JPH11218325A - Method for burning by thermal storage with reducing flame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for conducting a stably thermal storage burning with a reducing flame by improving a temperature distribution in a furnace. SOLUTION: A low oxygen air is supplied as a burning air of a burner 2 for a thermal storage burning, and burned by a reducing flame. The air is supplied to a burning gas containing unburned combustibles to this side of a burner 3 of an exhaust side, completely burned, and an exhaust heat is recovered through a thermal storage unit 5. The exhaust gas removed from the burner 3 of the exhaust side is circulated to the burner 2 of the burning side through an exhaust gas circulating route, and used as a burning air. A gas flow rate in a furnace is assured irrespective of the reducing burning, and its temperature distribution is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for storing and burning heat in a reducing flame suitable for reducing and firing ceramic products.

[0002]

2. Description of the Related Art Many ceramic products are fired at a high temperature of 800 ° C. or more in a reducing atmosphere. For this reason, a burner for reduction combustion capable of reducing the air ratio to less than 1 has conventionally been used in a firing furnace for ceramic products. And supply combustion air in the flue to produce harmful CO
Etc. were completely oxidized and released into the atmosphere.

However, in this method, the heat retained in the exhaust gas is wastefully released to the atmosphere. In this heat storage combustion method, for example, as shown in Japanese Patent Application Laid-Open No. Hei 7-133908, a plurality of burners provided with a heat storage body in an air flow passage are alternately burned so that exhaust and combustion are repeated in a short cycle. In this method, high-temperature exhaust gas is passed through a regenerator to recover exhaust heat, and during the next combustion, combustion air is passed through the regenerator to preheat the combustion air to a high temperature.

[0004] Naturally, when this heat storage combustion method is used for reduction combustion, the amount of combustion air must be reduced significantly in comparison with ordinary oxidation combustion in order to maintain the inside of the furnace in a reducing atmosphere. However, when the combustion is throttled, the amount of the combustion gas also decreases, so that the effect of stirring the gas in the furnace decreases. As a result, the temperature distribution in the furnace deteriorates.
A temperature difference of about 0 ° C. sometimes occurred. This phenomenon was particularly remarkable in a region where the amount of combustion was reduced in order to keep the furnace temperature constant.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems and to provide a method capable of performing heat storage combustion with a reducing flame without deteriorating the temperature distribution in the furnace. It was done.

[0006]

According to a first aspect of the present invention, there is provided a fuel cell system in which a plurality of burners provided with a heat storage element are alternately burned so that exhaust and combustion are repeated in a short cycle. A combustion method for preheating by passing combustion air through a regenerator heated by the above method, characterized in that low oxygen air is used as combustion air to burn with a reducing flame. A second invention made to solve the same problem is that a plurality of burners provided with a heat storage body are exhausted / burned.
A heat storage combustion method in which combustion is alternately burned so as to be repeated in a short cycle, and preheated by passing combustion air through a heat storage body heated by exhaust gas, while using low oxygen air as combustion air to burn with a reducing flame, Air is supplied in front of the burner on the exhaust side to perform complete combustion, and exhaust gas extracted from the burner on the exhaust side is circulated to the burner on the combustion side to be used as combustion air. . In any of the inventions, low oxygen air diluted with an inert gas may be used.

According to these inventions, since low oxygen air is used as combustion air, the amount of gas in the furnace can be increased while performing reduction combustion. Therefore, the inside of the furnace is sufficiently stirred by the combustion gas, and the temperature distribution is improved. In particular, in the second aspect, the exhaust gas is circulated to the burner on the combustion side and is used as combustion air, so that there is no waste of energy, and since air is supplied before the burner on the exhaust side to perform complete combustion, High-temperature combustion gas can be circulated, and the gas circulating outside the furnace is completely burned and does not contain harmful CO or the like. Hereinafter, preferred embodiments of the present invention will be described.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Invention) In the schematic diagram of FIG. 1, reference numeral 1 denotes a furnace body of a firing furnace for performing reduction firing of a ceramic product, and burners 2, which alternately burn on both sides thereof,
3 are arranged. In practice, many pairs of burners are arranged, but FIG. 1 shows only a pair of burners 2, 3. In FIG. 1, the left burner 2 is shown as being in a combustion state, and the right burner 3 is shown as being in an exhaust state. However, as described above, the exhaust and combustion of each burner are switched in a short cycle of about 30 seconds. Be driven. The switching device and the like for this purpose are well known in the industry, and thus description thereof is omitted.

Each of the burners 2 and 3 is provided with a heat storage body 4 and 5 made of a heat-resistant material such as a ceramic honeycomb. In the burner 2 on the combustion side, gas is supplied from the gas supply pipe 6 to the preheated combustion air passing through the regenerator 4 to perform combustion. On the other hand, in the burner 3 on the exhaust side, the combustion gas heats the regenerator 5, and the exhaust heat is recovered. The above points are not particularly different from the prior art.

However, in the present invention, low oxygen air is used as combustion air. This low oxygen air has an oxygen concentration of 21%
Means less than air and can be obtained, for example, by diluting air with an inert gas such as nitrogen gas. Since gas is supplied to the low-oxygen air in the burner 2 on the combustion side, the combustion is performed by the reducing flame and the inside of the furnace is kept in a reduced state, so that the ceramic product can be reduced and fired. In addition,
Since the combustion air is heated to a high temperature of 600 ° C. or higher by the regenerator 4, stable combustion is possible even with low oxygen air.

The combustion gas is exhausted from the burner 3 on the opposite side across the furnace. Preferably, additional air is supplied from the air supply pipe 7 to a portion in front of the burner 3 so that unburned fuel in the combustion gas is removed. To complete combustion. Thereby, the temperature of the combustion gas further rises, and the exhaust heat recovery by the heat storage body 5 of the burner 3 is more effectively performed. As described above, in the first invention, since the burner 2 is burned by the reducing flame with the low oxygen air, the amount of gas flowing in the furnace increases, and the inside of the furnace is sufficiently stirred to reduce the temperature distribution in the furnace. Can be improved.

(Second Invention) FIG. 2 shows an embodiment of the second invention. Also in this second invention, low-oxygen air is used as the combustion air, and gas is supplied to the low-oxygen air in the burner 2 on the combustion side. Therefore, combustion is performed by the reducing flame to keep the inside of the furnace in a reducing state, Reduction firing of ceramic products becomes possible. The combustion gas is exhausted from the burner 3 on the opposite side across the inside of the furnace, and air is additionally supplied to a portion in front of the burner 3 from the air supply pipe 7 to completely burn unburned components in the combustion gas. Let it. Thereby, the temperature of the combustion gas further rises, and the exhaust heat recovery by the heat storage body 5 of the burner 3 is more effectively performed. The furnace body 1 may be provided with an exhaust port to exhaust a part of the gas in the furnace.

Further, in the second invention, the burner 3 on the exhaust side is provided.
The exhaust gas taken out from the combustion chamber is circulated to the combustion side burner 2 through an exhaust gas circulation path 9 provided with a circulation fan 8, mixed with air supplied from a blower 10, and used as low oxygen combustion air. The first advantage is that the thermal energy of the combustion gas can be effectively used. Second
In addition, the exhaust gas that has become substantially free of oxygen by completely burning unburned components can be used as the low oxygen air. The exhaust gas may be circulated in its entirety, but as shown in FIG.
May be partially exhausted.

In this second invention, too, the burner 2 is burned with a reducing flame using low oxygen air, so that the amount of gas flowing in the furnace increases, and the inside of the furnace is sufficiently agitated to reduce the temperature distribution in the furnace. Can be improved. Further, since the exhaust heat is effectively recovered by the heat storage combustion method including the exhaust gas circulation path 9, a high energy saving effect can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific heat balance in a firing furnace for performing heat storage combustion with a reducing flame according to the second invention will be described below. 371 Nm ³ / h at a temperature of 250 ° C. supplied from the exhaust gas circulation path 9
Of exhaust gas and 350 Nm ³ / h of fresh air mixed at a temperature of 25 ° C. supplied from the blower 10 at a temperature of 14
Low oxygen air having a flow rate of 1 ° C., a flow rate of 721 Nm ³ / h and an oxygen concentration of 12% is supplied to the burner 2 shown in FIG. The temperature of the low-oxygen air rises to 1119 ° C. when passing through the regenerator 4, and 68 Nm ³ / h of gas is supplied from the gas supply pipe 6 at 25 ° C. to reduce and burn the burner 2. The state is reduced to a high temperature of 5% at a temperature of 996 ° C., and the ceramic product is reduced and fired.

A part of the gas in the furnace is exhausted from the furnace body 1 at a rate of 302 Nm ³ / h to the outside of the system, and since there is also heat taken out by the product, a total heat of 600,000 kcal / h is discharged from the furnace. Released. The gas in the furnace was completely burned at an air ratio of 1.2 by receiving 238 Nm ³ / h of air at a temperature of 25 ° C. from the air supply pipe 7 near the outlet at an air ratio of 1.2.
28 ° C. When the high-temperature exhaust gas passes through the heat storage unit 5 of the burner 3 on the exhaust side, a heat amount of 220,000 kcal / h is recovered. The exhaust gas whose temperature has dropped to 250 ° C is 7
21Nm flow of exhaust gas circulation path 9 at a flow rate of ³ / h, middle and evacuated 350 Nm ³ / h to the outside of the system 371 nm ³ / h is fed to the burner 2. Since the combustion and exhaust states of the burners 2 and 3 are switched at short intervals, almost the entire amount of heat of 220,000 kcal / h recovered by the heat storage unit 5 is used to preheat air when the burner 3 burns next time. used.

As described above, in the present invention, as a result of a large amount of gas flowing in the furnace, the temperature distribution in the furnace is greatly improved, and the maximum temperature difference in the furnace is 30 ° C. in a conventional regenerative combustion furnace using a reducing flame. However, it was confirmed that the temperature can be reduced to 10 ° C. or less. The gas flow rate in the furnace is about three times that of the conventional furnace using the regenerative combustion method for reduction combustion.

[0018]

As described above in detail, according to the heat storage combustion method using the reducing flame of the first and second inventions, the gas flow rate in the furnace is increased by using low oxygen air. It is possible to perform stable heat storage combustion with the reducing flame while improving the temperature distribution.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a heat storage combustion method according to a first invention.

FIG. 2 is a schematic diagram showing a heat storage combustion method according to a second invention.

[Explanation of symbols]

1 Furnace body, 2 burners, 3 burners, 4 heat storage units, 5
Heat storage unit, 6 gas supply pipe, 7 air supply pipe, 8 circulation fan, 9 exhaust gas circulation path, 10 blower

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[Procedure amendment]

[Submission date] January 21, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

According to a first aspect of the present invention, there is provided a fuel cell system comprising: a plurality of burners provided with a heat accumulator which are alternately burned so that exhaust / combustion is repeated in a short cycle; A heat storage combustion method in which combustion air is preheated by passing combustion air through a heat storage body heated by a furnace.
It is characterized in that the amount of gas flowing through the inside is increased . The second was made to solve the same problem.
The invention relates to a regenerative combustion method in which a plurality of burners provided with regenerators are alternately burned so that exhaust and combustion are repeated in a short cycle, and preheated by passing combustion air through regenerators heated by exhaust gas, Gas flowing through the furnace by burning it with a reducing flame using low oxygen air
Increasing the amount and supplying air before the burner on the exhaust side to perform complete combustion, and circulating the exhaust gas extracted from the burner on the exhaust side to the burner on the combustion side to use it as combustion air. It is a feature. In any of the inventions, low oxygen air diluted with an inert gas may be used.

Claims (3)

[Claims] 1. A regenerative combustion method in which a plurality of burners provided with a regenerator are alternately burned so that exhaust and combustion are repeated in a short cycle, and preheating is performed by passing combustion air through a regenerator heated by exhaust gas. A heat storage combustion method using a reducing flame, characterized in that low-oxygen air is used as the air to burn with a reducing flame. 2. A regenerative combustion method in which a plurality of burners provided with a regenerator are alternately burned so that exhaust and combustion are repeated in a short cycle, and preheated by passing combustion air through a regenerator heated by exhaust gas. Using low-oxygen air as the air and burning with a reducing flame, air is supplied before the burner on the exhaust side to perform complete combustion, and all or part of the exhaust gas extracted from the burner on the exhaust side A heat storage combustion method using a reducing flame, wherein the method is circulated to a combustion side burner and used as combustion air. 3. The method according to claim 1, wherein the combustion air is low oxygen air diluted with an inert gas.