Self-operated direct-fired pyrolysis ammonia spraying and mixing integrated device and control method thereof

Abstract

The invention belongs to the technical field of flue gas denitration treatment, and particularly relates to a self-operated direct-fired pyrolysis ammonia spraying and mixing integrated device and a control method thereof. Flue gas is heated in a direct combustion and inner cylinder wall preheating mode, the indirect heating mode of a traditional heat exchanger is avoided, the heat transfer efficiency is improved, energy waste is reduced, and the operation cost is reduced; and a direct combustion heating mode is adopted, so that the heating power can be quickly adjusted to cope with the change of flue gas flow or components. And the urea pyrolysis device is arranged, so that a urea solution can be efficiently pyrolyzed to generate ammonia gas, combustion conditions can be adjusted according to actual requirements, and the stability and high efficiency of the pyrolysis process are ensured. The device not only solves the problems of complex system, low response speed, low thermal efficiency, uneven ammonia gas distribution and the like in the traditional SCR denitration system, but also improves the overall performance of the system through optimization design, and has remarkable technical advantages and application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of flue gas denitration treatment, and in particular relates to a self-powered direct-combustion pyrolysis and ammonia spraying mixing integrated device and a control method thereof. Background Art

[0002] In industrial production, flue gas denitrification is an important environmental protection task. Selective catalytic reduction (SCR) technology is one of the most widely used flue gas denitrification methods. Traditional SCR denitrification systems usually require complex equipment layout and long process flow, which not only increases equipment investment and floor space, but may also lead to low system operation efficiency and increased maintenance costs.

[0003] In traditional SCR denitrification systems, flue gas usually needs to pass through a special preheating device to reach the optimal working temperature of the catalyst. However, this preheating process has some shortcomings: 1. Complex system: Traditional systems usually contain multiple components, such as heat exchangers, pipes, etc., which increase the complexity and maintenance cost of the system; 2. Slow response speed: When the flue gas flow or composition changes, it is difficult for traditional systems to adjust quickly, resulting in a decrease in denitrification efficiency; 3. Low thermal efficiency: Traditional flue gas heating methods often use indirect heating, such as using heat exchangers, which has low heat transfer efficiency and leads to energy waste; 4. Uneven distribution of ammonia: Due to the lack of an effective mixing device, ammonia is often not evenly distributed when entering the flue gas flow, affecting the denitrification effect.

[0004] Therefore, there is an urgent need for a flue gas direct combustion ammonia injection mixing device to solve the problems of complex system, slow response speed, low thermal efficiency of flue gas treatment and uneven distribution of ammonia in the flue gas in the existing SCR denitrification system.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to overcome the above-mentioned shortcomings of the prior art and to provide a self-powered direct-fired pyrolysis and ammonia spraying integrated mixing device and a control method thereof.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] On the one hand, the present invention provides a self-powered direct-fired pyrolysis and ammonia spraying and mixing integrated device, comprising a flue gas direct-fired heating cylinder, the flue gas direct-fired heating cylinder comprising an inner cylinder, an outer cylinder which is sleeved outside the inner cylinder and whose top is fixed on the outside of the inner cylinder, a flue gas inlet is provided at the upper end of the outer cylinder, a gap is provided between the bottom of the outer cylinder and the bottom of the inner cylinder for the flue gas to enter the inner cylinder, a first burner for heating the flue gas at the bottom of the inner cylinder is fixedly provided at the closed bottom of the outer cylinder, a flue gas outlet connected to the SCR denitrification reactor is provided at the top of the inner cylinder, an ammonia spraying and mixing device for uniformly mixing ammonia with the flue gas is also provided at the flue gas outlet, and the ammonia spraying and mixing device is connected to a urea pyrolysis device; a temperature control regulating device for controlling the ammonia flow rate according to the ammonia temperature is also provided at the portion where the urea pyrolysis device is connected to the ammonia spraying and mixing device. Specifically, the ammonia spray mixing device includes an annular plate connected to the urea pyrolysis device, and an annular porous plate fixed at the flue gas outlet and allowing ammonia to be evenly sprayed into the flue gas direct combustion heating cylinder. The annular plate and the annular porous plate are fixedly connected to form an ammonia containing chamber.

[0009] Specifically, the annular porous plate is provided with a plurality of air holes for uniformly spraying the ammonia gas in the ammonia gas containing chamber into the direct-fired heating cylinder.

[0010] Furthermore, the diameter of the pores on the annular porous plate close to the urea pyrolysis device gradually decreases, and the diameter of the pores on the annular porous plate away from the urea pyrolysis device gradually increases.

[0011] Specifically, the urea pyrolysis device includes a cylindrical pyrolysis chamber connected to the top and an ammonia spray mixing device, a second fire tube is fixedly provided at the bottom of the cylindrical pyrolysis chamber, one end of which is used for spraying fire to pyrolyze urea, and the other end extends out of the cylindrical pyrolysis chamber and is connected to a second burner, and a urea solution injection port is provided on the side wall of the cylindrical pyrolysis chamber and above the second fire tube.

[0012] Furthermore, the second burner is provided with a first interface for accessing natural gas and a second interface for accessing air.

[0013] Specifically, the temperature control and adjustment device comprises a conical gas outlet arranged at the ammonia outlet of the urea pyrolysis device, wherein the conical gas outlet has a closed end close to the ammonia spraying and mixing device and an open end away from the ammonia spraying and mixing device;

[0014] The temperature control and adjustment device also includes a temperature-controlled deformable metal disc fixedly mounted on the air inlet passage of the ammonia injection mixing device, a sliding rod fixedly mounted at the center of the metal disc which causes displacement through temperature-controlled deformation of the metal disc, a conical plug matched with the conical air outlet fixedly mounted at the end of the sliding rod away from the metal disc, and which approaches and moves away from the conical air outlet through the displacement of the sliding rod; the flow rate of ammonia entering the ammonia injection mixing device is controlled by the conical plug approaching and moving away from the conical air outlet; the metal disc is composed of multiple layers of metal sheets with different thermal expansion coefficients, which can directly convert thermal energy into mechanical energy, causing the sliding rod to produce a linear displacement, thereby causing the conical plug to approach or move away from the conical air outlet.

[0015] Furthermore, the metal disc is fixed in the air intake passage of the ammonia injection mixing device through a fixed bracket, and a sliding bracket for supporting the sliding of the sliding rod is fixed in the air intake passage of the ammonia injection mixing device.

[0016] Specifically, the first burner includes a first fire tube with one end fixed at the bottom of the outer tube and the other end extending into the bottom of the inner tube. One end of the first fire tube is also provided with a first interface for connecting to natural gas and a second interface for connecting to compressed air; the first interface is also provided with an air valve for controlling the size of natural gas, and the second interface is provided with an air compression pump.

[0017] On the other hand, the present invention provides a control method for the self-powered direct-fired pyrolysis and ammonia spraying integrated device as described above, wherein the self-powered direct-fired pyrolysis and ammonia spraying integrated device is provided with a control system, wherein the control system controls the flow rate of urea in the urea pyrolysis device according to the flow rate of the flue gas at the flue gas inlet or the content of nitrogen, and at the same time, the control system controls the flow rate of the flue gas at the flue gas inlet, and controls the flow rates of natural gas and air in the first burner to control the combustion temperature. The specific control method is as follows:

[0018] First, the control system controls the combustion temperature in the urea pyrolysis device to reach the temperature for pyrolyzing urea, and then the control system controls the urea pyrolysis device to start pyrolyzing urea to generate ammonia. The ammonia and the flue gas after combustion are mixed to form a first mixed gas, and then the first mixed gas is led to the ammonia spraying mixing device. A temperature control regulating device is provided in the channel between the urea pyrolysis device and the ammonia spraying mixing device to automatically control the flow rate of the first mixed gas according to the temperature of the first mixed gas. At the same time, the control system controls the first burner to mix the natural gas and air and burn them at the bottom of the inner cylinder, and heat the side wall of the inner cylinder at the same time.

[0019] Then, the control system controls the flow rate of the flue gas to be denitrated at the flue gas inlet according to the temperature of the flue gas outlet. When the flue gas to be denitrated passes through the channel between the inner tube and the outer tube, it is heated to a certain temperature by the inner tube wall, and then flows through the bottom of the inner tube. The temperature of the flue gas to be denitrated is heated to a temperature suitable for the reaction of the SCR denitration reactor by the first burner. At the same time, the flue gas generated after the combustion of the first burner is mixed with the flue gas to be denitrated to form a second mixed gas;

[0020] Finally, when the second mixed gas flows through the ammonia injection mixing device, the first mixed gas and the second mixed gas are evenly mixed to form a third mixed gas, and the third mixed gas is passed from the flue gas outlet to the SCR denitration reactor for subsequent denitration reaction.

[0021] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0022] The present invention heats the flue gas by direct combustion and preheating the inner cylinder wall, avoiding the indirect heating method of the traditional heat exchanger and improving the heat transfer efficiency. This method reduces energy waste and reduces operating costs. The self-powered direct-combustion pyrolysis ammonia spray mixing integrated device adopts the design of inner and outer cylinders, with a compact structure and high integration, reducing multiple components (such as heat exchangers, pipelines, etc.) in the traditional system, thereby reducing the complexity of the system and the volume of the device. The ammonia spray mixing device forms an ammonia containing cavity through an annular plate and an annular porous plate, so that ammonia can be evenly sprayed into the inner cylinder. The pores on the annular porous plate are designed to gradually decrease in diameter near the urea pyrolysis device and gradually increase in diameter away from the urea pyrolysis device. This gradual design helps to further improve the uniform mixing of ammonia with the flue gas after being injected into the inner cylinder, thereby improving the efficiency of the denitrification reaction. At the same time, the temperature control adjustment device automatically controls the ammonia flow rate according to the ammonia temperature to ensure uniform mixing of ammonia and flue gas.

[0023] The direct combustion heating method is adopted, which can quickly adjust the heating power to cope with changes in flue gas flow or composition. This rapid response capability ensures the stability and efficiency of the denitrification process, and can maintain a good denitrification effect even when the working conditions change, and greatly saves natural gas; the urea pyrolysis device can efficiently pyrolyze the urea solution to generate ammonia, and the combustion conditions can be adjusted according to actual needs to ensure the stability and efficiency of the pyrolysis process.

[0024] In summary, the self-powered direct-fired pyrolysis and ammonia spraying integrated mixing device and its control method provided by the present invention not only solve the problems of complex system, slow response speed, low thermal efficiency and uneven ammonia distribution in the traditional SCR denitrification system, but also improve the overall performance of the system through optimized design, and has significant technical advantages and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the present invention.

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0027] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0028] Figure 2 is a side view of the present invention;

[0029] Figure 3 for Figure 2 AA section view;

[0030] Figure 4 It is a front view of the present invention;

[0031] Figure 5 for Figure 4 BB section view;

[0032] Figure 6 It is a cross-sectional view of the temperature control and adjustment device of the present invention.

[0033] Among them: 1 is a flue gas direct combustion heating cylinder; 11 is an inner cylinder; 111 is a flue gas outlet; 12 is an outer cylinder; 121 is a flue gas inlet; 13 is a first burner; 14 is a first fire tube; 2 is an ammonia spray mixing device; 21 is an annular plate; 22 is an annular porous plate; 3 is a urea pyrolysis device; 31 is a cylindrical pyrolysis chamber; 32 is a second burner; 33 is a second fire tube; 34 is a urea solution injection port; 4 is a temperature control regulating device; 41 is a conical air outlet; 42 is a metal disc; 43 is a sliding rod; 44 is a conical plug; 45 is a fixed bracket; 46 is a sliding bracket. DETAILED DESCRIPTION

[0034] Here, exemplary embodiments will be described in detail, and examples thereof are shown in the accompanying drawings. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention as detailed in the appended claims.

[0035] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0036] Example

[0037] See also Figure 1-6 As shown, the present embodiment provides a self-powered direct-fired pyrolysis and ammonia spraying and mixing integrated device, comprising a flue gas direct-fired heating cylinder 1, the flue gas direct-fired heating cylinder 1 comprising an inner cylinder 11, an outer cylinder 12 which is sleeved outside the inner cylinder 11 and whose top is fixed on the outer side of the inner cylinder 11, a flue gas inlet 121 is provided at the upper end of the outer cylinder 12, a gap is provided between the bottom of the outer cylinder 12 and the bottom of the inner cylinder 11 for the flue gas to enter the inner cylinder 11, a first burner 13 for heating the flue gas at the bottom of the inner cylinder 11 is fixedly provided at the closed bottom of the outer cylinder 12, a flue gas outlet 111 connected to the SCR denitration reactor is provided at the top of the inner cylinder 11, an ammonia spraying and mixing device 2 for uniformly mixing ammonia with the flue gas is also provided at the flue gas outlet 111, the ammonia spraying and mixing device 2 is connected to a urea pyrolysis device 3; a temperature control regulating device 4 for controlling the ammonia flow rate according to the ammonia temperature is also provided at the portion where the urea pyrolysis device 3 is connected to the ammonia spraying and mixing device 2.

[0038] Specifically, the ammonia spray mixing device 2 includes an annular plate 21 connected to the urea pyrolysis device 3, and an annular porous plate 22 fixed at the flue gas outlet 111 and allowing ammonia to be evenly sprayed into the flue gas direct combustion heating cylinder 1. The annular plate 21 and the annular porous plate 22 are fixedly connected to form an ammonia containing chamber.

[0039] Specifically, the annular porous plate 22 is provided with a plurality of air holes for uniformly spraying the ammonia gas in the ammonia gas containing chamber into the direct-fired heating cylinder 1 .

[0040] Furthermore, the diameter of the pores on the annular porous plate 22 close to the urea pyrolysis device 3 gradually decreases, and the diameter of the pores on the annular porous plate 22 away from the urea pyrolysis device 3 gradually increases.

[0041] Specifically, the urea pyrolysis device 3 includes a cylindrical pyrolysis chamber 31 connected to the top and the ammonia spray mixing device 2, and a second fire tube 33 is fixedly provided at the bottom of the cylindrical pyrolysis chamber 31, one end of which is used for spraying fire to pyrolyze urea, and the other end extends out of the cylindrical pyrolysis chamber 31 and is connected to the second burner 32. A urea solution injection port 34 is provided on the side wall of the cylindrical pyrolysis chamber 31 and above the second fire tube 33.

[0042] Furthermore, the second burner 32 is provided with a first interface for accessing natural gas and a second interface for accessing air.

[0043] Specifically, the temperature control and adjustment device 4 includes a conical gas outlet 41 arranged at the ammonia outlet of the urea pyrolysis device 3, and the conical gas outlet 41 is closed at one end close to the ammonia spray mixing device 2, and is open at one end away from the ammonia spray mixing device 2;

[0044] The temperature control regulating device 4 also includes a metal disc 42 which is temperature-controlled and deformable and fixedly mounted on the air inlet passage of the ammonia injection mixing device 2. A sliding rod 43 which is displaced by the temperature-controlled deformation of the metal disc 42 is fixedly mounted at the center of the metal disc 42. A conical plug 44 which is adapted to the conical air outlet 41 and can be moved closer to and away from the conical air outlet 41 by the displacement of the sliding rod 43 is fixedly mounted at one end of the sliding rod 43 which is away from the metal disc 42. The conical plug 44 is moved closer to and away from the conical air outlet 41 to control the flow rate of ammonia entering the ammonia injection mixing device 2.

[0045] Further, the metal disc 42 is fixed in the air inlet passage of the ammonia injection mixing device 2 through a fixing bracket 45, and a sliding bracket 46 for supporting the sliding rod 43 to slide is fixed in the air inlet passage of the ammonia injection mixing device 2; see Figure 6 shown.

[0046] Specifically, the first burner 13 includes a first fire tube 14 with one end fixed at the bottom of the outer tube 12 and the other end extending into the bottom of the inner tube 11. One end of the first fire tube 14 is also provided with a first interface for connecting to natural gas and a second interface for connecting to compressed air; the first interface is also provided with an air valve for controlling the size of natural gas, and the second interface is provided with an air compression pump.

[0047] This embodiment provides a control method for a self-powered direct-fired pyrolysis and ammonia spraying integrated device, wherein the self-powered direct-fired pyrolysis and ammonia spraying integrated device is provided with a control system, wherein the control system controls the flow rate of urea in the urea pyrolysis device 3 according to the flow rate of the flue gas at the flue gas inlet 121 or the content of nitrogen, and controls the flow rates of natural gas and air in the first burner 13 to control the combustion temperature. The specific control method is as follows:

[0048] First, the control system controls the flow of natural gas and air in the second burner 32 of the urea pyrolysis device 3, so that the temperature of the gas ejected from the second fire tube 33 reaches the temperature of 400°C for pyrolyzing urea. Then, the control system controls the amount of urea solution sprayed from the urea solution spray port 34 into the cylindrical pyrolysis chamber 31 according to the flow of the flue gas or the content of nitrogen at the flue gas inlet 121, and simultaneously starts to pyrolyze urea to produce ammonia. The ammonia and the flue gas after combustion are mixed to form a first mixed gas, and then the mixed gas is passed to the ammonia spray mixing device 2 through the temperature control regulating device 4. The temperature control device 4 adjusts the distance between the conical plug 44 and the conical outlet 41 according to the temperature of the first mixed gas, thereby adjusting the flow rate of the first mixed gas entering the ammonia injection mixing device 2. The higher the temperature, the greater the distance between the conical plug 44 and the conical outlet 41, and vice versa. At the same time, the control system controls the first burner 13 to mix the natural gas and air and burn them at the bottom of the inner tube 11. The flue gas ejected from the first fire tube 14 generates a high temperature greater than 750°C, and heats the side wall of the inner tube 11 at the same time. See Figure 3As shown (the arrows in the figure show the flow directions of the flue gas to be denitrated, the first mixed flue gas, the second mixed flue gas, and the third mixed flue gas);

[0049] Then, the control system controls the flow rate of the flue gas to be denitrated (temperature is 80-160°C) at the flue gas inlet 121 according to the temperature of the flue gas outlet 111. When the flue gas to be denitrated passes through the channel between the inner tube 11 and the outer tube 12, it is heated to a certain temperature by the side wall of the inner tube 11, and then flows through the bottom of the inner tube 11. The flue gas ejected by the first fire tube 14 heats the temperature of the flue gas to be denitrated to a temperature suitable for the reaction of the SCR denitration reactor (temperature 230°C). At the same time, the flue gas generated after the combustion of the first burner 13 is mixed with the flue gas to be denitrated to form a second mixed gas (temperature is 230°C);

[0050] Finally, when the second mixed gas flows through the ammonia injection mixing device 2, the first mixed gas is uniformly sprayed out from the annular porous plate 22, and is uniformly mixed with the second mixed gas to form a third mixed gas, and the third mixed gas is passed from the flue gas outlet 111 to the SCR denitration reactor for subsequent denitration reaction; see Figure 3 , 5 As shown (the arrows in the figure indicate the flow directions of the flue gas to be denitrified, the first mixed flue gas, the second mixed flue gas, and the third mixed flue gas).

[0051] The control system controls the flow rate of urea in the urea pyrolysis device 3 according to the flow rate of the flue gas at the flue gas inlet 121 or the flow rate of the nitrogen content;

[0052] When the flow rate or nitrogen content of the flue gas decreases, the control system controls the amount of urea solution sprayed from the urea solution inlet 3 to decrease. Since the heat generated by the combustion in the second fire tube is constant, the energy consumed by reducing urea is small, which causes the temperature of the first mixed gas to rise. When the first mixed gas passes through the temperature control regulating device 4, the metal disc 42 is deformed, causing the slide rod 43 to drive the conical plug 44 to move away from the ammonia spray mixing device 2, that is, the distance between the conical plug 44 and the conical air outlet 41 increases, and at the same time, the amount of the first mixed gas entering the ammonia spray mixing device 2 is increased. At this time, the temperature of the newly generated first mixed gas decreases, and when it passes through the metal disc 42 again, the metal disc 42 returns to its original shape, causing the slide rod 43 to drive the conical plug 44 to move toward the ammonia spray mixing device 2, that is, the distance between the conical plug 44 and the conical air outlet 41 decreases, and at the same time, the amount of the first mixed gas entering the ammonia spray mixing device 2 is also reduced;

[0053] When the flow rate or nitrogen content of the flue gas increases, the control system controls the amount of urea solution sprayed from the urea solution inlet 3 to increase. Since the heat generated by the combustion in the second fire tube is constant, the increase in urea consumes more energy, which causes the temperature of the first mixed gas to drop. When the first mixed gas passes through the temperature control regulating device 4, the metal disc 42 deforms and returns to its original state, causing the slide rod 43 to drive the conical plug 44 to move toward the ammonia injection mixing device 2, that is, the distance between the conical plug 44 and the conical air outlet 41 is reduced, and at the same time, the amount of the first mixed gas entering the ammonia injection mixing device 2 is reduced. At this time, the first mixed gas remaining in the cylindrical pyrolysis chamber 31 continues to be heated to increase its temperature. When passing through the metal disc 42 again, the metal disc 42 is heated and deformed, causing the slide rod 43 to drive the conical plug 44 to move away from the ammonia injection mixing device 2, that is, the distance between the conical plug 44 and the conical air outlet 41 is increased, and at the same time, the amount of the first mixed gas entering the ammonia injection mixing device 2 is also increased.

[0054] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0055] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A self-powered direct-fired pyrolysis and ammonia spraying and mixing integrated device, characterized in that: The invention comprises a flue gas direct combustion heating cylinder (1), wherein the flue gas direct combustion heating cylinder (1) comprises an inner cylinder (11), an outer cylinder (12) which is sleeved outside the inner cylinder (11) and whose top is fixed to the outside of the inner cylinder (11), a flue gas inlet (121) is provided at the upper end of the outer cylinder (12), a gap is provided between the bottom of the outer cylinder (12) and the bottom of the inner cylinder (11) so that flue gas can enter the inner cylinder (11), and a gas inlet (121) is fixedly provided at the bottom of the closed outer cylinder (12) for heating flue gas at the bottom of the inner cylinder (11). The inner tube (11) is provided with a first burner (13) for producing ammonia gas, a flue gas outlet (111) connected to an SCR denitration reactor is provided at the top of the inner tube (11), an ammonia spraying and mixing device (2) for uniformly mixing ammonia gas with the flue gas is also provided at the flue gas outlet (111), the ammonia spraying and mixing device (2) is connected to a urea pyrolysis device (3); a temperature control device (4) for controlling the flow rate of ammonia gas according to the temperature of ammonia gas is also provided at the connection portion between the urea pyrolysis device (3) and the ammonia spraying and mixing device (2).

2. According to claim 1, the self-powered direct-fired pyrolysis and ammonia spraying integrated mixing device is characterized in that: The ammonia spray mixing device (2) comprises an annular plate (21) connected to the urea pyrolysis device (3), and an annular porous plate (22) fixedly arranged at the flue gas outlet (111) and allowing ammonia to be uniformly sprayed into the flue gas direct combustion heating cylinder (1); the annular plate (21) and the annular porous plate (22) are fixedly connected to form an ammonia containing chamber.

3. According to claim 2, the self-powered direct-fired pyrolysis and ammonia spraying integrated mixing device is characterized in that: The annular porous plate (22) is provided with a plurality of air holes for uniformly spraying the ammonia gas in the ammonia gas containing chamber into the direct-fired heating cylinder (1).

4. According to claim 3, the self-powered direct-fired pyrolysis and ammonia spraying integrated mixing device is characterized in that: The diameter of the pores on the annular porous plate (22) close to the urea pyrolysis device (3) gradually decreases, and the diameter of the pores on the annular porous plate (22) gradually away from the urea pyrolysis device (3) gradually increases.

5. According to claim 1, the self-powered direct-fired pyrolysis and ammonia spraying integrated mixing device is characterized in that: The urea pyrolysis device (3) comprises a cylindrical pyrolysis chamber (31) connected to the top with an ammonia spray mixing device (2); a second fire tube (33) is fixedly arranged at the bottom of the cylindrical pyrolysis chamber (31), one end of which is used for spraying fire to pyrolyze urea, and the other end of which extends out of the cylindrical pyrolysis chamber (31) and is connected to a second burner (32); a urea solution spray inlet (34) is arranged on the side wall of the cylindrical pyrolysis chamber (31) and above the second fire tube (33).

6. The self-powered direct-fired pyrolysis and ammonia spraying and mixing integrated device according to claim 5 is characterized in that: The second burner (32) is provided with a first interface for receiving natural gas, and a second interface for receiving air.

7. The self-powered direct-fired pyrolysis and ammonia spraying and mixing integrated device according to claim 1 is characterized in that: The temperature control and adjustment device (4) comprises a conical gas outlet (41) arranged at the ammonia outlet of the urea pyrolysis device (3), wherein the conical gas outlet (41) is closed at one end close to the ammonia spray mixing device (2) and is open at one end away from the ammonia spray mixing device (2); The temperature control and adjustment device (4) also includes a metal disc (42) that is temperature-controlled and deformable and fixedly mounted on the air inlet passage of the ammonia spray mixing device (2). A sliding rod (43) is fixedly mounted at the center of the metal disc (42) and is displaced by the temperature-controlled deformation of the metal disc (42). A conical plug (44) that is adapted to the conical air outlet (41) and is moved closer to and further away from the conical air outlet (41) is fixedly mounted at one end of the sliding rod (43) away from the metal disc (42). The conical plug (44) is moved closer to and further away from the conical air outlet (41), thereby controlling the flow rate of ammonia entering the ammonia spray mixing device (2).

8. The self-powered direct-fired pyrolysis and ammonia spraying integrated mixing device according to claim 7 is characterized in that: The metal disc (42) is fixed in the air intake passage of the ammonia injection mixing device (2) via a fixed bracket (45), and a sliding bracket (46) for supporting the sliding of the sliding rod (43) is fixed in the air intake passage of the ammonia injection mixing device (2).

9. The self-powered direct-fired pyrolysis and ammonia spraying and mixing integrated device according to claim 1 is characterized in that: The first burner (13) comprises a first fire tube (14) with one end fixed to the bottom of the outer tube (12) and the other end extending into the bottom of the inner tube (11); one end of the first fire tube (14) is also provided with a first interface for connecting to natural gas and a second interface for connecting to compressed air; the first interface is also provided with an air valve for controlling the amount of natural gas, and the second interface is provided with an air compression pump.

10. A control method for a self-powered direct-fired pyrolysis and ammonia spraying integrated mixing device according to any one of claims 1 to 9, characterized in that: The self-powered direct-fired pyrolysis and ammonia spraying integrated device is provided with a control system, which controls the flow rate of urea in the urea pyrolysis device (3) according to the flow rate of the flue gas at the flue gas inlet (121) or the content of nitrogen, and controls the flow rates of natural gas and air in the first burner (13) to control the combustion temperature. The specific control method is as follows: First, the control system controls the combustion temperature in the urea pyrolysis device (3) to reach the temperature for pyrolyzing urea, and then the control system controls the urea pyrolysis device (3) to start pyrolyzing urea to generate ammonia, and the ammonia and the flue gas after combustion are mixed to form a first mixed gas, which is passed to the ammonia spraying mixing device (2). A temperature control regulating device (4) is provided in the channel between the urea pyrolysis device (3) and the ammonia spraying mixing device (2) to automatically control the flow rate of the first mixed gas according to the temperature of the first mixed gas; at the same time, the control system controls the first burner (13) to mix natural gas and air and burn them at the bottom of the inner cylinder (11), and at the same time heats the side wall of the inner cylinder (11); Then, the control system controls the flow rate of the flue gas to be denitrated at the flue gas inlet (121) according to the temperature of the flue gas outlet (111). When the flue gas to be denitrated passes through the channel between the inner tube (11) and the outer tube (12), it is heated to a certain temperature by the inner tube wall, and then flows through the bottom of the inner tube (11). The temperature of the flue gas to be denitrated is heated to a temperature suitable for the reaction of the SCR denitration reactor by the first burner (13). At the same time, the flue gas generated after combustion by the first burner (13) is mixed with the flue gas to be denitrated to form a second mixed gas; Finally, when the second mixed gas flows through the ammonia injection mixing device (2), the first mixed gas and the second mixed gas are evenly mixed to form a third mixed gas, and the third mixed gas is passed from the flue gas outlet (111) to the SCR denitration reactor for subsequent denitration reaction.

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