JPH035301A - Method for operating and stopping fuel reformer - Google Patents

Abstract

PURPOSE:To reduce the time required for the reducing reaction of an oxidation catalyst by introducing an inert gas into a reformer tube isolated from the raw material in the backward direction to purge a combustible gas contg. steam. CONSTITUTION:Selectors 32, 35 and 36 are closed, and selectors 13, 33 and 24 are opened to operate the fuel reformer. Meanwhile, when the operation is stopped, the selector 13 is closed to stop the supply of the raw gas such as hydrocarbons and alcohols, a burner 3 is extinguished, a feed valve 24 is closed to stop the supply of the reformed gas 21 to a fuel cell. The selectors 35 and 36 are then opened, the selector 33 is closed, the selector 32 is opened to introduce the inert gas 31 from the lower outlet of the reformer 2 through the selector 32, the remaining reformed gas and steam are discharged to the outside of the system from the selector 36 through an inert gas passage 34, a water condenser 22 and a steam separator 23 as a vent gas 37, and condensed water is recovered in the separator 23.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to the use of low-purity inert gas when stopping the reforming operation of a fuel reformer that supplies hydrogen-rich reformed gas to a fuel cell. This invention relates to a method for purging reformed gas and water vapor remaining in a reformer using the present invention.

[Conventional technology]

FIG. 2 is a system flow diagram showing a conventional device. In FIG. provided. The raw material 11 is a mixture in which hydrocarbons such as methane or alcohols such as methanol are used as raw fuel, and steam or water necessary for a steam reforming reaction is added thereto at a predetermined hydrogenation ratio. The raw material gas is heated to a predetermined temperature by the provided heater 12, and is supplied to the upper inlet side of the reforming reaction tube 2 via the switching valve 13. The reforming reaction tube 2 is filled with a layer of a copper-based, zinc-based, molybdenum-based, etc. reforming catalyst as a steam reforming catalyst 2C, and the raw material gas is reformed into a hydrogen-rich reformed gas by a steam reforming reaction. This steam reforming reaction is an endothermic reaction, and the amount of heat required is
It is supplied by burning F, and reforming is carried out by keeping the reforming reaction tube 2 at a temperature suitable for the reaction.
The combustion exhaust gas 5 undergoes heat exchange with a heater 12, for example, and then is discharged to the outside of the system. The generated reformed gas 21F condenses water contained in a large amount in the reformed gas in the bottom analyzer 22 of the reforming reaction tube 2, recovers water in the steam-water separator 23, and converts the reformed gas 21F into a dried reformed gas 2.
1 is supplied to a fuel cell power generation device (not shown) via a switching valve 24.

In this way, when stopping the equipment during reforming operation, the valve 13
．． 24 is closed and the valve 36 on the vent side is opened, the reformed gas 21 with a pressure higher than atmospheric pressure is released outside the system as Ghent gas 37.
A large amount of normal-pressure reformed gas 21F and water vapor remain in the chamber. In this state, when the burner 3 is extinguished and the temperature of the furnace body 4 decreases, air is sucked in from the vent side because the gas pressure in the system decreases, and the hydrogen-rich reformed gas and air are mixed. There is a risk of explosion. Moreover, the water vapor in the system condenses on the cooled surface of the reforming catalyst layer 20. If the reforming catalyst layer in such a wet state is left as it is and the operation of restarting and stopping is repeated, the reforming catalyst will be powdered and the catalyst performance will deteriorate.

In order to prevent this situation, the switching valves 13 and 2
4, open the valve 36, and open the inert gas supply system 3.
0 switching valve 32 is opened and an inert gas 31 such as nitrogen gas is supplied to the reforming reaction tube 2 from the upper inlet side of the reforming reaction tube 2 via a part of the raw material supply system 10, and the reforming reaction tube 2 and the reformed gas are There is a known shutdown method in which the reformed gas 21F and water vapor remaining in the supply system 20, etc. are expelled to the vent side (this operation is called purge), and then the system is brought to a resting state with the system filled with inert gas. . In addition, by using nitrogen separated from the air by a nitrogen separation device using zeolite or a nitrogen separation device using a permeable membrane as the inert gas 31, it is possible to install a nitrogen tank or a liquefied nitrogen tank or replenish pure nitrogen. A method is known to eliminate the need for

[Problem to be solved by the invention]

The nitrogen gas obtained by the above-mentioned nitrogen content jiI apparatus generally contains about 0.1% to 2% oxygen, mainly from the economical point of view of the apparatus. When low-purity nitrogen gas containing oxygen is supplied to the reforming reaction tube as the inert gas 31 in this way, the reforming catalyst 2C is oxidized and its function as a catalyst is degraded. In the conventional device, the inert gas 31 is sent from the upper inlet side of the reforming reaction tube 2 (the inlet side of the raw material gas) to purge the flammable gas, so the reforming catalyst layer 2C
The oxidative deterioration starts from the inlet side and progresses sequentially towards the outlet side. The oxidatively degraded catalyst is reduced by the hydrogen produced by restarting the reforming operation, but since the main part of the oxidatively degraded part exists on the feedstock side of the raw material gas, the rate of reduction by the produced hydrogen is slow, and the fuel, which is a load, is reduced. If the battery is a power generating device that frequently starts and stops repeatedly, there is a drawback that oxidative deterioration of the reforming catalyst progresses gradually. As a countermeasure to this problem, it is possible to predict the oxidative deterioration and to provide a margin in advance for the amount of reforming catalyst to be filled in the reforming reaction tube 2. However, this will avoid the problem of increasing the size of the reforming reaction tube. arise.

An object of the present invention is to activate the reduction reaction of the oxidized catalyst so that repeated startup and shutdown can be performed using low-purity nitrogen gas as an inert gas.

[Means to solve the problem]

In order to solve the above-mentioned problems, according to the present invention, raw materials such as hydrocarbons and alcohols are sent to a reforming reaction tube of a water cool air reformer having a heat source through the supply system to produce a hydrogen-rich reformer. In a fuel reformer that reformes the raw material into a reformed gas and supplies the raw material to a fuel cell via a reformed gas supply system, after cutting off the supply of the raw material when the fuel reformer is stopped, inert gas is supplied to the reforming reaction tube. The reforming reaction tube and the reformed gas supply system are introduced in a direction opposite to the supply direction of the reformed gas to purge the combustible gas containing water vapor and gas remaining in the reforming reaction tube and the reformed gas supply system.

[Effect]

In the above method, we focused on the fact that the reduction reaction of the oxidized reforming catalyst can be activated in an atmosphere with a high hydrogen concentration. By supplying the reformed gas from the outlet side, oxidative deterioration of the reforming catalyst layer mainly occurs at the outlet side of the reformed gas. Therefore, by restarting the reforming operation, the upstream side Hydrogen produced by 7
Since the oxidized reforming gas is abundantly supplied to the downstream oxidized reforming catalyst portion, the reduction reaction of the oxidation catalyst becomes active, and the performance of the reforming catalyst can be restored in a short reforming operation.

Therefore, even if low-purity nitrogen gas is used to purge flammable gas and steam when reforming operation is stopped,
Since the reduction in the reforming reaction can be recovered in a short time by restarting the reforming operation, the fuel reformer can be repeatedly started and stopped in response to the fuel cell load.

〔Example〕

The present invention will be explained below based on examples.

FIG. 1 is a system flow diagram of a fuel reformer showing an embodiment method of the present invention. In FIG. 10 and the upstream side of the water condenser 22 of the reformed gas supply system 20, an inert gas passage 34 having a switching valve 35 is provided.

Further, the inert gas supply system 30 is connected to the reformed gas supply system 20 via a switching valve 32 so as to communicate with the lower outlet side of the reforming reaction tube 2.
connected to. In addition, this connecting part and the inert gas passage 3
A switching valve 33 is provided in the piping portion of the reformed gas supply system 20 between the connecting portion of the reformed gas supply system 20 and the connecting portion of the reformed gas supply system 20 .

The reforming operation of the reformer configured in this way is carried out by the switching valve 32.
．． 35 and 36 are closed and the switching valves 13, 33, 24 are open as in the conventional method.

On the other hand, when the reforming operation is stopped, the switching valve 13 is closed to cut off the supply of the raw material, the burner 3 is extinguished, and the supply valve 24 is closed to stop the supply of the reformed gas 21 to the fuel cell (not shown). Then, the switching valves 35 and 36 are opened.

When the switching valve 33 is closed and then the switching valve 32 is opened, nitrogen gas 31 containing oxygen as an inert gas flows from the lower outlet of the reforming reaction tube 2 through the switching valve 32, and the remaining reformed gas and water vapor are is an inert gas passage 34 from the upper inlet/outlet of the reforming reaction tube 2. Water condenser 22. It is purged out of the system as pent gas 37 from a valve 36 via a steam/water separator 23. In addition, the water vapor is transferred to the water condenser 22.
aI#IL is collected in the steam separator 23. The supply of nitrogen gas is cut off by the switching valve 32 when the hydrogen concentration in the system becomes sufficiently low, and by closing the valve 36, the system is cooled with nitrogen gas 31 sealed in the system, and the system is put into a rest state. reach.

During the above-mentioned stop operation, the oxygen content in the nitrogen gas flowing from the outlet side of the reforming reaction tube 2 reacts with the reforming catalyst, and if the catalyst is copper-based, for example, 1 qcuo of suboxide is generated on the catalyst surface, and the reforming Oxidation of the catalyst progresses from the lower outlet portion to the inlet portion of the quality catalyst 12c. However, when the reforming operation of the reformer is restarted, the hydrogen-rich reformed gas 21F generated on the upstream side of the reforming catalyst layer 2C is abundantly supplied to the oxidized catalyst located on the downstream side, as shown in the following equation. The reduction reaction is actively carried out, and the oxidized catalyst is quickly reduced and can regain its activity as a reforming catalyst.

CuO+H1→Cu+H1O-・-111 In this way, in the example method, the adsorbent method can be achieved by simply adding an inert gas passage through which the inert gas flows in the opposite direction to the raw material gas in the reforming reaction tube of the fuel reformer. Starting reforming operation by using low-purity nitrogen containing about 0.1% to 2% oxygen, obtained with a simple air nitrogen separation device such as a permeation membrane method, as an inert gas for purging the remaining reformed gas. Even if the stop is repeatedly performed, the reforming reaction can be carried out efficiently without deteriorating the steam reforming reaction due to oxidation of the reforming catalyst layer. In addition, since flammable gas in the system can be completely purged and water can be recovered, it goes without saying that performance degradation due to wet reforming catalyst layers and the risk of mixture of air and flammable gas can be avoided. That's true.

〔Effect of the invention〕

As mentioned above, when stopping the reforming operation of the fuel reformer, this invention sends low-purity nitrogen gas containing oxygen into the reforming reaction tube in the opposite direction to the supply direction of the raw material gas. It was configured to purge flammable gas including residual water vapor.

As a result, the reforming catalyst is oxidized by the oxygen in the nitrogen gas at the outlet side of the reforming reaction tube, and when the reforming operation is resumed, the oxidized catalyst is abundantly supplied with the hydrogen gas generated upstream, and the oxidation catalyst Because the reduction reaction occurs actively, the time required for the reduction reaction can be significantly shortened compared to the conventional method of flowing inert gas in the same direction as the raw material gas. It is possible to obtain a fuel reformer that can repeatedly start and stop in response to the fuel cell load without causing a drop in reforming performance by using low-purity nitrogen gas supplied from a fraudulent air nitrogen separation device. can. In addition, there is no need to increase the amount of reforming catalyst due to oxidative deterioration, high purity nitrogen is not required, and a backflow passage for inert gas can be easily formed, making the reformer smaller and simpler. This has the advantage of saving labor in maintenance work such as replenishing pure nitrogen.

[Brief explanation of drawings]

FIG. 1 is a system flow diagram of a fuel reformer showing an embodiment of the present invention, and FIG. 2 is a system flow diagram of a fuel reformer showing a conventional method. 1: Fuel reformer, 2: Reforming reaction tube, 3: Harna, 4: Furnace body, 10: Raw material supply system, 11: Hydrogenation raw material, 12: Heater, 20: Reformed gas supply system, 21. 21F: Reformed gas,
22: Water condenser, 23: Steam/water separator, 30: Inert gas supply system, 31: Inert gas (low purity nitrogen gas), 13.24, 32.33.35, 36: Switching valve, 34: Inert gas passage, 37: Vent system (gas to be purged).

Claims (1)

[Claims] 1) Raw materials such as hydrocarbons and alcohols are sent through the supply system to the reforming reaction tube of a steam reformer that has a heat source, reformed into hydrogen-rich reformed gas, and the reformed gas supply system is In a fuel reformer that supplies fuel to a fuel cell through a fuel reformer, after cutting off the supply of the raw material when the fuel reformer is stopped, an inert gas is introduced into the reforming reaction tube in the opposite direction to the supply direction of the raw material to 1. A method for stopping operation of a fuel reformer, comprising purging flammable gas containing water vapor remaining in a reformed reaction tube and a reformed gas supply system.