JP2001201044A - Pulverized coal firing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize heat recovery equipment by reducing the burning out time of pulverized coal. SOLUTION: A burner is formed by arranging at least a pair of heat exchangers 16 provided with thermal storage bodies 16b made of honeycomb ceramic on the furnace walls 1a of combustion furnaces 1, connecting combustion air supply and combustion gas exhaust pipes 15 on the upstream side of these heat exchangers 16, and connecting combustion air and combustion gas exhaust paths 3A surrounding the burner inner cylinder 3B on the down stream side of the heat exchangers 16. A pulverized coal supply pipe 14 is connected to the burner inner cylinder 3B, a combustion air supply pipe 15a and a combustion gas exhaust pipe 15b are connected to the other end of the combustion air supply and combustion gas exhaust pipe 15b through a four-way valve 17, combustion air 11 heated through the heat exchanger 16 and pulverized coal 19 from the burner inner cylinder 3B are fed to one burner 3a and burned by switching the four-way valve 17 periodically, and the heat exchanger 16 is heated and the combustion gas 13 is cooled by feeding the combustion gas 13 reversely flown from the other burner 3b to the heat exchanger 16 while switching between the one burner 3a and the other burner 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulverized coal combustion apparatus, and more particularly to a pulverized coal combustion apparatus for burning pulverized coal in high-temperature air to recover heat of high-temperature combustion exhaust gas.

[0002]

2. Description of the Related Art In pulverized coal combustion, coal pulverized by a pulverizer is sent to a burner together with combustion air, and is injected into a combustion chamber while being forcibly mixed with secondary air sent through an air passage at a burner section. You. The air jet containing pulverized coal entering the furnace is ignited by high-temperature radiant heat and convective heat to form a flame and burn.

In an industrial furnace or the like, gaseous fuel such as propane is mainly burned to recover heat of a high-temperature flue gas by a regenerator made of honeycomb, and combustion air is heated to a high temperature by the recovered heat. High-temperature air combustion for burning gaseous fuel is known, but is not applied to pulverized coal combustion.

FIG. 3 is a conceptual diagram of a conventional pulverized coal-fired boiler. In the figure, reference numeral 1 denotes a combustion furnace of a pulverized coal-fired boiler. Reference numeral 1a denotes a furnace wall of the combustion furnace 1. 2 is a combustion chamber.
Reference numeral 3 denotes a plurality of combustion burners disposed on the furnace wall 1a. 4
Is a combustion air supply pipe. 4a is a pulverized coal supply pipe connected to the middle of the combustion air supply pipe 4, and 4b is a combustion air supply pipe and a pulverized coal supply pipe. 5 is a steam pipe. 6 is a super heater, and 6a is an economizer. Reference numeral 7 denotes a flue gas denitration device provided downstream of the combustion furnace 1, reference numeral 8 denotes an air preheater, reference numeral 9 denotes an electric dust collector, and reference numeral 10 denotes a flue gas desulfurization device. 11 is combustion air. 12 is a flame, 13 is a combustion exhaust gas. 19 is pulverized coal.

[0005] The high-temperature flue gas 13 generated by the combustion of the pulverized coal 19 is discharged from above the combustion chamber 2, heats the superheater 6 and the economizer 6 a downstream thereof, and further flows downstream of the combustion furnace 1. When passing through the provided flue gas denitration apparatus 7 and passing through the air preheater 8, the combustion air 11
Is heated to about 300 ° C., and the temperature is lowered to 200 ° C. or lower, and the electric dust collector 9 and the flue gas desulfurizer 1
Emitted from the chimney through zero. The combustion air 11 heated to about 300 ° C. through the air preheater 8 is mixed with the pulverized coal 19 sent from the pulverized coal supply pipe 4 a connected to the middle of the combustion air supply pipe 4 and is supplied to the combustion burner 3. It is sent and burned in the combustion chamber 2.

[0006]

In such a conventional pulverized-coal-fired boiler, combustion air is supplied to an air preheater by an air preheater.
Since it can be heated only to about 00 ° C., its ignitability and burnout are poor. Poor ignitability makes it impossible to use coal with a high fuel ratio, such as anthracite. Due to poor burning, the size of the furnace, which is governed by the burning time, cannot be reduced. In addition, since the heat transfer coefficient cannot be increased so much with an economizer or an air preheater, the size of the entire apparatus increases. There is a problem that an economizer and an air preheater must be provided for exhaust heat recovery, and the entire apparatus must be enlarged.

The present invention has been made in order to solve the above-mentioned problems. The present invention applies high-temperature air combustion using gaseous fuel, which is performed in an industrial furnace, to pulverized coal combustion to achieve high-temperature combustion. Quickly recovers the exhaust heat of the combustion exhaust gas from
Eliminating equipment such as an economizer and air preheater to reduce the size of the heat recovery unit, and increasing the temperature of the combustion air to burn it in a combustion furnace at a high temperature, shortening the burn-out time and reducing the volume of the combustion chamber It is another object of the present invention to provide a pulverized coal combustion apparatus capable of burning even anthracite having a high fuel ratio without volatile components.

[0008]

According to the present invention, at least one pair of heat exchangers having a honeycomb-shaped ceramic regenerator is provided on a furnace wall of a combustion furnace. A combustion air supply pipe and a combustion exhaust gas discharge pipe are connected to the upstream side of the heat exchanger, and a combustion air path and a combustion exhaust gas discharge path provided to surround the burner inner cylinder are connected to the downstream side to form a burner. A pulverized coal supply pipe is connected to the burner inner cylinder, and a combustion air supply pipe and a combustion exhaust gas discharge pipe are connected to the other end of the combustion air supply pipe and the combustion exhaust gas discharge pipe via a four-way switching valve. By switching the four-way switching valve periodically, the heated combustion air is sent to one burner through the heat exchanger, and the pulverized coal is sent from the burner inner cylinder to be burned, and the other burner is burned. The flue gas that flows back is sent to the heat exchanger. While heating the heat exchanger, to perform the cooling of the flue gas, which one of the burners and other pulverized coal combustion apparatus so as to alternately performed in the burner is provided.

Next, the operation of the present invention will be described. According to the pulverized coal combustion device of the present invention, of the pair of burners disposed in the combustion furnace, first, combustion air and pulverized coal are mixed from one burner and supplied into the combustion furnace, and ignited by a spark plug (not shown). And burn. The high-temperature combustion exhaust gas generated by combustion of the combustion air and the pulverized coal flows back through the other burner and is discharged from the combustion furnace. At this time, the high-temperature combustion exhaust gas heats a honeycomb-shaped ceramic heat storage element of a heat exchanger connected to the burner. Next, switch the four-way switching valve,
The supply of combustion air to the burner that was burning is stopped, and the supply of pulverized coal is stopped. Conversely, the combustion air and the pulverized coal are mixed into the burner that has been stopped and supplied to the combustion furnace for combustion. When passing through the heat exchanger, the combustion air is heat-exchanged by the heat exchanger heated to a high temperature by the combustion exhaust gas to reach a high temperature of 800 ° C to 1,000 ° C and supplied to the combustion furnace. When the high-temperature flue gas exchanges heat with the combustion air via a heat exchanger, the temperature is lowered to 200 ° C. or less, and the flue gas passes through a flue gas treatment device such as a flue gas denitration device provided downstream of the combustion furnace and the chimney. Released from

As described above, 1,0 discharged from the combustion furnace
The heat exchange between the combustion exhaust gas having a high temperature of 00 ° C. or more and the combustion air supplied into the combustion furnace is performed through a heat exchanger having a heat storage body made of a honeycomb ceramic having a very large temperature gradient between a high temperature portion and a low temperature portion. Thus, the combustion air can be heated to 800 ° C. to 1,000 ° C. by the heat exchanger having the heat storage body and supplied to the combustion furnace. Therefore, the combustion reaction of the pulverized coal is promoted by the high-temperature combustion air, so that the burn-out time can be shortened and the volume of the combustion chamber can be made compact. Further, since the ignitability is improved, it is possible to increase the types of coal that can be burned, such as anthracite having a high fuel ratio. Furthermore, since the exhaust heat of the high-temperature combustion exhaust gas can be rapidly cooled to 200 ° C or less by a heat exchanger having a ceramic heat accumulator, there is no need for a heat recovery device such as an economizer or air preheater, and the entire device can be made more compact. Can be planned.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of a pulverized coal combustion apparatus according to the present invention, and FIG. 2 is an enlarged view of a heat exchanger having a honeycomb-shaped ceramic heat accumulator related to FIG. Note that components common to those described in the conventional example of FIG. 3 are described using the same reference numerals, and redundant description will be omitted.

1 and 2, reference numeral 1 denotes a combustion furnace of a pulverized coal combustion apparatus. Reference numeral 1a denotes a furnace wall of the combustion furnace 1. 2
Denotes a combustion chamber of the combustion furnace 1. Burners 3a and 3b are arranged in two pairs in one combustion furnace 1. FIG. 1 shows an example in which three combustion furnaces 1 are juxtaposed. Each of the burners 3a and 3b includes a burner inner cylinder 3B and a combustion air path and a combustion exhaust gas discharge path 3A provided so as to surround the inner cylinder 3B. 18 and an inner vane 18a are provided.
The outer vane 18 and the inner vane 18a control the feed amounts of the primary combustion air 11a and the secondary combustion air 11b, and the primary combustion air 11a and the secondary combustion air 11b.
A swirling flow is formed at b. Further, a heat exchanger described later is connected to the upstream side of the burners 3a and 3b. 5 is a steam pipe. Reference numeral 7 denotes a flue gas denitration device provided on the downstream side of the combustion furnace 1, and 9 denotes an electric dust collector,
0 is a flue gas desulfurization unit. Reference numeral 15 denotes a combustion air supply pipe and a combustion exhaust gas discharge pipe. Reference numeral 16 denotes a heat exchanger (hereinafter, referred to as a "heat storage heat exchanger") having a honeycomb-shaped ceramic heat storage connected to the upstream side of the burners 3a and 3b. 1
Reference numeral 7 denotes a four-way switching valve described later.

As shown in FIG. 2, the regenerative heat exchanger 16 has a combustion air supply pipe and a combustion exhaust gas discharge pipe 15 connected to an upper surface of a cylindrical body 16a, and a burner 3a (3b) connected to a lower surface. . A heat storage body 16b made of honeycomb ceramics is provided in the middle of the cylindrical body 16a. The material of the ceramic is preferably cordierite (2MgO.2Al ₂ O ₃ .5SiO ₂ ) in terms of low coefficient of thermal expansion and thermal shock resistance. Combustion air 1
1 and the combustion exhaust gas 13 are alternately sent by switching this heat storage body 16b periodically. In addition,
The specific heat of ceramics is about 0.2 KCaI / Kg ° C., whereas the specific heat of metal is about 0.1 KCaI / Kg ° C., so that the heat capacity is large. Since the honeycomb-shaped ceramics have high heat resistance, the temperature of the heat storage type heat exchanger 16 can be increased, and the porosity and the surface area are large, so that the efficiency of heat exchange is high. Further, a high temperature gradient can be obtained between the low temperature side and the high temperature side.

The four-way switching valve 17 has one end connected to the pair of regenerative heat exchangers 16 and the other end of the combustion air supply pipe and combustion exhaust gas discharge pipe 15, one end of the combustion air supply pipe 15a and the combustion exhaust gas discharge pipe 15b. And one end of each. By periodically switching the four-way switching valve 17, the combustion air heated through the regenerative heat exchanger 16 is sent to one burner 3a, and the pulverized coal 19 is sent from the burner inner cylinder 3B together with the air for conveyance. The combustion exhaust gas 13 that has been burned and has flowed back through the other burner 3b is stored in the regenerative heat exchanger 1.
6, the regenerative heat exchanger 16 is heated, and heat recovery by rapid cooling of the combustion exhaust gas 13 is performed, and the heat is alternately performed by one burner 3a and the other burner 3b.

Next, the operation based on the embodiment will be described. According to the pulverized coal combustion apparatus of the present invention, the combustion exhaust gas 13 having a high temperature of 1,000 ° C. or more discharged from the combustion furnace 1 and the combustion air 11 supplied into the combustion furnace 1 are heated at a high temperature portion and a low temperature portion. Heat exchanger 16 having heat storage body 16a made of honeycomb ceramic having a very large gradient (heat storage heat exchanger)
Heat exchange through the combustion air 11,
The temperature can be raised to 800 ° C. to 1,000 ° C. by the regenerative heat exchanger 16 and supplied to the combustion furnace 1. Therefore, since the combustion reaction of the pulverized coal 19 is promoted by the high-temperature combustion air 11, the burn-out time can be shortened,
The volume of the combustion chamber 2 can be made compact. Further, since the ignitability is improved, it is possible to increase the types of coal that can be burned, such as anthracite having a high fuel ratio. Further, since the exhaust heat of the high-temperature combustion exhaust gas 13 can be rapidly cooled to 200 ° C. or lower by the heat exchanger 16 having the ceramic heat storage body 16a, heat recovery equipment such as an economizer and an air preheater is eliminated, and the entire apparatus is eliminated. Compactness can be achieved.

The present invention is not limited to the above embodiment. For example, the heat storage body of the heat exchanger may be made of honeycomb-shaped alumina ceramics instead of honeycomb-shaped cordierite ceramics. Further, a single steam pipe is designed to convert water to superheated steam, but the evaporation chamber and the superheated steam pipe may be separated.
Of course, various changes can be made without departing from the spirit of the present invention. .

[0017]

As described above, according to the present invention, the combustion air and the combustion exhaust gas are heat-exchanged by the regenerative heat exchanger, and the combustion air heated by the regenerative heat exchanger is supplied to the combustion furnace. To promote the combustion reaction of pulverized coal, shortening the burn-out time, making the volume of the combustion chamber compact, and improving the ignitability to expand the types of coal that can be used be able to. In addition, the regenerative heat exchanger can quickly cool the exhaust heat of the high-temperature combustion exhaust gas and recover heat.This eliminates the need for devices such as economizers and air preheaters, and makes it possible to reduce the size of the entire system. It works.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a pulverized coal combustion device according to the present invention.

FIG. 2 is an enlarged sectional view of a regenerative heat exchanger related to FIG.

FIG. 3 is a conceptual diagram of a conventional pulverized coal-fired boiler.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Combustion furnace 1a Furnace wall 2 Combustion chamber 3,3a, 3b Burner 3A Combustion air path and flue gas discharge path 3B Burner inner cylinder 4,15a Combustion air supply pipe 4a, 14 Pulverized coal supply pipe 11 Combustion air 13 Combustion exhaust gas 15 Combustion Air supply pipe / combustion exhaust gas discharge pipe 15b Combustion exhaust gas discharge pipe 16 Heat exchanger (heat storage heat exchanger) 16a Cylindrical body 16b Heat storage body made of honeycomb ceramic 17 Four-way switching valve 19 Pulverized coal

Claims (1)

[Claims] At least one pair of heat exchangers having a heat storage body made of honeycomb-shaped ceramics are disposed on a furnace wall of a combustion furnace, and a combustion air supply pipe and a combustion exhaust gas discharge are provided upstream of these heat exchangers. A pipe is connected, and a combustion air path and a flue gas discharge path provided so as to surround the burner inner cylinder are connected on the downstream side to constitute a burner, and a pulverized coal supply pipe is connected to the burner inner cylinder, and the above combustion is performed. The other end of the air supply pipe and the flue gas discharge pipe is connected to the combustion air supply pipe and the flue gas discharge pipe via a four-way switching valve, and by periodically switching the four-way switching valve, one burner can be connected. The heated combustion air is sent through the heat exchanger, and the pulverized coal is sent from the burner inner cylinder to burn it, and the combustion exhaust gas flowing backward through the other burner is sent to the heat exchanger to heat the heat exchanger. At the same time, let the combustion exhaust gas cool, A pulverized coal combustion apparatus characterized in that these are alternately performed by one burner and the other burner.