JPH0443688Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention is an improvement of a three-stage pulverized coal combustion device equipped with a primary burner for burning a primary fuel made of pulverized coal and a secondary burner for _NOx reduction. Regarding.

Prior art and its problems In the conventional three-stage pulverized coal combustion apparatus, as shown in FIG. The fuel was supplied as pneumatic air, and the remainder was supplied to the secondary fuel nozzle 54 through a branch pipe in the middle of the piping.

However, when using a combustion device with this structure, when using coal that has a relatively high fuel ratio and poor ignitability, or coal that has a high nitrogen content and easily generates _NO There was a problem in that the combustion efficiency decreased due to an increase in the amount of carbon dioxide, and the effect of suppressing _NOx generation was not sufficiently exerted.

In view of the above-mentioned circumstances, the purpose of this invention is to provide a three-stage pulverized coal combustion device that can significantly improve combustion efficiency and efficiently suppress the generation of _NOx .

Means for Solving Problems The three-stage pulverized coal combustion device according to this invention consists of a primary burner 3 for primary fuel combustion and a secondary burner 4 for _NOx reduction, as shown in the attached Figures 1 and 2.
In this three-stage pulverized coal combustion apparatus, a pulverized coal swirling chamber 11 is provided at the downstream end of the primary fuel supply cylinder 9 of the primary burner 3, and an inlet 5 provided tangentially to the chamber 11 is provided with a centrifugal force adjustment chamber 11. A fine particle extraction pipe 13 and a coarse particle extraction pipe 14 are provided in the central part 11a and the peripheral part 11b of the pulverized coal swirling chamber 11, respectively.
Dampers 15 and 1 for flow rate adjustment are installed at 3 and 14, respectively.
6 is installed internally, and these extraction pipes 13 and 14 are joined at each trailing end and connected to a secondary fuel supply pipe 21 to the secondary burner 4.

Three-stage pulverized coal combustion involves burning primary fuel with excess air in a high-temperature oxidizing atmosphere to form a primary combustion zone, and supplying secondary fuel to the downstream side of the zone to create a reducing atmosphere using the excess air. The secondary fuel is combusted to form a secondary combustion zone, and further air is supplied to the downstream side of the zone to slowly burn the unburned content of the secondary fuel in a low-temperature oxidizing atmosphere to form a tertiary combustion zone. be. According to this combustion method, _NOx generated in the primary combustion zone is quickly reduced in the secondary combustion zone.

Embodiment Next, an embodiment of this invention will be specifically described based on the drawings.

In Figures 1 and 2, the three-stage pulverized coal combustion device according to this invention supplies pulverized coal obtained by pulverizing coal in a mill 1 as a primary fuel to the primary burner 3 of a furnace 2 using pneumatic air. However, secondary air is supplied to the burner 3, and a portion of pulverized coal is supplied from the downstream end of the primary burner 3 to the secondary burner 4 as secondary fuel.

The primary burner 3 includes an ignition oil burner cylinder 7 located at the shaft center.
, an oil burner air supply cylinder 8 on the outside, a primary fuel supply cylinder 9 on the outside, and a secondary air supply cylinder 10 on the outside are arranged concentrically. . And the primary burner 3 of this configuration
is provided on the front wall 6 of the furnace 2 facing inward.

A pulverized coal swirling chamber 11 having a larger diameter than that of the primary fuel supply tube 9 is provided at the downstream end of the primary fuel supply tube 9, and an inlet 5 is provided in the tangential direction at the bottom of the chamber 11, and the inlet 5 is provided with a centrifugal force. A guide vane 12 whose angle can be changed for adjustment is installed inside. Further, in the pulverized coal swirling chamber 11, a fine particle extraction pipe 13 and a coarse particle extraction pipe 14 are provided in the central part 11a and the peripheral part 11b, respectively, and dampers 15 and 16 for adjusting the flow rate are installed in these extraction pipes 13 and 14, respectively. has been done. These extraction pipes 13 and 14 are joined at each trailing end and connected to a secondary fuel supply pipe 21 to the secondary burner 4. Between the swirling chamber 11 and the primary fuel supply cylinder 9, a tapered cone-shaped restrictor 17 for rectification is provided.

A wind box 18 is provided at the downstream end of the secondary air supply cylinder 10, and swirl vanes 19,
20 are provided.

In the combustion apparatus having the above configuration, the pulverized coal sent from the mill 1 to the swirling chamber 11 by pneumatic air is transported by guide vanes 12 that are inclined at a predetermined angle with respect to the flow direction of the pulverized coal.
is guided in the rotation direction into the rotation chamber 11 and rotated within the same chamber 11. As a result of the swirling of the pulverized coal, coarse grains with a large particle size among the supplied pulverized coal are moved to the peripheral part 11b of the swirling chamber 11 due to the centrifugal force.
On the other hand, small particles are collected in the swirling chamber 1.
1 at the center 11a. Then, the fine particles and coarse particles are extracted from the swirling chamber 11 by extraction pipes 13 and 14, respectively, and after being adjusted to a required flow rate by dampers 15 and 16, they are introduced into the secondary fuel supply pipe 14 where they are mixed. Ru. The mixed pulverized coal obtained by mixing fine particles and coarse particles in the required ratio is then passed through the supply pipe 21 as a secondary fuel to the secondary nozzle 4.
and is supplied to the secondary combustion zone in the furnace 2.

The mixing ratio of fine particles and coarse particles is adjusted by dampers 15 and 16 of extraction pipes 13 and 14, respectively. For example, coal has a relatively high fuel ratio and has poor ignitability,
When using coal that has a high nitrogen content and easily generates _NO
4 damper 16 is slightly opened or closed. As a result, the secondary fuel made of mixed pulverized coal has a small particle size. Therefore, combustion of the secondary fuel can be quickly completed in the secondary combustion zone formed in the furnace 2, suppressing a decrease in combustion efficiency and an increase in unburned matter after combustion, and reducing reducing substances. By increasing the amount of NOx generated in the primary combustion zone, it is possible to efficiently reduce _NOx generated in the primary combustion zone.

Test Next, a test (Test 1) was conducted to determine the relationship between the combustion load and the amount of unburned matter contained in the ash and the amount _{of NO} A test (Test 2) was conducted to determine the relationship between the amount and unburned content.

Test 1 In this test, the coal type was Optimum coal, the combustion amount was 2t/h, the total air ratio was 1.25, the primary air ratio was 0.65,
The secondary fuel ratio was set at 30%. In addition, under the same conditions as these, tests were also conducted using the conventional technology described at the beginning of this paper. The results of this test are shown in FIG. As is clear from the figure, this invention has less ignition loss (that is, lower unburned content in the ash) than the conventional technology.
The amount of NO _X generated has been reduced (especially under load ₎
(was reduced by more than 10% compared to conventional technology).

Test 2 In this test, A coal, B coal, and C coal were used as coal types, the combustion amount was 2t/h, and the total air ratio was
1.25, the primary air ratio was 0.65, and the secondary fuel ratio was 30%. In addition, under the same conditions as these, tests were also conducted using the conventional technology described at the beginning of this paper. The results of this test are shown in FIG. As is clear from the figure,
In the case of this invention, the ignition loss was lower (that is, the unburned content in the ash was lower) and the combustion efficiency was improved, compared to the case of the conventional technology, regardless of the type of coal.

Effects of the invention According to the three-stage pulverized coal combustion device of this invention, pulverized coal is divided into fine particles and coarse particles by centrifugal force in the swirling chamber 11, and these are extracted from the swirling chamber 11 separately. The flow rate of grains is damped by damper 15,1.
6 to mix these in the required ratio, and the mixed pulverized coal can be supplied in the secondary combustion zone.
Therefore, by adjusting the mixing ratio of fine particles and coarse particles, fine particles with a small particle size among pulverized coal can be supplied to the secondary combustion zone where a large amount of unburned coal is generated. Combustion efficiency can be significantly improved compared to the conventional technology described in .

In addition, in the secondary combustion zone, as a result of supplying a large amount of pulverized coal with a small particle size, the thermal decomposition rate and combustion rate of the pulverized coal are accelerated, a strong reducing atmosphere is formed, and the generation of _NOx is efficiently suppressed. .

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of the main parts of a three-stage pulverized coal combustion device showing an embodiment of this invention, Figure 2 is a cross-sectional view taken along the - line in Figure 1, and Figure 3 is the result of Test 1. Combustion load and ignition loss indicating
_FIG . 4 is a graph of the relationship between fuel ratio and ignition loss showing the results of Test 2, and FIG. 5 is a cross-sectional view equivalent to FIG. 1 showing the prior art. 3...Primary burner, 4...Secondary burner, 5...
Inlet, 9...Primary fuel supply cylinder, 11...Pulverized coal swirling chamber, 11a...center, 11b...periphery, 1
2... Guide vane, 13... Fine particle extraction pipe, 14
... Coarse particle extraction pipe, 15, 16 ... Damper, 2
1...Secondary fuel supply pipe.

Claims (1)

[Scope of utility model registration request] In a pulverized coal three-stage combustion device equipped with a primary burner 3 for primary fuel combustion and a secondary burner 4 for _NO A guide vane 12 for centrifugal force adjustment is installed in an inlet 5 provided tangentially to the same chamber 11, and a fine particle extraction pipe 13 and a coarse particle extraction tube are provided in the central part 11a and peripheral part 11b of the pulverized coal swirling chamber 11, respectively. Dampers 15 and 16 for flow rate adjustment are installed in these extraction pipes 13 and 14, respectively, and these extraction pipes 13 and 14 are joined at each trailing end to form a secondary burner 4. A three-stage pulverized coal combustion device, characterized in that it is connected to a secondary fuel supply pipe 21 to the pulverized coal.