JP2006016256A - Auto-oxidation internal heating type reforming apparatus and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxidation/reforming reaction combination type reforming apparatus small-sized to be fitted to domestic use and having high thermal efficiency. <P>SOLUTION: The oxidation/reforming reaction combination type reforming apparatus is constituted so as to provide a primary reaction part and a secondary reaction part successively from the inside in the radius direction in the outside of a cylindrical reforming vessel inner cylinder, to arrange the primary reaction parts concentrically side by side in the vertical direction and to arrange a CO removing part provided with a CO removing catalyst concentrically in the vertical direction in the inside of the reforming vessel inner cylinder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reforming apparatus and method for generating hydrogen from fuels such as hydrocarbons, aliphatic alcohols, and dimethyl ether, and in particular, to provide a small and highly efficient reforming apparatus and method for general household use. To do.

A fuel cell is a power generation system that obtains an electromotive force from hydrogen and oxygen by the reverse reaction of water electrolysis, but a reformer that is an efficient generator of hydrogen for such a fuel cell or other purposes The provision of is now an increasingly important issue.
Since the capacity of the fuel cell as described above is small for household use, the reformer needs to be small in size accordingly. In such a small reformer, unless the heat loss is reduced, the reforming efficiency tends to decrease. Therefore, the area in contact with the outside air is reduced, or the mixed gas of the raw fuel and steam is vaporized. It is necessary to supply at the lowest temperature that can be present in order to make the temperature difference from the reformed gas discharged as small as possible. That is, the performance of a small reformer depends on how high the efficiency of heat exchange is.

The following three methods are known as a method for producing hydrogen by the reformer, if methane is given as a typical example of the raw material fuel.
First, the first method is to obtain hydrogen with the following general formula as the center using raw material fuel and water vapor.
_{CH 4 + 2H 2 O = CO} 2 + 4H 2 (1)
Since this reaction is highly endothermic, heating from the outside is required.
The second method is to obtain hydrogen around the following general formula.
_{CH 4 + O 2 = CO 2} + 2H 2 (2)
Since this reaction is an exothermic reaction, it does not require water vapor or heat from the outside when the reaction starts, but the thermal efficiency is not as high as that of the first method.
The third method uses both the first method and the second method. Both reactions occur in parallel so that heat is obtained by the second method and used as a heat source for the first method. This method is referred to as a partially oxidized internal heating type.
The above three methods merely show a central reaction as referred to as a general formula. Actually, depending on the reaction temperature and the type of catalyst, an intermediate reaction product may be generated or the temperature-dependent Reversible reactions
CO + H ₂ O = CO ₂ + H ₂ (3)
Alternatively, in the reaction using oxygen, that is, air, ammonia is also generated.

The present applicant belongs to the third method (combined oxidation and reforming method), and has proposed the invention of Japanese Patent Application No. 2002-143512 (Japanese Patent Laid-Open No. 2003-335504) as an efficient method for starting up the reaction. .
This is because a small amount of oxygen is mixed only in the raw material fuel and water vapor at the beginning, and the mixed gas is heated to a temperature higher than the ignition temperature by the oxidation catalyst (this is also a temperature increase only at the initial time), and then changed to the oxidation catalyst. Into the outer cylinder filled with the mixture of the catalyst, and a part of the raw material fuel is oxidized to generate heat to generate hydrogen, and this hydrogen is then mixed into the inner cylinder in which the oxidation catalyst and the reforming catalyst are mixed. The oxygen is allowed to flow in with oxygen (this oxygen itself is used in the steady operation stage) and is heated to generate heat. In the outer cylinder stage, the unreformed fuel is completely reformed, and the inner cylinder When the inner cylinder and the outer cylinder reach a predetermined temperature, the oxygen mixed into the supply gas is stopped, the oxygen supplied to the inner cylinder is increased, and the steady operation starts. Is.
JP 2003-335504 A

Although the prior invention of the present applicant as described above is an excellent method for starting the third method, the apparatus basically has two inner cylinders in one outer cylinder. Since it was a deployed form, it was still difficult to obtain a uniform temperature at each level in the outer cylinder.
In the prior invention, the intermediate part of the reforming vessel occupies the inner cylinder and the outer cylinder for the reaction. Therefore, in order to increase the heat exchange efficiency, preheat the raw fuel and oxygen with some heat source in the container. However, in order to arrange such a structure, the diameter of the reforming vessel is inevitably increased.
Further, in the invention of the prior application, as in the conventional example for carrying out the first to third methods, a catalytic oxidizer for reducing the carbon monoxide existing after reforming to a level of several ppm or less is a reformer. It was installed outside. For this reason, connection piping is necessary, heat loss from the piping and the catalyst oxidizer is large, and the volume of the entire reformer is large.

In view of the above, the first object of the present invention is to provide an outer cylinder (referred to herein as a primary reaction section) for a reformer (referred to herein as a self-oxidation internal heating type) for the third reaction type, In the arrangement structure of the inner cylinder (referred to as the secondary reaction section in the present application), since both are equally spaced not only in the vertical direction but also in the circumferential direction, heat transfer from the secondary reaction section to the primary reaction section It is to provide a device that is uniform.
A second object of the present invention is to provide an arrangement structure of a primary reaction section and a secondary reaction section that can arrange a catalytic oxidizer for reducing carbon monoxide in a reforming vessel.
The third object of the present invention is to provide a self-oxidation internal heating type reformer that does not significantly increase the volume of the reforming vessel while effectively preheating the raw fuel and / or oxygen for the oxidation reaction. It is to provide.

  According to the first aspect of the present invention, the primary reaction unit, the secondary reaction unit, and the primary reaction unit are sequentially arranged in the longitudinal direction in a concentric manner from the inside in the radial direction outside the inside of the cylindrical reforming vessel. A self-oxidation internal heating type reforming device is provided in which a reforming gas de-CO part having a de-CO catalyst layer is arranged in a concentric longitudinal direction inside the reforming vessel. .

  According to the second aspect of the present invention, the reformed gas guide path that passes through the de-CO part in the radial direction inside the de-CO part of the reformed gas in the longitudinal direction, oxygen mixture for reforming reaction The reforming apparatus according to claim 1, wherein the gas introduction paths are sequentially arranged.

  According to the third aspect of the present invention, the reformed gas guide path that has passed through the de-CO device, the concentric longitudinal direction outside the reformed gas de-CO device in the radial direction, and the primary gas mixture of the raw material fuel The ascending guide path to the reaction section is sequentially arranged in parallel, and a descending guide path for the mixed gas of the raw material fuel is formed between the ascending guide path and the inner primary reaction section. The reforming apparatus according to 2, is provided.

  According to the fourth aspect of the present invention, the raw material fuel partially reformed by the heat transfer particles and the reforming catalyst, which are maintained at a high temperature by heat transfer of the oxidation / reforming reaction and the shift reaction, during the steady operation, The mixed gas of water vapor is mixed with the oxygen mixed gas preheated by the heat at the time of steady operation of the de-CO device arranged in the reforming vessel, and this is mixed with the mixed catalyst of the oxidation catalyst and the reforming catalyst and the shift catalyst. A self-oxidation internal heating type reforming method is provided, characterized in that the reformed gas is obtained by flowing through the cylinders sequentially provided.

  According to a fifth aspect of the invention, there is provided the reforming method according to the sixth aspect, wherein the mixed gas of the raw fuel and the steam is preheated by heat generated by the de-CO device and / or transmission of heat transfer particles. Provided.

  According to the sixth aspect of the present invention, the oxidation reaction oxygen and the raw material fuel are initially flowed into the oxidation reaction oxygen introduction passage filled with the oxidation catalyst, and the raw material fuel is oxidized to obtain high-temperature oxygen. The mixed catalyst of the oxidation catalyst and the reforming catalyst and the shift catalyst are mixed with the mixed gas of the raw material fuel and the steam that has passed through the heat transfer particle layer and the reforming catalyst layer, which are the primary reaction part during normal operation. There is provided a method for starting up an internal heating type reformer characterized in that the temperature is raised in the reaction section while obtaining a reformed gas while flowing into a region that becomes a secondary reaction section during normal operation sequentially provided.

  According to the first aspect of the present invention, the primary reaction section and the secondary reaction section of the auto-oxidation internal heating type reformer are arranged in the cylindrical container at equal intervals in the longitudinal direction and the circumferential direction. In addition to expecting a uniform transfer of reaction heat, the reformer gas de-CO device with a de-CO catalyst layer is now compactly placed in the reforming vessel, reducing the volume associated with the reformer In addition, the reaction heat including the de-CO device can be used more effectively.

  According to the second aspect of the present invention, the oxygen mixed gas for the oxidation reaction can be effectively recovered, and the oxygen mixed gas is efficiently preheated. Therefore, the efficiency of the reforming reaction is also increased.

  According to the third aspect of the invention, the amount of heat contained in the reformed gas that has passed through the de-CO device can be effectively recovered into the mixed gas of the raw material fuel, and the mixed gas of the raw material fuel is efficiently preheated. The efficiency of the reforming reaction will also increase.

  According to the fourth aspect of the present invention, it is possible to reduce the heat of oxidation of the de-CO device arranged in the reforming vessel to the outside of the vessel, and the oxygen mixed gas for the oxidation reaction is preheated, so that the oxidation reaction A reforming method is provided in which is stable.

  According to the fifth aspect of the invention, the reforming method improves the reforming efficiency because the mixed gas of the raw material fuel and the steam is preheated by both the oxidation heat of the de-CO device and the heat transfer of the heat transfer particle layer. Is provided.

  According to the invention of claim 6, the reformer is provided by utilizing the oxygen introduction path for the oxidation reaction having a small thermal inertia without using the primary reaction section including the heat transfer particle layer or the like in a state where the temperature is lowered. Can be launched, so the startup time can be shortened.

  The present invention will be described in detail with reference to FIGS. 1 and 2, which are typical embodiments.

1. Structure of reformer The reformer according to the first embodiment of the present invention comprises a primary reaction in a cylindrical reformer 1 as shown in FIG. 1 from the radially outer side toward the radially inner side. Part 2, secondary reaction part 3, primary reaction part 2, reformed gas de-CO part 4 (note that this de-CO part is not only CO but also other unnecessary gases generated by the reaction, such as NH _3. In this case, it is also expressed as de-CO.sub.2), but the reformed gas guide path 5 and the oxidation reaction oxygen introduction path 6 that pass through the de-CO section are respectively appropriate annular walls. Etc. (if necessary, a heat insulating material is also attached) and are arranged in parallel in the vertical direction. That is, the present invention is characterized in that the reaction chambers and guide paths are all arranged concentrically.
The oxygen-mixing gas introduction path 6 for reforming reaction is located at the center of the cylindrical shape of the reforming vessel 1.

Further, the reforming vessel 1 has a mixed gas inlet 7 for raw material fuel, an air outlet for CO removal 8 as shown on the lower left side of FIG. 1, and a reformed gas outlet 9 as shown on the lower right side of FIG. In addition, an oxygen (air) inlet 10 for oxidation reaction is provided.
The CO air inlet 8 merges with the reformed gas from below the secondary reaction unit 3 inside the reforming vessel 1 and is supplied to the de-CO catalyst 18 of the de-CO unit 4. . Also, the oxidation reaction oxygen (air) inlet 10 communicates with the oxidation reaction oxygen introduction path 6 below the interior of the reforming vessel, and this oxygen introduction path 6 is located above the reforming vessel 1 in the secondary reaction section 3. The air is communicated with the blow ring 12. Further, the reformed gas guide path 5 that has passed through the de-CO 4 is connected to the reformed gas outlet 9 below the center of the reforming vessel 1.

From the upper side, the primary reaction unit 2 has the reforming catalyst layer 14 and the heat transfer particle layer 13, and from the upper side to the secondary reaction unit 3, the mixed (reforming / oxidation) catalyst layer 15, the heat transfer particle layer 13, the high temperature The shift catalyst layer 16 and the low temperature shift catalyst layer 17 are supported by appropriate means such as a lattice and a wire mesh, respectively. In addition, a heat insulating material 19 is disposed on the partition wall between the primary reaction section 2 and the secondary reaction section 3 as shown in FIG. 1, and the mixed catalyst layer 15 is maintained at a uniform temperature in the vertical direction. It has come to be.
The heat transfer particles increase the temperature of the raw material fuel mixed gas during steady operation, and a part thereof is reformed by an endothermic reaction using a reforming catalyst. The material has a thermal conductivity of 5 Kcal / mhr. SiC grains having an emissivity of 0.7 or higher are used. However, more recent materials with improved thermal conductivity (eg, 64.74 Kcal / mhr ° C.) can also be used. The heat transfer particles preferably have a particle diameter with a space ratio of about 0.4 and a large heat emissivity, for example, 0.85. Such a heat transfer particle layer is not only disposed as an independent heat transfer particle layer 13 in the lower part of the primary reaction unit 2 as shown in FIG. 1, but the upper reforming catalyst layer 14 is also a heat transfer particle layer. If the layers are configured as alternating layers, the heat transfer efficiency is further improved.
The CO removal unit 4 has a doughnut-shaped CO removal catalyst 18 disposed therein, and a heat insulating material 19 is disposed on the inner periphery and the ceiling. Note that, as described above, the de-CO unit 4 is merely described as a representative gas that is in the reformed gas and must be oxidized because it is unnecessary, and it treats NH _{3 and} other generated unnecessary gases (oxidation). ).

Since each part of the reforming apparatus remains at a low temperature from the start-up of the reforming apparatus of Example 1 to the steady operation and the necessary heat exchange cannot be performed, a special reaction method is continued for several minutes at the start-up, When each part reaches the required temperature, it is necessary to switch to steady operation.
1. Start-up method 1 (This is substantially the method disclosed in Japanese Patent Application No. 2002-143512, which is a prior application of the present applicant)
A reforming vessel containing raw material fuel that has been heated only at the beginning (as described above, hydrocarbon, aliphatic alcohol, dimethyl ether, etc.), water vapor and a small amount of mixed gas of oxygen (this small amount of oxygen is mixed only at startup) 1 is introduced from the raw material mixed gas inlet 7 on the lower left side. At this time, for example, although not shown, a starting oxidation catalyst is prepared at the lowermost portion of the primary reaction unit 2 so that the raw material fuel moves upward while generating heat due to the oxidation reaction. Since the reforming catalyst layer 14 is filled in the upper part, the raw material fuel is partially reformed by the heat. The partially reformed raw material fuel is introduced into the secondary reaction section 3 together with the oxygen for oxidation reaction, which is slightly suppressed at the beginning when it is blown from the blowing ring 12.

In the secondary reaction unit 3, self-oxidation internal heating type reforming and shifting are performed in the process of passing through the mixed catalyst layer (consisting of the reforming catalyst and the oxidation catalyst), the heat transfer particle layer, the high temperature shift catalyst layer, and the low temperature shift catalyst layer. Reaction takes place. The heat generated by this shift reaction rapidly heats the heat transfer particle layer 13 arranged in the primary reaction section 2 outside the heat.
On the other hand, the reformed gas flowing from the lower side of the secondary reaction unit 3 is de-CO in the process of ascending the de-CO unit at the center of the reforming vessel 1 and descends the gas guide path 5 passing through the de-CO unit 4. In the process leading to the reformed gas outlet 9, the oxygen for oxidation reaction is preheated. Accordingly, after the necessary temperature of each part is obtained by such a start-up operation, a steady operation is started.

2. Startup method 2
The following methods are also conceivable as startup methods.
An oxidation catalyst is filled in the oxidation reaction oxygen introduction path 6, and the oxygen and raw fuel mixture gas heated to 200 ° C. or higher is allowed to flow from the oxidation reaction oxygen inlet 10. Then, since the raw material fuel is oxidized by the oxidation catalyst and becomes high temperature, when this is led from the blowing ring 12 to the secondary reaction unit 3, the oxidation catalyst layer together with the mixed gas of the raw material fuel and water vapor via the primary reaction unit 2 And the reforming catalyst layer are introduced into a mixed catalyst layer to cause an oxidation / reforming reaction.
Thus, after the temperature of the required part of the reformer rises, the steady operation is performed.

Steady operation of the apparatus of Example 1 In the steady operation, only the raw material fuel and water vapor are taken in from the raw material fuel mixed gas inlet 7 and flowed through the primary reaction section 2, and the heat transfer particle layer 13 (heated state because of steady operation). The amount for the normal operation, which is preheated by the heat of the de-CO device during the normal operation, is led to the secondary reaction unit 3 The oxidized mixed gas is also led to the secondary reaction unit 3, and the reformed gas is obtained by sequentially flowing the mixed catalyst of the oxidation catalyst and the reforming catalyst of the secondary reaction unit 3 and the shift catalyst. This reformed gas is passed through a de-CO device, de-CO-treated, and then taken out of the reforming vessel 1.

When the raw material fuel is liquid, that is, when kerosene is used as usual, it is better to raise the reaction temperature of the secondary reaction section to about 730 to 750 ° C. For this purpose, the reforming catalyst layer of the primary reaction part (as described above, when this reforming catalyst layer is an alternate layer with the heat transfer catalyst layer, the alternate layer) is passed through paraffin which is the main component of kerosene. In converting naphthenes and aromatics to CH ₄ , it is desirable to perform partial reforming at a temperature of 500 to 550 ° C. This can be achieved by the sensible heat and internal heat transfer of the reformed gas in the secondary reaction section. However, the sensible heat of the reformed gas is converted into alternating layers of the heat transfer particle layer and the reforming catalyst layer (only the reforming catalyst layer). However, it is necessary to transfer heat sufficiently to the mixed gas of water vapor and hydrocarbon flowing in the alternating layer with the heat transfer particle layer.
On the other hand, the shift reaction is carried out in a high temperature shift reaction part (reaction temperature around 400 ° C.) and a low temperature shift reaction part (reaction temperature around 200 ° C.) CO + H ₂ O = CO ₂ + H _2.
However, since the current shift reaction catalyst does not proceed at a temperature of about 170 to 180 ° C. or less, it is taken out at this temperature and CO and NH ₃ are removed by the deCO catalyst of the deCO part 4. Etc. are preferably oxidized. Since the optimum temperature for catalytic oxidation of NH ₃ is about 190 ° C., the temperature to be transferred from the secondary reaction section to the de-CO section 4 is about 170 to 180 ° C., and this gas is an oxygen mixed gas necessary for oxidation Is preferably mixed and supplied to the de-CO catalyst 18 of the de-CO part 4.

Structure of the reformer In the reformer of the embodiment shown in FIG. 2, the reformed gas that has passed through the de-CO 4 is not only the guide path 5 on the radially inner side of the de-CO 4 but also the de-CO 4 The annular guide passages 21 and 22 are sequentially arranged in parallel to the outside of the guide passage 20 and the radially outer side of the guide passage 20 outside the guide passage 20, and the raw material from the raw fuel mixed gas inlet 7. After the fuel mixed gas rises concentrically in the radially outer guide path 21 of the reformed gas guide path 5 that has passed through the de-CO section 4 radially outside the de-CO section 4 and undergoes heat exchange. The structure is the same as that of the embodiment shown in FIG. 1 except that the outer side is again lowered concentrically by the guide path 22.

Start-up of the reforming apparatus of Example 2 The start-up method of the apparatus when each part of the reforming apparatus has not reached the required temperature is the same as that in Example 1, and is therefore omitted.
Steady operation of the reformer of the second embodiment The basic operation method is the same as that of the reformer of the first embodiment. However, in the reformer of the second embodiment, only the oxygen for oxidation reaction can be used in the steady operation stage. In addition, when the raw material fuel mixed gas ascends the guide path 21, heat exchange with the reformed gas passing downward through the guide path 20 outside the de-CO unit 4 and the reformed gas exiting the reforming vessel is performed. Reduce the temperature. In this case, since there is a large temperature difference between the raw fuel mixed gas descending the guide path 22 and the reforming catalyst layer 14 located on the outer side in the radial direction, it is desirable to dispose a heat insulating layer on the annular wall between them. . Such a reforming apparatus of Example 2 is particularly suitable when NH ₃ is generated as an unnecessary gas in the reaction section. This is because in order to remove NH ₃ by oxidation, a higher temperature is required than the usual removal by oxidation of CO. Therefore, the temperature of the final exhaust reformed gas also becomes higher. This is because it is desirable that the reformed gas that has passed through the de-CO unit 4 (in this case, the weight of the de-NH ₃ unit is increased) is subjected to more heat exchange to lower the temperature. Therefore, it can be said that the heat exchange structure of Example 2 is particularly suitable when there is a lot of NH ₃ oxidation treatment in view of its heat exchange efficiency.

1 is a longitudinal sectional view of a reformer according to a first embodiment of the present invention. It is longitudinal direction sectional drawing of the reformer which concerns on 2nd Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reforming container 2 ... Primary reaction part 3 ... Secondary reaction part 4 ... De-CO part 5 ... Reformed gas guide way which passed through the de-CO part 4 6 ... Oxygen introduction passage for oxidation reaction 7 ... Raw material fuel mixed gas Inlet 8 ... De-CO air inlet 9 ... Reformed gas outlet 10 ... Oxidation reaction oxygen inlet 12 ... (Oxidation reaction oxygen) blowing ring 13 ... Heat transfer particle layer 14 ... Reforming catalyst layer 15 ... Mixing (oxidation and modification) Quality) catalyst layer 16 ... high temperature shift catalyst layer 17 ... low temperature shift catalyst layer 18 ... de-CO catalyst 19 ... heat insulating material 20 ... (outside) guide path of reformed gas through de-CO part 4 21 ... raw material fuel mixed gas Ascending guide path 22 ... Descent guiding path of the raw fuel mixed gas

Claims (6)

  A primary reaction part, a secondary reaction part, and a primary reaction part are sequentially arranged in a longitudinal direction in a concentric manner from the inside in the radial direction on the outer side of the cylindrical reforming vessel. A self-oxidation internal heating type reformer characterized in that a reformed gas de-CO part having a de-CO catalyst layer is arranged in the vertical direction.   The reformed gas guide path and the oxygen mixed gas introduction path for reforming reaction are arranged in parallel in the concentric longitudinal direction inside the reformed gas de-CO section in the radial direction. The reformer according to claim 1, wherein the reformer is characterized in that:   The reformed gas guide passage through the de-CO device and the ascending guide passage to the primary reaction section of the mixed gas of the raw material fuel are sequentially arranged on the outer side in the radial direction of the reformed gas de-CO device in the longitudinal direction concentrically. The reforming apparatus according to claim 1 or 2, wherein the reforming apparatus is provided in parallel, and a descending guide path for the mixed gas of the raw material fuel is formed between the ascending guide path and the inner primary reaction section.   During steady operation, the mixed gas of raw fuel and steam partially reformed by the heat transfer particles and the reforming catalyst, which is maintained at a high temperature by heat transfer of oxidation / reforming reaction and shift reaction, Is mixed with the oxygen mixed gas preheated by the heat at the time of steady operation of the de-CO device arranged in the cylinder, and this is passed through the cylinder equipped with the mixed catalyst of the oxidation catalyst and the reforming catalyst and the shift catalyst in order, and reformed A self-oxidation internal heating reforming method characterized in that a gas is obtained.   The reforming method according to claim 6, wherein the mixed gas of the raw material fuel and water vapor is preheated by heat generated by the de-CO device and transmission of heat transfer particles. The oxidation reaction oxygen and the raw material fuel are initially flowed into the oxidation reaction oxygen introduction passage filled with the oxidation catalyst, and the raw material fuel is oxidized to obtain high-temperature oxygen. This is the primary reaction section during normal operation. Secondary reaction section during normal operation with a mixture of raw material fuel and water vapor that has passed through the heat transfer particle layer and the reforming catalyst layer, which are the regions to become, and a mixed catalyst of shift catalyst and oxidation catalyst in turn A method for starting up an internally heated reforming apparatus, wherein the temperature rise of the reaction section is obtained while obtaining the reformed gas through a region to be

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