pressure detection means 41 for detecting the pressure of the water vapor generated in the water storage part. Proportional electrical signals (detection signals) are respectively input to the control means 14.

  The control means 14 controls each flow rate adjusting valve or the like in response to an operation command from the detection value of the water level detection means 40 or the pressure detection means 41 or another operation panel. The control means 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, an input unit such as a keyboard or mouse, or an operation panel. Further, a display, a printer, etc. are added if necessary. The control means 14 may be installed at a location away from the package structure 80 in which the present system is accommodated, and the flow rate adjusting valve and the like may be controlled 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 exchange means 13, and the tip end of the pipe 114 opens to the outside. A pipe 101a for supplying gas fuel or liquid fuel such as anode exhaust gas of the fuel cell is connected to the heat exchanging means 13, and the pipe 101a communicates with the pipe 101 via the heat exchanging means 13. 2 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 via the flow rate adjustment valve 34. The air supplied from the pipe 112 is used as air for purging and / or adjusting the combustion temperature of the combustion section 2a when the operation of the combustion section 2a is started. That is, a control signal for opening the flow rate adjustment valve 34 is output from the control means 14 by the operation start signal for a set time, thereby purging the inside of the combustion section 2a. In addition, a predetermined amount of air is supplied so that the combustion temperature of the combustion section 2a becomes a predetermined temperature or less.

  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 means 9, and a pipe 103 through which the desulfurized raw material gas flows out is connected to the outlet side of the desulfurization means 9. The The pipe 103 is provided with a flow control valve 31 that can be operated remotely. The downstream side of the flow control valve 31 communicates with the pipe 108a through the heat exchanging means 13, and the tip of the pipe 108a is the first suction mixing means 4. Connected to. Although the illustrated heat exchange means 13 uses a three-fluid heat exchanger, two two-fluid heat exchangers having a heat exchange pipe for flue gas can also be used.

  A pipe 102b for supplying combustion air is connected to the second suction and mixing means 6, and the pipe 102b communicates with the pipe 102a through a heat exchange means 12 described later. The pipe 102a is provided with a flow control valve 37 that can be operated remotely, and the tip of the pipe 102a communicates with a pressurized air supply system 7 equipped with an air compressor or the like. A pipe 111a branched from the source gas supply pipe 111 is connected to the pipe 101a, and the pipe 111a is provided with a flow rate adjusting means 33a that can be remotely operated.

  The reforming means 1 is connected to a pipe 104 for supplying the raw material-steam mixture from the first suction mixing means 4 and a pipe 102d for supplying a pressurized oxygen-containing gas such as pressurized air. The pipe 102 d communicates with the pipe 102 c provided with the flow rate adjusting valve 36 that can be remotely operated via the heat exchange means 12, and the tip end of the pipe 102 c is connected to the pressurized air supply system 7.

  Further, a reforming gas discharge pipe 105 is connected to the reforming means 1, the pipe 105 is connected to the pipe 106 through the heat exchanging means 12, and the tip portion of the pipe 106 is mixed with the oxidizing air 5. Connected to. The outlet side of the mixing means 5 is connected to the CO reducing means 3, and the outlet pipe 107 is connected to a load facility such as the fuel cell 300. As the oxidation catalyst for the CO reduction means, for example, a pellet type in which noble metal contacts such as Pt and Pd are supported on ceramic particles, a metal honeycomb structure or a ceramic honeycomb structure in which noble metal contacts such as Pt and Pd are supported Can be used.

  The mixing means 5 is connected to a pressurized air supply pipe 110 provided with a flow control valve 38 that can be operated remotely, and the tip of the pipe 110 is connected to the pressurized air supply system 7. In this example, a three-fluid heat exchanger is used as the second heat exchanging means 12, but two two-fluid heat exchangers having a reformed gas heat exchanging pipe may be used.

  As will be described later, the reforming means 1 is provided with a first reaction chamber 61a and a second reaction chamber 62a (see FIG. 3), and the temperature of the mixed catalyst layer 72a accommodated in the second reaction chamber 62a is adjusted. A temperature detecting means 42 for detecting is provided. The detection signal from the temperature detection means 42 is input to the control means 14.

  As shown in FIG. 2, the first suction mixing unit 4 and the second suction mixing unit 6 are each configured by an ejector 20 of the same principle, except for the capacity. 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 first suction mixing unit 4 will be described as an example. When the steam flow, which is the main fluid, is supplied to the internal nozzle structure 22 as shown by the arrow, the space portion 26 is decompressed due to the venturi effect of the steam flow. Then, when the raw material gas which is a sub-fluid is supplied from the opening 24 as shown by the arrow, the raw material gas is sucked and mixed uniformly with the vapor flow and ejected from the opening 25. Therefore, the raw material gas is uniformly mixed with water vapor without using a special power unit, and a homogeneous raw material-water vapor mixture is obtained.

  In the case of the second suction and mixing means 6, air as a main fluid is supplied to the internal nozzle structure 22, and fuel gas as a secondary fluid is supplied from the opening 24, so that the fuel gas has a special power unit. Mix evenly with air even if not used. The mixing means 5 can also be constituted by an ejector 20 as shown in FIG. In that case, the reformed gas becomes the main fluid, and the pressurized air is sucked and mixed.

FIG. 3 is a view showing a specific configuration of the reforming means 1 shown in FIG. 1, (a) is a longitudinal sectional view thereof, (b) is a sectional view taken along line BB of (a), and (c) is ( It is CC sectional drawing of a). The reforming means 1 includes a vertically long outer cylinder 61 having a rectangular outer cross section and two long inner cylinders 62 having a rectangular outer cross section disposed at predetermined intervals therein. The upper and lower ends of the outer cylinder 61 are closed, the upper and lower ends of the inner cylinder 62 are opened, and the lower end edges thereof are fixed to the bottom surface of the outer cylinder 61 with a to constitute the bottom portion of the inner cylinder 62. The bottom is provided with a hole.
A first reaction chamber 61 a is formed in the space between the inner wall surface of the outer cylinder 61 and the outer wall surface of the inner cylinder 62, and a second reaction chamber 62 a is formed inside the inner cylinder 62. 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 first reaction chamber 61a and the second reaction chamber 62a are separated from each other by a good heat transfer partition wall 62b. It has become.

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

  A raw material supply unit 69a that communicates with the discharge unit 68a of the first reaction chamber 61a is provided at one end of the second reaction chamber 62a (upper side in FIG. 3), and an oxygen-containing gas such as air is provided in the raw material supply unit 69a. The manifolds 64 and 65 of the oxygen-containing gas introduction part 63 for introducing the gas communicate with each other. A discharge portion 69 having a manifold 65 is provided at the other end (lower side in FIG. 3) of the second reaction chamber 62a.

  Furthermore, support plates 73a, 73b, 73c, 73d, 73e having a large number of minute through portions are provided in the second reaction chamber 62a in order from the raw material supply unit 69a side. In the illustrated example, the support plates 73a and 73c provided in the first reaction chamber 61a have the same height as the support plates 73a and 73c provided in the second reaction chamber 62a. You can also.

  The mixed catalyst layer 72a in which the steam reforming catalyst and the oxidation catalyst are mixed is filled between the support plates 73a and 73b of the second reaction 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 the plates 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 disposed in the second reaction chamber 62a is a heat insulating wall 70, which prevents the oxidation reaction heat from the oxidation catalyst from escaping to the first reaction chamber 61a. .

The steam reforming catalyst layer 71a filled in the first reaction chamber 61a is a catalyst layer for steam reforming the raw material gas, and is similar to the reforming reaction catalyst disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-192201. Among them, a Ni-based reforming reaction catalyst such as NiS—SiO ₂ · Al ₂ O ₃ is preferable. A reforming reaction catalyst such as WS ₂ —SiO ₂ · Al ₂ O ₃ or NiS—WS ₂ · SiO ₂ · Al ₂ O ₃ can also be used. Furthermore, a known noble metal catalyst can be used if necessary.

  As the steam reforming catalyst which is the main component constituting the mixed catalyst layer 72a, the same steam reforming catalyst as that filled in the first reaction chamber 61a can be used. The amount of the steam reforming catalyst used is set to 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 depends on the type of raw material gas used. Since it varies, the optimum range is determined by experiments or the like.

  The oxidation catalyst uniformly dispersed in the mixed catalyst layer 72a is a material that heats the raw material gas in the raw material-steam mixture to oxidize and raises the temperature to a temperature necessary for the steam reforming reaction. For example, platinum (Pt) or palladium ( Pd) can be used. The mixing ratio of the oxidation catalyst to the steam reforming catalyst is selected in the range of about 1 to 5% depending on the type of the 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%. A catalyst in which an oxidation catalyst and a steam reforming catalyst are simultaneously supported on the same support can also be used.

  The heat transfer particle layer 71b of the first reaction chamber 61a and the heat transfer particle layer 72b of the second reaction chamber 62a efficiently transfer the heat energy of the second reaction chamber 62a to the first reaction chamber 61a via the partition wall 62b. Provided. That is, the heat transfer particle layer 72b filled in the second reaction chamber 62a heats the steam reforming catalyst layer 71a portion filled in the first reaction chamber 61a with the thermal energy of the high temperature effluent from the mixed catalyst layer 72a, The heat transfer particle layer 71b filled in the reaction chamber 61a heats the raw material-steam mixture flowing from the raw material supply unit 68 with the thermal energy from the shift catalyst layer 72e, which is an exothermic reaction unit, and transfers the thermal energy of both of them to transfer the heat energy. The temperature in the steam reforming catalyst layer 71a portion of the one reaction 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. Further, the heat transfer particle layer 72b may not be provided in some cases.

  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. A heat transfer particle layer may be provided between the high temperature shift catalyst layer 72c and the low temperature shift catalyst layer 72d.

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 700 ° C. or higher, it is desirable to use Cr ₂ O ₃ . However, in some cases, a known noble metal can be used as the shift catalyst.

  In the plurality of partition walls 62b, the end portions on the side of the raw material supply unit 68 and the discharge unit 69 are connected to each other at a portion to become fixed ends, and the end portions on the opposite side are not connected to each other and are free ends. It has become. Therefore, when there is a difference in thermal expansion between the first reaction chamber 61a and the second reaction chamber 62a that are brought to a high temperature state by the reforming reaction, especially when the second reaction chamber 62a has a large thermal expansion, the second reaction due to the thermal expansion. The expansion of the chamber 62a can be absorbed by the free end and the occurrence of distortion can be prevented.

  Next, a method for performing steam reforming of the raw material gas by the self-oxidation heating steam reforming system of FIG. 1 will be described.

(Water vapor generation operation)
First, the pressurized air supply system 7 is activated, pressurized air is supplied to the system, and the control means 14 is activated. Next, the water vapor generating means 2 is operated. The water level of the water storage section (water drum) of the steam generating means 2 is detected by the water level detecting means 40, and when 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 means 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 part 2a of the water vapor generating means 2, and further controls the flow rate adjusting valves 37, 33 (or 33a) to the combustion part 2a at a predetermined flow rate fuel-air mixture. Supply. That is, the control unit 14 controls the flow rate adjustment valve 37 of the pipe 102b for flowing pressurized air to the second suction mixing unit 6 so that the water vapor pressure detection value from the pressure detector 41 becomes a preset value. .

  When the controlled air flow flows into the second 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 second suction mixing unit 6 is used, the control unit 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. The degree can also be controlled to be approximately proportional to the air flow rate. Further, by setting the pressure of the pressurized air supplied to the first suction mixing means 6 to a value slightly higher than the normal pressure, for example, about 0.02 MPa, the fuel gas can be sucked into the second suction mixing means 6. A level of negative pressure can be generated.

  By opening the flow rate adjusting valve 33, gas fuel such as fuel cell anode exhaust gas, city gas, propane gas, natural gas, or liquid fuel such as kerosene is supplied to the second suction mixing unit 6 from the pipe 101 a. Further, by opening the flow rate adjusting valve 33a, a raw material gas such as anode exhaust gas of a fuel cell containing hydrocarbons such as methane, ethane and propane, alcohols such as methanol, ethers such as dimethyl ether, or residual hydrogen is gasified from the pipe 111. It can also be supplied to the second suction mixing means 6 as fuel.

  The selection of the flow rate adjusting valves 33 and 33a can be performed by a fuel selection command to the control means 14, for example. If necessary, both can be adjusted simultaneously. 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 is heated by the heat exchange means 13 and then supplied to the second suction mixing means 6.

(Raw material-steam mixing operation)
The water vapor generated by the water vapor generating means 2 is flow-adjusted by a flow restrictor such as a flow regulating valve 39 or an orifice and supplied to the first suction mixing means 4, and the flow rate adjustment is a control signal from the control means 14. Done in That is, when the set value of the raw material supply flow rate to the reforming unit 1 is input from the input unit provided in the control unit 14, the control unit 14 outputs a control signal for maintaining a predetermined valve opening degree to the flow rate adjustment valve 39. Instead of adjusting the valve opening degree of the flow rate adjusting valve 39, an appropriate flow rate can be adjusted with a plurality of orifices and switching valves having different flow rates.
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.

  As described above, the first suction mixing unit 4 includes a fuel cell containing a predetermined proportion of hydrocarbons such as methane, ethane, and propane, alcohols such as methanol, ethers such as dimethyl ether, or residual hydrogen with respect to the water vapor flow rate. Source gas such as anode exhaust gas, city gas, propane gas, and natural gas is sucked from the pipe 109. A uniform raw material-steam mixture flows out from the first suction mixing unit 4 and is supplied to the reforming unit 1. As described above, since the source gas is automatically sucked by the suction force of the water vapor flow in the first suction mixing unit 4, it is not necessary to provide a boosting unit such as a special power unit in the source gas system.

  The raw material gas supplied from the raw material supply system 8 flows into the pipe 108 a through the pipe 111, the desulfurization means 9, the flow rate adjustment valve 31, and the first heat exchange means 13. The source gas is limited in its maximum allowable flow rate by a flow rate adjusting valve 31 maintained at a predetermined opening by a control signal from the control means 14, heated to a predetermined temperature by the first heat exchange means 13, and then the first gas flow. It is supplied to the suction mixing means 4.

(Reforming reaction operation)
As described above, the raw material-water vapor mixture flowing out from the first suction mixing unit 4 into the pipe 104 flows into the first reaction chamber 61a through the raw material supply unit 69 (FIG. 3) of the reforming unit 1. During normal operation, the heat transfer particle layer 71b filled in the first reaction chamber 61a is heated by the heat energy transferred from the second reaction chamber 62a through the partition wall 62b, so that the first reaction chamber 61a 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 steam 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. . 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.

  However, since the raw material-steam mixture cannot be heated up to the reforming reaction temperature for a while from the start of operation, the steam reforming reaction does not decrease or hardly proceeds depending on the temperature at that time. The composition is discharged from the discharge section 68a with a composition almost similar to that at the time of inflow. Since the steam reforming reaction is an endothermic reaction, the temperature of the mixture flowing out from the discharge portion 68a is lower than the average temperature of the steam reforming catalyst layer 71a.

  The reformed gas and the raw material-water vapor mixture discharged from the discharge portion 68a of the first reaction chamber 61a flow into the mixed catalyst layer 72a from the raw material supply portion 69a of the second reaction chamber 62a. At that time, air is supplied as oxygen-containing gas from the oxygen-containing gas introduction unit 63 to the raw material supply unit 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 adjusting valve 36 controlled by the control means 14. That is, control information of the flow rate adjusting valve 35 for adjusting the water vapor flow rate is stored in the control means 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. Instead of disposing the oxygen-containing gas introducing portion 63 at the upper end of the reformer as shown in FIG. 3, an air pipe that penetrates the bottom surface of the outer cylinder 61 is inserted into the inner cylinder 62, and is inserted into the upper end of the pipe. A plurality of air outflow holes can also be provided. In this case, heat can be exchanged between the air flowing through the pipe and each layer in the inner cylinder 62 to heat the air. Thereby, the efficiency of the apparatus can be improved.

  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 inflowed air and is oxidized, and the reaction heat generates the raw material. -Raise the steam mixture to the level required for the reforming reaction. That is, auto-oxidation heating is performed. The average temperature in the mixed catalyst layer 72a is preferably 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, in the temperature control in the mixed catalyst layer 72a, it is important to set the temperature suitable for the steam reforming reaction. At the same time, the temperature at the boundary with the downstream heat transfer particle layer 72b is maintained at a predetermined level. It is important to manage as much as possible. For example, when the average temperature in the mixed catalyst layer 72a is controlled so that the temperature at the boundary with the heat transfer particle layer 72b is 650 ° C. or higher, preferably 700 ° C. or higher, the heat transfer particle layer 71b in the first reaction chamber 61a The temperature can be maintained at least at 500 ° C. or higher, thereby sufficiently promoting the steam reforming reaction in the first reaction chamber 61a.

  In order to maintain the average temperature of the mixed catalyst layer 72a in the above range, for example, by adjusting the SV value (Space Velocity) of the reformed gas passing through the mixed contact layer 72a to the required specification of the catalyst function. realizable. In the present embodiment, the average temperature of the mixed catalyst layer 72a is maintained at the reforming reaction temperature at which the steam reforming reaction can proceed. It is desirable that both the amount of oxygen necessary for raising the temperature for the steam reforming reaction and the amount of oxidation catalyst for completely reacting the oxygen are minimized. According to experiments, it has been found that the SV value for the reforming catalyst for the steam reforming reaction is preferably about 5000, and the SV value for the oxidation catalyst for the partial oxidation reaction is preferably about 100,000.

  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. While the reformed gas that flowed in as described above passes through the heat transfer particle layer 72b, a part of the sensible heat moves to the heat transfer particle layer 71b of the first reaction 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 flowing into the high temperature shift catalyst layer 72c is converted into hydrogen 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 into the low temperature shift catalyst layer 72d on the downstream side, and further hydrogen is generated from the remaining carbon monoxide. By performing the two-stage shift reaction in this manner, carbon monoxide can be further 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 first reaction 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 portion 69 of the second reaction 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, the heat is introduced 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. In the CO reduction means 3, carbon monoxide remaining in the reformed gas is reduced to a very small level (for example, 10 ppm) and supplied from the pipe 107 to a load facility such as the fuel cell 300.

  The flow rate of air supplied from the pipe 110 to the mixing unit 5 is adjusted by changing the opening of the flow rate adjusting valve 38 according to a control signal from the control unit 14. That is, the control means 14 stores the control information of the flow rate adjusting valve 38 that adjusts the air flow rate, and the air flow rate is correlated with the reformed gas flow rate. Therefore, 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.

  However, instead of using the water vapor control information, it is also possible to provide a carbon monoxide concentration detection means on the outlet side of the CO reduction means 3 and transmit the detection signal to the control means 14 for control. That is, the control means 14 outputs a control signal to the flow rate adjusting valve 38 so that the concentration of carbon monoxide contained in a minute amount in the reformed gas flowing out from the outlet side of the CO reducing means does not exceed a preset range. Configure as follows.

  The CO reduction means 3 can be constituted by, for example, accommodating a honeycomb porous sheet carrying an oxidation catalyst in a cylindrical reaction vessel by winding it in multiple layers. While the reformed gas flowing in from the inlet of the reaction tank passes through the gap between the wound sheets and flows out from the outlet, the contained carbon monoxide is oxidized by the oxidation catalyst and converted into harmless carbon dioxide. For this reason, the reformed gas flowing out from the CO reducing means 3 contains only a very small amount of carbon monoxide, so that it does not adversely affect the fuel cell, for example.

  FIG. 4 is a process flow diagram of the auto-oxidation internally heated steam reforming system including the features of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted. 4 differs from the example of FIG. 1 in that anode exhaust gas discharged from the fuel cell 300 is supplied as fuel to the combustion section 2a of the steam generation means 2 through various heat exchange means and recycled as a raw material gas. It is in.

  In FIG. 4, the anode exhaust gas discharged from the fuel cell 300 to the pipe 101d flows into the heat exchange means 18 for reheating, where it is cooled to some extent by heat exchange and then flows into the heat exchange means 19 for dehydration. In the heat exchanging means 19 for dehydration, another heat medium such as cogeneration equipment is supplied through the pipe 115, the anode exhaust gas is cooled by the heat medium, moisture is condensed and dehydrated, and the heat of the anode exhaust gas is reduced. It is recovered in another heat medium. The anode exhaust gas after dehydration flows into the heat exchange means 18 for reheating, where the relatively high temperature anode exhaust gas that has flowed from the pipe 101d is heat-exchanged and reheated.

  In general, the anode exhaust gas contains a relatively high moisture together with hydrogen. However, the anode exhaust gas having a low moisture content can be obtained by using the heat exchange means 19 for dehydration as described above. In addition, it is configured to reheat the anode exhaust gas after dehydration using the heat of the relatively hot anode exhaust gas discharged from the fuel cell, so that it recovers to an appropriate temperature level without supplying another heat source. Can be made.

  The reheated anode exhaust gas flows into the heat exchanging means 113a through the pipe 101a, where it is heated by heat exchange with the exhaust gas of the water vapor generating means 2 and then supplied as fuel to the combustion section 2a. Further, the raw material gas is supplied from the branch pipe of the pipe 101a to the mixing means 123, details of which will be described later.

  The water vapor generated by the water vapor generating means 2 is supplied to the first suction mixing means 4. The raw material gas flowing out from the heat exchanging means 16 described later is supplied to the suction mixing means 4, where it is sucked by the mainstream steam to produce a raw material-water vapor mixture. The raw material-steam mixture passes through the pipe 104 and the raw material-steam mixed gas flows into the heat exchanging means 12a, where it is heated by heat exchange with the reformed gas flowing in from the pipe 107 to the raw material supply section 68 of the reforming means 1. Supplied.

  The basic structure of the reforming means 1 in FIG. 4 is the same as that in FIG. 1, but the structure is slightly different. That is, in the reforming means 1 of FIG. 4, an oxygen-containing gas supply pipe 62b perpendicular to the center of the secondary reaction chamber 62a is provided, and the oxygen-containing gas supplied from the pipe 102 is supplied from the lower part of the oxygen-containing gas supply pipe 62b. It flows in, rises inside, and is ejected into the mixed catalyst layer 72a from the ejection hole 62c provided near the top. If comprised in this way, secondary reaction chamber 62a itself becomes a heat exchange means, and can preheat an oxygen-containing gas inside with the reaction heat. The reforming means 1 includes a primary reaction chamber 61a and a secondary reaction chamber 62a as in the basic configuration of FIG. 1, and various catalyst layers similar to those in FIG. 1 are disposed therein.

  In the reforming means 1 of FIG. 4, a temperature raising means 120 is connected to the upper part of the reforming means 1 in order to quickly raise the reforming means 1 to the reforming reaction temperature when the system is started. The temperature raising means 120 includes a tank 120a and an oxidation catalyst 120b such as platinum (Pt) or palladium (Pd) filled therein. The raw material gas in the raw material-steam mixture supplied from the pipe 104 is oxidized by oxygen in the oxygen-containing gas supplied from the pipe 102b in the presence of the oxidation catalyst 120b, and the temperature of the raw material-steam mixture is changed by the oxidation heat. The temperature is raised to around the temperature necessary for the steam reforming reaction. In this example, the heat exchange means is added to the oxidation catalyst layer, and another heat medium is supplied to the heat exchange means from the pipe 120c to heat the oxidation catalyst layer, and the temperature rise is further accelerated. Yes.

  The hydrogen-rich reformed gas generated by the reforming unit 1 flows out from the pipe 105 and flows into the mixing unit 5. The mixing means 5 can be constituted by an ejector similar to the first suction mixing means 4, and the oxygen-containing gas supplied from the pipe 110 provided with the flow rate adjusting means 38 with the inflowing reformed gas as the main flow. Aspirate and mix. The downstream side of the mixing unit 5 communicates with the CO reduction unit 3, and the CO remaining in the reformed gas is reduced in the CO reduction unit 3 in the same manner as in the example of FIG. Further, on the downstream side of the CO reduction means 3, three heat exchange means 12a, 16 and 17 are sequentially connected by pipes 107a to 107c.

  In the heat exchange means 12a, the raw material-steam mixture in the pipe 104 is preheated as described above, and in the heat exchange means 16, the raw material gas supplied from the desulfurization means 9 through the pipe 103a is preheated with the reformed gas flowing in from the pipe 107a, In the heat exchange means 17, water for generating steam or pure water supplied from the water tank 10 through the pipe 108a is preheated with the reformed gas flowing in from the pipe 107b. Then, the reformed gas gradually decreases in temperature by passing through these heat exchange means 12a, 16 and 17, and is supplied to the fuel cell 300 in a low temperature state.

  Next, the anode exhaust gas recycling means 122, which is a feature of the present invention, will be described. The recycle unit 122 shown in FIG. 4 includes a pipe 101 a for supplying anode exhaust gas and a mixing unit 123. The mixing means 123 is also used as the first suction mixing means 4 composed of an ejector that generates a raw material-water vapor mixture. That is, the first suction mixing means 4 is supplied with steam as a main stream, and the anode exhaust gas of the pipe 101a is sucked together with the raw material gas of the pipe 103a by the attraction force of the steam. Then, the raw material-steam mixture obtained by the first suction mixing unit 4 is supplied to the reforming unit 1 through the pipe 104.

  For example, when the flow rate of the raw material-steam mixture to the reforming means 1 is reduced, the required steam consumption is also reduced accordingly. However, when the amount of water vapor generated by the water vapor generating means 2 is constant, the water vapor pressure rises due to a decrease in water vapor consumption. Therefore, in the present embodiment, the anode exhaust gas supply amount to the combustion unit 2a is decreased and the anode exhaust gas supply amount to the mixing means 123 is automatically increased so that the water vapor pressure becomes a preset value. I have control.

  For example, when the increase in the water vapor pressure is detected by the pressure detection means 41 and the detected value becomes higher than a preset value, the control means 14 adjusts the amount of anode exhaust gas to the combustion section 2a. Control is performed to reduce the opening degree and increase the opening degree of the flow rate adjusting means 122a for adjusting the supply amount of the anode exhaust gas to the mixing means 123. When the anode exhaust gas is not supplied to the combustion unit 2a, the control unit 14 can perform only control for increasing the supply amount of the anode exhaust gas to the mixing unit 123.

By providing such anode exhaust gas recycling means 122, surplus anode exhaust gas can be effectively recovered and recycled for reforming. Further, the hydrogen concentration in the reformed gas is reduced by N ₂ and CO ₂ in the anode exhaust gas, and the hydrogen conversion rate of methane and the like can be increased. Furthermore, since it becomes possible to supply more hydrogen than necessary to the fuel cell body, the flow rate of the reformed gas flowing in the fuel cell can be increased. When the flow velocity in the fuel cell is increased, it is possible to prevent water droplets generated at the portion from being blown off and a water curtain to be formed on the electrode, thereby reducing power generation efficiency.

  The self-oxidation internal heating steam reforming system of the present invention can be used to supply hydrogen-rich reformed gas to a load facility such as a fuel cell.

The basic process flow figure of a self-oxidation internal heating type steam reforming system. FIG. 3 is a cross-sectional view showing a specific structure of the first suction mixing unit 4 or the second suction mixing unit 6 in FIG. 1. The figure which shows the specific structure of the reforming means 1 shown in FIG. The process flow figure which shows the self-oxidation internal heating type steam reforming system which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reforming means 2 Water vapor generation means 2a Combustion part 3 CO reduction means 4 1st suction mixing means 5 Mixing means 6 2nd suction mixing means 7 Air supply system 8 Raw material gas supply system 9 Desulfurization apparatus 10 Water tank

12, 12a Heat exchange means 13 Heat exchange means 14 Control means 16, 17 Heat exchange means 18 Heat exchange means for dehydration 19 Heat exchange means for reheating 20 Ejector 21 Fixing part 22 Internal nozzle structure 23 External nozzle structure 24 , 25 Opening 26 Throttle part

31-39 Flow rate adjustment means 40 Water level detection means 41 Pressure detection means 42 Temperature detection means 52, 53 Control cable 61 Outer cylinder 61a First reaction chamber 62 Inner cylinder 62a Second reaction chamber 62b Partition wall 63 Oxygen-containing gas supply section 64-66 Manifold 68 Raw material supply part 69 Discharge part 69a Raw material supply part 70 Thermal insulation wall

71a Steam 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

101-115 Piping 120 Temperature raising means 120a Tank 120b Oxidation catalyst 122 Recycling means 123 Mixing means 300 Fuel cell

Claims (4)

In a self-oxidation internally heated steam reforming system configured to generate a hydrogen-rich reformed gas by auto-oxidizing the raw material gas in the presence of oxygen and steam reforming,
Mixing means 123 for mixing the raw material gas and the water vapor generated by the water vapor generating means 2 to obtain a raw material-water vapor mixture;
A reforming means 1 is provided that oxidizes a source gas contained in a source-steam mixture with an oxygen-containing gas supplied from the outside and generates a hydrogen-rich reformed gas by performing steam reforming of the source gas with reaction heat due to oxidation. ,
The reformed gas is supplied to the fuel cell 300,
Recycling means 122 for supplying at least part of the anode exhaust gas discharged from the fuel cell 300 to the reforming means 1 as the raw material gas is provided,
The steam generating means 2 includes a combustion section 2a for burning an air-fuel mixture obtained by mixing combustion air and fuel, and at least a part of the anode exhaust gas as the fuel is a combustion section of the steam generating means 2. Configured to supply to 2a ,
When surplus is generated in the water vapor generated by the water vapor generating means 2, the amount of anode exhaust gas supplied to the combustion section 2a is reduced so as to reduce the surplus, and the amount of anode exhaust gas supplied to the mixing means 123 is reduced. A self-oxidation internal heating steam reforming system, characterized in that it is provided with a control means 14 for controlling the increase of the steam. In claim 1,
The mixing means 123 includes first suction mixing means 4 that sucks a raw material gas into a water vapor flow to obtain a raw material-water vapor mixture, and the anode suction gas is sucked into the first suction mixing means 4. A self-oxidizing internal heating steam reforming system. In claim 1 or claim 2 ,
In order to obtain the air-fuel mixture, a self-oxidation internal heating steam reforming system is provided, wherein a second suction means 6 for sucking fuel into the combustion air is provided. In any one of Claims 1 thru | or 3 ,
A pressure detection means 41 for detecting the pressure of water vapor generated by the water vapor generation means 2 and a control means 14 for receiving a detection signal of the pressure detection means 41 are provided, and the detection pressure of the pressure detection means 41 is preset. When the value rises above the value, the control means 14 decreases the supply amount of the anode exhaust gas to the combustion section 2a and increases the supply amount of the anode exhaust gas to the mixing means 123 so that the detected pressure becomes the set value. A self-oxidation internal heating steam reforming system characterized by performing control.

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