A system for preparing oligoesters from nitrogen-containing oligomers in acrylonitrile waste liquor and co-producing ammonium phosphate and a method of using the same

Abstract

This invention relates to a system and method for preparing low-polymers and co-producing ammonium phosphate from nitrogen-containing oligomers in acrylonitrile wastewater. The invention aims to address the technical problems of high cost and environmental pollution associated with treating nitrogen-containing organic wastewater generated in acrylonitrile production through combustion. The system comprises a premixing tank, a raw material preheater, a reaction vessel, a neutralization tank, an oil-water separator, an extraction tower, an alcohol recovery tower, and a water recovery tower. This invention provides a method for converting wastewater containing nitrogen-containing oligomers generated in acrylonitrile plants into low-polymers, which can be used as a green fuel, by fully utilizing the oligomeric carbon chains. Simultaneously, nitrogen is removed, and ammonium salts are co-produced, which can be sold as fertilizer raw materials, thereby reducing costs. This invention provides a novel process for utilizing nitrogen-containing organic wastewater, improving the utilization rate of carbon and nitrogen resources.

Description

Technical Field

[0001] This invention relates to a system for treating nitrogen-containing oligomers in acrylonitrile wastewater and its method of use. Background Technology

[0002] Acrylonitrile is one of the important monomers in the three major polymer synthetic materials (plastics, synthetic rubber, and synthetic fibers), used in the production of polyacrylonitrile fibers, ABS resin, etc. my country is the world's largest producer and consumer of acrylonitrile, consistently ranking first in production volume, and its production capacity is increasing year by year. Currently, the most widely used acrylonitrile production process globally is the propylene ammoxidation process (the Sohio process proposed in 1960), which uses propylene, ammonia, and air as raw materials to produce acrylonitrile. This process generates a large amount of acrylonitrile wastewater containing organic oligomers (some of which also contain ammonium sulfate). Acrylonitrile wastewater includes two main categories: quench tower bottom liquid and fourth-effect solvent residue. The fourth-effect evaporator residue is the evaporation residue produced during the treatment of the distillation recovery column in the acrylonitrile production process. The quench tower residue, depending on the type of quench tower (two-stage and one-stage), consists of three types of waste liquid: the upper stage quench tower residue (upper stage residue) of a two-stage quench tower, the lower stage quench tower residue (lower stage residue) of a two-stage quench tower, and the single-stage quench tower residue (single-stage residue). Early acrylonitrile production lines in my country mostly used two-stage quench towers, while newly built or renovated lines in recent years mostly use single-stage quench towers. Some acrylonitrile companies use both types of quench towers, but single-stage quench towers are gradually replacing two-stage quench towers. The residual liquid from the fourth-effect transistor contains a high concentration of organic oligomers, while the bottom liquid from the quench tower contains both organic oligomers and ammonium sulfate. Specifically, the upper section bottom liquid has a lower concentration of organic oligomers but a higher concentration of ammonium sulfate; the lower section bottom liquid has a higher concentration of organic oligomers but a lower concentration of ammonium sulfate; and the first section bottom liquid has relatively high concentrations of both organic oligomers and ammonium sulfate. The organic oligomers contained in these acrylonitrile waste liquids (residual liquid from the fourth-effect transistor and bottom liquid from the quench tower) are often referred to as heavy components and are nitrogen-containing (organic nitrogen) oligomers.

[0003] The treatment methods for the residual liquid from the fourth-effect transistor vary among acrylonitrile companies. Most acrylonitrile companies directly concentrate the residual liquid from the fourth-effect transistor and then incinerate it. A few acrylonitrile companies use the residual liquid from the fourth-effect transistor as quench water (quench tower inlet water) in the lower section of the quench tower and incinerate it in the form of quench tower bottom liquid. That is, the residual liquid from the fourth-effect transistor is ultimately treated by incineration (or pyrolysis to produce sulfuric acid).

[0004] The bottom liquid of the lower section and the bottom liquid of the first section of the quench tower have a high content of heavy components, which are currently treated by incineration (or pyrolysis to produce sulfuric acid, which can also be considered incineration). The bottom liquid of the upper section has a relatively low content of heavy components, which is currently treated by evaporation and crystallization of ammonium sulfate to produce solid ammonium sulfate fertilizer. However, this process also generates a concentrated waste liquid discharged from the crystallization system—ammonium sulfate polymer waste liquid. This waste liquid has a certain viscosity, and it is currently also treated by incineration. Acrylonitrile waste liquid can be extracted and separated to obtain nitrogen-containing oligomers. The separation method is an existing method, which can be seen in patents ZL201910744120.5, 202311223844.8, and 202311210096.X.

[0005] Because the waste liquid is composed of nitrogen-containing oligomers, and the organic nitrogen functional groups in the nitrogen-containing oligomers have flame-retardant properties, incineration consumes a lot of fuel, has low incineration efficiency, and high incineration costs.

[0006] In summary, while incineration is an effective method for treating acrylonitrile waste liquid (residue from the fourth-effect electrolytic capacitor and bottom liquid from the quench tower), it has significant shortcomings. Incineration is energy-intensive, costly, and generates large amounts of waste gas. The investment in incineration equipment and subsequent flue gas treatment equipment is substantial, and the cost of flue gas desulfurization and denitrification is high. Therefore, how to treat acrylonitrile waste liquid, especially how to achieve the resource utilization of nitrogen-containing oligomers from a combustion perspective, has become a pressing problem that needs to be solved in the resource utilization of acrylonitrile waste liquid. Summary of the Invention

[0007] The present invention aims to solve the technical problems of high cost and environmental pollution in the current treatment of nitrogen-containing organic waste liquid in acrylonitrile waste liquid by incineration, and provides a system and method for preparing low polyester and producing ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid.

[0008] The system for preparing low-polyester and producing ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid according to the present invention consists of a premixed stirring tank 1, a raw material preheater 2, a reaction vessel 3, a separation tower 4, a steam drum 5, a neutralization tank 6, an ammonia recovery tower 7, an oil-water separation tank 8, an ammonium salt crystallization tower 9, an extraction tower 10, an alcohol recovery tower 11, a water recovery tower 12, and an alcohol recovery cooler 13.

[0009] The lower outlet of the premixing tank 1 is connected to the shell-side inlet of the raw material preheater 2, and the shell-side outlet of the raw material preheater 2 is connected to the feed port at the top of the reactor 3; the tube-side inlet of the raw material preheater 2 is connected to the top of the reaction chamber in the reactor 3, and the tube-side outlet of the raw material preheater 2 is connected to the feed port of the separation tower 4; the top outlet of the separation tower 4 is connected to the top feed port of the reactor 3, and the bottom outlet of the separation tower 4 is connected to the waste liquid recovery system.

[0010] The lower material outlet of the reactor 3 is connected to the upper material inlet of the neutralization tank 6; the outer wall of the reactor 3 is provided with a heat insulation sleeve, the upper inlet of the heat insulation sleeve is connected to high-pressure steam, and the lower outlet of the heat insulation sleeve is connected to the inlet of the steam drum 5; the top of the steam drum 5 is provided with a safety pressure relief valve.

[0011] The upper material inlet of the neutralization tank 6 is also connected to a mixed ammonia water pipeline 7-1. An ammonia gas vent is provided at the upper part of the neutralization tank 6, which is connected to the middle part of the ammonia recovery tower 7. The bottom material outlet of the neutralization tank 6 is connected to the feed inlet of the oil-water separator 8. The outer wall of the neutralization tank 6 is provided with a heat insulation sleeve. The lower inlet of the heat insulation sleeve is connected to the lower outlet of the steam drum 5, and the upper outlet of the heat insulation sleeve is connected to the cooling water recovery pipe.

[0012] The top inlet of the ammonia recovery tower 7 is connected to deionized water, and the lower outlet of the ammonia recovery tower 7 is connected in parallel with the new ammonia water pipeline to form a mixed ammonia water pipeline 7-1.

[0013] The upper material outlet of the oil-water separator 8 is connected to the lower feed inlet of the extraction tower 10, and the lower material outlet of the oil-water separator 8 is connected to the material inlet of the ammonium salt crystallization tower 9. The lower outlet of the ammonium salt crystallization tower 9 yields the recycled ammonium salt product; a safety valve is provided at the top of the oil-water separator 8.

[0014] The upper material inlet of the extraction tower 10 is connected to deionized water, the top material outlet of the extraction tower 10 is connected to the material inlet of the alcohol recovery tower 11, and the bottom outlet of the extraction tower 10 is connected to the waste liquid recovery tower.

[0015] The upper material outlet of the alcohol recovery tower 11 is connected to the tube inlet of the alcohol recovery cooler 13, and the lower material outlet of the alcohol recovery tower 11 is connected to the material inlet of the water recovery tower 12; the tube outlet of the alcohol recovery cooler 13 receives recovered alcohol, and the shell inlet and outlet of the alcohol recovery cooler 13 are both connected to cooling water.

[0016] The upper material outlet of the water recovery tower 12 is connected to the waste liquid recovery, and the lower material outlet of the water recovery tower 12 outputs low polyester compounds.

[0017] The method of using the system of the present invention, which uses nitrogen-containing oligomers in acrylonitrile waste liquid as raw materials to prepare low-polyester and co-produce ammonium phosphate, is as follows:

[0018] 1. The nitrogen-containing organic liquid to be treated and alcohols are fed into a premixing tank 1, strong acid is added to adjust the pH to below 2, and after being mixed evenly, it is sent to the raw material preheater 2, and then sent to the reaction chamber of the reaction vessel 3.

[0019] The mass ratio of the alcohols to the nitrogen-containing organic matter in the nitrogen-containing organic liquid is (1-4):1;

[0020] 2. The reaction chamber of reactor 3 is heated to 120℃~140℃ by high-pressure steam from the outside and kept at this temperature for 6h~7h. At the same time, strong acid is also introduced into the reaction chamber to control the pH below 2. The upper steam outlet of the reaction chamber is connected to the tube inlet of the raw material preheater 2 to preheat the raw material. After the tube is cooled by heat exchange (mainly alcohol and water), it is introduced into the separation tower 4. The upper layer of the separation tower 4, which contains alcohol, flows back into the reaction chamber of reactor 3. The lower layer of the separation tower 4, which contains heavy components, is connected to the waste liquid recovery. High-pressure steam flows through the outer insulation jacket of reactor 3 and is connected to the steam drum 5 for gas-liquid separation. The cooled hot water in the steam drum 5 is introduced into the shell side of the outer insulation jacket of the neutralization tank 6 to heat the neutralization tank 6. The shell side water is output and connected to the cooling water recovery.

[0021] 3. The mixture after reaction in the reaction chamber of reactor 3 is introduced into neutralization tank 6 for neutralization. Ammonia water is added to neutralization tank 6 to adjust the pH to 7-8. The temperature in neutralization tank 6 is set to 40℃-70℃. The gas outlet at the top of the reaction chamber of neutralization tank 6 is connected to ammonia recovery tower 7. The ammonia gas that escapes is recovered by spraying deionized water into ammonia recovery tower 7. The recovered ammonia water is mixed with fresh ammonia water and then introduced into neutralization tank 6 through mixed ammonia water pipeline 7-1.

[0022] 4. The mixture after neutralization in neutralization tank 6 is fed into oil-water separator 8 to separate the ester layer and water layer. The upper ester layer is fed into extraction tower 10, where deionized water is introduced for washing. The ester layer is fed from the bottom of extraction tower 10, and the washing water is fed from the top for countercurrent extraction. The washing liquid at the bottom of extraction tower 10 is sent to waste liquid recovery. After extraction, the ester layer is transported through pipeline to alcohol recovery tower 11. The heavy components at the bottom of alcohol recovery tower 11 are then transported to water recovery tower 12. The alcohol recovered at the top of alcohol recovery tower 11 is mixed with new alcohol after passing through the tube side of alcohol recovery cooler 13 and fed back into premixed stirring tank 1 as a reaction feedstock. Cooling water is used as a cold fluid in the shell side of alcohol recovery cooler 13 to cool the recovered alcohol. The water layer in the lower layer of oil-water separator 8 contains ammonium salt and is transported to ammonium salt crystallization tower 9. The lower outlet of ammonium salt crystallization tower 9 yields the regenerated ammonium salt product.

[0023] It should be noted here that if there is ammonium sulfate residue in the nitrogen-containing oligomer liquid obtained after the extraction and separation of acrylonitrile waste liquid, the residual ammonium sulfate will also be in the water layer in the lower layer of oil-water separator 8.

[0024] 5. The heavy components at the bottom of the water recovery tower 12 are the final product low polyester compounds, while the light components at the top of the water recovery tower 12 are directly discharged into the wastewater recovery system.

[0025] The shell side of a heat exchanger is the outer liquid passage through which cold fluid flows; the tube side is the inner liquid passage through which hot fluid flows. This is existing technology.

[0026] This invention provides a method and apparatus for converting a nitrogen-containing oligomer from acrylonitrile wastewater, containing a large amount of nitrogen-containing oligomeric carbon chains, into low-polyester compounds while simultaneously removing nitrogen and co-producing ammonium salts. This method solves the problems of high treatment costs, long treatment times, and the inability to recover organic carbon chains in acrylonitrile industry wastewater. It fully utilizes the oligomeric carbon chains to convert them into low-polyester compounds, the product of which can be used as a green fuel. The co-produced ammonium salts can also be sold as fertilizer raw materials, thereby reducing costs. This invention provides a novel process for the utilization of nitrogen-containing organic wastewater, improving the utilization rate of carbon and nitrogen resources.

[0027] The method of this invention can effectively utilize nitrogen-containing organic oligomers, thereby improving corporate economic benefits, increasing corporate market competitiveness, reducing environmental emissions, and achieving clean production. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a system for preparing low-polyester and producing ammonium phosphate using nitrogen-containing oligomers from acrylonitrile waste liquid as raw materials, according to specific implementation method one.

[0029] Figure 2 Fourier transform infrared (FTIR) data are obtained from the nitrogen-containing organic liquid to be treated described in step one of Experiment 2 and the low-polyester compound prepared in step five of Experiment 2. Detailed Implementation

[0030] Specific Implementation Method 1: This implementation method is a system for preparing low-polyester and co-producing ammonium phosphate using nitrogen-containing oligomers from acrylonitrile waste liquid as raw materials, such as... Figure 1 As shown, it specifically consists of a premixing tank 1, a raw material preheater 2, a reaction vessel 3, a separation tower 4, a steam drum 5, a neutralization tank 6, an ammonia recovery tower 7, an oil-water separation tank 8, an ammonium salt crystallization tower 9, an extraction tower 10, an alcohol recovery tower 11, a water recovery tower 12, and a recovered alcohol cooler 13.

[0031] The lower outlet of the premixing tank 1 is connected to the shell-side inlet of the raw material preheater 2, and the shell-side outlet of the raw material preheater 2 is connected to the feed port at the top of the reactor 3; the tube-side inlet of the raw material preheater 2 is connected to the top of the reaction chamber in the reactor 3, and the tube-side outlet of the raw material preheater 2 is connected to the feed port of the separation tower 4; the top outlet of the separation tower 4 is connected to the top feed port of the reactor 3, and the bottom outlet of the separation tower 4 is connected to the waste liquid recovery system.

[0032] The lower material outlet of the reactor 3 is connected to the upper material inlet of the neutralization tank 6; the outer wall of the reactor 3 is provided with a heat insulation sleeve, the upper inlet of the heat insulation sleeve is connected to high-pressure steam, and the lower outlet of the heat insulation sleeve is connected to the inlet of the steam drum 5; the top of the steam drum 5 is provided with a safety pressure relief valve.

[0033] The upper material inlet of the neutralization tank 6 is also connected to a mixed ammonia water pipeline 7-1. An ammonia gas vent is provided at the upper part of the neutralization tank 6, which is connected to the middle part of the ammonia recovery tower 7. The bottom material outlet of the neutralization tank 6 is connected to the feed inlet of the oil-water separator 8. The outer wall of the neutralization tank 6 is provided with a heat insulation sleeve. The lower inlet of the heat insulation sleeve is connected to the lower outlet of the steam drum 5, and the upper outlet of the heat insulation sleeve is connected to the cooling water recovery pipe.

[0034] The top inlet of the ammonia recovery tower 7 is connected to deionized water, and the lower outlet of the ammonia recovery tower 7 is connected in parallel with the new ammonia water pipeline to form a mixed ammonia water pipeline 7-1.

[0035] The upper material outlet of the oil-water separator 8 is connected to the lower feed inlet of the extraction tower 10, and the lower material outlet of the oil-water separator 8 is connected to the material inlet of the ammonium salt crystallization tower 9. The lower outlet of the ammonium salt crystallization tower 9 yields the recycled ammonium salt product; a safety valve is provided at the top of the oil-water separator 8.

[0036] The upper material inlet of the extraction tower 10 is connected to deionized water, the top material outlet of the extraction tower 10 is connected to the material inlet of the alcohol recovery tower 11, and the bottom outlet of the extraction tower 10 is connected to the waste liquid recovery tower.

[0037] The upper material outlet of the alcohol recovery tower 11 is connected to the tube inlet of the alcohol recovery cooler 13, and the lower material outlet of the alcohol recovery tower 11 is connected to the material inlet of the water recovery tower 12; the tube outlet of the alcohol recovery cooler 13 receives recovered alcohol, and the shell inlet and outlet of the alcohol recovery cooler 13 are both connected to cooling water.

[0038] The upper material outlet of the water recovery tower 12 is connected to the waste liquid recovery, and the lower material outlet of the water recovery tower 12 outputs low polyester compounds.

[0039] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the raw material preheater 2 is a heat exchanger. Everything else is the same as in Specific Implementation Method One.

[0040] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the recovered alcohol cooler 13 is a heat exchanger. Everything else is the same as in Specific Implementation Method 1 or 2.

[0041] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that a pH probe is installed in the premixing tank 1. Otherwise, it is the same as Specific Implementation Methods One to Three.

[0042] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that a pH probe and a temperature probe are installed in the reaction vessel 3. Everything else is the same as in Specific Implementation Method Four.

[0043] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that a pH probe and a temperature probe are installed in the neutralization tank 6. Everything else is the same as in Specific Implementation Method Five.

[0044] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Method Six in that the separation tower 4 is a storage tank. Everything else is the same as in Specific Implementation Method Six.

[0045] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Method Seven in that the separation tower 4 is a distillation tower. Everything else is the same as in Specific Implementation Method Seven.

[0046] Specific Implementation Method Nine: This implementation method, along with Specific Implementation Method One, describes the system for preparing low-polyester and co-producing ammonium phosphate using nitrogen-containing oligomers from acrylonitrile waste liquid as raw materials. The specific process is as follows:

[0047] 1. The nitrogen-containing organic liquid to be treated and alcohols are fed into a premixing tank 1, strong acid is added to adjust the pH to below 2, and after being mixed evenly, it is sent to the raw material preheater 2, and then sent to the reaction chamber of the reaction vessel 3.

[0048] The mass ratio of the alcohols to the nitrogen-containing organic matter in the nitrogen-containing organic liquid is (1-4):1;

[0049] 2. The reaction chamber of reactor 3 is heated to 120℃~140℃ by high-pressure steam from the outside and kept at this temperature for 6h~7h. At the same time, strong acid is also introduced into the reaction chamber to control the pH below 2. The upper steam outlet of the reaction chamber is connected to the tube inlet of the raw material preheater 2 to preheat the raw material. After the tube is cooled by heat exchange, it is introduced into the separation tower 4. The upper layer of the separation tower 4, which contains alcohols, flows back into the reaction chamber of reactor 3. The lower layer of the separation tower 4, which contains heavy components, is connected to the waste liquid recovery. High-pressure steam flows through the outer insulation jacket of reactor 3 and is connected to the steam drum 5 for gas-liquid separation. The cooled hot water in the steam drum 5 is introduced into the shell side of the outer insulation jacket of the neutralization tank 6 to heat the neutralization tank 6. The shell side water is output and connected to the cooling water recovery.

[0050] 3. The mixture after reaction in the reaction chamber of reactor 3 is introduced into neutralization tank 6 for neutralization. Ammonia water is added to neutralization tank 6 to adjust the pH to 7-8. The temperature in neutralization tank 6 is set to 40℃-70℃. The gas outlet at the top of the reaction chamber of neutralization tank 6 is connected to ammonia recovery tower 7. The ammonia gas that escapes is recovered by spraying deionized water into ammonia recovery tower 7. The recovered ammonia water is mixed with fresh ammonia water and then introduced into neutralization tank 6 through mixed ammonia water pipeline 7-1.

[0051] 4. The mixture after neutralization in neutralization tank 6 is fed into oil-water separator 8 to separate the ester layer and water layer. The upper ester layer is fed into extraction tower 10, where deionized water is introduced for washing. The ester layer is fed from the bottom of extraction tower 10, and the washing water is fed from the top for countercurrent extraction. The washing liquid at the bottom of extraction tower 10 is sent to waste liquid recovery. After extraction, the ester layer is transported through pipeline to alcohol recovery tower 11. The heavy components at the bottom of alcohol recovery tower 11 are then transported to water recovery tower 12. The alcohol recovered at the top of alcohol recovery tower 11 is mixed with new alcohol after passing through the tube side of alcohol recovery cooler 13 and fed back into premixed stirring tank 1 as a reaction feedstock. Cooling water is used as a cold fluid in the shell side of alcohol recovery cooler 13 to cool the recovered alcohol. The water layer in the lower layer of oil-water separator 8 contains ammonium salt and is transported to ammonium salt crystallization tower 9. The lower outlet of ammonium salt crystallization tower 9 yields the regenerated ammonium salt product.

[0052] 5. The heavy components at the bottom of the water recovery tower 12 are the final product low polyester compounds, while the light components at the top of the water recovery tower 12 are directly discharged into the wastewater recovery system.

[0053] The invention was verified using the following experiments:

[0054] Experiment 1: This experiment is a system for preparing low-polyester co-production of ammonium phosphate using nitrogen-containing oligomers from acrylonitrile waste liquid as raw materials. Figure 1 As shown, it specifically consists of a premixing tank 1, a raw material preheater 2, a reaction vessel 3, a separation tower 4, a steam drum 5, a neutralization tank 6, an ammonia recovery tower 7, an oil-water separation tank 8, an ammonium salt crystallization tower 9, an extraction tower 10, an alcohol recovery tower 11, a water recovery tower 12, and a recovered alcohol cooler 13.

[0055] The raw material preheater 2 is a heat exchanger; the recovered alcohol cooler 13 is a heat exchanger; a pH probe is installed in the premixing tank 1; a pH probe and a temperature probe are installed in the reaction vessel 3; a pH probe and a temperature probe are installed in the neutralization tank 6.

[0056] The lower outlet of the premixing tank 1 is connected to the shell-side inlet of the raw material preheater 2, and the shell-side outlet of the raw material preheater 2 is connected to the feed port at the top of the reactor 3; the tube-side inlet of the raw material preheater 2 is connected to the top of the reaction chamber in the reactor 3, and the tube-side outlet of the raw material preheater 2 is connected to the feed port of the separation tower 4; the top outlet of the separation tower 4 is connected to the top feed port of the reactor 3, and the bottom outlet of the separation tower 4 is connected to the waste liquid recovery system.

[0057] The lower material outlet of the reactor 3 is connected to the upper material inlet of the neutralization tank 6; the outer wall of the reactor 3 is provided with a heat insulation sleeve, the upper inlet of the heat insulation sleeve is connected to high-pressure steam, and the lower outlet of the heat insulation sleeve is connected to the inlet of the steam drum 5; the top of the steam drum 5 is provided with a safety pressure relief valve.

[0058] The upper material inlet of the neutralization tank 6 is also connected to a mixed ammonia water pipeline 7-1. An ammonia gas vent is provided at the upper part of the neutralization tank 6, which is connected to the middle part of the ammonia recovery tower 7. The bottom material outlet of the neutralization tank 6 is connected to the feed inlet of the oil-water separator 8. The outer wall of the neutralization tank 6 is provided with a heat insulation sleeve. The lower inlet of the heat insulation sleeve is connected to the lower outlet of the steam drum 5, and the upper outlet of the heat insulation sleeve is connected to the cooling water recovery pipe.

[0059] The top inlet of the ammonia recovery tower 7 is connected to deionized water, and the lower outlet of the ammonia recovery tower 7 is connected in parallel with the new ammonia water pipeline to form a mixed ammonia water pipeline 7-1.

[0060] The upper material outlet of the oil-water separator 8 is connected to the lower feed inlet of the extraction tower 10, and the lower material outlet of the oil-water separator 8 is connected to the material inlet of the ammonium salt crystallization tower 9. The lower outlet of the ammonium salt crystallization tower 9 yields the recycled ammonium salt product; a safety valve is provided at the top of the oil-water separator 8.

[0061] The upper material inlet of the extraction tower 10 is connected to deionized water, the top material outlet of the extraction tower 10 is connected to the material inlet of the alcohol recovery tower 11, and the bottom outlet of the extraction tower 10 is connected to the waste liquid recovery tower.

[0062] The upper material outlet of the alcohol recovery tower 11 is connected to the tube inlet of the alcohol recovery cooler 13, and the lower material outlet of the alcohol recovery tower 11 is connected to the material inlet of the water recovery tower 12; the tube outlet of the alcohol recovery cooler 13 receives recovered alcohol, and the shell inlet and outlet of the alcohol recovery cooler 13 are both connected to cooling water.

[0063] The upper material outlet of the water recovery tower 12 is connected to the waste liquid recovery, and the lower material outlet of the water recovery tower 12 outputs low polyester compounds.

[0064] Experiment 2: The method of using the apparatus in Experiment 1 to prepare low-polyester and co-produce ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid is as follows:

[0065] 1. The nitrogen-containing organic liquid to be treated and butanol are fed into the premixing tank 1, concentrated phosphoric acid is added to adjust the pH to 1.5, and after being mixed evenly, it is sent to the raw material preheater 2, and then sent to the reaction chamber of the reaction vessel 3.

[0066] The mass fraction of nitrogen-containing organic matter in the nitrogen-containing organic liquid is 48%;

[0067] The mass ratio of butanol to nitrogen-containing organic matter in the nitrogen-containing organic liquid is 2:1;

[0068] 2. The reaction chamber of reactor 3 is heated to 140°C by high-pressure steam from the outside and kept at that temperature for 6 hours. At the same time, strong acid is introduced into the reaction chamber to control the pH to 1.5. The upper steam outlet of the reaction chamber is connected to the tube inlet of the raw material preheater 2 to preheat the raw material. After the tube is cooled by heat exchange, it is introduced into the separation tower 4 (using a storage tank) for static stratification. The upper layer of the separation tower 4, which is alcohol, flows back into the reaction chamber of reactor 3, and the lower layer of the separation tower 4, which is heavy component, is connected to the waste liquid recovery. High-pressure steam flows through the outer insulation jacket of reactor 3 and is connected to the steam drum 5 for gas-liquid separation. The steam drum 5 is kept stable by a pressure relief valve. The cooled hot water in the steam drum 5 is introduced into the shell side of the outer insulation jacket of the neutralization tank 6 to heat the neutralization tank 6. The shell side water is output and connected to the cooling water recovery.

[0069] 3. The mixture after reaction in the reaction chamber of reactor 3 is introduced into neutralization tank 6 for neutralization. Ammonia water is added to neutralization tank 6 to adjust the pH to 7. The temperature in neutralization tank 6 is set to 70℃. The gas outlet at the top of the reaction chamber of neutralization tank 6 is connected to ammonia recovery tower 7. The ammonia gas that escapes is recovered by spraying deionized water into ammonia recovery tower 7. The recovered ammonia water is mixed with fresh ammonia water and then introduced into neutralization tank 6 through mixed ammonia water pipeline 7-1.

[0070] 4. The mixture after neutralization in neutralization tank 6 is fed into oil-water separator 8 for settling to separate the ester layer and water layer. The upper ester layer is fed into extraction tower 10, where deionized water is circulated for washing. The ester layer is fed from the bottom of extraction tower 10, while the washing water is fed from the top for countercurrent extraction. The washing liquid at the bottom of extraction tower 10 is sent to waste liquid recovery. After extraction, the ester layer is transported through pipeline to alcohol recovery tower 11 (using a distillation tower). The heavy components at the bottom of alcohol recovery tower 11 are then transported to water recovery tower 12 (using a distillation tower). The alcohol recovered at the top of alcohol recovery tower 11 is mixed with new alcohol after passing through the tube side of alcohol recovery cooler 13 and fed back into premixed stirring tank 1 as a reaction feedstock. Cooling water is used as a cold fluid in the shell side of alcohol recovery cooler 13 to cool the recovered alcohol. The water layer in the lower layer of oil-water separator 8 contains ammonium salt and is transported to ammonium salt crystallization tower 9. Ammonium phosphate is obtained from the lower outlet of ammonium salt crystallization tower 9.

[0071] 5. The heavy components at the bottom of the water recovery tower 12 are the final product low polyester compounds, while the light components at the top of the water recovery tower 12 are directly discharged into the wastewater recovery system.

[0072] In step four, the ammonium salt content in the product at the top of extraction tower 10 is less than 1 g / kg.

[0073] In step four, the alcohol content in the heavy component of the product at the bottom of alcohol recovery tower 11 is less than 1 g / kg.

[0074] The water content in the low-polyester compound obtained in step five is less than 1 g / kg.

[0075] Experiment 3: The method of using the apparatus in Experiment 1 to prepare low-polyester and co-produce ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid is as follows:

[0076] 1. The nitrogen-containing organic liquid to be treated and methanol are fed into the premixing tank 1, concentrated sulfuric acid is added to adjust the pH to 1.5, and after being mixed evenly, it is sent to the raw material preheater 2, and then sent to the reaction chamber of the reaction vessel 3.

[0077] The mass fraction of nitrogen-containing organic matter in the nitrogen-containing organic liquid is 64%.

[0078] The mass ratio of methanol to nitrogen-containing organic matter in the liquid is 3:1;

[0079] 2. The reaction chamber of reactor 3 is heated to 120°C by high-pressure steam from the outside and kept at that temperature for 6 hours. At the same time, strong acid is introduced into the reaction chamber to control the pH to 1.5. The upper steam outlet of the reaction chamber is connected to the tube inlet of the raw material preheater 2 to preheat the raw material. After the tube is cooled by heat exchange, it is introduced into the separation tower 4. The separation tower 4 is a small distillation tower. After the feed is fed, it is distilled. The upper layer of the separation tower 4, which is alcohol, flows back into the reaction chamber of reactor 3. The lower layer of the separation tower 4, which is heavy component, is connected to the waste liquid recovery. High-pressure steam flows through the outer insulation jacket of reactor 3 and is connected to the steam drum 5 for gas-liquid separation. The steam drum 5 is kept stable by a pressure relief valve. The cooled hot water in the steam drum 5 is introduced into the shell side of the outer insulation jacket of the neutralization tank 6 to heat the neutralization tank 6. The shell side water is output and connected to the cooling water recovery.

[0080] 3. The mixture after reaction in the reaction chamber of reactor 3 is introduced into neutralization tank 6 for neutralization. Ammonia water is added to neutralization tank 6 to adjust the pH to 7. The temperature in neutralization tank 6 is set to 40℃. The gas outlet at the top of the reaction chamber of neutralization tank 6 is connected to ammonia recovery tower 7. The ammonia gas that escapes is recovered by spraying deionized water into ammonia recovery tower 7. The recovered ammonia water is mixed with fresh ammonia water and then introduced into neutralization tank 6 through mixed ammonia water pipeline 7-1.

[0081] 4. The mixture after neutralization in neutralization tank 6 is fed into oil-water separator 8 for settling to separate the ester layer and water layer. The upper ester layer is fed into extraction tower 10, where deionized water is circulated for washing. The ester layer is fed from the bottom of extraction tower 10, while the washing water is fed from the top for countercurrent extraction. The washing liquid at the bottom of extraction tower 10 is sent to waste liquid recovery. After extraction, the ester layer is transported through pipeline to alcohol recovery tower 11 (using a distillation tower). The heavy components at the bottom of alcohol recovery tower 11 are then transported to water recovery tower 12 (using a distillation tower). The alcohol recovered at the top of alcohol recovery tower 11 is mixed with new alcohol after passing through the tube side of alcohol recovery cooler 13 and fed back into premixed stirring tank 1 as a reaction feedstock. Cooling water is used as a cold fluid in the shell side of alcohol recovery cooler 13 to cool the recovered alcohol. The water layer in the lower layer of oil-water separator 8 contains ammonium salt and is transported to ammonium salt crystallization tower 9. Ammonium sulfate is obtained from the lower outlet of ammonium salt crystallization tower 9.

[0082] 5. The heavy components at the bottom of the water recovery tower 12 are the final product low polyester compounds, while the light components at the top of the water recovery tower 12 are directly discharged into the wastewater recovery system.

[0083] The calorific value of the low-polyester compounds prepared in step five of Experiments 2 and 3 is determined, and the results are shown in Table 1.

[0084] Table 1 Results of Calorific Value Determination

[0085]

[0086] Table 1 shows that the calorific value of the low-polyester compound prepared in step five of Experiment 2 is close to that of diesel oil in China (38–40 MJ / kg), and significantly higher than that of bituminous coal (22–32 MJ / kg) and biofuels (ethanol 23.5 MJ / kg, methanol 19.8 MJ / kg), indicating that it has a high energy density and may be suitable for industrial boilers or some fuel-fired equipment. The calorific value of the low-polyester compound prepared in step five of Experiment 3 is slightly higher than that of ethanol (23.5 MJ / kg), close to that of bituminous coal (22–32 MJ / kg), and similar to that of ethanol (23.5 MJ / kg), but significantly lower than that of diesel oil (38–40 MJ / kg) and gasoline (44–46 MJ / kg), making it suitable as a substitute for low-calorific-value fuels (such as some industrial coal or ethanol).

[0087] Fourier transform infrared spectroscopy was performed on the nitrogen-containing organic liquid to be treated described in step one of Experiment 2 and the low-polyester compound prepared in step five of Experiment 2, respectively. The results are as follows: Figure 2 As shown in the figure, the nitrogen-containing organic liquid at a wavelength of 2250 cm⁻¹... -1 A sharp peak appears at this position, indicating the presence of a carbon-nitrogen triple bond. However, the peak at this position disappears in the prepared low-polyesterified product, while a peak appears at 1735 cm⁻¹. -1The emergence of a new peak indicates that the cyano groups in the raw material were converted into ester groups after the treatment in Experiment 2.

Claims

1. A system for preparing low-polyester co-production of ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid, characterized in that... The system for preparing low-polyester and producing ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid consists of a premixed stirring tank (1), a raw material preheater (2), a reaction vessel (3), a separation tower (4), a steam drum (5), a neutralization tank (6), an ammonia recovery tower (7), an oil-water separation tank (8), an ammonium salt crystallization tower (9), an extraction tower (10), an alcohol recovery tower (11), a water recovery tower (12), and a recovered alcohol cooler (13). The premixed tank (1) is filled with a mixture of strong acid, alcohol and acrylonitrile waste liquid; the lower outlet of the premixed tank (1) is connected to the shell inlet of the raw material preheater (2), and the shell outlet of the raw material preheater (2) is connected to the feed port at the top of the reactor (3); the tube inlet of the raw material preheater (2) is connected to the top of the reaction chamber in the reactor (3), and the tube outlet of the raw material preheater (2) is connected to the feed port of the separation tower (4); the top outlet of the separation tower (4) is connected to the top feed port of the reactor (3), and the bottom outlet of the separation tower (4) is connected to the waste liquid recovery system. The lower material outlet of the reactor (3) is connected to the upper material inlet of the neutralization tank (6); the outer wall of the reactor (3) is provided with a heat insulation sleeve, the upper inlet of the heat insulation sleeve is connected to high-pressure steam, and the lower outlet of the heat insulation sleeve is connected to the inlet of the steam drum (5); the top of the steam drum (5) is provided with a safety pressure relief valve. The upper material inlet of the neutralization tank (6) is also connected to a mixed ammonia water pipeline (7-1). An ammonia gas vent is provided at the upper part of the neutralization tank (6), and the ammonia gas vent is connected to the middle part of the ammonia gas recovery tower (7). The bottom material outlet of the neutralization tank (6) is connected to the feed inlet of the oil-water separator (8). The outer wall of the neutralization tank (6) is provided with a heat insulation sleeve. The lower inlet of the heat insulation sleeve is connected to the lower outlet of the steam drum (5), and the upper outlet of the heat insulation sleeve is connected to the cooling water recovery pipe. The top inlet of the ammonia recovery tower (7) is connected to deionized water, and the lower outlet of the ammonia recovery tower (7) is connected to the new ammonia water pipeline to form a mixed ammonia water pipeline (7-1). The upper material outlet of the oil-water separator (8) is connected to the lower feed inlet of the extraction tower (10), and the lower material outlet of the oil-water separator (8) is connected to the material inlet of the ammonium salt crystallization tower (9). The lower outlet of the ammonium salt crystallization tower (9) yields recycled ammonium salt products. A safety valve is provided at the top of the oil-water separator (8). The upper material inlet of the extraction tower (10) is connected to deionized water, the top material outlet of the extraction tower (10) is connected to the material inlet of the alcohol recovery tower (11), and the bottom outlet of the extraction tower (10) is connected to the waste liquid recovery tower. The upper material outlet of the alcohol recovery tower (11) is connected to the tube inlet of the alcohol recovery cooler (13), and the lower material outlet of the alcohol recovery tower (11) is connected to the material inlet of the water recovery tower (12); the tube outlet of the alcohol recovery cooler (13) receives recovered alcohol, and the shell inlet and outlet of the alcohol recovery cooler (13) are both connected to cooling water. The upper material outlet of the water recovery tower (12) is connected to the waste liquid recovery, and the lower material outlet of the water recovery tower (12) outputs low polyester compounds.

2. The system for preparing low-polyester co-production of ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid according to claim 1, characterized in that... The raw material preheater (2) is a heat exchanger.

3. The system for preparing low-polyester co-production of ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid according to claim 1, characterized in that... The recovered alcohol cooler (13) is a heat exchanger.

4. The system for preparing low-polyester co-production of ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid according to claim 1, characterized in that... A pH probe is installed in the premixed mixing tank (1).

5. The system for preparing low-polyester co-production of ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid according to claim 1, characterized in that... A pH probe and a temperature probe are installed in the reactor (3).

6. The system for preparing low-polyester co-production of ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid according to claim 1, characterized in that... A pH probe and a temperature probe are installed in the neutralization tank (6).

7. The system for preparing low-polyester co-production of ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid according to claim 1, characterized in that... The separation tower (4) is a storage tank.

8. The system for preparing low-polyester co-production of ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid according to claim 1, characterized in that... The separation tower (4) is a distillation tower.

9. The method of using the system for preparing low-polyester and co-producing ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid as raw materials as described in claim 1, characterized in that... The method of using the system for preparing low-polyester and co-producing ammonium phosphate from nitrogen-containing oligomers in acrylonitrile waste liquid as raw materials is as follows:

1. The nitrogen-containing organic liquid to be treated and alcohols are fed into a premixed stirring tank (1), strong acid is added to adjust the pH to below 2, and after being mixed evenly, it is transported to the raw material preheater (2) and then to the reaction chamber of the reactor (3); The mass ratio of the alcohols to the nitrogen-containing organic matter in the nitrogen-containing organic liquid is (1~4):1; 2. The reaction chamber of the reactor (3) is heated to 120℃~140℃ by high-pressure steam on the outside and kept at that temperature for 6h~7h. At the same time, strong acid is also introduced into the reaction chamber to control the pH below 2. The upper steam outlet of the reaction chamber is connected to the tube inlet of the raw material preheater (2) to preheat the raw material. After the tube is cooled by heat exchange, it is introduced into the separation tower (4). The upper layer of the separation tower (4) is alcohol flowing back into the reaction chamber of the reactor (3). The lower layer of the separation tower (4) is heavy component connected to waste liquid recovery. High-pressure steam flows through the outer insulation jacket of the reactor (3) and is connected to the steam drum (5) for gas-liquid separation. The hot water in the steam drum (5) after cooling is introduced into the shell side of the outer insulation jacket of the neutralization tank (6) to heat the neutralization tank (6). The shell side water is output and connected to the cooling water recovery.

3. The mixture after reaction in the reaction chamber of the reaction vessel (3) is introduced into the neutralization tank (6) for neutralization. Ammonia water is added to the neutralization tank (6) to adjust the pH to 7~8. The temperature in the neutralization tank (6) is set to 40℃~70℃. The gas outlet at the top of the reaction chamber of the neutralization tank (6) is connected to the ammonia recovery tower (7). The ammonia gas that escapes is recovered by spraying deionized water into the ammonia recovery tower (7). The ammonia water obtained after recovery is mixed with the new ammonia water and then introduced into the neutralization tank (6) through the mixed ammonia water pipeline (7-1).

4. The mixture after neutralization in the neutralization tank (6) is fed into the oil-water separator (8) to separate the ester layer and the water layer. The upper ester layer is fed into the extraction tower (10), where deionized water is introduced for washing. The ester layer is fed from the bottom of the extraction tower (10), and the washing water is fed from the top for countercurrent extraction. The washing liquid at the bottom of the extraction tower (10) is sent to the waste liquid recovery station. After extraction, the ester layer is transported through a pipeline to the alcohol recovery tower (11). The bottom of the alcohol recovery tower (11) is... The partially recombined components are then transported to the water recovery tower (12); the alcohol recovered at the top of the alcohol recovery tower (11) is mixed with new alcohol after passing through the tube side of the alcohol recovery cooler (13) and is then fed back into the premixed stirring tank (1) as a reaction raw material; cooling water is used as a cold fluid in the shell side of the alcohol recovery cooler (13) to cool the recovered alcohol; the water layer in the lower layer of the oil-water separator (8) contains ammonium salts and is transported to the ammonium salt crystallization tower (9), and the lower outlet of the ammonium salt crystallization tower (9) yields the recycled ammonium salt product; 5. The heavy components at the bottom of the water recovery tower (12) are the final product low polyester compounds, while the light components at the top of the water recovery tower (12) are directly discharged into the wastewater recovery system.

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