Method and system for treating polycarbonate production waste salt
By using low-temperature and high-temperature microwave pyrolysis technology in the treatment of waste salt for polycarbonate production, volatile and difficult-to-volatile organic matter were removed separately to form solid sodium chloride salt, which solved the problems of difficult treatment and secondary pollution in the existing technology. It realizes efficient purification and recycling of waste salt.
Patent Information
- Application Number
- CN202411481728.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-23
- Publication Date
- 2025-02-18
AI Technical Summary
When processing polycarbonate waste salt, the prior art has problems such as harsh reaction conditions, high equipment requirements and high operating costs. In the incineration method and high temperature thermal melting method, the energy required is high and the secondary pollutants are generated. , it is difficult to achieve effective processing and recycling.
The microwave pyrolysis method is adopted for two-stage microwave pyrolysis methods, and microwave heating treatment is carried out at 150-190℃ and 550-600℃ respectively. The volatile organic matter is removed through low-temperature pyrolysis, and the volatile organic matter is removed through high-temperature pyrolysis to form Solid salt of sodium chloride and dioxin is reduced by quench cooling treatment.
The comprehensive purification and utilization of waste salts for polycarbonate production has been achieved, reducing the generation of toxic waste gases, protecting the ecological environment, and improving the pyrolysis efficiency and reducing energy consumption.
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Figure CN119455880A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of waste salt treatment, and relates to a method and a system for treating waste salt produced by polycarbonate. Background Art
[0002] Polycarbonate, also known as PC plastic, is a high molecular polymer containing carbonate groups in the molecular chain. Polycarbonate has high strength and elastic modulus, high impact strength and fatigue resistance, and is mainly used in glass assembly industry, automobile industry, electronics industry and electrical appliance industry.
[0003] The production methods of polycarbonate mainly include the transesterification method and the phosgene direct method. When polycarbonate is prepared by the phosgene direct method, the waste salt produced by the polymerization unit contains certain organic impurities, and the waste salt needs to be treated before it can be recycled. At present, the main treatment methods for waste salt in polycarbonate production are wet and dry. Among them, wet treatment refers to first dissolving the waste salt in water, and degrading organic pollutants through deep organic oxidation technology in the field of water treatment to achieve harmlessness of waste salt. Among them, commonly used organic oxidation technologies include advanced oxidation, wet catalytic oxidation and hydrothermal oxidation technology. Dry treatment includes incineration, high-temperature hot melting, organic carbonization pyrolysis, etc.
[0004] However, the wet treatment has harsh reaction conditions, high equipment requirements, and high operating costs. It cannot be applied to the treatment of organic wastewater with ultra-high concentration brine, which limits its widespread application. The temperature required for incineration and high-temperature hot melting methods is between 800-1200°C, so the energy required is high and more secondary pollutants are generated, which poses great obstacles in practical applications. The carbonization pyrolysis method of organic matter started late and is now gradually being promoted. Public information shows that the mainstream technology control temperature of this method in the market is 200-500°C, and this temperature range is exactly the favorable condition for the pyrolysis of chlorine- or bromine-containing organic matter to produce dioxins, which are extremely toxic, difficult to degrade, and difficult to remove pollutants. Summary of the invention
[0005] The purpose of the present invention is to provide a method and system for treating waste salt produced in polycarbonate production, so as to solve the problem that the existing treatment method cannot effectively treat waste salt produced in polycarbonate production.
[0006] To achieve the above object, the present invention adopts the following technical solutions: The present application provides a method for treating waste salt from polycarbonate production, the method comprising: S01: The sealed, nitrogen-filled waste salt from the production of polycarbonate is transported to a low-temperature pyrolysis device, and subjected to microwave heating treatment at a temperature of 150-190°C for 5-10 minutes to obtain treated salt and low-temperature decomposition waste gas.
[0007] In the present application, the waste salt from polycarbonate production refers to the solid sodium chloride by-product produced by the phosgene method polycarbonate polymerization unit, which meets the first-class quality standard of "Polycarbonate By-product Sodium Chloride" (T / CPCIF 0080-2020) issued by the China Petroleum and Chemical Industry Federation as shown in Table 1, but cannot meet the TOC limit requirements of "Perfluorinated Ion Exchange Membrane for Chlor-alkali Industry-Application Specification" (GB / T 30297-2013) shown in Table 2. Therefore, it cannot be used as raw salt in the chlor-alkali industry.
[0008] Table 1: Grade 1 quality standard of "Sodium Chloride as By-product of Polycarbonate" (T / CPCIF 0080-2020) Table 2: Requirements for TOC limits in the "Perfluorinated Ion Exchange Membranes for Chlor-Alkali Industry - Application Specifications" (GB / T 30297-2013) The waste salt from the production of polycarbonate is stored in a closed storage tank filled with nitrogen, and the pressure is maintained at a slightly positive pressure state of less than or equal to 6.9 kPa, so as to facilitate the smooth transportation of the waste salt from the production of polycarbonate. The waste salt from the production of polycarbonate is transported to the low-temperature pyrolysis device through a conveyor. The low-temperature pyrolysis device is equipped with a microwave generator, which can heat the temperature in the low-temperature pyrolysis device to 150-190°C, so that most of the volatile organic matter in the waste salt from the production of polycarbonate is decomposed through thermal decomposition to form low-temperature decomposition waste gas, and the decomposed waste salt from the production of polycarbonate forms treated salt. The low-temperature decomposition waste gas is introduced into the activated carbon injector through a low-temperature induced draft fan, and after being adsorbed by the activated carbon, it is sent to the bag filter for dust removal and then discharged in compliance with the standards.
[0009] Furthermore, in order to improve the collection efficiency of low-temperature decomposition waste gas, the low-temperature pyrolysis device is maintained at a slightly negative pressure state of -1.5-2.0 kPa.
[0010] In addition, a screw conveyor is installed in the low-temperature pyrolysis device to achieve pyrolysis while transporting the waste salt from the production of polycarbonate. Preferably, the microwave generators are distributed on both sides of the screw conveyor to ensure uniform heating temperature in the low-temperature pyrolysis device.
[0011] S02: The treated salt is transported to a high-temperature pyrolysis device and subjected to microwave heating treatment at a temperature of 550-600° C. for 5-10 minutes to obtain solid sodium chloride salt and high-temperature decomposition waste gas.
[0012] The treated salt is transported to a high-temperature pyrolysis device, which is equipped with a microwave generator and a screw conveyor. The microwave generator can heat the temperature in the high-temperature pyrolysis device to 550-600°C, so that most of the non-volatile organic matter in the treated salt is thermally decomposed to form high-temperature decomposition waste gas, and the decomposed treated salt forms solid sodium chloride salt. The TOC value of the solid sodium chloride salt is controlled within 25 mg / Kg, which meets the requirements of "Industrial Salt" (GB / T 5462-2015) and "Perfluorinated Ion Exchange Membrane for Chlor-Alkali Industry-Application Specification" (GB / T 30297-2013).
[0013] The high-temperature decomposition waste gas is introduced into the quench tower through a high-temperature induced draft fan for rapid cooling and cooling treatment, so that the temperature of the high-temperature decomposition waste gas is reduced to below 200°C, shortening the time of the high-temperature decomposition waste gas in the range of 200-500°C, reducing the secondary generation of dioxin waste gas, and recovering heat at the same time. In this application, the rapid cooling of the high-temperature decomposition waste gas is water rapid cooling, and water mist will be generated during the rapid cooling process. In order to prevent the water vapor entrained in the high-temperature decomposition waste gas after rapid cooling from hindering adsorption and dust removal, the high-temperature decomposition waste gas after rapid cooling is first defogged by a demister, and then adsorbed by activated carbon in an activated carbon injector and dusted by a bag filter before reaching the emission standard.
[0014] Similarly, in order to improve the collection efficiency of high-temperature decomposition waste gas and reduce the unorganized emission of highly toxic waste gas dioxins, the high-temperature pyrolysis device also maintains a slightly negative pressure state of -1.5-2.0kPa.
[0015] In the present application, the temperature control in the low-temperature pyrolysis device and the high-temperature pyrolysis device is achieved by adjusting the frequency of the microwave generator.
[0016] In addition, the present application also provides a system for treating waste salt from polycarbonate production, which includes a storage tank, a conveyor, a low-temperature pyrolysis device and a high-temperature pyrolysis device that are connected in sequence, the low-temperature pyrolysis device is connected to an activated carbon injector through a low-temperature induced draft fan, and the high-temperature pyrolysis device is connected to the activated carbon injector through a high-temperature induced draft fan, a quench cooler, and a demister in sequence, and the activated carbon injector is also connected to a bag dust collector.
[0017] The present invention has the following beneficial effects: (1) This method uses two-stage microwave pyrolysis methods, low-temperature pyrolysis and high-temperature pyrolysis, to control the pyrolysis temperature respectively, which not only reduces the generation of toxic waste gas and protects the ecological environment; but also realizes the complete purification and utilization of waste salt, thereby improving the pyrolysis efficiency.
[0018] (2) The rapid cooling treatment of high-temperature decomposition waste gas can shorten the time that the high-temperature decomposition waste gas is in the range of 200-500℃, reduce the secondary generation of dioxin waste gas, and at the same time recover heat and reduce the energy consumption of waste gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Figure 1 A schematic diagram of the structure of a system for treating waste salt from polycarbonate production provided in an embodiment of the present application; Symbols represent: 1-storage tank, 2-conveyor, 3-low-temperature pyrolysis device, 4-high-temperature pyrolysis device, 5-low-temperature induced draft fan, 6-activated carbon ejector, 7-bag dust collector, 8-high-temperature induced draft fan, 9-quencher, 10-demister. DETAILED DESCRIPTION
[0020] The technical solution of the present invention is further explained and illustrated by means of specific embodiments below.
[0021] Example 1 The present application provides a method for treating waste salt from polycarbonate production, the method comprising: S101: Store the waste salt from the production of polycarbonate in a sealed storage tank filled with nitrogen and maintain a slightly positive pressure of 6.9 kPa. Start the conveyor to transport the waste salt from the production of polycarbonate to the low-temperature pyrolysis device. At a temperature of 150°C and a pressure of 2.0 kPa, the waste salt from the production of polycarbonate is thermally decomposed in the low-temperature pyrolysis device for 5 minutes while being transported to obtain treated salt and low-temperature decomposition waste gas. Among them, the low-temperature decomposition waste gas is introduced into the activated carbon injector through a low-temperature induced draft fan, and after being adsorbed by the activated carbon, it is sent to the bag filter for dust removal and then discharged in compliance with the emission standards.
[0022] S102: The treated salt is transported to a high-temperature pyrolysis device, and the treated salt is thermally decomposed for 5 minutes at a temperature of 550°C and a pressure of 2.0 kPa to obtain solid sodium chloride salt and high-temperature decomposition waste gas. The high-temperature decomposition waste gas is introduced into a quenching tower through a high-temperature induced draft fan and rapidly cooled to 190°C, then defogged by a demister, and then adsorbed by activated carbon in an activated carbon injector and dusted by a bag filter before being discharged in compliance with the emission standards.
[0023] Example 2 The present application provides a method for treating waste salt from polycarbonate production, the method comprising: S201: Store the waste salt from the production of polycarbonate in a sealed storage tank filled with nitrogen and maintain a slightly positive pressure of 6.5kPa. Start the conveyor to transport the waste salt from the production of polycarbonate to the low-temperature pyrolysis device. At a temperature of 190°C and a pressure of -1.5kPa, the waste salt from the production of polycarbonate is thermally decomposed in the low-temperature pyrolysis device for 10 minutes while being transported to obtain treated salt and low-temperature decomposition waste gas. Among them, the low-temperature decomposition waste gas is introduced into the activated carbon injector through a low-temperature induced draft fan, and after being adsorbed by the activated carbon, it is sent to the bag filter for dust removal and then discharged in compliance with the emission standards.
[0024] S202: The treated salt is transported to the high-temperature pyrolysis device, and the treated salt is thermally decomposed for 10 minutes at a temperature of 600°C and a pressure of -1.5kPa to obtain solid sodium chloride salt and high-temperature decomposition waste gas. Among them, the high-temperature decomposition waste gas is introduced into the quenching tower through a high-temperature induced draft fan and rapidly cooled to 180°C, and then defogged by a demister, and then adsorbed by activated carbon in an activated carbon injector and dusted by a bag filter before being discharged in compliance with the emission standards.
[0025] Example 3 The present application provides a method for treating waste salt from polycarbonate production, the method comprising: S301: Store the waste salt from the production of polycarbonate in a sealed storage tank filled with nitrogen and maintain a slightly positive pressure of 6.0 kPa. Start the conveyor to transport the waste salt from the production of polycarbonate to the low-temperature pyrolysis device. At a temperature of 170°C and a pressure of -1.0 kPa, the waste salt from the production of polycarbonate is thermally decomposed in the low-temperature pyrolysis device for 8 minutes while being transported to obtain treated salt and low-temperature decomposition waste gas. Among them, the low-temperature decomposition waste gas is introduced into the activated carbon injector through a low-temperature induced draft fan, and after being adsorbed by the activated carbon, it is sent to the bag filter for dust removal and then discharged in compliance with the emission standards.
[0026] S302: The treated salt is transported to the high-temperature pyrolysis device, and the treated salt is thermally decomposed for 8 minutes at a temperature of 580°C and a pressure of -0.8kPa to obtain solid sodium chloride salt and high-temperature decomposition waste gas. Among them, the high-temperature decomposition waste gas is introduced into the quenching tower through a high-temperature induced draft fan and rapidly cooled to 150°C, and then defogged by a demister, and then adsorbed by activated carbon in an activated carbon injector and dusted by a bag filter before being discharged in compliance with the emission standards.
[0027] Example 4 The present application provides a system for treating waste salt from polycarbonate production, the system comprising: a storage tank 1, a conveyor 2, a low-temperature pyrolysis device 3 and a high-temperature pyrolysis device 4 which are connected in sequence. The low-temperature pyrolysis device 3 is connected to an activated carbon injector 6 via a low-temperature induced draft fan 5, and the high-temperature pyrolysis device 4 is connected to the activated carbon injector 6 via a high-temperature induced draft fan 8, a quencher 9 and a demister 10 in sequence. The activated carbon injector 6 is also connected to a bag filter 7, as shown in the attached Figure 1 shown.
[0028] Specifically, the storage tank 1 is used for sealed storage of waste salt from the production of polycarbonate, and the storage tank 1 is filled with nitrogen to maintain a slightly positive pressure state of less than or equal to 6.9 kPa, so as to facilitate the smooth transportation of waste salt from the production of polycarbonate.
[0029] The conveyor 2 is used to transport the polycarbonate production waste salt stored in the storage tank 1 to the low-temperature pyrolysis device 3.
[0030] The low-temperature pyrolysis device 3 uses a microwave generator installed inside to perform low-temperature pyrolysis on the waste salt produced by polycarbonate production, so that most of the volatile organic matter in the waste salt produced by polycarbonate production is pyrolyzed to form low-temperature decomposition waste gas. The low-temperature decomposition waste gas is introduced into the activated carbon injector 6 through the low-temperature induced draft fan 5, and after being adsorbed by the activated carbon, it is sent to the bag filter 7 for dust removal and then discharged in compliance with the standards.
[0031] The high-temperature pyrolysis device 4 uses a microwave generator installed inside to perform high-temperature thermal decomposition on the waste salt from the polycarbonate production after the low-temperature pyrolysis device 3, so that most of the non-volatile organic matter in the waste salt from the polycarbonate production is thermally resolved to form high-temperature decomposition waste gas, and the decomposed treated salt forms solid sodium chloride salt. The high-temperature decomposition waste gas is introduced into the quenching tower 9 through the high-temperature induced draft fan 8 for rapid cooling treatment, so that the temperature of the high-temperature decomposition waste gas is reduced to below 200°C, shortening the time of the high-temperature decomposition waste gas in the range of 200-500°C, reducing the secondary generation of dioxin waste gas, and recovering heat at the same time. The high-temperature decomposition waste gas after rapid cooling is defogged by the demister 10, and then passes through the activated carbon adsorption in the activated carbon injector 6 and the bag dust collector 7 for dust removal before reaching the emission standard.
[0032] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A method for treating waste salt from polycarbonate production, characterized in that: include: The sealed, nitrogen-filled waste salt from polycarbonate production is transported to a low-temperature pyrolysis device, and subjected to microwave heating treatment at a temperature of 150-190° C. for 5-10 minutes to obtain treated salt and low-temperature decomposition waste gas; The treated salt is transported to a high-temperature pyrolysis device and subjected to microwave heating treatment at a temperature of 550-600° C. for 5-10 minutes to obtain solid sodium chloride salt and high-temperature decomposition waste gas.
2. The method for treating waste salt produced by polycarbonate production according to claim 1, characterized in that: The low-temperature decomposition waste gas is discharged after being dust-removed by activated carbon and bag filters.
3. The method for treating waste salt produced by polycarbonate production according to claim 1, characterized in that: The high-temperature decomposition waste gas is rapidly cooled to below 200° C. and then discharged after being removed by a demister, activated carbon and bag dust collector.
4. The method for treating waste salt produced by polycarbonate production according to claim 1, characterized in that: The pressures in the low-temperature pyrolysis device and the high-temperature pyrolysis device are both -1.5-2.0 kPa.
5. The method for treating waste salt produced by polycarbonate production according to claim 1, characterized in that: The storage pressure of the waste salt produced by polycarbonate is less than or equal to 6.9 kPa.
6. A system for treating waste salt from polycarbonate production, characterized in that: include: A storage tank (1), a conveyor (2), a low-temperature pyrolysis device (3) and a high-temperature pyrolysis device (4) are sequentially connected, wherein the low-temperature pyrolysis device (3) is connected to an activated carbon injector (6) via a low-temperature induced draft fan (5), and the high-temperature pyrolysis device (4) is sequentially connected to the activated carbon injector (6) via a high-temperature induced draft fan (8), a quencher (9) and a demister (10), and the activated carbon injector (6) is also connected to a bag filter (7).