CN116085787A

CN116085787A - Pulverized coal boiler and control method thereof

Info

Publication number: CN116085787A
Application number: CN202211539062.0A
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: 2023-05-09
Also published as: CN116025893A; CN113280331A

Abstract

The invention relates to a pulverized coal boiler, comprising: a furnace; a preheating burner adapted to preheat pulverized coal to form a preheated fuel; and at least one pre-heat fuel nozzle, wherein: the preheating fuel nozzle is communicated with an outlet of the preheating burner, and the preheating fuel nozzle is suitable for leading preheating fuel into the hearth. The invention also relates to a control method of the pulverized coal boiler.

Description

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 pulverized coal boiler and a control method thereof.

Background

The low nitrogen combustion technology widely used at present mainly comprises a post-combustion removal technology (such as SNCR, SCR and the like) and an in-combustion removal technology (mainly a staged combustion technology). However, because the SNCR and SCR combined denitration device is required to be installed at the tail part of the boiler, the manufacturing cost, the installation cost and the operation cost of the system are greatly increased; in addition, in both SNCR and SCR technologies, a large amount of ammonia water needs to be sprayed to increase the NOx reduction reaction, but ammonia slip phenomenon exists, so that secondary pollution of the atmosphere is caused.

To achieve economical ultra-low emissions, even near zero emissions, the problem can be fundamentally solved only by greatly reducing nitrogen oxides in the development of combustion processes.

The preheating burner is a device for preprocessing fuel, which heats solid fuel by the heat released by the combustion of the preheating fuel in the preheating burner, so as to reduce the nitrogen of the fuel. Thus, the preheat burner is of sufficient volume to accommodate the high temperature gas-solid mixture while providing sufficient reaction space for the removal of fuel nitrogen. Therefore, the preheating burner has the advantages of larger volume, higher weight and higher manufacturing cost, and further affects the scale-up and application of the preheating burner.

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 materials circulating in the preheating burner are large-particle bed materials and large-particle fuels. The materials circulating in the preheater are preheated, so that the obvious 'binary' characteristic is shown, namely, the particle size distribution of the materials is shown, and the particle sizes of the preheated high-temperature solid fuel (mainly semicoke with smaller particle size) and the materials circulating in the preheater (mainly semicoke with larger particle size and bed material) are greatly different, as shown in figure 16. However, in the prior art, the separator can also trap the preheated high-temperature solid fuel (mainly semicoke with smaller particle size) and send the high-temperature solid fuel back to the internal circulation of the preheater, so that energy waste is caused, which is not expected.

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

Disclosure of Invention

The present invention is directed to alleviating or solving at least one aspect or point of the problems discussed above.

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

a furnace;

a preheating burner adapted to preheat pulverized coal to form a preheated fuel; and

at least one of the pre-heat fuel nozzle openings,

wherein:

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

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

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

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

Drawings

FIG. 1 is a schematic diagram of a preheating device 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 a schematic illustration of the return form at different coupling depths;

FIG. 4 is a schematic view of a preheating device according to another exemplary embodiment of the present invention, wherein the cone segments of the separator are eccentrically arranged;

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

FIG. 6 is a schematic view of a preheating device according to another exemplary embodiment of the present invention, wherein the cone segments of the separator are eccentrically arranged;

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

FIG. 8 is a schematic diagram of a preheating device according to an exemplary embodiment of the present invention, illustrating a three-stage air distribution mode;

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

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

FIG. 11 is a schematic diagram of a preheating device 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 device 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 diagram illustrating a warm-up process of fuel in the warm-up apparatus;

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

fig. 17 is a schematic front view of a pulverized coal boiler according to an exemplary embodiment of the present invention.

Reference numerals in fig. 1-15 relate to preheating devices and preheating processes:

preheating chamber 10, fuel inlet 11, preheating air inlet 12, air distribution device 121, stage air distribution device 13 (stage

air distribution ports

131, 132, 133);

Separator 20, separator section 21, cone section 22, top plate 23, central cylinder 24, blanking tube 25;

a return device 30;

fuel C, preheated wind A, high-temperature fuel H;

coupling depth d;

cyclone separator barrel section radius r;

the separation chamber maximum width D;

square tube preheating chamber width W, square tube preheating chamber length L, cylinder preheating chamber cross section radius R;

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 fluidization air pipe 4, a fluidization air chamber 5, a fluidization 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 embodiments of the present invention with reference to the accompanying drawings is intended to illustrate the general inventive concept and should not be taken as limiting the invention. In the drawings, the same reference numerals refer to the same or similar parts.

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

The technical scheme of the present invention will be specifically described 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 return 30 which are communicated with each other two by two, wherein the separator 20 and the preheating chamber 10 are coupled.

The preheating chamber 10 provides a space for preheating fuel, and the preheating chamber 10 is provided with: a fuel inlet 11, provided at the lower part or bottom of the preheating chamber 10, adapted to feed the fuel C into the preheating chamber; a preheating wind inlet 12, provided at the bottom of the preheating chamber 10, adapted to introduce preheating wind a into the preheating chamber, which will be used to fluidize the solid material in the preheating chamber 10 while providing oxygen required 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 for uniformly introducing the preheating air A into the preheating chamber 10.

The separator 20 is a cyclone separator and comprises a barrel section 21, a cone section 22 and a top plate 23, wherein 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 preheated high-temperature fuel H which reaches the requirement leaves the preheating device from the central cylinder 24; the lower part of the cone section is provided with a blanking pipe 25, and the high-temperature solid fuel and the bed materials which are trapped by the separator enter the blanking pipe 25. The barrel section 21 corresponds to a separation chamber of a separator.

The return device 30 is communicated with the blanking pipe 25 at the lower part of the separator 20 and the lower part of the preheating chamber 10, and is suitable for returning the high-temperature solid fuel and the bed material in the blanking pipe 25 to the preheating chamber 10.

In the method for realizing the self-preheating of the fuel by partial combustion, besides the high-temperature gas fuel, the preheated high-temperature fuel also contains high-temperature solid fuel, namely semicoke, while the materials circulating in the preheating device are high-temperature semicoke with larger particle size and bed materials, and the solid materials have obvious 'two-element' distribution characteristics, as shown in figure 16. Therefore, in a general circulating fluidized bed, since a high separation efficiency is required, the cyclone inlet section needs to have a long enough distance so that solid particles are accelerated 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, however, 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) for the specificity of the "two-component" material. Based on the above principle, instead of providing a separate separator inlet section in the cyclone separator inlet section, it is possible to open directly above the barrel section of the separator 20, with the wall thickness of the separator barrel section providing time and space for the gas drag to accelerate the solid material. The opening forms a channel that is directly formed substantially tangential to the circumferential direction of the barrel section. In addition, the upper section of the preheating chamber is smaller than the lower section, so that a pre-acceleration link is provided for the 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 toward the inner space of the preheating chamber 10, that is, the common side wall is recessed toward the preheating chamber, so that the upper space of the preheating chamber 10 is extruded, and the cross section of the upper space of the preheating chamber 10 is formed by enclosing a part of the wall surface of the preheating chamber 10 and a part of the wall surface of the separator 20 together.

The separator may take the external shape and internal space of existing designs, keeping the upper barrel or barrel section, lower cone or cone section configuration consistent with the prior art. However, the separator may also be changed based on actual needs, as in the examples shown in fig. 4 and 6.

The coupling depth d is defined as the depth of recess of the separator into the preheating chamber, the larger 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. In the case of cylindrical barrel sections of the cyclone, the coupling depth is smaller than the diameter 2r of the cyclone, i.e. d.ltoreq.2r. In other words, as shown in fig. 2, the maximum lateral distance between the common side wall and the side wall of the lower part of the preheating chamber on the separator side (preheating chamber boundary indicated by a broken 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, the space of the separator 20 and the preheating chamber 10 being separated by a common wall, the shape of which is maintained in a partial cylindrical shape and a partial conical shape, so that in the embodiment of fig. 1 the common wall is understood to be the wall of the separator 20 cut out of the intersecting line of both the preheating chamber 10 and the separator 20, comprising a part of the cylindrical section and a part of the conical section of the separator 20.

In an alternative embodiment, the cone section center of the separator 20 is substantially on the same vertical line as the cylinder section central axis of the separator 20, i.e. the downcomers and the cylinder section of the separator 20 are arranged substantially concentrically in a top view of the separator 20. The return is thus arranged inside or outside the preheating chamber 10, depending on the relationship between the coupling depth d of the separator and the separator barrel section radius and the downcomer diameter.

The specific arrangement of the return means is specifically set depending on the coupling depth of the separator 20 and the preheating chamber 10, as shown in fig. 3. In fig. 3 (a) is in the form of a return feeder with a coupling depth smaller than r, in which case, due to the smaller coupling depth, the down tube 25 is arranged outside the preheating chamber 10, the return feeder is a complete U-shaped return feeder structure, i.e. comprising a down section 31, an up section 32 and a return section 33; in fig. 3 (b), the material returning device is in the form of a material returning device with the coupling depth r, wherein a part of the down tube 25 is arranged outside the preheating chamber 10, a part of the material returning device is arranged inside the preheating chamber 10, the material returning device is a U-shaped material returning device, and comprises a down section 31 and an ascending section 32, and the material trapped by the separator directly enters the preheating chamber 10 from the down tube 25 after passing through the down section 31 and the ascending section 32 of the material returning device; in fig. 3 (c) is in the form of a return for r < d <2r, in which case the downcomers 25 are all arranged in the preheating chamber 10, the return being a U-shaped return.

In an alternative embodiment, the cone section of the separator 20 is arranged eccentrically, i.e. in a top view of the separator 20, the apex of the cone section does not coincide with the centre of the barrel section, as shown in fig. 4 and 6. By adopting the technical scheme, on one hand, the separation efficiency of the separator is not greatly influenced, and on the other hand, the whole structural arrangement of the preheating device is favorably optimized, and the volume of the preheating device is further reduced. Further alternatively, in a top view of the separator 20, the apex of the cone section coincides with the wall of the barrel section. Further, the apex of the cone section is arranged below the barrel section near the shared wall surface of the separator 20 and the preheating chamber 10, and the downcomers and the return are arranged inside the preheating chamber 10; or further, the apex of the cone section is disposed below the barrel section of the separator, near the opposite side of the common wall, e.g. directly below the barrel section of the separator, on the opposite side of the common wall.

Still further, in one embodiment, the apex of the cone section may be arranged directly below the wall shared by the separator and the preheating chamber section, i.e. the blanking tube is in close proximity to the wall shared by the separator and the preheating chamber section in top view, as shown in fig. 4 and 5. In this embodiment, the return feeder is arranged inside the preheating chamber, so that the volume of the preheating device is further reduced, and the arrangement of insulation material on the blanking pipe and the return feeder is not necessary, thereby reducing the cost of manufacturing the device.

Alternatively, in another embodiment, the apex of the cone section may be arranged directly below the wall of the section of the separator section opposite to the common wall of the section of the separator and the preheating chamber, i.e. the blanking pipe is in close contact with the wall of the separator on the side remote from the preheating chamber in a top view, as shown in fig. 6 and 7. In this embodiment, the return feeder is arranged outside the preheating chamber, and this arrangement places the return feeder outside, facilitating maintenance of the return feeder during the run phase, etc.

In an alternative embodiment, the common wall is flanked by high temperature, high material concentration gas-solid mixtures, i.e. high temperature gas-solid mixtures in the preheating chamber 10 on one side and rotating solid material in the separator 20 on one side. During manufacturing, the common wall surface adopts a water cooling or steam cooling mode, and fireproof and wear-resistant materials are respectively laid on two sides, so that the technical scheme can prevent the common wall surface of the separator 20 and the preheating chamber 10 from being overtemperature, and further reduce the weight of the preheating device. Optionally, the common wall surface is in a non-planar shape, and a part of conical surface exists, so that when the water cooling or steam cooling pipe is arranged, the local pipe jump or pipe union and other forms can be adopted, and the prior art means are adopted, so that the description is omitted. It is noted that in the present invention, the preheating chamber and/or the separator may be provided with a heating surface, and further, it is not limited to the common wall surface being in a water-cooled or steam-cooled form, and at least a part of the side wall of the preheating chamber and/or the separator may be in a water-cooled or steam-cooled form.

To strengthen the preheating effect, optimize the flow field in the preheating chamber and further reduce NO _x In addition to the preheating air A introduced into the bottom of the preheating chamber 10, a grading air distribution port 13 (which may include grading

air distribution ports

131, 132, 133, etc.) may be provided along the height direction of the preheating chamber, and a part of the preheating air A is introduced into the preheating chamber 10 from the side wall of the preheating chamber, and the lower portion of the preheating chamber 10 is cut laterally to adapt to the preheating air organization mode of the grading air, as shown in fig. 8 and 9. The lower side section of the classifying air distribution port 13 and 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 a cylindrical cross section and a cyclone separator, and the cross section of the preheating device formed by coupling is approximately in mirror symmetry along a vertical plane where an extension line of a connecting line of centers of the preheating chamber 10 and the separator 20 is located, as shown in fig. 1 and fig. 2. The body of the preheating chamber 10 is a cylinder, optionally having a diameter not smaller than the diameter of the separator. A part of the barrel section and cone section walls of the separator 20 face the inside of the barrel preheating chamber 10 and are recessed, the wall surfaces of the separator 20 and the preheating chamber 10 are communicated, and a preheating space with the upper cross section area smaller than that of the lower part is formed inside 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, one side of which is a wall of a duct arranged outside the preheating chamber and the separator, and the other side is an inner space of the preheating chamber, which connecting channel may be tangential to a barrel-shaped wall of the preheating chamber 10 and the separator 20, which connects the spaces of the preheating chamber 10 and the separator 20. The separator inlet is arranged at the intersecting line of the tangential passage and the separator 20, is an opening on the wall surface of the separator 20, and is approximately tangential to the inner cylinder of the separator. It should be noted that although a "connection channel" is provided between the preheating chamber 10 and the separator 20, it is distinguished from the inlet acceleration section of the cyclone of the prior art in that it has a limited acceleration effect on the air flow due to the open space between the connection channel and the preheating chamber 10.

In an alternative embodiment, the preheating device can also be formed by coupling a preheating chamber (called a square cylinder 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 rectangular cross-section straight quadrangular prism, wherein one side of the straight quadrangular prism is coupled with the cyclone, the rectangular cross-section side defining the side is the preheating chamber width W, and the other side is the preheating chamber length L (when the preheating chamber is a circular preheating chamber, w=l=2r, wherein R is the radius of the cross-section of the cylindrical preheating chamber), then the preheating chamber width satisfies w.gtoreq.2r (R is the radius of the barrel section of the cyclone). 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 intersecting line of the preheating chamber 10 and the separator 20, and the shape of the recess is matched with the separator 20. And an inlet of the separator 20 is arranged above the square cylinder preheating chamber and along the intersecting position of the wall surface of the square cylinder preheating chamber and the separator 20, and is approximately tangential to the inner wall of the cylinder section of the separator 20, so that the acceleration of solid materials is realized by utilizing the wall thickness of the separator.

The present invention may be applied to a separator in which a square prism and a square pyramid are combined to form a separator, the upper part of which is a square prism space and the lower part of which is a square pyramid space having a wide upper part and a narrow lower part, and the preheating chamber 10 is a square tube preheating chamber, as shown in fig. 11 and 12. The use of separators in the form of quadrangular prisms and rectangular pyramids facilitates the arrangement of the common wall of the preheating chamber 10 and the separator 20, in particular for the use of water-cooled or gas-cooled common wall, which embodiment facilitates the implementation of the arrangement of water-cooled or gas-cooled lines. Since the wear-resistant material is laid inside the separator, the separator can be processed into a relatively smooth cylindrical space by using the wear-resistant material laid inside, if necessary, to further optimize the separation effect of the separator. The separation performance of the separator can also be improved by providing a chamfer at the "square separator". Similar to the two embodiments shown in fig. 1, 2 and 10, in this embodiment, the cyclone inlet acceleration section is also implemented by using the wall thickness of the separator 20, which is not described here again.

Further, the separator may be processed into a separator having a columnar space at the upper part and a tapered space at the lower part, the tapered space being wider at the upper part and narrower at the lower part, the separator being composed of an N-prism and an N-pyramid matched with the N-prism (N is a positive integer of 4 or more). Preferably, the N-prism and the N-prism may be selected as a regular N-prism and a regular N-pyramid in order to secure symmetry and separation efficiency of the separator. Fig. 13 and 14 illustrate an example of a preheating device when N is 8.

As shown in fig. 10, 12 and 14, the side walls outside the common side wall of the preheating chamber comprise portions tangential or coplanar to the side walls outside the common side wall of the separation chamber. More specifically, the wall denoted by L in fig. 10 is tangential to the side wall of the separation chamber, and in fig. 12, a portion of the side wall corresponding to L is coplanar with the side wall of the separation chamber, and in fig. 14, 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 of the regular octagon 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 a part of one side wall of the preheating chamber. The embodiment 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. Which 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 be open to the preheating chamber, the inlet of the separation chamber constituting the outlet of the preheating chamber. In this way, the connecting channel arranged between the preheating chamber outlet and the separation chamber inlet is dispensed with in comparison with the prior art. This may further reduce the distance of the connecting channel at the inlet of the separator, thereby reducing the acceleration of the connecting channel, further facilitating the reduction of the velocity of the smaller size semicoke particles in the flue gas, thereby 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 which also takes the form of a regular prism or a cylindrical cyclone, also within the scope of the present invention.

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

1. the invention utilizes the principle of minimum perimeter 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 areas are reduced, the cost is saved, and the engineering amplification is facilitated;

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

4. by coupling the separator with the preheating chamber, the distance of the connecting channel at the inlet of the separator can be reduced, thereby reducing the acceleration effect of the connecting channel, which is beneficial to reducing the speed of semicoke particles with smaller particle size in the flue gas, thereby facilitating the semicoke particles to leave the preheating device.

The following exemplarily describes a fuel preheating process to which the preheating device according to the present invention is applied.

As shown in fig. 15, in one embodiment of the present invention, the preheating chamber 10, the separator 20 and the return 30, which are communicated two by two, constitute a circulation circuit, and the fuel C fed into the preheating chamber 10 from the fuel inlet 11 thereof is mixed with the preheating wind a or the like in the preheating chamber 10. The preheating wind 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 self-preheating is realized by releasing heat. The fuel C is subjected to partial combustion/gasification reaction in the preheating chamber 10, releases heat, and generates 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 coal 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 returning device 30, so that the temperature of the bed layer in the preheating chamber is kept stable and the preheating process is continuously participated; another portion of the smaller particle char not captured by the separator, which portion of char and hot gas together comprise the hot fuel H, leaves the preheater with the hot gas from the central drum 24 at the top of the separator 20. The fuel C is added into the preheating device and the high-temperature fuel H leaves the preheating device to achieve dynamic balance, so that the specific working process of the preheating device is described.

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, so that the preheating device needs to be vertically placed during operation. The vertical direction in the sense of the invention is thus the same direction as the axis of the preheating chamber 10 and separator 20 of the preheating device.

The preheating device of the invention can be used as a component of a preheating burner or can directly supply fuel to a hearth in a fuel system.

Based on the descriptions of fig. 1-16 and referring to fig. 1-16, the present invention proposes the following technical solutions:

1. a preheating device, comprising:

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 shared part, namely a shared side wall; or alternatively

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.

2. The preheating device according to 1, wherein:

the common side wall has a concave shape toward the preheating chamber such that the area of the cross section of the upper portion of the preheating chamber is smaller than the area of the cross section 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 device according to claim 3, wherein:

the side walls outside the common side wall of the preheating chamber comprise a portion tangential or coplanar to the side walls outside the common side wall of the separation chamber; or (b)

In a top view of the preheating device, the common side wall is a 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 in mirror symmetry with respect to a vertical plane defined by a vertical central line of the separation chamber and a vertical central line of the preheating chamber.

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

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

7. The preheating device 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 also provided with

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 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 2 to 8, wherein:

the separator comprises a cyclone separating cylinder defining a separating chamber, a cone section connected with the separating cylinder at the lower end of the separating cylinder, and a descending pipe connected with the cone section at the lower end of the cone section, wherein the lower end of the descending pipe is connected with the inlet of the material returning device.

10. The preheating device according to 9, wherein:

the side wall of the preheating chamber and the side wall of the separating cylinder of the separator have a shared part, and the side wall of the cone section has a shared part on the height of the cone section.

11. The preheating device according to 10, wherein:

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

12. The preheating device according to 11, wherein:

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

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

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

15. The preheating device according to 10, wherein:

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

16. The preheating device according to 15, wherein:

17. The preheating device according to 9, wherein:

the maximum transverse distance between the common side wall and the side wall of the lower part of the preheating chamber, which is positioned at one side of the separator, is the coupling depth D, and the coupling depth D is not greater than the maximum width D of the separation chamber.

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

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

The coupling depth D is equal to one half of the maximum width D, i.e., d=d/2, and the return has a U-shaped channel formed by a descending section and an ascending section, the descending pipe and the descending section being located outside the preheating chamber, the ascending section being located inside the preheating chamber; or alternatively

The coupling depth D is greater than one half of the maximum width D and less than the maximum width D, namely D/2 < D < D, and the returning charge device is provided with a U-shaped channel formed by a descending section and an ascending section, wherein the descending pipe, 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 of the grading air distribution opening is different from 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 is provided with a heating surface.

21. The preheating device according to claim 20, wherein:

at least a portion of the side wall of the preheating chamber and/or the side wall of the separator is a water cooled wall or an air cooled wall.

22. The preheating device according to claim 21, wherein:

the shared side wall is a water cooling wall or an air cooling wall.

23. The preheating device according to claim 21, wherein:

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

24. A preheat burner, comprising:

the preheating device according to any one of 1 to 23; and

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

25. A combustion system, comprising:

a furnace; and

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

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

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

The riser 7, the cyclone separator 8, the vertical pipe 9 and the material returning device 10 are combined into a circulating fluidized bed preheating burner, the circulating fluidized bed preheating burner has the function of preheating coal dust, the coal dust is converted into high-temperature coal gas and part of unvaporized high-temperature solid fuel after being preheated, 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 the hearth 13 through the 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 also be noted that, for the air supply device for fluidizing air, in addition to the example of the fluidizing air chamber 5, the fluidizing air cap 6 and the air distribution plate provided at the bottom of the riser pipe 7 shown in fig. 17, the form of an air distribution pipe and a cap may be directly adopted as long as the fluidizing air can be supplied to the riser pipe 7. However, as will be appreciated by those skilled in the art, in the event that control of the excess air ratio within the riser and hence the circulating fluidized bed preheating burner is required, the supply air volume of the fluidizing air needs to be controlled.

In order to strengthen the preheating (gasifying) effect of the circulating fluidized bed preheating burner, the riser 7 can be provided with a water-cooled wall structure, the cyclone separator 8 can be provided with an air-cooled cyclone separator or a steam-cooled cyclone separator, and the material returning device 10 can be provided with an external bed, namely, a water-cooled heating surface is arranged in the external bed of the material returning device.

The secondary air nozzle 12 may encircle 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 may be an annular channel, and swirl vanes may be disposed in the annular channel, or may be a plurality of single-tube channels arranged in an annular manner. The secondary air nozzle can also be arranged at the bottom of the hearth and adopts a hood air supply mode or an air pipe air supply mode.

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

Heating surfaces are arranged in a riser, 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 quantity of coal and oxygen can be increased under the condition of maintaining reasonable operation temperature of a preheating burner, and more coal nitrogen is separated out to be in a gaseous state and converted into nitrogen under the reducing atmosphere due to strong reducing atmosphere in the 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 an integral reducing atmosphere, and carbon in the coal is converted to mainly generate CO and CO ₂ And CH (CH) ₄ And (3) the gas is equal, 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.

Because a large amount of CO and CH exist in the circulating fluidized bed preheating burner ₄ The nitrogen precipitated in the coal is easy to N in the reducing gas ₂ The conversion, namely 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%.

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

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

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

Bed materials are paved 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 bed materials is 400-800mm, and the particle size of the bed materials is 0-2mm.

And (3) starting a system induced air, primary air, fluidization air, return air, powder feeding air, secondary air and tertiary air, starting a circulating fluidized bed igniter, starting a feeder 2 under a powder bin 1 when the temperature of the circulating fluidized bed is stabilized at about 800 ℃, and spraying pulverized coal into a lifting pipe 7 through a powder feeding pipe 3 under the action of the primary air.

The air excess coefficient in the circulating fluidized bed is controlled to be 0.3-0.8, 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 800-1000 ℃, 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%.

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 fluidization wind contains steam, the gasification (preheating) of coal dust can be promoted, the yield of reducing gas is improved, and the reduction of nitrogen to nitrogen after the precipitation of coal nitrogen is facilitated.

In the running 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 advanced removal of nitrogen in the circulating fluidized bed, and the expression form of less nitrogen in coal gas is HCN/NH ₃ And high-temperature coke nitrogen, and after preheated fuel is sprayed into the hearth and is burnt after meeting with secondary air, HCN/NH is further inhibited by grading air distribution in the hearth ₃ And converting high-temperature coke nitrogen into NOx, and simultaneously adopting a mode of spraying limestone into the furnace to promote the reduction of the NOx.

The excess air 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 excess air 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.

By combining the circulating fluidized bed preheating burner, the pulverized coal furnace staged combustion and the hearth temperature comprehensive control technology, the NOx emission level of pulverized coal combustion can be greatly reduced, and the ultra-low NOx emission of 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 the pulverized coal combustion is expected to directly reach an ultralow level, the manufacturing, installation and operation costs of the boiler are reduced, and the 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 cooled wall, which is compact and lightweight, and facilitates the direct installation of the circulating fluidized bed preheating burner and the boiler.

In the exemplary embodiment of the structure shown in fig. 17, the circulating fluidized bed preheating burner introduces a steam gasifying agent for promoting gasification conversion, which enhances the particle modifying effect, improves the quality of the preheated fuel, and enables the carbon residue and the gasification gas entering the furnace to be stably and efficiently combusted.

Based on the description of fig. 17 and referring to fig. 17, the following technical solutions are provided in the present invention:

1. A pulverized coal fired boiler comprising:

a furnace;

at least one of the pre-heat fuel nozzle openings,

wherein:

2. The boiler according to claim 1, wherein:

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

a riser in which fuel is preheated;

a cyclone separator 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 according to claim 2, further comprising:

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

4. The boiler according to claim 3, wherein:

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

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

5. The boiler according to claim 3, wherein:

the secondary air nozzle is disposed around the preheating fuel nozzle and coaxially surrounds the outside of the preheating fuel nozzle.

6. The boiler according to claim 2, further comprising:

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 according to 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 according to claim 6, wherein:

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

9. The boiler according to claim 2, further comprising:

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

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

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

11. The boiler according to claim 10, wherein:

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

12. The boiler according to claim 2, wherein:

the fluidization gas introduced into the lifting pipe is air or mixed gas of air and flue gas.

13. The boiler according to claim 2, wherein:

the fluidizing gas introduced into the lifting pipe 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 boiler comprises the following steps:

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

15. The method according to claim 14, wherein:

preheating pulverized coal by using a circulating fluidized bed preheating burner, wherein the circulating fluidized bed preheating burner comprises a riser, a cyclone separator and a material returning device; and is also provided with

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

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

and feeding the pulverized coal in the pulverized coal bin into a riser, wherein the pulverized coal is suitable for preheating in the riser.

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

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:

controlling the temperature in the circulating fluidized bed preheating burner to be 800-1000 ℃.

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 nitrogen oxides.

20. The method of claim 17, wherein:

the hearth is provided with a tertiary air nozzle;

the method comprises the steps of: and introducing secondary air into the hearth, and controlling the air quantity of the secondary air to enable the excess air coefficient in the hearth below the tertiary air nozzle to be 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 steps of: and introducing tertiary air into the hearth, and controlling the air quantity of the tertiary air to enable the excess air coefficient in the hearth above the tertiary air nozzle to be 1.15-1.35.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes may be made and equivalents may be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A pulverized coal fired boiler comprising:

a furnace;

at least one of the pre-heat fuel nozzle openings,

wherein:

2. The boiler according to claim 1, wherein:

a riser in which fuel is preheated;

3. The boiler according to claim 2, further comprising:

4. A boiler according to claim 3, wherein:

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

5. A boiler according to claim 3, wherein:

6. The boiler according to claim 2, further comprising:

7. The boiler according to claim 6, wherein:

8. The boiler according to claim 6, wherein:

9. The boiler according to claim 2, further comprising:

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

11. The boiler according to claim 10, wherein:

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

12. The boiler according to claim 2, wherein:

13. The boiler according to claim 2, wherein:

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

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

15. The method according to claim 14, wherein:

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

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

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

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

20. The method according to claim 17, wherein:

the hearth is provided with a tertiary air nozzle;

21. The method according to claim 17, wherein:

the hearth is provided with a tertiary air nozzle;