CN111420542A - A flue mixer structure for SNCR denitrification of pulverized coal boiler flue gas - Google Patents

Abstract

The invention provides a flue gas mixer structure for SNCR denitration of pulverized coal boiler flue gas. A simple and efficient flue gas/reducing agent mixer structure body is used in a suitable area of the flue gas of the pulverized coal boiler, so that the The flue gas containing the reducing agent can be fully mixed when it flows through it, so as to improve the efficiency of the SNCR denitration reaction; the overall design of the device is relatively simple, and it can be directly arranged by using the area where the internal devices such as no-screen heat exchangers exist in the flue. The changes to the flue structure are small, and good economic and social benefits can be obtained.

Description

A flue mixer structure for SNCR denitrification 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 used for SNCR denitration of flue gas of pulverized coal boilers.

Background technique

In order to meet the national requirements for ultra-low emission of pollutants (such as NOx, etc.) emitted by coal-fired units, pulverized coal boilers generally use selective catalytic reduction (SCR) to remove NOx. There are many problems such as large amount of flue gas, catalyst failure or poisoning, high disposal cost of waste catalyst and great potential harm to the environment, etc. If most of the NOx of the flue gas can be largely removed before it enters the SCR device, the denitration pressure of the downstream SCR device can be effectively relieved , which is beneficial to prolong the life of the SCR catalyst and produce good economic and social benefits.

China Huaneng Group Clean Energy Technology Research Institute Co., Ltd. (hereinafter referred to as Qingneng Institute) found that if a good mixing of reducing agent and flue gas can be quickly achieved during the research on selective non-catalytic reduction reaction (SNCR) of flue gas, the reduction of amino reducing agent The proportion of auto-oxidation in a high temperature environment increases its proportion for NOx reduction. Even if the flue gas temperature is high, SNCR denitrification can still achieve a relatively ideal denitration efficiency. Under the condition of high ammonia-nitrogen molar ratio and flue gas/reducing agent mixing quickly and evenly, even in high temperature flue gas up to 1000℃, the SNCR denitration efficiency can generally reach 60% to 70%, and the highest can be close to 80%. Reasonable design of flue gas/reductant mixture and SNCR reaction device at an appropriate upstream position of the SCR device can effectively reduce the NOx content in the flue gas before the SCR device and achieve the desired purpose.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a flue mixer structure for SNCR denitrification of pulverized coal boiler flue gas, which solves the problem of the existing pulverized coal boiler adopting selective catalytic reduction (SCR method for NOx removal, and the existing device construction cost) The defects of high cost and high cost of catalyst use.

In order to achieve the above object, the technical scheme adopted in the present invention is:

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

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

The outer baffles of the mixer are provided with two, and the two outer baffles of the mixer are placed downstream of the inner baffles of the mixer; An S-shaped flow channel is formed between them;

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

Preferably, a mixer rear baffle is provided at the connection between the first drainage baffle and the inner baffle of the mixer, and the mixer rear 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 layers of fire-resistant and wear-resistant materials.

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

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

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

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

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

Compared with the prior art, the beneficial effects of the present invention are:

The invention provides a flue gas mixer structure for SNCR denitration of pulverized coal boiler flue gas. A simple and efficient flue gas/reducing agent mixer structure body is used in a suitable area of the flue gas of the pulverized coal boiler, so that the The flue gas containing the reducing agent can be fully mixed when it flows through it, so as to improve the efficiency of the SNCR denitration reaction; the overall design of the device is relatively simple, and it can be directly arranged by using the area where the internal devices such as no-screen heat exchangers exist in the flue. The changes to the flue structure are small, and good economic and social benefits can be obtained.

Description of drawings

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

Fig. 2 is the structure diagram of mixer structure body;

Fig. 3 is the structure diagram of baffle;

Figure 4. Relative dimension drawing of the mixer based on flue width.

Detailed ways

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

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

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

The structural body of the mixer includes a first diversion baffle 3 , an inner baffle 5 of the mixer and an outer baffle 6 of the mixer, wherein two of the first diversion baffles 3 are arranged symmetrically on the side of the flue 2 . The side wall is provided with an inclination angle between 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.

There are two baffles 5 in the mixer, and the two baffles 5 in the mixer are arranged in parallel in the flue 2 ; and one end thereof is connected to the free end of the first drainage baffle 3 .

Due to the narrow area caused by the existence of the inclined first diversion baffle 3, in order to avoid the pressure loss caused by a large amount of flue gas flowing into the area and backflow, the first diversion baffle 3 and the baffle 5 in the mixer are set at the connection. There is a mixer rear baffle 4 perpendicular to the wall of the flue, so that the flue gas flows through here and will also flow back to the square flow channel formed by the outer baffle 6 of the mixer and the wall of the flue.

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

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

The downstream of the flue 2 is further provided with two second diversion baffles 8 , and the two second diversion baffles 8 are arranged in a triangular structure.

The free ends of the two second flow diversion baffles 8 are respectively connected with the two mixer outer baffles 6 .

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

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

The flue gas flowing from the square flow channels on both sides finally converges and flows downstream of the flue. The existence of the gradually expanding flue avoids the pressure loss of the flue gas flowing in the abruptly increased flow area.

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

In this flow channel, the flue gas flow rate gradually increases due to the reduction of the cross-sectional area, and the high flow rate flue gas flows forward with the reducing agent droplets entrained; The U-shaped flow channel constructed by the rear baffle 4 and the wall 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 traveling and turning of the flue gas. At the same time, the high-speed flow will form a strong recirculation zone in the local right-angle 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 reductant have undergone two U-shaped deflections in the flow direction in the mixer, and due to the narrowing of the flow channel, the tassel is effectively improved, and it is expected to achieve effective mixing, so as to achieve an ideal SNCR denitrification efficiency such as more than 60%, It can greatly reduce the NOx concentration of the flue gas before the SCR device.

As shown in Figure 3, the first flow 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 flow 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-like structure, and both sides of the plate-like structure are coated with refractory and wear-resistant material layers 11.

The thicknesses D1, D2 and D3 of the heat-resistant steel 10 and the refractory and wear-resistant material layer 11 can be comprehensively designed in combination with the conditions of the pulverized coal boiler 1 and the mixer.

As shown in FIG. 4 , the first diversion 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 diversion baffle 8 are determined. After the thickness d, that is, after d=D1+D2+D3, the specific dimensions of the mixer are designed in combination with the flue width 12 of the flue area suitable for arranging the mixer in the flue 2:

1. The inclination angle α1 of the first diversion baffle ₃ and the inclination angle α2 of the _second diversion baffle 8 can be specifically designed in combination with the specific length of the mixer arrangement area. The smaller the value, the pressure loss caused by the shrinkage or gradual expansion of the flow. the smaller

2. In principle, the change of 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 2 and the flue 2, and the flow width 13 between the inner baffles 5 of the two mixers is equal to the flow width between the inner baffle 5 of the mixer and the outer baffle 6 of the mixer 2 times 16;

3. The baffle length 14 of the mixer rear baffle 4 and the baffle length 20 of the mixer front baffle 7 need to be determined in combination with the flow widths 13, 15 and 16 and the baffle thickness d;

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 need to be determined in consideration of the space of the flue area where the mixer is arranged. When conditions permit, it can be appropriately increased to improve the flue gas. The mixing effect and residence time in the mixer are beneficial to improve 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, in order to reduce the pressure loss, the flow width 19 and The through-flow width 21 is equal and equal to the through-flow width 16 .

Claims (8)

1. A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas, characterized in that it comprises a mixer structure body, and the mixer structure body is arranged in the flue (2); the mixer structure The body comprises a first drainage baffle (3), an inner mixer baffle (5), an outer mixer baffle (6) and a second drainage baffle (8), wherein the first drainage baffle (3) Two are provided, symmetrically arranged on the side wall of the flue (2), and an inclination angle is set with the side wall of the flue (2); There are two baffles (5) in the mixer, and the two baffles (5) in the mixer are arranged in parallel in the flue (2); and one end of the baffles (5) in the two mixers is respectively connected to The free ends of the two first drainage baffles (3) are connected; The mixer outer baffles (6) are provided with two, and the two mixer outer baffles (6) are placed downstream of the mixer inner baffles (5); 5), an S-shaped flow channel is formed between the baffle plate (5) in the mixer; Two second drainage baffles (8) are provided, and one end of the two second drainage baffles (8) is connected; the other ends of the two second drainage baffles (8) are respectively connected with the outer blocks of the two mixers Board (6) connection. 2. A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas according to claim 1, characterized in that, the first drainage baffle (3) and the baffle (5) in the mixer A mixer rear baffle (4) is arranged at the connection between them, and the mixer rear baffle (4) is vertically fixed on the side wall of the flue (2). 3. 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 Both sides of the hot steel plate structure are coated with layers of refractory and wear-resistant materials. 4. A flue mixer structure for SNCR denitrification of pulverized coal boiler flue gas according to claim 1, characterized in that, a front mixer is arranged between the two mixer outer baffles (6) A baffle plate (7), the mixer front baffle plate (7) is vertically arranged between the two mixer outer baffle plates (6), and has a concave structure with the mixer outer baffle plate (6). 5. A flue mixer structure for SNCR denitrification of pulverized coal boiler flue gas according to claim 4, wherein the mixer front baffle (7) and two second drainage baffles ( 8) There is a triangular structure between them. 6. A flue mixer structure for SNCR denitration of pulverized coal boiler flue gas according to claim 4, wherein the mixer front baffle (7) is a heat-resistant steel plate structure, and the Both sides of the hot steel plate structure are coated with layers of refractory and wear-resistant materials. 7. A flue mixer structure for SNCR denitrification of pulverized coal boiler flue gas according to claim 1, characterized in that, the first drainage baffle (3) is arranged with a plurality of An SNCR spray gun (9), the SNCR spray gun (9) is connected with a reducing agent storage tank. 8. The structure of a flue mixer for SNCR denitrification of pulverized coal boiler flue gas according to claim 1, wherein the first drainage baffle (3) and the baffle (5) in the mixer , The mixer 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 layers of refractory and wear-resistant materials.

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