CN113280331A

CN113280331A - Preheating device, preheating burner, combustion system, pulverized coal boiler and control method thereof

Info

Publication number: CN113280331A
Application number: CN202110193938.XA
Authority: CN
Inventors: 吕清刚; 李百航; 那永洁; 高鸣; 朱建国; 欧阳子区; 刘敬樟; 满承波
Original assignee: Institute of Engineering Thermophysics of CAS
Current assignee: Institute of Engineering Thermophysics of CAS
Priority date: 2020-02-20
Filing date: 2021-02-20
Publication date: 2021-08-20
Also published as: CN116025893A; CN116085787A

Abstract

The invention relates to a preheating device, comprising: two liang of communicating preheating chamber, separator and returning charge ware, the separator has the separation cavity, wherein: the side wall of the preheating chamber and the side wall of the separator have a common part, namely a common side wall; or in a top view of the preheating device, the lower preheating chamber of the preheating chamber overlaps the separation chamber. The invention also relates to a combustion system comprising: a hearth; and the gas outlet of the separator of the preheating device is communicated with the hearth so as to supply fuel into the hearth. The invention also relates to a preheating burner, a combustion system, a pulverized coal fired boiler and a control method thereof.

Description

Preheating device, preheating burner, combustion system, pulverized coal boiler and control method thereof

Technical Field

The embodiment of the invention relates to the field of fuel pretreatment, in particular to a preheating device, a preheating burner, a combustion system, a pulverized coal boiler and a control method thereof.

Background

The low-nitrogen combustion technology widely used at present mainly comprises post-combustion removal technology (such as SNCR, SCR and the like) and in-combustion removal technology (mainly staged combustion technology). However, because the tail part of the boiler needs to be provided with an SNCR and SCR combined denitration device, the manufacturing cost, the installation cost and the operating cost of the system are greatly increased; in addition, in both the SNCR and SCR technologies, the NOx reduction reaction needs to be increased by injecting a large amount of ammonia water, but there is an ammonia slip phenomenon, which causes secondary pollution to the atmosphere.

To achieve economical ultra-low emissions, even near-zero emissions, the problem can only be fundamentally solved by developing a substantial reduction in nitrogen oxides during the combustion process.

The preheating burner is a device for pretreating fuel, and the preheating burner heats solid fuel by heat released by partial combustion of the preheating fuel in the preheating burner, so that the nitrogen of the fuel can be reduced. Thus, the preheat burner should be of sufficient volume to accommodate the high temperature gas-solid mixture while providing sufficient reaction space for fuel nitrogen removal. Therefore, the preheating burner is larger in size, higher in weight and higher in manufacturing cost, and further the scale enlargement and the application of the preheating burner are influenced.

In addition, the preheating process of the known circulating fluidized bed preheating burner is based on the principle of a circulating fluidized bed, but because the preheated high-temperature fuel contains a large amount of semicoke besides high-temperature combustible flue gas, the material circulating in the preheating burner is large-particle bed material and large-particle fuel. The material circulating in the preheating burner exhibits obvious 'binary' characteristics, namely, the particle size distribution of the material, and the particle size of the preheated high-temperature solid fuel (mainly semicoke with smaller particle size) is greatly different from that of the material circulating in the preheater (mainly semicoke with larger particle size and bed material), as shown in fig. 16. However, in the prior art, the separator would trap the preheated high-temperature solid fuel (mainly the carbocoal with smaller particle size) and send the fuel back to the preheater for internal circulation, which causes energy waste, which is not desirable.

In addition, there is a real need to further reduce fuel nitrogen in fuel pretreatment.

Disclosure of Invention

The present invention has been made to mitigate or solve at least one aspect or at least one point of the above-mentioned problems. According to an aspect of an embodiment of the present invention, there is provided a preheating device including:

a preheating chamber, a separator and a material returning device which are communicated in pairs, wherein the separator is provided with a separation chamber,

wherein:

the side wall of the preheating chamber and the side wall of the separator have a common part, namely a common side wall; or

In a top view of the preheating device, there is an overlap of the lower preheating chamber of the preheating chamber with the separation chamber.

Optionally, the common side wall is concave in shape towards the preheating chamber, such that the cross-sectional area of the upper part of the preheating chamber is smaller than the cross-sectional area of the lower part of the preheating chamber.

According to another aspect of an embodiment of the present invention, there is provided a preheating burner including:

the above-mentioned preheating device; and

and the gas outlet of the separator in the preheating device is communicated with the fuel nozzle.

According to another aspect of an embodiment of the present invention, there is provided a combustion system including:

a hearth; and

the preheating burner or the preheating device, wherein a gas outlet of the separator of the preheating device is communicated with the hearth to supply fuel into the hearth.

According to an aspect of an embodiment of the present invention, there is provided a pulverized coal boiler including:

a hearth;

the preheating burner is suitable for preheating the pulverized coal to form preheating fuel; and

at least one pre-heating fuel nozzle orifice,

wherein:

the preheating fuel nozzle is communicated with an outlet of the preheating burner and is suitable for introducing preheating fuel into the hearth.

The embodiment of the invention also relates to a control method of the pulverized coal fired boiler, which comprises the following steps:

preheating the pulverized coal by using a preheating burner to form preheating fuel; and

the preheated fuel from the preheating burner is fed into the furnace.

Drawings

FIG. 1 is a schematic view of a preheating arrangement according to an exemplary embodiment of the present invention;

FIG. 2 is a top view of the preheating device of FIG. 1;

FIG. 3 is an exemplary illustration of the form of a return feeder at different coupling depths;

FIG. 4 is a schematic view of a preheating arrangement according to another exemplary embodiment of the present invention, wherein the conical section of the separator is arranged eccentrically;

FIG. 5 is a top view of the preheating device of FIG. 4;

FIG. 6 is a schematic view of a preheating arrangement according to another exemplary embodiment of the present invention, wherein the conical section of the separator is arranged eccentrically;

FIG. 7 is a top view of the preheating device of FIG. 6;

FIG. 8 is a schematic view of a preheating arrangement according to an exemplary embodiment of the present invention, wherein a three-stage air distribution pattern is shown;

FIG. 9 is a schematic view from another perspective of the preheating device of FIG. 8;

FIG. 10 is a schematic top view of a preheating arrangement according to an exemplary embodiment of the present invention;

FIG. 11 is a schematic view of a preheating arrangement according to an exemplary embodiment of the present invention;

FIG. 12 is a top view of the preheating device of FIG. 11;

FIG. 13 is a schematic view of a preheating arrangement according to an exemplary embodiment of the present invention;

FIG. 14 is a top view of the preheating device of FIG. 13;

FIG. 15 is a schematic view for illustrating a preheating process of fuel in the preheating device;

FIG. 16 is a schematic illustration of the particle size of a "binary" material;

fig. 17 is a schematic front view of a pulverized coal boiler in accordance with an exemplary embodiment of the present invention.

Reference numerals in fig. 1-15 for the preheating means and preheating process indicate:

a preheating chamber 10, a fuel inlet 11, a preheating air inlet 12, an air distribution device 121 and a grading air distribution device 13 (grading

air distribution ports

131, 132 and 133 at each grade);

the separator comprises a separator 20, a separator cylinder section 21, a conical section 22, a top plate 23, a central cylinder 24 and a blanking pipe 25;

a material returning device 30;

fuel C, preheating air A and high-temperature fuel H;

a coupling depth d;

the radius r of the cylinder section of the cyclone separator;

separation chamber maximum width D;

the width W of the square cylinder preheating chamber, the length L of the square cylinder preheating chamber and the radius R of the cross section of the cylinder preheating chamber;

connecting channel P, connecting wall S.

The reference numerals in fig. 17 illustrate:

the device comprises a powder bin 1, a feeder 2, a powder feeding pipe 3, a fluidized air pipe 4, a fluidized air chamber 5, a fluidized air cap 6, a lifting pipe 7, a cyclone separator 8, a vertical pipe 9, a return feeder 10, a preheating fuel nozzle 11, a secondary air nozzle 12, a hearth 13 and a tertiary air nozzle 14.

Detailed Description

The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept of the present invention and should not be construed as limiting the invention. In the drawings, the same reference numerals are used to designate the same or similar components.

The invention provides a preheating device which comprises a preheating chamber, a separator and a material returning device which are communicated in pairs, wherein the preheating chamber and part of the side wall of the separator are shared, namely the shared side wall exists. Alternatively, part of the side walls of the separator also constitutes the side walls of the preheating chamber. As mentioned later, the separator may for example be of a conventional shape, while the upper part of the preheating chamber is modified with respect to conventional designs, for example of circular cross-section, i.e. there is a wall portion of a shape matching the outer shape of the separator, for example in cross-section in the shape of an arc concave towards the preheating chamber.

The technical solution of the present invention will be described in detail with reference to fig. 1 to 16.

As shown in fig. 1 and 2, the preheating device comprises a preheating chamber 10, a separator 20 and a material returning device 30 which are communicated with each other, wherein the separator 20 is coupled with the preheating chamber 10.

The preheating chamber 10 provides a space for preheating fuel, and on the preheating chamber 10, there are disposed: a fuel inlet 11, arranged at the lower part or bottom of the preheating chamber 10, adapted to introduce fuel C into the preheating chamber; a preheating air inlet 12, arranged at the bottom of the preheating chamber 10, is adapted to introduce preheating air a into the preheating chamber, which preheating air a will be used to fluidize the solid material in the preheating chamber 10 while providing oxygen needed for the partial combustion of the fuel. The bottom of the preheating chamber 10 is provided with an air distribution device 121 matched with the preheating air inlet, and the air distribution device is used for uniformly introducing preheating air A into the preheating chamber 10.

The separator 20 is a cyclone separator and comprises a cylinder section 21, a conical section 22 and a top plate 23, the upper part of the separator 20 is communicated with the upper part of the preheating chamber 10 and is suitable for separating high-temperature fuel preheated in the preheating chamber; a central cylinder 24 is arranged on the top plate, and the high-temperature fuel H which meets the requirement after being preheated leaves the preheating device from the central cylinder 24; the lower part of the conical section is provided with a blanking pipe 25, and the high-temperature solid fuel and bed materials collected by the separator enter the blanking pipe 25. The barrel section 21 corresponds to the separation chamber of the separator.

The return feeder 30 is in communication with the lower part of the feed pipe 25 of the lower part of the separator 20 and the lower part of the preheating chamber 10, and is adapted to return the high temperature solid fuel and the bed material in the feed pipe 25 to the preheating chamber 10.

In the method for realizing self-preheating of fuel by partial combustion, high-temperature solid fuel, namely semicoke, exists in the preheated high-temperature fuel except high-temperature gas fuel, and the material circulating in the preheating device is high-temperature semicoke and bed material with larger particle size, and the solid material has obvious 'binary' distribution characteristic, as shown in figure 16. Therefore, in a general circulating fluidized bed, since a high separation efficiency is required, the inlet section of the cyclone needs to have a distance long enough to accelerate the solid particles to 70% or more of the gas velocity by the drag force of the gas, thereby ensuring the separation effect of the cyclone. In the present invention, the high-temperature fuel formed must contain a certain amount of semicoke (the particle size of which is smaller than that of the material circulating in the preheater) in view of the particularity of the "binary" material. Based on the above principle, the inlet section of the cyclone separator is not separately provided, but is directly opened above the cylindrical section of the separator 20, and the wall thickness of the cylindrical section of the separator is used for providing time and space for accelerating solid materials for gas drag force. The opening directly forms a channel which is approximately tangential to the circumferential direction of the cylinder section. In addition, the section of the upper part of the preheating chamber is smaller than that of the lower part of the preheating chamber, so that a pre-accelerating link is provided for materials entering the separator.

In fig. 2, a communication channel P is provided between the outlet of the preheating chamber and the inlet of the separation chamber, said communication channel P comprising a connecting wall S tangentially connected to both the wall of the preheating chamber and the wall of the separation chamber.

In the present invention, the coupling of the separator and the preheating chamber means: the separator 20 is recessed into the inner space of the preheating chamber 10, i.e. the common side wall is recessed into the preheating chamber, so that the upper space of the preheating chamber 10 is compressed, and the cross section of the upper space of the preheating chamber 10 is enclosed by a part of the wall surface of the preheating chamber 10 and a part of the wall surface of the separator 20.

The separator can adopt the external shape and the internal space in the prior design, and the structure of the upper cylinder or the cylinder section and the lower cone or the cone section is kept consistent with the prior art. However, the separator may also be varied based on actual needs, as exemplified in fig. 4 and 6.

The coupling depth d is defined as the depth of the recess of the separator into the preheating chamber, the greater the coupling depth d, the smaller the cross-section of the upper space in the preheating chamber 10 relative to the cross-section of the middle-lower space. Under the condition that the cylinder section of the cyclone separator is cylindrical, the coupling depth is smaller than the diameter 2r of the cyclone separator, namely d is less than or equal to 2 r. In other words, as shown in fig. 2, the lateral maximum distance between the common side wall and the side wall of the lower part of the preheating chamber on the side of the separator (the boundary of the preheating chamber indicated by the dashed line in fig. 2) is the coupling depth D, which is not greater than the maximum width D of the separation chamber. In the case of a cylindrical barrel section, the maximum width D of the separation chamber is the diameter 2r in fig. 2. In the present invention, the maximum width D of the separation chamber means the maximum width of the separation chamber in the coupling direction.

The separator 20 is coupled to the preheating chamber 10, and the spaces of the separator 20 and the preheating chamber 10 are partitioned by a common wall surface, and the shape of the separator wall surface is maintained as a partial cylindrical shape and a partial conical cylindrical shape, so that, in the embodiment of fig. 1, the common wall surface can be understood as a wall surface where the intersecting line of both the preheating chamber 10 and the separator 20 is cut on the separator 20, including a part of the cylindrical section of the separator 20 and a part of the conical section.

In an alternative embodiment, the center of the conical section of the separator 20 is substantially aligned with the central axis of the cylindrical section of the separator 20, i.e., the downcomer and the cylindrical section of the separator 20 are arranged substantially concentrically in a top view of the separator 20. Thus, the back-feeder is arranged inside or outside the preheating chamber 10, depending on the relationship between the coupling depth d of the separator and the radius of the separator barrel section and the diameter of the downcomer.

The specific arrangement of the material returning device is specifically set according to the coupling depth of the separator 20 and the preheating chamber 10, as shown in fig. 3. Fig. 3 (a) shows a form of a material returning device when the coupling depth is less than r, in this case, because the coupling depth is smaller, the downcomer 25 is arranged outside the preheating chamber 10, and the material returning device is a complete U-shaped material returning device structure, that is, the material returning device structure comprises a descending section 31, an ascending section 32 and a material returning section 33; fig. 3 (b) shows a return feeder type with a coupling depth r, in which the downcomer 25 is partially disposed outside the preheating chamber 10 and partially disposed inside the preheating chamber 10, the return feeder is a U-shaped return feeder, and includes a descending section 31 and an ascending section 32, and the material collected by the separator passes through the downcomer 25, the descending section 31 and the ascending section 32 of the return feeder, and then directly enters the preheating chamber 10; in fig. 3, (c) is in the form of a return feeder where r < d <2r, in which case the downcomer 25 is arranged entirely within the preheating chamber 10, the return feeder being a U-shaped return feeder.

In another alternative embodiment, the cone segments of the separator 20 are arranged eccentrically, i.e. the apex of the cone segments do not coincide with the center of the barrel segments in a top view of the separator 20, as shown in fig. 4 and 6. By adopting the technical scheme, on one hand, the separation efficiency of the separator cannot be greatly influenced, on the other hand, the overall structural arrangement of the preheating device is favorably optimized, and the volume of the preheating device is further reduced. As a further alternative, the apex of the cone section coincides with the wall of the barrel section in a top view of the separator 20. Further, the top of the conical section is arranged below the cylinder section near the wall shared by the separator 20 and the preheating chamber 10, and the downcomer and the material returning device are arranged inside the preheating chamber 10; or further, the apex of the cone section is disposed below the separator barrel section adjacent the opposite side of the common wall surface, such as directly below the separator barrel section on the opposite side of the common wall surface.

Furthermore, in one embodiment, the apex of the cone section can be arranged directly below the wall shared by the separator and the preheating chamber cylinder section, i.e. in a top view, the discharge tube abuts against the wall shared by the separator and the preheating chamber cylinder section, as shown in fig. 4 and 5. In this embodiment, the return feeder is arranged inside the preheating chamber so as to further reduce the volume of the preheating device, and it is not necessary to arrange insulation material on the feeding pipe and the return feeder, reducing the cost of manufacturing the apparatus.

Alternatively, in another embodiment, the apex of the cone section can be arranged directly below the wall of the separator cylinder section facing the common wall of the separator and preheating chamber cylinder sections, i.e. in top view the blanking tube abuts against the separator wall on the side facing away from the preheating chamber, as shown in fig. 6 and 7. In this embodiment, the arrangement of the return feeder outside the preheating chamber facilitates maintenance of the return feeder during the operation phase, etc., by placing the return feeder outside.

In an alternative embodiment, both sides of the common wall are the high-temperature and high-material-concentration gas-solid mixture, i.e. one side is the high-temperature gas-solid mixture in the preheating chamber 10 and one side is the rotating solid material in the separator 20. During manufacturing, the common wall surface adopts a water cooling or steam cooling mode, and refractory and wear-resistant materials are respectively laid on two sides, and the technical scheme can prevent the common wall surface of the separator 20 and the preheating chamber 10 from being over-heated at the same time, so that the weight of the preheating device is further reduced. Optionally, since the common wall surface is a non-planar shape and has a part of conical surface, when the water-cooling or steam-cooling pipe is arranged, a form of local pipe jumping or pipe merging and the like can be adopted, which is a means of the prior art and is not described in detail. It is to be noted that, in the present invention, the preheating chamber and/or the separator may be provided with a heating surface, and in addition, it is not limited that the common wall surface is in a water-cooling or steam-cooling form, and at least a part of the sidewall of the preheating chamber and/or the separator may be in a water-cooling or steam-cooling form.

In order to strengthen the preheating effect, optimize the flow field in the preheating chamber and further reduce NO_xThe preheating chamber 10 can be provided with a graded air distribution port 13 (which can comprise graded air distribution ports of different levels) along the height direction of the preheating chamber besides the preheating air A introduced from the bottom131. 132, 133, etc.) to introduce a part of the preheated air a into the preheating chamber 10 from the side wall of the preheating chamber, and the lower part of the preheating chamber 10 is cut to the side so as to adapt to the preheating air organization of the graded air distribution, as shown in fig. 8 and 9. The graded tuyere 13 and the side tangent plane of the lower part of the preheating chamber are not on the same wall surface.

In an alternative embodiment, the preheating device may be formed by coupling a preheating chamber (referred to as a cylindrical preheating chamber) with an original cylindrical cross section and a cyclone separator, and the cross section of the preheating device formed after coupling is mirror-symmetrical approximately along a vertical plane where extension lines of circle centers of the preheating chamber 10 and the separator 20 are located, as shown in fig. 1 and fig. 2. The body of the preheating chamber 10 is a cylinder, optionally the diameter of the cylinder is not smaller than the diameter of the separator. A part of the wall surfaces of the cylinder section and the cone section of the separator 20 are concave towards the interior of the cylindrical preheating chamber 10, the wall surfaces of the separator 20 and the preheating chamber 10 are penetrated, and a preheating space with the upper cross section area smaller than that of the lower part is formed in the preheating chamber 10.

In the embodiment shown in fig. 1 and 2, a connecting channel is provided between the preheating chamber 10 and the separator 20, which connecting channel has one side of a wall of a conduit arranged outside the preheating chamber and the separator and the other side of an inner space of the preheating chamber, and can be tangent to the barrel-shaped walls of the preheating chamber 10 and the separator 20, which connecting the spaces of the preheating chamber 10 and the separator 20. The inlet of the separator is arranged at the intersection line of the tangential channel and the separator 20, and is an opening of the wall surface of the separator 20, and the direction of the opening is approximately tangential to the inner cylinder of the separator. It should be noted that although a "connecting channel" is provided between the preheating chamber 10 and the separator 20, the connecting channel has a limited effect on the acceleration of the gas flow due to the open space between the preheating chamber 10 and the connecting channel, and therefore, is different from the inlet acceleration section of the cyclone separator in the prior art.

In an alternative embodiment, the preheating device can also be formed by coupling a preheating chamber (called a square barrel preheating chamber) with a rectangular original cross section and a cyclone separator. As shown in fig. 10, the main body of the preheating chamber 10 is a straight quadrangular prism with a rectangular cross section, wherein one side of the straight quadrangular prism is coupled with the cyclone separator, the side length of the rectangular cross section of the side is defined as the preheating chamber width W, and the other side length is defined as the preheating chamber length L (when the preheating chamber is a circular preheating chamber, W is 2R, wherein R is the radius of the cross section of the cylindrical preheating chamber), then the preheating chamber width satisfies W ≧ 2R (R is the radius of the cylinder section of the cyclone separator). The side of the preheating chamber 10 coupled with the separator 20 forms a recess due to the coupling, the edge of the recess is the intersection line of the preheating chamber 10 and the separator 20, and the shape of the recess is matched with the separator 20. An inlet of the separator 20 is arranged above the square cylinder preheating chamber and along the intersection of the wall surface of the square cylinder preheating chamber and the separator 20, the inlet is approximately in tangential arrangement with the inner wall of the cylinder section of the separator 20, and solid materials are accelerated by utilizing the wall surface thickness of the separator.

The present invention can also adopt the following embodiments, as shown in fig. 11 and 12, in which the separator is processed into a separator having a rectangular prism space at the upper part and a rectangular pyramid space at the lower part, the rectangular pyramid space being wide at the upper part and narrow at the lower part, and the preheating chamber 10 is a square cylinder preheating chamber. The use of separators in the form of a quadrangular prism and a quadrangular pyramid facilitates the arrangement of the common wall of the preheating chamber 10 and the separator 20, and particularly for the common wall in the form of water cooling or steam cooling, this embodiment facilitates the arrangement of water cooling or steam cooling lines. Due to the fact that the wear-resistant material is laid inside the separator, if the separating effect of the separator needs to be further optimized, the wear-resistant material laid inside can be used for machining the inside of the separator into a relatively smooth cylindrical space. The separation performance of the separator can also be improved by arranging a chamfer on the square separator. Similar to the two embodiments shown in fig. 1, 2 and 10, in this embodiment, the inlet acceleration section of the cyclone separator is also implemented by the wall thickness of the separator 20, and will not be described again here.

Further, the separator may be processed into a separator having a cylindrical space at the upper part and a tapered space at the lower part, wherein the tapered space is formed by combining an N-prism and a matching N-pyramid (N is a positive integer greater than or equal to 4). Preferably, the N-prism and the N-prism are selected to be a regular N-prism and a regular N-pyramid in order to ensure the symmetry and the separation efficiency of the separator. Fig. 13 and 14 show an example of the preheating device in which N is 8.

As shown in fig. 10, 12 and 14, the sidewall outside the common sidewall of the preheat chamber includes a portion that is tangent to or coplanar with the sidewall outside the common sidewall of the separation chamber. More specifically, the wall indicated by L in fig. 10 is tangent to the side wall of the separation chamber, a portion of the side wall corresponding to L in fig. 12 is coplanar with the side wall of the separation chamber, and a portion of the side wall of the preheating chamber (upper and lower sides in fig. 14) is coplanar with the corresponding side wall in the octagon of the separation chamber (upper and lower sides in the octagon in fig. 14) in fig. 14.

Although not shown, for example, in fig. 12, the cross section of the preheating chamber may be a large rectangle, and the cross section of the separation chamber may be a small rectangle. Thus, in a top view of the preheating device, the common side wall of the preheating chamber and the separation chamber is part of one side wall of said preheating chamber. The embodiments shown in fig. 10 and 14 can also be modified in that the common side wall is only a part of the side wall of the preheating chamber. These are all within the scope of the present invention.

In the examples shown in fig. 10, 12 and 14, the inlet of the separation chamber may open into the preheating chamber, the inlet of the separation chamber constituting the outlet of the preheating chamber. In this way, compared to the prior art, a connecting channel arranged between the outlet of the preheating chamber and the inlet of the separation chamber is dispensed with. This further reduces the distance of the connecting channel of the inlet of the separator, thus reducing the acceleration effect of this connecting channel, further contributing to the reduction of the velocity of the smaller-size particles of the semicoke in the flue gas, thus facilitating their exit from the preheating device.

Similarly, the preheating chamber 10 may also take the form of a regular prism coupled to a separator 20 that also employs a regular prism or cylindrical cyclone separator, and is within the scope of the present invention.

Based on the technical solutions of the present invention shown in fig. 1-15, at least one of the following technical effects can be obtained:

1. the invention utilizes the minimum perimeter principle to couple the separator and the preheating chamber together, so that the total volume of the preheating device is reduced, the total internal and external surface area is reduced, the cost is saved, and the engineering amplification is facilitated;

2. a water cooling structure is adopted, so that the use of materials is reduced, and the weight and the volume of the preheating device are reduced;

3. the preheating chamber is coupled with the separator, so that the formed preheating chamber structure with a narrow upper part and a wide lower part can accommodate more bed materials, and the preheating device has larger heat capacity, so that the operation is more stable;

4. by coupling the separator to the preheating chamber, the distance of the connecting channel of the separator inlet can be reduced, thereby reducing the acceleration effect of this connecting channel, which is beneficial for reducing the velocity of the smaller particle size char particles in the flue gas, thereby facilitating their exit from the preheating device.

The fuel preheating process to which the preheating device of the present invention is applied is exemplarily described below.

As shown in fig. 15, in one embodiment of the present invention, the preheating chamber 10, the separator 20 and the return feeder 30, which are communicated with each other, constitute a circulation circuit, and the fuel C introduced into the preheating chamber from the fuel inlet 11 of the preheating chamber 10 is mixed with the preheating air a, etc. in the preheating chamber 10. The amount of the preheating air a is controlled based on the amount of the fuel C, so that the fuel C is partially combusted/gasified in the preheating chamber 10, and the heat is released to realize self-preheating. The fuel C is subjected to partial combustion/gasification reaction in the preheating chamber 10 to release heat, so as to generate a mixture of high-temperature coal gas and high-temperature coal coke (namely a high-temperature gas-solid mixture), and the preheating chamber 10 is in a strong reducing atmosphere. The high-temperature gas-solid mixture enters the separator 20 from the upper part of the preheating chamber 10, wherein the coke with larger particles is captured by the separator 20, enters the blanking pipe 25, and then returns to the preheating chamber 10 through the material returning device 30, so as to maintain the stability of the bed temperature in the preheating chamber and continue to participate in the preheating process; another part of the smaller-particle coal char not captured by the separator leaves the preheater from the central drum 24 at the top of the separator 20 together with the high-temperature gas, and the part of the coal char and the high-temperature gas together constitute the high-temperature fuel H. The specific working process of the preheating device of the invention is explained so far, in which the fuel C is added into the preheating device and the high-temperature fuel H leaves the preheating device to reach dynamic balance.

Because the preheating device utilizes the principle of a circulating fluidized bed, the establishment of material circulation needs to rely on the action of gravity, and therefore, the preheating device needs to be vertically placed during operation. The vertical direction in the present invention is therefore the same direction as the preheating chamber 10 and the separator 20 of the preheating device.

The preheating device of the present invention can be used as an integral part of a preheating burner or can directly provide fuel for a furnace chamber in a fuel system.

Based on the description shown in fig. 1-16 and above with reference to fig. 1-16, the present invention proposes the following technical solutions:

1. a preheating device, comprising:

wherein:

2. The preheating device according to 1, wherein:

the common side wall is concave toward the preheating chamber such that the cross-sectional area of the upper portion of the preheating chamber is smaller than the cross-sectional area of the lower portion of the preheating chamber.

3. The preheating device according to 2, wherein:

the cross section of the preheating chamber is a part of a circle or a regular polygon, the cross section of the separation chamber is a circle or a regular polygon, and the number of sides of the regular polygon is not less than 4.

4. The preheating apparatus according to 3, wherein:

the side wall outside the common side wall of the preheating chamber comprises a portion tangent to or coplanar with the side wall outside the common side wall of the separation chamber; or

In a top view of the preheating device, the common side wall is part of one side wall of the preheating chamber.

5. The preheating device according to 1, wherein:

the cross sections of the preheating chamber and the separation chamber are mirror images about a vertical plane defined by a vertical center line of the separation chamber and a vertical center line of the preheating chamber.

6. The preheating device according to any one of claims 1 to 5, wherein:

the inlet of the separation chamber is opened in the preheating chamber, and the inlet of the separation chamber forms the outlet of the preheating chamber.

7. The preheating apparatus according to 6, wherein:

the separation chamber inlet is arranged tangentially to the inner wall of the separation chamber.

8. The preheating device according to 1, wherein:

the cross section of the upper part of the preheating chamber is a part of a circle, and the cross section of the separation chamber is a circle; and is

A communication channel is arranged between the outlet of the preheating chamber and the inlet of the separation chamber, and the communication channel comprises a connecting wall which is in tangential connection with the wall surface of the preheating chamber and the wall surface of the separation chamber.

9. The preheating device according to any one of claims 2 to 8, wherein:

the separator comprises a cyclone separating cylinder for limiting a separating chamber, a conical section connected with the separating cylinder at the lower end of the separating cylinder, and a downcomer connected with the conical section at the lower end of the conical section, wherein the lower end of the downcomer is connected with an inlet of the material returning device.

10. The preheating apparatus according to 9, wherein:

the side wall of the preheating chamber shares a common part with the side wall of the separating drum of the separator, and the side wall of the cone segment shares a common part over the height of the cone segment.

11. The preheating apparatus according to 10, wherein:

the material returning device is provided with a U-shaped channel formed by a descending section and an ascending section, the descending pipe and the descending section are positioned outside the preheating chamber, and the ascending section is positioned in the preheating chamber.

12. The preheating apparatus according to 11, wherein:

the blanking pipe and the preheating chamber share the wall surface.

13. The preheating apparatus according to 10, wherein:

the material returning device is provided with a U-shaped channel formed by a descending section and an ascending section, and the descending pipe, the descending section and the ascending section are all positioned in the preheating chamber.

14. The preheating apparatus according to 13, wherein:

the conical section is an eccentrically arranged conical section, and the separating cylinder, the conical section and the downcomer are provided with collinear parts in the vertical direction of the preheating device.

15. The preheating apparatus according to 10, wherein:

the preheating chamber is provided with a material returning port, the material returning device and the descending pipe are both positioned outside the preheating chamber, and the outlet of the material returning device is communicated with the material returning port.

16. The preheating apparatus according to 15, wherein:

17. The preheating apparatus according to 9, wherein:

the lateral maximum distance between the common side wall and the side wall of the preheating chamber on the side of the separator is a coupling depth D, which is not greater than the maximum width D of the separation chamber.

18. The preheating apparatus according to 17, wherein:

the coupling depth D is less than one half of the maximum width D, namely D is less than D/2, the preheating chamber is provided with a material returning port, the material returning device and the descending pipe are positioned outside the preheating chamber, and the outlet of the material returning device is communicated with the material returning port; or

The coupling depth D is equal to one half of the maximum width D, namely D is equal to D/2, the material returning device is provided with a U-shaped channel formed by a descending section and an ascending section, the descending tube and the descending section are positioned outside the preheating chamber, and the ascending section is positioned inside the preheating chamber; or

The coupling depth D is larger than one half of the maximum width D and smaller than the maximum width D, namely D/2 < D < D, the material returning device is provided with a U-shaped channel formed by a descending section and an ascending section, and the descending tube, the descending section and the ascending section are all positioned in the preheating chamber.

19. The preheating device according to 1, wherein:

the lower part of the preheating chamber is provided with an inward inclined wall surface, and the lower part of the preheating chamber is provided with a grading air distribution port;

the wall surface where the graded air distribution opening is located is different from the surface of the inward inclined wall surface.

20. The preheating device according to any one of claims 1 to 19, wherein:

the preheating chamber and/or the separator are provided with a heating surface.

21. The preheating apparatus of claim 20, wherein:

at least a portion of the sidewall of the preheating chamber and/or the sidewall of the separator is a water cooled wall or a steam cooled wall.

22. The preheating apparatus of claim 21, wherein:

the shared side wall is a water cooling wall or a steam cooling wall.

23. The preheating apparatus of claim 21, wherein:

and the outside of the water-cooled wall or the steam-cooled wall is coated with a fireproof wear-resistant material.

24. A preheat combustor, comprising:

the preheating device of any one of claims 1-23; and

25. A combustion system, comprising:

a hearth; and

the preheating arrangement according to any one of claims 1 to 23, a gas outlet of a separator of the preheating arrangement being in communication with the furnace for supplying fuel into the furnace, or the preheating burner according to 24.

Fig. 17 shows a schematic front view of a pulverized coal boiler in an exemplary embodiment of the present invention.

As shown in fig. 17, the pulverized coal boiler according to the embodiment of the present invention includes: the device comprises a powder bin 1, a feeder 2, a powder feeding pipe 3, a fluidized air pipe 4, a fluidized air chamber 5, a fluidized air cap 6, a riser pipe 7, a cyclone separator 8, a vertical pipe 9, a return feeder 10, a preheating fuel nozzle 11, a secondary air nozzle 12, a hearth 13 and a tertiary air nozzle 14.

The lift pipe 7, the cyclone separator 8, the vertical pipe 9 and the return feeder 10 are combined into a circulating fluidized bed preheating burner which has the function of preheating coal powder, the coal powder is converted into high-temperature coal gas and part of unvaporized high-temperature solid fuel after being preheated by the circulating fluidized bed preheating burner, the high-temperature coal gas and part of unvaporized high-temperature solid fuel are called preheating fuel, the temperature of the preheating fuel is between 800 ℃ and 1000 ℃, and the preheating fuel is sprayed into a hearth 13 through a preheating fuel nozzle 11. The preheating process is actually a gasification/partial gasification reaction process.

It is also noted that the supply of pulverized coal to the riser 7 shown in fig. 17 is merely exemplary and is not limited to this embodiment as long as it is a device capable of feeding pulverized coal into the riser.

It should be noted that, as for the supply device of the fluidized air, in addition to the examples of the fluidized air chamber 5, the fluidized air cap 6, and the air distribution plate provided at the bottom of the riser 7 shown in fig. 17, the forms of the air distribution pipe and the air cap may be directly adopted as long as the fluidized air can be supplied to the riser 7. However, as can be appreciated by those skilled in the art, in situations where it is desirable to control the excess air factor in the riser or even in the circulating fluidized bed preheat combustor, the supply air volume of the fluidizing air needs to be controlled.

In order to enhance the preheating (gasification) effect of the preheating burner of the circulating fluidized bed, the lifting pipe 7 can be arranged into a water-cooled wall structure, the cyclone separator 8 can be arranged into an air-cooled cyclone separator or a steam-cooled cyclone separator, the inner part of the material returning device 10 can be arranged into an external bed form, namely, a water-cooled heating surface is arranged in the external bed of the material returning device.

The secondary air nozzle 12 can surround the periphery of the preheating fuel nozzle 11, the secondary air nozzle and the preheating fuel nozzle form a concentric circle, the secondary air nozzle 12 can be an annular channel, swirl blades can be arranged in the annular channel, and the annular channel can also be a plurality of single-pipe channels which are annularly arranged. The secondary air nozzles can also be arranged at the bottom of the hearth and adopt an air cap air supply form or an air pipe air supply form.

The working principle of the embodiment shown in fig. 17 is described below.

Heating surfaces are arranged in a lifting pipe, a cyclone separator and a material returning device of the circulating fluidized bed, so that the heat absorption capacity of the circulating fluidized bed is increased, namely the reaction amount of coal and oxygen can be increased under the condition of maintaining reasonable operation temperature of a preheating burner.

Because the circulating fluidized bed is a preheater, the excess air coefficient of pulverized coal combustion in the circulating fluidized bed is far less than 1.0, the circulating fluidized bed is in the overall reducing atmosphere, and CO are mainly generated after carbon in coal is converted₂And CH₄When gas is used, a small part of unconverted carbon remains in the solid fuel, the conversion of the carbon is increased by improving the gasification strength in the preheating process of the circulating fluidized bed, and meanwhile, the conversion of nitrogen in the coal to gaseous substances is greatly improved by improving the gasification strength.

Due to the existence of a large amount of CO and CH in the circulating fluidized bed preheating burner₄When the reducing gas is equal, nitrogen precipitated from the coal is easily converted into N₂The conversion, i.e. the circulating fluidized bed gasifier or the preheater is equivalent to a coal nitrogen remover, and the coal nitrogen removal rate can reach more than 70 percent.

After the preheated fuel after the coal nitrogen is removed is sprayed into a hearth, the conversion process of the nitrogen of the preheated fuel to NOx can be further inhibited by combining grading air distribution and temperature control, and a circulating fluidized bed preheating burner and a pulverized coal furnace are integrated, namely, the pulverized coal is fully gasified (preheated) in the circulating fluidized bed preheating burner and then sent into the pulverized coal furnace for combustion, so that the NOx emission level of pulverized coal combustion can be greatly reduced, and even the ultralow emission of the pulverized coal combustion can be directly realized.

In addition, in order to deeply reduce NOx emission, the reaction rate of the NO and the reducing gas such as CO can be enhanced in a mode of injecting a catalyst (such as limestone powder and the like) in the circulating fluidized bed preheating burner and the pulverized coal furnace.

A specific example of the embodiment according to fig. 17 is described in detail below.

The circulating fluidized bed preheating burner is characterized in that bed materials are laid in a lifting pipe of the circulating fluidized bed preheating burner, the type of the bed materials is quartz sand or river sand, the thickness of the material layer is 400-800mm, and the particle size of the bed materials is 0-2 mm.

And opening the system to induce air, primary air, fluidized air, return air, powder feeding air, secondary air and tertiary air, starting the igniter of the circulating fluidized bed, starting the feeding machine 2 below the powder bin 1 when the temperature of the circulating fluidized bed is stabilized at about 800 ℃, and spraying pulverized coal into the lifting pipe 7 through the powder feeding pipe 3 under the action of the primary air.

The air excess coefficient in the circulating fluidized bed is controlled to be between 0.3 and 0.8, such as 0.3, 0.32, 0.35, 0.4, 0.5, 0.7 or 0.8, the preheating burner temperature of the circulating fluidized bed is between 800 ℃ and 1000 ℃, such as 800 ℃, 900 ℃ or 1000 ℃, the pulverized coal has higher gasification (preheating) intensity in the circulating fluidized bed, and the carbon conversion rate is more than 70 percent.

The fluidizing air of the circulating fluidized bed can be air, or mixed gas of air and steam, or mixed gas of air, flue gas and steam. When the fluidized air contains steam, the gasification (preheating) of the coal powder can be promoted, the yield of the reducing gas is improved, and the reduction of nitrogen after the separation of the coal nitrogen is facilitated.

In the operation process, a small amount of limestone can be added into the circulating fluidized bed to promote the reduction of nitrogen oxides.

The coal powder is subjected to nitrogen removal in advance in the circulating fluidized bed, and the expression form of a small part of nitrogen in coal gas is HCN/NH₃After the preheated fuel is sprayed into the hearth to be combusted when meeting with secondary air, HCN/NH is further inhibited in the furnace through grading air distribution₃And the high-temperature coke nitrogen is converted into NOx, and meanwhile, a limestone spraying mode in the furnace is adopted to promote the reduction of the NOx.

The air excess coefficient below the tertiary air nozzle of the pulverized coal furnace is 0.85-0.95, such as 0.85, 0.90 or 0.95, and the air excess coefficient above the tertiary air nozzle is 1.15-1.35, such as 1.15, 1.20 or 1.35. The combustion temperature of the preheated fuel in the hearth is controlled between 1000 and 1250 ℃, for example, 1000 ℃, 1100 ℃ or 1250 ℃, so that the generation of thermal nitrogen oxides is effectively avoided.

The circulating fluidized bed preheating burner, the pulverized coal furnace staged combustion and the hearth temperature comprehensive control technology are combined, the emission level of NOx generated by pulverized coal combustion can be greatly reduced, and the ultralow emission of NOx in the pulverized coal industrial boiler can be directly realized.

In the exemplary embodiment of the structure shown in fig. 17, the preheating burner and the preheating fuel staged combustion process are combined, so that the pre-removal of coal nitrogen can be greatly completed in the preheating burner, the original emission of NOx generated by pulverized coal combustion is expected to be directly ultra-low, the manufacturing, installation and operation costs of a boiler are reduced, and secondary pollution is reduced.

In the exemplary embodiment of the configuration shown in fig. 17, the circulating fluidized-bed preheating burner is in the form of a water wall, which is compact and lightweight, and facilitates direct installation of the circulating fluidized-bed preheating burner and the boiler.

In the exemplary embodiment of the configuration shown in fig. 17, the circulating fluidized bed preheating burner introduces a steam gasifying agent for promoting gasification conversion, which enhances the particle modification effect and improves the quality of the preheated fuel, so that the residual carbon and the gasified gas entering the hearth can be stably and efficiently combusted.

Based on the description shown in fig. 17 and above with reference to fig. 17, the present invention proposes the following technical solutions:

1. a pulverized coal fired boiler comprising:

a hearth;

at least one pre-heating fuel nozzle orifice,

wherein:

2. The boiler of claim 1, wherein:

the preheating burner comprises a circulating fluidized bed preheating burner comprising:

a riser in which fuel is preheated;

a cyclone into which the preheated fuel fluid from the riser enters; and

one end of the material returning device is communicated with the lower end of the cyclone separator, and the other end of the material returning device is communicated with the lower part of the lifting pipe;

the preheating fuel nozzle is communicated with an upper outlet of the cyclone separator.

3. The boiler of claim 2, further comprising:

and the secondary air nozzle is used for introducing secondary air into the hearth.

4. The boiler of claim 3, wherein:

the secondary air nozzle is arranged around the preheating fuel nozzle; or

The secondary air nozzle is arranged at the bottom of the hearth.

5. The boiler of claim 3, wherein:

the secondary air nozzle is arranged around the preheating fuel nozzle and coaxially surrounds the outer side of the preheating fuel nozzle.

6. The boiler of claim 2, further comprising:

and the tertiary air nozzle is arranged at the middle upper part or the upper part of the hearth and is used for introducing tertiary air into the hearth.

7. The boiler of claim 6, wherein:

the excess air coefficient in the hearth below the tertiary air nozzle is between 0.85 and 0.95.

8. The boiler of claim 6, wherein:

the excess air coefficient in the hearth above the tertiary air nozzle is 1.15-1.35.

9. The boiler of claim 2, further comprising:

and the powder feeding pipe is used for conveying the coal powder from the coal powder bin into the lifting pipe, and the coal powder entering the lifting pipe is fluidized in the lifting pipe.

10. The boiler according to any one of claims 2-9, wherein:

at least one of the lifting pipe, the cyclone separator and the material returning device is provided with a heating surface.

11. The boiler of claim 10, wherein:

the heating surface of the lifting pipe is of a water-cooled wall structure.

12. The boiler of claim 2, wherein:

the fluidizing gas introduced into the riser is air or a mixture of air and flue gas.

13. The boiler of claim 2, wherein:

the fluidizing gas introduced into the riser is a mixed gas of air and steam or a mixed gas of air, flue gas and steam.

14. A control method of a pulverized coal fired boiler comprises the following steps:

the preheated fuel from the preheating burner is fed into the furnace.

15. The method of claim 14, wherein:

preheating pulverized coal by using a circulating fluidized bed preheating burner, wherein the circulating fluidized bed preheating burner comprises a lifting pipe, a cyclone separator and a material returning device; and is

Preheated fuel from the circulating fluidized bed preheating burner is fed into the furnace.

16. The method of claim 15, comprising the steps of:

the coal dust in the coal dust bin is fed into a lifting pipe, and the coal dust is suitable for preheating in the lifting pipe.

17. The method according to claim 15 or 16, comprising the steps of:

and controlling the air excess coefficient in the circulating fluidized bed preheating burner to be 0.3-0.8.

18. The method of claim 17, comprising the steps of:

the temperature in the circulating fluidized bed preheating burner is controlled to be between 800 ℃ and 1000 ℃.

19. The method of claim 17, comprising the steps of:

and introducing a catalyst into the circulating fluidized bed preheating burner and/or the hearth, wherein the catalyst is used for promoting the reduction of the nitrogen oxides.

20. The method of claim 17, wherein:

the hearth is provided with a tertiary air nozzle;

the method comprises the following steps: and introducing secondary air into the hearth, and controlling the air quantity of the secondary air to ensure that the excess air coefficient in the hearth below the tertiary air nozzle is between 0.85 and 0.95.

21. The method of claim 17, wherein:

the hearth is provided with a tertiary air nozzle;

the method comprises the following steps: and introducing tertiary air into the hearth, and controlling the air quantity of the tertiary air to ensure that the excess air coefficient in the hearth above the tertiary air nozzle is between 1.15 and 1.35.

Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments and combinations of elements without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

Claims

1. A preheating device, comprising:

wherein:

2. The preheating device according to claim 1, wherein:

3. The preheating device according to claim 2, wherein:

4. The preheating device according to claim 3, wherein:

5. The preheating device according to claim 1, wherein:

6. The preheating device according to any one of claims 1 to 5, wherein:

7. The preheating device according to claim 6, wherein:

8. The preheating device according to claim 1, wherein:

And a communication channel is arranged between the outlet of the preheating chamber and the inlet of the separation chamber, and comprises a connecting wall which is tangentially connected with the wall surface of the preheating chamber and the wall surface of the separation chamber.

9. The preheating device according to any one of claims 2 to 8, wherein:

10. The preheating device according to claim 9, wherein:

11. The preheating device according to claim 10, wherein:

12. The preheating device according to claim 11, wherein:

the blanking pipe and the preheating chamber share the wall surface.

13. The preheating device according to claim 10, wherein:

14. The preheating device of claim 13, wherein:

15. The preheating device according to claim 10, wherein:

16. The preheating device of claim 15, wherein:

17. The preheating device according to claim 9, wherein:

18. The preheating device of claim 17, wherein:

the coupling depth D is less than one half of the maximum width D, namely D is less than D, the preheating chamber is provided with a material return port, the material return device and the descending pipe are positioned outside the preheating chamber, and the outlet of the material return device is communicated with the material return port; or

The coupling depth D is equal to one half of the maximum width D, namely D is equal to D, the material returning device is provided with a U-shaped channel formed by a descending section and an ascending section, the descending pipe and the descending section are positioned outside the preheating chamber, and the ascending section is positioned inside the preheating chamber; or

19. The preheating device according to claim 1, wherein:

20. The preheating device according to any one of claims 1 to 19, wherein:

21. The preheating device of claim 20, wherein:

22. The preheating device of claim 21 wherein:

the shared side wall is a water cooling wall or a steam cooling wall.

23. The preheating device of claim 21 wherein:

24. A preheat combustor, comprising:

the preheating device of any one of claims 1-23; and

25. A combustion system, comprising:

a hearth; and

the preheating arrangement according to any one of claims 1 to 23, a gas outlet of a separator of the preheating arrangement being in communication with the furnace for supplying fuel into the furnace, or the preheating burner according to claim 24.

26. A pulverized coal fired boiler comprising:

a hearth;

at least one pre-heating fuel nozzle orifice,

wherein:

27. The boiler according to claim 26, wherein:

a riser in which fuel is preheated;

a cyclone into which the preheated fuel fluid from the riser enters; and

28. The boiler according to claim 27, wherein:

29. The boiler according to claim 28, wherein:

the lift pipe is of a water-cooled wall structure.

30. A control method of a pulverized coal fired boiler comprises the following steps:

the preheated fuel from the preheating burner is fed into the furnace.