A system and method for continuous production of acetonitrile by amination of acetic acid.

Abstract

This invention relates to a system and method for the continuous production of acetonitrile via acetic acid ammoniation. This system ensures stable reaction processes without requiring catalyst replacement, enabling long-term operation of the entire production unit. The system, arranged sequentially according to material flow direction, includes a raw material pretreatment section, a catalytic regeneration section, a distillation section, and a denitrification section, achieving catalyst recycling and continuous, energy-efficient acetonitrile production. The system's continuous operation cycle is 18–24 months. Compared to existing technologies that require catalyst replacement every 6–7 months, this invention allows for catalyst replenishment without shutdown, and eliminates the need for complete catalyst replacement. The replacement catalyst mass is 50–75% of the original catalyst mass, ultimately achieving an acetic acid conversion rate ≥98%, an acetonitrile selectivity ≥95%, and an acetonitrile purity ≥99 wt%.

Description

Technical Field

[0001] This invention relates to the field of organic chemical technology, and in particular to a system and method for the continuous production of acetonitrile by ammoniation of acetic acid. Background Technology

[0002] Acetonitrile, commonly known as methyl nitrile, is an important fine chemical intermediate and chemical solvent. It can be used as an intermediate and solvent in the pharmaceutical and pesticide industries, and also as an extraction agent in the synthetic rubber industry.

[0003] Currently, acetonitrile mainly appears as a byproduct of acrylonitrile production. The crude acetonitrile obtained has a complex composition, and many components are difficult to separate from acetonitrile, making it difficult to guarantee product quality. Consequently, the energy consumption for subsequent distillation separation is also very high. As it is a byproduct of acrylonitrile production, its yield is heavily dependent on acrylonitrile production.

[0004] The main methods for directly synthesizing acetonitrile are the ethanol ammoxidation method and the acetic acid ammoxidation method.

[0005] The ethanol ammoxidation process is a method for producing acetonitrile using ethanol, ammonia, and oxygen as raw materials in a fixed-bed or fluidized-bed reactor. For example, CN1226281C discloses a method for synthesizing high-purity acetonitrile via ethanol ammoxidation, and CN1329369C discloses a fluidized-bed catalyst for acetonitrile production via ammoxidation. Both patents disclose methods for synthesizing acetonitrile in a fluidized-bed reactor using molybdenum-bismuth as the active catalyst component. The yield of the obtained acetonitrile product is relatively low, approximately 70-81%, with the remaining components mainly being hydrogen cyanide and carbon oxides. Because it is an oxidation reaction, the reactor does not require additional heating. However, a large amount of heat contained in the reactor outlet gas is carried away by quench water, resulting in significant energy waste. Another example is the literature "Amination of ethanol to acetonitrile over Ni-doped Co / γ-Al2O3 catalyst," which discloses a method for synthesizing acetonitrile in a fixed-bed reactor using a Ni-doped Co / γ-Al2O3 catalyst. This method can operate continuously and stably for 720 hours, with an acetonitrile yield of approximately 82%. In summary, although the reactor consumes almost no energy for the ethanol ammoxidation process, the yield of acetonitrile is low, and the large amount of heat at the reactor outlet is not fully utilized. At the same time, whether it is a fixed bed or a fluidized bed, coking will occur on the catalyst surface, so the catalyst cannot operate for a long period of time.

[0006] The acetic acid ammoniation process is a method for synthesizing acetonitrile using acetic acid and ammonia as raw materials, typically in a fixed-bed reactor. For example, CN104529819B discloses a method for preparing acetonitrile using acetic acid ammoniation, employing a hydrogen-form molecular sieve as a catalyst, achieving a 100% conversion rate of acetic acid and a 99% yield of acetonitrile. However, this patent does not address the issue of long-term catalyst operation. Another example is the literature "The Process of Acetonitrite synthesis over γ-Al2O3 promoted by phosphoric acid catalysts," which reports a method for synthesizing acetonitrile in a fixed-bed reactor using acetic acid and ammonia as raw materials and γ-Al2O3 as a catalyst. The catalyst initially exhibits high activity, with both acetic acid conversion and acetonitrile selectivity exceeding 99%. However, as surface coking increases, both activity and selectivity rapidly decline. Catalyst coking leads to process discontinuity, preventing the entire unit from operating for extended periods. Although catalyst improvements can extend the operating time, this does not fundamentally solve the problem of discontinuous reaction processes.

[0007] CN111018741A discloses a novel continuous process for preparing acetonitrile, which mentions a wastewater (referred to as recycled acid) recovery process. Because the wastewater contains complex components, especially high-boiling-point nitrogenous substances, these substances can coat the active surface of the catalyst, leading to catalyst deactivation and severely impacting its lifespan. The deactivated catalyst requires shutdown for removal, thus preventing long-term continuous operation of the equipment. Furthermore, the recovery process uses azeotropic dehydration, which not only introduces new substances into the system but also consumes a significant amount of steam, wasting energy.

[0008] CN 113509965 B discloses a method for regenerating a catalyst used in the acetic acid ammoniation process for producing acetonitrile. The regeneration method includes: preparing a pretreatment solution, catalyst pretreatment, equilibration, a primary regeneration treatment, and a secondary regeneration treatment. The pretreatment solution includes the following raw materials: N-methylpyrrolidone, cyclohexanone, n-dodecyl mercaptan, and methanol. This patent points out that traditional acetic acid ammoniation processes use fixed-bed reactors, where the catalyst can only be removed during shutdown maintenance. However, with increasing time, the surface area, pore size, and pore volume of the catalyst decrease significantly, resulting in a substantial decrease in acetonitrile yield. After 6-7 months of use, the composition of the material flowing out of the reactor can no longer meet the requirements of the subsequent distillation stage, ultimately forcing a shutdown. Because the catalyst is constantly operating under harsh conditions, too many harmful impurities accumulate on its surface and inside. Given the large amount of impurities, even after the primary regeneration treatment, 15-18% of the catalyst still requires deep cleaning through aerobic combustion. Therefore, the treatment process is not only costly but also extremely cumbersome. While this method can extend the catalyst's lifespan, it disrupts the continuous production of the acetonitrile-to-acetylene reaction section, significantly reducing production efficiency. Furthermore, because the catalyst activity is constantly decreasing, the acetonitrile production process remains in a fluctuating state, which is highly detrimental to the entire production process, especially the distillation section.

[0009] Based on the above-mentioned existing technologies, the direct synthesis of acetonitrile in the existing technologies has technical problems that urgently need to be solved, such as catalyst coking, short lifespan, need to be replaced after deactivated catalyst, and inability of the whole system to operate for a long period of time, discontinuous reaction section, long operation time, and lack of energy saving. Summary of the Invention

[0010] To address the aforementioned technical problems, this invention provides an energy-saving system for continuous acetonitrile production. This system ensures the stability of the reaction process without requiring catalyst replacement, thereby enabling long-term operation of the entire production unit. Specifically, this invention provides a system for the continuous production of acetonitrile via acetic acid ammoniation. This system, arranged sequentially according to the material flow direction, includes a raw material pretreatment section, a catalytic reaction regeneration section, a distillation section, and a denitrification section, achieving catalyst recycling and continuous, energy-saving acetonitrile production. The system's continuous operation cycle is 18–24 months.

[0011] Furthermore, the catalytic reaction regeneration section includes a riser reactor, a catalyst regenerator, a gas supply device, and a waste heat boiler. The riser reactor and the catalyst regenerator are connected by a pre-regeneration slide valve and a regeneration slide valve. The catalyst after reaction, i.e., the coking catalyst, enters the catalyst regenerator from the riser reactor through the pre-regeneration slide valve. The regenerated catalyst, i.e., the regenerated catalyst, returns from the catalyst regenerator to the riser reactor through the regeneration slide valve. The circulation of the catalyst is achieved by the pressure difference between the riser reactor and the catalyst regenerator. The pressure difference between the riser reactor and the catalyst regenerator is 80-90 kPa, and the pressure difference between the catalyst regenerator and the riser reactor is 100-110 kPa, which can prevent the material in the riser reactor from entering the catalyst regenerator.

[0012] Furthermore, the mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section to the amount of catalyst stored in the riser reactor is (1-1.5):(1-1.8).

[0013] Furthermore, the riser reactor is provided with reaction section I, reaction section II, and coking catalyst recovery section from bottom to top, wherein the diameter of reaction section I is smaller than that of reaction section II, the diameter of reaction section II is smaller than that of catalyst recovery section, and reaction section I, reaction section II, and coking catalyst recovery section all contain catalyst.

[0014] Furthermore, after the system has been running continuously for 18 to 24 months, 50 to 75% of the total catalyst mass in the riser reactor can be removed as discarded catalyst without stopping the entire system operation. Then, an equal mass of fresh catalyst can be added, thus maintaining the constant catalyst mass in the riser reactor and the stability of the overall system. The riser reactor is provided with a catalyst feeding port on the outside for adding fresh catalyst or removing discarded catalyst. Before adding fresh catalyst, the discarded catalyst is removed from the catalyst feeding port.

[0015] Furthermore, the catalyst regenerator is provided with a coking tank and a regenerated catalyst recovery section from bottom to top inside, and the coking tank is used to remove coke from the coking catalyst.

[0016] Furthermore, the waste heat boiler is used to initially recover the heat generated in the catalytic reaction regeneration section, and to produce steam to power the raw material gasification section, thereby realizing energy reuse.

[0017] Furthermore, the raw material pretreatment section includes a raw material vaporization section and a raw material preheating section. The raw material vaporization section and the raw material preheating section are used to shorten the reaction time of the raw material in the riser reactor, reducing the reaction time to 3-6 seconds, thereby shortening the regeneration cycle of the coking catalyst in the catalyst regenerator, reducing the regeneration cycle to 3-6 seconds.

[0018] Furthermore, the raw material vaporization section includes an acetic acid vaporizer and a liquid ammonia vaporizer. The heat required by the acetic acid vaporizer and the liquid ammonia vaporizer is provided by the material sent from the waste heat boiler of the catalytic reaction regeneration section, thereby realizing energy reuse.

[0019] Furthermore, the raw material preheating section includes a preheater, the heat required by which is provided by the material sent from the riser reactor of the catalytic reaction regeneration section, thereby realizing energy reuse.

[0020] Furthermore, the preheater includes an acetic acid preheater and an ammonia preheater.

[0021] Furthermore, a falling film evaporator is provided between the riser reactor and the distillation section in the raw material preheating section. The heat required by the falling film evaporator is provided by the material sent out from the raw material preheating section, thereby realizing energy reuse.

[0022] Furthermore, the air supply device includes a smoke machine, a blower, and a motor. The smoke machine recovers the pressure energy of the catalyst regenerator and uses it to drive the blower to blow air into the catalyst regenerator, thereby realizing energy reuse. The motor is a backup power supply device used to supplement the kinetic energy of the blower.

[0023] Furthermore, the catalytic reaction regeneration section also includes an external heat exchanger to stabilize the temperature of the catalyst regenerator. The extracted waste heat is used to produce steam, which is then transported to the steam pipeline network to achieve energy reuse.

[0024] Furthermore, the distillation section includes a gas-liquid separator and a distillation column. The gas-liquid separator is used to separate crude acetonitrile product and send the ammonia in the crude acetonitrile product back to the riser reactor in the catalytic reaction regeneration section to participate in the catalytic reaction again. The distillation column is used to distill the crude acetonitrile product after removing ammonia to obtain the finished acetonitrile product, wherein the conversion rate of acetic acid is ≥98%, the selectivity of acetonitrile is ≥95%, and the purity of acetonitrile is ≥99wt%.

[0025] Furthermore, the crude acetonitrile product contains acetonitrile, water, ammonium acetate, acetamide, ammonia, acetic acid, and nitrogen-containing organic matter. The acetonitrile accounts for 50-55 wt% of the crude acetonitrile product, and the water accounts for 45-46 wt% of the crude acetonitrile product, based on the total mass of the crude acetonitrile product.

[0026] Furthermore, the denitrification section includes a selective catalytic reduction (SCR) reactor and a second waste heat boiler. The SCR reactor is used to purify the flue gas from the catalytic reaction regeneration section and the waste gas from the distillation section. The flue gas contains nitrogen oxides, and the waste gas is ammonia. The second waste heat boiler recovers the heat from the materials discharged from the SCR reactor to produce steam, which is then transported to the steam pipeline network to achieve energy reuse.

[0027] The present invention also provides a method for continuous production of acetonitrile using the above-mentioned system for continuous production of acetonitrile by acetic acid amination, comprising the following steps:

[0028] (1) Pretreatment: The raw materials acetic acid and liquid ammonia are vaporized by the acetic acid vaporizer and liquid ammonia vaporizer in the raw material vaporization section, respectively. The vaporized acetic acid gas and ammonia gas are then heated by the preheater in the raw material preheating section.

[0029] (2) Catalytic reaction: The acetic acid gas and ammonia gas heated in step (1) enter the riser reactor from the bottom of the riser reactor in the catalytic reaction regeneration section. Under the action of the catalyst, they react to produce crude acetonitrile product, which includes intermediates ammonium acetate and acetamide. The crude acetonitrile product is sent out from the top of the riser reactor and enters the preheater in the raw material preheating section to supply energy to the raw material preheating section. The catalytic chemical reactions involved are:

[0030]

[0031] Wherein, M1 is acetic acid gas, M2 is ammonia gas, M3 is ammonium acetate, M4 is acetamide, and M5 is acetonitrile;

[0032] (3) Catalyst regeneration: The coked catalyst after the reaction in step (2) enters the catalyst regenerator through the regeneration slide valve and reacts with the air blown in by the blower to burn off the coke on the catalyst and become a regenerated catalyst that can participate in the reaction again, and generates flue gas. The regenerated catalyst enters the riser reactor through the regeneration slide valve to participate in the catalytic reaction again, realizing the recycling of the catalyst.

[0033] (4) Crude acetonitrile distillation: The crude acetonitrile product after the first cooling stage of the raw material preheating section in step (2) enters the falling film evaporator for the second cooling stage. The crude acetonitrile product after the second cooling stage enters the gas-liquid separator in the distillation section for gas-liquid separation. The gas is ammonia, which is discharged from the top of the gas-liquid separator and then merged into the acetic acid gas and ammonia gas after heating in step (1). The liquid is the crude acetonitrile product after removing ammonia, which enters the distillation tower for distillation to obtain the finished acetonitrile product. At the same time, wastewater and waste gas are generated. Among them, the wastewater contains intermediate ammonium acetate and acetamide and nitrogen-containing organic matter. 30-50% of the total wastewater mass is returned to the falling film evaporator for concentration. It is then combined with the acetic acid gas and ammonia gas after heating in step (1) and the ammonia gas discharged from the gas-liquid separator and enters the riser reactor to participate in the catalytic reaction again. The remaining wastewater is discharged to the wastewater treatment station for treatment and discharged after meeting the standards.

[0034] (5) Denitrification: The flue gas generated in step (3) and the waste gas generated in step (4) are combined and then enter the selective catalytic reduction (SCR) reactor in the denitrification section for denitrification reaction to obtain denitrified gas, which is then fed into the waste heat boiler to recover heat and is discharged in compliance with standards. The flue gas contains nitrogen oxides and the waste gas is ammonia.

[0035] Further, in step (1), the molar ratio of raw material acetic acid and liquid ammonia is 1:(1.05~1.1), and the temperature of acetic acid gas after heating is 250~300℃, and the temperature of ammonia gas is 250~300℃.

[0036] Furthermore, in step (2), the top pressure in the riser reactor is 200-300 kPa, and the top pressure in the catalyst regenerator is 200-300 kPa. The top pressure is controlled by valves and heat exchangers installed on the riser reactor or the catalyst regenerator. The circulation of the catalyst is achieved by the pressure difference between the riser reactor and the catalyst regenerator. The pressure difference between the riser reactor and the catalyst regenerator is 80-90 kPa, and the pressure difference between the catalyst regenerator and the riser reactor is 100-110 kPa. At the same time, it can also prevent the material in the riser reactor from entering the catalyst regenerator.

[0037] Furthermore, in step (2), the mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section to the amount of catalyst stored in the riser reactor is (1-1.5):(1-1.8).

[0038] Furthermore, in step (2), the catalyst in the riser reactor is selected from one or more of ZSM molecular sieves, HZSM molecular sieves, Ti-Si molecular sieves, SAPO molecular sieves, MCM molecular sieves, type A molecular sieves, type X molecular sieves, type Y molecular sieves, and acid-modified γ-Al2O3.

[0039] Furthermore, in step (2), the catalyst in the riser reactor is selected from one of ZSM-5 molecular sieve, Ti-Si molecular sieve, SAPO-34 molecular sieve, Y-type molecular sieve, and acid-modified γ-Al2O3.

[0040] Furthermore, in step (2), the catalyst is in powder form with a particle size range of 40–100 μm.

[0041] Furthermore, in step (2), the reaction temperature of the riser reactor is 360–450°C, and the reaction cycle duration is 3–6 seconds.

[0042] Furthermore, in step (3), the reaction temperature in the catalyst regenerator is 600-700°C, and the regeneration cycle time is 3-6 seconds.

[0043] Furthermore, the reaction temperature in the catalyst regenerator in step (3) is 650–700°C.

[0044] Furthermore, in step (3), a CO combustion enhancer is introduced to help accelerate the rate of catalyst regeneration.

[0045] Furthermore, the nitrogen oxide content of the flue gas in step (3) is 0.3 to 0.5 wt%.

[0046] Furthermore, in step (4), the conversion rate of acetic acid is ≥98%, the selectivity of acetonitrile is ≥95%, and the purity of acetonitrile is ≥99wt%.

[0047] Furthermore, the mass content of the intermediates ammonium acetate and acetamide in the wastewater of step (4) is 40-60 wt%.

[0048] Furthermore, the temperature of the SCR reactor in step (5) is 280–320°C.

[0049] Furthermore, in step (5), the oxygen content of the denitrification gas is 3-5 wt%, and the nitrogen oxide content is less than 100 ppm.

[0050] The beneficial effects of this invention are as follows:

[0051] 1. The catalytic regeneration section in the system and process for continuous acetonitrile production by acetic acid ammoniation provided by this invention can achieve regeneration of the coking catalyst directly in the system without removing it, realizing the recycling of the catalyst and meeting the requirements of long-term operation. This further enables continuous acetonitrile production, with the system operating continuously for 18 to 24 months. Compared with the prior art, which requires shutdown and replacement of the catalyst every 6 to 7 months, this invention can replenish the catalyst without shutdown and does not require complete replacement of the entire catalyst. The replacement catalyst mass is 50 to 75% of the original catalyst mass, ultimately achieving an acetic acid conversion rate of ≥98%, an acetonitrile selectivity of ≥95%, and an acetonitrile purity of ≥99 wt%.

[0052] 2. The system and process for continuous production of acetonitrile by acetic acid ammoniation provided by this invention can improve the adaptability of existing catalysts. Existing catalysts with different activities, such as ZSM molecular sieves, HZSM molecular sieves, Ti-Si molecular sieves, SAPO molecular sieves, MCM molecular sieves, type A molecular sieves, type X molecular sieves, type Y molecular sieves, and acid-modified γ-Al2O3, can be applied, which is convenient for large-scale promotion. Moreover, the fresh catalyst added accounts for only 50-75% of the mass of the original catalyst in the riser reactor, which greatly saves production costs.

[0053] 3. The system and process for continuous production of acetonitrile by acetic acid amination provided by this invention fully realizes energy recovery and recycling in the raw material vaporization section, raw material preheating section, catalytic reaction regeneration section, distillation section and denitrification section, thus achieving the purpose of energy saving and environmental protection.

[0054] 4. The falling film evaporator in the continuous acetonitrile production system and process provided by the present invention enables the recycling of wastewater from the distillation section, reducing environmental pressure. It can also significantly save steam consumption in existing traditional processes by recovering the energy of crude acetonitrile products.

[0055] 5. In this invention, a blower is used to replace the high-temperature molten salt heating system used in the fixed-bed reactor for acetonitrile production in the prior art. The power consumption of the blower is significantly lower than that of the molten salt system. Furthermore, part of the kinetic energy of the blower comes from the kinetic energy (pressure energy) of the catalyst regenerator recovered by the flue gas fan, which further reduces the energy consumption in the system and process for continuous acetonitrile production by acetic acid ammoniation in this invention. Attached Figure Description

[0056] Figure 1 This is a system flow diagram of the continuous production of acetonitrile by acetic acid amination in Examples 1-3 of the present invention;

[0057] Figure 2 The diagram shows the structure of the riser reactor in Embodiments 1-4 of this invention.

[0058] Figure 3 The diagram shows the structure of the catalyst regenerator in Examples 1-4 of this invention.

[0059] Figure 4 This is a system flow diagram of the continuous production of acetonitrile by acetic acid amination in Example 4 of the present invention.

[0060] The names of the labels in the diagram are as follows:

[0061] A. Raw material pretreatment section; B. Catalytic reaction regeneration section; C. Distillation section; D. Denitrification section; 1. Liquid ammonia vaporizer; 2. Acetic acid vaporizer; 3. Preheater; 301. Ammonia preheater; 302. Acetic acid preheater; 4. Riser reactor; 401. Reaction section I; 402. Reaction section II; 403. Coking catalyst recovery section; 5. Catalyst regenerator; 501. Coke burner; 502. Regenerated catalyst recovery section; 6. Regeneration slide valve; 7. Waiting slide valve; 8. External heat exchanger; 9. Smoke machine; 10. Blower; 11. Motor; 12. Waste heat boiler one; 3. Falling film evaporator; 14. Gas-liquid separator; 15. Distillation column one; 16. Distillation column two; 17. SCR reactor; 18. Waste heat boiler two; 19. Catalyst feed inlet / outlet; 20. Steam network; 21. Wastewater treatment station; 22. Chimney; a. Acetic acid; b. Liquid ammonia; c1. Boiler feedwater one; c2. Boiler feedwater two; c3. Boiler feedwater three; d. Flue gas; e1. Steam one; e2. Steam two; e3. Steam three; e4. Steam four; f. Air; g. Waste gas; h. Denitrification gas; i. Acetonitrile; j. Wastewater; k. Concentrated material; m. Condensate. Detailed Implementation

[0062] Example 1

[0063] like Figure 1 As shown, this embodiment provides a system for the continuous production of acetonitrile by ammoniation of acetic acid. The system includes, in sequence according to the material flow direction, a raw material pretreatment section A, a catalytic reaction regeneration section B, a distillation section C, and a denitrification section D, thereby realizing catalyst recycling and continuous energy-saving production of acetonitrile.

[0064] The raw material pretreatment section A includes a liquid ammonia vaporizer 1, an acetic acid vaporizer 2, an ammonia preheater 301, and an acetic acid preheater 302.

[0065] The catalytic reaction regeneration section B includes a riser reactor 4, a catalyst regenerator 5, a gas supply device, and a waste heat boiler 12. The riser reactor 4 and the catalyst regenerator 5 are connected by a waiting slide valve 7 and a regeneration slide valve 6. The coking catalyst after reaction enters the catalyst regenerator 5 from the riser reactor 4 through the waiting slide valve 7, and the regenerated catalyst returns from the catalyst regenerator 5 to the riser reactor 4 through the regeneration slide valve 6. The circulation of the catalyst is achieved by the pressure difference between the riser reactor 4 and the catalyst regenerator 5. The pressure difference between the riser reactor 4 and the catalyst regenerator 5 is 80 kPa, and the pressure difference between the catalyst regenerator 5 and the riser reactor 4 is 110 kPa. This prevents the material in the riser reactor 4 from entering the catalyst regenerator 5.

[0066] The mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section B to the amount of catalyst stored in the riser reactor 4 is 1.1:1.8.

[0067] like Figure 2 As shown, the riser reactor 4 is provided with reaction section I 401, reaction section II 402, and coking catalyst recovery section 403 from bottom to top. The diameter of reaction section I 401 is smaller than that of reaction section II 402, and the diameter of reaction section II 402 is smaller than that of catalyst recovery section 403. All three reaction sections I 401, reaction section II 402, and coking catalyst recovery section 403 contain catalyst.

[0068] In this embodiment, the system can operate continuously for 24 months. After 24 months of continuous operation, without stopping the entire system, 50% of the total catalyst mass in the riser reactor 4 can be removed as discarded catalyst, and then an equal mass of fresh catalyst can be added. This maintains the constant catalyst mass in the riser reactor 4 and the stability of the overall system. The riser reactor 4 is provided with a catalyst feeding port 19 on the outside for adding fresh catalyst or removing discarded catalyst. Before adding fresh catalyst, discarded catalyst is removed from the catalyst feeding port 19.

[0069] like Figure 3 As shown, the catalyst regenerator 5 is provided with a coking tank 501 and a regenerated catalyst recovery section 502 from bottom to top inside. The coking tank 501 is used for decoking the coking catalyst.

[0070] The waste heat boiler 12 is used to initially recover the heat generated in the catalytic reaction regeneration section B, and to produce steam to power the raw material gasification section A. Specifically, as follows: Figure 1 As shown, boiler feedwater c1 enters waste heat boiler 12 and exchanges heat with flue gas d generated by catalyst regenerator 5 to generate steam e1. Steam e1 with a volume fraction of 90% supplies energy to raw material gasification section A. After heating acetic acid a and liquid ammonia b, it is converted into condensate m. The remaining steam e1 goes to steam pipeline 20 to achieve energy reuse. The condensate m can also be used as boiler feedwater to produce steam in this system, realizing the recycling of materials.

[0071] The raw material pretreatment section B includes a raw material vaporization section and a raw material preheating section. The raw material vaporization section and the raw material preheating section are used to shorten the reaction time of the raw material in the riser reactor 4, reducing the reaction time to 4 seconds, thereby shortening the regeneration cycle of the coking catalyst in the catalyst regenerator 5, reducing the regeneration cycle to 4 seconds.

[0072] The raw material vaporization section includes an acetic acid vaporizer 2 and a liquid ammonia vaporizer 1. The heat required by the acetic acid vaporizer 2 and the liquid ammonia vaporizer 1 is provided by the material sent from the waste heat boiler 12 of the catalytic reaction regeneration section B, thereby realizing energy reuse.

[0073] The raw material preheating section A includes an acetic acid preheater 302 and an ammonia preheater 301. The heat required by the acetic acid preheater 302 and the ammonia preheater 301 is provided by the material sent from the riser reactor 4 of the catalytic reaction regeneration section B, thereby realizing energy reuse.

[0074] A falling film evaporator 13 is provided between the riser reactor 4 in the raw material preheating section B and the distillation section C. The heat required by the falling film evaporator 13 is provided by the material sent out from the raw material preheating section B, so as to realize energy reuse.

[0075] The air supply device includes a smoke machine 9, a blower 10 and a motor 11. The smoke machine 9 recovers the pressure energy of the catalyst regenerator 5 and drives the blower 10 to blow air f into the catalyst regenerator 5 to achieve energy reuse. The motor 11 is a backup power supply device used to supplement the kinetic energy of the blower 10.

[0076] The catalytic reaction regeneration section B also includes an external heat exchanger 8, which is used to stabilize the temperature of the catalyst regenerator 5. Boiler feedwater c2 enters the external heat exchanger 8, and the extracted waste heat is used to produce steam e2, which is then transported to the steam pipeline network 20 to achieve energy reuse.

[0077] The distillation section C includes a gas-liquid separator 14 and distillation columns 15 and 16. The gas-liquid separator 14 is used to separate crude acetonitrile product and send the ammonia in the crude acetonitrile product back to the riser reactor 4 in the catalytic reaction regeneration section B to participate in the catalytic reaction again. The distillation columns 15 and 16 are used for the distillation of the crude acetonitrile product after removing ammonia. That is, the main function of distillation column 15 is to separate substances with boiling points higher than acetonitrile from acetonitrile in the system, which mainly refers to the separation of water and acetonitrile. Distillation column 16 is used to separate substances with boiling points lower than acetonitrile from acetonitrile in the system. Finally, the finished product acetonitrile i is obtained, wherein the conversion rate of acetic acid is 99%, the selectivity of acetonitrile is 98%, and the purity of acetonitrile after separation is 99.5 wt%.

[0078] The crude acetonitrile product contains acetonitrile, water, ammonium acetate, acetamide, ammonia, acetic acid, and nitrogen-containing organic matter. In this embodiment, based on the total mass of the crude acetonitrile product, acetonitrile accounts for 53 wt% and water accounts for 46 wt%.

[0079] The denitrification section D includes an SCR reactor 17 and a waste heat boiler 18. The SCR reactor 17 is used to purify the flue gas d from the catalytic reaction regeneration section B and the waste gas g from the distillation section C. The flue gas d contains nitrogen oxides, and the waste gas g is ammonia. The denitrified gas h after being treated by the SCR reactor 17 enters the waste heat boiler 18 and exchanges heat with the boiler feedwater 3c3 to produce steam 3e3, which is then transported to the steam pipeline network 20 to achieve energy reuse.

[0080] In this embodiment, using Figure 1 The steps for continuous acetonitrile production in the acetic acid amination system are as follows:

[0081] (1) Pretreatment: The raw materials acetic acid a and liquid ammonia b are vaporized by acetic acid vaporizer 2 and liquid ammonia vaporizer 1 in the raw material vaporization section A, respectively. The vaporized acetic acid gas and ammonia gas are then heated by acetic acid preheater 302 and ammonia preheater 301 in the raw material preheating section A.

[0082] (2) Catalytic reaction: The acetic acid gas and ammonia gas heated in step (1) enter the riser reactor 4 from the bottom of the riser reactor 4 in the catalytic reaction regeneration section B. Under the action of the catalyst, they react to produce crude acetonitrile product, which includes intermediates ammonium acetate and acetamide. The crude acetonitrile product enters the acetic acid preheater 302 and ammonia preheater 301 in the raw material preheating section A from the top of the riser reactor 4 to supply energy to the raw material preheating section A. The catalytic chemical reactions involved are as follows:

[0083]

[0084] Wherein, M1 is acetic acid gas, M2 is ammonia gas, M3 is ammonium acetate, M4 is acetamide, and M5 is acetonitrile;

[0085] (3) Catalyst regeneration: After the reaction in step (2), the coked catalyst enters the catalyst regenerator 5 through the regeneration slide valve 7 and reacts with the air f blown in by the blower 10 to burn off the coke on the catalyst and become a regenerated catalyst that can participate in the reaction again, and generates flue gas d. The regenerated catalyst enters the riser reactor 4 through the regeneration slide valve 6 to participate in the catalytic reaction again, realizing the recycling of the catalyst.

[0086] (4) Crude acetonitrile distillation: The crude acetonitrile product after primary cooling in the raw material preheating section A in step (2) enters the falling film evaporator 13 for secondary cooling. The crude acetonitrile product after secondary cooling enters the gas-liquid separator 14 in the distillation section C for gas-liquid separation. The gas is ammonia, which is discharged from the top of the gas-liquid separator 14 and then incorporated into the acetic acid gas and ammonia gas heated in step (1). The liquid is the crude acetonitrile product after removing ammonia. It is then sequentially distilled into distillation column 15 and distillation column 26 to obtain the finished product acetonitrile i, while generating... Wastewater j and waste gas g, wherein wastewater j contains intermediate ammonium acetate and acetamide and nitrogen-containing organic matter, 30% of the total mass of wastewater j is returned to falling film evaporator 13 for concentration, and steam e4 is generated and sent to steam pipeline 20 to realize energy recovery. The concentrated material k is combined with acetic acid gas, ammonia gas and ammonia gas discharged from gas-liquid separator 14 after heating in step (1) and enters riser reactor 4 to participate in catalytic reaction again. The remaining wastewater j is discharged to wastewater treatment station 21 for treatment and discharged after meeting the standards.

[0087] (5) Denitrification: The flue gas d generated in step (3) and the waste gas g generated in step (4) are combined and then enter the SCR reactor 17 in the denitrification section for denitrification reaction to obtain denitrified gas h, which is then sent to the waste heat boiler 18 to recover heat and then sent to the chimney 22 for emission in compliance with standards. The flue gas d contains nitrogen oxides and the waste gas g is ammonia.

[0088] In step (1), the molar ratio of raw material acetic acid a and liquid ammonia b is 1:1.05, and the temperature of acetic acid gas and ammonia gas after heating is 300℃.

[0089] In step (2), the top pressure in the riser reactor 4 is 210 kPa and the top pressure in the catalyst regenerator 5 is 230 kPa. The top pressures are controlled by valves and heat exchangers installed on the riser reactor 4 or the catalyst regenerator 5. The circulation of the catalyst is achieved by the pressure difference between the riser reactor 4 and the catalyst regenerator 5. The pressure difference between the riser reactor 4 and the catalyst regenerator 5 is 80 kPa and the pressure difference between the catalyst regenerator 4 and the riser reactor 5 is 110 kPa. At the same time, it can also prevent the material in the riser reactor 4 from entering the catalyst regenerator 5.

[0090] The mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section B in step (2) to the amount of catalyst stored in the riser reactor 4 is 1.1:1.8.

[0091] In step (2), the catalyst in the riser reactor 4 is selected from ZSM-5 molecular sieve. The catalyst is in powder form with a particle size range of 40-100 μm and a D50 value of 60 μm, where D50 is the particle size value corresponding to a cumulative distribution percentage of 50%.

[0092] In step (2), the reaction temperature of riser reactor 4 is 400℃ and the reaction cycle duration is 4s.

[0093] In step (3), the reaction temperature in the catalyst regenerator 5 is 600℃ and the regeneration cycle time is 4s.

[0094] The reaction temperature in the catalyst regenerator 5 in step (3) is 600℃.

[0095] In step (3), a CO combustion improver is also introduced to help accelerate the catalyst regeneration rate. The proportion of the CO combustion improver added is 0.01 wt% of the catalyst circulation volume.

[0096] The nitrogen oxide content of the flue gas in step (3) is 0.3 wt%.

[0097] In step (4), the conversion rate of acetic acid is 99%, the selectivity of acetonitrile is 98%, and the purity of acetonitrile after distillation is 99.5 wt%.

[0098] The mass contents of the intermediates ammonium acetate and acetamide in the wastewater of step (4) are 3 wt% and 5 wt%, respectively.

[0099] In step (5), the temperature of the SCR reactor 17 is 300°C.

[0100] In step (5), the oxygen content of the denitrification gas is 3 wt%, and the nitrogen oxide content is less than 100 ppm.

[0101] Example 2

[0102] like Figure 1 As shown, this embodiment provides a system for the continuous production of acetonitrile by ammoniation of acetic acid. The system includes, in sequence according to the material flow direction, a raw material pretreatment section A, a catalytic reaction regeneration section B, a distillation section C, and a denitrification section D, thereby realizing catalyst recycling and continuous energy-saving production of acetonitrile.

[0103] The raw material pretreatment section A includes a liquid ammonia vaporizer 1, an acetic acid vaporizer 2, an ammonia preheater 301, and an acetic acid preheater 302.

[0104] The catalytic reaction regeneration section B includes a riser reactor 4, a catalyst regenerator 5, a gas supply device, and a waste heat boiler 12. The riser reactor 4 and the catalyst regenerator 5 are connected by a waiting slide valve 7 and a regeneration slide valve 6. The coking catalyst after reaction enters the catalyst regenerator 5 from the riser reactor 4 through the waiting slide valve 7, and the regenerated catalyst returns from the catalyst regenerator 5 to the riser reactor 4 through the regeneration slide valve 6. The circulation of the catalyst is achieved by the pressure difference between the riser reactor 4 and the catalyst regenerator 5. The pressure difference between the riser reactor 4 and the catalyst regenerator 5 is 85 kPa, and the pressure difference between the catalyst regenerator 5 and the riser reactor 4 is 110 kPa. This prevents the material in the riser reactor 4 from entering the catalyst regenerator 5.

[0105] The mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section B to the amount of catalyst stored in the riser reactor 4 is 1.3:1.8.

[0106] like Figure 2 As shown, the riser reactor 4 is provided with reaction section I 401, reaction section II 402, and coking catalyst recovery section 403 from bottom to top. The diameter of reaction section I 401 is smaller than that of reaction section II 402, and the diameter of reaction section II 402 is smaller than that of catalyst recovery section 403. All three reaction sections I 401, reaction section II 402, and coking catalyst recovery section 403 contain catalyst.

[0107] In this embodiment, the system can operate continuously for 20 months. After 20 months of continuous operation, without stopping the entire system, 60% of the total catalyst mass in the riser reactor 4 can be removed as discarded catalyst, and then an equal mass of fresh catalyst can be added. This maintains the constant catalyst mass in the riser reactor 4 and the stability of the overall system. The riser reactor 4 is provided with a catalyst feeding port 19 on the outside for adding fresh catalyst or removing discarded catalyst. Before adding fresh catalyst, discarded catalyst is removed from the catalyst feeding port 19.

[0108] like Figure 3 As shown, the catalyst regenerator 5 is provided with a coking tank 501 and a regenerated catalyst recovery section 502 from bottom to top inside. The coking tank 501 is used for decoking the coking catalyst.

[0109] The waste heat boiler 12 is used to initially recover the heat generated in the catalytic reaction regeneration section B, and to produce steam to power the raw material gasification section A. Specifically, as follows: Figure 1As shown, boiler feedwater c1 enters waste heat boiler 12 and exchanges heat with flue gas d generated by catalyst regenerator 5 to generate steam e1. Steam e1 with a volume fraction of 86% supplies energy to raw material gasification section A. After heating acetic acid a and liquid ammonia b, it is converted into condensate m. The remaining steam e1 goes to steam pipeline 20 to achieve energy reuse. The condensate m can also be used as boiler feedwater to produce steam in this system, realizing the recycling of materials.

[0110] The raw material pretreatment section B includes a raw material vaporization section and a raw material preheating section. The raw material vaporization section and the raw material preheating section are used to shorten the reaction time of the raw material in the riser reactor 4, reducing the reaction time to 4.5s, thereby shortening the regeneration cycle of the coking catalyst in the catalyst regenerator 5, reducing the regeneration cycle to 4.5s.

[0111] The raw material vaporization section includes an acetic acid vaporizer 2 and a liquid ammonia vaporizer 1. The heat required by the acetic acid vaporizer 2 and the liquid ammonia vaporizer 1 is provided by the material sent from the waste heat boiler 12 of the catalytic reaction regeneration section B, thereby realizing energy reuse.

[0112] The raw material preheating section A includes an acetic acid preheater 302 and an ammonia preheater 301. The heat required by the acetic acid preheater 302 and the ammonia preheater 301 is provided by the material sent from the riser reactor 4 of the catalytic reaction regeneration section B, thereby realizing energy reuse.

[0113] A falling film evaporator 13 is provided between the riser reactor 4 in the raw material preheating section B and the distillation section C. The heat required by the falling film evaporator 13 is provided by the material sent out from the raw material preheating section B, so as to realize energy reuse.

[0114] The air supply device includes a smoke machine 9, a blower 10 and a motor 11. The smoke machine 9 recovers the pressure energy of the catalyst regenerator 5 and drives the blower 10 to blow air f into the catalyst regenerator 5 to achieve energy reuse. The motor 11 is a backup power supply device used to supplement the kinetic energy of the blower 10.

[0115] The catalytic reaction regeneration section B also includes an external heat exchanger 8, which is used to stabilize the temperature of the catalyst regenerator 5. Boiler feedwater c2 enters the external heat exchanger 8, and the extracted waste heat is used to produce steam e2, which is then transported to the steam pipeline network 20 to achieve energy reuse.

[0116] The distillation section C includes a gas-liquid separator 14 and distillation columns 15 and 16. The gas-liquid separator 14 is used to separate crude acetonitrile product and send the ammonia in the crude acetonitrile product back to the riser reactor 4 in the catalytic reaction regeneration section B to participate in the catalytic reaction again. The distillation columns 15 and 16 are used for the distillation of the crude acetonitrile product after removing ammonia. That is, the main function of distillation column 15 is to separate substances with boiling points higher than acetonitrile from acetonitrile in the system, which mainly refers to the separation of water and acetonitrile. Distillation column 16 is used to separate substances with boiling points lower than acetonitrile from acetonitrile in the system. Finally, the finished product acetonitrile i is obtained, wherein the conversion rate of acetic acid is 99%, the selectivity of acetonitrile is 96.5%, and the purity of acetonitrile after separation is 99.4 wt%.

[0117] The crude acetonitrile product contains acetonitrile, water, ammonium acetate, acetamide, ammonia, acetic acid, and nitrogen-containing organic matter. In this embodiment, based on the total mass of the crude acetonitrile product, acetonitrile accounts for 52.3 wt% and water accounts for 46 wt%.

[0118] The denitrification section D includes an SCR reactor 17 and a waste heat boiler 18. The SCR reactor 17 is used to purify the flue gas d from the catalytic reaction regeneration section B and the waste gas g from the distillation section C. The flue gas d contains nitrogen oxides, and the waste gas g is ammonia. The denitrified gas h after being treated by the SCR reactor 17 enters the waste heat boiler 18 and exchanges heat with the boiler feedwater 3c3 to produce steam 3e3, which is then transported to the steam pipeline network 20 to achieve energy reuse.

[0119] use Figure 1 The steps for continuous acetonitrile production in the acetic acid amination system are as follows:

[0120] (1) Pretreatment: The raw materials acetic acid a and liquid ammonia b are vaporized by acetic acid vaporizer 2 and liquid ammonia vaporizer 1 in the raw material vaporization section A, respectively. The vaporized acetic acid gas and ammonia gas are then heated by acetic acid preheater 302 and ammonia preheater 301 in the raw material preheating section A.

[0121] (2) Catalytic reaction: The acetic acid gas and ammonia gas heated in step (1) enter the riser reactor 4 from the bottom of the riser reactor 4 in the catalytic reaction regeneration section B. Under the action of the catalyst, they react to produce crude acetonitrile product, which includes intermediates ammonium acetate and acetamide. The crude acetonitrile product enters the acetic acid preheater 302 and ammonia preheater 301 in the raw material preheating section A from the top of the riser reactor 4 to supply energy to the raw material preheating section A. The catalytic chemical reactions involved are as follows:

[0122]

[0123] Wherein, M1 is acetic acid gas, M2 is ammonia gas, M3 is ammonium acetate, M4 is acetamide, and M5 is acetonitrile;

[0124] (3) Catalyst regeneration: After the reaction in step (2), the coked catalyst enters the catalyst regenerator 5 through the regeneration slide valve 7 and reacts with the air f blown in by the blower 10 to burn off the coke on the catalyst and become a regenerated catalyst that can participate in the reaction again, and generates flue gas d. The regenerated catalyst enters the riser reactor 4 through the regeneration slide valve 6 to participate in the catalytic reaction again, realizing the recycling of the catalyst.

[0125] (4) Crude acetonitrile distillation: The crude acetonitrile product after primary cooling in the raw material preheating section A in step (2) enters the falling film evaporator 13 for secondary cooling. The crude acetonitrile product after secondary cooling enters the gas-liquid separator 14 in the distillation section C for gas-liquid separation. The gas is ammonia, which is discharged from the top of the gas-liquid separator 14 and then incorporated into the acetic acid gas and ammonia gas heated in step (1). The liquid is the crude acetonitrile product after removing ammonia. It is then sequentially distilled into distillation column 15 and distillation column 26 to obtain the finished product acetonitrile i, while generating... Wastewater j and waste gas g, wherein wastewater j contains intermediate ammonium acetate and acetamide and nitrogen-containing organic matter, 36% of the total mass of wastewater j is returned to falling film evaporator 13 for concentration, and steam e4 is generated and sent to steam pipeline 20 to realize energy recovery. The concentrated material k is combined with acetic acid gas, ammonia gas and ammonia gas discharged from gas-liquid separator 14 after heating in step (1) and enters riser reactor 4 to participate in catalytic reaction again. The remaining wastewater j is discharged to wastewater treatment station 21 for treatment and discharged after meeting the standards.

[0126] (5) Denitrification: The flue gas d generated in step (3) and the waste gas g generated in step (4) are combined and then enter the SCR reactor 17 in the denitrification section for denitrification reaction to obtain denitrified gas h, which is then sent to the waste heat boiler 18 to recover heat and then sent to the chimney 22 for emission in compliance with standards. The flue gas d contains nitrogen oxides and the waste gas g is ammonia.

[0127] In step (1), the molar ratio of raw material acetic acid a and liquid ammonia b is 1:1.07, and the temperature of acetic acid gas and ammonia gas after heating is 300℃.

[0128] In step (2), the top pressure in the riser reactor 4 is 208 kPa and the top pressure in the catalyst regenerator 5 is 225 kPa. The top pressures are controlled by valves and heat exchangers installed on the riser reactor 4 or the catalyst regenerator 5. The circulation of the catalyst is achieved by the pressure difference between the riser reactor 4 and the catalyst regenerator 5. The pressure difference between the riser reactor 4 and the catalyst regenerator 5 is 85 kPa and the pressure difference between the catalyst regenerator 4 and the riser reactor 5 is 110 kPa. At the same time, it can also prevent the material in the riser reactor 4 from entering the catalyst regenerator 5.

[0129] In step (2), the mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section B to the amount of catalyst stored in the riser reactor 4 is 1.3:1.8.

[0130] In step (2), the catalyst in the riser reactor 4 is selected from Ti-Si molecular sieves. The catalyst is in powder form with a particle size range of 40-100 μm and a D50 value of 63 μm.

[0131] In step (2), the reaction temperature of riser reactor 4 is 408℃ and the reaction cycle time is 4.5s.

[0132] In step (3), the reaction temperature in the catalyst regenerator 5 is 610°C and the regeneration cycle time is 4.5s.

[0133] The reaction temperature in the catalyst regenerator 5 in step (3) is 610℃.

[0134] In step (3), a CO combustion improver is also introduced to help accelerate the catalyst regeneration rate. The proportion of the CO combustion improver added is 0.015 wt% of the catalyst circulation volume.

[0135] The nitrogen oxide content of the flue gas in step (3) is 0.32 wt%.

[0136] In step (4), the conversion rate of acetic acid is 99%, the selectivity of acetonitrile is 96.5%, and the purity of acetonitrile after distillation is 99.4 wt%.

[0137] The mass contents of the intermediates ammonium acetate and acetamide in the wastewater of step (4) are 3.6 wt% and 5.4 wt%, respectively.

[0138] In step (5), the temperature of the SCR reactor 17 is 300°C.

[0139] In step (5), the oxygen content of the denitrification gas is 3 wt%, and the nitrogen oxide content is less than 100 ppm.

[0140] Example 3

[0141] like Figure 1 As shown, this embodiment provides a system for the continuous production of acetonitrile by ammoniation of acetic acid. The system includes, in sequence according to the material flow direction, a raw material pretreatment section A, a catalytic reaction regeneration section B, a distillation section C, and a denitrification section D, thereby realizing catalyst recycling and continuous energy-saving production of acetonitrile.

[0142] The raw material pretreatment section A includes a liquid ammonia vaporizer 1, an acetic acid vaporizer 2, an ammonia preheater 301, and an acetic acid preheater 302.

[0143] The catalytic reaction regeneration section B includes a riser reactor 4, a catalyst regenerator 5, a gas supply device, and a waste heat boiler 12. The riser reactor 4 and the catalyst regenerator 5 are connected by a waiting slide valve 7 and a regeneration slide valve 6. The coking catalyst after reaction enters the catalyst regenerator 5 from the riser reactor 4 through the waiting slide valve 7, and the regenerated catalyst returns from the catalyst regenerator 5 to the riser reactor 4 through the regeneration slide valve 6. The circulation of the catalyst is achieved by the pressure difference between the riser reactor 4 and the catalyst regenerator 5. The pressure difference between the riser reactor 4 and the catalyst regenerator 5 is 90 kPa, and the pressure difference between the catalyst regenerator 5 and the riser reactor 4 is 115 kPa. This prevents the material in the riser reactor 4 from entering the catalyst regenerator 5.

[0144] The mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section B to the amount of catalyst stored in the riser reactor 4 is 1.6:1.8.

[0145] like Figure 2 As shown, the riser reactor 4 is provided with reaction section I 401, reaction section II 402, and coking catalyst recovery section 403 from bottom to top. The diameter of reaction section I 401 is smaller than that of reaction section II 402, and the diameter of reaction section II 402 is smaller than that of catalyst recovery section 403. All three reaction sections I 401, reaction section II 402, and coking catalyst recovery section 403 contain catalyst.

[0146] In this embodiment, the system can operate continuously for 18 months. After 18 months of continuous operation, without stopping the entire system, 75% of the total catalyst mass in the riser reactor 4 can be removed as discarded catalyst, and then an equal mass of fresh catalyst can be added. This maintains the constant catalyst mass in the riser reactor 4 and the stability of the overall system. The riser reactor 4 is provided with a catalyst feeding port 19 on the outside for adding fresh catalyst or removing discarded catalyst. Before adding fresh catalyst, discarded catalyst is removed from the catalyst feeding port 19.

[0147] like Figure 3As shown, the catalyst regenerator 5 is provided with a coking tank 501 and a regenerated catalyst recovery section 502 from bottom to top inside. The coking tank 501 is used for decoking the coking catalyst.

[0148] The waste heat boiler 12 is used to initially recover the heat generated in the catalytic reaction regeneration section B, and to produce steam to power the raw material gasification section A. Specifically, as follows: Figure 1 As shown, boiler feedwater c1 enters waste heat boiler 12 and exchanges heat with flue gas d generated by catalyst regenerator 5 to generate steam e1. Steam e1 with a volume fraction of 90% supplies energy to raw material gasification section A. After heating acetic acid a and liquid ammonia b, it is converted into condensate m. The remaining steam e1 goes to steam pipeline 20 to achieve energy reuse. The condensate m can also be used as boiler feedwater to produce steam in this system, realizing the recycling of materials.

[0149] The raw material pretreatment section B includes a raw material vaporization section and a raw material preheating section. The raw material vaporization section and the raw material preheating section are used to shorten the reaction time of the raw material in the riser reactor 4, reducing the reaction time to 5.2s, thereby shortening the regeneration cycle of the coking catalyst in the catalyst regenerator 5, reducing the regeneration cycle to 5.2s.

[0150] The raw material vaporization section includes an acetic acid vaporizer 2 and a liquid ammonia vaporizer 1. The heat required by the acetic acid vaporizer 2 and the liquid ammonia vaporizer 1 is provided by the material sent from the waste heat boiler 12 of the catalytic reaction regeneration section B, thereby realizing energy reuse.

[0151] The raw material preheating section A includes an acetic acid preheater 302 and an ammonia preheater 301. The heat required by the acetic acid preheater 302 and the ammonia preheater 301 is provided by the material sent from the riser reactor 4 of the catalytic reaction regeneration section B, thereby realizing energy reuse.

[0152] A falling film evaporator 13 is provided between the riser reactor 4 in the raw material preheating section B and the distillation section C. The heat required by the falling film evaporator 13 is provided by the material sent out from the raw material preheating section B, so as to realize energy reuse.

[0153] The air supply device includes a smoke machine 9, a blower 10 and a motor 11. The smoke machine 9 recovers the pressure energy of the catalyst regenerator 5 and drives the blower 10 to blow air f into the catalyst regenerator 5 to achieve energy reuse. The motor 11 is a backup power supply device used to supplement the kinetic energy of the blower 10.

[0154] The catalytic reaction regeneration section B also includes an external heat exchanger 8, which is used to stabilize the temperature of the catalyst regenerator 5. Boiler feedwater c2 enters the external heat exchanger 8, and the extracted waste heat is used to produce steam e2, which is then transported to the steam pipeline network 20 to achieve energy reuse.

[0155] The distillation section C includes a gas-liquid separator 14 and distillation columns 15 and 16. The gas-liquid separator 14 is used to separate crude acetonitrile product and send the ammonia in the crude acetonitrile product back to the riser reactor 4 in the catalytic reaction regeneration section B to participate in the catalytic reaction again. The distillation columns 15 and 16 are used for the distillation of the crude acetonitrile product after removing ammonia. That is, the main function of distillation column 15 is to separate substances with boiling points higher than acetonitrile from acetonitrile in the system, which mainly refers to the separation of water and acetonitrile. Distillation column 16 is used to separate substances with boiling points lower than acetonitrile from acetonitrile in the system. Finally, the finished product acetonitrile i is obtained, wherein the conversion rate of acetic acid is 99%, the selectivity of acetonitrile is 95%, and the purity of acetonitrile after separation is 99.1 wt%.

[0156] The crude acetonitrile product contains acetonitrile, water, ammonium acetate, acetamide, ammonia, acetic acid, and nitrogen-containing organic matter. In this embodiment, based on the total mass of the crude acetonitrile product, acetonitrile accounts for 50.2 wt% and water accounts for 45.8 wt%.

[0157] The denitrification section D includes an SCR reactor 17 and a waste heat boiler 18. The SCR reactor 17 is used to purify the flue gas d from the catalytic reaction regeneration section B and the waste gas g from the distillation section C. The flue gas d contains nitrogen oxides, and the waste gas g is ammonia. The denitrified gas h after being treated by the SCR reactor 17 enters the waste heat boiler 18 and exchanges heat with the boiler feedwater 3c3 to produce steam 3e3, which is then transported to the steam pipeline network 20 to achieve energy reuse.

[0158] In this embodiment, using Figure 1 The steps for continuous acetonitrile production in the acetic acid amination system are as follows:

[0159] (1) Pretreatment: The raw materials acetic acid a and liquid ammonia b are vaporized by acetic acid vaporizer 2 and liquid ammonia vaporizer 1 in the raw material vaporization section A, respectively. The vaporized acetic acid gas and ammonia gas are then heated by acetic acid preheater 302 and ammonia preheater 301 in the raw material preheating section A.

[0160] (2) Catalytic reaction: The acetic acid gas and ammonia gas heated in step (1) enter the riser reactor 4 from the bottom of the riser reactor 4 in the catalytic reaction regeneration section B. Under the action of the catalyst, they react to produce crude acetonitrile product, which includes intermediates ammonium acetate and acetamide. The crude acetonitrile product enters the acetic acid preheater 302 and ammonia preheater 301 in the raw material preheating section A from the top of the riser reactor 4 to supply energy to the raw material preheating section A. The catalytic chemical reactions involved are as follows:

[0161]

[0162] Wherein, M1 is acetic acid gas, M2 is ammonia gas, M3 is ammonium acetate, M4 is acetamide, and M5 is acetonitrile;

[0163] (3) Catalyst regeneration: After the reaction in step (2), the coked catalyst enters the catalyst regenerator 5 through the regeneration slide valve 7 and reacts with the air f blown in by the blower 10 to burn off the coke on the catalyst and become a regenerated catalyst that can participate in the reaction again, and generates flue gas d. The regenerated catalyst enters the riser reactor 4 through the regeneration slide valve 6 to participate in the catalytic reaction again, realizing the recycling of the catalyst.

[0164] (4) Crude acetonitrile distillation: The crude acetonitrile product after primary cooling in the raw material preheating section A in step (2) enters the falling film evaporator 13 for secondary cooling. The crude acetonitrile product after secondary cooling enters the gas-liquid separator 14 in the distillation section C for gas-liquid separation. The gas is ammonia, which is discharged from the top of the gas-liquid separator 14 and then incorporated into the acetic acid gas and ammonia gas heated in step (1). The liquid is the crude acetonitrile product after removing ammonia. It is then sequentially distilled into distillation column 15 and distillation column 26 to obtain the finished product acetonitrile i, while generating... Wastewater j and waste gas g, wherein wastewater j contains intermediate ammonium acetate and acetamide and nitrogen-containing organic matter, 40% of the total mass of wastewater j is returned to falling film evaporator 13 for concentration, and steam e4 is generated and sent to steam pipeline 20 to realize energy recovery. The concentrated material k is combined with acetic acid gas, ammonia gas and ammonia gas discharged from gas-liquid separator 14 after heating in step (1) and enters riser reactor 4 to participate in catalytic reaction again. The remaining wastewater j is discharged to wastewater treatment station 21 for treatment and discharged after meeting the standards.

[0165] (5) Denitrification: The flue gas d generated in step (3) and the waste gas g generated in step (4) are combined and then enter the SCR reactor 17 in the denitrification section for denitrification reaction to obtain denitrified gas h, which is then sent to the waste heat boiler 18 to recover heat and then sent to the chimney 22 for emission in compliance with standards. The flue gas d contains nitrogen oxides and the waste gas g is ammonia.

[0166] In step (1), the molar ratio of raw material acetic acid a and liquid ammonia b is 1:1.10, and the temperature of acetic acid gas and ammonia gas after heating is 320℃.

[0167] In step (2), the top pressure in the riser reactor 4 is 220 kPa and the top pressure in the catalyst regenerator 5 is 240 kPa. The top pressure is controlled by valves and heat exchangers installed on the riser reactor 4 or the catalyst regenerator 5. The circulation of the catalyst is achieved by the pressure difference between the riser reactor 4 and the catalyst regenerator 5. The pressure difference between the riser reactor 4 and the catalyst regenerator 5 is 90 kPa and the pressure difference between the catalyst regenerator 4 and the riser reactor 5 is 115 kPa. At the same time, it can also prevent the material in the riser reactor 4 from entering the catalyst regenerator 5.

[0168] The mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section B in step (2) to the amount of catalyst stored in the riser reactor 4 is 1.6:1.8.

[0169] In step (2), the catalyst in the riser reactor 4 is selected from acid-modified γ-Al2O3. The catalyst is in powder form with a particle size range of 40-100 μm and a D50 value of 70 μm.

[0170] In step (2), the reaction temperature of riser reactor 4 is 450°C and the reaction cycle duration is 6s.

[0171] In step (3), the reaction temperature in catalyst regenerator 5 is 660°C and the regeneration cycle time is 6s.

[0172] The reaction temperature in the catalyst regenerator 5 in step (3) is 660°C.

[0173] In step (3), a CO combustion improver is also introduced to help accelerate the catalyst regeneration rate. The proportion of the CO combustion improver added is 0.02 wt% of the catalyst circulation volume.

[0174] The nitrogen oxide content of the flue gas in step (3) is 0.5 wt%.

[0175] In step (4), the conversion rate of acetic acid is 99%, the selectivity of acetonitrile is 95%, and the purity of acetonitrile after distillation is 99.1 wt%.

[0176] The mass contents of the intermediates ammonium acetate and acetamide in the wastewater of step (4) are 5 wt% and 7 wt%, respectively.

[0177] In step (5), the temperature of the SCR reactor 17 is 300°C.

[0178] In step (5), the oxygen content of the denitrification gas is 4 wt%, and the nitrogen oxide content is less than 100 ppm.

[0179] Example 4

[0180] like Figure 4 As shown, this embodiment provides a system for the continuous production of acetonitrile by ammoniation of acetic acid. The system includes, in sequence according to the material flow direction, a raw material pretreatment section A, a catalytic reaction regeneration section B, a distillation section C, and a denitrification section D, thereby realizing catalyst recycling and continuous energy-saving production of acetonitrile.

[0181] The raw material pretreatment section A includes a liquid ammonia vaporizer 1, an acetic acid vaporizer 2, and a preheater 3. The difference from Examples 1-3 is that this example combines the ammonia preheater 301 and the acetic acid preheater 302 in Examples 1-3 into a single preheater 3, thus saving process costs.

[0182] The catalytic reaction regeneration section B includes a riser reactor 4, a catalyst regenerator 5, a gas supply device, and a waste heat boiler 12. The riser reactor 4 and the catalyst regenerator 5 are connected by a waiting slide valve 7 and a regeneration slide valve 6. The coking catalyst after reaction enters the catalyst regenerator 5 from the riser reactor 4 through the waiting slide valve 7, and the regenerated catalyst returns from the catalyst regenerator 5 to the riser reactor 4 through the regeneration slide valve 6. The circulation of the catalyst is achieved by the pressure difference between the riser reactor 4 and the catalyst regenerator 5. The pressure difference between the riser reactor 4 and the catalyst regenerator 5 is 85 kPa, and the pressure difference between the catalyst regenerator 5 and the riser reactor 4 is 105 kPa. This prevents the material in the riser reactor 4 from entering the catalyst regenerator 5.

[0183] The mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section B to the amount of catalyst stored in the riser reactor 4 is 1.1:1.8.

[0184] like Figure 2 As shown, the riser reactor 4 is provided with reaction section I 401, reaction section II 402, and coking catalyst recovery section 403 from bottom to top. The diameter of reaction section I 401 is smaller than that of reaction section II 402, and the diameter of reaction section II 402 is smaller than that of catalyst recovery section 403. All three reaction sections I 401, reaction section II 402, and coking catalyst recovery section 403 contain catalyst.

[0185] In this embodiment, the system can operate continuously for 18 months. After 18 months of continuous operation, without stopping the entire system, 50% of the total catalyst mass in the riser reactor 4 can be removed as discarded catalyst, and then an equal mass of fresh catalyst can be added. This maintains the constant catalyst mass in the riser reactor 4 and the stability of the overall system. The riser reactor 4 is provided with a catalyst feeding port 19 on the outside for adding fresh catalyst or removing discarded catalyst. Before adding fresh catalyst, discarded catalyst is removed from the catalyst feeding port 19.

[0186] like Figure 3 As shown, the catalyst regenerator 5 is provided with a coking tank 501 and a regenerated catalyst recovery section 502 from bottom to top inside. The coking tank 501 is used for decoking the coking catalyst.

[0187] The waste heat boiler 12 is used to initially recover the heat generated in the catalytic reaction regeneration section B, and to produce steam to power the raw material gasification section A. Specifically, as follows: Figure 4 As shown, boiler feedwater c1 enters waste heat boiler 12 and exchanges heat with flue gas d generated by catalyst regenerator 5 to generate steam e1. Steam e1 with a volume fraction of 90% supplies energy to raw material gasification section A. After heating acetic acid a and liquid ammonia b, it is converted into condensate m. The remaining steam e1 goes to steam pipeline 20 to achieve energy reuse. The condensate m can also be used as boiler feedwater to produce steam in this system, realizing the recycling of materials.

[0188] The raw material pretreatment section B includes a raw material vaporization section and a raw material preheating section. The raw material vaporization section and the raw material preheating section are used to shorten the reaction time of the raw material in the riser reactor 4, reducing the reaction time to 4 seconds, thereby shortening the regeneration cycle of the coking catalyst in the catalyst regenerator 5, reducing the regeneration cycle to 4 seconds.

[0189] The raw material vaporization section includes an acetic acid vaporizer 2 and a liquid ammonia vaporizer 1. The heat required by the acetic acid vaporizer 2 and the liquid ammonia vaporizer 1 is provided by the material sent from the waste heat boiler 12 of the catalytic reaction regeneration section B, thereby realizing energy reuse.

[0190] The raw material preheating section A includes a preheater 3. The heat required by the preheater 3 is provided by the material sent from the riser reactor 4 of the catalytic reaction regeneration section B, thereby realizing energy reuse.

[0191] A falling film evaporator 13 is provided between the riser reactor 4 in the raw material preheating section B and the distillation section C. The heat required by the falling film evaporator 13 is provided by the material sent out from the raw material preheating section B, so as to realize energy reuse.

[0192] The air supply device includes a smoke machine 9, a blower 10 and a motor 11. The smoke machine 9 recovers the pressure energy of the catalyst regenerator 5 and drives the blower 10 to blow air f into the catalyst regenerator 5 to achieve energy reuse. The motor 11 is a backup power supply device used to supplement the kinetic energy of the blower 10.

[0193] The catalytic reaction regeneration section B also includes an external heat exchanger 8, which is used to stabilize the temperature of the catalyst regenerator 5. Boiler feedwater c2 enters the external heat exchanger 8, and the extracted waste heat is used to produce steam e2, which is then transported to the steam pipeline network 20 to achieve energy reuse.

[0194] The distillation section C includes a gas-liquid separator 14 and distillation columns 15 and 16. The gas-liquid separator 14 is used to separate crude acetonitrile product and send the ammonia in the crude acetonitrile product back to the riser reactor 4 in the catalytic reaction regeneration section B to participate in the catalytic reaction again. The distillation columns 15 and 16 are used for the distillation of the crude acetonitrile product after removing ammonia. That is, the main function of distillation column 15 is to separate substances with boiling points higher than acetonitrile from acetonitrile in the system, which mainly refers to the separation of water and acetonitrile. Distillation column 16 is used to separate substances with boiling points lower than acetonitrile from acetonitrile in the system. Finally, the finished product acetonitrile i is obtained, wherein the conversion rate of acetic acid is 99%, the selectivity of acetonitrile is 97%, and the purity of acetonitrile after separation is 99.5 wt%.

[0195] The crude acetonitrile product contains acetonitrile, water, ammonium acetate, acetamide, ammonia, acetic acid, and nitrogen-containing organic matter. In this embodiment, based on the total mass of the crude acetonitrile product, acetonitrile accounts for 52.5 wt% and water accounts for 46 wt%.

[0196] The denitrification section D includes an SCR reactor 17 and a waste heat boiler 18. The SCR reactor 17 is used to purify the flue gas d from the catalytic reaction regeneration section B and the waste gas g from the distillation section C. The flue gas d contains nitrogen oxides, and the waste gas g is ammonia. The denitrified gas h after being treated by the SCR reactor 17 enters the waste heat boiler 18 and exchanges heat with the boiler feedwater 3c3 to produce steam 3e3, which is then transported to the steam pipeline network 20 to achieve energy reuse.

[0197] use Figure 4 The steps for continuous acetonitrile production in the acetic acid amination system are as follows:

[0198] (1) Pretreatment: The raw materials acetic acid a and liquid ammonia b are vaporized by acetic acid vaporizer 2 and liquid ammonia vaporizer 1 in the raw material vaporization section A, respectively. The vaporized acetic acid gas and ammonia gas are combined and then heated by preheater 3 in the raw material preheating section A.

[0199] (2) Catalytic reaction: The acetic acid gas and ammonia gas heated in step (1) enter the riser reactor 4 from the bottom of the riser reactor 4 in the catalytic reaction regeneration section B. They react under the action of the catalyst to generate crude acetonitrile product, which includes intermediates ammonium acetate and acetamide. The crude acetonitrile product enters the preheater 3 in the raw material preheating section A directly from the top of the riser reactor 4 to supply energy to the raw material preheating section A. The catalytic chemical reactions involved are as follows:

[0200]

[0201] Wherein, M1 is acetic acid gas, M2 is ammonia gas, M3 is ammonium acetate, M4 is acetamide, and M5 is acetonitrile;

[0202] (3) Catalyst regeneration: After the reaction in step (2), the coked catalyst enters the catalyst regenerator 5 through the regeneration slide valve 7 and reacts with the air f blown in by the blower 10 to burn off the coke on the catalyst and become a regenerated catalyst that can participate in the reaction again, and generates flue gas d. The regenerated catalyst enters the riser reactor 4 through the regeneration slide valve 6 to participate in the catalytic reaction again, realizing the recycling of the catalyst.

[0203] (4) Crude acetonitrile distillation: The crude acetonitrile product after primary cooling in the raw material preheating section A in step (2) enters the falling film evaporator 13 for secondary cooling. The crude acetonitrile product after secondary cooling enters the gas-liquid separator 14 in the distillation section C for gas-liquid separation. The gas is ammonia, which is discharged from the top of the gas-liquid separator 14 and then incorporated into the acetic acid gas and ammonia gas heated in step (1). The liquid is the crude acetonitrile product after removing ammonia. It is then sequentially distilled into distillation column 15 and distillation column 26 to obtain the finished product acetonitrile i, while generating... Wastewater j and waste gas g, wherein wastewater j contains intermediate ammonium acetate and acetamide and nitrogen-containing organic matter, 30% of the total mass of wastewater j is returned to falling film evaporator 13 for concentration, and steam e4 is generated and sent to steam pipeline 20 to realize energy recovery. The concentrated material k is combined with acetic acid gas, ammonia gas and ammonia gas discharged from gas-liquid separator 14 after heating in step (1) and enters riser reactor 4 to participate in catalytic reaction again. The remaining wastewater j is discharged to wastewater treatment station 21 for treatment and discharged after meeting the standards.

[0204] (5) Denitrification: The flue gas d generated in step (3) and the waste gas g generated in step (4) are combined and then enter the SCR reactor 17 in the denitrification section for denitrification reaction to obtain denitrified gas h, which is then sent to the waste heat boiler 18 to recover heat and then sent to the chimney 22 for emission in compliance with standards. The flue gas d contains nitrogen oxides and the waste gas g is ammonia.

[0205] In step (1), the molar ratio of raw material acetic acid a and liquid ammonia b is 1:1.06, and the temperature of acetic acid gas and ammonia gas after heating is 290℃.

[0206] In step (2), the top pressure in the riser reactor 4 is 210 kPa and the top pressure in the catalyst regenerator 5 is 230 kPa. The top pressures are controlled by valves and heat exchangers installed on the riser reactor 4 or the catalyst regenerator 5. The circulation of the catalyst is achieved by the pressure difference between the riser reactor 4 and the catalyst regenerator 5. The pressure difference between the riser reactor 4 and the catalyst regenerator 5 is 85 kPa and the pressure difference between the catalyst regenerator 4 and the riser reactor 5 is 105 kPa. At the same time, it can also prevent the material in the riser reactor 4 from entering the catalyst regenerator 5.

[0207] The mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section B in step (2) to the amount of catalyst stored in the riser reactor 4 is 1.1:1.8.

[0208] In step (2), the catalyst used in the riser reactor 4 is a ZSM-5 molecular sieve catalyst. The catalyst is in powder form with a particle size range of 40–100 μm and a D50 value of 60 μm.

[0209] In step (2), the reaction temperature of riser reactor 4 is 400℃ and the reaction cycle duration is 4s.

[0210] In step (3), the reaction temperature in the catalyst regenerator 5 is 600℃ and the regeneration cycle time is 4s.

[0211] The reaction temperature in the catalyst regenerator 5 in step (3) is 600℃.

[0212] In step (3), a CO combustion improver is also introduced to help accelerate the catalyst regeneration rate. The proportion of the CO combustion improver added is 0.01 wt% of the catalyst circulation volume.

[0213] The nitrogen oxide content of the flue gas in step (3) is 0.32 wt%.

[0214] In step (4), the conversion rate of acetic acid is 99%, the selectivity of acetonitrile is 97%, and the purity of acetonitrile after distillation is 99.5 wt%.

[0215] The mass contents of the intermediates ammonium acetate and acetamide in the wastewater of step (4) are 3 wt% and 5 wt%, respectively.

[0216] In step (5), the temperature of the SCR reactor 17 is 300°C.

[0217] In step (5), the oxygen content of the denitrification gas is 3 wt%, and the nitrogen oxide content is less than 100 ppm.

[0218] In summary, for the entire continuous acetic acid amination to acetonitrile system, the catalytic regeneration section B is the core section. Other sections (raw material pretreatment section A, distillation section C, and denitrification section D) cooperate with it to achieve optimal results. This system can regenerate the coking catalyst directly within the system without removing it, achieving catalyst recycling and meeting the requirements for long-term operation. Furthermore, compared to existing technologies that require shutdown and catalyst replacement every 6-7 months, this invention allows for the replenishment of fresh catalyst without shutdown, and does not require complete catalyst replacement. The replacement catalyst mass is 50-75 wt% of the original process, ultimately achieving an acetic acid conversion rate of ≥98%, an acetonitrile selectivity of ≥95%, and an acetonitrile purity of ≥99 wt%.

[0219] It should be understood that the present invention is not limited to the processes and contents described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for the continuous production of acetonitrile by ammoniation of acetic acid, characterized in that, Includes the following steps: (1) Pretreatment: The raw materials acetic acid and liquid ammonia are vaporized by the acetic acid vaporizer and liquid ammonia vaporizer in the raw material vaporization section, respectively. The vaporized acetic acid gas and ammonia gas are then heated by the acetic acid preheater and ammonia preheater in the raw material preheating section. (2) Catalytic reaction: The acetic acid gas and ammonia gas heated in step (1) enter the riser reactor from the bottom of the riser reactor in the catalytic reaction regeneration section. Under the action of the catalyst, the reaction takes place at a temperature of 360-450℃ and a reaction cycle of 3-6s, producing crude acetonitrile product, which includes intermediates ammonium acetate and acetamide. The crude acetonitrile product is sent out from the top of the riser reactor and enters the acetic acid preheater and ammonia preheater in the raw material preheating section to supply energy to the raw material preheating section. The catalytic chemical reactions involved are: Wherein, M1 is acetic acid gas, M2 is ammonia gas, M3 is ammonium acetate, M4 is acetamide, and M5 is acetonitrile; (3) Catalyst regeneration: The coked catalyst after the reaction in step (2) enters the catalyst regenerator through the regeneration slide valve and reacts with the air blown in by the blower to burn off the coke on the catalyst and generate a regenerated catalyst to participate in the reaction again, and generate flue gas. The regenerated catalyst enters the riser reactor through the regeneration slide valve to participate in the catalytic reaction again, realizing the recycling of the catalyst. The reaction temperature in the catalyst regenerator is 600-700℃, and the regeneration cycle time is 3-6s. (4) Crude acetonitrile distillation: The crude acetonitrile product after the first cooling stage of the raw material preheating section in step (2) enters the falling film evaporator for the second cooling stage. The crude acetonitrile product after the second cooling stage enters the gas-liquid separator in the distillation section for gas-liquid separation. The gas is ammonia gas, which is discharged from the top of the gas-liquid separator and then merged into the acetic acid gas and ammonia gas after heating in step (1). The liquid is the crude acetonitrile product after removing ammonia gas. It enters the first distillation column and the second distillation column for distillation in sequence to obtain the finished acetonitrile product. At the same time, wastewater and waste gas are generated. Among them, the wastewater contains intermediate ammonium acetate and acetamide and nitrogen-containing organic matter. 30-50% of the total wastewater mass is returned to the falling film evaporator for concentration. At the same time, steam is generated and sent to the steam pipeline network. The concentrated material is combined with the acetic acid gas, ammonia gas and ammonia gas discharged from the gas-liquid separator after heating in step (1) and enters the riser reactor to participate in the catalytic reaction again. The remaining wastewater is discharged to the wastewater treatment station for treatment and discharged after meeting the standards. (5) Denitrification: The flue gas generated in step (3) and the waste gas generated in step (4) are combined and then enter the selective catalytic reduction reactor in the denitrification section to carry out the denitrification reaction, obtain denitrified gas, and then enter the waste heat boiler to recover heat and discharge in compliance with standards. The flue gas contains nitrogen oxides and the waste gas is ammonia.

2. The method for continuous production of acetonitrile by ammoniation of acetic acid according to claim 1, characterized in that, The method employs a system for the continuous production of acetonitrile via acetic acid ammoniation. This system, in accordance with the material flow direction, includes a raw material pretreatment section, a catalytic reaction regeneration section, a distillation section, and a denitrification section. The system operates continuously for 18 to 24 months. The raw material pretreatment section includes a raw material vaporization section and a raw material preheating section; The catalytic reaction regeneration section includes a riser reactor, a catalyst regenerator, a gas supply device, and a waste heat boiler. The distillation section includes a gas-liquid separator and a distillation column; The denitrification section includes a selective catalytic reduction reactor and a waste heat boiler.

3. The method for continuous production of acetonitrile by ammoniation of acetic acid according to claim 2, characterized in that, The riser reactor and the catalyst regenerator are connected by a pre-regeneration slide valve and a regeneration slide valve. The catalyst after reaction, i.e., the coking catalyst, enters the catalyst regenerator from the riser reactor through the pre-regeneration slide valve. The regenerated catalyst, i.e., the regenerated catalyst, returns to the riser reactor from the catalyst regenerator through the regeneration slide valve. The circulation of the catalyst is achieved by the pressure difference between the riser reactor and the catalyst regenerator. The pressure difference between the riser reactor and the catalyst regenerator is 80-90 kPa, and the pressure difference between the catalyst regenerator and the riser reactor is 100-110 kPa, which can prevent the material in the riser reactor from entering the catalyst regenerator.

4. The method for continuous production of acetonitrile by ammoniation of acetic acid according to claim 3, characterized in that, The mass ratio of the amount of catalyst circulating in the catalytic reaction regeneration section to the amount of catalyst stored in the riser reactor is (1-1.5):(1-1.8).

5. The method for continuous production of acetonitrile by ammoniation of acetic acid according to claim 3, characterized in that, The riser reactor is provided with reaction section I, reaction section II, and coking catalyst recovery section from bottom to top. The diameter of reaction section I is smaller than that of reaction section II, and the diameter of reaction section II is smaller than that of coking catalyst recovery section. All three reaction sections contain catalyst.

6. The method for continuous production of acetonitrile by ammoniation of acetic acid according to claim 3, characterized in that, The catalyst regenerator is equipped with a coking tank and a regenerated catalyst recovery section from bottom to top. The coking tank is used to remove coke from the coking catalyst.

7. The method for continuous production of acetonitrile by ammoniation of acetic acid according to claim 2, characterized in that, The raw material vaporization section includes an acetic acid vaporizer and a liquid ammonia vaporizer. The heat required by the acetic acid vaporizer and the liquid ammonia vaporizer is provided by the material sent from the waste heat boiler of the catalytic reaction regeneration section. The raw material preheating section includes an acetic acid preheater and an ammonia preheater. The heat required by the acetic acid preheater and the ammonia preheater is provided by the material sent from the riser reactor of the catalytic reaction regeneration section.

8. The method for continuous production of acetonitrile by ammoniation of acetic acid according to claim 6, characterized in that, The gas-liquid separator is used to separate crude acetonitrile product and send the ammonia in the crude acetonitrile product back to the riser reactor in the catalytic reaction regeneration section to participate in the catalytic reaction again. The distillation column is used to distill the crude acetonitrile product after removing ammonia to obtain the finished acetonitrile product, wherein the conversion rate of acetic acid is ≥98%, the selectivity of acetonitrile is ≥95%, and the purity of acetonitrile is ≥99wt%.

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