Melamine fluidized bed reactor

Abstract

The utility model belongs to the technical field of chemical production, and particularly relates to a melamine fluidized bed reactor. The melamine fluidized bed reactor comprises a fluidized bed main body, the lower end of the fluidized bed main body is connected with a micron bubble generator, the micron bubble generator is connected with a mixer, a Y-shaped premixer is arranged at the bottom of the mixer, the upper end of the fluidized bed main body is connected with a primary separation mechanism, and a discharge port is formed in the top of the primary separation mechanism. The discharge port is connected with the secondary separation mechanism, the discharge port is higher than an inlet of the secondary separation mechanism, the bottom of the secondary separation mechanism is provided with a pipeline for refluxing to the fluidized bed main body, the pipeline for refluxing to the fluidized bed main body is obliquely inserted into the fluidized bed main body, and the top of the secondary separation mechanism is provided with a product discharge port. And the conveying device is used for conveying the reacted product mixed gas to the next working section. According to the melamine fluidized bed reactor disclosed by the utility model, materials are uniformly distributed, the separation of a catalyst and a product is realized, and the quality of a reaction product is ensured.

Description

Technical Field

[0001] The utility model belongs to the technical field of chemical production, and specifically relates to a melamine fluidized bed reactor. Background Art

[0002] Melamine is an important organic chemical intermediate, widely used in wood processing, plastics, coatings, water reducers, papermaking, adhesives, textiles, leather, electrical appliances, medicine, flame retardants and other industries. The production of melamine usually uses urea as raw material. Under the action of certain temperature, pressure and catalyst, urea is decomposed and repolymerized to form melamine in a fluidized bed reactor. The heat required for the reaction is generally provided by a molten salt system, and the carrier gas is mostly a mixed gas of ammonia and carbon dioxide that has been purified, cooled and preheated by boosting pressure.

[0003] There are four main production processes for melamine: high-pressure method, medium-pressure method, low-pressure method and normal-pressure method. Among them, the low-pressure urea decomposition method is one of the common processes. The reaction temperature is usually around 380°C, and the reaction pressure is normal pressure or slightly higher than atmospheric pressure. However, in the low-pressure production process of melamine, the reactor has many defects: first, affected by the gas distributor at the bottom of the fluidized bed, the carrier gas bubbles are easy to merge and cause "short circuit", which leads to poor fluidization effect of the fluidized bed; in addition, because the catalyst is in a fluid state during the reaction stage, it is easy to cause catalyst wear and catalyst backflow during the shutdown stage, which affects the reaction efficiency and the difficulty of starting.

[0004] CN209501637U discloses a novel one-step melamine fluidized bed, which mainly arranges four groups of heaters A, B, C, and D with the same structure in sequence from the middle of the fluidized bed tank downward. Each heater consists of two connecting seats, a cavity is provided in the connecting seat, a group of heating pipes are connected between the two connecting seats, the two ends of the heating pipes are connected to the cavity in the connecting seat, and the connecting seat is also connected to a nozzle connected to the cavity. The angle between the two adjacent groups of the four groups of heaters is 45 degrees, and they are arranged vertically and horizontally in the middle and lower part of the fluidized bed. This design effectively increases the heat exchange area, can reduce the temperature of molten salt, and save energy; the heater has no welds, prevents molten salt leakage, reduces maintenance and parking, extends the production cycle, increases annual output, and reduces production costs. However, the heater group spans both sides of the tank, which causes certain obstacles to the distribution uniformity and flow of materials in the fluidized bed. If the material is unevenly distributed in the fluidized bed, it may cause low heating efficiency in some areas. At the same time, materials may accumulate on the surface of the heater, further reducing the heating efficiency.

[0005] Therefore, comprehensively speaking, it is of great significance to optimize the fluidized bed design, improve the gas distributor and the internal structure of the reactor, ensure uniform distribution of materials, and solve the problem of catalyst backflow. Utility Model Content

[0006] The purpose of the utility model is to overcome the above-mentioned defects of the prior art and provide a melamine fluidized bed reactor. By designing the fluidized bed, the uniform distribution of materials is ensured, and auxiliary mechanisms and two-stage separation mechanisms are set to achieve separation of catalysts and products, thereby ensuring the quality of the reaction products.

[0007] The melamine fluidized bed reactor of the utility model comprises a fluidized bed body, a primary separation mechanism and a secondary separation mechanism. The lower end of the fluidized bed body is connected with a micron bubble generator, the micron bubble generator is connected with a mixer, a Y-shaped premixer is arranged at the bottom of the mixer, a urea feed port is arranged at the bottom of the Y-shaped premixer, the Y-shaped premixer is connected with an ammonia mixed gas pipeline, the upper end of the fluidized bed body is connected with the primary separation mechanism, a discharge port is arranged at the top of the primary separation mechanism, the discharge port is connected with the secondary separation mechanism, the height of the discharge port is higher than the inlet of the secondary separation mechanism, a pipeline for reflux to the fluidized bed body is arranged at the bottom of the secondary separation mechanism, the pipeline for reflux to the fluidized bed body is obliquely inserted into the fluidized bed body, and a product discharge port is arranged at the top of the secondary separation mechanism for conveying the product mixed gas after the reaction to the next working section.

[0008] Preferably, the fluidized bed body is provided with a feed plate, a gas distribution plate, an auxiliary mechanism, and a catalyst feed port in sequence from bottom to top, and the pipeline inlet connecting the fluidized bed body and the secondary separation mechanism is located at the upper part of the auxiliary mechanism.

[0009] Preferably, the auxiliary mechanism includes a spiral shaft, a support plate, and a rotating position. The spiral shaft is located at the center of the support plate to support the rotation of the auxiliary mechanism. Two rotating positions are arranged at the positions where the two ends of the spiral shaft are connected to the fluidized bed body. The rotating positions are controlled by a motor to rotate the auxiliary mechanism.

[0010] Preferably, six spray guns are arranged on the feed plate, jackets are arranged on the gas distribution plate at positions corresponding to the spray guns, and a gas inlet is arranged on one side wall of the gas distribution plate to be connected to an ammonia mixed gas pipeline.

[0011] Preferably, the jacket is located at the periphery of the spray gun, the height of the jacket outlet is lower than the height of the spray gun outlet, and the height of the jacket outlet is higher than the height of the gas distribution plate body.

[0012] Preferably, the primary separation mechanism includes blades and a support rod. The primary separation mechanism is a conical structure. A support rod is arranged in the vertical direction at the center of the conical structure. The support rod is provided with blades. The blades start from the top of the support rod and are arranged spirally downward along the support rod.

[0013] Preferably, the bottom of the secondary separation mechanism refluxes to the pipeline of the fluidized bed body, and is provided with a sewage outlet and a rotating baffle, and the sewage outlet is located above the rotating baffle.

[0014] Preferably, the ammonia mixed gas pipeline is provided with a branch connected to the micron bubble generator.

[0015] Preferably, three support frames are evenly welded around the outer wall of the bottom of the fluidized bed body to support the entire device.

[0016] The working principle of the utility model is:

[0017] The molten urea and the heated and gasified ammonia mixture are preliminarily mixed in a Y-type premixer, and then enter the mixer and the micron bubble generator in turn to enter the fluidized bed body. The mixed liquid in the micron bubble generator is mixed with the ammonia mixture, and the gas molecules and liquid molecules collide and diffuse to ensure that the bubbles are evenly mixed in the liquid. After entering the fluidized bed body, the mixed liquid is sprayed in by a spray gun. In order to ensure the stability of the mixed liquid spraying, a gas distribution plate is set. The remaining ammonia mixture is used as a carrier gas to carry the atomized mixed liquid to react with the catalyst. The catalyst particles are in a suspended state under the action of the mixture and move randomly in the fluidized bed reactor. In the reaction stage, the catalyst particles collide continuously, and the small particle catalyst moves with the airflow to the primary separation mechanism. The primary separation mechanism is provided with a support rod and a spiral blade. During the rotation of the airflow along the blade, the solid particles are acted on by gravity and fall down. After sinking into the fluidized bed body, the gas enters the secondary separation mechanism through the discharge port. Under the dual effects of centrifugal force and rotating airflow, the remaining small particle powder is separated and refluxed to the fluidized bed body through the bottom pipe of the secondary separation mechanism to continue to participate in the reaction. The gas after two-stage separation is transported from the top of the secondary separation mechanism to the next section, thereby ensuring the quality of the product. At the same time, during the reaction process and the shutdown stage, in order to prevent the catalyst backflow caused by the reduction of gas flow rate, an auxiliary mechanism is arranged in the fluidized bed body. The auxiliary mechanism is placed vertically during normal operation and does not hinder the reaction. Once an emergency occurs, the auxiliary mechanism can be rotated 90° to form a partition on the upper part of the feed spray gun to separate the raw material and the catalyst. Even if the catalyst backflows, it will fall on the auxiliary mechanism due to gravity and will not cause damage to the spray gun, etc., thereby ensuring the stability and safety of the device operation.

[0018] The fluidized bed body in the utility model adopts a conventional heating method, and a coil heat exchange tube bundle is arranged in the fluidized bed body; the molten salt in the molten salt tank enters the molten salt furnace to be heated, and the fuel and air from outside the boundary area enter the molten salt furnace, and the molten salt flows from bottom to top through the furnace in the furnace tube, and the coal burns in the furnace to release heat, and the high-temperature flue gas transfers the heat to the molten salt in the furnace tube. The temperature of the heated molten salt is maintained at 430-440°C, and then enters the coil heat exchange tube bundle arranged in the fluidized bed body to provide heat for the material reaction in the fluidized bed.

[0019] Compared with the prior art, the utility model has the following beneficial effects:

[0020] (1) The melamine fluidized bed reactor of the utility model ensures that the urea and ammonia mixed gas are fully mixed before entering the fluidized bed body through the design of the micron bubble generator and the mixer, and the bubbles are evenly distributed in the liquid, thereby improving the reaction efficiency. The spray gun and the gas distribution plate are used to further improve the uniformity of the material.

[0021] (2) The melamine fluidized bed reactor of the utility model utilizes centrifugal force and gravity to effectively separate larger particles, thereby ensuring the continuity and efficiency of the reaction and improving the purity and quality of the product.

[0022] (3) The melamine fluidized bed reactor of the utility model, the auxiliary mechanism design in the fluidized bed body, and the sewage outlet and rotating partition design at the bottom of the secondary separation mechanism realize the separation of raw materials and catalysts, prevent the backflow of catalysts from damaging equipment such as spray guns, and facilitate regular cleaning and maintenance to ensure the long-term stable operation of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of the melamine fluidized bed reactor described in the utility model;

[0024] Figure 2 It is a schematic diagram of the auxiliary mechanism of the melamine fluidized bed reactor described in the utility model;

[0025] Figure 3 It is an enlarged view of the melamine fluidized bed reactor A described in the utility model;

[0026] Figure 4 It is an enlarged view of the B portion of the melamine fluidized bed reactor described in the present utility model;

[0027] Figure 5 It is an enlarged view of the spray gun at position B of the melamine fluidized bed reactor described in the utility model.

[0028] In the figure: 1. fluidized bed body; 2. primary separation mechanism; 3. secondary separation mechanism; 4. catalyst feed port; 5. support frame; 6. Y-type premixer; 7. urea feed port; 8. ammonia mixed gas pipeline; 9. feed plate; 10. mixer; 11. micron bubble generator; 12. gas distribution plate; 13. auxiliary mechanism; 14. discharge port; 15. product discharge port; 201. blade; 202. support rod; 301. sewage outlet; 302. rotating partition; 901. spray gun; 902. jacket; 1301. spiral shaft; 1302. support plate; 1303. rotating position. DETAILED DESCRIPTION

[0029] The utility model will be further described below in conjunction with the accompanying drawings.

[0030] like Figure 1-Figure 5 As shown, the melamine fluidized bed reactor comprises a fluidized bed body 1, a primary separation mechanism 2, and a secondary separation mechanism 3. The upper end of the fluidized bed body 1 is connected to the primary separation mechanism 2. The top of the primary separation mechanism 2 is provided with a discharge port 14, and the discharge port 14 is connected to the secondary separation mechanism 3. The bottom of the secondary separation mechanism 3 is provided with a pipeline for reflux to the fluidized bed body 1. The top of the secondary separation mechanism 3 is provided with a product discharge port 15.

[0031] The bottom of the fluidized bed body 1 is connected to a micron bubble generator 11, the micron bubble generator 11 is connected to a mixer 10, a Y-shaped premixer 6 is provided at the bottom of the mixer 10, the Y-shaped premixer 6 is provided with a urea feed port 7, and the Y-shaped premixer 6 is connected to an ammonia mixed gas pipeline 8.

[0032] The fluidized bed body 1 is provided with a feed plate 9, a gas distribution plate 12, an auxiliary mechanism 13, and a catalyst feed port 4 in sequence from bottom to top. The pipeline inlet connecting the fluidized bed body 1 and the secondary separation mechanism 3 is located on the upper part of the auxiliary mechanism 13.

[0033] The auxiliary mechanism 13 includes a spiral shaft 1301, a support plate 1302, and a rotating position 1303. The spiral shaft 1301 is located at the center of the support plate 1302 to support the rotation of the auxiliary mechanism 13. Two rotating positions 1303 are arranged at the positions where the two ends of the spiral shaft 1301 are connected to the fluidized bed body 1. The rotating position 1303 is controlled by a motor to rotate the auxiliary mechanism 13.

[0034] The feed plate 9 is provided with a spray gun 901 , the gas distribution plate 12 is provided with a jacket 902 at a position corresponding to the spray gun 901 , and a gas inlet is provided on one side wall of the gas distribution plate 12 to connect with the ammonia mixed gas pipeline 8 .

[0035] The jacket 902 is located outside the spray gun 901 , the outlet height of the jacket 902 is lower than the outlet height of the spray gun 901 , and the outlet height of the jacket 902 is higher than the height of the gas distribution plate 12 .

[0036] The primary separation mechanism 2 includes blades 201 and a support rod 202. The primary separation mechanism 2 is a conical structure. A support rod 202 is arranged in the vertical direction at the center of the conical structure. Blades 201 are arranged on the support rod 202. The blades 201 start from the top of the support rod 202 and are arranged in a spiral downward along the support rod 202.

[0037] The bottom of the secondary separation mechanism 3 refluxes to the pipeline of the fluidized bed body 1 , and is provided with a sewage outlet 301 and a rotating baffle 302 . The sewage outlet 301 is located above the rotating baffle 302 .

[0038] The ammonia mixed gas pipeline 8 is provided with a branch connected to the micron bubble generator 11 .

[0039] Three support frames 5 are evenly welded around the outer wall of the bottom of the fluidized bed body 1 to support the entire device.

[0040] During operation, the above melamine fluidized bed reactor operates as follows:

[0041] (1) The molten urea is pumped to the urea feed port 7, the ammonia mixed gas is heated to 380°C by a carrier gas preheater, and then introduced into the fluidized bed reactor in three ways. One way is mixed with the molten urea and enters the Y-type premixer 6 for initial mixing with the molten urea and preliminary heating to prevent the temperature difference from being too large and affecting the subsequent reaction effect;

[0042] (2) The urea and ammonia mixed gas enters the mixer 10 and the micron bubble generator 11 in sequence. In the micron bubble generator 11, the mixed liquid and the ammonia mixed gas are further mixed, and the gas molecules and the liquid molecules collide and diffuse to ensure that the bubbles are evenly mixed in the liquid;

[0043] (3) The mixed liquid is sprayed into the fluidized bed body 1 through six spray guns 901 on the feed plate 9. In order to ensure the stability of the mixed liquid spraying, a gas distribution plate 12 is set. The remaining ammonia mixed gas is used as a carrier gas to carry the atomized mixed liquid to react with the catalyst. The catalyst particles are in a suspended state under the action of the mixed material and move randomly in the fluidized bed reactor. The reaction temperature is maintained at 380°C and the reaction pressure is 0.2MPa. Urea is converted into melamine, ammonia and carbon dioxide on the catalyst surface to generate a material mixed gas;

[0044] (4) The mixed gas generated by the reaction first enters the primary separation mechanism 2. The primary separation mechanism 2 is a conical structure, and a support rod 202 and a spiral blade 201 are arranged inside. When the gas flow rotates along the blade 201, the solid particles sink into the fluidized bed body 1 under the action of gravity, and the gas enters the secondary separation mechanism 3 through the discharge port 14;

[0045] (5) The gas from the primary separation mechanism 2 enters the secondary separation mechanism 3. The secondary separation mechanism 3 further separates the remaining small particle powder by using the dual effects of centrifugal force and rotating airflow. These powders flow back to the fluidized bed body 1 through the pipeline at the bottom of the secondary separation mechanism 3 to continue to participate in the reaction. The rotating partition 302 can also be closed to discharge the catalyst particles. The gas after two-stage separation is transported to the next process section from the product discharge port 15 at the top of the secondary separation mechanism 3;

[0046] (6) The auxiliary mechanism 13 is arranged in the fluidized bed body 1. When working normally, the auxiliary mechanism 13 is placed vertically and does not hinder the reaction. Once an emergency occurs, the auxiliary mechanism 13 can be rotated 90° to form a partition on the upper part of the feed spray gun 901 to separate the raw material and the catalyst, and prevent the catalyst from flowing back and damaging the spray gun 901 and other equipment. The rotating positions 1303 at both ends of the auxiliary mechanism 13 are driven by a motor to realize the flipping of the support plate 1302.

Claims

1. A melamine fluidized bed reactor, characterized in that: The invention comprises a fluidized bed body (1), a primary separation mechanism (2), and a secondary separation mechanism (3), wherein the upper end of the fluidized bed body (1) is connected to the primary separation mechanism (2), the top of the primary separation mechanism (2) is provided with a discharge port (14), the discharge port (14) is connected to the secondary separation mechanism (3), the bottom of the secondary separation mechanism (3) is provided with a pipeline for reflux to the fluidized bed body (1), and the top of the secondary separation mechanism (3) is provided with a product discharge port (15); The bottom of the fluidized bed body (1) is connected to a micron bubble generator (11), the micron bubble generator (11) is connected to a mixer (10), a Y-shaped premixer (6) is provided at the bottom of the mixer (10), a urea feed port (7) is provided at the bottom of the Y-shaped premixer (6), and the Y-shaped premixer (6) is connected to an ammonia mixed gas pipeline (8).

2. The melamine fluidized bed reactor according to claim 1, characterized in that: The fluidized bed body (1) is provided with a feed plate (9), a gas distribution plate (12), an auxiliary mechanism (13), and a catalyst feed port (4) in sequence from bottom to top, and the inlet of the pipeline connecting the fluidized bed body (1) and the secondary separation mechanism (3) is located above the auxiliary mechanism (13).

3. The melamine fluidized bed reactor according to claim 2, characterized in that: The auxiliary mechanism (13) comprises a spiral shaft (1301), a support plate (1302), and a rotation point (1303); the spiral shaft (1301) is located at the center of the support plate (1302) and is used to support the auxiliary mechanism (13) in rotation; two rotation points (1303) are provided at the positions where the two ends of the spiral shaft (1301) are connected to the fluidized bed body (1); the rotation points (1303) are controlled by a motor to rotate the auxiliary mechanism (13).

4. The melamine fluidized bed reactor according to claim 2, characterized in that: The feed plate (9) is provided with a spray gun (901), the gas distribution plate (12) is provided with a jacket (902) at a position corresponding to the spray gun (901), and a gas inlet is provided on a side wall of the gas distribution plate (12) and is connected to the ammonia mixed gas pipeline (8).

5. The melamine fluidized bed reactor according to claim 4, characterized in that: The jacket (902) is located outside the spray gun (901), the outlet height of the jacket (902) is lower than the outlet height of the spray gun (901), and the outlet height of the jacket (902) is higher than the height of the gas distribution plate (12).

6. The melamine fluidized bed reactor according to claim 1, characterized in that: The primary separation mechanism (2) comprises blades (201) and a support rod (202). The primary separation mechanism (2) is a conical structure. A support rod (202) is arranged in the center of the conical structure in a vertical direction. The support rod (202) is provided with blades (201). The blades (201) are arranged in a spiral downward along the support rod (202) starting from the top of the support rod (202).

7. The melamine fluidized bed reactor according to claim 1, characterized in that: The bottom of the secondary separation mechanism (3) is refluxed to the pipeline of the fluidized bed body (1), and is provided with a sewage outlet (301) and a rotating baffle (302), wherein the sewage outlet (301) is located above the rotating baffle (302).

8. The melamine fluidized bed reactor according to claim 1, characterized in that: The ammonia mixed gas pipeline (8) is provided with a branch connected to the micron bubble generator (11).

9. The melamine fluidized bed reactor according to claim 1, characterized in that: Three support frames (5) are evenly welded around the outer wall of the bottom of the fluidized bed body (1) for supporting the entire device.

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