JPS59195017A - Pulverized coal combustion device - Google Patents

Abstract

PURPOSE:To reduce production of NOX during combustion of pulverized coal, by a method wherein, in response to a detecting signal from a volatile content detecting means, an amount of the air for combustion fed to the air system of a denitrating burner is controlled to less than the amount of the air for theoretical combustion of a volatile content. CONSTITUTION:A volatile content in coal fed to a denitrating burner 4 is detected by a volatile content detector 17, a volatile content detecting signal 18, provided by the volatile content detector 17, is transmitted to a controller 19, and by means of a control signal 21 from the controller 19, dampers 15 and 20 are opened and closed. Or in case pulverized coal to the denitrating burner 4 is low fuel ratio coal, the volatile content detecting signal 18 by the volatile content detector 17 is increased, whereby the dampers 15 and 20 are throttled so that a ratio of the air to the volatile content becomes below 0.5, and in case pulverized coal is high fuel ratio coal, the dampers 15 and 20 are throttled so that the ratio of the air becomes below 0.5. This causes reduction in production of NOX during combustion of pulverized coal.

Description

[Detailed Description of the Invention] Unexploded B11 relates to a pulverized coal combustion device, and particularly relates to a pulverized coal combustion device suitable for reducing nitride oxides (hereinafter referred to as NOx) generated during combustion of pulverized coal. .

Fossil fuels contain N in addition to fuel components such as C and I, and in particular, pulverized coal has a higher amount of N than gaseous fuels and liquid fuels (C).

For this reason, the amount of NOx generated during combustion of pulverized coal is greater than the amount of NOx generated during combustion of gaseous oxygen and liquid fuel, and therefore it is desired to reduce NOx as much as possible.

NOx generated during the combustion of various fuels is thermal (Th
(ermal) No X and Fuel (Fuel) N
Thermal NOx is generated when nitrogen in the combustion air is oxidized by oxygen.
-10,000, Fuel NOx is generated by the oxidation of N in the fuel.

Combustion methods that suppress the generation of these NOAs include a multistage combustion method in which combustion air is divided into multiple stages and supplied, and an exhaust gas recirculation combustion method in which low-oxygen swirling combustion exhaust gas is mixed into the combustion area. There is.

These low NOx combustion methods are based not on lowering the temperature of the combustion flame through low-oxygen smoldering, but rather on suppressing the reaction between the oxidizer and oxygen. However, between thermal NOx and fuel NOx, the generation of thermal NOx can be suppressed by lowering the combustion temperature, while fuel NOx can be suppressed by lowering the combustion temperature.
Ox generation has little dependence on combustion temperature. Therefore, conventional combustion methods aimed at lowering flame temperature are effective for combustion of gaseous and liquid fuels with low N content. However, it has little effect on the combustion of pulverized coal fuel, in which nearly 80% of the generated NOx is fuel NOx.

In addition, there is an in-furnace denitrification combustion method that is an extension of these multistage combustion methods and exhaust gas recirculation combustion, but this in-furnace denitrification combustion method creates a reducing atmosphere in the furnace and This is a combustion method that reduces generated NOx using reducing substances from a denitrification burner, and has been put into practical use for liquid fuels.

However, even if this in-furnace denitrification combustion method is applied to the combustion of pulverized coal fuel, there is no obvious difference from the conventional combustion method.

For example, volatile content 50%, fixed carbon content 40%, ash content 10%
When combusting pulverized coal using the in-furnace denitrification combustion method, even if the air ratio to the denitrification burner is reduced, the residual air ratio remains the theoretical combustion air amount for the eight components of the pulverized coal, and for this reason, the denitrification It is not possible to significantly reduce NOx without fulfilling its role as a burner.

The present invention attempts to eliminate the drawbacks of 7) Slh rice promotion, and its purpose is to obtain a pulverized coal combustion device that can reduce NOx even when pulverized coal fuel is burned. It is something.

In order to achieve the above-mentioned object, the present invention provides an i-emitting component detection means 7 for detecting volatile components in the fuel in the coal supply system to the denitrification burner, and uses a detection signal from the volatile component detection means to detect the denitrification burner. The amount of nitrogen gas for combustion into the air system is controlled to be less than the theoretical amount of air for combustion of volatile components.

Hereinafter, embodiments of the invention will be described with reference to the drawings.

v2. 1 lA shows experimental data7 conducted by the present inventors, where the vertical axis represents tNOx and the horizontal axis represents the burner average air ratio. The characteristic curve diagram shown shows the change in NOx when transitioning from normal combustion to two-stage combustion. Figure 2 is a system diagram showing this sixth embodiment.

In addition, in FIG. 2, for convenience of explanation, only the coal supply system and the air system to the denitrification nozzle are shown, and the coal supply system and the air system to the main burner are omitted.

Below, in order to provide a detailed explanation of the present invention, the differences in combustion mechanisms between liquid fuel and pulverized coal fuel will be discussed.

The combustion mechanism for liquid fuel is that all of the liquid fuel is vaporized and burned.
In contrast, the combustion mechanism of pulverized coal fuel is divided into decomposition combustion of volatile components and surface combustion of fixed carbon components, and the decomposition and combustion speed of volatile components is significantly faster than the surface combustion speed of fixed carbon components. Therefore, the reaction between the two can clearly be seen as two reactions: first, the volatile components are burned, and then, at t, the fixed carbon begins to burn.

In other words, the combustion mechanism of pulverized coal consists of the pyrolysis process of pulverized coal in which volatile components are released, the combustion process of the released volatile components, and the combustion process of combustible solid components (hereinafter referred to as char) after pyrolysis. . The burning rate of volatile components is much faster than that of solid components, and volatile components burn at the beginning of combustion. In addition, during the pyrolysis process, the N content contained in pulverized coal is
There are two types of combustible components: those that are volatilized and released like other combustible components, and those that remain in the char.

Therefore, fuel NOx generated during pulverized coal combustion is
Volatile NOx caused by the N content in the volatile components of pulverized coal and N contained in the char
It is divided into char (Char) No.
Since x is first generated when char burns, char Nox is generated until the second half of combustion, whereas volatile NoX is generated during the first half of combustion.

In other words, the volatile N component turns into compounds such as NHa and HCN in the initial stage of combustion and in the oxygen-deficient combustion region;
In addition to reacting with oxygen to become NOx, these nitrogen compounds can also act as a "reducing agent" that decomposes the generated Nox into nitrogen. This NOx reduction and secretion by nitrogen compounds is NOx
In a reaction system where NOx coexists, most of the nitrogen compound parts are oxidized with NoxK. In addition, the production of this reducing substance is more likely to occur in an atmosphere with a lower acid purple concentration.

In this way, as a NOx reduction method during pulverized coal combustion,
Since the nitrogen content in the volatile components that have a high reducing property generates reducing substances such as NH3 and HCN in the initial stage of combustion and in the combustion region where there is a lack of oxygen, it is necessary to adjust the amount of air to the denitrification burner to correspond to the volatile components of the pulverized coal. It turned out that the important point was to control the situation.

This tendency is true even if the fuel ratio (industrial analysis of coal (C″!ε) of fixed carbon mass/volatile components) is different between low-fuel coal and high-fuel coal.

The experimental data in Figure 1 shows changes in NOx (B) when normal combustion gradually shifts to two-stage combustion, and the results are for pulverized coal with different properties.

In the figure, curve A shows low fuel ratio coal with a fuel ratio of 0.8, and curves B and C show high fuel ratio coals with fuel ratios of 3.3 and 4.3.

In other words, as is clear from Figure 1, with low-twisted tornized coal (pulverized coal with a high volatile content), NOx decreases even if the burner average air ratio is slightly lowered, as shown by curve A, but with a high fuel ratio Curves B and C for charcoal (pulverized coal with low volatile components)
As shown in , it is NO unless the burner average air ratio is significantly lowered.
It shows that x is not bad.

This is thought to be due to the amount of volatile components in the pulverized coal.In the case of low-fuel coal, there are many volatile components, so even if the burner average air ratio is slightly lowered, the air ratio to volatile components decreases. In the case of high-fuel coal, the two-stage combustion effect becomes thicker and NOx is reduced, or in the case of high-fuel coal, the second-stage combustion effect is small and NO
x also showed a tendency not to decrease much, and even with high fuel ratio coal, it is clear that NOx can be reduced by controlling the amount of air to the denitrification burner ((2, In Fig. 2, 1 is a boiler furnace, 2 is a wind box, 3 is a main burner, 4 is a denitrification burner, and 5 is an after air port.The inside of the wind box 2 is divided into stages of a main burner 3, a denitrification burner 4, and an after air port 5. The amount of air can be controlled for each stage 5. The coal supply system 6 to the denitrification burner 4 is such that the coal is supplied from the raw coal bunker 7 to the mill 9 via the coal feeder 8, and is pulverized into pulverized coal and sent to the fuel pipe 10. The denitrification burner 4 is supplied with the denitrification burner 4.

On the other hand, the combustion air for the denitrification burner 4 is supplied to the air system 14 through the air duct 11, 12 for preheated air and cold air, and the exhaust gas duct 13 for the combustion air to be supplied to the denitrification burner 4. The pulverized coal is sent to the mill 9, and then supplied to the denitrification burner 4 through the fuel pipe 10.

17 is a volatile component detector for detecting the volatile components of coal supplied to the denitrification burner 4; 18 is a one-shot component detection signal; 19
is the controller, 20 is the damper that controls the secondary air starvation period 1, and 2
1 is a control signal for controlling Dannogu15.207.

In such illegal production, first, the volatile component detector 17 detects the Id emitting components in the coal supplied to the denitrification burner 4,
The volatile component detection signal 18 obtained by the volatile ash extractor 17 is transmitted to the controller 19, and the dampers 15 and 20 are closed by the control signal 21 of the controller 19 and the denitrification burner 4 is closed. The total amount of primary air and secondary air is changed depending on the volatile components in the pulverized coal supplied to the pulverized coal.

It is preferable that the dampers 15 and 20 are controlled by the '6;: control signal 21 so that the air ratio of the denitrification burner 4 is 05 or less as the air ratio to volatile components.

In other words, if the pulverized coal supplied to the denitrification burner 4 is low-burning coal, the volatile component detection signal 18 at the volatile component detector 17
Since the ratio of air to volatile components becomes 0.5 or less, reduce the damper 15°20 and use the denitrification burner.
When the pulverized coal to 1 is a high fuel ratio coal, the volatile components are small (k), so Danno or 15 r 20 is squeezed so that the air ratio to the volatile components is 0.5 or less.

In addition, in the case of high fuel ratio coal, since there are few volatile components ((,
When the ratio of coal to the volatile wall is 70.5 or less, the coal becomes slightly different from the wall. 112 can be sent] [In order to achieve this, 13 exhaust gas ducts will be sent and a pack amplifier will be sent.

In this way, by controlling the air needle according to the volatile components in the pulverized coal, denitrification combustion can be performed regardless of the low-flame carbonized coal. 'Mr.NOx
Can you even measure the change?

[Brief explanation of the drawing]

The first section shows NQA in the vertical direction, the horizontal axis shows the average air ratio of the burner, and the second chart shows an example of the present invention. This is a simplified genealogy diagram. 3... Main burner, 4... Denitrification burner, 6... Coal supply system set, 14... All systems, 17... Emission component detector, 18... Volatile component detection signal , 19...Controller, 15°20...Gunpa, 21...Control signal.

Claims (1)

[Claims] A coal supply system that supplies coal to the main burner and the denitrification burner, and an air system that supplies hot air for combustion are provided, and NOx in the main burner is denitrified and combusted with reducing substances from the denitrification burner. A volatile component detection means for detecting volatile components in the fuel is provided in the coal supply system, and the amount of combustion air supplied to the air system of the denitrification burner is controlled to be less than or equal to the theoretical combustion air amount of volatile components based on the detection signal of the volatile component detection means. The pulverized coal combustion equipment is characterized by the fact that it is controlled in a controlled manner.