CN111420541A - A new type of mixer structure suitable for SNCR denitrification of high temperature flue gas of pulverized coal boiler - Google Patents

Abstract

The invention provides a novel mixer structure suitable for SNCR denitrification of high-temperature flue gas of pulverized coal boiler. In a suitable area in the flue of the pulverized coal boiler, an efficient flue gas/reducing agent mixer is constructed based on the basic mixer body, which can realize Ideal SNCR denitration efficiency; its overall design is simple, and it can be directly arranged by using the area without screen heat exchangers in the flue, with small changes to the flue structure and little impact on the operation of the equipment downstream of the flue; due to the flue gas Acceleration in the mixer will increase the flow resistance and the design needs to strike a balance between flue gas flow loss and SNCR denitration efficiency in order to achieve the desired overall economic benefits.

Description

A new type of mixer structure suitable for SNCR denitrification of high temperature flue gas of pulverized coal boiler

technical field

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

Background technique

In order to meet the national requirements for ultra-low emission of pollutants such as NOx from the flue gas emitted by coal-fired units, pulverized coal boilers generally use the selective catalytic reduction SCR method to remove NOx. This method has the disadvantages of high construction cost of denitrification devices and large catalyst consumption. , catalyst failure or poisoning, high cost of disposal of waste catalyst and potential harm to the environment and many other problems. 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.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a novel mixer structure suitable for SNCR denitrification of high temperature flue gas of pulverized coal boiler, which solves the problem of low SNCR denitration efficiency existing in the prior art.

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

The present invention provides a novel mixer structure suitable for high-temperature flue gas SNCR denitrification of pulverized coal boilers, including a mixer arranged in a flue for high-temperature flue gas SNCR denitrification, the mixer is provided with at least one, the mixer The devices are arranged side by side along the radial direction of the flue.

Preferably, the mixer includes several basic mixer bodies, wherein the several basic mixer bodies are connected in series in sequence; the basic mixer body placed at the top is connected with a flue gas inlet unit; the basic mixer body placed at the tail A flue gas outlet unit is connected.

Preferably, the flue gas inlet unit and the flue gas outlet unit have the same structure, wherein the flue gas inlet unit includes two inclined baffles, and the two inclined baffles are arranged in a symmetrical structure; the axis of each inclined baffle and the flue is There is an inclination angle between them; the two ends of each inclined baffle are respectively connected with a first mixer baffle, and the free ends of the two first mixer baffles are connected; A right-angled triangular prism shape is formed between them; the two right-angled triangular prism shapes are arranged in a symmetrical structure.

Preferably, the opening of the flue gas inlet unit faces the upstream of the flue gas to form a reduction-type flow channel; the opening of the flue gas outlet unit faces the downstream of the flue gas to form a gradually expanding flow channel.

Preferably, the flue gas inlet unit is arranged with a plurality of SNCR lances.

Preferably, the basic mixer body includes two long box body structures, each of which is provided with an opening; the two long box body structures are symmetrically arranged, and the two openings are arranged oppositely; the two long box body structures are arranged oppositely; The box body structures are connected by an I-shaped connecting piece, and both ends of the I-shaped connecting piece are respectively placed in the cavities of the two long box body structures.

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

The invention provides a novel mixer structure suitable for SNCR denitrification of high-temperature flue gas of a pulverized coal boiler. A high-efficiency flue gas/reducing agent mixer is constructed based on the basic mixer body in a suitable area of the flue of the pulverized coal boiler, which can realize Ideal SNCR denitration efficiency; its overall design is simple, and it can be directly arranged by using the area without screen heat exchangers in the flue, with small changes to the flue structure and little impact on the operation of the equipment downstream of the flue; due to the flue gas Acceleration in the mixer will increase flow resistance, and the design needs to strike a balance between flue gas flow loss and SNCR denitration efficiency in order to achieve the desired overall economic benefits.

Description of drawings

FIG. 1 is a schematic diagram of a structure arranged in a plurality of mixers;

Figure 2 is a top view of the base mixer body;

Figure 3 is a front view of the base mixer body;

Figure 4 is a top view of the flue gas inlet unit;

Figure 5 is a front view of the flue gas inlet unit;

Figure 6 is a top view of the flue gas outlet unit;

Figure 7 is a front view of the flue gas outlet unit;

Fig. 8 is a mixer structure diagram constructed by a flue gas inlet unit, two basic mixer bodies and a flue gas outlet unit;

Figure 9 is a structural diagram of an inclined baffle;

Figure 10 is a structural diagram of a mixer baffle;

Figure 11 is a relative dimension drawing of the base mixer body based on flue width;

Among them, 1. pulverized coal boiler 2, flue 3, mixer 4, inclined baffle 5, SNCR spray gun 6, second mixer baffle 7, heat-resistant steel 8, fire-resistant and wear-resistant material layer 9, boundary baffle 10 , flue width 11, basic unit width 12, inlet width 13, runner width 14, runner width 15, runner width 16, runner width 17, baffle length 18, baffle length 19, baffle half length 20 , baffle length.

Detailed ways

At present, when studying the selective non-catalytic reduction reaction SNCR of flue gas, it is found that if the good mixing of reducing agent and flue gas can be achieved quickly, the self-oxidation share of amino reducing agent in high temperature environment can be effectively reduced, thereby improving its use in NOx reduction. Even if the flue gas temperature is high, SNCR denitrification can still achieve a relatively ideal denitration efficiency. For example, through experiments and simulation studies, it is found that under the conditions of suitable ammonia nitrogen molar ratio and rapid and uniform mixing of flue gas/reducing agent, even up to In the high temperature flue gas at 1000°C, the SNCR denitration efficiency can generally reach 60% to 70%, and the highest can be close to 80%. On the basis of this research, for the design of different types of SNCR denitration reactors, the relative comparative analysis was carried out from the perspectives of the coverage of the SNCR lance and the width of the flue. Flue gas SNCR denitration requires a basic mixer unit in the reusable flue, assisted by the design of the inlet and outlet of the mixer to promote droplet evaporation and reduce the loss of flue gas resistance, constructing a high-efficiency flue gas suitable for pulverized coal boilers For SNCR denitrification mixers and reactors, 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 NOx content in the flue gas before the SCR device can be effectively reduced to achieve the expected purpose; specifically:

As shown in FIG. 1 , the present invention provides a novel mixer structure suitable for SNCR denitration of high-temperature flue gas from pulverized coal boilers, including pulverized coal boiler 1, flue 2, mixer 3, inclined baffle 4, SNCR spray gun 5 and a mixer baffle 6, wherein a flue 2 is connected to the tail of the pulverized coal boiler 1, and a mixer 3 for high temperature flue gas SNCR denitration is arranged in the flue 2.

The mixer 3 includes several basic mixer bodies, wherein several basic mixer bodies are connected in series in sequence; the basic mixer body placed at the first is connected with a flue gas inlet unit; the basic mixer body placed at the tail is connected with a flue gas inlet unit. Flue gas outlet unit.

At least one mixer 3 is provided, and its height is the same as that of the flue; if more than two mixers 3 are provided, the mixers 3 are arranged side by side.

As shown in FIGS. 4 to 7 , the flue gas inlet unit and the flue gas outlet unit have the same structure, wherein the flue gas inlet unit includes two inclined baffles 4 , and the two inclined baffles are arranged in a symmetrical structure.

An inclination angle is set between the inclined baffle 4 and the axis of the flue 2 .

The two ends of the inclined baffle 4 are respectively connected with first mixer baffles, and the free ends of the two first mixer baffles are connected; a right-angled triangle is formed between the inclined baffle 4 and the two first mixer baffles. Prismatic shape.

The opening of the flue gas inlet unit faces the upstream of the flue gas; the opening of the flue gas outlet unit faces the downstream of the flue gas.

A plurality of SNCR spray guns 5 are arranged on the inclined baffle plate 4 at the flue gas inlet unit; an inclination angle is set between the installation direction of each SNCR spray gun 5 and the inclined baffle plate 4 .

The specific required number and arrangement of spray guns can be optimized by numerical simulation method in combination with the conditions of smoke temperature and smoke velocity.

The tail of the SNCR spray gun 5 is located in the closed right prism space, and the reducing agent solution pipeline passes through the flue wall surface above the space and enters the right prism space to be connected with the SNCR spray gun 5 . That is, the SNCR spray gun 5 can be arranged inside the flue, which can effectively solve several problems of the limited injection depth of the reducing agent solution after being sprayed by the SNCR spray gun 5, and break through the SNCR spray gun 5 in the SNCR denitration method. Traditional methods that cannot be arranged inside the flue.

The flue gas inlet unit is formed by two symmetrical straight triangular prisms to form a reduction-type flow channel, through which the high-temperature flue gas will be accelerated, and entrain the reducing agent droplets sprayed from the SNCR spray gun 5 into the basic mixer body.

As shown in FIG. 2 and FIG. 3 , the basic mixer body is composed of a second mixer baffle 6, which includes two long box body structures, each of which is provided with an opening; two long box body structures are provided with openings; The frame structure is symmetrically arranged, and the two openings are arranged oppositely.

The two elongated box structures are connected by an I-shaped connector, and both ends of the I-shaped connector are respectively placed in the cavities of the two elongated box structures.

As shown in FIGS. 9 and 10 , the inclined baffle 4 is made of heat-resistant steel material 7 , and the surface of the heat-resistant steel material 7 in contact with the flue gas is coated with a fire-resistant and wear-resistant material layer 8 .

The mixer baffle is made of heat-resistant steel, and both sides of the heat-resistant steel are coated with layers of refractory and wear-resistant materials.

The heat-resistant steel is 310S stainless steel as the baffle material.

After the flue gas/reducing agent enters the basic mixer body, due to the barrier of the vertical plate of the I-shaped connector, it is divided into two flue gas flows to both sides, and continues to complete the "Ω-type" flow route.

Since the flue gas and the reducing agent have completed multiple turning flows in the enclosed space, the mixing of the flue gas and the reducing agent is promoted during the traveling and turning of the flue gas. The right-angle area will form a strong recirculation area, which can further improve the mixing effect of flue gas and reducing agent in the local recirculation area.

The flue gas and reductant flow through a single basic mixer body to complete the U-shaped flow four times, and strengthen the mixing through multiple local reflux zones, which can achieve sufficient mixing and ideal SNCR denitrification. If it flows through 2 or more basic mixer bodies, the effect of mixing and SNCR denitration is better, although the flow pressure loss is also larger.

The basic mixer body is shown in Figure 8 and Figure 11. A good design of the channel width and other dimensions is the key to achieving lower flow pressure loss and higher SNCR denitration efficiency. The design principles should include the following points:

1. The width 10 of the flue 2 should be an integer multiple of the width 11 of the basic mixer body;

2. The width 11 of the basic mixer body should be 3 times the width 12 of its inlet;

3. The two "Ω-type" flow channels in the basic mixer body are symmetrically distributed, and the channel widths 13, 14, 15, and 16 are consistent;

4. The lengths 18 and 19 of the baffles in the basic mixer body need to be determined in combination with the number of basic mixer bodies used and the space in the flue area where the mixers are arranged.

In the present invention, an efficient flue gas/reducing agent mixer is constructed based on the basic mixer body in a suitable area in the flue 2 of the pulverized coal boiler 1, and an ideal SNCR denitration efficiency can be achieved. The overall design is simple, and the area without screen heat exchangers in the flue 2 can be used for direct arrangement, the changes to the structure of the flue are small, and the influence on the operation of the equipment downstream of the flue is small. Since the flue gas acceleration in the mixer will increase the flow resistance, the design needs to strike a balance between the flue gas flow loss and the SNCR denitration efficiency in order to obtain the desired overall economic benefits.

Claims (6)

1. The utility model provides a novel blender structure suitable for pulverized coal boiler high temperature flue gas SNCR denitration which characterized in that, is used for high temperature flue gas SNCR denitration blender (3) including arranging in flue (2), blender (3) are provided with at least one, blender (3) are arranged side by side along the radial direction of flue (2).

2. The novel mixer structure suitable for SNCR denitration of high-temperature flue gas of a pulverized coal boiler as claimed in claim 1, wherein the mixer (3) comprises a plurality of basic mixer bodies, wherein the basic mixer bodies are sequentially connected in series; the basic mixer body arranged at the head is connected with a flue gas inlet unit; the basic mixer body arranged at the tail part is connected with a smoke outlet unit.

3. The novel mixer structure suitable for SNCR denitration of high-temperature flue gas of a pulverized coal boiler is characterized in that the flue gas inlet unit and the flue gas outlet unit have the same structure, wherein the flue gas inlet unit comprises two inclined baffles (4), and the two inclined baffles are arranged in a symmetrical structure; an inclination angle is arranged between each inclined baffle (4) and the axis of the flue (2); two ends of each inclined baffle (4) are respectively connected with a first mixer baffle, and free ends of the two first mixer baffles are connected; a right-angle triangular prism shape is formed between the inclined baffle plate (4) and the two first mixer baffle plates; the two right-angle triangular prisms are arranged in a symmetrical structure.

4. The novel mixer structure suitable for SNCR denitration of high-temperature flue gas of a pulverized coal fired boiler as recited in claim 3, wherein the opening of the flue gas inlet unit faces the upstream of the flue gas to form a reduction-type flow passage; the opening of the smoke outlet unit faces the smoke downstream to form a gradually expanding flow channel.

5. The new mixer structure for SNCR denitration of pulverized coal boiler high temperature flue gas according to claim 2, characterized in that the flue gas inlet unit is arranged with a plurality of SNCR lances (5).

6. The novel mixer structure suitable for SNCR denitration of high-temperature flue gas of a pulverized coal fired boiler as recited in claim 2, wherein the basic mixer body comprises two rectangular frame structures, each rectangular frame structure is provided with an opening; the two rectangular frame structures are symmetrically arranged, and the two openings are oppositely arranged; the two rectangular frame structures are connected through an I-shaped connecting piece, and two ends of the I-shaped connecting piece are arranged in the cavities of the two rectangular frame structures respectively.

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