JPH05170402A - Fuel reformer - Google Patents

Abstract

PURPOSE:To provide a fuel reformer where the influence of channeling of fuel gas flow on it is eliminated and the quantity of heat due to radiant heat transfer is made uniform for all the reforming tubes so that the surface temp. distribution of the reforming tubes may be made uniform. CONSTITUTION:A lot of reforming tubes 3 are divided into some regions at every tubes 3. Partitions 22 are installed in the boundary of the regions all over the height of the upper half part of the reforming tubes 3. The partition 22 is made of a formed part of heat resisting material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is directed to heating a gas (hereinafter referred to as a raw material gas) obtained by mixing a hydrocarbon gas with water vapor by a combustion gas, and a gas containing hydrogen as a main component (hereinafter referred to as a reformed gas) by a reforming reaction using a catalyst. Fuel reformer (below)
Reformer), in particular, by providing a means for preventing uneven heating phenomenon of a large number of reforming tubes provided in the reformer suitable for use in a fuel cell power plant, The present invention relates to a reformer capable of improving the reliability of a fuel cell power plant.

[0002]

2. Description of the Related Art A fuel cell power plant is a very complicated system, which is generally composed of a fuel cell main body, the reformer, a power converter, a controller and many heat exchangers. Regarding the reformer which is the object of the present invention,
An example of a commonly used reformer is shown in FIGS.

A reforming tube group 4 composed of a large number of reforming tubes 3 regularly arranged on the circumference is erected in a storage container 1 having an inner surface coated with a heat insulating material 2 having an appropriate thickness. A fuel burner 7 (hereinafter referred to as a burner) having a burner air inlet 5 and a burner fuel inlet 6 is provided at the lower end of the storage container 1. In addition, a wide space called a combustion gas space 8 is provided in the upper part of the storage container 1, and a cylindrical riser pipe 9 whose lower end is in contact with the burner 7 is vertically provided in the central part. Further, a raw material gas inlet 10, a reformed gas outlet 11 and an exhaust gas outlet 12 are provided at the lower end of the storage container 1 so as to penetrate the container wall. Moreover, an inner pipe is provided in the reforming pipe 3.
13 is provided, and a granular reforming catalyst is filled between the two tubes to form a catalyst layer 14.

Burner air inlet 5 and burner fuel inlet 6
The burner air and the burner fuel supplied from the burner burn in the burner 7 to become a combustion gas 15 having a high temperature of 1000 ° C. or higher, and rise in the riser pipe 9 installed right above the burner 7 while mixing. Then, the combustion gas 15 whose temperature is made uniform is introduced into the combustion gas space 8 above the storage container 1. Further, the combustion gas 15 turns downward in the combustion gas space 8 and flows into the reforming pipe group 4, and flows through the combustion gas passage 16 formed between the reforming pipes 3 and 3. To do. Next, it flows at high speed through the gap of the heat transfer sleeve 17 provided in the lower half of the reforming pipe 3, flows out to the lower end of the storage container 1, and is discharged from the exhaust gas outlet 12 to the outside of the device.

The temperature of the high temperature combustion gas 15 is gradually lowered by exchanging heat with the fluid flowing inside the reforming pipe 3 when flowing down around the reforming pipe 3. At this time, since the combustion gas 15 is extremely hot in the upper half of the reforming tube 3, radiation is dominant and forced convection is a secondary heat transfer mode. On the other hand, in the lower half, the temperature is relatively low and the flow velocity is accelerated, so forced convection is dominant and radiation is a secondary heat transfer form.

On the other hand, a gas obtained by mixing a hydrocarbon-based raw material gas and water vapor (hereinafter referred to as raw material gas 20) flows into the distribution pipe 18 from the raw material gas inlet 10 at the lower end of the storage container 1 and passes through the distribution branch pipe 19. It is introduced into the reforming pipe 3. Next, the catalyst layer 14 flows upward along the length direction of the reforming pipe 3, and at that time, the raw material gas 20 is heated by the combustion gas 15 flowing outside, and the temperature gradually rises. Then, the reforming reaction occurs due to the action of the catalyst, and changes to the reformed gas 21 containing hydrogen at about 750 ° C. as a main component before reaching the upper end.

Further, the reformed gas 21 is inverted at the upper end of the reforming pipe 3 and flows downward in the inner pipe 13. At this time, the high temperature reformed gas 21 exchanges heat with the relatively low temperature raw material gas 20 through the wall surface of the inner pipe 13, and the temperature drops to about 550 ° C. and is discharged from the reformed gas outlet 11 to the outside of the device. , Is guided to the fuel cell main body via various devices not shown.

[0008]

In the fuel cell power plant having the conventional reformer having the above-mentioned structure and function, the raw material gas is used to cause the reforming reaction.
It is necessary to heat 20 up to about 750 ° C, so that combustion gas 15 is generally a very hot gas from 1000 ° C to 1500 ° C.

Therefore, the temperature of the reforming tube 3 is about 1000 ° C. at the upper end, which is extremely harsh for a metallic material. Then, in order to sufficiently bring out the reforming performance and to secure the function, all of the many reforming tubes 3 are uniformly heated, and variations in the surface temperature thereof are particularly affected.
It is essential to have a minimum at the top of the. If the continuous operation is performed under the condition that the average temperature is about 1000 ° C. and the local overheat is generated, the metal life of the reforming pipe 3 is drastically reduced, and in an extreme case, it may be broken in a short time.

On the contrary, when the average temperature of the reforming pipe 3 is lowered to prevent local overheating, it becomes impossible to heat the temperature of the raw material gas 20 to about 750 ° C. Inevitably, the deterioration of the reforming performance, which is the most important point to avoid, is inevitable.

As described above, in the reformer in which a large number of reforming tubes 3 are arranged to constitute the reforming tube group 4, it is important to make the temperature distribution of the metal portion of the reforming tube 3 uniform. Particularly, recently, since this type of reformer tends to be large-sized and the number of reforming tubes 3 tends to increase, this problem is the most important issue.

By the way, the cause of the variation in the temperature of the reforming tube 3 is often mainly related to the flow of the combustion gas 15. That is, in the case where the flow of the combustion gas 15 as a heat source is not uniform around a large number of reforming tubes 3 and a flow along the length direction of the reforming tubes 3 and a transverse flow perpendicular to the length direction coexist. is there.

4 to 6, as an example, a reforming tube group 4
The case where a drift of the combustion gas 15 occurs inside is schematically shown. As shown in the figure, there is a region where the combustion gas flowing into the combustion gas passage 16 flows straight down along the lengthwise direction of the reforming pipe 3, and there is a region where the combustion gas passes around a certain reforming pipe 3 and changes in temperature. There is also a cross flow region where the lowered combustion gas flows into the adjacent reforming pipe 3.

As described above, in the heat transfer form in the upper half of the reforming tube 3, the amount of heat transfer by forced convection is relatively small,
Radiation is dominant. Since the radiant heat transfer is proportional to the fourth power of the gas temperature, the heat transfer amount of a certain reforming tube 3 is determined by the temperature of the combustion gas 15 existing around it. Then, if the combustion gas 15 has a nonuniform flow in the reforming tube group 4 and the temperature around the individual reforming tubes 3 becomes nonuniform, the temperature of the reforming tubes 3 also becomes nonuniform.

As described above, the cause of the local overheating of the reforming tube 3 is due to the nonuniform flow of the flow of the combustion gas 15, the nonuniformity of the gas temperature caused by it, and the variation of the radiant heat transfer accompanying it. It is not a problem that can be easily solved by changing the shape of the arrangement of the pipe 3 or the like.

The pressure loss of the combustion gas 15 is the largest in the heat transfer sleeve 17, and the amount of the combustion gas 15 flowing into the heat transfer sleeve 17 because the flow is restricted by the portion is the total number of the reforming tubes 3. Is almost constant.

The present invention has been made to solve the above problems, and an object of the present invention is to eliminate the influence of drift of the flow of combustion gas and to reduce the amount of heat by radiant heat transfer to all reforming tubes. The object is to provide a fuel reformer in which the surface temperature distribution of the reforming tube is made uniform by the above.

[0018]

In order to achieve the above object, the present invention has a reforming tube group composed of a large number of reforming tubes inside a storage container, and obtains combustion gas by a combustion burner. Further, in the fuel reformer that heats the raw material gas flowing in the reforming pipe by sending it to the combustion gas passage outside the reforming pipe through the combustion gas space, combustion in the combustion gas passage along the upper half of the reforming pipe. A partition wall is provided to prevent gas from flowing in the radial direction and the circumferential direction.

[0019]

By the above means, the drift of the combustion gas in the reforming tube group is eliminated, and therefore the temperature distribution of the combustion gas becomes constant around all the reforming tubes, so that the surface temperature distribution of the reforming tubes becomes Be homogenized.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a vertical sectional view of a reformer to which the present invention is applied, and FIG. 2 shows a lateral sectional view thereof. FIG. 3 shows details around the reforming tube 3 of the present invention. In each of the drawings, the parts denoted by the same reference numerals as those in FIGS.

In the reforming pipe group 4 below the combustion gas space 8, a large number of reforming pipes 3 are divided into several regions for some reforming pipes 3, and partition walls 22 are provided at the boundaries of the regions. Is installed. The height of the partition wall 22 extends over the entire height of the upper half portion of the reforming tube 3, and the lower end portion is held by the heat insulating material provided around the heat transfer sleeve 17 in the lower half portion of the reforming tube 3. .. Also,
The material of the partition wall 22 is made of a heat-resistant material, for example, a molded product of a ceramic heat insulating material whose main component is aluminum oxide (Al ₂ O ₃ ). Next, the operation of the embodiment of the present invention will be described along the flow of gas. The description of the parts having the same functions as the conventional ones will be omitted.

The burner fuel and the burner air are burned in the burner 7 to become a combustion gas 15 having a high temperature of 1000 ° C. or higher, and flows into the combustion gas space 8 via the riser pipe 9. Therefore, the combustion gas 15 is inverted and flows into the reforming tube group 4, and the combustion gas passage 16 formed in the gap between the reforming tube 3 and the upper half of the reforming tube 3 is radiated to the reforming tube by radiative heat transfer. Heat is supplied to 3 and the temperature is lowered to flow down.

At this time, since the upper half portion of the reforming pipe 3 is partitioned by the partition wall 22 and is independent for each region, the combustion gas 15 flowing into one region is almost vertical to the lower end of the partition wall 22. The drift along the reforming pipe 3 and the flow across the reforming pipe 3 does not occur. Next, the combustion gas 15 flows into the gap between the heat transfer sleeve 17 in the lower half of the reforming pipe 3 and the reforming pipe 3 to increase its flow velocity, and further flows down while lowering the temperature.

At this time, the amount of the combustion gas 15 flowing into each region partitioned by the partition wall 22 corresponds to the ratio of the number of the reforming tubes 3 included in that region. This is because the pressure loss of the combustion gas 15 in the combustion gas space 8 and the combustion gas passage 16 passes through the heat transfer sleeve 17 in the lower half of the reforming pipe 3 as described in the section of the prior art. It is due to being very small compared to. That is, as a fluid dynamic characteristic, the flow rate of the combustion gas 15 flowing through the heat transfer sleeve 17 having the largest pressure loss is substantially equal in all the reforming tubes 3.

Therefore, the flow rate of the combustion gas 15 flowing around the reforming tubes 3 and the temperature distribution in the height direction are substantially equal in all the reforming tubes 3, and therefore the temperature distribution in the reforming tubes 3 is not uniform. There is no need to worry about local overheating.

According to the present invention, in addition to the reformer having the reforming tube group 4 having the arrangement shown in the embodiment, appropriate region division can be made to the reformer having the reforming tube group 4 having various arrangements. It goes without saying that it can be applied by applying.

[0027]

As described above, according to the present invention,
Since the partition wall is provided in the upper half of the reforming tube, there is no concern that uneven flow or cross flow of the combustion gas will occur. Therefore, the temperature distribution in the reforming tube can be made uniform and local overheating can be prevented. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing an embodiment of a fuel reformer according to the present invention.

FIG. 2 is a cross-sectional view of a fuel reformer according to the present invention.

FIG. 3 is a detailed view around the reforming tube of the present invention.

FIG. 4 is a vertical sectional view showing an example of a conventional fuel reformer.

FIG. 5 is a cross-sectional view showing an example of a conventional fuel reformer.

FIG. 6 is a detailed view around a conventional reforming tube.

[Explanation of symbols]

 1 ... Storage container 3 ... Reforming tube 4 ... Reforming tube group 7 ... Combustion burner 8 ... Combustion gas space 16 ... Combustion gas passage 22 ... Partition

Claims (1)

[Claims] 1. A reforming tube group composed of a large number of reforming tubes is provided inside a storage container, combustion gas is obtained by a combustion burner, and combustion is performed outside the reforming tube through a combustion gas space. In the fuel reformer that sends the gas to the gas passage and heats the raw material gas flowing in the reforming pipe, the combustion gas is prevented from flowing in the combustion gas passage along the upper half of the reforming pipe in the radial direction and the circumferential direction. A fuel reformer having a partition wall for preventing the fuel reformer.