WO2021218075A1

WO2021218075A1 - Flue mixer structure for sncr denitrification of pulverized coal boiler flue gas

Info

Publication number: WO2021218075A1
Application number: PCT/CN2020/123326
Authority: WO
Inventors: 林伟荣; 李楠; 宋润; 王海涛; 时正海; 高洪培
Original assignee: 华能国际电力股份有限公司; 中国华能集团清洁能源技术研究院有限公司
Priority date: 2020-04-29
Filing date: 2020-10-23
Publication date: 2021-11-04
Also published as: CN111420542A

Abstract

A flue mixer structure for SNCR denitrification of pulverized coal boiler flue gas, the structure comprising a pulverized coal boiler (1), a flue (2), a first drainage baffle (3), a mixer rear baffle (4), a mixer inner baffle (5), a mixer outer baffle (6), a mixer front baffle (7), a second diversion baffle (8) and an SNCR spray lance (9), wherein a flue gas outlet of the pulverized coal boiler (1) is connected to a flue inlet of the flue (2), and a flue gas outlet of the flue (2) is connected to an external SCR unit. The flue mixer structure is simple and achieves adequate mixing, thereby enhancing the SNCR denitrification efficiency.

Description

A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas

【Technical Field】

The invention relates to the technical field of environmental protection of coal-fired boilers, in particular to a flue mixer structure for SNCR denitration of flue gas of a pulverized coal boiler.

【Background technique】

In order to meet the requirements for ultra-low emission of pollutants (such as NO _x) emitted by coal-fired units, pulverized coal boilers generally adopt selective catalytic reduction (SCR method) for NO _x removal. This method has high construction costs for denitrification devices and catalysts. There are many problems such as large consumption, catalyst failure or poisoning, high disposal cost of waste catalyst and high potential harm to the environment. If the flue gas can be largely removed before entering the SCR device, most of its NO _x can be effectively alleviated in the downstream SCR device. The denitration pressure is beneficial to prolong the life of the SCR catalyst and produce good economic and social benefits.

When studying the selective non-catalytic reduction reaction of flue gas, it is found that if the reductant and flue gas can be quickly mixed, the self-oxidation share of the amino reductant in the high temperature environment can be effectively reduced, thereby increasing its use for NO _x reduction. Even if the flue gas temperature is relatively high, SNCR denitrification can still achieve a relatively ideal denitrification efficiency. For example, Qingneng Institute has found through experiments and simulation studies that under the conditions of a suitable ammonia-nitrogen molar ratio and rapid and uniform mixing of flue gas/reductant, Even in the high temperature flue gas of 1000℃, the denitration efficiency of SNCR can generally reach 60% to 70%, and the highest can be close to 80%. If a reasonable flue gas/reductant mixing and SNCR reaction device is designed at an appropriate position upstream of the SCR device of the pulverized coal boiler, the NO _x content in the flue gas before the SCR device can be effectively reduced, and the expected goal can be achieved.

[Summary of the invention]

The purpose of the present invention is to provide a flue mixer structure for SNCR denitration of pulverized coal boiler flue gas, which solves the problem of the existing equipment construction cost of _{the existing pulverized coal boiler using selective catalytic reduction SCR method for NO x removal} The defects of high cost and high cost of catalyst use.

In order to achieve the above objectives, the present invention adopts the following technical solutions to achieve:

The present invention provides a flue mixer structure for SNCR denitrification of pulverized coal boiler flue gas, including a mixer structure body, the mixer structure body is arranged in the flue; the mixer structure body includes a first drainage baffle The plate, the inner baffle of the mixer, the outer baffle of the mixer and the second drainage baffle, wherein the first drainage baffle is provided with two, which are symmetrically arranged on the side wall of the flue and are connected to the side of the flue. There is an inclination angle between the walls;

There are two inner baffles in the mixer, and the two inner baffles in the mixer are arranged in parallel in the flue; and one end of the two inner baffles in the mixer is respectively connected with the free ends of the two first drainage baffles;

There are two outer baffles of the mixer, and the two outer baffles of the mixer are placed downstream of the inner baffle of the mixer; S-shaped flow channel is formed between;

There are two second diversion baffles, one end of the two second diversion baffles is connected; the other ends of the two second diversion baffles are respectively connected to the two mixer outer baffles.

Preferably, a mixer back baffle is arranged at the connection between the first drainage baffle and the inner baffle of the mixer, and the mixer back baffle is vertically fixed on the side wall of the flue.

Preferably, the rear baffle of the mixer is a heat-resistant steel plate structure, and both sides of the heat-resistant steel plate structure are coated with a layer of refractory and wear-resistant material.

Preferably, a mixer front baffle is arranged between the two mixer outer baffles, and the mixer front baffle is vertically arranged between the two mixer outer baffles and is connected to the mixer outer baffle. The room is a concave structure.

Preferably, a triangular structure is formed between the front baffle of the mixer and the two second drainage baffles.

Preferably, the front baffle of the mixer is a heat-resistant steel plate structure, and both sides of the heat-resistant steel plate structure are coated with a layer of refractory and wear-resistant material.

Preferably, a plurality of SNCR spray guns are arranged on the first drainage baffle along its height direction, and the SNCR spray guns are connected with a reducing agent storage tank.

Preferably, the first drainage baffle, the mixer inner baffle, the mixer outer baffle and the second drainage baffle all comprise a heat-resistant steel plate structure, and both sides of the heat-resistant steel plate structure are coated with fire-resistant Abrasive material layer.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention provides a flue gas mixer structure for SNCR denitrification of pulverized coal boiler flue gas. A simple and efficient flue gas/reductant mixer structure body is used in a suitable area in the flue gas of a pulverized coal boiler to allow entrapment The flue gas containing the reducing agent can be fully mixed when flowing through it to improve the efficiency of the SNCR denitration reaction; the overall design of the device is relatively simple, and it can be directly arranged in the area where internal devices such as non-screen heat exchangers in the flue exist. The changes to the flue structure are very small, and better economic and social benefits can be harvested.

【Explanation of the drawings】

In order to explain the technical solutions of the embodiments of the present invention more clearly, the following will briefly introduce the drawings needed in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore do not It should be regarded as a limitation of the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative work.

Figure 1 is a front view and a top view of the mixer structure arranged in the flue of a pulverized coal boiler according to the present invention;

Figure 2 is a structural diagram of the mixer structural body;

Figure 3 is a structural diagram of the baffle;

Figure 4 Based on the flue width of the mixer related dimensions.

【Detailed ways】

The present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the present invention provides a flue mixer structure for SNCR denitration of pulverized coal boiler flue gas, which includes a pulverized coal boiler 1, a flue 2, a first drainage baffle 3, and a mixer rear baffle 4. Mixer inner baffle 5, mixer outer baffle 6, mixer front baffle 7, second drainage baffle 8 and SNCR spray gun 9, wherein the flue gas outlet of pulverized coal boiler 1 is connected to flue gas 2 The gas inlet, and the flue gas outlet of the flue 2 is connected to an external SCR device.

A mixer structural body for flue gas SNCR denitration is arranged upstream of the external SCR device, and the mixer structural body is arranged in the flue 2.

The mixer structure body includes a first drainage baffle 3, a mixer inner baffle 5, and a mixer outer baffle 6, wherein two first drainage baffles 3 are provided, which are symmetrically arranged in the flue 2. An inclination angle is arranged on the side wall and the side wall of the flue 2 so that the inner cavity of the flue 2 forms a reduced flow channel.

The mixer inner baffle 5 is provided with two, the two mixer inner baffles 5 are arranged in parallel in the flue 2;

Due to the narrow area caused by the existence of the inclined first drainage baffle 3, in order to avoid the pressure loss caused by a large amount of flue gas flowing into this area and then flowing back, the first drainage baffle 3 and the inner baffle 5 of the mixer are arranged at the junction There is a mixer rear baffle 4 perpendicular to the wall of the flue, so that the flue gas will flow back to the square flow channel constructed by the outer baffle 6 of the mixer and the wall of the flue.

A mixer back baffle 4 is provided at the connection between the first drainage baffle 3 and the inner baffle 5 of the mixer, and the mixer back baffle 4 is fixed on the side wall of the flue 2.

The mixer outer baffle 6 is provided with two, the two mixer outer baffles 6 are arranged in parallel in the flue 2; S-shaped flow channel is formed between 5.

Two second drainage baffles 8 are also provided downstream of the flue 2, and the two second drainage baffles 8 are arranged in a triangular structure.

The free ends of the two second drainage baffles 8 are connected to the two mixer outer baffles 6 respectively.

The free ends of the two second drainage baffles 8 are connected by the front baffle 7 of the mixer.

The front baffle 7 of the mixer and the outer baffle 6 of the mixer are perpendicular to each other.

The flue gas flows through the flow channel formed by the inner baffle 5 of the mixer, and flows back to the S-shaped flow channel between the inner baffle 5 of the mixer and the outer baffle 6 of the mixer due to the blocking effect of the front baffle 7 of the mixer.

The front baffle 7 of the mixer and the outer baffle 6 of the mixer are in a concave structure; the front baffle 7 of the mixer and the two second drainage baffles 8 are in a triangular structure; The baffle 8 forms a divergent flow channel.

The flue gas flowing from the square runners on both sides eventually converges and flows to the downstream of the flue. The existence of the divergent flue avoids the pressure loss of flue gas flowing in the abruptly increased flow area.

A certain number of SNCR spray guns 9 are arranged along the height direction on the wall surface of the first drainage baffle 3, and the reducing agent such as ammonia or urea solution is broken by the SNCR spray gun 9 and sprayed into the flue in the form of tiny droplets.

In the flow channel, due to the reduction of the cross-sectional area, the flue gas flow rate gradually increases, and the high-velocity flue gas flows forward with the reducing agent droplets entrained; due to the front baffle 7 of the mixer, the outer baffle 6 of the mixer, and the mixer The U-shaped flow channel constructed by the rear baffle 4 and the wall surface of the flue, the flue gas/reducing agent starts to flow along the U-shaped route in the mixer, and the flue gas and the reducing agent are promoted during the travel and turning of the flue gas. At the same time, high-speed flow will form a strong recirculation zone in the local right-angled area of the U-shaped flow channel, which can further improve the mixing effect of the flue gas and the reducing agent in the local internal drive.

The flue gas and the reducing agent have undergone two U-shaped deflection in the flow direction in the mixer, and the reduction of the flow channel has effectively improved the tassel, which is expected to achieve effective mixing, so as to obtain an ideal SNCR denitrification efficiency such as more than 60%. _{It can greatly reduce the NO x} concentration in the flue gas before the SCR device.

As shown in Figure 3, the first drainage baffle 3, the mixer back baffle 4, the mixer inner baffle 5, the mixer outer baffle 6, the mixer front baffle 7 and the second drainage baffle 8 The structure is the same, wherein the first drainage baffle 3 is a heat-resistant steel plate structure 10, such as a 310S stainless steel plate-shaped structure, and both sides of the plate-shaped structure are coated with a refractory and wear-resistant material layer 11.

The thicknesses D1, D2, and D3 of the heat-resistant steel 10 and the refractory and wear-resistant material layer 11 can be combined with the conditions of the pulverized coal boiler 1 and the mixer for comprehensive design.

As shown in Figure 4, the first drainage baffle 3, the mixer rear baffle 4, the mixer inner baffle 5, the mixer outer baffle 6, the mixer front baffle 7 and the second drainage baffle 8 are determined. After the thickness d, that is, d=D1+D2+D3, the specific size of the mixer is designed in combination with the flue width 12 of the flue area suitable for arranging the mixer in the flue 2:

1. The first diversion flap angle α 3 ₁ and the second diversion angle [alpha] ₂ of the shutter 8 may bind to a specific length of the particular design of the mixer arrangement region, the smaller the value, the flow reduction or gradual pressure loss due to expansion Smaller

2. In principle, the flow area in the mixer should be avoided to reduce the pressure loss of the flow, that is, the flow width 16 between the inner baffle 5 of the mixer and the outer baffle 6 of the mixer is equal to the outer baffle 6 of the mixer. The flow width 15 between the side wall of the flue and the flue 2, and the flow width 13 between the two mixer inner baffles 5 is equal to the flow width between the mixer inner baffle 5 and the mixer outer baffle 6 2 times of 16;

3. The baffle length 14 of the back baffle 4 of the mixer and the baffle length 20 of the front baffle 7 of the mixer should be determined by combining the

flow widths

13, 15 and 16 and the thickness d of the baffle;

4. The baffle length 18 of the inner baffle 5 of the mixer and the baffle length 17 of the outer baffle 6 of the mixer should be specifically determined in consideration of the space of the flue area where the mixer is arranged, and can be appropriately increased when conditions permit to increase the flue gas The mixing effect and residence time in the mixer are conducive to improving the denitration efficiency of SNCR;

5. Since the inner baffle 5 of the mixer needs to be partially inserted into the concave space formed by the outer baffle 6 of the mixer and the front baffle 7 of the mixer to form a U-shaped flow channel, for the consideration of reducing pressure loss, the flow width is 19 and The flow width 21 is equal and equal to the flow width 16.

The above content is only to illustrate the technical ideas of the present invention, and cannot be used to limit the scope of protection of the present invention. Any changes made on the basis of the technical solutions based on the technical ideas proposed by the present invention fall into the claims of the present invention. Within the scope of protection.

Claims

A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas, which is characterized in that it comprises a mixer structure body, the mixer structure body is arranged in the flue (2); the mixer structure body includes The first drainage baffle (3), the mixer inner baffle (5), the mixer outer baffle (6) and the second drainage baffle (8), wherein the first drainage baffle (3) is provided with Two, symmetrically arranged on the side wall of the flue (2), and an inclination angle is set between the side wall of the flue (2);

There are two baffles (5) in the mixer, the two baffles (5) in the mixer are arranged in parallel in the flue (2); and one end of the two baffles (5) in the mixer is connected to The free ends of the two first drainage baffles (3) are connected;

The mixer outer baffle (6) is provided with two, the two mixer outer baffles (6) are placed downstream of the mixer inner baffle (5); and the mixer inner baffles (6) are arranged in a one-to-one correspondence. 5) The outer side of the mixer forms an S-shaped flow channel with the baffle (5) in the mixer;

There are two second drainage baffles (8), one end of the two second drainage baffles (8) is connected; the other end of the two second drainage baffles (8) is connected to the two mixer outer blocks respectively. The board (6) is connected.
A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas according to claim 1, characterized in that, between the first drainage baffle (3) and the inner baffle (5) of the mixer A mixer back baffle (4) is arranged at the joint of the mixer, and the mixer back baffle (4) is vertically fixed on the side wall of the flue (2).
A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas according to claim 2, characterized in that, the mixer rear baffle (4) is a heat-resistant steel plate structure, and the heat-resistant steel plate Both sides of the structure are coated with a layer of refractory and wear-resistant material.
A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas according to claim 1, wherein a mixer front baffle is arranged between the two mixer outer baffles (6) (7), the mixer front baffle (7) is vertically arranged between the two mixer outer baffles (6), and is in a concave structure with the mixer outer baffle (6).
A flue mixer structure for SNCR denitrification of pulverized coal boiler flue gas according to claim 4, characterized in that the mixer front baffle (7) and two second drainage baffles (8) There is a triangular structure between.
A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas according to claim 4, wherein the front baffle (7) of the mixer is a heat-resistant steel plate structure, and the heat-resistant steel plate Both sides of the structure are coated with a layer of refractory and wear-resistant material.
A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas according to claim 1, characterized in that a plurality of SNCR spray guns are arranged on the first drainage baffle (3) along its height direction (9) The SNCR spray gun (9) is connected with a reducing agent storage tank.
A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas according to claim 1, wherein the first drainage baffle (3), the inner baffle (5) of the mixer, and the mixing The outer baffle (6) and the second drainage baffle (8) both comprise a heat-resistant steel plate structure, and both sides of the heat-resistant steel plate structure are coated with a layer of refractory and wear-resistant material.