Hydroxyacetonitrile production method and production system based on carbon fiber off-gas

Abstract

The present invention relates to a hydroxyacetonitrile production method and production system based on a carbon fiber off-gas. The carbon fiber off-gas comprises a carbonization off-gas. The hydroxyacetonitrile production method comprises the following steps: subjecting the carbonization off-gas to de-tarring treatment and de-ammoniation treatment to obtain a treated off-gas; and performing a nucleophilic addition reaction between the treated off-gas and formaldehyde in the presence of a catalyst to obtain the hydroxyacetonitrile. By subjecting the carbonization off-gas to de-tarring treatment and de-ammoniation treatment and performing a nucleophilic addition reaction between the treated off-gas and formaldehyde in the presence of the catalyst to obtain the hydroxyacetonitrile, the present invention can significantly reduce the contents of hydrogen cyanide and ammonia gas in the off-gas, and the treated off-gas can meet emission standards. In addition, using the carbon fiber off-gas as a starting material to produce hydroxyacetonitrile can also be achieved, thereby leading to improved resource utilization rate and economic benefits.

Description

A method and system for producing hydroxyacetonitrile based on carbon fiber exhaust gas Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method and system for producing hydroxyacetonitrile based on carbon fiber tail gas. Background Technology

[0002] Carbon fiber refers to fibrous carbon compounds in which carbon elements account for more than 90% of the total mass. It is a material produced from organic raw materials such as polyacrylonitrile, pitch, and viscose fiber through processes such as oxidation and carbonization. It has a relatively low specific gravity (less than 1 / 4 that of steel), high tensile strength (7-9 times that of steel), and a high tensile modulus of elasticity (230-240 GPa). It is a structural material with high temperature resistance, corrosion resistance, low coefficient of thermal expansion, good dimensional stability, high specific strength, and high specific modulus, and is widely used in aerospace, sports, industry, transportation, construction, and many other fields.

[0003] Based on different raw materials, carbon fibers can be classified into polyacrylonitrile (PAN)-based carbon fibers, pitch-based carbon fibers, cellulose-based carbon fibers, phenolic-based carbon fibers, polyethylene-based carbon fibers, rayon-based carbon fibers, and polyamide-based carbon fibers. Among them, carbon fibers prepared from polyacrylonitrile-based precursor fibers and rayon precursor fibers exhibit superior performance. Polyacrylonitrile-based precursor fibers, in particular, possess high molecular orientation, high crystallinity, low cyclization activation energy, high melting point, and high carbon fiber yield. When polyacrylonitrile-based precursor fibers are heat-treated at low temperatures, a highly oriented molecular structure with excellent thermal stability can be formed. This thermally stable structure is not severely damaged during carbonization, resulting in carbon fibers with excellent mechanical properties. Clearly, polyacrylonitrile-based carbon fibers have superior performance, thus accounting for over 90% of total carbon fiber production and representing a current research hotspot.

[0004] The production process of polyacrylonitrile-based carbon fiber mainly includes polymerization of the spinning solution, preparation of precursor fibers, oxidation, and carbonization. During oxidation (carried out at approximately 180-300℃), cyclization degradation, dehydrogenation, and oxidation reactions mainly occur, causing the fiber color to change from white to yellow, then brown, and finally black. The carbonization process includes low-temperature carbonization (carried out at approximately 300-600℃) and high-temperature carbonization (carried out at approximately 900-1600℃), carried out under a protective gas atmosphere (such as nitrogen or inert gases). During carbonization, non-carbon elements such as nitrogen, hydrogen, and oxygen react and are released, producing gases such as hydrogen cyanide and ammonia.

[0005] In related technologies, combustion is commonly used to treat the exhaust gases generated during the carbonization process. However, this method is not very effective in treating exhaust gases, and the treated gases still fail to meet emission standards, causing environmental pollution and wasting resources to some extent. Summary of the Invention

[0006] In view of this, the present invention provides a carbonization tail gas deammoniation system and a carbon fiber production system to solve the problems of the commonly used combustion emission method for treating the tail gas generated in the carbonization process. This method has poor treatment effect on the tail gas, and the treated tail gas still cannot meet the emission standards, which still causes environmental pollution problems and, to a certain extent, wastes resources.

[0007] To achieve the above solution, the technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for producing hydroxyacetonitrile based on carbon fiber tail gas, wherein the carbon fiber tail gas includes carbonization tail gas, and the method for producing hydroxyacetonitrile includes the following steps:

[0009] The carbonized tail gas is subjected to tar removal and ammonia removal treatment to obtain treated tail gas;

[0010] After treatment, the exhaust gas undergoes a nucleophilic addition reaction with formaldehyde in the presence of a catalyst to yield hydroxyacetonitrile.

[0011] Optionally, the temperature of the nucleophilic addition reaction is 0-40℃, preferably 10-40℃; the duration of the nucleophilic addition reaction is 1-6h, preferably 1.5-6h.

[0012] Optionally, the catalyst is selected from at least one of cyanates, alkali metal hydroxides, and alkali metal sulfites.

[0013] In this application, cyanates may include substances such as sodium cyanide, potassium cyanide, cesium cyanide, and rubidium cyanide; alkali metal hydroxides may include substances such as sodium hydroxide, potassium hydroxide, cesium hydroxide, and rubidium hydroxide; and alkali metal sulfites may include substances such as sodium sulfite and sodium bisulfite.

[0014] Optionally, the molar ratio of the catalyst to formaldehyde is 0.001-0.015:1.0-1.5, preferably 0.003-0.015:1.0-1.5.

[0015] Optionally, after the nucleophilic addition reaction, the process further includes: performing gas-liquid separation on the system after the nucleophilic addition reaction, and mixing the separated gas with the first solvent.

[0016] Optionally, the first solvent is selected from at least one of alcohols, esters, aldehydes, benzene compounds, and water.

[0017] In this application, alcohols may include substances such as ethanol and glycerol, ethers may include substances such as diethyl ether, aldehydes may include substances such as formaldehyde, and benzene compounds may include substances such as benzene, toluene, and xylene.

[0018] Optionally, after mixing and separating the gas and the first solvent, the process further includes incinerating the remaining gas after mixing.

[0019] Optionally, the tar removal process includes:

[0020] A mixed gaseous cooling medium is used to exchange heat with carbonized tail gas to obtain crude tar.

[0021] The crude tar is subjected to gas-liquid separation, and the separated gas is mixed with a second solvent to absorb the tar in the gas.

[0022] Optionally, the deammoniation treatment includes:

[0023] The exhaust gas after tar removal is mixed with a deammonigenin to remove ammonia from the exhaust gas.

[0024] Optionally, the second solvent is selected from aromatic hydrocarbons or organic acids or a combination of both.

[0025] In this application, aromatic hydrocarbons may include substances such as benzene, toluene, and xylene, and organic acids may include substances such as citric acid and acetic acid.

[0026] In this application, alcohols may include substances such as ethanol.

[0027] Optionally, the deamination agent is selected from acids or acidic oxides or a combination of both.

[0028] Optionally, the carbon fiber exhaust gas further includes oxidation exhaust gas, and the hydroxyacetonitrile production method based on the carbon fiber exhaust gas further includes:

[0029] The tar and ammonia in the oxidized exhaust gas are removed to obtain purified exhaust gas;

[0030] The purified exhaust gas is mixed with the formaldehyde and the catalyst to carry out a nucleophilic addition reaction to obtain hydroxyacetonitrile.

[0031] Secondly, the present invention also provides a hydroxyacetonitrile production system based on carbon fiber tail gas, wherein the carbon fiber tail gas includes carbonization tail gas, and the hydroxyacetonitrile production system includes a carbonization tail gas tar removal treatment unit, a carbonization tail gas ammonia removal unit, and a hydroxyacetonitrile production unit. The hydroxyacetonitrile production unit includes several alternating stages of hydroxyacetonitrile reactors and a first gas-liquid separation mechanism, wherein the first stage hydroxyacetonitrile reactor is connected to the carbonization tail gas tar removal treatment unit and / or the carbonization tail gas ammonia removal unit.

[0032] Optionally, the hydroxyacetonitrile production system based on carbon fiber exhaust gas further includes a hydrogen cyanide absorption device, which is connected to the final stage first gas-liquid separation mechanism.

[0033] Optionally, the hydroxyacetonitrile production system based on carbon fiber exhaust gas further includes an incinerator connected to the hydrogen cyanide absorption device.

[0034] Optionally, the carbonized tail gas tar removal treatment unit includes:

[0035] The heat exchanger has an exhaust gas inlet and an exhaust gas outlet at the top, and a gas inlet and a material outlet at the bottom.

[0036] The second gas-liquid separation mechanism is provided with a feed inlet and a gas outlet. The feed inlet is connected to the material outlet. The second gas-liquid separation mechanism is located below the heat exchanger.

[0037] The device includes a tar removal unit, with an exhaust gas outlet and a solvent inlet at the top, and a tail gas inlet and a liquid outlet at the bottom. The tail gas inlet is connected to the gas outlet, and the exhaust gas outlet is connected to the first-stage hydroxyacetonitrile reactor.

[0038] Optionally, an induced draft fan is provided on the connecting pipe between the exhaust gas inlet of the tar removal device and the gas outlet of the gas-liquid separation device.

[0039] Optionally, a pressure control valve is provided on the connecting pipe between the gas outlet of the gas-liquid separation device and the induced draft fan.

[0040] Optionally, a gas mixer is provided on the connecting pipe between the induced draft fan and the exhaust gas inlet. The gas mixer has a circulation inlet, which is connected to the liquid outlet of the tar removal device. A circulation pump is provided on the connecting pipe between the circulation inlet of the gas mixer and the liquid outlet of the tar removal device. A cooling mechanism is provided on the connecting pipe between the circulation pump and the gas mixer.

[0041] Optionally, the carbonized tail gas ammonia removal treatment unit includes:

[0042] The system comprises several alternating stages of deammoniation reactors and circulating tanks, with each adjacent circulating tank connected to the previous one. All deammoniation reactors are equipped with inlets and outlets. The circulating tanks are connected to the inlets of the corresponding deammoniation reactors. The connecting pipe between the first-stage circulating tank and the inlet of the first-stage deammoniation reactor is also connected to an ammonium salt storage container. The last-stage circulating tank is connected to the first-stage hydroxyacetonitrile reactor.

[0043] In this invention, the beneficial effects of the carbonization tail gas deammoniation system and the carbon fiber production system are as follows:

[0044] This invention involves treating carbonized exhaust gas with tar and ammonia removal. After treatment, the exhaust gas undergoes a nucleophilic addition reaction with formaldehyde in the presence of a catalyst to produce hydroxyacetonitrile. This significantly reduces the content of hydrogen cyanide and ammonia in the exhaust gas, enabling the treated exhaust gas to meet emission standards.

[0045] This invention uses carbon fiber exhaust gas as a raw material to produce hydroxyacetonitrile, which improves resource utilization and economic benefits.

[0046] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0047] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0048] Figure 1 is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber tail gas in Example 1;

[0049] Figure 2 is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber tail gas in Example 2;

[0050] Figure 3 is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber tail gas in Example 3;

[0051] Figure 4 is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber tail gas in Example 4.

[0052] Figure 5 is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber tail gas in Example 5.

[0053] Figure 6 is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber tail gas in Example 6.

[0054] Attached figures: 1-Heat exchanger; 2-Induced draft fan; 3-Tar removal device; 4-Ammonia removal reactor; 41-Packed section; 42-Tray section; 421-Sieve plate; 43-Second level gauge; 5-Gas-liquid separation device; 51-Pressure gauge; 6-Pressure control valve; 7-Gas mixer; 8-Circulating pump; 9-Tar removal mechanism; 10-Hydrogen cyanide removal device; 11-Cooling device; 12-Hydroxyacetonitrile reactor; 13-Circulating tank; 131-First level gauge; 132-Flow regulating valve; 14-Ammonium salt storage container; 15-Cooling mechanism; 16-Second gas-liquid separation mechanism; 17-First gas-liquid separation mechanism; 18-Hydrogen cyanide absorption device; 19-Incinerator. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0056] It should be noted that all directional indicators (such as up, down, top, bottom, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0057] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, technical solutions between various embodiments can be combined, but only if they are feasible for those skilled in the art. If a combination of technical solutions is contradictory or impossible to implement, it should be considered non-existent and not within the scope of protection claimed by this invention. In related technologies, combustion emissions are commonly used to treat the exhaust gas generated during the carbonization process. This treatment method is ineffective, and the treated exhaust gas still fails to meet emission standards, causing environmental pollution and, to some extent, wasting resources. Based on the above technical problems, one embodiment of this invention provides a method for producing hydroxyacetonitrile based on carbon fiber exhaust gas, where the carbon fiber exhaust gas includes carbonization exhaust gas, and the hydroxyacetonitrile production method includes the following steps:

[0059] The carbonized tail gas is subjected to tar removal and ammonia removal treatment to obtain treated tail gas;

[0060] The tar removal process includes: mixing a gaseous cooling medium with carbonized tail gas for heat exchange to obtain crude tar;

[0061] The crude tar is subjected to gas-liquid separation, and the separated gas is mixed with a second solvent to absorb the tar in the gas. The second solvent is selected from aromatic hydrocarbons or organic acids or a combination of the two.

[0062] Ammonia removal treatment: The exhaust gas after tar removal is mixed with an ammonia removal agent to remove ammonia from the exhaust gas. The ammonia removal agent is selected from acids or acidic oxides or a combination of both.

[0063] After treatment, the exhaust gas and formaldehyde undergo a nucleophilic addition reaction at 0-40℃ for 1-6 hours in the presence of a catalyst to obtain hydroxyacetonitrile. The catalyst is selected from at least one of cyanate, alkali metal hydroxide and alkali metal sulfite, and the molar ratio of catalyst to formaldehyde is 0.001-0.015:1.0-1.5.

[0064] After the nucleophilic addition reaction, the system after the nucleophilic addition reaction is subjected to gas-liquid separation, the separated gas is mixed with the first solvent, and the remaining gas after mixing is incinerated. The first solvent is selected from at least one of alcohol, ether, aldehyde, benzene and water.

[0065] In another embodiment of the present invention, the carbon fiber exhaust gas further includes oxidation exhaust gas, and the method for producing hydroxyacetonitrile based on the carbon fiber exhaust gas further includes:

[0066] The tar and ammonia in the oxidized exhaust gas are removed to obtain purified exhaust gas;

[0067] The purified exhaust gas was mixed with formaldehyde and a catalyst to carry out a nucleophilic addition reaction to obtain hydroxyacetonitrile.

[0068] Another embodiment of the present invention provides a hydroxyacetonitrile production system based on carbon fiber tail gas, wherein the carbon fiber tail gas includes carbonization tail gas, and the hydroxyacetonitrile production system includes a carbonization tail gas tar removal treatment unit, a carbonization tail gas ammonia removal unit, and a hydroxyacetonitrile production unit.

[0069] The hydroxyacetonitrile production unit includes several alternating stages of hydroxyacetonitrile reactors 12 and a first gas-liquid separation unit 17;

[0070] The carbonized tail gas tar removal treatment unit includes:

[0071] Heat exchanger 1 has an exhaust gas inlet and an exhaust gas outlet at the top, and a gas inlet and a material outlet at the bottom;

[0072] The second gas-liquid separation mechanism 16 is provided with a feed inlet and a gas outlet. The feed inlet is connected to the material outlet. The second gas-liquid separation mechanism 12 is located below the heat exchanger 1.

[0073] The tar removal device 3 has an exhaust gas outlet and a solvent inlet at the top, and a tail gas inlet and a liquid outlet at the bottom. The tail gas inlet is connected to the gas outlet, and the exhaust gas outlet is connected to the first-stage hydroxyacetonitrile reactor 12.

[0074] The carbonization tail gas ammonia removal treatment unit includes:

[0075] Several alternating stages of deammoniation reactors 5 and circulation tanks 13 are connected. The next stage circulation tank 13 is connected to the next stage circulation tank 13. All deammoniation reactors 5 are equipped with inlets and outlets. Circulation tanks 13 are connected to the inlets of the corresponding stage deammoniation reactors 5. The connecting pipe between the first stage circulation tank 13 and the inlet of the first stage deammoniation reactor 5 is also connected to an ammonium salt storage container 14. The last stage circulation tank 13 is connected to the first stage hydroxyacetonitrile reactor 12.

[0076] In another embodiment of the present invention, the hydroxyacetonitrile production system based on carbon fiber tail gas further includes a hydrogen cyanide absorption device 18, which is connected to the last stage first gas-liquid separation mechanism 17.

[0077] In another embodiment of the present invention, the hydroxyacetonitrile production system based on carbon fiber tail gas further includes an incinerator 19, which is connected to a hydrogen cyanide absorption device 18.

[0078] The present invention will be described in detail below through specific examples and embodiments. It should also be understood that the following embodiments are only for specific illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0079] Example 1

[0080] Please refer to Figure 1. Figure 1 is a schematic diagram of the structure of the hydroxyacetonitrile production system based on carbon fiber tail gas in this embodiment. The hydroxyacetonitrile production system based on carbon fiber tail gas includes a carbonization tail gas tar removal treatment unit, a carbonization tail gas ammonia removal unit, and a hydroxyacetonitrile production unit. The carbonization tail gas tar removal treatment unit includes a heat exchanger 1, a gas-liquid separation device 5, and a tar removal device 3.

[0081] Please refer to Figure 1. Heat exchanger 1 serves as the site for heat exchange of the exhaust gas. The upper part of heat exchanger 1 has an exhaust gas inlet and an outlet, while the lower part has a gas inlet and a material outlet. The bottom of heat exchanger 1 also has a material outlet. The exhaust gas inlet is connected to a main pipeline, which in turn connects to a first branch pipeline and a second branch pipeline. Higher-temperature carbonized exhaust gas can enter heat exchanger 1 through the exhaust gas inlet, while lower-temperature gases such as nitrogen can enter through the lower gas inlet. The lower-temperature gases, including nitrogen, gradually rise and exchange heat with the higher-temperature exhaust gas, thus lowering the exhaust gas temperature. The tar in the exhaust gas cools and condenses, separating from the exhaust gas.

[0082] Specifically, in this embodiment, by connecting the exhaust gas inlet of the heat exchanger 1 to a main pipe 11, and the main pipe 11 to a first branch pipe and a second branch pipe, the exhaust gas with a temperature of about 600°C generated during the low-temperature carbonization process and the exhaust gas with a temperature of about 900°C generated during the high-temperature carbonization process can be mixed through the main pipe and then sent to the heat exchanger 1 for treatment, thereby improving the treatment efficiency.

[0083] Please refer to Figure 1. The gas-liquid separation device 5 is used to separate the removed tar (containing some tail gas) into gas and liquid components. The gas-liquid separation device 5 is located below the heat exchanger 1 and includes a feed inlet, a gas outlet, a tar outlet, and a pressure gauge 51. The feed inlet of the gas-liquid separation device 5 is connected to the material outlet of the heat exchanger 1. The gas-liquid separation device 5 can be a gas-liquid separator, a gas buffer tank, etc. Gas-liquid separators and gas buffer tanks are existing technologies and will not be described in detail here.

[0084] Specifically, in this embodiment, the gas-liquid separation device 5 is equipped with a pressure gauge 51, which can adjust the pressure of the gas-liquid separation device 5 to ensure the stability of the pressure during the production process, thereby ensuring the stable operation of the system.

[0085] Please refer to Figure 1. The tar removal device 3 serves as a site for removing tar and hydrogen cyanide from the exhaust gas. The upper part of the tar removal device 3 has a waste gas outlet and a solvent inlet, while the lower part has a tail gas inlet and a liquid outlet. The tail gas inlet connects to the gas outlet of the gas-liquid separator 5. Inside the tar removal device 3, a second solvent (e.g., aromatics or organic acids) absorbs and dissolves the tar in the exhaust gas, thereby further recovering the tar entrained in the exhaust gas. The tar removal device 3 can employ a circulation tank, etc. Circulation tanks are existing technology and will not be described in detail here.

[0086] Please refer to Figure 1. An induced draft fan 2 is installed on the connecting pipe between the exhaust gas inlet of the tar removal device 3 and the gas outlet of the gas-liquid separator 5. The induced draft fan 2 is used to extract the exhaust gas containing a small amount of tar and send it into the tar removal device 3, providing power for the exhaust gas and thus ensuring a sufficient supply of exhaust gas to the tar removal device 3, thereby improving processing efficiency. A pressure control valve 6 is installed on the connecting pipe between the gas outlet and the induced draft fan 2.

[0087] Specifically, in this embodiment, a pressure control valve 6 is added to the connecting pipe between the gas outlet and the induced draft fan 2. The pressure of the gas discharged from the gas-liquid separation mechanism 2 can be adjusted by the pressure control valve 6, thereby further ensuring the stability of the pressure during the production process and ensuring the stable operation of the system.

[0088] Please refer to Figure 1. A gas mixer 7 is installed on the connecting pipe between the induced draft fan 2 and the exhaust gas inlet. The gas mixer 7 has a circulation inlet, which is connected to the liquid outlet of the tar removal device 3. A circulation pump 8 is installed on the connecting pipe between the circulation inlet of the gas mixer 7 and the liquid outlet of the tar removal device 3. A cooling device 11 is installed on the connecting pipe between the circulation pump 8 and the gas mixer 7. The cooling device 11 can be a circulating cooler, which is existing technology and will not be described in detail here.

[0089] Specifically, in this embodiment, a gas mixer 7 is added to the connecting pipe between the induced draft fan 2 and the exhaust gas inlet, and the liquid outlet is connected to the circulation inlet of the gas mixer 7. A circulation pump 8 is installed on the connecting pipe between the liquid outlet and the circulation inlet of the gas mixer 7. The circulation pump 8 can send the tar carrying a small amount of gas into the cooling device 11. The cooling device 11 can reduce the temperature of the tar carrying a small amount of gas. After the tar cools and condenses, some of the tar is separated from the exhaust gas. The exhaust gas carrying a small amount of tar enters the gas mixer 7 after separation. After being mixed evenly with the exhaust gas drawn by the induced draft fan 2, it enters the tar removal device 3 again for tar removal treatment, thereby further recovering the tar.

[0090] Please refer to Figure 1. The tar outlet and / or circulating pump 8 of the gas-liquid separation device 5 are also connected to a tar removal mechanism 9 and / or a hydrogen cyanide removal device 10. The tar removal mechanism 9 is equipped with a tar discharge port, and the hydrogen cyanide removal device 10 is equipped with a hydrogen cyanide outlet and a solvent outlet. The solvent outlet of the hydrogen cyanide removal device 10 is connected to the solvent inlet of the tar removal device 3. The tar removal mechanism 9 and the hydrogen cyanide removal device 10 can be made of distillation columns, etc. Distillation columns are existing technology and will not be described in detail here.

[0091] Specifically, this embodiment adds a tar removal mechanism 9, which removes solvents, hydrogen cyanide, and other substances entrained in the tar, thereby improving the purity of the tar. By connecting the solvent outlet of the hydrogen cyanide removal device 10 to the solvent inlet of the tar removal device 3, the solvent removed from the tar can be fed into the tar removal device 3 for reuse as a second solvent, improving resource utilization, reducing costs, and increasing profits.

[0092] Please refer to Figure 1. The carbonization tail gas deammoniation treatment unit includes several alternating deammoniation reactors 4 and circulation tanks 13. The adjacent next-level circulation tank 13 is connected to the adjacent previous-level circulation tank 13. All deammoniation reactors 4 are equipped with inlets and outlets. The circulation tank 13 is connected to the inlet of the corresponding level deammoniation reactor 4. The connecting pipe between the first-level circulation tank 13 and the inlet of the first-level deammoniation reactor 4 is also connected to an ammonium salt storage container 14.

[0093] Please refer to Figure 1. The ammonia removal reactor 4 serves as the site for removing ammonia from the tail gas. A spray assembly (not shown) is installed at the top of the reactor 4. All reactors 4 have a tail gas inlet and a feed inlet at the top, with the feed inlet connected to the spray assembly. All reactors 4 have a discharge outlet at the bottom. Between the feed inlet and discharge outlet are a packing section 42 and a tray section 43, with several sieve plates 431 located on the sidewalls from top to bottom. The spray assembly is connected to the feed inlet. The ammonia removal reactor 4 is equipped with a second level gauge 41, which is electrically connected to the discharge outlet of the corresponding stage of the reactor 4. The tail gas inlet of the first-stage ammonia removal reactor 4 is connected to the exhaust gas outlet of the tar removal device 3. The feed inlet serves as the inlet for substances such as sulfuric acid solution to enter the ammonia removal reactor 4. Inside the reactor 4, sulfuric acid reacts with ammonia in the tail gas to produce ammonium sulfate and water, thereby removing ammonia from the tail gas.

[0094] Specifically, in this embodiment, a packing section 42 and a tray section 43 are sequentially arranged between the inlet and outlet of the ammonia removal reactor 4. Several sieve plates 431 are installed on the side walls of the tray section 43 from top to bottom. The packing ensures effective absorption of the exhaust gas, while the sieve plates 431 prevent trace amounts of tar in the exhaust gas from clogging the ammonia removal reactor 43, thus ensuring smooth production. A spray assembly is installed at the top of the ammonia removal reactor 4 and connected to the inlet. This increases the contact area between substances such as dilute sulfuric acid and the exhaust gas, thereby better removing ammonia and other substances from the exhaust gas. The ammonia removal reactor 43 is equipped with a second level gauge 41, which is electrically connected to the outlet of the corresponding level of the ammonia removal reactor 43. This allows for automatic discharge of material when the liquid level in the ammonia removal reactor 4 reaches a certain level, improving processing efficiency.

[0095] Please refer to Figure 1. Circulation tanks 13 are installed on the connecting pipes between adjacent ammonia removal reactors 4 and downstream of the last-stage ammonia removal reactor 13. The next-stage circulation tank 13 is connected to the next-stage circulation tank 13. All circulation tanks 13 are equipped with an acid inlet, a first level gauge 131, and a discharge port. The first level gauge 131 is electrically connected to the discharge port of the corresponding stage. The discharge port of the circulation tank 13 is connected to the feed inlet of the corresponding-stage ammonia removal reactor 4. A circulation pump is installed on the connecting pipe between the discharge port of the circulation tank 13 and the feed inlet of the corresponding-stage ammonia removal reactor 4. The last-stage circulation tank 13 has a feed pipe with a flow control valve 132, which is signal-connected to the first level gauge 131 of the last-stage circulation tank 13. The circulation pump is used to pump the sulfuric acid solution in the circulation tank to the next-stage adjacent ammonia removal reactor 4.

[0096] Specifically, in this embodiment, by electrically connecting the first level gauge 131 to the lower outlet of the corresponding level circulation tank 13, the lower outlet of the circulation tank 13 can be opened when the first level gauge 131 detects that the liquid level in the circulation tank 13 has reached a first preset liquid level threshold, thereby achieving automated control and improving efficiency. By installing a flow regulating valve 132 on the feed pipe connected to the last-stage circulation tank 13 and connecting the flow regulating valve 132 to the first level gauge 131 of the last-stage circulation tank 13, the flow rate of the sulfuric acid solution can be automatically reduced by the flow regulating valve 132 when the liquid level in the last-stage circulation tank 13 reaches a certain level, thus avoiding negative impacts on production caused by excessive material in the last-stage circulation tank 13.

[0097] Please refer to Figure 1. The connecting pipe between the outlet of the first-stage circulating tank 13 and the first-stage deammoniation reactor 4 is also connected to an ammonium salt storage container 14. The ammonium salt storage container 14 is used as a place to store the ammonium salt (e.g., ammonium sulfate solution) generated after the ammonia gas in the tail gas reacts with the deammoniation agent (the deammoniation agent is selected from an acid or an acidic oxide or a combination of the two).

[0098] Specifically, this embodiment uses several alternating stages of ammonia removal reactors 4 and circulating tanks 13. Each adjacent lower-level circulating tank 13 is connected to its adjacent upper-level circulating tank 13. All ammonia removal reactors 1 are equipped with inlets and outlets. The circulating tanks 13 are connected to the inlets of the corresponding level of ammonia removal reactor 4. The connecting pipe between the first-level circulating tank 13 and the outlet of the first-level ammonia removal reactor 4 is also connected to an ammonium salt storage container 14, enabling the tail gas to be transported in the opposite direction to the ammonia removal agent (selected from acids, acidic oxides, or a combination thereof). This process employs a counter-current method to treat ammonia gas. A deammoniation agent (selected from acids, acidic oxides, or combinations thereof, such as sulfuric acid) is continuously introduced into the last-stage circulation tank. The deammoniation agent gradually flows from the last-stage circulation tank 13 to the first-stage circulation tank 13 and then into the first-stage deammoniation reactor 4. The tail gas to be treated is introduced into the first-stage deammoniation reactor 4. Ammonia in the tail gas reacts with sulfuric acid solution to produce ammonium sulfate. After the reaction, the system gradually passes through the first-stage circulation tank 13 and sequentially enters the phase... In the next stage deammoniation reactor 4, sulfuric acid solution is fed into the reactor through the circulation tank 13. Unreacted ammonia in the system continues to react with a deammoniation agent (selected from acids, acidic oxides, or combinations thereof, such as sulfuric acid). This continues until the system enters the final stage deammoniation reactor 4, where the reaction continues. After the reaction, the solution is fed into the final stage circulation tank 13, where a deammoniation agent (selected from acids, acidic oxides, or combinations thereof, such as sulfuric acid) is continuously introduced. The mixture is transported along the sulfuric acid conveying direction in the opposite direction to the tail gas conveying direction to the adjacent upstream circulation tank 13 and then to the first-stage circulation tank 13. That is, the concentration of acid and other deammoniation agents in the system in the last circulation tank 13 is the highest and the pH is the lowest, while the concentration of acid and other deammoniation agents in the system in the first-stage circulation tank is the lowest and the pH is the highest. It is then sent into the ammonium salt storage container 14 through the connecting pipe between the first-stage circulation tank 13 and the ammonium salt storage container 14, thereby ensuring that the obtained ammonium salt solution contains fewer acid radical ions and improving the purity of the ammonium salt product.

[0099] Please refer to Figure 1. A cooling mechanism 15 is installed on the connecting pipe between the circulating pump and the feed inlet of the adjacent upstream ammonia removal reactor 4. The cooling mechanism 15 is used to reduce the temperature of the incoming ammonia removal agent (if a mixture of concentrated sulfuric acid and water is introduced, the concentrated sulfuric acid will release heat during the dilution process). The cooling mechanism 15 can be a condenser, which is existing technology and will not be described in detail here.

[0100] Specifically, in this embodiment, a cooling mechanism 15 is added to the connecting pipe between the circulating pump and the feed inlet of the adjacent upstream deammoniation reactor 4. The cooling mechanism can cool the acid solution to reduce the heat released during the dilution of the deammoniation agent (if a mixture of concentrated sulfuric acid and water is usually introduced during the production process), thus avoiding excessive heat from causing safety hazards to the production.

[0101] Please refer to Figure 1. The vent of the last-stage circulation tank 13 is connected to the second gas-liquid separation mechanism 16. The second gas-liquid separation mechanism 16 is provided with an exhaust port and a liquid discharge port. The liquid discharge port is connected to the last-stage circulation tank 2, and the exhaust port is connected to the second gas-liquid separation mechanism 16. The second gas-liquid separation mechanism 16 is provided with an exhaust port and a liquid discharge port. The exhaust port is connected to the hydroxyacetonitrile reactor 12, and the liquid discharge port is connected to the last-stage circulation tank 13. The second gas-liquid separation mechanism 16 can be a gas-liquid separator, a gas buffer tank, etc. Gas-liquid separators and gas buffer tanks are existing technologies and will not be described in detail here.

[0102] Specifically, in this embodiment, by connecting the drain port of the second gas-liquid separation mechanism 16 to the last-stage circulation tank 13, ammonium salts in the system can be sent into the last-stage circulation tank 13, thereby facilitating the recovery of ammonium salts and other substances in the system and increasing profits.

[0103] Please refer to Figure 1. The hydroxyacetonitrile production unit includes several alternating stages of hydroxyacetonitrile reactors 12 and a first gas-liquid separation mechanism 17. The exhaust port of the first-stage hydroxyacetonitrile reactor 12 is connected to the exhaust port of the second gas-liquid separation mechanism 16. The first-stage hydroxyacetonitrile reactor is connected to the hydrogen cyanide outlet of the hydrogen cyanide removal device 10.

[0104] Please refer to Figure 1. The hydroxyacetonitrile reactor 12 serves as the reaction site for the reaction of hydrogen cyanide and formaldehyde in the tail gas to produce hydroxyacetonitrile under the catalysis of a catalyst. The hydroxyacetonitrile reactor 12 has a feed inlet and a circulation inlet at the top, and a discharge outlet at the bottom. The hydroxyacetonitrile reactor 12 is equipped with a temperature control component.

[0105] In this embodiment, by connecting the tar outlet and / or circulation pump 8 to a tar removal mechanism 9, the solvent and hydrogen cyanide entrained in the tar can be removed through the tar removal mechanism 9. By connecting the first-stage hydroxyacetonitrile reactor to the hydrogen cyanide outlet of the hydrogen cyanide removal device 10, the removed hydrogen cyanide gas can be sent to the first-stage hydroxyacetonitrile reactor 12 to produce hydroxyacetonitrile using hydrogen cyanide gas as raw material. This improves the purity of the tar and the resource utilization rate of hydrogen cyanide, thereby increasing economic benefits. By connecting the solvent outlet of the tar removal mechanism 9 to the tar removal device 3, the solvent separated from the tar removal mechanism 9 can be sent to the tar removal device 3 for reuse, reducing production costs and increasing profits.

[0106] Please refer to Figure 1. The first gas-liquid separation mechanism 17 is used to separate the gas and liquid components of the material after reaction in the hydroxyacetonitrile reactor 12. The feed inlet of the hydroxyacetonitrile reactor 12 is connected to the first end of the corresponding stage of the first gas-liquid separation mechanism 17. The second end of the first gas-liquid separation mechanism 17 is connected to the circulation inlet of the corresponding stage of the hydroxyacetonitrile reactor 12. A circulation pump is installed on the connecting pipe between the second end of the first gas-liquid separation mechanism 17 and the circulation inlet of the hydroxyacetonitrile reactor 12. The circulation pump is connected to the hydroxyacetonitrile storage container 18. The first gas-liquid separation mechanism 17 is provided with an exhaust port, a circulation feed port, and a discharge port. The discharge port of the last stage of the first gas-liquid separation mechanism 17 is connected to the circulation inlet of the last stage of the hydroxyacetonitrile reactor 12. A circulation pump is installed on the connecting pipe between the discharge port of the last stage of the first gas-liquid separation mechanism 17 and the circulation inlet of the last stage of the hydroxyacetonitrile reactor 12. The first gas-liquid separation mechanism 17 can be a circulation tank, which is existing technology and will not be described in detail here.

[0107] Specifically, in this embodiment, by connecting the first gas-liquid separation mechanism 17 to the circulation inlet of the corresponding stage hydroxyacetonitrile reactor 12, unreacted formaldehyde in the reaction system can be reintroduced into the hydroxyacetonitrile reactor 12 for further reaction, improving resource utilization and yield. By adding a tar removal mechanism 9, which connects the hydrogen cyanide removal device to the hydroxyacetonitrile reactor, hydrogen cyanide and solvent entrained in the tar can be removed, improving tar purity. By adding a hydrogen cyanide removal device 10, hydrogen cyanide can be removed from the mixed gas, thus separating the solvent from the hydrogen cyanide. By connecting the first-stage hydroxyacetonitrile reactor to the hydrogen cyanide outlet of the hydrogen cyanide removal device 10, the removed hydrogen cyanide gas can be fed into the first-stage hydroxyacetonitrile reactor 12, using hydrogen cyanide gas as a raw material to produce hydroxyacetonitrile. This improves both tar purity and the resource utilization rate of hydrogen cyanide, thereby increasing economic benefits.

[0108] It should be understood that all connecting pipes are equipped with switch valves.

[0109] The principle of this embodiment is as follows: by setting up a carbonized tail gas tar removal treatment unit, a carbonized tail gas ammonia removal unit, and a hydroxyacetonitrile production unit, and connecting the hydroxyacetonitrile production unit's hydroxyacetonitrile reactor 12 to the carbonized tail gas tar removal treatment unit and the carbonized tail gas ammonia removal unit, tar and ammonia in the carbonized tail gas can be removed and the tail gas can be sent into the hydroxyacetonitrile reactor 12 to produce hydroxyacetonitrile using hydrogen cyanide in the tail gas as raw material. Thus, while treating the tail gas, the byproduct hydroxyacetonitrile is obtained, thereby improving economic efficiency.

[0110] Example 2

[0111] Please refer to Figure 2, which is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber tail gas shown in Example 2.

[0112] As shown in Figure 2, the difference between this embodiment and Embodiment 1 is that the exhaust port of the last-stage first gas-liquid separation mechanism 17 is connected to a hydrogen cyanide absorption device 18. The hydrogen cyanide absorption device 18 serves as a site for dissolving and absorbing residual hydrogen cyanide gas in the tail gas. The upper part of the hydrogen cyanide absorption device 18 has an inlet and an exhaust port, while the lower part has a gas inlet and a discharge port. The gas inlet of the hydrogen cyanide absorption device 18 is connected to the exhaust port of the last-stage first gas-liquid separation mechanism 17. The hydrogen cyanide absorption device 18 has a circulating inlet. The discharge port of the hydrogen cyanide absorption device 18 is connected to the circulating inlet of the hydrogen cyanide absorption device 18. A circulating pump is installed on the connecting pipe between the discharge port and the circulating inlet of the hydrogen cyanide absorption device 18, and this circulating pump is connected to the circulating inlet of the last-stage first gas-liquid separation mechanism 17. A first solvent (e.g., alcohol, ether, aldehyde, benzene, water, etc.) can be introduced into the hydrogen cyanide absorption device 18 through the inlet. Within the hydrogen cyanide absorption device 18, a first solvent (e.g., alcohol, ether, aldehyde, benzene, water, etc.) can absorb and dissolve the remaining small amount of hydrogen cyanide gas in the tail gas. The hydrogen cyanide absorption device 18 can be a packed tower, which is existing technology and will not be described in detail here.

[0113] Specifically, in this embodiment, by adding a hydrogen cyanide absorption device 18 connected to the exhaust port of the last-stage first gas-liquid separation mechanism 17, the remaining small amount of hydrogen cyanide in the exhaust gas can be dissolved and absorbed by the first solvent introduced into the hydrogen cyanide absorption device 18, thereby further reducing the hydrogen cyanide content in the exhaust gas.

[0114] Example 3

[0115] Please refer to Figure 3, which is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber tail gas shown in Example 3.

[0116] As shown in Figure 3, the difference between this embodiment and embodiment 2 is that the exhaust port of the hydrogen cyanide absorption device 18 is connected to the incinerator 19, and the incinerator 19 is provided with an exhaust port.

[0117] Specifically, in this embodiment, by adding an incinerator 19 connected to the exhaust port of the hydrogen cyanide absorption device 18, the exhaust gas can be further treated by the incinerator 19, thereby reducing the content of harmful substances in the exhaust gas.

[0118] Example 4

[0119] Please refer to Figure 4, which is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber exhaust gas shown in this embodiment.

[0120] As shown in Figure 4, the difference between this embodiment and embodiment 3 is that the exhaust gas inlet of the tar removal device 3 and the gas outlet of the gas-liquid separation device 5 are not equipped with an induced draft fan 2 and a pressure control valve 6.

[0121] Example 5

[0122] Please refer to Figure 5, which is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber exhaust gas shown in this embodiment.

[0123] As shown in Figure 5, the difference between this embodiment and embodiment 3 is that a pressure control valve 6 is not installed on the connecting pipe between the gas outlet of the gas-liquid separator 5 and the induced draft fan 2.

[0124] Example 6

[0125] Please refer to Figure 6, which is a schematic diagram of the hydroxyacetonitrile production system based on carbon fiber exhaust gas shown in this embodiment.

[0126] As shown in Figure 6, the difference between this embodiment and embodiment 3 is that the gas mixer 7 and the cooling device 11 are not included.

[0127] Example 7

[0128] The system used in Example 3 was used to produce hydroxyacetonitrile, and the specific steps are as follows:

[0129] The low-temperature carbonization exhaust gas and the high-temperature carbonization exhaust gas are respectively sent into the first branch pipeline and the second branch pipeline, and then enter the main pipeline to obtain carbonized mixed exhaust gas (intake volume of 1500m³). 3 / h, total mass flow rate is 850kg / h, temperature is 800℃);

[0130] The carbonized mixed exhaust gas enters the heat exchanger 1 through the exhaust gas inlet. The lower temperature nitrogen enters the heat exchanger 1 through the gas inlet. The low temperature gases such as nitrogen entering the heat exchanger 1 gradually rise and exchange heat with the carbonized mixed exhaust gas entering the heat exchanger 1, thereby reducing the temperature of the exhaust gas. The tar in the exhaust gas cools down and condenses, separating from the exhaust gas.

[0131] The separated tar enters the gas-liquid separator 5 through the connecting pipe between the feed inlet of the gas-liquid separator 5 and the material outlet of the heat exchanger 1 under the action of gravity. Some of the gas entrained in the tar gradually floats to the top, while the liquid tar sinks to the bottom, thus achieving gas-liquid separation. During this process, the pressure of the gas-liquid separator 5 can be adjusted by the pressure gauge 51 to ensure the stability of the pressure during the production process, thereby ensuring the stable operation of the system.

[0132] Next, the induced draft fan 2 extracts the exhaust gas containing a small amount of tar and sends it sequentially into the gas mixer 7 and the tar removal device 3 to provide power for the exhaust gas, thereby providing a sufficient supply of exhaust gas to the gas mixer 7 and the tar removal device 3. In the tar removal device 3, the second solvent (specifically citric acid) can dissolve tar and hydrogen cyanide, which have high viscosity at low temperatures, thereby removing tar, hydrogen cyanide and other substances from the exhaust gas. The pressure of the gas discharged from the gas-liquid separation mechanism 2 is regulated by the pressure control valve 6, thereby further ensuring the stability of the pressure during the production process and ensuring the stable operation of the system.

[0133] Meanwhile, the circulating pump 8 sends the tar containing a small amount of gas into the cooling device 11. The cooling device 11 can reduce the temperature of the tar containing a small amount of gas. After the tar cools down, it condenses, causing some of the tar to separate from the tail gas. The tail gas carrying a small amount of tar after separation enters the gas mixer 7 and is mixed evenly with the tail gas drawn by the induced draft fan 2. Then it enters the tar removal device 3 again for tar removal treatment, and further recovers the tar.

[0134] Subsequently, the tar is fed into the tar removal mechanism 9, which removes the first solvent entrained in the tar. The removed first solvent is then sent to the tar removal device 3 for recycling.

[0135] Next, after the first solvent is removed, the tar is sent to the hydrogen cyanide removal unit 10, which removes the hydrogen cyanide gas entrained in the tar.

[0136] Then, the hydrogen cyanide gas removed from the hydrogen cyanide removal device 10 is sent into the hydroxyacetonitrile reactor 12;

[0137] A sulfuric acid solution (specifically a mixture of concentrated sulfuric acid and water, with a sulfuric acid concentration of 30 wt%) is introduced into the last-stage circulation tank 13. The sulfuric acid solution is transported in the opposite direction to the tail gas conveying direction to the adjacent previous-stage circulation tank 13 and then to the first-stage circulation tank 13. During this process, the cooling mechanism 15 cools the mixture (specifically, to room temperature) to reduce the heat released during the dilution of concentrated sulfuric acid (a mixture of concentrated sulfuric acid and water is usually introduced during the production process), and to avoid excessive heat causing safety hazards to the production process.

[0138] The sulfuric acid solution in the first-stage circulating tank 13 enters the first-stage deammoniation reactor 4. In the deammoniation reactor 4, at room temperature, the sulfuric acid reacts with ammonia in the tail gas to produce ammonium sulfate and water, thereby removing ammonia from the tail gas. The system is then transported to the adjacent next-stage deammoniation reactor 4 for further reaction. Sulfuric acid solution is fed into this next-stage reactor 4 through the circulating tank 13, and any unreacted ammonia in the system continues to react with sulfuric acid. This process continues until the system enters the final-stage deammoniation reactor 4, where the reaction continues. After the reaction, the solution is sent back to the final-stage circulating tank 13 to continue its reaction. Sulfuric acid solution is introduced into the first-stage circulation tank 13 to obtain a mixture. The mixture is transported along the sulfuric acid conveying direction in the opposite direction to the tail gas conveying direction to the adjacent previous-stage circulation tank 13 until it reaches the first-stage circulation tank 13. That is, the sulfuric acid concentration and pH are the highest in the system in the last-stage circulation tank 13, while the sulfuric acid concentration and pH are the lowest in the system in the first-stage circulation tank 13. The mixture is then sent into the ammonium salt storage container 14 through the connecting pipe between the first-stage circulation tank 13 and the ammonium salt storage container 14, thereby ensuring that the obtained ammonium sulfate solution contains fewer sulfate ions and improving the purity of the ammonium sulfate product.

[0139] Subsequently, the unreacted exhaust gas enters the second gas-liquid separation mechanism 16 through the connecting pipe between the vent of the last stage circulation tank 13 and the second gas-liquid separation mechanism 16 to achieve gas-liquid separation, thereby separating out some of the solution entrained in the exhaust gas.

[0140] After being processed by the second gas-liquid separation unit 16, the exhaust gas is sent into the first-stage hydroxyacetonitrile reactor 12.

[0141] A mixture of formaldehyde and catalyst (specifically sodium cyanide, with a molar ratio of sodium cyanide to formaldehyde of 0.01:1.5) is introduced into the first-stage hydroxyacetonitrile reactor 12. In the first-stage hydroxyacetonitrile reactor 12, at room temperature, hydrogen cyanide gas in the tail gas reacts with formaldehyde under the catalytic action of the catalyst to produce hydroxyacetonitrile.

[0142] After the reaction, the system is then sent to the first gas-liquid separation unit 17 for gas-liquid separation. The separated liquid phase is sent to the hydroxyacetonitrile storage container 18, and the separated gas phase is sent to the adjacent next-stage hydroxyacetonitrile reactor 12 to continue the reaction until it is sent to the last-stage hydroxyacetonitrile reactor 12. In the last-stage hydroxyacetonitrile reactor 12, at room temperature, hydrogen cyanide gas in the tail gas reacts with formaldehyde under the catalysis of a catalyst to generate hydroxyacetonitrile, which is then sent to the last-stage first gas-liquid separation unit 17. The separated liquid phase is sent to the hydroxyacetonitrile storage container 18, and the separated gas phase is sent to the hydrogen cyanide absorption device 18. In the hydrogen cyanide absorption device 18, the first solvent (specifically formaldehyde) dissolves and absorbs the remaining small amount of hydrogen cyanide gas in the tail gas.

[0143] Next, the exhaust gas is sent to incinerator 19 for further treatment to reduce the content of harmful substances in the exhaust gas.

[0144] After being treated in an incinerator, the exhaust gas is released into the atmosphere.

[0145] According to statistics, the production method described in this embodiment yields approximately 0.94 tons of hydroxyacetonitrile per ton of carbonized mixed tail gas. Based on a market price of approximately 8,000 yuan / ton, the revenue per ton of carbonized mixed tail gas is at least 7,520 yuan (excluding the byproduct ammonium sulfate).

[0146] Detection

[0147] The flow rates and concentrations of hydrogen cyanide, ammonia, carbon monoxide, and tar in the carbonized mixed exhaust gas of Example 7 were detected using a gas detector, as well as the flow rates and concentrations of hydrogen cyanide, ammonia, carbon monoxide, and tar in the exhaust gas emitted into the atmosphere. The results are shown in Table 1.

[0148] Table 1. Detection results of mass flow rate and concentration of each component. Note: -- indicates not detected, i.e., exceeding the detection limit, the same below. The total mass flow rate in this table refers to the corresponding mass flow rate of each component.

[0149] As shown in Table 1, after treatment in Example 7, the contents of hydrogen cyanide, ammonia, and carbon monoxide in the exhaust gas were significantly reduced. The levels of hydrogen cyanide and ammonia in the treated exhaust gas were both far below the emission standard thresholds. This result demonstrates that the method of the present invention can significantly reduce the content of hydrogen cyanide and ammonia in the exhaust gas, and the treated exhaust gas can meet the emission standards.

[0150] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for producing hydroxyacetonitrile based on carbon fiber tail gas, wherein the carbon fiber tail gas includes carbonization tail gas, characterized in that, The method for producing hydroxyacetonitrile includes the following steps: The carbonized tail gas is subjected to tar removal and ammonia removal treatment to obtain treated tail gas; After treatment, the exhaust gas undergoes a nucleophilic addition reaction with formaldehyde in the presence of a catalyst to yield hydroxyacetonitrile.

2. The method for producing hydroxyacetonitrile based on carbon fiber tail gas as described in claim 1, characterized in that, The nucleophilic addition reaction is carried out at a temperature of 0-40°C and for a duration of 1-6 hours. And / or, the catalyst is selected from at least one of cyanates, alkali metal hydroxides and alkali metal sulfites; And / or, the molar ratio of the catalyst to formaldehyde is 0.001-0.015:1.0-1.5; And / or, after the nucleophilic addition reaction, the method further includes: performing gas-liquid separation on the system after the nucleophilic addition reaction, and mixing the separated gas with the first solvent; And / or, the tar removal process includes: A mixed gaseous cooling medium is used to exchange heat with carbonized tail gas to obtain crude tar. The crude tar is subjected to gas-liquid separation, and the separated gas is mixed with a second solvent to absorb the tar in the gas; And / or, the deammoniation treatment includes: The exhaust gas after tar removal is mixed with a deammonigenin to remove ammonia from the exhaust gas.

3. The method for producing hydroxyacetonitrile based on carbon fiber tail gas as described in claim 2, characterized in that, The first solvent is selected from at least one of alcohols, ethers, aldehydes, benzene compounds, and water; And / or, after mixing the separated gas with the first solvent, the method further includes: incinerating the remaining gas after mixing.

4. The method for producing hydroxyacetonitrile based on carbon fiber tail gas as described in claim 2, characterized in that, The second solvent is selected from at least one of aromatic hydrocarbons or organic acids or combinations thereof; And / or, the deamination agent is selected from acids or acidic oxides or a combination of both.

5. The method for producing hydroxyacetonitrile based on carbon fiber tail gas as described in claim 1, characterized in that, The carbon fiber exhaust gas also includes oxidation exhaust gas, and the hydroxyacetonitrile production method based on the carbon fiber exhaust gas further includes: The tar and ammonia in the oxidized exhaust gas are removed to obtain purified exhaust gas; The purified exhaust gas is mixed with the formaldehyde and the catalyst to carry out a nucleophilic addition reaction to obtain hydroxyacetonitrile.

6. A hydroxyacetonitrile production system based on carbon fiber tail gas, wherein the carbon fiber tail gas includes carbonization tail gas, characterized in that, The hydroxyacetonitrile production system includes a carbonization tail gas tar removal treatment unit, a carbonization tail gas ammonia removal unit, and a hydroxyacetonitrile production unit. The hydroxyacetonitrile production unit includes several alternating stages of hydroxyacetonitrile reactors and a first gas-liquid separation mechanism. The first stage hydroxyacetonitrile reactor is connected to the carbonization tail gas tar removal treatment unit and / or the carbonization tail gas ammonia removal unit.

7. The hydroxyacetonitrile production system based on carbon fiber tail gas as described in claim 6, characterized in that, It also includes a hydrogen cyanide absorption device, which is connected to the final stage first gas-liquid separation mechanism.

8. The hydroxyacetonitrile production system based on carbon fiber exhaust gas as described in claim 7, characterized in that, It also includes an incinerator connected to the hydrogen cyanide absorption device.

9. The hydroxyacetonitrile production system based on carbon fiber tail gas as described in claim 6, characterized in that, The carbonized tail gas tar removal treatment unit includes: The heat exchanger has an exhaust gas inlet and an exhaust gas outlet at the top, and a gas inlet and a material outlet at the bottom. The second gas-liquid separation mechanism is provided with a feed inlet and a gas outlet. The feed inlet is connected to the material outlet. The second gas-liquid separation mechanism is located below the heat exchanger. The device includes a tar removal unit, with an exhaust gas outlet and a solvent inlet at the top, and a tail gas inlet and a liquid outlet at the bottom. The tail gas inlet is connected to the gas outlet, and the exhaust gas outlet is connected to the first-stage hydroxyacetonitrile reactor.

10. The hydroxyacetonitrile production system based on carbon fiber tail gas as described in claim 6, characterized in that, The carbonized tail gas ammonia removal treatment unit includes: The system consists of several alternating stages of deammoniation reactors and circulating tanks. The next-level circulating tank is connected to the next-level circulating tank. All deammoniation reactors are equipped with inlets and outlets. The circulating tanks are connected to the inlets of the corresponding deammoniation reactors. The connecting pipe between the first-level circulating tank and the inlet of the first-level deammoniation reactor is also connected to an ammonium salt storage container. The last-level circulating tank is connected to the first-level hydroxyacetonitrile reaction.

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