JP2001221430A - Pulverized coal combustor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the burn up time for pulverized coal and make a heat recovery device compact. SOLUTION: A combustor comprises at least one pair of burners 3a, 3b disposed on a furnace wall 1a of a combustion furnace 1A, a pulverized coal supply pipe 14 connected to an inner cylinder 3B of the burner, a pipe 15 for supplying combustion air and discharging combustion exhaust gas whose one end is connected to a path 3A doubling as a combustion air supplying path and a combustion exhaust gas discharging path, with the other end of the pipe 15 being connected to a four-way switching valve 17, and a cyclone 20 and a heat exchanger 16 which are intermediately connected between the burners 3a, 3b and the valve 17. By periodically switching the valve 17, heated combustion air 11 is transferred to one burner 3a through the heat exchanger 16, and thus pulverized coal 19 transferred from the cylinder 3B is combusted. Further, combustion exhaust gas 13 which has flowed back through the other burner 3b is transferred to the heat exchanger 16 through the cyclone 20 to conduct cooling of the gas 13 as well as heating of the heat exchanger 16, and thus fly 21 ash contained in the gas 13 is removed by the cyclone 20.

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

In FIG. 1, 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.

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 on the downstream side, and further flows on the downstream side 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.

[0007]

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, thereby achieving 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.

[0009]

According to the present invention, at least a burner provided with a combustion air path and a combustion exhaust gas discharge path on a furnace wall of a combustion furnace so as to surround a burner inner cylinder is provided. One pair is provided, and a pulverized coal supply pipe is connected to the burner inner cylinder, and one end of the combustion air supply pipe and the combustion exhaust gas discharge pipe is connected to the combustion air path and the combustion exhaust gas discharge path. A four-way switching valve is connected to the other end of the pipe and the flue gas exhaust pipe, and a cyclone is provided between the combustion air supply pipe and the flue gas exhaust pipe that connects the burner and the four-way switching valve.
Heat exchangers each having a heat storage body made of honeycomb ceramics are connected to each other, and by periodically switching a four-way switching valve, heated combustion air is sent to one burner through the heat exchanger, and Pulverized coal is sent from the inner cylinder and burned, and the flue gas that has flowed back through the other burner is sent to a heat exchanger via a cyclone to heat the heat exchanger and to cool the flue gas, causing the flue gas to cool. Provided is a pulverized coal combustion apparatus in which fly ash contained therein is removed by a cyclone, and these are alternately performed by one burner and the other burner.

Next, the operation of the present invention will be described.

[0011] According to the pulverized coal combustion apparatus of the present invention, the high temperature exhaust gas discharged from the combustion furnace and the combustion air supplied to the combustion furnace and the temperature gradient between the high temperature section and the low temperature section. The heat exchange is performed through a heat exchanger having a heat storage body made of a honeycomb-shaped ceramic having a very large temperature, so that the combustion air can be heated to 800 ° C. to 1,000 ° C. 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. 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 storage unit, the overall equipment can be made compact by eliminating heat recovery equipment such as economizers and air preheaters. Can be. Further, since fly ash is removed by the cyclone provided on the upstream side of the heat exchanger, the fly ash does not reach the heat exchanger, and the fly ash does not adhere to the heat exchanger to cause blockage.

[0012]

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 view of a pulverized coal combustion apparatus according to the present invention, and FIG. 2 is an enlarged sectional view of a burner. FIG. 3 is an enlarged sectional view of the regenerative heat exchanger. Note that components common to those described in the conventional example of FIG. 4 will be described using the same reference numerals, and redundant description will be omitted.

1 to 3, reference numeral 1A denotes a combustion furnace of a pulverized coal combustion apparatus. 1a is a furnace wall of the combustion furnace 1A. Reference numeral 2 denotes a combustion chamber of the combustion furnace 1. Burners 3a and 3b are provided in two pairs in one combustion furnace 1A. The burners 3a and 3b include a burner inner cylinder 3B and a combustion air path / combustion exhaust gas discharge path 3 provided so as to surround the burner inner cylinder 3B.
A, an outer vane 18 and an inner vane 18a are disposed in the combustion air passage / combustion exhaust gas discharge passage 3A. 11 is combustion air. Outer vane 1
The inner vane 8 and the inner vane 18a control the feed amount of the primary combustion air 11a and the secondary combustion air 11b, and form a swirling flow between the primary combustion air 11a and the secondary combustion air 11b. Pulverized coal supply pipes 14A and 14B are connected to the burner inner cylinder 3B. One end of a combustion air supply pipe / combustion exhaust gas discharge pipe 15A, 15B is connected to the combustion air path / combustion exhaust gas discharge path 3A. A four-way switching valve 17 to be described later is connected to the other ends of the combustion air supply pipe and the combustion exhaust gas discharge pipes 15A and 15B. Cyclones 20A, 20B, which will be described later, are connected between the combustion air supply pipe and the combustion exhaust gas discharge pipes 15A, 15B.
Further, a combustion air supply pipe and a combustion exhaust gas discharge pipe 15A, 1
Between the cyclones 20A, 20B connected to 5B and the four-way switching valve 17, regenerative heat exchangers 16A, 16
B is connected. 5 is a steam pipe. The steam pipe 5 converts water to superheated steam by itself, but the steam pipe and the superheated steam pipe may be separated. 12 is a flame.

As shown in FIG. 3, the regenerative heat exchangers 16A and 16B have, on the downstream side, one end of the combustion air supply pipe / combustion exhaust gas discharge pipe 15b and the upstream side of the combustion air supply pipe / combustion exhaust gas discharge pipe 15A. Combustion air supply pipe and flue gas discharge pipe 15
c is connected to one end. A heat storage body 16b made of honeycomb ceramics is provided in the middle of the cylindrical body 16a. The material of the ceramics, the low thermal expansion coefficient and thermal shock resistance of the points in cordierite _{(2MgO · 2Al 2 O 3 ·} 5Si
O ₂ ) is preferred. Combustion air 11 and flue gas 13
The heat storage elements 16b are periodically switched and sent alternately. The specific heat of ceramics is
Since the specific heat of the metal is about 0.1 KCL / Kg ° C., while the specific heat is about 0.2 KCL / Kg ° C., the heat capacity is large.
Since the honeycomb-shaped ceramics have high heat resistance, the temperature of the regenerative heat exchangers 16A and 16B can be increased, and the porosity and the surface area are large, so that heat exchange efficiency is high. Further, a high temperature gradient can be obtained between the low temperature side and the high temperature side.

As shown in FIG. 1, the four-way switching valve 17 has one end connected to a pair of regenerative heat exchangers 16A and 16B, the other end of a combustion air supply pipe and combustion exhaust gas discharge pipe 15c, and a combustion air supply pipe. Also connected to one end of a combustion exhaust gas discharge pipe 15d. The combustion air heated through the regenerative heat exchanger 16A is sent to one burner 3a by periodically switching the four-way switching valve 17, and the burner inner cylinder 3
B, the pulverized coal 19 is sent together with the carrier air to be burned, and the flue gas 13 flowing back through the other burner 3b
To the regenerative heat exchanger 16B
Is heated and heat recovery by rapid cooling of the combustion exhaust gas 13 is performed, and these are alternately performed by one burner 3a and the other burner 3b. The arrow 1 shown by a solid line
Numeral 1 indicates combustion air sent to the burner 3a, and an arrow 11 indicated by a dashed line indicates that the four-way switching valve 17 is switched to burner 3b.
Shows the combustion air sent to Arrow 1 shown by a solid line
Numeral 3 indicates the combustion exhaust gas discharged by flowing back through the burner 3b, and the arrow 13 indicated by a dashed line indicates the combustion exhaust gas discharged by switching the four-way switching valve 17 and flowing back through the burner 3a.

The cyclones 20A and 20B remove fly ash 21 contained in the flue gas 13 and the fly ash 21 is treated by ash treatment equipment (not shown) provided on the downstream side. The cyclones 20A and 20B are provided with pulverized coal burners 3a and 3b on the downstream side.
One end of a combustion air supply pipe / combustion exhaust gas discharge pipe 15a connected to the air supply pipe, and a combustion air supply pipe / combustion exhaust gas discharge pipe 1 on the upstream side.
5b, respectively.

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 1A and the combustion air 11 supplied into the combustion furnace 1A are separated into a high temperature portion and a low temperature Since the heat exchange is performed through the heat exchanger 16 having the heat storage body 16b made of a honeycomb-shaped ceramic having a very large temperature gradient at the portion, the combustion air 11 is heated to 800 ° C.
The temperature can be increased to １，1,000 ° C. and supplied to the combustion furnace 1A. Therefore, the combustion reaction of the pulverized coal 19 is promoted by the high-temperature combustion air 11, so that the burn-out time can be shortened and 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. Since the exhaust heat of the high-temperature combustion exhaust gas 13 can be rapidly cooled to 200 ° C. or less by the heat exchanger 16 having the ceramic heat storage element 6b, the entire apparatus can be made compact by eliminating heat recovery equipment such as an economizer and an air preheater. Can be achieved. Furthermore, since fly ash 21 is removed by cyclones 20A and 20B provided on the upstream side of heat exchanger 16, fly ash 21 does not reach heat exchangers 16A and 16B, and fly ash 21 adheres to heat exchangers 16A and 16B. It does not cause blockage.

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. Of course, various changes can be made without departing from the spirit of the present invention. .

[0021]

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, since the regenerative heat exchanger can rapidly cool the exhaust heat of the high-temperature combustion exhaust gas to recover the heat, it is possible to reduce the size of the entire apparatus by eliminating equipment such as an economizer and an air preheater. Further, since fly ash is removed by the cyclone, an excellent effect is obtained such that the heat exchanger is not blocked due to the fly ash being attached.

[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 pulverized coal burner.

FIG. 3 is an enlarged sectional view of a regenerative heat exchanger.

FIG. 4 is a conceptual diagram of a conventional pulverized coal-fired boiler.

[Explanation of symbols]

 1, 1A Combustion furnace 1a Furnace wall 2 Combustion chamber 3, 3a, 3b Burner 3A Combustion air path / combustion exhaust gas discharge path 3B Burner inner cylinder 4 Combustion air supply pipe 4a, 14A, 14B Pulverized coal supply pipe 11 Combustion air 13 Combustion exhaust gas 15A, 15B Combustion air supply pipe and combustion exhaust gas discharge pipe 16A, 16B 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 20 Cyclone 21 Fly ash 22 Motor

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 3K023 QA02 QA04 QB02 QB09 QB13 QB17 QB21 QC05 QC07 SA01 3K065 QB03 QB13 QB15 QC03 3K070 DA09 DA29 DA49 DA76

Claims (1)

[Claims] At least one pair of burners provided with a combustion air passage and a combustion exhaust gas discharge passage so as to surround a burner inner cylinder is arranged on a furnace wall of a combustion furnace, and a pulverized coal supply pipe is connected to the burner inner cylinder. At the same time, one end of a combustion air supply pipe and a combustion exhaust gas discharge pipe is connected to the combustion air path and the combustion exhaust gas discharge path, and a four-way switching valve is connected to the other end of the combustion air supply pipe and the combustion exhaust gas discharge pipe. , A cyclone and a heat exchanger having a honeycomb-shaped ceramic regenerator are connected in the middle of the combustion air supply pipe and the combustion exhaust gas discharge pipe connecting the burner and the four-way switching valve, respectively. By switching, while sending the combustion air heated through the heat exchanger to one burner, pulverized coal is sent from the burner inner cylinder and burned, and the combustion exhaust gas flowing back through the other burner is passed through the cyclone. The heat is sent to the heat exchanger to heat the heat exchanger and cool the flue gas.The fly ash contained in the flue gas is removed by a cyclone, and these are alternately performed by one burner and the other burner. A pulverized coal combustion device characterized in that: