JPH031564B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a pulverized coal-fired low NO _x combustion device.

(Prior Art) Conventionally, in an industrial furnace 1 such as a boiler furnace as shown in FIG. 1, a first main burner 2 and a second main burner 3 are installed at the lower part of the outer periphery, and pulverized coal is supplied to each of them. By communicating the pipe 4 and the air supply pipe 5, a pulverized coal supply port 6 and an air supply port 7 are provided to burn the pulverized coal. Since the combustion gas is based on oxygen-excess combustion, there are
A denitrification burner 9 is installed above the overfire air supply port 8, and a denitrification burner 9 is installed above the overfire air supply port 8 to treat _NOx in the furnace before discharging _it outside the furnace. An after-air supply port 10 is disposed above the air conditioner 9 to cope with the problem.

As shown in FIG. 2, this denitrification burner 9 is connected to a pulverized coal supply pipe 4 and an air supply pipe 5, each of which is provided with a pulverized coal supply port 6 and an air supply port 7. By introducing air into the furnace at a ratio below the required air amount (equivalent) for combustion and reacting it with the combustion gas generated in the main burner combustion zone a shown in Figure 1 as unburned fuel, unburned fuel is produced. The following reaction is obtained in the existing reduction zone b.

NO + HC ^* → N・R ... () Here, NO is what rises from the main burner combustion area a. HC ^* is activated hydrocarbon and is generated by incomplete combustion in the denitrification burner 9. N.R.
For example, refers to nitrogen compounds such as HCN or _NH3 .

At the stage after the above-mentioned N.R is generated, it is oxidized by the air supplied from the after-air supply port 10, and in the combustion completion zone c, the following reaction is first obtained.

N・R+O ₂ →NO ……() Furthermore, due to the reaction between N・R and NO in the above equation, NO disappears as shown in N・R+NO→N ₂ …(), and as much NO as possible is removed from the furnace. is prevented from being emitted.

However, the conventional denitrification burner 9, as shown in FIG. This is the so-called in-furnace combustion method, in which combustion does not take place inside the furnace, but instead takes place inside the furnace.

Therefore, according to this in-furnace combustion method,
In the denitrification fuel combustion zone 11, a relatively low-temperature flame with heat dissipation is formed, so the combustion does not become active and the supplied air is not completely consumed. This results in a relatively large amount of O ₂ remaining in the fuel-existing reduction zone b.

As a result of the above-mentioned large amount of O ₂ remaining, the reduction zone b where unburned fuel should be a reducing atmosphere for denitrification becomes an oxidizing atmosphere with poor denitrification ability, and as a result, the amount of activated hydrocarbon HC ^* generated is small. Therefore, the reaction of formula () does not proceed, and the denitrification effect becomes insufficient.

This is not only due to the fact that the unburned fuel existing reduction zone b is an oxidizing atmosphere, but also because the reduction zone b is compressed by the expansion of the denitrified fuel combustion zone 11 and presents a narrow combustion zone. .

In addition, as mentioned above, since sufficient combustion is not performed in the denitrification fuel combustion zone 11, a lot of coal particles (coal grains) are generated due to unburned remains. Even when it is burned and gasified in the existing reduction zone b, O ₂
In the low-concentration and low-temperature atmosphere described above, gasification cannot be performed effectively, and therefore, even if you try to achieve complete combustion by supplying afterair in the next step, However, since complete gasification was not achieved, complete combustion was not achieved, resulting in a large amount of char being discharged directly from the furnace.

Furthermore, since pulverized coal usually contains about 10% to 20% ash, it is necessary to smoothly discharge this ash to prevent damage to industrial furnaces.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and is a pulverized coal-fired low _{NO x} aims to provide combustion equipment.

(Structure of the Invention) In order to achieve the above object, in this invention, a coal partial combustion furnace is protruded from the outer periphery corresponding to between the main burner and the after air supply port of the industrial furnace, and the coal partial combustion furnace is provided with a coal partial combustion furnace. A partial combustion chamber is formed inside which communicates with the inside of the industrial furnace via a gas inlet,
In addition, the denitrification burner communicating with the partial combustion chamber is installed at the protruding outer end of the coal partial combustion furnace, and a buttful is provided in the middle of the coal partial combustion furnace to hold back the molten ash, and upstream of this buttful, the molten ash is collected from the coal. A take-out hole is provided to take out the part-combustion furnace, and the air supply port of the denitrification burner is connected to the air supply port of the denitrification burner, which is set at 50 to 50% of the theoretical air amount required for combustion, which is set for the amount of pulverized coal supplied per unit time.
It was set so that 80% of the air amount was supplied per unit time.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 3 shows an example of this, and the components not shown are constructed in the same way as the conventional type shown in FIG. and the after air supply port 10, and the industrial furnace 1 is provided at the base end thereof.
A gas inlet 13 is formed to communicate with the denitrification burner 9, and a denitrification burner 9 is provided at the protruding outer end. The coal partial combustion furnace 12 configured as this outside combustion method is made of a fireproof and insulating material,
It is provided in an inclined shape so that the gas inlet 13 side is at the bottom.

Inside this coal partial combustion furnace 12, a denitrification burner 9 is installed.
A partial combustion chamber 14 is formed between the coal partial combustion furnace 12 and the gas inlet 13, and in this case, the coal partial combustion furnace 12 melts the generated ash with a gas flow swirling at high temperature. It is said to be a cyclone method that does not entrain ash into the combustion gas.

Here, the air ratio of the air from the air supply port 7 of the denitrification burner 9 to the pulverized coal is set as follows. In other words, if the amount of air supply required to completely burn pulverized coal supplied per unit time is the theoretical amount of air required for combustion (equivalent amount), then the amount of air supplied/the amount of air required for theoretical combustion, that is, the air The ratio is set at 0.5 to 0.8.

If the air ratio exceeds the upper limit of 0.8, there is almost no generation of activated hydrocarbons, which are most effective for decomposing _NO do not have.

Reference numeral 20 denotes a buffer, which is provided in the middle of the coal partial combustion furnace 12 to dam the melted coal in the pulverized coal. Reference numeral 21 denotes a take-out hole, which is provided upstream of the baffle 20 to transfer the molten ash to the coal partial combustion furnace 1.
This is extracted from 2.

In the above configuration, pulverized coal and air having an air ratio of 0.5 to 0.8 are supplied via the denitrification burner 9, and in this case, the coal partial combustion furnace 12 is a certain limited space, and the fireproof insulation In the partial combustion chamber 14, the denitrified fuel combustion zone 1
1 occurs as a high-temperature combustion region of around 1700℃.

Therefore, due to high-temperature combustion, ₂ minutes of O out of the predetermined amount of supplied air is completely consumed for combustion, and since the air ratio is 0.5 or more, there is no room for chirping to occur. There are also few. In this way, in the partial combustion chamber 14, most of the supplied coal is gasified in the denitrified fuel combustion zone 11 due to high-temperature incomplete combustion, and this gasified material is rapidly transferred from the gas inlet 13 into the wide furnace. Since it is ejected, it expands greatly and forms a diffused unburned fuel existing reduction zone b.

In this reduction zone b where unburned fuel exists, due to the above-mentioned high-temperature combustion, neither O ₂ nor chia exists at all, and the fuel is completely gasified (CO, H ₂ , HC ^* gas) at high temperature.

Therefore, in the reduction zone b where unburned fuel exists, O ₂
Moreover, since the air ratio is less than 0.8, it becomes an expanded area filled with activated hydrocarbons HC ^* , so it has a strong denitrification and reduction ability. NO in the rising combustion gas is efficiently decomposed by the reaction of the above formula (), and other N/R compounds are obtained as desired.

In this way, since NO is in a completely reduced form and completely gasified, it reacts as shown in the above equation () by the air supplied from the after-air supply port 10, and the resulting NO is In the combustion completion region c, as in the above formula (), the above N・R
As a result, the denitrified gas, which has been rendered harmless to _N2 , is taken out of the furnace.

Furthermore, the chir that is expected to occur to some extent in the main burner combustion zone a disappears completely with the supply of after air, and therefore there is almost no chir discharged outside the furnace as a whole. Become.

By the way, since the temperature inside the coal partial combustion furnace 12 becomes extremely high, pulverized coal usually contains 10% to 20%
% of ash is completely melted.In contrast, this invention provides a buffer 20 for damming up molten ash in the middle of the high-temperature coal partial combustion furnace 12 to dam up the molten ash. Since the extraction hole 21 is provided in the coal partial combustion furnace 12, the molten ash can be taken out of the coal partial combustion furnace 12 while the molten ash is kept at a high temperature. Therefore, ash can be smoothly discharged.

Further, if the coal partial combustion furnace 12 is of a cyclone type, the molten ash receives a strong swirling flow caused by the gas and adheres to the furnace wall surface. From this, the molten ash is allowed to adhere to the inner wall of the coal partial combustion furnace 12, and due to the so-called self-coating effect,
It may also be used as a substitute for the above refractory insulation material.

Of course, the coal partial combustion furnace 12 may not be of the cyclone type.

(Effects of the Invention) As explained above, according to the present invention, a coal partial combustion furnace is provided protruding from the outer peripheral portion corresponding to between the main burner and the after air supply port of an industrial furnace, and a coal partial combustion furnace is provided. Inside the industrial furnace,
An outside-furnace combustion method is adopted in which a partial combustion chamber is formed that communicates with the partial combustion chamber through a gas inlet, and the denitrification burner that communicates with the partial combustion chamber is installed at the protruding outer end of the coal partial combustion furnace. The air supply port of the burner was set so that an air amount of 50 to 80% of the theoretical combustion air amount set for the amount of pulverized coal supplied per unit time was supplied per unit time, so NO _x The gas in a state where most of the chir is not present is now discharged outside the industrial furnace, and this can now be achieved with a very simple structure. In addition, a buttful for damming up molten ash was installed in the middle of the coal partial combustion furnace to dam up the molten ash, and a take-out hole was provided upstream of this buttfull, so the molten ash could be removed while the molten ash was kept at a high temperature. Coal can be taken out of the partial combustion furnace, so
Ash can be smoothly discharged.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a conventional combustion device;
FIG. 2 is an enlarged view of the main part thereof, and FIG. 3 is an enlarged view of the main part showing one embodiment of the present invention. 1... Industrial furnace, 2, 3... Main burner, 6... Pulverized coal supply port, 7... Air supply port, 9... Denitration burner, 10... After air supply port, 12... Coal partial combustion furnace, 13...Gas inlet, 14...Partial combustion chamber, 20...Batsuful, 21...Takeout hole.

Claims (1)

[Claims] 1. A main burner and a denitrification burner provided with a pulverized coal supply port and an air supply port are installed on the outer periphery of an industrial furnace with the denitrification burner on top, and an after air supply port is provided above the denitrification burner. In the pulverized coal-fired low NO _x combustion equipment, a coal partial combustion furnace is provided protruding from the outer periphery corresponding to between the main burner and the after air supply port of the industrial furnace, and
A partial combustion chamber that communicates with the inside of the industrial furnace through a gas inlet is formed inside the coal partial combustion furnace, and the denitrification burner that communicates with the partial combustion chamber is provided at a protruding outer end of the coal partial combustion furnace. A buffer is installed in the middle of the coal partial combustion furnace to hold up the molten ash, an extraction hole is provided upstream of this buffer to take out the molten ash from the coal partial combustion furnace, and the air supply port of the denitrification burner is 50% or more of the theoretical required combustion air amount set for the amount of pulverized coal supplied
Pulverized coal-fired low NO _x characterized by 80% air volume being supplied per unit time
Combustion device.