Process system and method for producing acrylonitrile

Abstract

The invention discloses a process system and method for producing acrylonitrile, the process system comprises an ammonia-propylene reactor, the ammonia-propylene reactor is connected with a heating device and an ammonia-propylene mixer, and the heating device is connected with an air compressor; the ammonia-propylene mixer is connected with a propylene superheater and an ammonia superheater, the propylene superheater is connected with a propylene evaporator, and the ammonia superheater is connected with an ammonia evaporator. The process system for producing acrylonitrile, which is reasonable in layout, is simple in structure, small in occupied area and low in investment cost; raw materials of liquid propylene and ammonia are fed into a propylene evaporator and an ammonia evaporator from a liquid pump, gasified propylene and ammonia gas are superheated by a superheater and then respectively enter an ammonia-propylene mixer to be uniformly mixed, and after mixing, the mixture enters an ammonia-propylene reactor; on the other hand, the raw material air is taken from the atmosphere, the air enters the air compressor after being filtered by the filter, and the air compressed by the air compressor enters the bottom of the ammonia-propylene reactor through the heating device after being started, and is mixed with propylene and ammonia.

Description

Technical Field

[0001] The invention relates to the technical field of producing acrylonitrile, and in particular to a process system and method for producing acrylonitrile. Background Art

[0002] Acrylonitrile is the main raw material for the production of polyacrylonitrile fiber (acrylic fiber). Acrylic fiber has excellent properties such as softness, warmth retention, and light resistance. In addition, the demand for high-performance fibers in special fields such as industrial filtration and outdoor products will further promote the application of acrylonitrile in the field of synthetic fibers. Acrylonitrile is also copolymerized with butadiene to produce nitrile rubber, which has good oil resistance, wear resistance and heat resistance, and is widely used in seals and conveyor belts in the automotive, aerospace, petrochemical and other fields. As a key component in the production of ABS resin (acrylonitrile-butadiene-styrene copolymer), ABS resin has high strength, high toughness and good processing properties, and is widely used in many fields such as electronic appliances, automotive parts, and building materials. Acrylonitrile is also used to produce a variety of fine chemical products, such as water repellents, adhesives, coatings, carbon fibers, etc.

[0003] In the 1840s, acrylonitrile began to be produced industrially for the first time, using hydrocyanic acid and ethylene oxide or acetylene to react. In 1960, the American Sohio Company pioneered and developed the propylene ammoxidation method (Sohio method), which was quickly promoted. After years of development, the production technology of acrylonitrile has become increasingly mature and perfect. Today, more than 95% of the world's acrylonitrile is produced using the Sohio method.

[0004] In recent years, the main technology for producing acrylonitrile in China is propylene ammoxidation, which accounts for more than 90% of the global market share. Propylene ammoxidation uses propylene and ammonia as raw materials to produce acrylonitrile, and by-products include acetonitrile and hydrocyanic acid. The raw materials of this technology are easy to obtain, the process is simple, the operation is stable, and the product is easy to refine. At present, the production of acrylonitrile by propylene ammoxidation has low conversion rate, high energy consumption, and the catalyst is brought into the downstream, resulting in unstable downstream operation and complex catalyst replacement reactor process. Summary of the invention

[0005] The present invention aims to solve the problems of low conversion rate, high energy consumption, catalyst being carried downstream, resulting in unstable downstream operation, and complex catalyst replacement process in the reactor, etc. in the current propylene ammoxidation method for producing acrylonitrile, and provides a process system and method for producing acrylonitrile.

[0006] In order to achieve the above technical objectives, the technical solution provided by the present invention is:

[0007] A process system for producing acrylonitrile comprises an ammonia-propylene reactor, wherein the ammonia-propylene reactor is connected to a heating device and an ammonia-propylene mixer, the heating device is connected to an air compressor; the ammonia-propylene mixer is connected to a propylene superheater and an ammonia superheater, the propylene superheater is connected to a propylene evaporator, and the ammonia superheater is connected to the ammonia evaporator.

[0008] Specifically, the heating device includes but is not limited to a heating furnace.

[0009] Furthermore, the air compressor is provided with an air filter, which can filter out impurities in the air to prevent contamination of the catalyst, thereby indirectly improving the reaction conversion rate and product yield.

[0010] Furthermore, the ammonia-propylene reactor is provided with a heat collector, which is connected to an air compressor. The heat collector adopts an external heat collection and back-mixing form, and the heat collection load of the ammonia-propylene reactor is adjusted by compressed air. The operation and control are convenient, and the heat collection effect is obvious.

[0011] Furthermore, the heat extractor is connected to the fresh catalyst tank and the spent catalyst tank.

[0012] Furthermore, the heat extractor is connected to a heat extraction steam drum, the heat extraction steam drum is connected to a superheater, and the top of the heat extraction steam drum is connected to an incinerator.

[0013] Furthermore, a primary cyclone separator and a secondary cyclone separator are arranged inside the ammonia-propylene reactor, the secondary cyclone separator is connected to the primary cyclone separator, and the efficiency of the cyclone catalyst is 99%.

[0014] Furthermore, the ammonia-propylene reactor is connected to a filter and a catalyst collecting tank, the bottom of the filter is connected to the catalyst collecting tank, and the catalyst collecting tank is connected to a fresh catalyst tank and a waste catalyst tank.

[0015] Specifically, the filtered catalyst is sampled and analyzed. When the performance is stable, the filtered catalyst is supplemented to the ammonia-propylene reactor through the catalyst collection tank. If the catalyst performance is poor, it is unloaded to the waste catalyst tank. The operation is flexible and easy to use. When the ammonia-propylene reactor is supplemented with catalyst, fresh catalyst is added to the catalyst collection tank to supplement the ammonia-propylene reactor.

[0016] Furthermore, the top of the filter is connected to a superheater, and the superheater is connected to an absorption tower.

[0017] Specifically, lowering the temperature of the reaction product by a superheater helps the downstream absorption tower to absorb the acrylonitrile product.

[0018] Furthermore, the top of the absorption tower is connected to an incinerator, and the incinerator is provided with an incinerator steam drum.

[0019] The present invention also provides a method for producing acrylonitrile, comprising the following steps:

[0020] Step 1: Propylene and ammonia are pumped into a propylene evaporator and an ammonia evaporator respectively to gasify the propylene and ammonia. The gasified propylene and ammonia pass through a heater, and after being overheated, they enter an ammonia-propylene mixer respectively to be evenly mixed, and then enter an ammonia-propylene reactor after mixing;

[0021] Step 2: After the raw air enters the air compressor for compression, the compressed air enters the bottom of the ammonia-propylene reactor through the heating device and mixes with propylene and ammonia. The mixed gas fluidizes the catalyst bed and reacts at the same time.

[0022] The present invention has the following beneficial effects:

[0023] 1. The present invention adopts a process system for producing acrylonitrile with a reasonable layout, which has a simple structure, a small footprint and a low investment cost. The raw materials, liquid propylene and ammonia, are pumped from the liquid raw material tank area into the propylene and ammonia evaporators, and the gasified propylene and ammonia are superheated in the heater and respectively enter the ammonia-propylene mixer for uniform mixing, and then enter the ammonia-propylene reactor after mixing; on the other hand, the raw material air is taken from the atmosphere, and the air is filtered by a filter and then enters the air compressor. The air compressed by the air compressor, after being started, enters the bottom of the ammonia-propylene reactor through a heating device and is mixed with propylene and ammonia.

[0024] 2. The catalyst carried by the reaction product of the present invention is filtered through a filter and then sent to the ammonia-propylene reactor through a catalyst collection tank. If the activity of the catalyst in the ammonia-propylene reactor is reduced or there is too much fine powder, the catalyst in the catalyst collection tank can be unloaded into a waste catalyst tank, and fresh catalyst is added to the ammonia-propylene reactor. The catalyst replacement and supplementation are flexible and easy to use, ensuring the reaction conversion rate and product yield; the tail gas of the process system for producing acrylonitrile is incinerated, which is environmentally friendly.

[0025] 3. In the present invention, the deoxygenated water enters the superheater for heating and then enters the heat extraction drum, while reducing the temperature of the reaction product to increase heat utilization. The hot water in the heat extraction drum enters the heat extraction drum through a pipeline. In addition, 4.0 MPa saturated steam is produced by taking the reaction heat of the ammonia-propylene reactor. The 4.0 MPa saturated steam enters the heat extraction drum through a pipeline. The saturated steam of the heat extraction drum is combined with the saturated steam of the incinerator drum through a pipeline and enters the superheating section of the incinerator for superheating, and finally produces 4.0 MPa superheated steam. The 4.0 MPa superheated steam is used to drive the air compressor 8. The system produces superheated steam as a by-product, has low energy consumption, and low overall operating cost.

[0026] 4. The incinerator of the present invention is safe, reliable, environmentally friendly, can produce steam, and has low operating cost. The cyclone separator in the ammonia-propylene reactor separates the catalyst carried in the product. The filter filters the catalyst carried in the reaction product. The air filter filters impurities in the air without polluting the catalyst. The ammonia-propylene mixer fully mixes propylene and ammonia, so that the feed is evenly mixed, thereby improving the reaction conversion rate and yield. The catalyst collecting tank can collect the filtered catalyst and add it to the ammonia-propylene reactor or directly unload it to the waste catalyst tank, thereby improving the utilization efficiency of the catalyst and being easy to operate. The heat extractor adopts the form of sampling external heat extraction and remixing, which is convenient to operate, easy to control, safe and reliable, with high heat utilization, steam production, low energy consumption, and low operating cost. The heat extractor can be used as a replacement and supplementary transfer equipment for the reactor catalyst, which is convenient to operate, flexible and easy to use. The superheater, the deoxygenated water passes through the superheater, while reducing the temperature of the reaction product, increasing the temperature of the deoxygenated water, saving energy and reducing consumption, and improving thermal efficiency. The evaporator and the superheater are respectively provided for propylene and ammonia, thereby effectively increasing the feed temperature, not affecting each other, being easy to operate, and being good to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A flowchart of Embodiment 1 provided by the present invention;

[0028] Figure 2 A flowchart of Embodiment 2 provided by the present invention;

[0029] Markings and corresponding parts names in the attached drawings:

[0030] 1- ammonia-propylene reactor; 2- propylene evaporator; 3- propylene superheater; 4- ammonia evaporator; 5- ammonia superheater; 6- ammonia-propylene mixer; 7- heat extractor; 8- air compressor; 9- heating device; 10- filter; 11- catalyst collection tank; 12- fresh catalyst tank; 13- waste catalyst tank; 14- superheater; 15- absorption tower; 16- heat extraction drum; 17- incinerator; 18- incinerator drum; 101- primary cyclone separator; 102- secondary cyclone separator; 103- air filter DETAILED DESCRIPTION

[0031] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0033] Example 1

[0034] like Figure 1 As shown, a process system for producing acrylonitrile provided in this embodiment includes an ammonia-propylene reactor 1, wherein the bottom of the ammonia-propylene reactor 1 is connected to a heating device 9, the heating device 9 is connected to an air compressor 8, and an air filter 103 is arranged at the inlet of the air compressor 8; before the air enters the air compressor 8, it passes through the air filter 103 to filter out impurities carried in the air, thereby not affecting the reaction effect, and the filtering effect is obvious; when the heating device 9 is started, the temperature of the compressed air can be increased, and the start-up time can be shortened; during normal production, a cross-line can be set or used as a compressed air channel; during shutdown or accident state, it is used to burn the catalyst to ensure the temperature of the ammonia-propylene reactor 1, and cooperate with the catalyst unloading to make the unloaded catalyst in a regenerated state.

[0035] In this embodiment, the lower part of the ammonia-propylene reactor 1 is connected to an ammonia-propylene mixer 6, the ammonia-propylene mixer 6 is connected to a propylene superheater 3 and an ammonia superheater 5, the propylene superheater 3 is connected to a propylene evaporator 2, and the ammonia superheater 5 is connected to an ammonia evaporator 4; the raw material liquid propylene is pumped into the propylene evaporator 2 from the propylene spherical tank in the liquid raw material tank area, and the propylene is controlled to be gasified at 0°C. The gasified propylene gas is superheated by the propylene superheater 3; the raw material liquid ammonia is pumped into the ammonia evaporator 4 from the ammonia spherical tank in the liquid raw material tank area, and the ammonia is controlled to be gasified at 7°C. After the gasified ammonia is superheated by the ammonia superheater 5, it is evenly mixed with the superheated propylene in the ammonia-propylene mixer 6 and enters the ammonia-propylene reactor 1.

[0036] In this embodiment, a heat collector 7 is arranged outside the ammonia-propylene reactor 1. The heat collector 7 adopts a back-mixing type. The heat collector 7 is connected to an air compressor 8. The heat load of the ammonia-propylene reactor 1 is adjusted by compressed air. Two streams of fluidized compressed air are arranged, and the heat collection effect is obvious, easy to control, and convenient to operate; the heat collector 7 is connected to a fresh catalyst tank 12 and a waste catalyst tank 13; the heat collector 7 is connected to a fresh catalyst tank: if the ammonia-propylene reactor 1 lacks catalyst or has little catalyst, the catalyst can be supplemented to the heat collector through the fresh catalyst tank. The catalyst storage of the heat collector 7 is certain, and the supplemented catalyst (equivalent to the excess catalyst) will directly enter the ammonia-propylene reactor 1 for the reaction of the ammonia-propylene reactor 1; the heat collector 7 is connected to a waste catalyst tank: the temperature of the ammonia-propylene reactor 1 is generally relatively high, and the temperature of the catalyst unloading pipeline will increase during the catalyst unloading process, and even exceed the design problem. In order to avoid damaging the catalyst pipeline and equipment, the catalyst agent can be unloaded from the heat collector 7.

[0037] In this embodiment, a primary cyclone separator 101 and a secondary cyclone separator 102 are arranged inside the ammonia-propylene reactor 1, and the efficiency of cyclone separation of catalyst is 99%. The top of the ammonia-propylene reactor 1 is connected to a filter 10, and the top of the filter 10 is connected to a superheater 14 and an absorption tower 15 in sequence; the number of filters 10 can be 3 to 6 according to the needs of the device, and the efficiency of filtering the catalyst is above 99%. The cyclone separator and the filter are combined, and the total efficiency is above 99.99%, and the catalyst removal effect is good; the ammonia-propylene reactor 1 is connected to the filter 10 and the catalyst collection tank 11, and the bottom of the filter 10 is connected to the catalyst collection tank 11, and the catalyst is removed. The catalyst collecting tank 11 is connected to the fresh catalyst tank 12 and the waste catalyst tank 13. The catalyst in the collecting tank 11 is sampled and analyzed, and the direction of the catalyst in the catalyst collecting tank 11 is determined according to the analysis result. When the catalyst activity is high, the catalyst in the catalyst collecting tank 11 is directly added to the ammonia-propylene reactor 1. When the activity is low or there is a lot of fine powder, the catalyst in the catalyst collecting tank 11 is directly unloaded to the waste catalyst tank 13. When the amount of catalyst in the ammonia-propylene reactor 1 is small, fresh catalyst can be added to the catalyst collecting tank 11 through the fresh catalyst tank 12. Finally, the fresh catalyst in the catalyst collecting tank 11 can enter the ammonia-propylene reactor 1 through a pipeline.

[0038] Example 2

[0039] like Figure 2 As shown, the upper end of the superheater 14 is connected to the heat extraction drum 16, and the heat extraction drum 16 is connected to the heat collector 7; the lower end of the superheater 14 is connected to the absorption tower 15, and the top of the absorption tower 15 is connected to the incinerator 17, and the incinerator 17 is provided with an incinerator drum 18; the deoxygenated water enters the superheater 14 for heating and then enters the heat extraction drum 16, while reducing the temperature of the reaction product to increase the heat utilization rate, and the hot water in the heat extraction drum 16 enters the heat collector 7 through a pipeline; in addition, 4.0 MPa saturated steam is produced by taking the reaction heat of the ammonia-propylene reactor 1, and the 4.0 MPa saturated steam enters the heat extraction drum 16 through a pipeline, and the saturated steam of the heat extraction drum 16 is merged with the saturated steam of the incinerator drum 18 through a pipeline and enters the superheating section of the incinerator 17 for superheating, and finally produces 4.0 MPa superheated steam, and the 4.0 MPa superheated steam is used to drive the air compressor 8.

[0040] In this embodiment, the tail gas from the absorption tower 15 enters the incinerator 17 for incineration. The incinerator 17 is provided with an evaporation section, an overheating section, and a heating section. The deoxygenated water enters the heating section for heating and then enters the incinerator drum 18. The hot water in the incinerator drum 18 enters the evaporation section of the incinerator 17 to produce saturated steam. The saturated steam enters the incinerator drum 18 through a pipeline. The saturated steam in the incinerator drum 18 merges with the saturated steam in the heat extraction drum 16 and enters the overheating section of the incinerator 17 for overheating, thereby finally producing 4.0 MPa of superheated steam.

[0041] The process system for producing acrylonitrile provided in this embodiment has a simple structure, a small footprint, low investment cost, safety and reliability, environmental friendliness, flexible operation, system steam production, high heat utilization rate, low energy consumption, and low production process operating cost.

[0042] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art 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 appended claims and their equivalents.

[0043] The above specific implementation methods are detailed descriptions of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A process system for producing acrylonitrile, characterized in that: The invention comprises an ammonia-propylene reactor (1), wherein the ammonia-propylene reactor (1) is connected to a heating device (9) and an ammonia-propylene mixer (6), the heating device (9) is connected to an air compressor (8); the ammonia-propylene mixer (6) is connected to a propylene superheater (3) and an ammonia superheater (5), the propylene superheater (3) is connected to a propylene evaporator (2), and the ammonia superheater (5) is connected to an ammonia evaporator (4).

2. A process system for producing acrylonitrile according to claim 1, characterized in that: The air compressor (8) is provided with an air filter (103).

3. A process system for producing acrylonitrile according to claim 1, characterized in that: The ammonia-propylene reactor (1) is provided with a heat collector (7), and the heat collector (7) is connected to an air compressor (8).

4. A process system for producing acrylonitrile according to claim 3, characterized in that: The heat extractor (7) is connected to the fresh catalyst tank (12) and the spent catalyst tank (13).

5. A process system for producing acrylonitrile according to claim 3, characterized in that: The heat extractor (7) is connected to a heat extraction steam drum (16), the heat extraction steam drum (16) is connected to a superheater (14), and the top of the heat extraction steam drum (16) is connected to an incinerator (17).

6. A process system for producing acrylonitrile according to claim 1, characterized in that: A primary cyclone separator (101) and a secondary cyclone separator (102) are arranged inside the ammonia-propylene reactor (1), and the secondary cyclone separator (102) is connected to the primary cyclone separator (101).

7. A process system for producing acrylonitrile according to claim 1, characterized in that: The ammonia-propylene reactor (1) is connected to a filter (10) and a catalyst collecting tank (11), the bottom of the filter (10) is connected to the catalyst collecting tank (11), and the catalyst collecting tank (11) is connected to a fresh catalyst tank (12) and a waste catalyst tank (13).

8. A process system for producing acrylonitrile according to claim 7, characterized in that: The top of the filter (10) is connected to a superheater (14), and the superheater (14) is connected to an absorption tower (15).

9. A process system for producing acrylonitrile according to claim 8, characterized in that: The top of the absorption tower (15) is connected to an incinerator (17), and the incinerator (17) is provided with an incinerator steam drum (18).

10. A method for producing acrylonitrile using a process system according to any one of claims 1 to 9, characterized in that: The steps include: Step 1: Propylene and ammonia are pumped into a propylene evaporator and an ammonia evaporator respectively to gasify the propylene and ammonia. The gasified propylene and ammonia pass through a heater, and after being overheated, they enter an ammonia-propylene mixer respectively to be evenly mixed, and then enter an ammonia-propylene reactor after mixing; Step 2: After the raw air enters the air compressor for compression, the compressed air enters the bottom of the ammonia-propylene reactor through the heating device and mixes with propylene and ammonia. The mixed gas fluidizes the catalyst bed and reacts at the same time.

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