Use method for efficiently pyrolyzing and dechlorinating waste plastics

Abstract

The invention discloses a use method for efficient waste plastic pyrolysis and dechlorination, which comprises the following steps: cleaning, blow-drying and crushing waste plastic, mixing with a catalyst, performing low-temperature pyrolysis in an oxygen-free environment, performing gas-liquid separation, cyclone dust removal and high-temperature dechlorination adsorbent treatment, and finally performing deep denitration and dechlorination by using a spray chamber. Wherein the temperature, the pressure, the heating rate and the heating time are strictly controlled in the pyrolysis process, and it is ensured that pyrolysis oil and gas are efficiently produced; in the dechlorination step, modified HZSM-5 zeolite and a spraying chamber technology are adopted, and chlorine and nitrogen oxides in pyrolysis gas are effectively removed through gas-liquid-solid three-phase contact, so that preparation of a high-purity product is realized. Experimental results show that the method can remarkably improve the dechlorination efficiency, the dechlorination rate reaches 96.18%, and an efficient and environment-friendly solution is provided for resource utilization of the waste plastics; according to the method, the economic benefit of waste plastic treatment is improved, and sustainable development of environmental protection and resource recycling is promoted.

Description

Technical Field

[0001] The invention relates to the technical field of pyrolysis and dechlorination of waste plastics, and in particular to a method for efficiently pyrolyzing and dechlorinating waste plastics. Background Art

[0002] As global attention to plastic pollution continues to rise, the treatment and recycling of waste plastics has become an important issue in the field of environmental protection. The essence of plastic pollution is the environmental leakage caused by improper management of plastic waste. Especially in the context of rapid growth in plastic production and consumption, improper treatment of waste plastics not only causes a huge waste of resources, but also poses a considerable threat to the ecological environment.

[0003] In the process of plastic waste treatment, the treatment of chlorine-containing waste plastics is particularly difficult. Due to the presence of chlorine, chlorine-containing waste plastics may produce toxic and harmful chlorides during the recycling and treatment process, posing a threat to the environment and human health.

[0004] At present, the dechlorination technology of waste plastics is mainly divided into three types: chemical method, physical method and biological method. Chemical method removes chlorides through chemical reactions, such as alkali treatment method, catalytic hydrogenolysis method, etc.; physical method achieves dechlorination through high temperature pyrolysis and other means; biological method uses the biodegradation of microorganisms to remove chlorides. Although a variety of dechlorination technologies have been proposed and studied, their industrial application still faces challenges such as technology, cost and market demand.

[0005] In practical applications, a single dechlorination technology is often difficult to meet production requirements, so it is often necessary to adopt a combination of dechlorination technologies to combine the advantages of different technologies to improve dechlorination efficiency. In addition, dechlorination of pyrolysis oil is also an important direction for the development of technology to improve the dechlorination effect of waste plastics. By improving the quality and added value of pyrolysis oil, its subsequent processing and application range can be expanded.

[0006] Therefore, in order to solve the shortcomings of the above problems, a method for efficiently pyrolyzing and dechlorinating waste plastics is proposed. Summary of the invention

[0007] The present invention overcomes the shortcomings of the prior art and provides a method for efficiently pyrolyzing and dechlorinating waste plastics.

[0008] To achieve the above object, the technical solution adopted by the present invention is: a method for efficiently pyrolyzing and dechlorinating waste plastics, comprising the following steps:

[0009] S1: Wash the waste plastics, use a blower to dry the waste plastics after washing, and crush the waste plastics into waste plastic powder;

[0010] S2: mixing waste plastic powder with a catalyst;

[0011] S3: low temperature pyrolysis in an oxygen-free environment, the temperature range of low temperature pyrolysis is 350-480°C;

[0012] S4: Separating the gas, liquid and solid residue produced by pyrolysis;

[0013] S5: Use cyclone dust removal and high temperature dechlorination adsorbent particles to remove dust and chlorine from pyrolysis gas;

[0014] S6: The pyrolysis gas treated in S5 is passed through a spray chamber for flue gas denitrification and dechlorination treatment. A number of turbulent balls are arranged in the spray chamber, and the deep removal of nitrogen oxides and chlorine compounds in the flue gas is achieved through gas-liquid-solid three-phase contact.

[0015] In a preferred embodiment of the present invention, in S1, the cleaning time ranges from 20 to 30 minutes, the drying time ranges from 10 to 20 minutes, the particle size of the waste plastic powder ranges from 200 to 300 μm, and the crushing time ranges from 10 to 20 minutes.

[0016] In a preferred embodiment of the present invention, in S2, the mixing time range of the waste plastic powder and the catalyst is 20-30 min, the mass ratio of the waste plastic powder to the catalyst is 1:1, the material of the waste plastic includes but is not limited to polyethylene, polypropylene, polystyrene, and the catalyst is Fe-Zr / ZSM-5.

[0017] In a preferred embodiment of the present invention, in S3, during low-temperature pyrolysis, the pyrolysis pressure is maintained in the range of 0.1-0.5 atm, the heating rate is in the range of 25-30°C / min, and the pyrolysis reaction time is in the range of 30-60 min.

[0018] In a preferred embodiment of the present invention, in S4, the gas, liquid and solid residue generated by pyrolysis are separated by a gas-liquid separator; the pyrolysis gas is converted into pyrolysis oil through cooling and condensation, and the solid residue is collected for subsequent processing or utilization.

[0019] In a preferred embodiment of the present invention, in S5, the high temperature dechlorination adsorbent particles are modified HZSM-5 zeolite.

[0020] In a preferred embodiment of the present invention, in S6, the material of the turbulent ball includes but is not limited to PVC, PE, PP plastic or stainless steel hollow ball, and the spray liquid is a liquid absorbent containing nitric acid.

[0021] In a preferred embodiment of the present invention, in S6, the height from the nozzle in the spray chamber to the plurality of turbulent balls is 300 mm, so as to ensure that the spray liquid can evenly cover the surface of the turbulent balls.

[0022] In a preferred embodiment of the present invention, in S6, the nozzles in the spray chamber are high-efficiency atomizing nozzles, and the nozzles are arranged in a staggered manner to ensure uniform distribution of the pyrolysis gas in the spray chamber and sufficient mixing with the spray liquid.

[0023] In a preferred embodiment of the present invention, in S6, the nozzle angle in the spray chamber is in the range of 60-120°, the flow rate of the nozzle is in the range of 10-30 L / min, and the spray frequency is in the range of 5-10 times / min.

[0024] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0025] (1) The present invention provides a method for the use of efficient waste plastic pyrolysis and dechlorination, which ensures the purity of the raw materials and the efficiency of the pyrolysis reaction through the steps of washing, drying and crushing. Secondly, the Fe-Zr / ZSM-5 catalyst is mixed with the waste plastic powder, which not only improves the uniformity and efficiency of the pyrolysis reaction, but also significantly improves the selectivity of the product, thereby obtaining higher quality pyrolysis oil and gas products. In addition, through the use of a gas-liquid separator and a cyclone dust collector, the gas, liquid and solid residue generated during the pyrolysis process are effectively separated, the recycling rate of resources is improved, and the generation of waste is reduced, reflecting the concept of resource recycling.

[0026] (2) In the present invention, the deep removal of chlorine compounds in the pyrolysis gas of waste plastics is achieved by combining the modified HZSM-5 zeolite and the spray chamber. In step S5, a dechlorination efficiency of 90% is achieved by high-temperature dechlorination treatment of the modified HZSM-5 zeolite, significantly reducing the chlorine content. In step S6, the dechlorination rate is further increased to 96.18% through further treatment in the spray chamber, close to the level of complete dechlorination. This continuous dechlorination process not only improves the quality of the pyrolysis products of waste plastics, but also reduces pollution to the environment, with significant environmental benefits.

[0027] (3) In the present invention, efficient conversion of waste plastics and output of high-purity pyrolysis products are achieved through optimized operating parameters and process flow. This method not only improves the yield and quality of pyrolysis oil and gas, but also reduces waste generation through resource recycling, which has important economic and environmental benefits. In addition, the effectiveness of the dechlorination method and experimental conditions adopted is verified by experiments, providing a practical solution for the environmentally friendly treatment and resource utilization of waste plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described below in conjunction with the accompanying drawings and embodiments;

[0029] Figure 1 It is a flow chart of a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0030] The present invention will now be further described in detail with reference to the accompanying drawings and embodiments. These drawings are simplified schematic diagrams that only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0031] like Figure 1 As shown, a method for efficiently pyrolyzing and dechlorinating waste plastics comprises the following steps:

[0032] S1: washing the waste plastics for a period of 20-30 minutes, using a blower to dry the waste plastics after washing, the particle size of the waste plastic powder is in the range of 200-300 μm, crushing the waste plastics into waste plastic powder, and the crushing time is in the range of 10-20 minutes;

[0033] S2: mixing the waste plastic powder with the catalyst, wherein the mixing time of the waste plastic powder and the catalyst is in the range of 20-30 minutes, the mass ratio of the waste plastic powder to the catalyst is 1:1, the material of the waste plastic includes but is not limited to polyethylene, polypropylene, and polystyrene, and the catalyst is Fe-Zr / ZSM-5;

[0034] S3: low-temperature pyrolysis is performed in an oxygen-free environment, the temperature range of the low-temperature pyrolysis is 350-480°C, the pyrolysis pressure is maintained in the range of 0.1-0.5atm, the heating rate is in the range of 25-30°C / min, and the pyrolysis reaction time is in the range of 30-60min;

[0035] S4: The gas, liquid and solid residue produced by pyrolysis are separated by a gas-liquid separator. The pyrolysis gas is converted into pyrolysis oil through cooling and condensation, while the solid residue is collected for subsequent treatment or utilization;

[0036] S5: Use cyclone dust removal and high temperature dechlorination adsorbent particles to remove dust and chlorine in the pyrolysis gas. The high temperature dechlorination adsorbent particles are modified HZSM-5 zeolite.

[0037] S6: The pyrolysis gas treated in S5 is passed through a spray chamber for flue gas denitrification and dechlorination treatment. A number of turbulent balls are arranged in the spray chamber. The materials of the turbulent balls include but are not limited to PVC, PE, PP plastics or stainless steel hollow balls. The spray liquid is a liquid absorbent containing nitric acid. Through the three-phase contact of gas, liquid and solid, the deep removal of nitrogen oxides and chlorine compounds in the flue gas is achieved. The height from the nozzle to the turbulent balls in the spray chamber is 300mm, which is used to ensure that the spray liquid can evenly cover the surface of the turbulent balls. The nozzle is a high-efficiency atomizing nozzle, and the nozzle is arranged in a staggered manner to ensure the uniform distribution of the pyrolysis gas in the spray chamber and sufficient mixing with the spray liquid. The spray angle range is 60-120°, the flow rate of the nozzle ranges from 10-30L / min, and the spray frequency ranges from 5-10times / min.

[0038] It should be noted that:

[0039] In S1, there are three key steps: cleaning, drying and crushing. The cleaning process effectively removes impurities and contaminants on the waste plastics, ensures the purity of the raw materials entering the pyrolysis stage, and lays a good foundation for improving the quality of pyrolysis oil and gas products. The subsequent drying step ensures that the waste plastic powder is in a dry state, eliminates the negative impact that moisture may have on the pyrolysis efficiency, and helps maintain the stability of temperature and reaction conditions during the pyrolysis process. Finally, the crushing step converts the waste plastic into powder, significantly increasing the surface area of ​​the raw materials, thereby accelerating the rate of the pyrolysis reaction and improving the efficiency of the entire pyrolysis process;

[0040] In S2, by mixing the waste plastic powder and the catalyst in a 1:1 ratio, the waste plastic powder and the catalyst can be evenly mixed to ensure sufficient contact between the two, which not only improves the uniformity and efficiency of the pyrolysis reaction, but also maximizes the effectiveness of the catalyst through the optimized mass ratio of 1:1, and promotes the chemical reaction in the pyrolysis process. The selected Fe-Zr / ZSM-5 catalyst significantly improves the selectivity of the product by promoting the breaking of specific chemical bonds, and can obtain higher quality pyrolysis oil and gas products;

[0041] In S3, the regulated temperature, pressure, heating rate and time have a decisive influence on the pyrolysis efficiency and product quality. Waste plastics are pyrolyzed in an oxygen-free environment within a temperature range of 350-480°C. This temperature range optimizes the yield and quality of pyrolysis oil and gas133. At the same time, the pyrolysis process is carried out at a pressure of 0.1-0.5atm, which helps to control the reaction rate and improve the purity of the product135. In addition, the heating rate is controlled at 25-30°C / min, while the pyrolysis reaction time is adjusted between 30-60min as needed to ensure the stability of the pyrolysis process and the consistency of the products136. Through these operating parameters, the S3 stage not only improves the pyrolysis efficiency, but also ensures the quality and yield of the pyrolysis products, laying a solid foundation for the subsequent separation and purification steps;

[0042] In S4, the application of the gas-liquid separator effectively and precisely separates the gas, liquid and solid residue produced during the pyrolysis process, which not only improves the efficiency of subsequent treatment, but also facilitates the further processing and application of various products. Secondly, the collection of pyrolysis oil is achieved by cooling and condensing the pyrolysis gas, which not only increases the recycling rate of resources, but also creates conditions for obtaining high-quality pyrolysis oil products. In addition, the collection and utilization of solid residues, converting them into raw materials that can be used in other industrial processes, reduces the generation of waste and embodies the concept of resource recycling;

[0043] In S5, cyclone dust removal uses the principle of centrifugal force to remove dust particles from pyrolysis gas, which not only reduces the wear and blockage of subsequent equipment caused by dust, but also prevents safety accidents that may be caused by dust accumulation. The cyclone dust collector itself has a simple structure, is easy to operate, and is inexpensive, but its dust removal efficiency is not as high as 100%, especially for finer dust particles; secondly, high-temperature dechlorination uses modified HZSM-5 zeolite as an adsorbent to effectively remove chlorine compounds from pyrolysis gas. Modified HZSM-5 zeolite plays an important role in the dechlorination process due to its high activity and special pore structure. The modification of zeolite enhances its adsorption capacity for chlorine compounds, thereby significantly improving the purity of the gas and providing a higher quality purification effect for pyrolysis gas. The S5 stage not only optimizes the quality of pyrolysis gas, but also provides a safer and more reliable process flow for the entire pyrolysis and dechlorination method; through dust removal and dechlorination, the pyrolysis gas is purified, laying a solid foundation for the subsequent spray chamber treatment stage;

[0044] In S6, the turbulent balls in the spray chamber promote the full contact of the three phases of gas, liquid and solid, improve the mass transfer efficiency, and enhance the reaction rate of denitrification and dechlorination; through the selection of liquid absorbent containing nitric acid, it is highly targeted and can effectively remove pollutants in the flue gas. In addition, the staggered arrangement of high-efficiency atomizing nozzles and precise spray parameter control - including spray angles of 60-120°, flow rates of 10-30L / min, and frequencies of 5-10times / min - ensure uniform mixing between pyrolysis gas and spray liquid, further optimizing the treatment efficiency and mass transfer effect of the spray chamber; not only improves the treatment capacity of the spray chamber, but also ensures the deep purification of the flue gas, reflecting the environmental performance and high efficiency of resource utilization of the entire waste plastic pyrolysis and dechlorination method.

[0045] Embodiment 1:

[0046] Prepare the materials:

[0047] Waste plastics: polyethylene;

[0048] Catalyst: Fe-Zr / ZSM-5;

[0049] Ensure that the mass ratio of polyethylene to Fe-Zr / ZSM-5 is 1:1.

[0050] S1: Put the polyethylene into a cleaning tank, add enough water, and carry out a cleaning process for 20 minutes to remove impurities and pollutants; after cleaning, use a blower to blow dry the polyethylene to ensure that the polyethylene powder is dry, and the drying time is 15 minutes; put the dried polyethylene into a pulverizer and crush it into powder with a particle size range of 200-300μm, and the crushing time is 12 minutes.

[0051] S2: Mix the polyethylene powder with the Fe-Zr / ZSM-5 catalyst in a mixer for 25 minutes to ensure that the mixture is uniform.

[0052] S3: Put the mixed polyethylene powder into a pyrolysis reactor, set the temperature to 400°C, the pressure to 0.3atm, the heating rate to 28°C / min, and the pyrolysis reaction time to 45min in an oxygen-free environment.

[0053] S4: After the pyrolysis is completed, the generated gas, liquid and solid residue are separated through a gas-liquid separator, and the pyrolysis oil is collected and cooled and condensed to ensure the quality of the oil.

[0054] S5: The pyrolysis gas is passed through a cyclone dust collector to remove dust particles, and modified HZSM-5 zeolite is used as a high-temperature dechlorination adsorbent to remove chlorine compounds in the pyrolysis gas.

[0055] S6: The pyrolysis gas after dust removal and dechlorination treatment is introduced into the spray chamber. In the spray chamber, a high-efficiency atomizing nozzle is set with a spray angle of 90°, a flow rate of 20L / min, and a frequency of 7times / min. A turbulent ball made of PVC is placed in the spray chamber to ensure that the spray liquid evenly covers the surface of the turbulent ball. A liquid absorbent containing nitric acid is used as the spray liquid to achieve deep removal of nitrogen oxides and chlorine compounds in the flue gas.

[0056] Table 1:

[0057] Chlorine content test: Use silver nitrate titration to test the chlorine content in the experimental procedure;

[0058] The calculation formula of dechlorination rate is as follows:

[0059]

[0060]

[0061] From Table 1 we can see that:

[0062] Step S5: using modified HZSM-5 zeolite as a dechlorinating agent, treating the pyrolysis gas at a temperature of 400° C. and a pressure of 0.3 atm, measuring the chlorine content before and after dechlorination, and calculating a dechlorination rate of 90%.

[0063] Step S6: Based on step S5, a spray chamber is further used for treatment, the nozzle flow rate is set to 20 L / min and the frequency is set to 7 times / min, and a liquid absorbent containing nitric acid is used to measure the chlorine content before and after dechlorination again, and a dechlorination rate of 96.18% is calculated.

[0064] In summary:

[0065] The experiment was conducted in two stages, first using modified HZSM-5 zeolite as a dechlorinating agent in the S5 step, followed by further deep treatment via a spray chamber in the S6 step.

[0066] Step S5: Dechlorination treatment of pyrolysis gas was performed using modified HZSM-5 zeolite at a temperature of 400°C and a pressure of 0.3 atm. The chlorine content was 1000 mg / L before the experiment and decreased to 100 mg / L after the treatment.

[0067] Step S6: Based on S5, the pyrolysis gas is further treated by using a liquid absorbent containing nitric acid through a spray chamber. The nozzle flow rate is set to 20L / min, the frequency is 7 times / min, and the final chlorine content is reduced to 3.82mg / L.

[0068] Analysis of dechlorination effect:

[0069] Step S5: Achieved a dechlorination efficiency of 90%, significantly reduced the chlorine content, and laid a solid foundation for subsequent spray room treatment.

[0070] Step S6: Through deep treatment in the spray chamber, the dechlorination rate is further increased to 96.18%, close to the level of complete dechlorination.

[0071] Through the continuous treatment of the two steps S5 and S6, the dechlorination rate was significantly increased from 90% to 96.18%. This result verified the effectiveness of the dechlorination method and experimental conditions adopted, especially in the S6 step, by optimizing the operating parameters of the spray chamber, a deeper dechlorination effect was achieved.

[0072] The above is based on the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for efficiently pyrolyzing and dechlorinating waste plastics, characterized in that: The following steps are involved: S1: Wash the waste plastics, use a blower to dry the waste plastics after washing, and crush the waste plastics into waste plastic powder; S2: mixing waste plastic powder with a catalyst; S3: low temperature pyrolysis in an oxygen-free environment, the temperature range of low temperature pyrolysis is 350-480°C; S4: Separating the gas, liquid and solid residue produced by pyrolysis; S5: Use cyclone dust removal and high temperature dechlorination adsorbent particles to remove dust and chlorine from pyrolysis gas; S6: The pyrolysis gas treated in S5 is passed through a spray chamber for flue gas denitrification and dechlorination treatment. A number of turbulent balls are arranged in the spray chamber, and the deep removal of nitrogen oxides and chlorine compounds in the flue gas is achieved through gas-liquid-solid three-phase contact.

2. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In S1, the cleaning time ranges from 20 to 30 minutes, the drying time ranges from 10 to 20 minutes, the particle size of the waste plastic powder ranges from 200 to 300 μm, and the crushing time ranges from 10 to 20 minutes.

3. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In S2, the mixing time of the waste plastic powder and the catalyst is in the range of 20-30 min, the mass ratio of the waste plastic powder to the catalyst is 1:1, the material of the waste plastic includes but is not limited to polyethylene, polypropylene, and polystyrene, and the catalyst is Fe-Zr / ZSM-5.

4. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In the S3, during low-temperature pyrolysis, the pyrolysis pressure is maintained in the range of 0.1-0.5 atm, the heating rate is in the range of 25-30° C. / min, and the pyrolysis reaction time is in the range of 30-60 min.

5. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In S4, the gas, liquid and solid residue generated by pyrolysis are separated by a gas-liquid separator; the pyrolysis gas is converted into pyrolysis oil through cooling and condensation, and the solid residue is collected for subsequent treatment or utilization.

6. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In the S5, the high temperature dechlorination adsorbent particles are modified HZSM-5 zeolite.

7. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In S6, the material of the turbulent ball includes but is not limited to PVC, PE, PP plastic or stainless steel hollow ball, and the spray liquid is a liquid absorbent containing nitric acid.

8. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In the S6, the height from the nozzle to the turbulent balls in the spray chamber is 300 mm, which is used to ensure that the spray liquid can evenly cover the surface of the turbulent balls.

9. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In S6, the nozzles in the spray chamber are high-efficiency atomizing nozzles, and the nozzles are arranged in a staggered manner to ensure uniform distribution of the pyrolysis gas in the spray chamber and sufficient mixing with the spray liquid.

10. The method for high-efficiency pyrolysis and dechlorination of waste plastics according to claim 1, characterized in that: In the S6, the nozzle angle in the spray chamber is in the range of 60-120°, the flow rate of the nozzle is in the range of 10-30 L / min, and the spray frequency is in the range of 5-10 times / min.

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