Device and method for generating glycolonitrile through reaction of gas-phase hydrocyanic acid

Abstract

The invention discloses a device and a method for generating hydroxyacetonitrile through reaction of gas-phase hydrocyanic acid. The device comprises a hydroxylation reaction tower I and a hydroxylation reaction tower II. Gas-phase hydrocyanic acid enters the first hydroxylation reaction tower from a tower kettle inlet of the first hydroxylation reaction tower to react with a formaldehyde solution, and the proportion, temperature and pH of raw materials and the retention time of the materials in the glycolonitrile reaction kettle are controlled; unreacted gas-phase hydrocyanic acid is conveyed to a tower kettle gas-phase inlet of the second hydroxylation reaction tower from a tower top gas-phase outlet of the second hydroxylation reaction tower to continuously react with fresh formaldehyde, and completely reacted glycolonitrile tower kettle liquid is conveyed to the first hydroxylation reaction tower. According to the invention, gas-phase hydrocyanic acid is directly reacted with formaldehyde, the conditions of the reaction process are controlled, the reaction rate is accelerated, the residence time of tower bottoms is prolonged, meanwhile, the emission of cyanogen-containing waste gas is reduced, the utilization rate of raw materials and the production safety are improved, and the purpose of continuously producing formaldehyde with the content of 1t is achieved; the content of the hydrocyanic acid is less than or equal to 1%.

Description

Technical Field

[0001] The present invention relates to a chemical production device, in particular to a device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid. The present invention also relates to a method for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid. Background Art

[0002] Hydroxyacetonitrile, also known as glycolonitrile or formaldehyde cyanohydrin, is a colorless to pale yellow organic compound with strong toxicity, corrosiveness, and tear-inducing properties. As a key raw material for the production of chemicals such as glycine, malononitrile, and indigo dye, the quality of hydroxyacetonitrile directly impacts its applications and the production process of downstream products.

[0003] Currently, the most common hydroxyacetonitrile chemical is produced by the direct reaction of formaldehyde and liquid hydrocyanic acid. However, industrial production often faces challenges with storing liquid hydrocyanic acid and the presence of formaldehyde, hydrocyanic acid, or both impurities in hydroxyacetonitrile, making it difficult to safely and stably produce high-quality hydroxyacetonitrile products on a continuous basis. Furthermore, the hydroxyacetonitrile production process generates waste products containing hydrocyanic acid, which are difficult for companies to handle. This not only poses a threat to the safety of operators but also poses a significant risk to the environment.

[0004] Therefore, a method and device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid are needed to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to provide a device for generating hydroxyacetonitrile by reacting gaseous phase hydrocyanic acid, wherein the device can produce hydroxyacetonitrile by adopting gaseous phase hydrocyanic acid.

[0006] Another object of the present invention is to provide a method for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid, which method can continuously produce hydroxyacetonitrile having a formaldehyde content of <0.08% and a hydrocyanic acid content of ≤1%.

[0007] The first technical solution adopted by the present invention is a device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid, comprising a first hydroxylation reaction tower and a second hydroxylation reaction tower with the same internal structure, wherein the internal structure is sequentially provided with a wire mesh demister, a spray plate, a water distributor and structured packing from top to bottom; The top of the first hydroxylation reaction tower is provided with a tower gas outlet, the bottom is provided with a finished liquid outlet, and the side wall is provided with a gaseous hydrocyanic acid inlet below the structured packing and above the bottom liquid; The top of the second hydroxylation reaction tower is provided with an outlet for non-condensable gas containing cyanide, the bottom is provided with a second tower outlet, and the side wall is provided with a second tower inlet below the structured packing and above the bottom liquid; The gas outlet of the first tower is connected to the inlet of the second tower through a pipeline, and the production outlet of the second tower is connected to the spray plate inlet of the first hydroxylation reaction tower through a pipeline and the production pump of the second tower.

[0008] The first technical solution of the present invention is also characterized in that: Both the first hydroxylation reaction tower and the second hydroxylation reaction tower include a cooling circulation system, specifically: A tower kettle circulation outlet is provided at the bottom of the first hydroxylation reaction tower. The tower kettle circulation outlet is connected to a tower circulation pump and a tower cooler in sequence through a pipeline, and is finally connected to the spray plate inlet of the first hydroxylation reaction tower. A second tower kettle circulation outlet is provided at the bottom of the second hydroxylation reaction tower. The second tower kettle circulation outlet is connected to the second tower circulation pump and the second tower cooler in sequence through pipelines, and is finally connected to the spray plate inlet of the second hydroxylation reaction tower.

[0009] Both the first and second hydroxylation reaction towers include temperature monitoring systems, specifically: A temperature online detector 1 is provided on the side wall of the first hydroxylation reaction tower located in the bottom liquid of the tower, and a program-controlled valve 2 is provided on the outlet pipe of the first tower circulation pump, and the temperature online detector 1 is associated with the program-controlled valve 2; A temperature online detector 2 is located on the side wall of the second hydroxylation reaction tower in the bottom liquid. A program-controlled valve 4 is provided on the outlet pipe of the second tower circulation pump, and the temperature online detector 2 is associated with the program-controlled valve 4.

[0010] Both the first and second hydroxylation reaction towers include a liquid level monitoring system, specifically: A liquid level online detector 1 is installed on the side wall of the hydroxylation reaction tower 1 located in the bottom liquid of the tower, and a program-controlled valve 3 is installed on the outlet pipe of the production pump of the second tower. The liquid level online detector 1 is associated with the program-controlled valve 3; A second liquid level online detector is provided on the side wall of the second hydroxylation reaction tower located in the bottom liquid of the tower. A program-controlled valve five is provided on the formaldehyde solution delivery pipeline. The second liquid level online detector is associated with the program-controlled valve five.

[0011] The first hydroxylation reaction tower includes a production system, specifically: An analytical online detector is installed on the side wall of the hydroxylation reaction tower located in the bottom liquid. A tower bottom production pump and a program-controlled valve are sequentially installed on the production pipeline of the finished liquid production outlet. The analytical online detector is associated with the program-controlled valve.

[0012] The structured packing consists of two pieces stacked one on top of the other and uses 350Y corrugated packing.

[0013] The second technical solution adopted by the present invention is a method for generating hydroxyacetonitrile by gas-phase hydrocyanic acid reaction, using the above-mentioned device for generating hydroxyacetonitrile by gas-phase hydrocyanic acid reaction, comprising the following steps: Step 1: delivering gaseous hydrocyanic acid with a volume percentage of not less than 75% from the gaseous hydrocyanic acid inlet into the first hydroxylation reaction tower, and simultaneously delivering a formaldehyde solution with a mass percentage of 37-55% into the spray plate of the second hydroxylation reaction tower, wherein the formaldehyde solution is mixed with sodium glycolate, and the mass ratio of sodium glycolate to formaldehyde is (0.1-0.5):100; Step 2: starting the extraction pump of the second tower to transport the bottom liquid of the hydroxylation reaction tower 2 from the extraction outlet of the second tower to the spray plate of the hydroxylation reaction tower 1. After being evenly dispersed by the spray plate and the water distributor, the bottom liquid of the hydroxylation reaction tower 2 is countercurrently contacted with the gaseous hydrogen cyanide transferred upward on the surface of the structured packing to cause a hydroxylation reaction. The generated hydroxyacetonitrile is extracted through the finished liquid extraction outlet. The unreacted gaseous hydrogen cyanide in the hydroxylation reaction tower 1 enters the inlet of the second tower after passing through the mesh demister, transfers mass upward in the hydroxylation reaction tower 2, and contacts with the formaldehyde solution dispersed by the spray plate and water distributor of the hydroxylation reaction tower 2 in countercurrent on the surface of the structured packing to cause hydroxylation reaction. The generated hydroxyacetonitrile and unreacted formaldehyde form the bottom liquid, and the non-condensable gas after the reaction is discharged from the cyanide-containing non-condensable gas outlet.

[0014] The second technical solution of the present invention is also characterized in that: Both the first and second hydroxylation reaction towers include a cooling circulation system and a temperature monitoring system, specifically: A tower kettle circulation outlet is provided at the bottom of the first hydroxylation reaction tower. The tower kettle circulation outlet is connected to a tower circulation pump and a tower cooler in sequence through pipelines, and is ultimately connected to the spray plate inlet of the first hydroxylation reaction tower. A first online temperature detector is provided on the side wall of the first hydroxylation reaction tower below the structured packing. A second program-controlled valve is provided on the outlet pipe of the first tower circulation pump. The first online temperature detector is associated with the second program-controlled valve. A second tower kettle circulation outlet is provided at the bottom of the second hydroxylation reaction tower. The second tower kettle circulation outlet is connected to the second tower circulation pump and the second tower cooler in sequence through a pipeline, and is ultimately connected to the spray plate inlet of the second hydroxylation reaction tower. A second online temperature detector is located on the side wall of the second hydroxylation reaction tower below the structured packing. A fourth programmable valve is provided on the outlet pipe of the second tower circulation pump. The second online temperature detector is associated with the fourth programmable valve. In step 2, the cooling circulation system is started at the same time, specifically: Start the circulation pump of tower 1 and tower 2, A circulating pump in tower 1 extracts the bottom liquid from the bottom circulation outlet of tower 1 and transports it to a cooler in tower 1 for heat exchange with cooling water to reduce the temperature. An online temperature detector monitors the temperature of the bottom liquid in the hydroxylation reaction tower 1 in real time. When the temperature of the bottom liquid exceeds 10-30°C, a programmable valve 2 opens, thereby increasing the amount of cooling water entering the cooler in tower 1. The second tower circulation pump extracts the bottom liquid from the second tower bottom circulation outlet and transports it to the second tower cooler for heat exchange with cooling water for cooling; the temperature online detector 2 monitors the temperature of the bottom liquid in the hydroxylation reaction tower 2 in real time. When it is detected that the bottom liquid temperature exceeds 10-30℃, the programmable valve 4 opens, thereby increasing the cooling water entering the second tower cooler.

[0015] Both the first and second hydroxylation reaction towers include a liquid level monitoring system. The first hydroxylation reaction tower also includes a withdrawal system, specifically: The side wall of the first hydroxylation reaction tower below the structured packing is equipped with a liquid level online detector 1 and an analysis online detector. The outlet pipe of the second tower production pump is equipped with a program-controlled valve 3, and the liquid level online detector 1 is associated with the program-controlled valve 3. The production pipe of the finished liquid production outlet is equipped with a tower kettle production pump and a program-controlled valve 1 in sequence, and the analysis online detector is associated with the program-controlled valve 1. A second liquid level online detector is provided on the side wall of the second hydroxylation reaction tower below the structured packing, and a program-controlled valve five is provided on the formaldehyde solution delivery pipeline. The second liquid level online detector is associated with the program-controlled valve five. In step 2, the liquid level monitoring system and the extraction system are started simultaneously, specifically: Start the production pump of tower 1 and the production pump of tower 2. When the online detector detects that the formaldehyde content in the bottom liquid of the hydroxylation reaction tower is less than 0.08% and the hydrocyanic acid content is less than 1%, the program-controlled valve is opened to extract the bottom liquid; The liquid level online detector 1 monitors the liquid level of the hydroxylation reaction tower 1 in real time. When the liquid level is detected to be lower than the preset value, the program-controlled valve 3 opens, thereby increasing the liquid delivery rate of the bottom of the hydroxylation reaction tower 2; The liquid level online detector 2 monitors the liquid level of the hydroxylation reaction tower 2 in real time. When the liquid level is detected to be lower than the preset value, the program-controlled valve 5 opens, thereby increasing the flow rate of the formaldehyde solution entering the hydroxylation reaction tower 2.

[0016] A pressure regulating device is installed at the outlet of the cyanide-containing non-condensable gas, and the pressure in the hydroxylation reaction tower 1 and the hydroxylation reaction tower 2 is controlled by the pressure regulating device to maintain at -0.02-0.02MPa.

[0017] The beneficial effects of the present invention are: 1. The present device uses gaseous hydrocyanic acid to generate hydroxyacetonitrile, fundamentally avoiding the significant safety hazards associated with the high toxicity and volatility of liquid hydrocyanic acid during storage, transportation, and use, such as leakage and poisoning. Since gaseous hydrocyanic acid participates in the reaction in gaseous form, the reaction system is more airtight, effectively reducing the risk of direct contact with operators. Furthermore, the continuous production mode achieves a stable and controllable reaction process by controlling the reaction temperature, pressure, and material flow rate.

[0018] 2. The device of the present invention adopts a two-stage hydroxylation reaction tower to collaboratively produce hydroxyacetonitrile. During the reaction process, gaseous hydrocyanic acid and liquid formaldehyde solution contact in a countercurrent manner. This mass transfer mode significantly prolongs the residence time of formaldehyde and hydrocyanic acid in the reaction system. The countercurrent contact allows the gas and liquid phases to be fully mixed and reacted in each stage of the reactor, effectively improving the reaction depth, increasing the efficiency of the hydroxyacetonitrile reaction, and reducing the emission of cyanide-containing waste gas.

[0019] 3. The circulation system of the two-stage reaction tower of the present invention can control the temperature and pH value during the hydroxyacetonitrile reaction process. By adjusting the reaction temperature and pH value, the hydroxylation reaction can be carried out at the optimal temperature and pH value, accelerating the reaction rate while reducing the occurrence of side reactions. This significantly reduces the amount of unreacted formaldehyde and hydrocyanic acid residues in the hydroxyacetonitrile product, and can continuously produce high-quality hydroxyacetonitrile with a formaldehyde content of less than 0.08% and a hydrocyanic acid content of ≤1%.

[0020] Furthermore, the pH regulator of the present invention uses sodium glycolate, and the hydroxyacetonitrile product prepared using the pH regulator is colorless and transparent, which not only meets the stringent requirements of high-end application fields on product appearance and purity, but also reduces the processing costs of subsequent refining processes such as decolorization. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the device of the present invention.

[0022] Figure: 1. Hydroxylation reaction tower 1, 2. Hydroxylation reaction tower 2, 3. Gas outlet of tower 1, 4. Wire mesh demister 1, 5. Spray plate 1, 6. Spray head 1, 7. Water distributor 1, 8. Structured packing 1, 9. Structured packing 2, 11. Gas-phase hydrocyanic acid inlet, 12. Temperature online detector 1, 13. Analytical online detector, 14. Liquid level online detector 1, 15. Finished product liquid outlet, 16. Circulation outlet of tower 1, 19. Production pump of tower 1, 20. Program-controlled valve 1, 21. Circulation pump of tower 1, 23. Program-controlled valve 2, 24. Cooler of tower one, 29. Outlet of non-condensable gas containing cyanide, 30. Wire mesh demister two, 31. Spray plate two, 32. Spray head two, 33. Water distributor two, 34. Structured packing three, 36. Structured packing four, 37. Inlet of tower two, 38. Online temperature detector two, 39. Online liquid level detector two, 40. Program-controlled valve three, 41. Production pump of tower two, 42. Production outlet of tower two, 44. Kettle circulation outlet of tower two, 46. Circulation pump of tower two, 48. Program-controlled valve four, 49. Cooler of tower two, 51. Program-controlled valve five. DETAILED DESCRIPTION

[0023] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1 like Figure 1 As shown, the device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid in the present invention comprises a first hydroxylation reaction tower 1 and a second hydroxylation reaction tower 2 connected in series.

[0025] Inside the hydroxylation reaction tower 1, arranged from top to bottom are a wire mesh demister 4, a spray plate 5, a water distributor 7, a structured packing 8, and a structured packing 9. The wire mesh demister 4 has the same diameter as the hydroxylation reaction tower 1 and is fixed to the inner wall of the hydroxylation reaction tower 1. It is used to separate mist or droplets entrained by the rising gas in the tower. A tower gas outlet 3 is provided at the top of the hydroxylation reaction tower 1 for discharging the gas after the reaction in the tower; a finished liquid extraction port 15 is provided at the bottom for extracting qualified hydroxyacetonitrile product; a gaseous hydrogen cyanide inlet 11 is provided on the side wall, and the gaseous hydrogen cyanide inlet 11 is located in the structured packing 9 for receiving the raw gaseous hydrogen cyanide. The spray plate 5 is used to receive the formaldehyde solution. Several spray heads 6 are evenly distributed inside the spray plate 5 to evenly disperse the received formaldehyde solution. Below the structured packing 9 is the tower bottom, which is used to hold the tower bottom liquid. The tower bottom liquid accounts for 60-70% of the tower bottom volume. The gaseous hydrogen cyanide inlet 11 is located above the tower bottom liquid.

[0026] During production, gaseous hydrocyanic acid enters the hydroxylation reaction tower 1 through the gaseous hydrocyanic acid inlet 11 and transfers upward within the tower. Simultaneously, a formaldehyde solution is introduced into the spray plate 5. After being evenly dispersed by the spray head 6, the formaldehyde solution is dispersed through the water distributor 7 within the structured packing 8. The gaseous hydrocyanic acid and the formaldehyde solution meet in countercurrent within the structured packing 8 and structured packing 2 9, where a hydroxylation reaction occurs. The hydroxyacetonitrile produced by the reaction enters the bottom of the tower and, after passing testing, is withdrawn through the finished product liquid outlet 15. Unreacted gaseous hydrocyanic acid passes through the wire mesh demister 4 and is discharged through the tower gas outlet 3.

[0027] The internal structure of the second hydroxylation tower 2 is identical to that of the first hydroxylation tower 1. Arranged from top to bottom are a second wire mesh demister 30, a second spray tray 31, a second water distributor 33, a third structured packing 34, and a fourth structured packing 36. A cyanide-containing non-condensable gas outlet 29 is provided at the top of the second hydroxylation tower 2 for discharging the cyanide-containing non-condensable gas after the reaction. A second tower extraction outlet 42 is provided at the bottom. A second tower inlet 37 is provided on the sidewall, located below the fourth structured packing 36 and above the bottom liquid.

[0028] The inlet of spray plate 1 (5) is connected to the second tower extraction port (42) via a pipeline and the second tower extraction pump (41). The spray head (6) within the spray plate evenly disperses the bottoms liquid from the second hydroxylation tower (2), which contains unreacted formaldehyde from the second hydroxylation tower (2). The bottoms liquid dispersed by spray plate 1 (5) is further dispersed by water distributor 7 before evenly entering structured packing (8) and structured packing (9). There, it comes into countercurrent contact with gaseous hydrocyanic acid (hydrocyanic acid) introduced through gaseous hydrocyanic acid inlet (11). The hydroxylation reaction between formaldehyde and hydrocyanic acid occurs on the surface and in the interstices of the structured packing. The resulting hydroxyacetonitrile product is stored at the bottom of the first hydroxylation tower (1) and, after passing inspection, is withdrawn from the finished product extraction port (15).

[0029] The inlet 37 of the second tower is connected to the gas outlet 3 of the first tower, and the inlet of the second spray plate 31 is connected to the formaldehyde solution pipeline. A number of second spray heads 32 are evenly distributed in the second spray plate 31 for evenly dispersing the formaldehyde solution. The formaldehyde solution is further dispersed by the second water distributor 33 and enters the third structured packing 34 and the fourth structured packing 36. In the structured packing, it contacts the gas-phase hydrocyanic acid gas and liquid introduced from the inlet 37 of the second tower in reverse order to carry out the hydroxylation reaction of formaldehyde and hydrocyanic acid.

[0030] The present invention adopts a two-stage series reaction tower structure to achieve multiple reactions of the reaction materials. On the one hand, the unreacted formaldehyde in the hydroxylation reaction tower 2 is utilized to continue to participate in the reaction in the hydroxylation reaction tower 1, thereby improving the utilization rate of the formaldehyde; on the other hand, the unreacted gaseous hydrocyanic acid in the hydroxylation reaction tower 1 is utilized to continue to participate in the reaction in the hydroxylation reaction tower 2, thereby improving the utilization rate of the gaseous hydrocyanic acid. This method can reduce the cost of raw materials. At the same time, in each stage of the reaction tower of the present invention, the gaseous hydrocyanic acid and the liquid formaldehyde solution are reacted in a countercurrent manner in the structured packing. This method increases the gas-liquid mass transfer area and mass transfer time, allowing formaldehyde and hydrocyanic acid to fully contact each other, ultimately making the reaction more complete, and significantly improving the yield and purity of hydroxyacetonitrile.

[0031] Example 2 On the basis of Example 1, in this embodiment, both the first hydroxylation reaction tower 1 and the second hydroxylation reaction tower 2 are provided with a circulation system.

[0032] Specifically, a bottom recirculation outlet 16 is provided at the bottom of hydroxylation reaction tower 1. This outlet 16 is connected via a pipeline to the inlet of a tower circulation pump 21. The outlet of the tower circulation pump 21 is in turn connected via a pipeline to the inlet of a spray plate 5. Circulation pump 21 is used to transport the bottom liquid generated at the bottom of hydroxylation reaction tower 1 to spray plate 5 for further hydroxylation reaction. After being evenly dispersed within spray plate 5 by spray head 6, the bottom liquid re-enters hydroxylation reaction tower 1 to continuously undergo a hydroxylation reaction with gaseous hydrocyanic acid introduced through gaseous hydrocyanic acid inlet 11.

[0033] A second tower kettle circulation outlet 44 is provided at the bottom of the second hydroxylation reaction tower 2. The second tower kettle circulation outlet 44 is connected to the inlet of the second tower circulation pump 46 through a pipeline. The outlet of the second tower circulation pump 46 is connected to the inlet of the second spray plate 31 through a pipeline. The second tower circulation pump 46 is used to transport the bottom liquid of the second hydroxylation reaction tower 2 to the second spray plate 31, and the hydroxylation reaction is continuously carried out in the first hydroxylation reaction tower 1.

[0034] The circulation system can allow unreacted reactants in the bottom liquid to participate in the reaction again, thereby improving the conversion rate of the reactants and further increasing the yield of hydroxyacetonitrile.

[0035] Example 3 On the basis of Example 2, the circulation systems of the first hydroxylation reaction tower 1 and the second hydroxylation reaction tower 2 in this example are both provided with cooling structures.

[0036] Specifically, a tower cooler 24 is installed on the pipeline connecting the tower circulation pump 21 and the spray plate 5. A cooling water circulation channel is provided inside the tower cooler 24. By externally connecting cooling water at a temperature of -15°C to -5°C, the cooling water circulates in the channel, thereby taking away heat and reducing the temperature of the bottom liquid of the hydroxylation reaction tower 1 transported by the tower circulation pump 21.

[0037] Similarly, a second tower cooler 49 is installed on the pipeline connecting the second tower circulation pump 46 and the second spray plate 31. The structure and working principle of the second tower cooler 49 are the same as those of the first tower cooler 24, and is used to cool the circulating liquid in the bottom of the second hydroxylation reaction tower 2.

[0038] This cooling structure effectively addresses the issue of elevated material temperatures due to reaction exotherm, which can impact reaction efficiency. Furthermore, by controlling the temperature of the circulating liquid in the reactor, the reactor can be maintained within the optimal reaction temperature range, avoiding side reactions caused by excessively high temperatures and ultimately improving the purity of the hydroxyacetonitrile product.

[0039] Example 4 On the basis of Example 3, the first hydroxylation reaction tower 1 and the second hydroxylation reaction tower 2 in this embodiment are further provided with a temperature control system and a liquid level control system, so as to achieve more precise control of the reaction process.

[0040] Specifically, an online temperature detector 12 and an online liquid level detector 14 are installed on the side wall of the hydroxylation reaction tower 1, located at the bottom liquid position. A programmable valve 23 is installed in the outlet pipe of the first tower cooler 24. The programmable valve 23 is connected to the online temperature detector 12 and is used to control the temperature of the bottom liquid in the hydroxylation reaction tower 1, maintaining it at 10°C-30°C, preferably 15°C-20°C. The online temperature detector 12 monitors the temperature of the bottom liquid in the hydroxylation reaction tower 1 in real time and transmits the temperature signal to the control system. When it is detected that the bottom liquid temperature exceeds a preset range, the control system automatically adjusts the opening of the programmable valve 23 based on the temperature deviation, thereby controlling the flow of cooling water entering the first tower cooler 24. This precisely controls the temperature of the bottom liquid in the hydroxylation reaction tower 1, ensuring that the reaction proceeds at an appropriate temperature and improving reaction efficiency.

[0041] A programmable valve 3 (40) is installed on the outlet pipe of the second tower's extraction pump (41). This valve 3 (40) is connected to an online liquid level detector (14) to control the liquid level in the bottom of the hydroxylation reaction tower (1), maintaining it at 60%-70% of its height. The online liquid level detector (14) monitors the bottom of the hydroxylation reaction tower (1) in real time and feeds the level signal back to the control system. When the bottom of the hydroxylation reaction tower (1) changes, the control system automatically adjusts the opening of the programmable valve 3 (40) based on the level, delivering bottom liquid to the hydroxylation reaction tower (1), thereby achieving stable control of the bottom of the hydroxylation reaction tower (1).

[0042] Similarly, an online temperature detector 238 and an online liquid level detector 239 are installed on the sidewall of the second hydroxylation reaction tower 2 below the structured packing 236. A programmable valve 448 is installed in the outlet pipe of the second tower cooler 49. This valve is connected to the online temperature detector 238 and is used to control the temperature of the bottom liquid in the second hydroxylation reaction tower 2, maintaining it between 10°C and 30°C, preferably between 15°C and 20°C. A programmable valve 551 is installed in the formaldehyde solution delivery pipe and is connected to the online liquid level detector 239. This valve is used to control the formaldehyde solution feed rate and the bottom liquid level in the second hydroxylation reaction tower 2, maintaining the liquid level at 60%-70% of the bottom height.

[0043] Example 5 On the basis of Example 4, the hydroxylation reaction tower 1 in this embodiment is further provided with a finished product extraction system, which can effectively ensure that the extracted bottom liquid meets the product quality requirements.

[0044] Specifically, an analytical online detector 13 is installed on the side wall of the hydroxylation reaction tower 1 at the bottom liquid position. The detector can analyze and detect the composition of the bottom liquid in real time. A tower bottom extraction pump 19 and a programmable valve 20 are installed in sequence on the pipeline of the finished liquid extraction outlet 15. The programmable valve 20 is associated with the analytical online detector 13. The analytical online detector 13 continuously monitors the composition of the bottom liquid in the hydroxylation reaction tower 1. When the formaldehyde content in the bottom liquid is detected to be less than 0.08% and the hydrocyanic acid content is ≤1%, it means that the bottom liquid has reached the quality standard of the finished product. At this time, the analytical online detector 13 will transmit the detection signal to the control system. The control system controls the programmable valve 20 to open according to the signal, and the tower bottom extraction pump 19 starts to work to extract the bottom liquid that meets the quality requirements from the finished liquid extraction outlet 15. On the contrary, if the online analytical detector 13 detects that the formaldehyde content in the bottom liquid is ≥0.08% or the hydrocyanic acid content exceeds 1%, the control system will control the programmable valve 20 to remain in the closed state, and the bottom liquid will continue to remain in the hydroxylation reaction tower 1 to react until it meets the quality standard.

[0045] Example 6 On the basis of Example 5, in this embodiment, the structured packing 1 8, the structured packing 2 9, the structured packing 3 34 and the structured packing 4 36 all adopt 350Y corrugated packing, which has a corrugation angle of 45° and a specific surface area of ​​approximately 350 m² / m³, and can effectively disperse the liquid formaldehyde and provide sufficient specific surface area for the gaseous hydrogen cyanide and liquid formaldehyde, so that the countercurrent contact between the gas and liquid phases is more sufficient and the mass transfer and heat transfer are more sufficient.

[0046] In another embodiment of the present invention, a Roots blower is installed at the outlet 29 of the cyanide-containing non-condensable gas. The Roots blower is used to adjust the pressure of the hydroxylation reaction towers so that the pressure in the hydroxylation reaction tower 1 and the hydroxylation reaction tower 2 is maintained at -0.02-0.02 MPa. The gaseous hydrocyanic acid undergoes a hydroxylation reaction in the hydroxylation reaction tower 1 under a slightly negative pressure, and its residence time in the hydroxylation reaction tower 1 is controlled to be 10-30 minutes. The gaseous hydrocyanic acid that has not been completely reacted is transported to the hydroxylation reaction tower 2 using the slightly negative pressure as a power source, where it continues to undergo a hydroxylation reaction.

[0047] The method for continuously producing hydroxyacetonitrile with a formaldehyde content of less than 0.08% and a hydrocyanic acid content of less than 1% of the present invention comprises the following steps: Step 1: delivering gaseous hydrocyanic acid with a volume percentage of not less than 75% from the gaseous hydrocyanic acid inlet 11 into the first hydroxylation reaction tower 1; at the same time, delivering a formaldehyde solution with a mass percentage of 37-55% into the second spray plate 31 of the second hydroxylation reaction tower 2; Before the reaction, the present invention adds a pH adjuster to the formaldehyde solution. The pH adjuster is sodium glycolate, or sodium hydroxide and glycolic acid are added to the formaldehyde solution. The mass ratio of sodium glycolate to formaldehyde in the mixed solution is (0.1-0.5):100. The pH adjuster is used to control the pH of the hydroxylation reaction at 4.5-7.5, preferably 5.5-6, thereby regulating the progress of the hydroxylation reaction. The hydroxyacetonitrile product obtained using this pH adjuster is colorless and transparent.

[0048] Step 2, start the second tower production pump 41, the first tower circulation pump 21, the second tower circulation pump 46 and the first tower kettle production pump 19; The second-tower extraction pump 41 transports the bottom liquid of the second hydroxylation reaction tower 2 from the second-tower extraction port 42 to the spray plate 1 5. After being evenly dispersed by the spray plate 1 5 and the water distributor 1 7, the bottom liquid of the second hydroxylation reaction tower 2 undergoes countercurrent contact with the upwardly transferred gaseous hydrogen cyanide on the surface of the structured packing 1 8 and the structured packing 2 9 to cause a hydroxylation reaction. The generated hydroxyacetonitrile is extracted through the product liquid extraction port 15. The unreacted gaseous hydrogen cyanide in the hydroxylation reaction tower 1 enters the second tower inlet 37 after passing through the mesh demister 4, transfers upward in the hydroxylation reaction tower 2, and contacts the formaldehyde solution dispersed by the spray plate 2 31 and the water distributor 2 33 in countercurrent on the surface of the structured packing 3 34 and the structured packing 4 36 to cause a hydroxylation reaction. The generated hydroxyacetonitrile and unreacted formaldehyde form the tower bottom liquid, and the non-condensable gas after the reaction is discharged from the cyanide-containing non-condensable gas outlet 29.

[0049] Since the hydroxylation reaction is an exothermic reaction, the bottom liquid in the hydroxylation reaction tower will rise due to the heat released by the reaction. The first tower circulation pump 21 extracts the bottom liquid from the first tower bottom circulation outlet 16 and transports it to the first tower cooler 24 for heat exchange with cooling water. The cooled bottom liquid enters the spray plate 5 and the water distributor 7 for uniform dispersion, and then enters the hydroxylation reaction tower 1 to continue to participate in the hydroxylation reaction. At the same time, the temperature online detector 12 is associated with the program-controlled valve 23 to control the cooling water input amount of the hydroxylation reaction tower cooler 24 to reduce the reaction temperature in the hydroxylation reaction tower 1. Similarly, the second tower circulation pump 46 transports the bottom liquid from the second tower bottom circulation outlet 44 to the second tower cooler 49 for cooling. The temperature online detector 238 monitors the reaction temperature in real time and is associated with the programmable valve 44. When it is detected that the temperature exceeds the preset range, the programmable valve 44 is opened to allow cooling water to enter the second tower cooler 49 to cool the bottom liquid. The cooled bottom liquid is transported to the spray plate 231 and the water distributor 233 for dispersion to form a hydroxyacetonitrile solution containing formaldehyde; the non-condensable gas containing trace amounts of hydrocyanic acid after the hydroxylation reaction in the second tower 2 absorption reaction enters the cyanide-containing non-condensable gas outlet 29 and enters the tail gas absorption tower.

[0050] The online analytical instrument 13 analyzes and tests the composition of the bottom liquid in the hydroxylation reaction tower 1 in real time. When the formaldehyde content in the bottom liquid is detected to be less than 0.08% and the hydrocyanic acid content is ≤1%, the bottom liquid has met product quality requirements. At this point, the programmable valve 1 20 opens, and the bottom liquid is withdrawn via the tower 1 bottom pump 19. After the bottom liquid is withdrawn from the hydroxylation reaction tower 1, the liquid level drops. When the online liquid level detector 1 14 detects that the bottom liquid level is below a preset value, the programmable valve 3 40 opens, and the tower 2 bottom liquid pump 41 delivers the tower 2 bottom liquid to the spray plate 5. After dispersion, it is further dispersed in the water distributor 7 on the structured packing 1 8 and structured packing 2 9 of the hydroxylation reaction tower 1 to participate in the hydroxylation reaction. Similarly, when the liquid level in the hydroxylation reaction tower 2 drops and the online liquid level detector 2 39 detects that the bottom liquid level is below a preset value, the programmable valve 5 51 opens, increasing the input of formaldehyde solution to the input spray plate 2 31.

[0051] Example 1: At a temperature of 18.3°C and a pressure of -0.011 MPa, a 37% formaldehyde solution reacted with 93.2% gaseous hydrocyanic acid to obtain a hydroxyacetonitrile solution containing 0.63% hydrocyanic acid, 0.0% formaldehyde, and 49.44% hydroxyacetonitrile. The contents of hydroxyacetonitrile, formaldehyde, and hydrocyanic acid were determined according to the method in "Determination of the Contents of Hydroxyacetonitrile, Formaldehyde, and Hydrocyanic Acid in Industrial Hydroxyacetonitrile" SH / T 1803-2016.

[0052] Example 2: At a temperature of 16.2°C and a pressure of -0.008 MPa, a 37% formaldehyde solution reacted with 91.5% gaseous hydrocyanic acid to obtain a hydroxyacetonitrile solution containing 0.63% hydrocyanic acid, 0.0% formaldehyde, and 50.64% hydroxyacetonitrile. The contents of hydroxyacetonitrile, formaldehyde, and hydrocyanic acid were detected according to the method in "Determination of the Contents of Hydroxyacetonitrile, Formaldehyde, and Hydrocyanic Acid in Industrial Hydroxyacetonitrile" SH / T 1803-2016.

[0053] Example 3: At a temperature of 18.7°C and a pressure of -0.013 MPa, a 37% formaldehyde solution reacted with 93.3% gaseous hydrocyanic acid to obtain a hydroxyacetonitrile solution containing 0.46% hydrocyanic acid, 0.0% formaldehyde, and 52.39% hydroxyacetonitrile. The contents of hydroxyacetonitrile, formaldehyde, and hydrocyanic acid were determined according to the method in "Determination of the Contents of Hydroxyacetonitrile, Formaldehyde, and Hydrocyanic Acid in Industrial Hydroxyacetonitrile" SH / T 1803-2016.

[0054] Example 4: At a temperature of 16.4°C and a pressure of -0.010 MPa, a 37% formaldehyde solution reacted with 94.2% gaseous hydrocyanic acid to obtain a hydroxyacetonitrile solution containing 0.61% hydrocyanic acid, 0.0% formaldehyde, and 49.73% hydroxyacetonitrile. The contents of hydroxyacetonitrile, formaldehyde, and hydrocyanic acid were determined according to the method in "Determination of the Contents of Hydroxyacetonitrile, Formaldehyde, and Hydrocyanic Acid in Industrial Hydroxyacetonitrile" SH / T 1803-2016.

Claims

1. A device for generating hydroxyacetonitrile by reacting gaseous hydrogen cyanide, characterized in that: It comprises a hydroxylation reaction tower (1) and a hydroxylation reaction tower (2) having the same internal structure, wherein the internal structure is provided with a wire mesh demister, a spray plate, a water distributor and structured packing in sequence from top to bottom; The hydroxylation reaction tower (1) is provided with a tower gas outlet (3) at the top, a finished liquid outlet (15) at the bottom, and a gaseous hydrogen cyanide inlet (11) on the side wall below the structured packing and above the bottom liquid. The top of the second hydroxylation reaction tower (2) is provided with a cyanide-containing non-condensable gas outlet (29), the bottom is provided with a second tower extraction outlet (42), and the side wall is provided with a second tower inlet (37) below the structured packing and above the bottom liquid; The gas outlet (3) of the first tower is connected to the inlet (37) of the second tower via a pipeline, and the production outlet (42) of the second tower is connected to the spray plate inlet of the first hydroxylation reaction tower (1) via a pipeline and the production pump (41) of the second tower.

2. The device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid according to claim 1, characterized in that The first hydroxylation reaction tower (1) and the second hydroxylation reaction tower (2) both include a cooling circulation system, specifically: A tower kettle circulation outlet (16) is provided at the bottom of the hydroxylation reaction tower (1), and the tower kettle circulation outlet (16) is connected to a tower circulation pump (21) and a tower cooler (24) in sequence through pipelines, and is finally connected to the spray plate inlet of the hydroxylation reaction tower (1); A second tower kettle circulation outlet (44) is provided at the bottom of the second hydroxylation reaction tower (2). The second tower kettle circulation outlet (44) is connected to a second tower circulation pump (46) and a second tower cooler (49) in sequence through pipelines, and is finally connected to the spray plate inlet of the second hydroxylation reaction tower (2).

3. The device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid according to claim 2, characterized in that: The first hydroxylation reaction tower (1) and the second hydroxylation reaction tower (2) both include a temperature monitoring system, specifically: A temperature online detector (12) is provided on the side wall of the hydroxylation reaction tower (1) located in the bottom liquid of the tower, and a program-controlled valve (23) is provided on the outlet pipe of the tower circulation pump (21). The temperature online detector (12) is associated with the program-controlled valve (23). The second online temperature detector (38) is located on the side wall of the second tower (2) in the bottom liquid of the tower. A program-controlled valve (48) is provided on the outlet pipe of the second tower circulation pump (46). The second online temperature detector (38) is associated with the program-controlled valve (48).

4. The device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid according to claim 1, characterized in that The first hydroxylation reaction tower (1) and the second hydroxylation reaction tower (2) both include a liquid level monitoring system, specifically: A liquid level online detector (14) is provided on the side wall of the hydroxylation reaction tower (1) located in the bottom liquid of the tower, and a program-controlled valve (40) is provided on the outlet pipe of the extraction pump (41) of the second tower. The liquid level online detector (14) is associated with the program-controlled valve (40); A second liquid level online detector (39) is provided on the side wall of the second hydroxylation reaction tower (2) located in the bottom liquid of the tower, and a program-controlled valve (51) is provided on the formaldehyde solution delivery pipeline. The second liquid level online detector (39) is associated with the program-controlled valve (51).

5. The device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid according to claim 1, characterized in that: The hydroxylation reaction tower (1) includes a production system, specifically: An analytical online detector (13) is provided on the side wall of the hydroxylation reaction tower (1) located in the tower bottom liquid, and a tower bottom extraction pump (19) and a program-controlled valve (20) are sequentially provided on the extraction pipeline of the finished liquid extraction outlet (15), and the analytical online detector (13) is associated with the program-controlled valve (20).

6. The device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid according to claim 1, characterized in that: The structured packing is composed of two pieces stacked up and down, and adopts 350Y corrugated packing.

7. A method for generating hydroxyacetonitrile by reacting gas-phase hydrocyanic acid, characterized in that: The device for generating hydroxyacetonitrile by reacting gaseous hydrocyanic acid as claimed in claim 1 comprises the following steps: Step 1: transporting gaseous hydrogen cyanide with a volume percentage of not less than 75% from the gaseous hydrogen cyanide inlet (11) into the first hydroxylation reaction tower (1), and simultaneously transporting a formaldehyde solution with a mass percentage of 37-55% into the spray plate of the second hydroxylation reaction tower (2), wherein the formaldehyde solution is mixed with sodium glycolate, and the mass ratio of sodium glycolate to formaldehyde is (0.1-0.5):100; Step 2, starting the second tower extraction pump (41), and transporting the bottom liquid of the hydroxylation reaction second tower (2) from the second tower extraction outlet (42) to the spray plate of the hydroxylation reaction first tower (1), after the bottom liquid of the hydroxylation reaction second tower (2) is evenly dispersed through the spray plate and the water distributor, it is countercurrently contacted with the gaseous hydrogen cyanide transferred upward on the surface of the structured packing to cause a hydroxylation reaction, and the generated hydroxyacetonitrile is extracted through the finished liquid extraction outlet (15); The unreacted gaseous hydrogen cyanide in the hydroxylation reaction tower (1) enters the inlet (37) of the second tower after passing through the mesh demister, and is transferred upward in the hydroxylation reaction tower (2). It is countercurrently contacted with the formaldehyde solution dispersed by the spray plate and water distributor of the hydroxylation reaction tower (2) on the surface of the structured packing to cause a hydroxylation reaction. The generated hydroxyacetonitrile and unreacted formaldehyde form the bottom liquid, and the non-condensable gas after the reaction is discharged from the cyanide-containing non-condensable gas outlet (29).

8. The method for producing hydroxyacetonitrile by reacting gaseous hydrocyanic acid according to claim 7, wherein: The first hydroxylation reaction tower (1) and the second hydroxylation reaction tower (2) both include a cooling circulation system and a temperature monitoring system, specifically: A tower kettle circulation outlet (16) is provided at the bottom of the hydroxylation reaction tower (1), and the tower kettle circulation outlet (16) is connected to a tower circulation pump (21) and a tower cooler (24) in sequence through a pipeline, and is finally connected to the spray plate inlet of the hydroxylation reaction tower (1); a temperature online detector (12) is provided on the side wall of the hydroxylation reaction tower (1) below the structured packing, and a program-controlled valve (23) is provided on the outlet pipe of the tower circulation pump (21), and the temperature online detector (12) is associated with the program-controlled valve (23); A second tower kettle circulation outlet (44) is provided at the bottom of the second hydroxylation reaction tower (2), and the second tower kettle circulation outlet (44) is connected to the second tower circulation pump (46) and the second tower cooler (49) in sequence through a pipeline, and is finally connected to the spray plate inlet of the second hydroxylation reaction tower (2); a second temperature online detector (38) is provided on the side wall of the second hydroxylation reaction tower (2) below the structured packing, and a program-controlled valve (48) is provided on the outlet pipe of the second tower circulation pump (46), and the second temperature online detector (38) is associated with the program-controlled valve (48); In step 2, the cooling circulation system is started at the same time, specifically: Start the first tower circulation pump (21) and the second tower circulation pump (46), A tower circulation pump (21) extracts the tower bottom liquid from the tower bottom circulation outlet (16) of the tower and transports it to the tower cooler (24) for heat exchange with cooling water to reduce the temperature; a temperature online detector (12) monitors the temperature of the tower bottom liquid in the hydroxylation reaction tower (1) in real time. When it is detected that the tower bottom liquid temperature exceeds 10-30°C, the program-controlled valve (23) opens, thereby increasing the cooling water entering the tower cooler (24); The second tower circulation pump (46) extracts the bottom liquid from the second tower bottom circulation outlet (44) and transports it to the second tower cooler (49) for heat exchange with cooling water for cooling; the second online temperature detector (38) monitors the temperature of the bottom liquid in the second hydroxylation reaction tower (2) in real time. When it is detected that the bottom liquid temperature exceeds 10-30°C, the programmable valve four (48) opens, thereby increasing the cooling water entering the second tower cooler (49).

9. The method for producing hydroxyacetonitrile by reacting gaseous hydrocyanic acid according to claim 7, wherein: The first hydroxylation reaction tower (1) and the second hydroxylation reaction tower (2) both include a liquid level monitoring system. The first hydroxylation reaction tower (1) also includes a production system, specifically: A liquid level online detector (14) and an analytical online detector (13) are provided on the side wall of the first hydroxylation reaction tower (1) below the structured packing, a program-controlled valve (40) is provided on the outlet pipe of the second tower production pump (41), and the liquid level online detector (14) is associated with the program-controlled valve (40); a tower reactor production pump (19) and a program-controlled valve (20) are provided in sequence on the production pipe of the finished liquid production outlet (15), and the analytical online detector (13) is associated with the program-controlled valve (20); A second liquid level online detector (39) is provided on the side wall of the second hydroxylation reaction tower (2) below the structured packing, and a program-controlled valve (51) is provided on the formaldehyde solution delivery pipeline. The second liquid level online detector (39) is associated with the program-controlled valve (51); In step 2, the liquid level monitoring system and the extraction system are started simultaneously, specifically: Start the first tower kettle extraction pump (19) and the second tower extraction pump (41), When the analytical online detector (13) detects that the formaldehyde content in the bottom liquid of the hydroxylation reaction tower (1) is less than 0.08% and the hydrocyanic acid content is less than or equal to 1%, the program-controlled valve (20) is opened to extract the bottom liquid; The liquid level online detector 1 (14) monitors the liquid level of the hydroxylation reaction tower 1 (1) in real time. When the liquid level is detected to be lower than a preset value, the program-controlled valve 3 (40) opens, thereby increasing the liquid delivery rate of the bottom of the hydroxylation reaction tower 2 (2); The second liquid level online detector (39) monitors the liquid level of the second hydroxylation reaction tower (2) in real time. When the liquid level is detected to be lower than the preset value, the program-controlled valve (51) opens, thereby increasing the flow rate of the formaldehyde solution entering the second hydroxylation reaction tower (2).

10. The method for producing hydroxyacetonitrile by reacting gaseous hydrocyanic acid according to claim 7, characterized in that: A pressure regulating device is installed at the cyanide-containing non-condensable gas outlet (29), and the pressure in the hydroxylation reaction tower 1 (1) and the hydroxylation reaction tower 2 (2) is controlled by the pressure regulating device to maintain the pressure at -0.02-0.02 MPa.

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