JPS59180204A - Pulverized coal burning device for reducing nox - Google Patents

Abstract

PURPOSE:To effectively perform the vapor phase reduction of NOx by disposing a classifier between a coal crusher and a burner to re-classify the crushed coal, and injecting the crushed coal separately from the burner to form a main combustion flame and a reducing flame. CONSTITUTION:Coals 5 are supplied dropwise to the crusher 3 through a coal feeder 6. In this crusher 3, the coals are crushed and supplied from the crusher 3 to the classifier 8 through a slack coal pipeline 7 by air A supplied by a fan 2. In the classifier 8, the coals are classified in the classifier 8. Coals having a particle diameter less than a predetermined particle diameter, are supplied as a main fuel to a burner 9 through a main fuel pipeline 10 by air A. On the other hand, coarse particle coals discharged through a feeder 11 are supplied as an auxiliary fuel through an auxiliary pipeline 13 to the burner 9 by an exhaust gas EG supplied through an exhaust gas pipeline 25. The main fuel is injected within the furnace from an injection port 16 of a main fuel pipe 14. On the other hand, the auxiliary fuel consisting of coarse particle coals, which has reached an auxiliary fuel pipe 17, is injected into the furnace through an injection port 18.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pulverized coal combustion device, and more particularly to a combustion device capable of reducing nitrogen oxide emissions.

Most large-scale boilers for businesses, including large-scale boilers for power plants, that use coal as fuel use powdered coal that has been pulverized to a specified particle size (hereinafter referred to as "pulverized coal"). . By using this pulverized coal, the surface area per unit amount of coal is increased, and the combustibility is greatly improved, and controllability is also improved accordingly.

On the other hand, even in boilers that use such pulverized coal as fuel, the requirement to reduce nitrogen oxides (NOx) is the same as in other combustion devices, and various low NOx combustion methods have been implemented. In the case of coal combustion, the amount of N contained in the fuel is lower than that of oil.
There is a lot of so-called fuel NOx, and the current switching to coal as fuel is actually making the NOx problem even more serious.

NOx removal suppresses and controls the generation of NOx during the combustion stage,
There is a low NOx combustion method that removes the generated NOx, and a method that removes the generated 11Ox from the exhaust gas using a denitrification device. Among these, there is a gas phase reduction method as one of the low NOx combustion methods. This method performs combustion by dividing the air ratio (the ratio of the amount of air actually supplied to the theoretical amount of air), and performs combustion at an air ratio of approximately 1 to offset the heat load on the combustion device. By keeping the ratio low (usually 0°6 or less), intermediate products with reducing properties such as ・OH, ,00, ・H are generated, and NOx generated by these products is reduced in the gas phase and rendered harmless. N2.

In the gas phase reduction method described above, the production of intermediate products is N
It is necessary to generate the intermediate product at the same time as the generation of Ox or after the generation of NOx, and there is almost no point in generating intermediate products spatially upstream of the generation of NOx before the generation of NoX. In other words, most intermediate products, especially radicals, have a duration of less than 1 second, and if no intermediate products exist in the combustion zone where NOx is generated, gas phase reduction will hardly occur. This is because you can't expect much.

This invention was constructed in view of the above-mentioned problems,
An object of the present invention is to provide a pulverized coal combustion device that can effectively perform gas phase reduction.

In short, this invention places a classifier between a coal crusher and a burner, classifies the crushed coal supplied from the coal crusher again, and injects each of the classified coals separately from the burner to reduce the main combustion flame and This combustion device is configured to form a flame and effectively perform gas phase reduction of NOx.

This invention will be explained in detail below.

In FIG. 1, pulverized coal pipe 7 is connected to coal crusher 3
A classifier 8 is placed in the cyclone via the cyclone. A main fuel pipe 10 supplies pulverized coal classified by a classifier 8 to a burner 9. On the other hand, an auxiliary fuel pipe IE is connected to the lower part of the classifier 8 via a rotary feeder 11, and a classified coarse coal supply pipe 26 is an air supply pipe for supplying air A to this exhaust gas supply pipe 25. It is a supply pipeline.

In FIG. 2, the fuel line 10 is connected to the main fuel line 14 of the burner, while the auxiliary fuel line 13 is connected to the auxiliary fuel line 17 of the burner. 16 is a main injection port formed in an annular shape, 18 is a sub injection port located at the center of the main injection port 16, 19
is a wind box, 20 is a swirling blade, 21 is a swirling room,
22 is an air injection port.

Next, the operating state of this device will be explained.

In FIG. 1, coal 5 in a hopper 4 is dropped and supplied to a crushing device 3 via a coal feeder 6.

In this pulverizer, coal is pulverized and passed through a pulverized coal pipe 7 to the pulverizer 3 by air A supplied by a fan 2.
is supplied to the classifier 8 from

In this case, a classifier may be disposed within the pulverizer 7 to primarily classify the pulverized coal.

Classification! The powdered charcoal that has reached A8 is classified here,
Coal having a predetermined particle size or less is supplied to the burner 9 via the main fuel pipe 10 using air A as the main fuel. On the other hand, the coarse coal discharged from the feeder 11 is supplied to the burner 9 through the auxiliary fuel pipe 13 as an auxiliary fuel by means of the exhaust gas supplied through the exhaust gas pipe 25.

In this case, the exhaust gas E(j) may be mixed with air A through the pipe 26 to control the combustion of the auxiliary fuel.

The main fuel that has reached the burner is injected into the furnace from the injection port 16 of the main fuel pipe 14, and is given a swirling force by the air used for air flow transport (minus air) and the swirling vane 20, and is injected from the air injection port 22. The secondary air forms the main combustion flame. On the other hand, the coarse auxiliary fuel that has reached the auxiliary fuel pipe 17 is only exhaust gas.
Alternatively, a mixture of exhaust gas and air is injected into the furnace from the injection port 18. In the case of secondary fuel, the gas for airflow transport is exhaust gas (other inert gases may also be used) or a mixture thereof, and the secondary air is blocked by the main combustion flame, so it burns at a low air ratio and has low reducing properties. produce an intermediate product with Further, since the secondary fuel has a large particle size, its combustion rate is slow, and the intermediate product is produced after NOx is formed in the main combustion flame, so that NOx can be effectively reduced in the gas phase. The combustion rate of the auxiliary fuel can be controlled by adjusting the amount of air mixed with the exhaust gas, and it can also be controlled so that intermediate products can be produced at a time when gas phase reduction is effective.

According to this invention, pulverized coal can be divided into fine powder and coarse particles, and by burning each pulverized coal separately, it is possible to generate a specific intermediate product that is most easily subjected to gas phase reduction, thereby reducing nitrogen oxides. can be effectively reduced in the gas phase.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of the device according to the present invention, and FIG.
The figure is a sectional view of the burner of FIG. 1.

Claims (1)

[Claims] 1. In a device in which coal is pulverized by a pulverizer and then transported by pneumatic flow to a burner for combustion, a classifier is disposed in a pipe for pneumatically transporting the pulverized coal to the burner, and the classifier and burner are connected together. are connected by a main fuel pipe and an auxiliary fuel pipe, each classified fuel is separately transported and combusted by airflow to a burner, and NOx is reduced in the gas phase by intermediate products in the auxiliary fuel flame. A pulverized coal combustion device that reduces NOx. 2. Pulverized coal combustion for reducing NOx as set forth in claim 1, characterized in that a pipe line for supplying inert gas such as exhaust gas as air flow transport gas is connected to the auxiliary fuel supply pipe line. Device. 3. Combustion is controlled by connecting an air supply pipe to the inert gas supply pipe and adjusting the amount of air mixed. A pulverized coal combustion device that reduces NOx as described above.