Ammonia spraying and mixing device for urea pyrolysis

Abstract

The utility model belongs to the technical field of flue gas denitration treatment, and particularly relates to a urea pyrolysis ammonia spraying and mixing device. The ammonia gas can be uniformly sprayed into the flue gas direct combustion heating cylinder body through the annular porous plate arranged at the flue gas outlet; and the diameters of the air holes in the annular porous plate are designed to be gradually reduced close to the urea pyrolysis device and gradually increased far away from the urea pyrolysis device, so that the gradual change design is beneficial to further improving uniform mixing of ammonia gas and flue gas, and the subsequent denitration efficiency is improved. Natural gas and air are sprayed out from the upper end of the fire barrel after being mixed and combusted in the gas combustor, a stable high-temperature environment is provided, and a urea solution enters the barrel-shaped pyrolysis chamber and is rapidly pyrolyzed to generate ammonia gas in the high-temperature environment. According to the device, by optimizing the positions and the connection modes of all the components, the maintenance difficulty is reduced, the service life of the device is prolonged, and the device further has the advantages of being compact in structure, reasonable in design, easy to install and maintain and the like.

Description

Technical Field

[0001] The utility model belongs to the technical field of flue gas denitrification treatment, and particularly relates to a urea pyrolysis and ammonia spraying mixing device. Background Art

[0002] With the increasingly stringent environmental regulations, nitrogen oxides (NO x ) control has become an important issue. Urea pyrolysis ammonia injection technology is a denitrification technology widely used in coal-fired power plants, industrial boilers and other fields. It generates ammonia by pyrolysis of urea solution and sprays it evenly into the flue gas to react with nitrogen oxides in the flue gas to produce a selective catalytic reduction reaction (SCR), thereby achieving NO x In traditional urea pyrolysis systems, urea solution is usually sprayed directly into the high-temperature area for pyrolysis, and the generated ammonia then enters the flue gas flow.

[0003] However, this method has some shortcomings: 1) Low pyrolysis efficiency: The residence time of the urea solution in the high-temperature zone is limited, the pyrolysis is incomplete, and some urea is not fully converted into ammonia, affecting the overall denitrification effect; 2) Uneven distribution of ammonia: Due to the lack of an effective mixing device, the distribution of ammonia in the flue gas is often not uniform, resulting in reduced denitrification efficiency; 3) High energy consumption: In order to ensure that the urea solution can be completely pyrolyzed, a higher temperature and a longer heating time are required, which increases the energy consumption of the system.

[0004] Therefore, there is an urgent need for a urea pyrolysis ammonia spray mixing device to allow the ammonia after pyrolysis to be evenly mixed with the flue gas, so as to facilitate the subsequent SCR reactor to perform denitrification reaction.

[0005] In view of this, the present utility model is proposed. Utility Model Content

[0006] The purpose of the utility model is to overcome the shortcomings of the above-mentioned prior art and provide a urea pyrolysis and ammonia spraying mixing device.

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

[0008] A urea pyrolysis and ammonia spraying mixing device comprises a flue gas direct-fired heating cylinder, the flue gas direct-fired heating cylinder comprising a flue gas inlet and a flue gas outlet, the flue gas outlet being connected to a urea pyrolysis device via an ammonia spraying mixing device, the ammonia spraying mixing device comprising an outer cylinder communicated with the urea pyrolysis device, and an annular porous plate fixed at the flue gas outlet for uniformly spraying ammonia into the flue gas direct-fired heating cylinder, the outer cylinder and the annular porous plate being fixedly connected to form an ammonia containing chamber; a temperature control regulating device for controlling the ammonia flow rate according to the ammonia temperature is further provided at the portion where the urea pyrolysis device is connected to the outer cylinder.

[0009] Specifically, the temperature control and adjustment device includes a conical gas outlet provided at the ammonia outlet of the urea pyrolysis device, wherein the conical gas outlet has a closed end close to the ammonia spray mixing device and an open end away from the ammonia spray mixing device;

[0010] The temperature control and adjustment device also includes a metal disc that is temperature-controlled and deformable and is fixed to the air inlet channel of the outer cylinder. A sliding rod is fixed at the center of the metal disc, which is displaced by the temperature-controlled deformation of the metal disc. A conical plug that is adapted to the conical air outlet is fixed at the end of the sliding rod away from the metal disc, and is moved closer to and away from the conical air outlet by the displacement of the sliding rod. The flow rate of ammonia entering the ammonia injection mixing device is controlled by the approach and distance of the conical plug. 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.

[0011] Specifically, the sliding rod is screwed to the conical plug.

[0012] Specifically, the metal disc is fixed in the air inlet passage of the outer cylinder through a fixing bracket.

[0013] Specifically, a sliding bracket for supporting the sliding rod to slide is fixedly provided in the air inlet passage of the outer cylinder.

[0014] Specifically, the urea pyrolysis device includes a cylindrical pyrolysis chamber connected to the top with an ammonia spray mixing device. A fire tube is fixed 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 gas burner. A urea solution injection port is provided on the side wall of the cylindrical pyrolysis chamber and above the fire tube. High-pressure air and urea solution are mixed and enter the cylindrical pyrolysis chamber from the urea solution injection port.

[0015] Specifically, the gas burner is further provided with a first interface for receiving natural gas and a second interface for receiving air; after the natural gas and air are mixed and burned in the gas burner, they are ejected from the upper end of the fire tube, and the high temperature causes the urea solution to decompose into ammonia in the cylindrical pyrolysis chamber.

[0016] 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.

[0017] Specifically, the diameters of the pores on the annular porous plate close to the urea pyrolysis device gradually decrease, and the diameters of the pores on the annular porous plate away from the urea pyrolysis device gradually increase.

[0018] Compared with the prior art, the technical solution provided by the utility model has the following beneficial effects:

[0019] 1. Improve ammonia distribution uniformity: Ammonia can be evenly sprayed into the flue gas direct-fired heating cylinder through the annular porous plate set at the flue gas outlet; 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 and flue gas, thereby improving the subsequent denitrification efficiency.

[0020] 2. Automatically adjust the ammonia flow rate according to the stability of ammonia: When ammonia passes through the temperature control device, the metal disc in the device is deformed appropriately by the ammonia temperature, driving the conical plug to move relative to the conical air outlet, controlling the flow of ammonia entering the ammonia spray mixing device, thereby controlling the temperature of the ammonia spraying into the flue gas outlet in the ammonia spray mixing device.

[0021] 3. Efficient urea pyrolysis process: Urea solution enters the cylindrical pyrolysis chamber through the urea solution injection port and rapidly pyrolyzes to generate ammonia under high temperature. Natural gas and air are mixed and burned in the gas burner and then ejected from the upper end of the fire tube, providing a stable high-temperature environment that is conducive to the complete pyrolysis of the urea solution. The design of the fire tube allows the urea solution to be fully heated, improving the pyrolysis efficiency, reducing the residual urea that is not completely pyrolyzed, and ensuring the quality and yield of the formed ammonia.

[0022] 4. Reduced energy consumption: By optimizing the design of the pyrolysis chamber and ammonia spray mixing device, the pyrolysis efficiency and uniformity of ammonia distribution are improved, unnecessary heat loss is reduced, and the overall energy consumption of the system is reduced. This not only saves energy costs but also meets environmental protection requirements.

[0023] 5. Enhanced system stability: The device forms an ammonia chamber through the outer cylinder and the annular porous plate, which acts as a static pressure box, ensuring that the mixture of ammonia and air can be evenly injected into the flue gas direct combustion heating cylinder under constant pressure. This design enhances the stability and reliability of the system and reduces performance degradation caused by pressure fluctuations.

[0024] 6. Simplified operation and maintenance: The device has a compact structure, reasonable design, and is easy to install and maintain. By optimizing the position and connection method of each component, the operation process is simplified, the maintenance difficulty is reduced, and the service life of the equipment is extended.

[0025] In summary, the urea pyrolysis and ammonia spraying mixing device provided by the utility model not only solves the problems of low pyrolysis efficiency, uneven ammonia distribution and high energy consumption in traditional systems, but also improves the overall performance of the system through optimized design, and has significant technical advantages and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are incorporated into and constitute a part of this specification and, together with the description, are used to explain the principles of the present invention.

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 It is a three-dimensional structural schematic diagram of the utility model;

[0029] Figure 2 It is a side view of the utility model;

[0030] Figure 3 for Figure 2 AA section view;

[0031] Figure 4 It is an enlarged schematic diagram of the temperature control and adjustment device of the present invention.

[0032] Among them: 1 is the flue gas direct combustion heating cylinder; 11 is the flue gas inlet; 12 is the flue gas outlet; 2 is the ammonia injection mixing device; 21 is the outer cylinder; 22 is the annular porous plate; 3 is the urea pyrolysis device; 31 is the fire cylinder; 32 is the cylindrical pyrolysis chamber; 33 is the urea solution injection port; 4 is the temperature control adjustment device; 41 is the sliding rod; 42 is the conical plug; 43 is the conical air outlet; 44 is the fixed bracket; 45 is the metal disc; 46 is the sliding bracket. DETAILED DESCRIPTION

[0033] Exemplary embodiments will now be described in detail, with examples shown in the accompanying drawings. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present invention. Instead, they are merely examples consistent with certain aspects of the present invention as detailed in the appended claims.

[0034] 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 with reference to the accompanying drawings and embodiments.

[0035] Example

[0036] See also Figure 1-3As shown, this embodiment provides a urea pyrolysis and ammonia spraying mixing device, including a flue gas direct-fired heating cylinder 1, the flue gas direct-fired heating cylinder 1 including a flue gas inlet 11 and a flue gas outlet 12, the flue gas outlet 12 is connected to a urea pyrolysis device 3 through an ammonia spraying mixing device 2, the ammonia spraying mixing device 2 includes an outer cylinder 21 connected to the urea pyrolysis device 3, and a ring-shaped porous plate 22 fixed at the flue gas outlet 12 and allowing ammonia to be evenly sprayed into the flue gas direct-fired heating cylinder 1, the outer cylinder 21 and the ring-shaped porous plate 22 are fixedly connected to form an ammonia containing chamber; the portion where the urea pyrolysis device 3 is connected to the outer cylinder 21 is further provided with a temperature control regulating device 4 for controlling the ammonia flow rate according to the temperature of the ammonia.

[0037] Specifically, the temperature control device 4 includes a conical gas outlet 43 provided at the ammonia outlet of the urea pyrolysis device 3. The conical gas outlet 43 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.

[0038] The temperature control and adjustment device 4 also includes a metal disc 45 that is deformable under temperature control and fixed to the air inlet channel of the outer cylinder 21. A sliding rod 41 is fixed at the center of the metal disc 45, which is displaced by the temperature control deformation of the metal disc 45. The end of the sliding rod 41 away from the metal disc 45 is fixed with a conical plug 42 that is adapted to the conical air outlet 43 and approaches and moves away from the conical air outlet 43 by the displacement of the sliding rod 41. The flow rate of ammonia entering the ammonia injection mixing device 2 is controlled by the approach and distance of the conical plug 42. Figure 4 shown.

[0039] Specifically, the sliding rod 41 is screwed to the conical plug 42 .

[0040] Specifically, the metal disc 45 is fixed in the air inlet passage of the outer cylinder 21 through a fixing bracket 44.

[0041] Specifically, a sliding bracket 46 for supporting the sliding rod 41 is fixed in the air inlet passage of the outer cylinder 21 .

[0042] Specifically, the urea pyrolysis device 3 includes a cylindrical pyrolysis chamber 32 connected to the top and the ammonia injection mixing device 2. A fire tube 31 is fixed at the bottom of the cylindrical pyrolysis chamber 32, one end of which is used for spraying fire to pyrolyze urea, and the other end extends out of the cylindrical pyrolysis chamber 32 and is connected to the gas burner. A urea solution injection port 33 is provided on the side wall of the cylindrical pyrolysis chamber 32 and above the fire tube 31.

[0043] Specifically, the gas burner is further provided with a first interface for accessing natural gas and a second interface for accessing air.

[0044] 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 .

[0045] Specifically, the diameters of the pores on the annular porous plate 22 close to the urea pyrolysis device 3 gradually decrease, and the diameters of the pores on the annular porous plate 22 away from the urea pyrolysis device 3 gradually increase.

[0046] This embodiment also provides a method for using a urea pyrolysis and ammonia spraying mixing device, which is specifically as follows:

[0047] The gas burner uses natural gas as fuel and generates hot air with a temperature greater than 400°C through combustion with natural wind. The hot air enters the cylindrical pyrolysis chamber 32. The pyrolysis section is provided with a urea solution injection port 33. After the urea solution and high-pressure air are mixed, they enter the cylindrical pyrolysis chamber 32 from the urea solution injection port 33 and are converted into ammonia by high temperature. The gas formed by the mixture of ammonia and air passes through the temperature control device 4 and enters the ammonia containing chamber of the ammonia injection mixing device 2; when the ammonia temperature is too high, the metal disc 45 deforms, driving the slide rod 41 close to the urea pyrolysis device 3, thereby driving the conical plug 42 away from the conical air outlet 43, increasing the flow rate of ammonia; when the ammonia temperature drops, the metal disc 45 resets, driving the slide rod 41 away from the urea pyrolysis device 3, thereby driving the conical plug 42 close to the conical air outlet 43, reducing the flow rate of ammonia entering the ammonia injection mixing device.

[0048] The ammonia holding chamber is formed by the annular outer cylinder 21 and the annular porous plate 22. The annular space acts as a static pressure box. The mixed gas of ammonia and air is injected into the flue gas direct-fired heating cylinder 1 at high speed through the porous horizontal direction of the annular porous plate 22. After being evenly mixed with the flue gas in the flue gas direct-fired heating cylinder 1, an ammonia / flue gas mixed gas is formed. The mixed gas enters the SCR reactor for denitrification reaction. Under the action of the catalyst, ammonia and nitrogen oxides undergo redox reaction to generate nitrogen and water, thereby achieving the purpose of purifying the flue gas.

[0049] The amount of urea solution injected from the urea solution injection port 33 is controlled by an electric valve. The flue gas inlet 11 is provided with a flow meter for detecting the flue gas flow rate and nitrogen concentration. The electric valve and the flow meter are controlled by a controller. The flow meter identifies the flue gas flow rate or nitrogen concentration and controls the electric valve through the controller to increase or decrease the amount of urea solution injected from the urea solution injection port 33.

[0050] When the flow meter detects that the flue gas flow rate increases or the nitrogen concentration decreases, the electric valve reduces the amount of urea solution injected from the urea solution injection port 33. At this time, since the heat generated by the fire cylinder in the urea pyrolysis device 3 is constant, the temperature of the generated ammonia will increase (the amount of urea solution decreases, the decomposition absorbs less heat, and the temperature increases). When the ammonia passes through the temperature control device 4, due to the increase in the ammonia temperature, the metal disc 45 is deformed, and at the same time, the slide rod 41 is driven to move away from the ammonia injection mixing device 2, resulting in an increase in the distance between the conical plug 42 and the conical air outlet 43, and ultimately the amount of ammonia passing through the temperature control device 4 is increased, and the heating time of ammonia in the cylindrical pyrolysis chamber 32 is reduced. After the temperature drops, the metal disc 45 slowly returns to its original shape and drives the slide rod 41 to move toward the ammonia injection mixing device 2, resulting in a decrease in the distance between the conical plug 42 and the conical air outlet 43, and ultimately the amount of ammonia passing through the temperature control device 4 is reduced.

[0051] When the flow meter detects an increase in the flue gas flow rate or an increase in the nitrogen concentration, the electric valve increases the amount of urea solution injected from the urea solution injection port 33. At this time, since the heat generated by the flame in the urea pyrolysis device 3 is constant, the temperature of the generated ammonia gas will decrease (the amount of urea solution increases, the heat absorption increases, and the temperature decreases). When the ammonia gas passes through the temperature control device 4, due to the decrease in ammonia temperature, the metal disc 45 returns to its original shape and at the same time drives the slide rod 41 to move toward the ammonia injection and mixing device 2, resulting in a decrease in the distance between the tapered plug 42 and the tapered air outlet 43, and ultimately reduces the amount of ammonia gas passing through the temperature control device 4. The heating time of ammonia gas in the cylindrical pyrolysis chamber 32 will increase. After the temperature rises, the metal disc 45 is deformed by the heat and drives the slide rod 41 to move away from the ammonia injection and mixing device 2, resulting in an increase in the distance between the tapered plug 42 and the tapered air outlet 43, and ultimately increases the amount of ammonia gas passing through the temperature control device 4.

[0052] The above description is merely a specific embodiment of the present invention, which enables those skilled in the art to 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 may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0053] It should be understood that the present invention is not limited to the above description and that various modifications and changes can be made without departing from the scope of the present invention. The scope of the present invention is limited only by the appended claims.

Claims

1. A urea pyrolysis and ammonia spraying mixing device, characterized in that: The invention comprises a flue gas direct-fired heating cylinder (1), the flue gas direct-fired heating cylinder (1) comprising a flue gas inlet (11) and a flue gas outlet (12), the flue gas outlet (12) being connected to a urea pyrolysis device (3) via an ammonia spraying and mixing device (2), the ammonia spraying and mixing device (2) comprising an outer cylinder (21) communicating with the urea pyrolysis device (3), and an annular porous plate (22) fixedly arranged at the flue gas outlet (12) and configured to uniformly spray ammonia into the flue gas direct-fired heating cylinder (1), the outer cylinder (21) and the annular porous plate (22) being fixedly connected to form an ammonia accommodating chamber; and a temperature control regulating device (4) for controlling the ammonia flow rate according to the temperature of the ammonia is further provided at the portion where the urea pyrolysis device (3) is connected to the outer cylinder (21).

2. The urea pyrolysis and ammonia spraying mixing device according to claim 1, characterized in that: The temperature control and adjustment device (4) comprises a conical gas outlet (43) provided at the ammonia outlet of the urea pyrolysis device (3), wherein the conical gas outlet (43) 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 (45) that is deformable and temperature-controlled and fixed to the air inlet channel of the outer cylinder (21). A sliding rod (41) is fixed at the center of the metal disc (45) and is displaced by the temperature-controlled deformation of the metal disc (45). A conical plug (42) that is adapted to the conical air outlet (43) and is moved closer to and away from the conical air outlet (43) by the displacement of the sliding rod (41) is fixed at one end of the sliding rod (41) away from the metal disc (45); the flow rate of ammonia entering the ammonia injection mixing device (2) is controlled by the approach and distance of the conical plug (42).

3. The urea pyrolysis and ammonia spraying mixing device according to claim 2, characterized in that: The sliding rod (41) is screwed to the conical plug (42).

4. The urea pyrolysis and ammonia spraying mixing device according to claim 2, characterized in that: The metal disc (45) is fixed in the air inlet passage of the outer cylinder (21) via a fixing bracket (44).

5. The urea pyrolysis and ammonia spraying mixing device according to claim 2, characterized in that: A sliding bracket (46) for supporting the sliding of the sliding rod (41) is fixedly provided in the air inlet passage of the outer cylinder (21).

6. The urea pyrolysis and ammonia spraying mixing device according to claim 1, characterized in that: The urea pyrolysis device (3) comprises a cylindrical pyrolysis chamber (32) connected to the top with an ammonia spray mixing device (2); a fire tube (31) is fixedly provided at the bottom of the cylindrical pyrolysis chamber (32), 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 (32) and is connected to a gas burner; a urea solution spray inlet (33) is provided on the side wall of the cylindrical pyrolysis chamber (32) and above the fire tube (31).

7. The urea pyrolysis and ammonia spraying mixing device according to claim 6, characterized in that: The gas burner is further provided with a first interface for accessing natural gas and a second interface for accessing air.

8. The urea pyrolysis and ammonia spraying mixing device according to claim 1, characterized in that: The annular porous plate (22) is provided with a plurality of air holes for uniformly spraying the ammonia in the ammonia containing chamber into the flue gas direct combustion heating cylinder (1).

9. The urea pyrolysis and ammonia spraying mixing device according to claim 8, characterized in that: The diameters of the pores on the annular porous plate (22) close to the urea pyrolysis device (3) gradually decrease, and the diameters of the pores on the annular porous plate (22) away from the urea pyrolysis device (3) gradually increase.

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