JP4804900B2 - Oxygen supply pipe structure of reformer - Google Patents

Description

  The present invention relates to a reformer that generates a hydrogen-rich reformed gas by steam reforming a raw material gas, and in particular, the reformer is of a self-oxidation internal heating type and supplies oxidizing air therein. The present invention relates to an oxygen supply pipe structure.

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 further converted into CO ₂ by reacting a small amount of CO (carbon monoxide) contained therein with an oxygen-containing gas in the presence of a catalyst by means of CO reduction means, In particular, for a solid polymer electrolyte fuel cell operating at a low temperature, it is suitably used as a fuel 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 such a reformer, a 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 650 to The range is 750 ° C.

  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 provided with a heating unit outside, and a reformed gas is generated by 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), oxygen is supplied to the partial oxidation reaction layer through an oxygen supply pipe, and the heat generated there is used on the downstream side. The deployed steam reforming reaction layer is heated to the steam reforming reaction temperature, and the 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 + 12 · O 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 reformer of this patent document includes a so-called pre-reforming chamber and a main reforming chamber, and the pre-reforming chamber is provided with a raw material-steam mixture supply section, a reforming catalyst layer, and a discharge section. Are 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 reformed gas discharge portion.

  FIG. 6 is a cross-sectional view schematically showing a conventional self-oxidation internal heating type reformer. The reformer 1 includes an outer preliminary reforming chamber 2 and an inner main reforming chamber 3 arranged in a double cylinder shape, and a reforming catalyst layer 4 is provided in the preliminary reforming chamber 2. Further, a mixed catalyst layer 5 and a shift catalyst layer 6 in which a reforming catalyst and an oxidation catalyst are mixed are provided. The shift catalyst layer 6 includes a high temperature shift catalyst layer 7 and a low temperature shift catalyst layer 8.

The reforming catalyst is a steam reforming of the raw material gas. For example, a Ni-based reforming reaction catalyst such as NiO—Al ₂ O or NiO—SiO ₂ .Al ₂ O ₃ or WO ₂ —SiO ₂ .A1 ₂ O _3. NiO-WO ₂ / SiO ₂ / A 1 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% 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 about 5% ± 2%. In the case of methanol, the mixing ratio is about 2% ± 1%.

  A raw material-steam mixture supply unit 9 is provided at the lower part of the preliminary reforming chamber 2, and a discharge unit 10 for discharging the effluent after the preliminary reforming is provided at the upper part of the preliminary reforming chamber 2. An upper portion of the main reforming chamber 3 is provided with a supply portion 11 communicating with the discharge portion 10 of the preliminary reforming chamber 2, and an oxygen-containing gas such as air is supplied to the central portion of the main reforming chamber 3 for oxidation. The supply pipe 14 is extended. Further, a reformed gas discharge section 12 is provided in the lower part of the main reforming chamber 3.

The main reforming chamber 3 mixed catalyst layer 5 in this order from top to bottom, although the high-temperature shift catalyst layer 7 and the low-temperature shift catalyst layer 8 is provided, the low-temperature shift catalyst layer 8 including the boundary portion and the discharge portion 12 of the catalyst layers A support plate 15 for supporting the catalyst particles is disposed on the lower side. (Similar support plates 15 are also disposed in the pre-reforming chamber 2.) These support plates 15 have a gas flowability but have a hole diameter that does not allow catalyst particles to pass through. Porous members such as mesh and mesh are used.

  The discharge unit 12 includes a manifold provided in a space below the support plate 15 and an outlet tank connected to an end portion of the manifold extending outside the reformer 1. Then, the reformed gas that has flowed out to the discharge section 12 passes through the support plate 15 and enters the manifold, and is discharged from there through the outlet tank.

  On the other hand, a starting preheater 13 is connected to the upper portion of the main reforming chamber 3. The preheater 13 quickly raises the mixed catalyst layer 5 to the oxidation reaction temperature when the system is started up. An electric heater is disposed inside the preheater 13 and an oxidation catalyst such as platinum (Pt) or palladium (Pd) is provided. Filled. At the time of startup, the preheater 13 is supplied with raw material gas and start air, and the raw material gas undergoes an oxidation reaction with oxygen in the air. It comes to heat.

On the other hand, water vapor from a water vapor generating means (not shown) and raw material gas from a raw material supply part are introduced into a fluid introducing part of a suction mixing means constituted by an ejector. Further, the discharge part of the suction mixing means is communicated with the supply part 9 of the preliminary reforming chamber 2.

  Next, the operation of the reformer 1 of FIG. 6 will be schematically described. The raw material-steam mixture supplied from the supply unit 9 is partly reformed by the action of the reforming catalyst 4 in the preliminary reforming chamber 2 to generate a hydrogen-rich reformed gas. The quality gas and the remaining raw material-steam mixture flow from the discharge unit 10 to the supply unit 11 of the main reforming chamber 3.

  The raw material-steam mixture flowing into the main reforming chamber 3 reacts with the oxygen in the air (oxidation reaction) due to the action of the oxidation catalyst contained in the mixed catalyst layer 5, and the raw material gas is generated by the oxidation heat. Reacts with water vapor (reforming reaction) to generate reformed gas. The generated reformed gas converts CO (carbon monoxide) remaining in the high temperature shift catalyst layer 7 into hydrogen, and then further converts the remaining CO into hydrogen in the low temperature shift catalyst layer 8 to be discharged from the discharge unit 12 to the outside. Is done.

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

  A supply pipe 14 for supplying an oxygen-containing gas such as oxidizing air in the conventional reformer 1 is extended to the center of the main reforming chamber 3. A plurality of air holes are opened at the tip of the supply pipe, and oxygen is supplied from the air holes to the mixed catalyst layer 5 including the oxidation catalyst. In general, a round pipe is used as the supply pipe 14, but in order to supply oxygen uniformly to the mixed catalyst layer 5, a plurality of air holes are formed in a plurality of flat tubes, and oxygen is dispersed therefrom. It is preferable to supply. In that case, the pipe connected from the outside to the flat tube is preferably a round tube having a circular cross section. This is because the round tube requires less space and the bent portion can be easily arranged.

  However, when a round tube and a plurality of flat tubes are connected, it is difficult to evenly distribute air to the plurality of flat tubes, and even within a single flat tube, air can be distributed uniformly to each part of the cross section. difficult. In general, as a countermeasure, it is conceivable to connect the connecting portion between the round tube and the flat tube in a funnel shape. Alternatively, a special header may be provided, and a baffle plate or the like may be provided in the header. In these cases, however, the structure is complicated, the number of parts is increased, and there is a disadvantage that the reliability is insufficient. Therefore, an object of the present invention is to solve these problems.

In the present invention, a mixed catalyst layer 5 of a reforming catalyst and an oxidation catalyst and a shift catalyst layer 6 are sequentially provided inside, and the raw material gas is supplied to the mixed catalyst layer 5 while supplying oxygen via an oxygen supply pipe. In the oxygen supply pipe structure of a self-oxidation internal heating type reformer that generates hydrogen-rich reformed gas by steam reforming,
The oxygen supply pipe includes a flat pipe 14a having closed end faces 26 at both ends, and a plurality of oxygen outflow holes 27 that are opened apart from the mixed catalyst layer at the downstream end of the flow path in the flat pipe 14a. An oxygen supply inlet pipe 30 that penetrates the flat tube 14a parallel to the short axis of the cross section at the upstream end of the flow path, and is formed on the closed end face 26 side adjacent in the through portion of the inlet pipe 30. The oxygen supply pipe structure of the reformer comprises oxygen inlet holes 31 for injecting oxygen toward the closed end face 26 and inverting and dispersing the oxygen at the closed end face 26 (Claim 1).

In the above configuration, the flat tube 14a is erected vertically in each of the catalyst layers 5 and 6, penetrates the inlet pipe 30 at the lower end thereof, and the oxygen inlet on the lower surface side of the through portion of the inlet pipe 30. A hole 31 is provided, and an inner fin 28 can be provided in the middle portion of the flow path in the flat tube 14a (claim 2).
Further, in the configuration, a plurality of the flat tubes 14a can be arranged in parallel, the inlet pipes 30 can be passed through the respective flat tubes 14a, and the oxygen inlet holes 31 can be provided in the respective through portions. (Claim 3).

  The oxygen supply pipe structure of the reformer of the present invention has a closed end face that penetrates the flat pipe 14a through the inlet pipe 30 parallel to the short axis of the cross section at the upstream end in the flat pipe 14a. Since the oxygen inlet hole 31 is provided on the side 26 and the oxygen ejected from the oxygen inlet hole 31 is inverted and dispersed at the closed end face 26, the oxygen is uniformly distributed to each part of the cross section of the flat tube 14a for supplying oxygen. be able to. As a result, oxygen flows out uniformly from a large number of oxygen outflow holes 27 provided at the downstream end of the flat tube 14a, uniformly supplies oxygen to the oxidation catalyst of each part, and efficiently reforms the raw material gas with steam. Hydrogen-rich reformed gas can be generated. In addition, the above structure allows the inlet pipe 30 to pass through the flat tube 14a in parallel with its short axis, so that the structure is simple and reliable.

In the above configuration, when the flat tube 14a is erected vertically in each of the catalyst layers 5 and 6, the inlet pipe 30 is attached to the lower end portion thereof, and the inner fin 28 is provided in the flat tube 14a, The oxygen in the flat tube 14a can be efficiently heated uniformly by the inner fin 28, and the oxidation catalyst can be efficiently heated by the oxygen. At the same time, deformation of the flat tube due to heat can be prevented.
In the above configuration, in the case where the inlet pipe 30 is passed through a plurality of parallel flat tubes 14a and the oxygen inlet holes 31 are respectively provided in the through portions, oxygen is uniformly distributed to the flat tubes 14a, which is efficient. A reformer can be provided.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a reformer having an oxygen supply pipe according to the present invention, an enlarged view of the lower part thereof, and an enlarged perspective view of a part C cut away, FIG. 2 is a sectional view taken along line II-II in FIG. Is a sectional view taken along line III-III in FIG. 1, and FIG. 4 is a sectional view taken along line VI-VI in FIG. In these drawings, the same parts as those of the reformer 1 shown in FIG. 6 described above are denoted by the same reference numerals, and redundant description of the structure and operation is omitted as much as possible.

  The reformer 1 of the present embodiment has an outer cylinder 2a having a rectangular cross section and two inner cylinders 3a housed therein, and a preliminary reforming chamber 2 is provided outside the inner cylinder 3a, and the inner cylinder 3a. The main reforming chamber 3 is provided inside, two main reforming chambers 3 exist, and both the reforming chambers 3 are connected to each other at the lower part. Further, the outer preliminary reforming chamber 2 surrounds each main reforming chamber 3 and is connected in the shape of a cross section as shown in FIG. Three or more main reforming chambers can be provided. A raw material-steam mixture supply unit 9 is provided at the lower portion of the outer pre-reformation chamber 2, and a plurality of supply holes 9a are formed therein. A discharge unit 10 is provided in the upper portion of the preliminary reforming chamber 2. Each supply unit 9 is connected to a common pipe through which a raw material-water vapor mixture from a suction mixing means (not shown) flows.

  The heat transfer particle layer 4a is provided on the support plate 15 near the supply unit 9, and the reforming catalyst layer 4 supported by the support plate 15 is provided above the heat transfer particle layer 4a. The heat transfer particle layer 4a is formed of a layer of ceramic particles, for example, and transfers the thermal energy of the low temperature shift catalyst layer 8 to the preliminary reforming chamber 2 to raise the temperature of the reforming catalyst 4 and the supplied raw material-steam mixture. .

  A supply unit 11 communicating with the discharge unit 10 is provided in the upper part of the main reforming chamber 3. A mixed catalyst layer 5, a high temperature shift catalyst layer 7, and a low temperature shift catalyst layer 8 are sequentially provided below the supply unit 11, and the high temperature shift catalyst layer 7 and the low temperature shift catalyst layer 8 constitute a shift catalyst layer 6. . Since the mixed catalyst layer 5 needs to monitor and control its oxidation reaction temperature, reforming reaction temperature, etc., each mixed catalyst layer 5 is provided with a temperature sensor 16 such as a thermistor or a thermocouple.

  A flat tube 14 a is erected at the center of the two inner cylinders 3 a as shown in FIG. 1, and passes through the shift catalyst layer 6 and reaches the upper end of the mixed catalyst layer 5. The upper end and the lower end of the flat tube 14a are respectively closed by a closed end face 26. The closed end face 26 is composed of an end lid that matches the cross section of the flat tube 14a. The flat tube 14a is arranged on the center line of the inner cylinder 3a having a rectangular cross section as shown in FIG. Further, an inner fin 28 is inserted in an intermediate portion in the flat tube 14a, and oxygen 29 passing therethrough is heated by the heat of the shift catalyst layer. At the same time, deformation of the flat tube 14a due to thermal strain is prevented. As shown in FIG. 2, a plurality of oxygen outflow holes 27 made up of a plurality of small holes are arranged in parallel in the horizontal direction at the upper end on the downstream side of the flat tube 14a. Then, the oxygen outflow holes 27 are opened in the mixed catalyst layer 5. The diameter of the oxygen outflow hole 27 is smaller than the diameter of the mixed catalyst layer 5.

  An inlet pipe 30 formed of a round pipe shown in FIGS. 1C and 1B and FIG. 2 passes through the center of the flat side surface of the lower end portion, which is the upstream side of the flat tube 14a. In addition, the hole edge part of the through-hole is burring processed outside. Both ends of the inlet pipe 30 are closed, and one end of the supply pipe 14 communicates with the center in the longitudinal direction. The supply pipe 14 is bent in an L shape. Next, a plurality of oxygen inlet holes 31 are formed in the through portion where the inlet pipe 30 penetrates the flat tube 14a as shown in FIGS. 1 (C) and 1 (B). The oxygen inlet hole 31 is formed on the closed end face 26 side adjacent to the inlet pipe 30 as shown in FIGS.

  In this example, a pair of holes are formed on the letter C in a diagonally downward direction of the inlet pipe 30. The diameter of the oxygen inlet hole 31 is made sufficiently smaller than the cross-sectional diameter of the inlet pipe 30, and oxygen (generally air containing oxygen) ejected from the oxygen inlet hole 31 collides with the opposite closed end face 26 and reverses. The flat tube 14a is configured so as to be distributed uniformly in each part of the cross section of the flat tube 14a. The oxygen 29 is heated by passing through the inner fin 28 of the flat tube 14 a, flows out uniformly from a large number of oxygen outlet holes 27 provided at the downstream end thereof, and is supplied to the oxidation catalyst of the mixed catalyst layer 5.

  Next, the regions of the two main reforming chambers 3 where the lower portions of the low temperature shift catalyst layer 8 are respectively arranged are communicated with each other to form a common portion 12b, whereby the lower portions of the two low temperature shift catalyst layers 8 are Commonized. The common portion 12b constitutes a part of the reformed gas discharge section 12, and the discharge pipe 20 is inserted into the common portion 12b from the outside. The tip of the discharge pipe 20 is closed, and as shown in FIGS. 1 (B) and 5, a slit 20a parallel to the axis is provided in the insertion portion so as to face the bottom surface 12a of the common portion 12b. From there, the reformed gas flows into the discharge pipe 20.

Instead of the elongated slit 20a, a number of holes (not shown) can be provided apart from each other in the longitudinal direction of the discharge pipe 20. The size of the slit 20a and the number of holes (opening size) is set in a range in which the catalyst particles filled in the low temperature shift catalyst layer 8 do not flow into the exhaust pipe 20 along with the reformed gas.

When setting the size of the slit 20a or the hole to a range where the catalyst particles do not flow into the exhaust pipe 20 along with the reformed gas, the processing capacity is prevented by preventing the desired reformed gas from flowing into the exhaust pipe 20. It is desirable that the range does not decrease and the catalyst particles do not flow in. The range can be confirmed by experiments or the like.

  The reformer having an oxygen supply pipe of the present invention can be used for a self-oxidation internal heating type reformer that generates a hydrogen-rich reformed gas by steam reforming a raw material gas. Note that air containing oxygen can be circulated in the oxygen supply pipe.

The longitudinal cross-sectional view and lower part enlarged view of the reformer which have the oxygen supply pipe | tube of this invention, and the C section enlarged perspective view which fractured | ruptured one part. II-II sectional view taken on the line of FIG. III-III sectional drawing of FIG.

FIG. 6 is a sectional view taken along line VI-VI in FIG. The VV cross-sectional enlarged view of FIG. Sectional drawing which shows the conventional auto-oxidation internal heating type reformer typically.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reformer 2 Preliminary reforming chamber 2a Outer cylinder 3 Main reforming chamber 3a Inner cylinder 4 Reforming catalyst layer 4a Heat transfer particle layer 5 Mixed catalyst layer 6 Shift catalyst layer 7 High temperature shift catalyst layer 8 Low temperature shift catalyst layer 9 Supply Part 9a hole
10 Discharge section

11 Supply section
12 Discharge section
12a Bottom
12b common parts
13 Preheater
14 Supply pipe
14a flat tube
15 Support plate
16 Temperature sensor
20 discharge pipe
20a slit
26 Closed end face
27 Oxygen outflow hole
28 Inner fin
29 Oxygen
30 inlet pipe
31 Oxygen inlet hole

Claims (3)

A mixed catalyst layer 5 of a reforming catalyst and an oxidation catalyst and a shift catalyst layer 6 are sequentially provided inside, and the raw material gas is steam reformed while supplying oxygen to the mixed catalyst layer 5 through an oxygen supply pipe. In the oxygen supply pipe structure of a self-oxidation internal heating type reformer that generates hydrogen-rich reformed gas,
The oxygen supply pipe includes a flat tube 14a having closed end faces 26 at both ends, and a plurality of oxygen outflow holes 27 that are opened apart from the mixed catalyst layer at the downstream end of a flow path in the flat tube 14a. An oxygen supply inlet pipe 30 that penetrates the flat tube 14a parallel to the short axis of the cross section at the upstream end of the flow path, and is formed on the closed end face 26 side adjacent in the through portion of the inlet pipe 30. An oxygen supply pipe structure of a reformer comprising: an oxygen inlet hole 31 for injecting oxygen toward the closed end face 26 and inverting and dispersing oxygen at the closed end face 26. In claim 1,
The flat tube 14a is erected vertically in the catalyst layers 5 and 6, the inlet pipe 30 penetrates at the lower end thereof, and the oxygen inlet hole 31 is provided on the lower surface side of the through portion of the inlet pipe 30. A reformer oxygen supply pipe structure in which an inner fin 28 is provided in the middle of the flow path in the flat pipe 14a. In claim 2,
A reformer oxygen supply pipe structure in which a plurality of the flat tubes 14a are arranged in parallel, the inlet pipe 30 penetrates each flat tube 14a, and the oxygen inlet hole 31 is provided in each through portion.

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