JP2007186351A - Reformer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the deformation of a supply pipe for supplying oxidation air in a self-oxidation internal heating type reformer. <P>SOLUTION: In the self-oxidation internal heating type reformer 1, in which the supply pipe 14 for supplying oxidation air is extended into a mixed catalyst layer 5 arranged in a main reforming chamber 3 and a plurality of air ejecting holes 17 are provided in the extended part of the supply pipe 14, the cross section of the supply pipe 14 is made flat and a plurality of rows of the plurality of air ejecting holes 17 are provided in each of both walls of the major diameter side of the supply pipe 14, and a supporting part 19 having gas permeability is provided between the rows of the air ejecting holes 17 so as to prevent the mutual approximation of the both walls. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a self-oxidation internal heating type reformer that generates a hydrogen-rich reformed gas by steam reforming a raw material gas, and in particular, prevents thermal deformation of a supply pipe that supplies oxidized air, The present invention relates to a self-oxidation internal heating type reformer that facilitates circulation.

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 to CO ₂ by reacting residual CO (carbon monoxide) with an oxygen-containing gas in the presence of a catalyst by means of CO reduction, and operates at a particularly low temperature. For solid polymer electrolyte fuel cells, CO is reduced to several ppm level before being supplied as fuel. 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, 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 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), and the steam reforming reaction layer disposed on the downstream side using the heat generated in the partial oxidation reaction layer is subjected to a steam reforming reaction. Heating to a temperature is performed, and a steam reforming reaction is performed in the heated steam reforming catalyst layer to generate a hydrogen-rich reformed gas.

The partial oxidation reaction can be represented by CH ₄ + 1/2 · O ₂ → CO + 2H ₂ , and the preferable 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 have a double structure including an outer preliminary reforming chamber and an inner main reforming chamber. The main reforming chamber is provided with a catalyst layer and a discharge unit, the main reforming chamber receives a discharge from the discharge unit, a supply pipe for oxidized air, a mixed catalyst layer in which the reforming catalyst and the oxidation catalyst are mixed, a shift catalyst layer, and A reformed gas discharge unit is provided.

  FIG. 5 is a cross-sectional view schematically showing a self-oxidation internal heating type reformer, and FIG. 6 is a cross-sectional view taken along line AA of FIG. The reformer 1 includes an outer preliminary reforming chamber 2 and an inner main reforming chamber 3 arranged in a double cylinder shape, and is formed thin as a whole. The preliminary reforming chamber 2 and the main reforming chamber 3 are each elongated and have a flat cross section (in the illustrated example, a flat square shape), and the cross sections thereof are substantially similar to each other. The preliminary reforming chamber 2 is formed between the outer cylinder 2a and the inner cylinder 3a, and the main reforming chamber 3 is formed inside the inner cylinder 3a. The reforming catalyst layer 4 is provided in the pre-reforming chamber 2, the mixed catalyst layer 5 and the shift catalyst layer 6 in which the reforming catalyst and the oxidation catalyst are mixed are provided in the main reforming chamber 3, and the shift catalyst layer 6 is shifted at a high temperature. The catalyst layer 7 and the low temperature shift catalyst layer 8 are configured. The catalyst filled in the catalyst layer is generally in the form of particles or honeycomb.

Reforming catalyst are those of the raw material gas to steam reforming, for example, _NiO-A1 2 _{O 3} or Ni-based reforming catalyst such as _{NiO-SiO 2 · A1 2 O} 3 and _{WO 2} -SiO 2 · _A1 2 O ₃ and NiO-WO ₂ · SiO ₂ · A1 ₂ O ₃ are 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 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. A supply unit 11 communicating with the discharge unit 10 of the preliminary reforming chamber 2 is provided above the main reforming chamber 3, and an oxygen supply pipe 14 for supplying oxidized air to the central portion of the main reforming chamber 3 is extended. In the portion where the oxygen supply pipe 14 extends to the mixed catalyst layer 5, an air ejection portion 17 composed of a plurality of nozzles is formed. Further, a reformed gas discharge section 12 is provided at the lower portion of the main reforming chamber 3. The cross section of the oxygen supply pipe 14 is formed in a flat shape (a flat square in the illustrated example), and is substantially similar to the cross sections of the preliminary reforming chamber 2 and the main reforming chamber 3.

  The main reforming chamber 3 is provided with a mixed catalyst layer 5, a high temperature shift catalyst layer 7 and a low temperature shift catalyst layer 8 in order from the top to the bottom, and the low temperature shift catalyst layer 8 including the boundary portion of each catalyst layer and the discharge portion 12. A support plate 15 for supporting the catalyst particles is disposed on the lower side. (It should be noted that a similar support plate 15 is also disposed in the pre-reforming chamber 2. Furthermore, it is not necessary to insert a support plate at the boundary of the shift layer.) Although these support plates 15 have gas flow properties, they are catalysts. The particles have a pore diameter that does not allow passage, and usually a porous member such as a plate-like punch metal or mesh is 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 unit 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 rapidly 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 start-up, the preheater 13 is supplied with the raw material gas and the start air from the suction mixing means 16, and the raw material gas is oxidized by oxygen in the air, and the mixed catalyst layer 5 can be oxidized by the high temperature gas generated by the oxidation heat. Heats up to a certain temperature.

  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 the fluid introducing part of the suction mixing means 16 constituted by an ejector. The discharge part of the suction mixing means 15 is communicated with the supply part 9 of the preliminary reforming chamber 2.

  Next, the operation of the reformer 1 of FIG. 5 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 a 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.

  7 is a partial cross-sectional view of the practical reformer 1, and FIG. 8 is a cross-sectional view taken along the line VIII-VIII of FIG. In the examples shown in these figures, the reformer 1 has a structure in which two thin reformers are stacked to increase the processing capacity per unit. The configuration and operation are shown in FIG. Is substantially the same. 7 and FIG. 8 that are the same as in FIG. 3 are assigned the same reference numerals as in FIG. Reference numeral 18 denotes a temperature detector such as a thermistor, which is used for temperature monitoring or temperature control of the reformer 1.

  As shown in FIGS. 7 and 8, the oxygen supply pipe 14 for oxidized air of this example is an air jet comprising a small through hole in a plane parallel to the major axis of the cross section of the portion extending into the mixed catalyst layer 5. Each group of holes 17 is provided. These air ejection holes 17 are arranged in two rows near the tip of the supply pipe, but three or more rows can also be arranged. The tip of the oxygen supply pipe 14 is closed by brazing or the like.

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

  In the mixed catalyst layer 5 of the reformer 1 as described above, heat generation due to the oxidation reaction and heat absorption due to the reforming reaction occur simultaneously. There is. For this reason, the temperature in the region close to the air ejection hole is high, and the temperature in the peripheral region far from it is lower than that, and there is a tendency that a temperature difference occurs between the two regions. When such a temperature difference occurs, the stress due to the difference in thermal expansion between the oxygen supply pipe 14 having a large thermal expansion coefficient made of metal such as stainless steel and the mixed catalyst layer 5 having a small thermal expansion coefficient supported on an inorganic carrier such as alumina. In addition, the oxygen supply pipe 14 may be deformed due to a temperature difference in each part of the oxygen supply pipe 14.

  Further, when the reformer 1 is operating at a high temperature due to a difference in thermal expansion between the mixed catalyst layer 5 having a small coefficient of thermal expansion and the inner cylinder 3a having a large coefficient of thermal expansion made of a metal such as stainless steel. When the reforming catalyst layer 5 sinks downward and the reformer 1 stops and is at a low temperature, the sinking does not recover and the oxygen supply pipe 14 may be deformed to be crushed from the surroundings. is there.

  FIG. 9 is a diagram schematically illustrating a state in which the oxygen supply pipe 14 is deformed by stress from the surroundings. FIG. 9A shows a case where the reformer 1 is stopped and kept at a temperature of about 150 ° C., for example. FIG. 9B shows a case where the reformer 1 is operating normally at about 700 ° C. FIG. 9C shows the case where the reformer 1 returns from the normal operation to the operation stop state again.

  First, assuming that the mixed catalyst layer 5 is at a normal level in the state of FIG. 9A, when the reformer 1 is in a high temperature state of FIG. 9B, the thermal expansion of the inner cylinder 3a is made of alumina or the like. Since it is larger than the thermal expansion of the mixed catalyst layer 5 supported on the inorganic carrier, as a result, the mixed catalyst layer 5 sinks downward in the inner cylinder 3a as shown in the figure. That is, since the entire volume of the mixed catalyst layer 5 hardly changes, the upper surface of the mixed catalyst layer 5 is lowered by an amount corresponding to an increase in the inner diameter of the inner cylinder 3a.

  Even when the reformer 1 returns to the low temperature state shown in FIG. 9C, the entire volume of the mixed catalyst layer 5 submerged in the inner cylinder 3a hardly changes. The inner cylinder 3a cannot be restored to its original state due to the mixed catalyst layer 5 expanded to the extent that it deforms so as to bulge outward. Due to this deformation, an inward stress is generated, and the stress is applied to the oxygen supply pipe 14 through the mixed catalyst layer 5 to deform the oxygen supply pipe 14 from the outside. It has been found that the extent of this deformation is greatest in the region near the air ejection hole 17 of the oxygen supply pipe 14.

  When the oxygen supply pipe 14 is deformed, the supply capacity of the oxidized air is lowered, and the air ejection may be uneven. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a reformer having a new structure for solving the problem in the oxidizing air supply pipe in the conventional self-oxidation internal heating type reformer. To do.

  In the reformer of the present invention that solves the above-described problem, a supply pipe for supplying oxidized air is extended into a mixed catalyst layer disposed in a main reforming chamber, and a plurality of air ejection holes are formed in the extended portion of the supply pipe. Is a self-oxidation internal heating type reformer. The supply pipe has a flat cross section, and a plurality of rows of air ejection holes are provided in both walls parallel to the major axis of the cross section, preventing the both walls from approaching each other, and The support part which enables distribution | circulation is arrange | positioned between the row | line | columns of the said air ejection hole (Claim 1), It is characterized by the above-mentioned.

  In the reformer, the support portion may be a plurality of dimples formed in a row at predetermined intervals on both walls, or a fin or spacer having a corrugated cross section disposed between both walls.

  In the reformer, the pitch of the plurality of dimples, fins, or spacers can be 25 times or less the plate thickness of the supply pipe.

  In the reformer of the present invention, the supply pipe has a flat cross section, and a plurality of rows of air ejection holes are provided on both walls parallel to the major axis, thereby preventing the walls from approaching each other. Further, the present invention is characterized in that a support portion that enables gas flow is disposed between the rows of the air ejection holes. With this configuration, even if stress from the outside is applied to both walls parallel to the long diameter of the supply pipe due to differences in thermal expansion of the supply pipe, the mixed catalyst layer, the inner cylinder, and the like, Deformation can be prevented.

  In the reformer, the support portion may be a plurality of dimples formed in a row at predetermined intervals on both walls, or a fin or spacer having a corrugated cross section disposed between both walls. By using such a plurality of dimples, fins or spacers, it is possible to easily configure a support portion having gas flowability and a high deformation preventing function.

  In the above reformer, if the pitch of the plurality of dimples, fins or spacers is 25 times or less the plate thickness of the supply pipe, the support section can surely exhibit a practically sufficient deformation preventing function.

  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 specifically showing a supply pipe portion in the reformer of the present invention and a partially enlarged view thereof, and FIG. 2 is a sectional view taken along the line II-II in FIG. 1 and a partially enlarged view thereof. The reformer 1 shown in these figures is the same as the reformer 1 shown in FIGS. Therefore, the same parts are denoted by the same reference numerals, and redundant description is omitted as much as possible. The reformer 1 to which the present invention can be applied is not limited to such a double structure, but the pre-reforming chamber 2 and the main reforming chamber 3 are configured as separate bodies, or the pre-reforming. The present invention can also be applied to a configuration in which steam reforming is performed only in the main reforming chamber 3 without the chamber 2. Therefore, the “main reforming chamber 3” in which the oxygen supply pipe 14 in the present invention is disposed is the main main chamber disposed separately from the main reforming chamber 3 disposed inside the double structure as shown in FIG. This means that the reforming chamber 3 or the main reforming chamber 3 having no preliminary reforming chamber 2 is included.

  The oxygen supply pipe 14 for oxidized air provided in the reformer 1 of the present invention is extended in parallel with the longitudinal direction of the main reforming chamber 3 surrounded by the inner cylinder 3a and along the central portion thereof, and its distal end side. Reaches the upper part of the mixed catalyst layer 5, and the tip thereof is closed by brazing of the upper lid 14a (FIG. 1B). The cross section of the oxygen supply pipe 14 is flat, and a portion extending into the mixed catalyst layer 5 is provided with a large number of air ejection holes 17 consisting of through holes on both walls parallel to the major axis of the cross section. As shown in FIG. 2 (A), these air ejection holes 17 are provided in two rows in parallel on both walls of the oxygen supply pipe 14, respectively. In the first row, 13 are arranged in this example, and in the second row, Twelve air ejection holes 17 are arranged at regular intervals. The cross section of the oxygen supply pipe 14 may be a flat square shape, a flat elliptical shape, or an arc shape only at the major axis end of the cross section.

  Between the two rows of the air ejection holes 17, a pair of frustoconical (conical frustoconical) support portions 19 that prevent the two walls from approaching each other and ensure the flow of gas from both walls. It is recessed and its opposite surface is in contact. The illustrated support portion 19 is constituted by a plurality of (in this example, 13) dimples 20 arranged in a row at a predetermined interval. As shown in FIG. 1B, these dimples 20 have a shape in which both walls of the oxygen supply pipe 14 are pushed in from the outside to the inside, and the tip portions of the opposing dimples 20 are in close contact with each other. It is brazed. By providing such a support portion 19, external force applied from both sides of the cross-section in the minor axis direction is received by the support portion 19, and deformation of the oxygen supply pipe 14 is prevented by the support force. Further, since the dimples 20 are separated from each other at a predetermined interval, the internal gas flowability is not impaired. Each dimple 20 can be formed, for example, by pressing the major axis of the oxygen supply pipe 14 from the outside.

  The oxygen supply pipe 14 is easily subjected to stress in the region near the air ejection holes 17 as described above. However, by arranging the support portions 19 between the rows of the air ejection holes 17 as described above, the resistance force against the stress can be increased. It can increase mainly in the area. In the present embodiment, two rows of air ejection holes 17 are provided on both walls of the oxygen supply pipe 14, but three or more rows may be provided. In the case where three or more rows of air ejection holes 17 are provided, a support portion 19 may be provided for each of those rows.

  In the present embodiment, the support portion 19 is provided between the rows of the air ejection portions 17. However, as shown in the figure, the other portion of the mixed catalyst layer 5 and the region of the shift catalyst layer 6 (particularly the high temperature shift catalyst layer 7). In addition, it is also possible to arrange the support portions 19 in an arrangement in which no deviation occurs in the air flow and to reinforce those regions. In some cases, the support portions 19 other than those between the rows can be omitted. Further, the inner fins 22 may be disposed on the shift catalyst layer 6.

  The plane shape of the dimple 20 may be any shape such as a circle, an ellipse, a rectangle, or a polygon. Further, in the case of the plane dimension, for example, a circle, the diameter of the plane is preferably about 2 to 10 times the plate thickness. Further, when a plurality of dimples 20 are used as the support portion 19, according to an experiment, the pitch (interval between the centers of adjacent dimples 19) is determined by changing the thickness of the oxygen supply pipe 14 (the thickness of the minor axis differs from that of the major axis) In this case, it has been confirmed that a sufficient reinforcing effect is exhibited by setting it to 25 times or less of the plate thickness on the major axis side). For example, when the thickness of the oxygen supply pipe 14 is 0.8 mm, the pitch of the dimples 20 is desirably 20 mm or less.

  FIG. 3 shows another embodiment of the reformer 1 of the present invention according to FIG. 3 differs from the structure shown in FIG. 2 in the shape of the support portion 19 provided in the oxygen supply pipe 14, and the other configuration is the same. The support portion 19 is constituted by a corrugated fin 21 elongated in the width direction as shown in FIG. 4A or an elongated rectangular fin 21 as shown in FIG. By arranging the peaks and valleys of the fin 21 in contact between both walls parallel to the long diameter of the oxygen supply pipe 14, the same reinforcing effect as in the example of FIG. 2 (FIG. 1) can be exhibited. . The support portion 19 may be a spacer instead of the fin 21. Such a spacer is not shown, but can be composed of, for example, a plurality of plates or bars that can be connected to or joined to at least one of the inner surfaces of both walls on the long axis side of the oxygen supply pipe 14.

  The reformer of the present invention can be used for a reformer that generates a hydrogen-rich reformed gas by steam reforming a raw material gas.

The longitudinal section showing an example of the reformer of the present invention. The right view of FIG. The side view which shows the other example of the reformer of this invention. The fragmentary perspective view of the fin 21 used as the support part 19 of FIG. Sectional drawing which shows a self-oxidation internal heating type reformer typically. AA sectional drawing of FIG. FIG. 2 is a partial cross-sectional view of a practical reformer 1. The right view of FIG. The figure which illustrates typically the state in which the oxygen supply pipe 14 receives a deformation | transformation with the stress from the circumference.

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 5 Mixed catalyst layer 6 Shift catalyst layer 7 High temperature shift catalyst layer 8 Low temperature shift catalyst layer 9 Supply unit 10 Discharge unit 11 Supply section 12 Discharge section

DESCRIPTION OF SYMBOLS 13 Preheater 14 Oxygen supply pipe 14a Top cover 14b Air introduction pipe 14c Manifold 15 Support plate 16 Suction mixing means 17 Air ejection part 19 Support part 20 Dimple 21 Fin 22 Inner fin 23 Heat insulating material 24 Oxidation air 26 Reformed gas

Claims (3)

  A supply pipe 14 for supplying oxidized air is extended into the mixed catalyst layer 5 disposed in the main reforming chamber 3, and a plurality of air ejection holes 17 are provided in the extended portion of the supply pipe 14. In the heating type reformer 1, the supply pipe 14 has a flat cross section, and a plurality of rows of air ejection holes 17 are provided on both walls on the long diameter side, and the both walls approach each other. A reformer characterized in that a support portion 19 that prevents gas flow and is arranged between rows of the air ejection holes 17 is provided.   2. The modification according to claim 1, wherein the support portion 19 is a plurality of dimples 20 formed in a row at predetermined intervals on the both walls, or fins 21 or spacers having a corrugated cross section disposed between the both walls. A genitalia.   3. The reformer according to claim 2, wherein the pitch of the plurality of dimples 20, fins 21, or spacers is 25 times or less the plate thickness of the supply pipe 14.

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