JPS60223906A - Burning device - Google Patents

Abstract

PURPOSE:To control effectively generation of NOx and unburnt contents in ashes by contriving combustion by a method wherein as for an upstream side (under a state of surplus oxygen), fuel is supplied by specifying only coarse particles and as for a downstream side (under a state of oxygen starvation), the fuel is supplied by specifying only fine particles. CONSTITUTION:As for pulverized coal crushed by a mill 12, only coarse and fine particles are supplied to an upstream side burner 2 and a downstream side burner 3 respectively by a classifying device 13, an air quantity making the upstream side burner 2 into a surplus state of air is supplied to the burner 2 and the air quantity is supplied to the downstream side burner 3 so that the burner 3 is made into a starvation state of the air, through which combustion is performed within a furnace body 1 while they are being mixed with each other. In consequence of the above, along with control of generation of NOx generation of unburnt contents is controlled also and even if the unburnt contents are generated, discharge quantity itself is controlled sufficiently as a generating position is on an upstream side and sufficient dwell time for burning out unburnt contents can be taken until the unburnt contents are discharged even if the unburnt contents are generated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a combustion device in which burners are arranged in multiple stages for supplying a twisted material containing combustible solid particles and an oxygen-containing gas.

(Prior art) For example, in a pulverized coal-fired boiler, a burner is installed on the outer periphery of the furnace body, and pulverized coal and high-temperature air are supplied to the parser, mixed, and ejected into the furnace body for combustion. It's Nishide. Some of these are designed to improve the combustion capacity by, for example, having upper and lower burners all working on the outer periphery of the furnace body. The upstream side here means the upstream side with respect to the flow direction of combustion gas. For example, in a vertical boiler, the upstream burner is installed below the downstream burner.

In order to maintain Japan's strict environmental regulations, such pulverized coal-fired boilers are required to fully suppress emissions of NOx and unburned matter in the ash.

In this case, in order to reduce NOx, it is necessary to supply a relatively larger amount of air (per unit time υ) to the upstream side burner, while supplying a smaller amount of air to the downstream burner. is valid, and this fact can be seen in the patent application filed in 1867
It is described in the specification of No. 54.

As described above, it is effective to provide a difference in the amount of air supplied to the upper and lower burners in reducing NOx, but there is still another problem in reducing NOx.

In other words, in reducing NOx mentioned above, we focused only on the amount of air supplied, and regarding the pulverized coal that is supplied together with air,
It has been neglected.

Conventionally, pulverized coal has been supplied by pulverizing it in a mill and then supplying it directly to both upstream and downstream burrs.

For such pulverized coal, if all of it is pulverized into sufficiently fine particles by a mill in advance, the emissions of unburned matter in the ash can be suppressed to a very small amount; It is not preferable to refine all the materials that are used because the crushing cost will be enormous and it will require a lot of soil. Therefore, pulverization is usually carried out within the limits that are commensurate with the pulverization cost, and the pulverized materials include a mixture of finely divided materials and coarsely granulated materials.

When the pulverized coal made of these is supplied as it is to each upstream and downstream burner, the generation of N(JX) and unburned content in the ash is as follows.

First, the NOx generation concentration is as shown in Table 1.

Table 1 Comparison table of NOx generation concentration (relative ratio) Selected and supplied to the burner, each h is individually combusted in each state of excess air and insufficient air, and the resulting NOx generation concentration is compared using the St″ standard in Table 1. Here, the air ratio refers to (actual air supply amount)/(theoretical air requirement), and the expressions for air excess and air deficiency conditions, and fine and coarse particles are as follows: It is used in a relative rather than an absolute sense.

Here, in general, combustion in an air-excess state has a higher N0 value than combustion in an air-deficient state.
This means that when there is excess air and fine particles are supplied (Table 1■), the NoxQ
This is also supported by the fact that the degree was the highest compared to the others. This is thought to be due to the fact that in the case of coarse particles (o), the total surface area of all particles is large and the excessive supply of air causes rapid combustion. On the other hand, in the case of coarse grains (■), the generation of NOx is suppressed more than in the case of fine grains (■).

On the other hand, the situation changes when there is a lack of air.

In other words, when fine particles are supplied in an air-deficient condition (O), even though there is a lack of air, the fine particles react sufficiently due to their small diameter, and almost all the nitrogen needles in the fuel are N8. Therefore, the amount of NOx generated can be suppressed to a low level. On the other hand, when coarse grains are supplied in an air-deficient state (■), they are not completely burnt out, and the N content in the coarse grains remains unburned and flows downstream, resulting in the nitrogen being supplied downstream from the downstream burner. The above unburned N is determined by the empty percentage for stage combustion.
It is thought that a large amount of NOx is generated as a result of the rapid combustion of NOx in excess air.

As mentioned above, in addition to the air supply condition, the NOx generation factor is also related to the average particle size of pulverized coal. A mixture of grains and coarse grains was supplied to each of the lower burners, and combustion was performed by supplying excess air to the upstream burner and insufficient air to the downstream burner. Excess air and coarse particles (■), and on the downstream side, insufficient air and coarse particles (@) result in increased NOx generation concentration, so it is necessary to simply change the air supply amount upstream and downstream. It is thought that it is not possible to achieve 140x low sincerity effectively by doing just that.

On the other hand, the generation of unburned matter in the ash is due to the supply of coarse particles that are difficult to burn, and especially when coarse particles are supplied to the downstream side where there is insufficient air, a large amount of unburned matter is generated. This is because the supply point is on the downstream side and the residence time in the furnace until discharge is short, so the unburned content in the ash is discharged without being fully burned.

(Object of the invention) This invention was made in view of the above problem, and it
The aim is to reduce both the amount of unburned matter in the ash and the amount of unburned matter generated in the ash.

(Structure of the Invention) In order to achieve the above object, the present invention provides a furnace body such as a boiler with an upstream burner and a downstream burner, and sets the upstream burner to the downstream side with respect to the flow direction of combustion gas. located upstream of the burner, and the amount of oxygen-containing gas supplied to the upstream burner per unit time is set to be larger than the amount of oxygen-containing gas supplied to the downstream burner, And, the average particle size of the fuel containing combustible solid particles supplied to the upstream burner is set to 1.
Wow,. ,. I□. . Engineering. ,Yo,.

By setting a large value, on the upstream side (oxygen excess state), only coarse particles are specifically supplied and combusted, while on the downstream side (oxygen deficient state), only fine particles are specifically supplied and combusted. This is to simultaneously suppress the generation of NOx and unburned matter in the ash.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment, and 1 denotes a furnace body. This furnace body 1 is vertical, and an upstream burner 2 is located at the lower part of the vertical wall of the furnace body 1, and an upstream burner 2 is located at the upper part of the vertical wall. downstream burner 3
is provided. 4 is an upstream fuel supply pipe, 5 is a downstream fuel supply pipe, 6 is an upstream air supply pipe, and 7 is a downstream air supply pipe, which are connected to the corresponding upstream burner 2. It is connected to the downstream burner 3. In this case, 8 indicates an upstream fuel supply port, 9 indicates a downstream fuel supply port, 10 indicates an upstream air supply port, and 11 indicates a downstream air supply port.

Here, the upstream and downstream air supply pipes 4.5 are connected to one Mi/L/12, and the classifier 13 is disposed downstream of the Mi/'12. Only coarse grains are supplied to the upstream burner 2, and only fine grains are supplied to the downstream burner 3.

In that case, the coarse particles have an average particle diameter of 60 μm as described above, for example.
The fine particles have an average particle size of 5 μm. On the other hand, the upstream air supply port 1o has the air ratio 1 as described above.
．． 2, and the downstream air supply port 11 has an air ratio of 0.2.
8 to supply air respectively.

In addition, in the figure, 14 is a secondary air supply port, which is arranged above the downstream burner 3.

In the above configuration, the fine powder returned by MiA/12 is
The classifier 13 supplies only coarse particles to the upstream burner 2 and only fine particles to the downstream burner 3, and supplies the upstream burner 2 with excess air. An amount of air is supplied to the downstream burner 3 so as to create an air shortage condition, and combustion is performed within the furnace body 1 while being mixed.

As a result, in Table 1, (upstream side) and ◎ (lower mal
) n1m-hi hard-yo I/r) shi1λ■^-y/fz9Q
d-+1. Hatake・rl・・a,,+++-, and the generation of unburned matter is also suppressed because combustion is not carried out in the state shown in ■ in Table 1, and it is temporarily shown in ■ in Table 1. Even if unburned matter is generated as a result of combustion, the generation location is on the upstream side and sufficient residence time can be taken for the unburned matter to burn out before being discharged, so the amount of discharge itself can be sufficiently suppressed.

In addition, the fuel supplied to the upper and lower burners 2.3 is not entirely reduced to fine particles below a predetermined level by the mill 12, but is sent to the upstream burner 2 in a coarse particle state. Since it is not necessary, it does not take much time to crush it, which is advantageous in terms of cost.

Note that even in the conventional combustion method in which equal amounts of air are supplied to the upper and lower burners, the present invention, which classifies the ash into coarse particles and fine particles, has the effect of reducing the unburned content in the ash.

FIG. 2 shows a second embodiment, in which a denitrification burner for decomposing Noxf generated on the upstream side is installed as the downstream burner 3. This denitrification downstream burner 3 includes a denitrification fuel supply pipe 15 and a denitrification fuel supply pipe 1t knee-ζt2-1ka・12j-re%J! I! l! ? m-ko・l-++-1
From ,-, it has a fine powder that is easy to burn, and
The denitrification air supply port 18 is supplied with air in an air-deficient state where the air ratio is less than 1. In this embodiment, as in the first embodiment, the effect of suppressing emissions of NOx and unburned substances can be obtained. In this case, between the upstream and downstream burners 2 and 3,
The two-stage combustion air supply port 14 and the after-air supply port 19 are arranged above the downstream burner 3, respectively, and the NO.
This is to more effectively suppress emissions of x and unburned matter.

In addition to coal, the above fuel may be delayed coke made from petroleum residue or fluid coke, as long as it contains flammable solid particles.
Furthermore, the fuel may be a mixture of coal and water or coal and oil. Further, the supply gas may be any gas containing oxygen, for example, pure oxygen.

Furthermore, there are various types of furnace body 1, such as the above-mentioned vertical type in which the combustion gas flows downward, and a horizontal type in which the combustion gas flows horizontally. In this case, for example, in a type in which combustion gas descends, the upper stage burner becomes the upstream burner.

Further, as the fuel supply means, as shown in FIG. 1, there are cases in which the mill 12 is connected to the furnace body 1, and cases in which it is not connected and is provided and transported separately from the combustion device.

Furthermore, as shown in Figure 1, Mi/l'12 may be one unit or multiple units, and in the case of multiple units, it is adapted to the requirements of each part 2 and 3. crushing ability,
The crusher is designed exclusively for cans, fine grains, and coarse grains. When such different types of pulverizers are provided, a part of the tM granule powder pulverizer from the pulverizer for coarse granules can be communicated with the pulverizer.

Further, the classifier 13 can be replaced with a structure having a classification function, and similar to the mill 12, there are two types of classification means: one connected to the combustion device and one not connected. Furthermore, regardless of the connection method, the classification means can be assembled into the Mi1v12 as an internal circulation type.

In addition, when using the above-mentioned classification u13, an airflow method such as a cyclone classifier using centrifugal force or a gravity classifier using fluid resistance is practical because it can classify a large amount of the total amount, but it is recommended to use a filter or strainer. A sieving method such as

(Effects of the Invention) As explained above, according to the present invention, on the upstream side (oxygen excess state), fuel is specifically supplied only to coarse particles, and on the downstream side (oxygen deficient state), fuel is supplied only to fine particles. Since combustion is achieved by supplying specific fuel to the ash, it is possible to effectively suppress the generation of both NOx and unburned matter in the ash. Moreover, it is possible to effectively suppress the generation of both NOx and unburned matter in the ash. , it is not necessary to make all the particles into fine particles, which is advantageous in terms of pulverization cost.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a combustion apparatus showing a first embodiment of the present invention, and FIG. 2 is a system diagram showing a second embodiment. 1...Furnace main body, 2...Upstream side pass, 3...Downstream side pass. Patent applicant: Kawasaki Heavy Industries, Ltd.

Claims (1)

[Claims] (A furnace body such as a reboiler is provided with an upstream parser and a downstream burner, and the upstream burner is placed upstream of the downstream burner with respect to the flow direction of the combustion gas, and the upstream par The supply amount per unit time of the oxygen-containing gas supplied to the burner is set to be larger than the supply amount of the oxygen-containing gas supplied to the downstream burner, and the combustible solids supplied to the upstream burner are A combustion device in which the average particle diameter of the twisted material containing particles is set to be larger than the average particle diameter of the twisted material containing combustible solid particles that is supplied to a downstream burner.