CN107930332B - A device and method for strengthening the removal of ultrafine particles in coal-fired boilers - Google Patents

Abstract

The invention relates to a device and a method for removing ultrafine particles in a reinforced coal-fired boiler, wherein the device is a cuboid as a whole, two angular inner grooves are symmetrically arranged in the middle of the cuboid up and down, one end of the device is a flue gas inlet, and the other end of the device is a flue gas outlet; a V-shaped turbulence piece is arranged on the axis of the device in front of the flue gas inlet and the angular inner grooves, the sharp corner of the V-shaped turbulence piece faces the flue gas inlet, and a [ V-shaped turbulence piece ] is arranged on the axis of the device behind the lowest point of the angular inner grooves. The device sets up symmetrical angular form inside groove through the upper and lower wall at the device to install the vortex piece of different shapes additional in the device, through angular form inside groove and vortex piece interact, produce the swirl in the device, make the better coalescence of granule, promote the granule to grow up. The invention has the advantages of convenient operation, simple manufacturing process, low operation cost and the like.

Description

A device and method for strengthening the removal of ultrafine particles in coal-fired boilers

technical field

The invention belongs to the technical field of removing ultrafine particles in flue gas, in particular to a device and method for strengthening the removal of ultrafine particles in coal-fired boilers, which is suitable for removing fine particles in coal-fired flue gas in industrial boilers.

Background technique

In recent years, due to the impact of various aspects of industrial production and life, the atmospheric environment has deteriorated day by day. Especially in autumn and winter, the content of PM _2.5 in the air has gradually increased, making the haze weather more and more serious. my country is a large industrial country. Coal-fired boilers are the most widely used in industrial production, and the flue gas of coal-fired boilers contains a large number of ultrafine particles. Traditional dust collectors such as electrostatic precipitators, bag filters, etc. The removal effect of medium and ultrafine particles (the equivalent diameter of particles is less than 1 micron) is not good, resulting in a large amount of ultrafine particles being discharged into the air and polluting the atmospheric environment. Therefore, a pretreatment stage is set before the flue gas enters the dust collector, so that the ultrafine particles in the coal-fired flue gas can be physically or chemically agglomerated into particles with larger diameters during the pretreatment stage, and then passed through the traditional dust collector. remove. This can not only increase the removal efficiency of the dust collector, but also greatly reduce the number density of ultrafine particles in the environment.

Particle agglomeration techniques can be divided into many types, such as acoustic agglomeration, electromagnetic agglomeration, charge agglomeration, turbulent flow agglomeration, chemical agglomeration, steam phase change, etc. At present, because of the simple operation of turbulent flow agglomeration, the cost in the use process is low, and this kind of process operation can be realized without changing the existing equipment, so turbulent flow agglomeration has been favored by many people, and it is used in engineering Also the widest. Turbulent agglomeration is a process in which particles in the flow field collide and agglomerate into larger particles because the velocity of the particles changes due to the disturbance of the flow field, which makes the particles in the flow field locally enriched or the radial velocity between the particles is uneven.

Liu Hanxiao (Liu Hanxiao. Numerical simulation of eddy coalescence of coal-fired ultrafine particles [D]. North China Electric Power University. 2011) proposed a coalescer, which is a cuboid with triangular prisms, large vortex A baffle made of two flat plates and a small vortex. The large scroll is set at the front end of the coalescer, and a small scroll is installed after a certain distance from the large scroll. There are two large scrolls and six small scrolls in each row. There are three rows of the same arrangement, and each row is connected to the Each row is separated by a baffle. After numerical simulation, although the coalescer has a good vortex generation effect, the number of large and small vortex pieces in the coalescer increases the flow resistance of the fluid, and it is equipped with multiple baffles, which not only increases the The complexity of the process also increases the resistance in the coalescer.

Contents of the invention

In view of the deficiencies in the prior art, the problem to be solved by the present invention is to provide a device and method for strengthening the removal of ultrafine particles in coal-fired boilers. The device sets symmetrical angular inner grooves on the upper and lower walls of the device, and installs spoilers of different shapes in the device, through the interaction between the angular inner grooves and the spoilers, a vortex is generated in the device, so that the particles are better Agglomeration promotes particle growth. The invention has the advantages of convenient operation, simple manufacturing process and low operating cost.

The technical solution adopted by the present invention to solve the technical problem is:

A device for strengthening the removal of ultra-fine particles in coal-fired boilers. The device is generally a cuboid, and is characterized in that two angular inner grooves are arranged symmetrically up and down in the middle of the cuboid. One end of the device is the flue gas inlet, and the other end is the flue gas Outlet; set a "V" shaped spoiler on the axis of the device before the smoke inlet and the angular inner groove, the sharp corner of the "V" shaped spoiler faces the smoke inlet, and the device behind the lowest point of the angular inner groove Arrange a "﹝"-shaped spoiler on the axis, the "﹝"-shaped spoiler is a symmetrical structure with respect to the axis of the device, and the sealing end of the "﹝"-shaped spoiler faces the smoke inlet, and the "﹝"-shaped spoiler A plurality of rectangular spoilers are set between the piece and the flue gas outlet. Two rectangular spoilers form a group and are symmetrical about the axis of the device. The "V" shaped spoiler, the hypotenuse of the "﹝" shaped spoiler and the The included angles between the rectangular spoiler and the axis of the device are equal; the flue gas outlet is a tapered outlet, and the flue gas outlet is connected to the electrostatic precipitator; the distance from the apex of the "V" shaped spoiler to the flue gas inlet is the total 2/15 of the length; the distance from the apex of the angular inner groove to the smoke inlet is 13/30 of the total length of the device; the distance from the sealing end of the "﹝" shaped spoiler to the smoke inlet is 17/ of the total length of the device 30; the distance from the end of the last group of rectangular spoilers to the smoke outlet is 6/30 of the total length of the device; the shortest distance between the two rectangular spoilers of the first group is greater than the "﹝" shaped spoiler The maximum distance between the two hypotenuses of .

A method for strengthening the removal of ultrafine particles in a coal-fired boiler, the method uses the above-mentioned device, and the specific steps are:

1) The incoming high-temperature flue gas enters the inlet of the coalescer at a speed of 10m/s. In the coalescer, the flue gas first flows through the "V" shaped spoiler to divert the flue gas and reduce the speed of the flue gas. The spoiler After that, a larger velocity gradient is generated, which will form two vortices in opposite directions behind the spoiler, and the small particles collide with each other under the action of the vortex to form larger particles;

2) For the flue gas flowing through the "V" shaped spoiler, due to the setting of the angular inner groove, the width of the device is first narrowed, so that the flow velocity of the flue gas increases, and then the width of the device increases again, so that the flue gas has a relatively large gap at this stage. A large velocity gradient will form a vortex on the edge of the angular inner groove, which will increase the impact between the particles and make the particles reunite;

3) The accelerated smoke flows through the "﹝"-shaped spoiler, and the sealing end of the "﹝"-shaped spoiler plays the role of diversion. When the smoke flows through the two hypotenuses of the spoiler, it will The role of the "﹝" shaped spoiler forms a vortex, which further causes the particles to interact and continue to grow; after that, the smoke flows through multiple rectangular spoilers that are distributed in an expanding manner to accelerate, and after the rectangular spoiler The particles grow again;

4) After step 3), the agglomerated particles pass through the flue gas tapering outlet, and the flow rate increases again, so that the agglomerated particles are fully mixed and flow out of the device, and then removed by the electrostatic precipitator.

Compared with prior art, the beneficial effect of the present invention is:

(1) The device of the present invention is symmetrically designed along the direction of flue gas flow, and a "V" shaped spoiler is provided at the flue gas inlet, with a top angle of 60° and two sides of equal length, so that the incoming flue gas flows through When the spoiler element is used, it can play the role of diversion, and can form two vortices in opposite directions behind the "V" shape. The small particles flow with the vortex to increase the probability of collision between the particles, so that the small particles are aggregated. into larger particles.

(2) Symmetrical angular inner grooves are arranged on the upper and lower walls of the device of the present invention, and this design can increase the flow velocity of the flue gas. And when the smoke flows through the second side of the angular inner groove, a vortex will be formed behind the symmetrical angular inner groove due to the disturbance. Particles interact strongly in the vortex, which can further coalesce the small particles that were not agglomerated due to the diversion of the "V" shaped spoiler before; Due to the effect of the vortex, the particles that have passed will also continue to grow and coalesce into larger particles.

(3) The device of the present invention adds a "﹝" shaped spoiler and a pair of rectangular spoilers behind the "V" shaped spoiler. The accelerated flue gas passes through the "﹝" shaped spoiler first, and after being diverted, two vortices are formed behind the "﹝" shaped spoiler, and the particles grow further under the action of the vortex. The grown particles flow through a pair of rectangular spoilers, the rectangular spoilers are combined with the tapered outlet at the tail, the tapered outlet accelerates the fluid, and then combine with the spoiler to form a vortex again, making the split fluid in the middle Part of the small particles get a higher probability of reunion in the vortex.

(4) In the method of the present invention, a flue gas flow rate of 10m/s is selected, and at this flue gas flow rate, it flows through a "V"-shaped spoiler element and forms a vortex behind the element. Because the distance between the "V"-shaped element and the flue gas inlet and the angular inner groove is appropriate, it not only plays the role of diversion, but also prevents the vortex generated by the spoiler from being damaged by the angular inner groove. The first side of the angular inner groove increases the flow velocity of the smoke. If the "V"-shaped element is too close to the angular inner groove, the vortex will be destroyed due to the increased flow velocity, which will affect the agglomeration effect.

(5) The present invention has a better effect when the superfine particles are aggregated and the particle size is relatively uniform, and the pressure drop in the whole process is 423.24 Pa, and the overall energy consumption is less. The device has a novel appearance and has the function of increasing the flow rate of the smoke and generating vortices. The turbulence element in the device has simple structure, low manufacturing cost, greatly improves the agglomeration effect, and has good development prospects.

Description of drawings

Fig. 1 is a schematic structural view of an embodiment of a device for removing ultrafine particles in a coal-fired boiler of the present invention;

Fig. 2 is the velocity vector diagram of Embodiment 1 of the device for strengthening ultrafine particulate matter removal in coal-fired boilers of the present invention;

Fig. 3 is a partially enlarged vector diagram of the "﹝"-shaped spoiler in Fig. 2;

Fig. 4 is the distribution diagram before and after the agglomeration of particle mean particle size in embodiment 1;

Fig. 5 is the percentage distribution figure of the outlet average particle diameter of embodiment 1;

In Fig. 1: 1-smoke inlet; 2-angular inner groove; 3-smoke outlet; 4-"V"-shaped spoiler; 5-"﹝"-shaped spoiler; 6-rectangular spoiler.

Detailed ways

The present invention will be described in detail below in conjunction with the embodiments and accompanying drawings, but this should not be used as a limitation to the protection scope of the claims of the present application.

The device for strengthening the removal of ultrafine particles in coal-fired boilers of the present invention (referred to as the device, see Figure 1), the device is generally a cuboid, and two angular inner grooves 2 are arranged symmetrically up and down in the middle of the cuboid, and one end of the device is a flue gas inlet 1 , the other end is the flue gas outlet 3; a "V" shaped spoiler 4 is set on the axis of the device before the flue gas inlet and the angular inner groove, and the sharp corner of the "V" shaped spoiler faces the flue gas inlet, and in the angular shape Arrange a "﹝"-shaped spoiler 5 on the device axis behind the lowest point of the inner tank. The "﹝"-shaped spoiler is a symmetrical structure with respect to the device axis, and the sealed end of the "﹝"-shaped spoiler faces the smoke At the entrance, a plurality of rectangular spoilers 6 are set between the "﹝" shaped spoiler and the smoke outlet. Two rectangular spoilers form a group and are symmetrical about the axis of the device. The "V" shaped spoiler, " ﹝The hypotenuse of the ""-shaped spoiler and the included angle between the rectangular spoiler and the axis of the device are equal; the flue gas outlet is a tapered outlet, and the flue gas outlet is connected to the electrostatic precipitator.

A further feature of the present invention is that the distance from the apex of the "V" shaped spoiler to the smoke inlet is 2/15 of the total length of the device; the distance from the apex of the angular inner groove to the smoke inlet is 13/ of the total length of the device 30; The distance from the sealing end of the "﹝" shaped spoiler to the smoke inlet is 17/30 of the total length of the device; the distance from the end of the last group of rectangular spoilers to the smoke outlet is 6/30 of the total length of the device 30.

The opening angle of the "V" shaped spoiler is 60°. The opening angle is determined according to the flow velocity of the incoming smoke, and the agglomeration effect of the fine particles is better when the angle is 60° under the flow velocity (10m/s) of the present invention. The sharp corner of the "V" shaped spoiler faces the smoke inlet, which can divert the smoke.

The apex angle of the angular inner groove is 120°. The angular inner groove is an isosceles triangle with an apex angle of 120°, and the apex angle faces the interior of the device. The angle of the angular inner groove can be adjusted according to the flow velocity of the incoming smoke. The apex angle of 120° is preferred. most.

The "﹝"-shaped spoiler has an overall isosceles trapezoidal shape, and the sealing end of the "﹝"-shaped spoiler is the upper bottom of an isosceles trapezoid, facing the smoke inlet. The isosceles trapezoid has no bottom, preferably an isosceles trapezoid The base angle is 60°. Different parameter selection will affect the agglomeration effect of fine particles.

The plurality of rectangular spoilers are in groups of two, and the two rectangular spoilers in each group are arranged symmetrically with respect to the axis of the device, and the distance between adjacent groups is equal, and the plane where each rectangular spoiler is located is the same as "﹝ The plane where the hypotenuse of the ""-shaped spoiler is parallel, the shortest distance between the two rectangular spoilers of the first group is greater than the maximum distance between the two hypotenuses of the "﹝"-shaped spoiler.

The key point of the device design of the present invention lies in the shape and size of the angular inner groove, the "V"-shaped spoiler, the "﹝"-shaped spoiler and the rectangular spoiler, and the relative position of each component arrangement. By adjusting the above parameters, it can be obtained optimal results. The first side of the angular inner groove can increase the flow rate of the smoke, and form a vortex behind the second side to increase the collision probability of particles. There are three different turbulence elements in the device, and the turbulence elements can agglomerate particles with different particle sizes at different positions, so that small particles can further grow into particles with larger particle sizes.

In the present invention, the number of "V"-shaped spoiler is one, the number of "﹝"-shaped spoiler is one, and the number of rectangular spoilers is multiple pairs. The number of rectangular elements 6 is preferably a pair. The "V" shaped spoiler can not only divert the smoke, but also form a vortex behind the spoiler so that the vortex is not destroyed. The "﹝"-shaped spoiler 5 not only plays the role of shunting flow but also forms a vortex to agglomerate small particles without destroying the vortex generated after the smoke flows through the angular inner groove.

The steps of the method for strengthening the removal of ultrafine particles in the coal-fired boiler of the present invention are:

1) The incoming high-temperature flue gas enters the inlet of the coalescer at a speed of 10m/s. In the coalescer, the flue gas first flows through the "V" shaped spoiler to divert the flue gas and reduce the speed of the flue gas. The spoiler Finally, a larger velocity gradient is generated, which will form two vortices in opposite directions behind the spoiler, and the small particles collide with each other under the action of the vortex to form larger particles.

2) For the flue gas flowing through the "V" shaped spoiler, because of the angular inner grooves on the upper and lower walls of the device, the width of the device on the first side of the angular inner groove gradually narrows, so that the flow velocity of the flue gas increases , and then the area width of the second side of the device in the angular inner groove gradually increases, so that the smoke has a larger velocity gradient in this area, and a vortex will be formed on the edge of the angular inner groove, which will increase the impact between the particles and make the particles reunited again.

3) The accelerated smoke flows through the "﹝"-shaped spoiler, and the sealing end surface of the "﹝"-shaped spoiler plays the role of diversion. When the smoke flows through the two hypotenuses of the spoiler, it will The role of the "﹝" shaped spoiler forms a vortex, which further makes the particles interact and grow continuously. After the flue gas flows through the rectangular spoiler, it undergoes an acceleration process again, and the particles grow up again behind the fins.

4) The agglomerated particles pass through the flue gas zoom outlet, and the flow rate increases again, so that the agglomerated particles are fully mixed and then flow out of the coalescer, and are connected to the electrostatic precipitator for removal.

After the particles with a particle diameter below 0.5 micron are agglomerated by the present invention, most of the particle diameters are between 2.4-3.8 microns. After the flue gas flows out of the coalescer, it is connected with the electrostatic precipitator, and after the next step of removal, the dust removal effect is better.

Example 1

In this embodiment, the device for strengthening the removal of ultrafine particles in coal-fired boilers is a cuboid as a whole. One end of the device is provided with a flue gas inlet 1, and the other end is provided with a flue gas outlet 3. The flue gas inlet is connected behind the desulfurization tower, and the flue gas outlet Connect the electrostatic precipitator; there is a "V" shaped spoiler 4 behind the flue gas inlet, and the sharp corner of the spoiler element 4 faces the flue gas inlet; the upper and lower walls of the device behind the "V" shaped spoiler Two angular inner grooves 2 are arranged symmetrically, and the top angle of the angular inner grooves 2 is 120°; after the smoke flows through the channel of the angular inner grooves, it passes through the "﹝" shaped spoiler 5, and the "﹝" shaped spoiler is arranged on the device On the axis, the sealing end face of the "﹝" shaped spoiler is perpendicular to the direction of smoke flow; after the smoke flows through the "﹝" shaped spoiler, it passes through a pair of rectangular spoilers 6, two rectangular spoilers Symmetrically distributed on both sides of the axis of the device, the rectangular spoiler is 30° from the direction of the smoke flow, and the shortest distance between the two rectangular spoilers is greater than the maximum between the two hypotenuses of the "﹝" shaped spoiler distance.

In this embodiment, the flue gas is produced by a fully automatic coal-fired boiler with a flue gas volume of 70Nm ³ /h. After desulfurization, the flue gas enters the flue gas inlet 1 through the dredging pipe, and the flue gas flow rate is 10m/s. The entire combiner is a cuboid structure with a length of 1520mm, a width of 500mm and a height of 300m. The distance from the apex of the "V" shaped spoiler to the smoke inlet is 2/15 of the total length of the device; the distance from the apex of the angular inner groove to the smoke inlet is 13/30 of the total length of the device; "﹝" shape The distance from the sealed end of the spoiler to the smoke inlet is 17/30 of the total length of the device; the distance from the end of the last group of rectangular spoilers to the smoke outlet is 6/30 of the total length of the device.

Fig. 2 is the velocity vector diagram of this embodiment. It can be seen from the vector diagram that when the smoke flows through the "V" shaped spoiler, two vortices in opposite directions will be formed behind it; after flowing through the angular inner groove, a vortex will be formed behind the angular inner groove; After passing through the "﹝" shaped spoiler, two vortices are formed behind the spoiler, and after flowing through a pair of rectangular spoilers, a vortex will be formed behind the rectangular spoiler, as can be seen from Figure 3; Under the action of the vortex, the fine particles increase the probability of collision and improve the reunion effect.

Figure 4 is a distribution diagram of the average particle size of particulate matter in flue gas before and after agglomeration. It can be seen from Figure 4 that before the particles are agglomerated, the average particle size of the particles is below 0.5 microns, and the particle size is relatively small. After agglomeration, it can be seen that compared with before agglomeration, the average particle size of the particles is between 2.4 microns and 3.8 microns, and the removal efficiency can reach 96%. The particle size within this range can be better removed by subsequent dust removal equipment remove. It shows that after the agglomeration of the device, the particle growth is obvious, and the agglomeration effect of the device is better.

Figure 5 is a percentage distribution diagram of the average particle size of the flue gas outlet after being agglomerated by the device of this embodiment. It can be seen from the figure that the particle size at the flue gas outlet is between 2.4-3.8 μm, and the particle size is 3.0 μm The particles accounted for more than 95%, indicating that the particle size of the agglomerated particles in the device of this embodiment is larger and can be removed more easily by subsequent processes.

What is not mentioned in the present invention is applicable to the prior art.

Claims (5)

1. A device for strengthening the removal of ultrafine particles in a coal-fired boiler, the device is generally a cuboid, characterized in that two angular inner grooves are arranged symmetrically up and down in the middle of the cuboid, one end of the device is a flue gas inlet, and the other end is a Smoke outlet; set a "V" shaped spoiler on the axis of the device before the smoke inlet and the angular inner groove, the sharp corner of the "V" shaped spoiler faces the smoke inlet, behind the lowest point of the angular inner groove Arrange a "﹝"-shaped spoiler on the axis of the device. The "﹝"-shaped spoiler is a symmetrical structure with respect to the device axis, and the sealing end of the "﹝"-shaped spoiler faces the smoke inlet. A plurality of rectangular spoilers are arranged between the spoiler and the smoke outlet, and two rectangular spoilers form a group, and the two rectangular spoilers in a group are symmetrical about the axis of the device, and the "V" shaped spoiler The oblique side of the "﹝"-shaped spoiler and the angle between the rectangular spoiler and the axis of the device are all equal; the flue gas outlet is a tapered outlet, and the flue gas outlet is connected to the electrostatic precipitator; the "V"-shaped spoiler The distance from the vertex of the part to the smoke inlet is 2/15 of the total length of the device; the distance from the vertex of the angular inner groove to the smoke inlet is 13/30 of the total length of the device; the sealing end of the "﹝" shaped spoiler The distance to the flue gas inlet is 17/30 of the total length of the device; the distance from the end of the last set of rectangular spoilers to the flue gas outlet is 6/30 of the total length of the device; the first set of two rectangular spoilers The shortest distance between them is greater than the maximum distance between the two hypotenuses of the "﹝" shaped spoiler. 2. The device for strengthening the removal of ultrafine particles in coal-fired boilers according to claim 1, characterized in that the opening angle of the "V" shaped spoiler is 60°. 3. The device for strengthening the removal of ultrafine particles in coal-fired boilers according to claim 1, characterized in that the apex angle of the angular inner groove is 120°. 4. The device for strengthening the removal of ultrafine particles in a coal-fired boiler according to claim 1, wherein the number of rectangular spoilers is two. 5. A method for strengthening the removal of superfine particles in a coal-fired boiler, the method uses the device described in any one of claims 1-4, and the device is a coalescer, and the specific steps are: 1) The incoming high-temperature flue gas enters the inlet of the coalescer at a speed of 10m/s. In the coalescer, the flue gas first flows through the "V" shaped spoiler to divert the flue gas and reduce the speed of the flue gas. The spoiler After that, a larger velocity gradient is generated, which will form two vortices in opposite directions behind the spoiler, and the small particles collide with each other under the action of the vortex to form larger particles; 2) For the flue gas flowing through the "V" shaped spoiler, due to the setting of the angular inner groove, the width of the device is first narrowed, so that the flow velocity of the flue gas increases, and then the width of the device increases again, so that the flue gas has a relatively large gap at this stage. A large velocity gradient will form a vortex on the edge of the angular inner groove, which will increase the impact between the particles and make the particles reunite again; 3) The accelerated smoke flows through the "﹝"-shaped spoiler, and the sealing end of the "﹝"-shaped spoiler plays the role of diversion. When the smoke flows through the two hypotenuses of the spoiler, it will The role of the "﹝" shaped spoiler forms a vortex, which further causes the particles to interact and continue to grow; after that, the smoke flows through multiple rectangular spoilers that are distributed in an expanding manner to accelerate, and after the rectangular spoiler The particles grow again; 4) After step 3), the agglomerated particles pass through the flue gas tapering outlet, and the flow rate increases again, so that the agglomerated particles are fully mixed and flow out of the device, and then removed by the electrostatic precipitator.

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