Selective non-catalytic reduction denitration system of circulating fluidized bed boiler

Abstract

The utility model discloses a selective non-catalytic reduction denitration system of a circulating fluidized bed boiler, which comprises a hearth provided with a dense-phase area; a separator; a hearth outlet flue; an upper secondary air pipe; the lower secondary air pipe is connected with an on-off valve; one end of the secondary air pipe denitration spray gun is connected with the lower end of the lower secondary air pipe, the other end of the secondary air pipe denitration spray gun is connected with a reducing agent storage tank through a reducing agent conveying pipe, and the secondary air pipe denitration spray gun is provided with an atomization steam pipe; one end of the hearth outlet denitration spray gun is connected with the hearth outlet flue, the other end of the hearth outlet denitration spray gun is connected with the reducing agent storage tank through a reducing agent conveying pipe, and the hearth outlet denitration spray gun is provided with an atomization steam pipe; and a coal feeding pipe. According to the selective non-catalytic reduction denitration system of the circulating fluidized bed boiler provided by the embodiment of the utility model, the use of the secondary air pipe denitration spray gun and the hearth outlet denitration spray gun can be adjusted based on the operation load, so that the problems of low denitration reaction efficiency and poor low-load denitration capability are solved, and the denitration efficiency is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of circulating fluidized bed boiler pollutant control, in particular to a selective non-catalytic reduction denitration system for a circulating fluidized bed boiler. Background Art

[0002] The flue gas generated by circulating fluidized bed boilers during operation contains a large amount of nitrogen oxides, which need to be treated with denitrification before they can be discharged. The denitrification method of circulating fluidized bed boilers in related technologies adopts the selective non-catalytic reduction (SNCR) denitrification process, but when the circulating fluidized bed boiler is running at a low load, the temperature is low and deviates from the smoke window temperature of the SNCR reaction, causing the denitrification efficiency to drop significantly. For this reason, some circulating fluidized bed boilers are equipped with a spray gun, which uses the spray gun to spray a reducing agent into the furnace to achieve the purpose of denitrification, but because the denitrification reaction requires a lower oxygen concentration, and the oxygen concentration in the furnace is high, it is still difficult to ensure the denitrification effect. Utility Model Content

[0003] The utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the utility model proposes a circulating fluidized bed boiler selective non-catalytic reduction denitration system, which has the advantages of good denitration effect and the like.

[0004] To achieve the above-mentioned purpose, according to an embodiment of the first aspect of the utility model, a circulating fluidized bed boiler selective non-catalytic reduction denitrification system is proposed, and the circulating fluidized bed boiler selective non-catalytic reduction denitrification system comprises: a furnace, the lower part of the furnace has a dense phase zone; a separator, the upper end of the separator is provided with a separator outlet flue and the lower end is connected to the dense phase zone through a return device and a return pipe; a furnace outlet flue, the furnace outlet flue is respectively connected to the upper part of the furnace and the upper part of the separator; an upper secondary air duct, the upper end of the upper secondary air duct is connected to an air source and the lower end is connected to the dense phase zone; a lower secondary air duct, the upper end of the lower secondary air duct is connected to the air source and the lower end is connected to the dense phase zone, and the lower end of the lower secondary air duct Located below the lower end of the upper secondary air duct, the lower secondary air duct is connected to a shut-off valve; a secondary air duct denitrification spray gun, one end of the secondary air duct denitrification spray gun is connected to the lower end of the lower secondary air duct and the other end is connected to the reducing agent storage tank through the reducing agent delivery pipe, and an atomizing steam pipe is arranged on the circumference of the secondary air duct denitrification spray gun, and the atomizing steam pipe is connected to a steam source; a furnace outlet denitrification spray gun, one end of the furnace outlet denitrification spray gun is connected to the furnace outlet flue and the other end is connected to the reducing agent storage tank through the reducing agent delivery pipe, and an atomizing steam pipe is arranged on the circumference of the furnace outlet denitrification spray gun, and the atomizing steam pipe is connected to a steam source; a coal feeding pipe, the upper end of the coal feeding pipe is connected to the furnace coal supply source and the lower end is connected to the dense phase zone.

[0005] The selective non-catalytic reduction denitration system for a circulating fluidized bed boiler according to the embodiment of the utility model has the advantages of good denitration effect and the like.

[0006] In addition, the selective non-catalytic reduction denitration system for circulating fluidized bed boilers according to the above embodiment of the utility model may also have the following additional technical features:

[0007] According to one embodiment of the utility model, the circulating fluidized bed boiler selective non-catalytic reduction denitrification system includes a medium load state, a high load state, a low load state and a startup state. In the low load state or the startup state, the secondary air duct denitrification spray gun is running and the on-off valve is closed to isolate the air. In the medium load state or the high load state, the furnace outlet denitrification spray gun is running and the on-off valve is opened.

[0008] According to an embodiment of the utility model, the circulating fluidized bed boiler selective non-catalytic reduction denitration system further comprises a separator inlet flue gas temperature detection device, and the separator inlet flue gas temperature detection device is suitable for detecting the inlet flue gas temperature of the separator.

[0009] According to one embodiment of the utility model, there are multiple separators and each of the separators is provided with a separator outlet flue and is connected to the dense phase zone through the return device and the return pipe, there are multiple furnace outlet flues, multiple furnace outlet flues are connected to the furnace and are respectively connected to multiple separators, there are multiple upper secondary air ducts and are arranged at intervals along the circumference of the furnace, there are multiple lower secondary air ducts and are arranged at intervals along the circumference of the furnace, each lower secondary air duct is connected with an on-off valve, there are multiple secondary air duct denitrification spray guns and are connected one-to-one with multiple lower secondary air ducts, there are multiple furnace outlet denitrification spray guns and are connected one-to-one with multiple furnace outlet flues.

[0010] According to an embodiment of the utility model, a header is provided outside the furnace, the header is connected to the gas source, and the upper ends of the plurality of upper secondary air ducts and the upper ends of the plurality of lower secondary air ducts are all connected to the header.

[0011] According to an embodiment of the utility model, the separator outlet flue is connected to a flue gas component detection device for detecting the concentration of nitrogen oxides in the flue gas.

[0012] According to an embodiment of the present invention, the lower end of the lower secondary air duct and the lower end of the coal feeding pipe are located at the same height on the furnace and are alternately arranged in the circumferential direction of the furnace.

[0013] According to an embodiment of the present utility model, the reducing agent in the reducing agent storage tank is urea solution or ammonia water.

[0014] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0016] Figure 1 It is a structural schematic diagram of a selective non-catalytic reduction denitration system for a circulating fluidized bed boiler according to an embodiment of the utility model.

[0017] Figure 2 It is a structural schematic diagram of a selective non-catalytic reduction denitration system for a circulating fluidized bed boiler according to an embodiment of the utility model.

[0018] Figure 3 It is a partial structural schematic diagram of a selective non-catalytic reduction denitration system for a circulating fluidized bed boiler according to an embodiment of the utility model.

[0019] Figure numerals: circulating fluidized bed boiler selective non-catalytic reduction denitrification system 1, furnace 10, straight section 11, contraction section 12, separator 20, separator outlet flue 21, flue gas composition detection device 22, return feeder 23, return feed pipe 24, furnace outlet flue 30, upper secondary air duct 40, lower secondary air duct 50, on-off valve 51, secondary air duct denitrification spray gun 61, furnace outlet denitrification spray gun 62, reducing agent delivery pipe 63, reducing agent storage tank 64, atomizing steam pipe 65, coal feeding pipe 70, manifold 80. DETAILED DESCRIPTION

[0020] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0021] In the description of the present utility model, it is necessary to understand that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. In addition, features defined as "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present utility model, unless otherwise specified, "multiple" means two or more.

[0022] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0023] The selective non-catalytic reduction denitration system 1 for a circulating fluidized bed boiler according to an embodiment of the utility model will be described below with reference to the accompanying drawings.

[0024] like Figure 1-Figure 3 As shown, the selective non-catalytic reduction denitrification system 1 for a circulating fluidized bed boiler according to an embodiment of the utility model includes a furnace 10, a separator 20, a furnace outlet flue 30, an upper secondary air duct 40, a lower secondary air duct 50, a secondary air duct denitrification spray gun 61, a furnace outlet denitrification spray gun 62 and a coal feeding pipe 70 (the up and down directions are shown by the arrows in the figure).

[0025] The lower portion of the furnace 10 has a dense phase zone.

[0026] The upper end of the separator 20 is provided with a separator outlet flue 21 and the lower end is connected to the dense phase zone through a return device 23 and a return pipe 24.

[0027] The furnace outlet flue 30 is connected to the upper portion of the furnace 10 and the upper portion of the separator 20 respectively.

[0028] The upper end of the upper secondary air duct 40 is communicated with the air source and the lower end is communicated with the dense phase zone.

[0029] The upper end of the lower secondary air duct 50 is connected to the air source and the lower end is connected to the dense phase zone. The lower end of the lower secondary air duct 50 is located below the lower end of the upper secondary air duct 40 . The lower secondary air duct 50 is connected to an on-off valve 51 .

[0030] One end of the secondary air duct denitrification spray gun 61 is connected to the lower end of the lower secondary air duct 50 and the other end is connected to the reductant storage tank 64 through the reductant delivery pipe 63. An atomizing steam pipe 65 is provided on the circumference of the secondary air duct denitrification spray gun 61, and the atomizing steam pipe 65 is connected to the steam source.

[0031] One end of the furnace outlet denitration spray gun 62 is connected to the furnace outlet flue 30 and the other end is connected to the reducing agent storage tank through the reducing agent delivery pipe 63. An atomizing steam pipe 65 is provided on the circumference of the furnace outlet denitration spray gun 62, and the atomizing steam pipe 65 is connected to the steam source.

[0032] Specifically, each secondary air duct denitration spray gun 61 and each furnace outlet denitration spray gun 62 are connected to an independent reductant storage tank 64 through a reductant delivery pipe 63. The reductant storage tank connected to the furnace outlet denitration spray gun 62 is not shown in the figure. Each secondary air duct denitration spray gun 61 and each furnace outlet denitration spray gun 62 are connected to an atomizing steam pipe 65. The steam source is a steam source.

[0033] The upper end of the coal feeding pipe 70 is connected to the coal supply source for entering the furnace, and the lower end is connected to the dense phase zone.

[0034] Reference below Figure 1-Figure 3 The operation process of the selective non-catalytic reduction denitrification system 1 for a circulating fluidized bed boiler is described.

[0035] First, the charge coal is supplied to the furnace 10 through the coal supply pipe 70, and the charge coal is burned in the furnace 10 to generate flue gas.

[0036] When the boiler is running at a low load, only the secondary air duct denitration spray gun 61 is used, the on-off valve 51 arranged on the lower secondary air duct 50 is closed, the reducing agent in the reducing agent storage tank 64 is transported to the secondary air duct denitration spray gun 61 through the reducing agent delivery pipe 63, and steam is input into the atomizing steam pipe 65 to allow the steam to enter the secondary air duct denitration spray gun 61. With steam as the atomizing medium, the steam and the reducing agent are mixed in the secondary air duct denitration spray gun 61, and the steam atomized wind is sprayed from the secondary air duct denitration spray gun 61 into the furnace 10. Since the on-off valve 51 is closed to isolate the air, the oxygen content in the flue gas around the secondary air duct denitration spray gun 61 in the furnace 10 can be significantly reduced. After the steam is atomized and sprayed through the secondary air duct denitration spray gun 61, it enters the furnace 10. The atomized steam and the coal first react with water gas. The carbon monoxide produced by the reaction will enhance the ability of the denitration reducing agent to reduce nitrogen oxides, reduce the concentration of nitrogen oxides, and thus achieve the purpose of denitration.

[0037] When the boiler is running at high load, only the furnace outlet denitrification spray gun 62 is used, and the reducing agent enters into the furnace outlet denitrification spray gun 62 through the reducing agent delivery pipe 63, and at the same time, the steam enters into the furnace outlet denitrification spray gun 62 through the atomizing steam pipe 65. With steam as the atomizing medium, the steam and the reducing agent are mixed in the furnace outlet denitrification spray gun 62, and the steam atomized wind is sprayed from the furnace outlet denitrification spray gun 62 into the furnace outlet flue 30, whereby a denitrification reaction occurs to reduce the concentration of nitrogen oxides at the furnace outlet.

[0038] For example, when the inlet flue gas temperature of the separator 20 is greater than 750 degrees Celsius, it is considered to be a high-load operation, and when the inlet flue gas temperature of the separator 20 is less than 750 degrees Celsius, it is considered to be a low-load operation.

[0039] The denitrified air enters the separator 20 through the furnace outlet flue 30 at the top of the furnace 10. The coarse particles are separated and captured by the separator 20, enter the return device 23, and re-enter the furnace 10 through the return pipe 24 to continue burning. The denitrified fine particles and air enter the separator outlet flue 21 through the top of the separator 20 and are discharged.

[0040] According to the circulating fluidized bed boiler selective non-catalytic reduction denitration system 1 of the embodiment of the utility model, by setting the secondary air duct denitration spray gun 61 and the furnace outlet denitration spray gun 62, when the boiler is running at high load, only the furnace outlet denitration spray gun 62 is used, and when the boiler is running at low load, only the secondary air duct denitration spray gun 61 is used, so that the denitration reaction is carried out in different positions in a targeted manner according to the furnace operating temperature.

[0041] Furthermore, since the optimal temperature for the denitrification reaction cannot be reached when the boiler is running at a low load, the on-off valve 51 is provided. When the boiler is running at a low load and the secondary air duct denitrification spray gun 61 is used, the on-off valve 51 is closed, and the lower secondary air duct 50 can be closed to prevent the lower secondary air duct 50 from continuing to supply air into the furnace 10, thereby reducing the oxygen concentration in the dense phase area of ​​the furnace 10, reducing the oxygen concentration in the environment of the denitrification reaction, and improving the denitrification effect.

[0042] In addition, by using the atomizing steam pipe 65 to supply atomizing steam to the secondary air duct denitrification spray gun 61 and the furnace outlet denitrification spray gun 62, the atomizing steam and the reducing agent can be mixed in the spray gun first, reducing the influence of oxygen in the furnace on the denitrification reaction and further improving the denitrification effect.

[0043] Furthermore, by connecting the secondary air duct denitrification spray gun 61 and the coal feeding pipe 70 to the dense phase zone, when using the secondary air duct denitrification spray gun 61 for denitrification, water vapor and coal can first react with water gas. The carbon monoxide produced by the reaction helps to reduce nitrogen oxides, thereby reducing the concentration of nitrogen oxides, further facilitating the improvement of the denitrification effect during low-load operation.

[0044] Therefore, the selective non-catalytic reduction denitration system 1 for a circulating fluidized bed boiler according to the embodiment of the utility model has the advantages of good denitration effect and the like.

[0045] The selective non-catalytic reduction denitration system 1 for a circulating fluidized bed boiler according to a specific embodiment of the utility model will be described below with reference to the accompanying drawings.

[0046] In some specific embodiments of the present invention, Figure 1-Figure 3 As shown, the selective non-catalytic reduction denitrification system 1 for a circulating fluidized bed boiler according to an embodiment of the utility model includes a furnace 10, a separator 20, a furnace outlet flue 30, an upper secondary air duct 40, a lower secondary air duct 50, a secondary air duct denitrification spray gun 61, a furnace outlet denitrification spray gun 62 and a coal feeding pipe 70.

[0047] Specifically, the circulating fluidized bed boiler selective non-catalytic reduction denitration system 1 includes a medium load state, a high load state, a low load state and a startup state. In the low load state or the startup state, the secondary air duct denitration spray gun 61 is running and the on-off valve 51 is closed. In the medium load state or the high load state, the furnace outlet denitration spray gun 62 is running and the on-off valve 51 is opened. In this way, the circulating fluidized bed boiler selective non-catalytic reduction denitration system 1 can switch the operating state, and adopt different denitration methods when the boiler is in the high load and low load operating states, respectively, so as to improve the denitration effect in a targeted manner.

[0048] More specifically, the circulating fluidized bed boiler selective non-catalytic reduction denitration system 1 also includes a separator inlet flue gas temperature detection device, and the separator inlet flue gas temperature detection device is suitable for detecting the inlet flue gas temperature of the separator. Specifically, when the inlet flue gas temperature of the separator 20 is higher than 750 degrees, the circulating fluidized bed boiler selective non-catalytic reduction denitration system 1 switches to the high load state, and when the inlet flue gas temperature of the separator 20 is lower than 750 degrees, the circulating fluidized bed boiler selective non-catalytic reduction denitration system 1 switches to the low load state. In this way, it is possible to determine whether the boiler is in a high load state or a low load state by detecting the inlet flue gas temperature of the separator 20, and control the switching of the secondary air duct denitration spray gun 61 and the furnace outlet denitration spray gun 62 and the opening and closing of the on-off valve 51 by detecting the inlet flue gas temperature of the separator 20, so as to select different denitration methods in a targeted manner and further improve the denitration effect.

[0049] Figure 1 and Figure 2 The following is a diagram showing a selective non-catalytic reduction denitration system 1 for a circulating fluidized bed boiler according to some examples of the present invention. Figure 1 and Figure 2As shown, there are multiple separators 20 and each separator 20 is provided with a separator outlet flue 21 and is connected to the dense phase zone through a return device 23 and a return pipe 24, there are multiple furnace outlet flues 30, multiple furnace outlet flues 30 are connected to the furnace 10 and are respectively connected to multiple separators 20, there are multiple upper secondary air ducts 40 and are arranged at intervals along the circumference of the furnace 10, there are multiple lower secondary air ducts 50 and are arranged at intervals along the circumference of the furnace 10, each lower secondary air duct 50 is connected to an on-off valve 51, there are multiple secondary air duct denitration spray guns 61 and are connected to multiple lower secondary air ducts 50 one by one, and there are multiple furnace outlet denitration spray guns 62 and are connected to multiple furnace outlet flues 30 one by one. In this way, the operating number of the secondary air duct denitration spray guns 61 and the furnace outlet denitration spray guns 62 can be adjusted to facilitate achieving the best denitration effect.

[0050] Specifically, Figure 1 and Figure 2 As shown, the separator outlet flue 21 is connected to a flue gas component detection device 22 for detecting the concentration of nitrogen oxides in the flue gas. Specifically, the number of operations of the secondary air duct denitration spray gun 61 and the furnace outlet denitration spray gun 62 or the amount of reductant sprayed can be controlled according to the concentration of nitrogen oxides detected by the flue gas component detection device 22, for example, the number of operations of the spray guns can be increased when the concentration of nitrogen oxides is high, and the number of operations of the spray guns can be reduced when the concentration of nitrogen oxides is low, so as to achieve the best denitration effect.

[0051] More specifically, Figure 1 and Figure 2 As shown, a header 80 is provided outside the furnace 10, the header 80 is connected to the air source, and the upper ends of the plurality of upper secondary air ducts 40 and the upper ends of the plurality of lower secondary air ducts 50 are all connected to the header 80. In this way, the header 80 can be used to uniformly supply air to the plurality of upper secondary air ducts 40 and the plurality of lower secondary air ducts 50, so that the airflow is distributed to the plurality of upper secondary air ducts 40 and the plurality of lower secondary air ducts 50 through the header 80, so that the plurality of upper secondary air ducts 40 and the plurality of lower secondary air ducts 50 can supply air into the furnace 10.

[0052] Advantageously, if Figure 1-Figure 3 As shown, the lower end of the lower secondary air duct 50 and the lower end of the coal feeding pipe 70 are located at the same height on the furnace 10 and are alternately arranged in the circumferential direction of the furnace 10. Since the secondary air duct denitration lance 61 is connected to the lower end of the lower secondary air duct 50, the outlet of the secondary air duct denitration lance 61 and the outlet of the lower secondary air duct 50 can be close to the outlet of the coal feeding pipe 70, so that the steam sprayed by the secondary air duct denitration lance 61 and the coal discharged from the coal feeding pipe 70 react with water gas to produce carbon monoxide.

[0053] More advantageously, if Figure 1 and Figure 2As shown, the furnace 10 includes a straight section 11 and a contraction section 12, the contraction section 12 is located below the straight section 11, and the dense phase area is formed in the contraction section 12. This makes it easier for each reactant to be fully mixed in the dense phase area, further improving the denitration effect.

[0054] Optionally, the reducing agent in the reducing agent storage tank 64 is urea solution or ammonia water. In this way, urea or ammonia water can be used for reduction and denitration reaction, thereby reducing costs while ensuring the reduction effect.

[0055] Furthermore, the mass concentration of the reducing agent in the reducing agent storage tank 64 is less than or equal to 40%. Here, the mass concentration of the reducing agent sprayed into the furnace 10 is preferably 5-20%. This makes it easier to adjust the denitration effect.

[0056] Other structures and operations of the circulating fluidized bed boiler selective non-catalytic reduction denitrification system 1 according to the embodiment of the utility model are known to ordinary technicians in the field and will not be described in detail here.

[0057] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0058] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A circulating fluidized bed boiler selective non-catalytic reduction denitrification system, characterized in that: include: A furnace, wherein the lower portion of the furnace has a dense phase zone; A separator, wherein the upper end of the separator is provided with a separator outlet flue and the lower end of the separator is connected with the dense phase zone through a return device and a return pipe; A furnace outlet flue, wherein the furnace outlet flue is connected to an upper portion of the furnace and an upper portion of the separator respectively; An upper secondary air duct, wherein the upper end of the upper secondary air duct is connected to the air source and the lower end of the upper secondary air duct is connected to the dense phase zone; A lower secondary air duct, wherein the upper end of the lower secondary air duct is connected to the air source and the lower end is connected to the dense phase zone, the lower end of the lower secondary air duct is located below the lower end of the upper secondary air duct, and the lower secondary air duct is connected to an on-off valve; A secondary air duct denitration spray gun, one end of which is connected to the lower end of the lower secondary air duct and the other end of which is connected to the reducing agent storage tank via a reducing agent delivery pipe, an atomizing steam pipe is provided on the circumference of the secondary air duct denitration spray gun, and the atomizing steam pipe is connected to a steam source; A furnace outlet denitration spray gun, one end of which is connected to the furnace outlet flue and the other end of which is connected to the reducing agent storage tank via a reducing agent delivery pipe. An atomizing steam pipe is provided on the circumference of the furnace outlet denitration spray gun, and the atomizing steam pipe is connected to a steam source; A coal feeding pipe, wherein the upper end of the coal feeding pipe is connected to a coal supply source for entering the furnace and the lower end of the coal feeding pipe is connected to the dense phase zone.

2. The circulating fluidized bed boiler selective non-catalytic reduction denitration system according to claim 1, characterized in that: The circulating fluidized bed boiler selective non-catalytic reduction denitrification system includes a medium load state, a high load state, a low load state and a startup state. In the low load state or the startup state, the secondary air duct denitrification spray gun operates and the on-off valve is closed to isolate the air. In the medium load state or the high load state, the furnace outlet denitrification spray gun operates and the on-off valve is opened.

3. The selective non-catalytic reduction denitration system for circulating fluidized bed boiler according to claim 1, characterized in that: It also includes a separator inlet smoke temperature detection device, which is suitable for detecting the inlet smoke temperature of the separator.

4. The circulating fluidized bed boiler selective non-catalytic reduction denitration system according to claim 1, characterized in that: There are multiple separators and each of the separators is provided with a separator outlet flue and is connected to the dense phase zone through the return device and the return pipe. There are multiple furnace outlet flues and multiple furnace outlet flues are connected to the furnace and are respectively connected to multiple separators. There are multiple upper secondary air ducts and are arranged at intervals along the circumference of the furnace. There are multiple lower secondary air ducts and are arranged at intervals along the circumference of the furnace. Each lower secondary air duct is connected with an on-off valve. There are multiple secondary air duct denitrification spray guns and are connected one-to-one with multiple lower secondary air ducts. There are multiple furnace outlet denitrification spray guns and are connected one-to-one with multiple furnace outlet flues.

5. The circulating fluidized bed boiler selective non-catalytic reduction denitration system according to claim 4, characterized in that: A header is provided outside the furnace, the header is connected to the gas source, and the upper ends of the plurality of upper secondary air ducts and the upper ends of the plurality of lower secondary air ducts are all connected to the header.

6. The selective non-catalytic reduction denitration system for a circulating fluidized bed boiler according to any one of claims 1 to 5, characterized in that: The separator outlet flue is connected to a flue gas component detection device for detecting the concentration of nitrogen oxides in the flue gas.

7. The selective non-catalytic reduction denitration system for a circulating fluidized bed boiler according to any one of claims 1 to 5, characterized in that: The lower end of the lower secondary air duct and the lower end of the coal feeding pipe are located at the same height on the furnace and are alternately arranged in the circumferential direction of the furnace.

8. The circulating fluidized bed boiler selective non-catalytic reduction denitration system according to any one of claims 1 to 5, characterized in that: The reducing agent in the reducing agent storage tank is urea solution or ammonia water.

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