JPS61250409A - Apparatus for catalytic combustion - Google Patents

Abstract

PURPOSE:To surely prevent a backfire and to make possible a stable catalytic combustion, by providing porous solid substances of high porosity and permeability on the introducing side of mixed gases. CONSTITUTION:Combustible gases 2 are introduced into a gas mixer 1 together with air or exhaust air 3 whose oxygen concentration is lower than that of the ordinary air. A gas mixture of the combustible gases 2, having being mixed in the gas mixer 1, and air or the exhaust air 3 are passed through permeable, porous solid substances 6 of extremely high porosity, causing almost no pressure drop, and then introduced into a catalytic combustion chamber 4. In the catalytic combustion chamber 4 the combustible gases 2 burn with air or the exhaust air 3 in the presence of combustion catalysts 41 and forwarded to gas users as high-temperature combustion gases. Backfires being thus prevented, and being also capable of a low-load operation, a stable catalytic combustion can be carried out together with low energy loss.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a catalytic combustion device for burning flammable gas in the presence of a combustion catalyst using air or air having a lower oxygen concentration than normal air.

[Technical Background of the Invention and Problems thereof] In recent years, development of fuel cell power generation systems has been actively promoted as systems that directly convert chemical energy contained in fuel into electrical energy. This fuel cell power generation system usually arranges a pair of porous electric bridges with an electrolyte in between, and contacts a fuel gas such as hydrogen on the back of one electrode, and an oxidizing agent such as air on the back of the other electrode. Electrical energy is extracted from between the electrodes by bringing gas into contact and utilizing the electrochemical reaction that occurs.As long as the fuel gas and oxidant gas are supplied, electrical energy can be extracted with high conversion efficiency. It is something that can be taken out.

On the other hand, in this type of fuel cell power generation system, as a method to increase the overall efficiency of the system, air with a low oxygen concentration that is exhausted after being used for the electrochemical reaction in the fuel cell is used as the fuel for the fuel cell. It has been proposed to use the air as a heating source for the reforming reaction in a reformer for producing hydrogen (Japanese Patent Laid-Open No. 57-3678).
Publication No. 4).

In addition, NOx emission regulations have become stricter due to environmental conservation issues, and it is necessary to reduce Nox in the combustion exhaust gas from the reformer even in such fuel cell power generation systems. Therefore, recently, a technology has been put into practical use that employs a catalytic combustion method, which generates less Nox than a burner combustion method, as a heating method in a reformer. That is, this catalytic combustion method mixes exhaust air discharged from one electrode of a fuel cell and exhaust fuel discharged from the other electrode,
This is combusted in the presence of a combustion catalyst.

By the way, when performing catalytic combustion using this type of catalytic combustion method, conventionally, exhaust air and exhaust fuel are mixed in advance in a mixer, and this mixed gas is introduced into a combustion catalyst chamber filled with a combustion catalyst. The apparatus is configured to combust the exhaust fuel in the presence of a combustion catalyst. In this case, the flow rate of the mixed gas introduced into the combustion catalyst chamber needs to be faster than the flame propagation speed in order to prevent backfire to the mixed gas. However, such a catalytic combustion device has a fatal problem in that it cannot be operated at low loads.

Furthermore, there is energy loss due to increasing the flow rate of the mixed gas, which is not preferable from the point of view of improving system efficiency.

On the other hand, in order to solve these MI problems, air or exhaust air with a lower oxygen concentration than normal air and flammable gas are mixed together without exceeding the flammability limit and introduced into the combustion catalyst chamber for combustion. It is also possible to introduce the insufficient amount of air, combustible gas, and exhaust air into the combustion catalyst chamber after that, but such a method requires a large amount of combustion catalyst and is uneconomical. Moreover, the number of gas introduction parts increases further, making the device configuration complicated, which is not preferable.

[Purpose of the Invention] The present invention has been made to solve the above-mentioned problems, and its purpose is to reliably prevent flashback without increasing the flow rate of the mixed gas introduced into the combustion catalyst chamber, To provide a catalytic combustion device that is inexpensive and has a simple configuration, capable of withstanding low-load operation and performing stable catalytic combustion with little energy loss.

[Summary of the Invention J In order to achieve the above object, the present invention mixes air or air with a lower oxygen concentration than normal air with a flammable gas in a mixer, and mixes this mixed gas with a combustion catalyst filled with a combustion catalyst. In a catalytic combustion device that introduces the combustible gas into a combustion catalyst chamber and burns it in the presence of the combustion catalyst, a porous solid material with high porosity and permeability is provided on the mixed gas introduction side of the combustion catalyst chamber. It is characterized in that it is configured by providing the following information.

[Embodiments of the invention] An embodiment of the present invention shown in the drawings will be described below.

The figure shows an example of the configuration of a catalytic combustion device according to the present invention. In the figure, 1 is a mixer that mixes combustible gas 2 and air or exhaust air 3 (from a fuel cell, not shown), which has a lower oxygen concentration than normal air. Further, 4 is a combustion catalyst chamber in which a combustion catalyst 41 is filled in a container 42 and into which the mixed gas from the mixer 1h1 is introduced, in which the combustible gas 2 is combusted in the presence of this combustion catalyst 41, The high-temperature combustion gas 5 is supplied to a desired gas utilization target such as a reforming pipe of a reforming device. Further, reference numeral 6 is a porous solid material such as ceramic having extremely high porosity and permeability, and is provided between the combustion catalyst chamber 4 and the mixer 1, that is, on the mixed gas introduction side of the combustion catalyst chamber 4. In this case, combustible gas 2. Air or exhaust air 3 is approximately 400
Preheated to ℃. Further, as the mixer 1, an efficient mixer with low pressure loss is used.

In a catalytic combustion device having such a configuration, combustible gas 2 is introduced into mixer 1 together with air or exhaust air 3 whose oxygen concentration is lower than that of normal air. The mixed gas of combustible gas 2 and air or exhaust air 3 mixed in this mixer 1 passes through a permeable porous solid material 6 with extremely high porosity with almost no pressure loss. From this point, it is introduced into the combustion catalyst chamber 4. In this combustion catalyst chamber 4, the combustible gas 2 is combusted by air or exhaust air 3 in the presence of a combustion catalyst I [41], and becomes a high-temperature combustion gas 5 which is discharged to a gas utilization target (not shown) for various purposes. It will be used for

In this case, if the porous solid material 6 were not present, backfire would occur if the gas flow rate inside the mixer 1 became slower than the flame propagation speed due to heat radiation from the upper part of the combustion catalyst 41, which had reached a high temperature. Combustion occurs inside 1. In this case, this combustion is no longer catalytic combustion but similar to normal burner combustion, and the amount of Nox in the high temperature combustion gas 5 increases compared to catalytic combustion. In this regard, in the configuration of this embodiment, since the porous solid material 6 is present on the mixed gas introduction side of the combustion catalyst chamber 4 as shown in the figure, the gas flow velocity inside the mixer 1 is slower than the flame propagation velocity. Even if this occurs, the effect of high temperature when combustion occurs in the combustion catalyst chamber 4 is blocked by the porous solid material 6, and no flashback phenomenon from the combustion catalyst chamber 4 to the mixing chamber 1 occurs. Therefore, the function as a catalytic combustion device is sufficiently maintained, and stable low NOx combustion can be achieved even under low load. In the above, even if the mixed gas is preheated to such an extent that the gas does not ignite, there is no functional problem.

As described above, according to the catalytic combustion apparatus configured in this embodiment, the following effects can be obtained.

(a) Since a porous solid material 6 with high porosity and permeability is provided on the mixed gas introduction side of the combustion catalyst chamber 4,
It becomes possible to reliably prevent flashback without increasing the flow rate of the mixed gas introduced into the combustion catalyst chamber 4 as in the conventional case. As a result, it is possible to operate at a low load and to perform stable catalytic combustion with little energy loss.

(b) Due to the reason in paragraph (a) above, in order to solve the problem of inability to operate at low loads and energy loss due to increasing the flow rate of mixed gas, air or exhaust air and flammable gas There is no need to mix the mixture without exceeding the flammability limit and introduce it into the combustion catalyst chamber for combustion, and then introduce the insufficient air, combustible gas, and exhaust air into the combustion catalyst chamber. Become. As a result, it is possible to reduce costs by omitting the combustion catalyst required for this, and it is also possible to simplify the device configuration by reducing the number of gas introduction sections.

It should be noted that the present invention is not limited to the above embodiments, and can be implemented with various modifications without changing the gist thereof.

[Effects of the Invention] As explained above, according to the present invention, air or air with a lower oxygen concentration than normal air is mixed with a flammable gas, and this mixed gas is mixed with a combustion catalyst filled with a combustion catalyst. In a catalytic combustion device that introduces the combustible gas into a combustion catalyst chamber and burns it in the presence of the combustion catalyst, a porous solid material with high porosity and permeability is provided on the mixed gas introduction side of the combustion catalyst chamber. This structure reliably prevents flashback without increasing the flow rate of the mixed gas introduced into the combustion catalyst chamber, and allows stable catalytic combustion to withstand low-load operation and with little energy loss. It is possible to provide a catalytic combustion device that is inexpensive and has a simple configuration.

[Brief explanation of the drawing]

The figure is a configuration diagram showing an embodiment of the present invention. 1... Mixer, 2... Flammable gas, 3... Air or exhaust air with low oxygen concentration, 4... Combustion catalyst chamber, 41
... Combustion catalyst, 42... Container, 5... ＾ Warm combustion gas, 6... Porous solid material.

Claims (1)

[Claims] Air or air with a lower oxygen concentration than normal air is mixed with a combustible gas in a mixer, and this mixed gas is introduced into a combustion catalyst chamber filled with a combustion catalyst. A catalytic combustion device for combusting a reactive gas, characterized in that a permeable porous solid material with a high porosity is provided on the mixed gas introduction side of the combustion catalyst chamber.