JPH0761842B2 - Fuel reformer for fuel cell power generation system - Google Patents

Description

The present invention relates to a heating medium that is incorporated in a fuel cell power generation system and heats a reforming raw material when generating a hydrogen-rich reformed gas to be supplied to a fuel cell. The present invention relates to a fuel reformer equipped with a burner for supplying fuel by combustion.

[Conventional technology]

A fuel cell power generation system is configured by incorporating a fuel cell and a fuel reformer, and the fuel reformer produces a reformed gas by reforming a hydrogen-rich gas from a reforming raw material, and the reformed gas is generated. Is supplied to the fuel cell as fuel. The fuel cell generates electricity by a cell reaction between the supplied reformed gas and air as an oxidant gas. At this time, the fuel gas containing hydrogen that does not contribute to the cell reaction is discharged from the fuel cell. This exhaust fuel gas is guided to the fuel reformer and burned by the supplied combustion air, and the flame and combustion gas generated by combustion heat the reforming tube filled with the reforming catalyst and flow through the reforming tube. The reforming raw material is reformed into a hydrogen-rich gas. The amount of reformed gas generated and the amount of exhausted fuel gas discharged increase or decrease according to the load amount of the fuel cell.

As such a fuel reformer, the one shown in FIG. 3 is conventionally known. In the figure, the reforming pipe 2 has a double pipe structure, and is constituted by connecting an inner pipe 4 and an outer pipe 5 provided inside and outside the partition cylinder 3 at a lower end portion thereof with a semi-annular bottom plate 6. The partition cylinder 3 is provided apart from the bottom plate 6. The reforming pipe 2 is divided into an upper half portion and a lower half portion, and the lower half portion is filled with the reforming catalyst 7, and is provided between the inner pipe 4 and the partition cylinder 3 and between the partition cylinder 3 and the outer pipe 5. Form an inner catalyst layer 8 and an outer catalyst layer 9, respectively, and the inner catalyst layer 8 and the outer catalyst layer 9 are connected at their lower ends to form a catalyst layer 11. Reforming tube 2
Between the outer tube 5 and the partition cylinder 3 in the upper half part of the reforming material, an inlet chamber 12 through which the reforming raw material flows into the catalyst layer 11 and between the partition cylinder 3 and the inner tube 4 flows out from the catalyst layer 11 A gas outlet chamber 13 is formed.

The furnace container 15 is provided so as to surround the lower half of the reforming tube 2.
The burner 16 is provided at the center of the upper portion of the furnace vessel 15, and is provided with an exhaust fuel gas supply passage 18 having a nozzle 17 for ejecting exhaust fuel gas, and a combustion air supply passage 20 having a nozzle 19 for ejecting combustion air. ing.

The inner portion of the inner pipe 4 of the reforming pipe 2 is the combustion chamber 22, and the reforming pipe 2
A heating chamber 23 is formed between the heating chamber 23 and the furnace container 15, and a combustion exhaust gas outlet is provided at an upper portion of the heating chamber 23.

With such a configuration, the exhaust fuel gas containing the amount of residual hydrogen corresponding to the load amount of the fuel cell discharged from the fuel cell is passed through the fuel supply passage 18 and the nozzle 17, while the combustion air is passed through the combustion air supply passage 20. Ejected from the nozzle 19, the exhausted fuel gas is mixed with combustion air and burned, a flame and combustion gas are formed in the combustion chamber 22, the combustion gas flows from the combustion chamber 22 to the heating chamber 23, and from the upper combustion exhaust gas outlet. It is discharged to the outside.

On the other hand, an amount of reforming raw material corresponding to the load of the fuel cell, such as natural gas or naphtha, flows into the inlet chamber 12 together with the steam and then into the catalyst layer 11, and passes through the outer catalyst layer 9 and the inner catalyst layer 8. Shed. During this time, the reforming raw material that is heated by the flame or combustion gas due to combustion in the burner 16 and flows through the catalyst layer 11 is reformed into a hydrogen-rich gas, and this reformed gas flows from the catalyst layer 11 into the outlet chamber 13. After that, it is supplied to the fuel cell.

By the way, the combustion air amount for burning the exhaust fuel gas in the burner 16 is determined from the exhaust fuel gas amount, and the air-fuel ratio 1.05 to 2.5 so that the representative temperature of the catalyst layer 11 or the reforming pipe surface temperature becomes an appropriate temperature. To control the temperature of the catalyst layer.

The reforming tube surface temperature when the exhaust fuel gas is burned by the burner 16 to heat the reforming tube 2 with the air-fuel ratio as described above has the temperature distribution shown in FIG. In Fig. 4, the horizontal axis represents the catalyst layer position in the flow direction of the reforming raw material, and the vertical axis represents the reforming pipe surface temperature. 25 is a high load in which a large amount of reforming raw material flows into the fuel reformer. At this time, 26 is the temperature distribution of the reforming tube surface temperature at the catalyst layer position in the flow direction of the reforming raw material due to the combustion of the exhaust fuel gas under a low load in which a small amount of the reforming raw material flows. From the figure, it is understood that the temperature distribution 26 at low load has a higher temperature on the catalyst layer outlet side on the combustion chamber side than the temperature distribution 25 at high load.
This is because when the load is low, the endothermic amount of the endothermic reaction in the catalyst layer is small, and therefore the heat transfer area is larger than the heat transfer amount, and therefore the reforming tube surface temperature near the catalyst layer outlet portion rises.

By the way, the reforming tube 2 is made of super heat resistant steel such as HK-40 and Inconel 800, but even with these materials, the service life is remarkably reduced at a temperature of 900 ° C. or higher. Therefore, the reforming pipe surface temperature is controlled to be lowered by lowering the combustion temperature by increasing the air-fuel ratio.

On the other hand, when the load is large, the endothermic amount of the endothermic reaction in the catalyst layer also becomes large. Therefore, it is necessary to increase the heat transfer area. However, the heat transfer area is designed to be as small as possible in order to make the fuel reformer compact in consideration of the fact that it is for on-site use. For this reason, it is necessary to raise the combustion temperature in order to secure the amount of heat transfer. Therefore, the air-fuel ratio is made small so that the combustion temperature becomes high.

[Problems to be Solved by the Invention]

As described above, it is important to change the air-fuel ratio in order to control the reforming surface temperature and combustion temperature of the fuel reformer according to the load of the fuel cell and the fuel reformer. There is a problem that it has an adverse effect. When the load changes, especially when the load changes from high to low, the exhaust gas from the fuel cell increases and the reforming pipe near the catalyst layer outlet is temporarily overheated, causing the reforming pipe surface temperature to rise temporarily. There is also a problem that the temperature becomes high and the life of the modified pipe material is shortened.

The object of the present invention is to stabilize the combustibility in the burner by keeping the air-fuel ratio constant from a low load to a high load of the fuel cell and the fuel reformer, and also to temporarily improve the surface temperature of the reforming pipe even when the load changes. It is to provide a fuel reformer for a fuel cell power generation system that can prevent a significant increase.

[Means for Solving the Problems]

According to the present invention, in order to solve the above-mentioned problems, according to the present invention, a reforming pipe annularly arranged in a furnace chamber and filled with a reforming catalyst, and a discharge pipe disposed in the upper center of the furnace chamber and discharged from a fuel cell are provided. A fuel cell that includes a burner that burns fuel gas, heats the reforming tube with a heat medium from the burner, reforms the reforming raw material that flows through the reforming tube into a gas rich in hydrogen, and supplies the gas to the fuel cell. In a fuel reformer of a power generation system, the burner is provided with an exhausted fuel gas supply passage having a fuel injection port that is provided in a central portion and opens into a furnace chamber, and a primary air jet that is opened in the furnace chamber in a region around the fuel injection port. A primary air supply passage having an outlet, a secondary air supply passage having a secondary air jet opening to the furnace chamber in the peripheral area of the primary air jet outlet, and a secondary air supply passage having an opening to the furnace chamber in the peripheral area of the secondary air jet outlet. ,
The cooling air supply passage has an ejection port for ejecting cooling air for cooling the reforming pipe.

[Action]

In a gas burner, the mixed state of fuel and combustion air is generally the largest factor that determines the combustion speed that governs the combustion state. Therefore, by changing the primary air amount and the secondary air amount with respect to the exhaust fuel gas amount that changes with the load of the fuel cell, the shape of the flame generated during combustion of the exhaust fuel gas is changed and its temperature distribution is controlled. Then, the amount of heat received by the reforming tube is controlled and the surface temperature of the reforming tube is appropriately controlled, so that the air-fuel ratio can be kept constant. Further, when the load of the fuel cell fluctuates, particularly when the load fluctuates from low load to high load, the reforming pipe is temporarily overheated due to the increased amount of exhausted fuel gas. Controls temperature rise.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a sectional view of a fuel reformer according to an embodiment of the present invention. In FIG. 1, the same parts as those of the conventional example of FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. 1 is different from the conventional example in that a primary air supply passage 31 having a primary air nozzle 30 opening to a combustion chamber 22 around a nozzle 17 of an exhaust fuel gas supply passage 18 arranged in a central portion and a primary air supply passage A secondary air nozzle that opens into the combustion chamber 22 in the lower peripheral area of the nozzle 30.
A secondary air supply passage 33 having 32, and a cooling air supply passage 35 having a cooling air nozzle 34 opening to the combustion chamber 22 in the peripheral area of the secondary air nozzle 32 and ejecting cooling air for cooling the reforming pipe 2.
And is equipped with.

With such a configuration, the amount of exhausted fuel gas increases or decreases according to the load amount of the fuel cell, but the amount of combustion air composed of primary air and secondary air stably burns the amount of exhausted fuel gas corresponding to the load amount. Is supplied to the burner 16 with a constant air-fuel ratio, primary air is ejected from the primary air nozzle 30 via the primary air supply passage 31, and secondary air is ejected from the secondary air nozzle 32 via the secondary air supply passage 33. Then, it is mixed with the exhaust fuel gas ejected from the nozzle 17 through the fuel supply passage 18 and burned.

In the above combustion, when the load on the fuel cell and the fuel reformer is small, the amount of secondary air is increased and the amount of primary air is decreased. As a result, the fuel that could not be burned due to the small amount of primary air comes into contact with the secondary air and burns, so that the length of the flame becomes relatively long. As a result, the heat of combustion in the vicinity of the catalyst layer outlet is relatively small. As a result, overheating of the reforming pipe near the catalyst layer outlet portion is prevented, and an increase in the surface temperature of the reforming pipe is suppressed. Conventionally, when the load is small, the air-fuel ratio was increased to prevent overheating of the reforming pipe, but in the present invention,
It is possible to suppress overheating near the catalyst layer outlet portion of the reforming pipe without changing the air-fuel ratio (that is, even if the air-fuel ratio is smaller than in the past). When the load is large, the amount of secondary air is reduced, the amount of primary air is increased to shorten the flame length, and the temperature near the outlet of the catalyst layer, that is, the surface temperature of the reforming pipe near the outlet of the catalyst layer is reduced. Keep the temperature appropriate for the reforming reaction.

FIG. 2 shows reforming when the exhaust fuel gas is burned by mixing and adjusting the primary air amount and the secondary air amount as described above for the low load and the high load of the fuel reformer in the burner 16 as described above. 4 is a graph showing the temperature distribution of the reforming tube surface temperature at the position of the catalyst layer in the flow direction of the raw material in the same manner as in FIG. 4, where 27 shows the temperature distribution when the load is high, and 28 shows the temperature distribution when the load is low. Of FIG.
25 and 27 in FIG. 2 have almost the same temperature distribution curve, and there is a big difference between the temperature distribution curves 26 and 28 when the load is low.
From the figure, the temperature of the reforming tube near the outlet of the catalyst layer does not rise to a high temperature as in the past even when the fuel reformer has a low load, and the temperature distribution at low load is almost the same as that at high load. It is understood that it is controlled so that

When the load of the fuel cell changes from a low load to a high load, the amount of exhaust fuel gas increases and the reforming pipe is temporarily overheated, but the cooling air is temporarily cooled through the cooling air supply passage 35. The reforming pipe 2 is directly cooled by jetting from the air jet port 34, and the rise of the reforming pipe surface temperature is prevented.

〔The invention's effect〕

As is clear from the above description, according to the present invention, the burner of the fuel reformer is provided with the primary air supply passage, the secondary air supply passage, and the cooling air supply passage. Controlling the temperature distribution of the flame from low load to high load by controlling the amount of primary air and secondary air to prevent the surface temperature of the reforming tube near the catalyst layer outlet from rising and to give the catalyst layer the necessary amount of heat. Since the air-fuel ratio can be made constant, the combustibility can be stabilized. Also, when the reforming pipe is temporarily overheated due to an increase in the amount of exhausted fuel gas when the fuel cell changes from low load to high load, the reforming pipe can be cooled by the cooling air, so the surface temperature of the reforming pipe rises. Can be prevented.

[Brief description of drawings]

FIG. 1 is a sectional view of a fuel reformer according to an embodiment of the present invention,
FIG. 2 is a diagram showing the temperature distribution of the reforming tube surface temperature with respect to the position of the catalyst layer in the flow direction of the reforming raw material when the exhaust fuel gas from the fuel cell is burned by the burner of FIG. 1, and FIG. FIG. 4 is a sectional view of the fuel reformer of FIG. 4, and FIG. 4 shows the temperature distribution of the reforming tube surface temperature with respect to the catalyst layer position in the flow direction of the reforming raw material when the exhaust fuel gas of the fuel cell is burned by the burner of FIG. FIG. 2: reforming pipe, 7: reforming catalyst, 11: catalyst layer, 18: exhaust fuel gas supply passage, 22: combustion chamber, 23: heating chamber, 31: primary air supply passage, 33: secondary air supply passage, 35: Cooling air supply path.

Claims (1)

[Claims] 1. A reforming tube which is annularly arranged in a furnace chamber and is filled with a reforming catalyst, and a burner which is provided at the center of an upper portion of the furnace chamber and burns exhaust fuel gas discharged from a fuel cell. In a fuel reformer of a fuel cell power generation system, which heats a reforming tube with a heat medium from a burner, reforms a reforming raw material flowing through the reforming tube into a gas rich in hydrogen, and supplies the reformed gas to a fuel cell,
The burner, an exhaust fuel gas supply path having a fuel injection port that is provided in the central portion and opens into the furnace chamber, and a primary air supply path that has a primary air ejection port that opens into the furnace chamber in the peripheral region of the fuel injection port, A secondary air supply passage having a secondary air jet opening to the furnace chamber in the area around the primary air jet, and cooling air opening to the furnace chamber in the area around the secondary air jet to cool the reforming pipe. A fuel reformer for a fuel cell power generation system, comprising: a cooling air supply passage having an ejection port for ejecting the fuel.