Waste plastic resourceful treatment method and equipment

Abstract

The invention relates to a waste plastic resourceful treatment method and equipment. The method comprises the following steps: screening, identifying and preliminarily sorting the waste plastics; a nozzle of an air compressor is used for emitting compressed air, and the plastics are sequentially separated in a segmented mode according to different types; the sorted single-material plastic is subjected to briquetting, and multiple layers of plastic are subjected to crushing decomposition and preliminary cleaning; the multiple layers of small plastic blocks are treated through supercritical carbon dioxide, rapid volume expansion of the plastic layers is triggered, and the subsequent extraction efficiency is improved; a specific solvent is used for selectively dissolving and precipitating different polymer layers in the multi-layer plastic in sequence, so that separation and recovery of the multi-layer plastic are realized. Through the innovative technological process and equipment design, different polymer components in the multi-layer plastic can be effectively separated, the method has the characteristics of being good in separation effect, high in resource recovery rate, free of secondary pollution and the like, and the resourceful treatment level of the waste plastic is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of waste plastics, and specifically to a method and equipment for the resource treatment of waste plastics. Background Technique

[0002] The recycling and treatment of waste plastics is a key topic at present. At this stage, common treatment methods include manual sorting, crushing, and cleaning and separation, etc. Although manual sorting has good results, it is inefficient and has high labor costs; while existing automated sorting technologies, such as electrostatic, wind force, optical sorting, density sorting, and flotation, etc., each have limitations. Some can only work for specific types of plastics, or are difficult to adapt to complex plastic compositions. The patent CN102717451 B proposes a method and equipment for the resource treatment of waste plastics, which mainly realizes the treatment of waste plastics through two steps of crushing and sorting and cleaning and separation. Specifically, the crushing and sorting process of this patent successively includes manual sorting, primary crushing, magnetic separation, and secondary crushing, aiming to remove impurities in waste plastics and classify plastics; while the cleaning and separation process is based on the principle of density sorting, using two liquids with different densities of water and brine to separate the components of waste plastics. However, although this patent has improved the recycling efficiency and quality of waste plastics to a certain extent, there are still obvious limitations when facing the separation and recycling of multi-layer plastics.

[0003] However, the patent CN102717451 B mainly has the following defects: First, it cannot achieve the efficient separation of multi-layer plastics. For complex-structured materials such as multi-layer plastics, traditional density sorting methods are difficult to effectively separate different polymer layers, resulting in low purity of the recycled plastics and being difficult to meet the requirements of high-quality applications. Second, the existing technology has limited ability to treat additives, pigments, etc. in plastics, and the existence of these impurities further affects the performance and reuse range of the recycled plastics. In addition, in the process of plastic crushing and cleaning in the existing technology, the fine treatment of plastics is insufficient, which is easy to cause excessive crushing or insufficient cleaning of plastics, affecting the subsequent recycling effect. Summary of the Invention

[0004] (1) Technical Problems to be Solved

[0005] In view of the deficiencies of the existing technology, the present invention provides a method and equipment for the resource treatment of waste plastics, and solves the problems raised in the above background technique.

[0006] (2) Technical Solutions

[0007] To achieve the above objectives, the present invention is realized through the following technical solutions: A method and equipment for the resource treatment of waste plastics, including the following steps;

[0008] Step 1: Put the recycled waste plastics into a large rotary screen for screening, so that the waste plastics are classified according to size, and different plastics are discharged through at least three different material flows. After separating the materials according to size, the subsequent sorting process will be easier;

[0009] Step 2: Use an infrared imaging system to identify and scan the plastics, and analyze the characteristic peaks of the infrared spectrum of the sample plastics to determine their main polymer components, as well as secondary polymers, fillers, additives and other auxiliary components. During the analysis, the infrared spectrum of the sample plastic can be compared and analyzed with the infrared spectrum of known plastic samples and other reference substances, and compared and analyzed in combination with the spectra in the retrieval database to determine the type of plastic. The air compressor emits compressed air through the nozzle to separate the plastics in different categories, so that different categories of plastics are exported in segments, and the exported material flow is manually sorted to sort out plastics other than the mixture of plastics and non-recyclable waste;

[0010] Step 3: briquetting the sorted single-material plastics for secondary processing as secondary raw materials, crushing and decomposing the sorted multi-layer plastics into small plastic pieces, and preliminarily cleaning the small plastic pieces;

[0011] Step 4: Place the preliminarily cleaned multilayer plastic pieces into a high-pressure container, seal the container, heat and pressurize the container until the carbon dioxide reaches a supercritical state for a period of time, then quickly depressurize the sealed container and filter the filter residue;

[0012] Step 5. Place the filtered residue into a container filled with cyclohexane and stir at room temperature for 2 hours to fully dissolve the PE layer. Use a filtering device to separate the dissolved PE solution from the undissolved plastic. Slowly add ethanol as a non-solvent to the PE solution while stirring. Ethanol and cyclohexane are immiscible, which will reduce the solubility of PE in the solution and cause it to precipitate. Continue stirring for 30 minutes to ensure that PE is completely precipitated, and collect the precipitated PE by centrifugation or filtration. Wash the PE precipitate with ethanol to remove residual cyclohexane and other impurities. Dry the washed PE naturally in a fume hood or dry it at low temperature to obtain pure PE recyclate;

[0013] Step Six: Put the small pieces into a container filled with DMF, stir at 60 °C for 3 hours to fully dissolve EVOH, filter out the undissolved plastics to be processed, slowly add water as a non-solvent to the DMF solution containing EVOH while stirring. Water will be miscible with DMF but will reduce the solubility of EVOH, causing EVOH to precipitate. After stirring for 30 minutes, let it stand for a period of time to allow EVOH to completely precipitate. Collect the EVOH precipitate by centrifugation or filtration, wash the precipitate with deionized water to remove residual DMF and other impurities, and dry it naturally in a fume hood or in a low-temperature dryer to obtain pure EVOH recovery material;

[0014] Step Seven: Put the small pieces of the PET layer obtained after filtration into a container filled with ethyl acetate, stir at room temperature for 2 hours to fully dissolve PET, and filter out the undissolved impurities. Slowly add water as a non-solvent to the ethyl acetate solution of PET while stirring. Ethyl acetate has good solubility for PET, and water will reduce the solubility of PET in the solution, causing it to precipitate. Continue stirring for 30 minutes to ensure complete precipitation of PET, and collect the PET precipitate by centrifugation or filtration. Wash the PET precipitate with deionized water to remove residual ethyl acetate and other impurities. After drying, obtain pure PET recovery material.

[0015] Preferably, an air separator is provided in each material flow in Step One, and the air separator blows compressed air towards the foil in the recycled plastics.

[0016] Preferably, in Step Three, the plastics and non-recyclable waste are used for energy recovery incineration, and the heat obtained from incineration can provide energy for the recovery of various extraction solutions for repeated use.

[0017] Preferably, the pressure in the high-pressure vessel in Step Four is set to exceed 7.4 - 8.2 MPa, and the temperature is maintained at 30 °C - 50 °C to reach the supercritical state. In the supercritical state, carbon dioxide rapidly penetrates into the plastic layer and causes the plastic layer to swell. This process usually needs to be maintained for a certain period of time (such as 3 hours) to ensure sufficient swelling and separation. In addition, supercritical carbon dioxide can also extract additives and pigments from the plastics, and the additives and pigments can be recovered by further reducing the pressure or temperature of the high-pressure vessel.

[0018] Preferably, the rapid pressure relief in Step Four is to reduce the pressure in the high-pressure vessel by more than 50% within 30 seconds, triggering a rapid expansion of the volume of the plastic layer, enabling pre-separation between layers and improving the subsequent extraction efficiency.

[0019] Preferably, Step Five also includes recovering cyclohexane and ethanol by distillation, Step Six also includes recovering DMF and water by distillation, and Step Seven also includes recovering ethyl acetate and water by distillation.

[0020] A waste plastic resource treatment device, which is applied to the above-mentioned waste plastic resource treatment method, includes: a large rotary sieve, an infrared imaging system, an air compressor, a plurality of air separators, an artificial sorting platform, a briquetting device, a crushing and cleaning device, a high-pressure vessel, a plurality of stirring containers and corresponding filtering devices, and a centrifugal separation device;

[0021] Among them, the large rotary sieve is used to receive and screen waste plastics, and export plastics of different sizes through at least three different material flows;

[0022] The infrared imaging system cooperates with the air compressor to emit compressed air through a nozzle to identify and segment-separate plastics;

[0023] The artificial sorting platform is arranged at the material flow export end for manually sorting plastics other than the sorted mixture;

[0024] The briquetting device is used to briquette plastics of a single material;

[0025] The crushing and cleaning device is responsible for crushing and decomposing multi-layer plastics and performing preliminary cleaning;

[0026] The high-pressure vessel is used for sealing, heating and pressurizing to make carbon dioxide reach the supercritical state and perform a filtering operation on the filter residue;

[0027] Each of the stirring containers is respectively used to load corresponding solvents such as cyclohexane, DMF, ethyl acetate, etc., and cooperate with a temperature control and a stirring device to achieve the dissolution and separation of different plastic components. The corresponding filtering device and centrifugal separation device are used to collect the precipitated plastic recyclables.

[0028] Preferably, the waste plastic resource treatment device is also provided with an energy recovery incineration device, which is connected to the artificial sorting platform and is used to treat the sorted plastics and non-recyclable wastes, perform energy recovery incineration on them, and the generated heat can provide energy for each extraction solution recovery process through an energy conversion device to achieve the recycling of energy; at the same time, the various treatment devices are coordinately controlled through an automatic control system to ensure the orderly and efficient operation of the entire waste plastic resource treatment process, and monitoring sensors are arranged at key treatment links to monitor the treatment parameters in real time and feedback them to the control system, so as to adjust the equipment operation state in time and ensure the quality and efficiency of plastic recycling.

[0029] (III) Beneficial effects

[0030] The present invention provides a waste plastic resource treatment method and device, which have the following beneficial effects:

[0031] 1. Through steps such as multi-stage sorting, crushing and cleaning, supercritical carbon dioxide treatment, and solvent extraction, the present invention realizes the efficient resource treatment of waste plastics. The combination of a rotary sieve and an infrared imaging system, together with an air compressor nozzle, accurately separates plastics of different sizes and categories. Manual sorting removes impurities with high precision. Supercritical carbon dioxide treatment promotes pre-separation between plastic layers, extracts additives and pigments, and improves the separation effect. Subsequently, solvent extraction recovers high-purity PE, EVOH, and PET, which can be directly used in the production of new plastic products, improving the recycling rate of waste plastic resources, reducing plastic waste pollution, saving petrochemical resources, and bringing significant environmental and economic benefits.

[0032] 2. The treatment process of the present invention realizes resource recycling and pollutant reduction. Non-recyclable waste is incinerated for energy recovery, and the heat is used for the recovery of extraction solvents, achieving efficient energy utilization and reducing carbon emissions. The extraction solvent is recovered and reused through distillation, reducing VOCs emissions and air pollution. The entire treatment process is carried out in closed equipment to avoid pollutant leakage, minimize the negative impact on the environment to the greatest extent, improve the current situation of plastic waste management, alleviate the plastic pollution problem, promote environmental sustainable development, and contribute to the construction of a resource-saving and environment-friendly society. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of waste plastic separation for a waste plastic resource treatment method in the present invention;

[0034] Figure 2 It is a schematic diagram of multi-layer plastic separation for a waste plastic resource treatment method in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] Example 1:

[0037] As Figure 1-2 shown, the embodiment of the present invention provides a waste plastic resource treatment method for treating a batch of waste plastics mainly composed of multi-layer plastic packaging materials.

[0038] The specific steps are as follows: Put the recycled waste plastics into a large rotary sieve. The rotary sieve is provided with sieves of different pore sizes to classify the waste plastics according to their sizes, and the plastics of different sizes are respectively led out through three different material flows. An air separator is set in each material flow. The nozzle of the air separator is aligned with the direction of the material flow. When the infrared imaging system identifies the type of plastic, the air compressor emits compressed air through the nozzle to blow out light impurities such as foil paper in the plastic, realizing preliminary separation.

[0039] The plastics are identified and scanned by the infrared imaging system, and the air compressor emits compressed air through the nozzle to sequentially and segmentally separate the plastics according to different categories, so that plastics of different categories are led out in segments. Manually sort the led-out material flows, sort the plastics other than the mixture composed of plastics and non-recyclable wastes, and the non-recyclable wastes are used for energy recovery incineration.

[0040] Press the sorted plastics of a single material into blocks for secondary processing as secondary raw materials. Crush and decompose the sorted multi-layer plastics into small plastic pieces, and conduct preliminary cleaning on the small plastic pieces.

[0041] Put the preliminarily cleaned small multi-layer plastic pieces into a high-pressure container, seal the container, heat and pressurize it to a pressure exceeding 7.4 - 8.2 MPa, and keep the temperature at 30°C - 50°C to make carbon dioxide reach the supercritical state and maintain it for a period of time. Quickly depressurize the sealed container (reduce the pressure in the high-pressure container by more than 50% within 30 seconds), causing the volume of the plastic layer to expand rapidly, and filter the filter residue.

[0042] Put the filtered filter residue into a container filled with cyclohexane, stir for 2 hours at room temperature to fully dissolve the PE layer, use a filtering device to separate the dissolved PE solution from the undissolved plastics; slowly add ethanol as a non-solvent to the PE solution while stirring for 30 minutes, and collect the precipitated PE by centrifugation or filtration. Wash the PE precipitate with ethanol to remove the residual cyclohexane and other impurities, and obtain pure PE recovery after drying.

[0043] Put the undissolved plastics into a container filled with DMF, stir at 60°C for 3 hours to fully dissolve the EVOH, filter the undissolved plastics to be treated, slowly add water as a non-solvent to the DMF solution containing EVOH while stirring, after stirring for 30 minutes, let it stand for a period of time, and collect the precipitated EVOH by centrifugation or filtration. Wash the EVOH precipitate with deionized water to remove the residual DMF and other impurities, and obtain pure EVOH recovery after drying.

[0044] Put the undissolved plastic to be processed obtained after filtration into a container filled with ethyl acetate, stir at room temperature for 2 hours to fully dissolve the PET, and filter the undissolved impurities. Slowly add water as a non-solvent to the ethyl acetate solution of PET while stirring for 30 minutes, and collect the precipitated PET by centrifugation or filtration. Wash the PET precipitate with deionized water to remove the residual ethyl acetate and other impurities, and obtain pure PET recyclate after drying. Recover cyclohexane and ethanol, DMF and water, and ethyl acetate and water by distillation to realize the recycling of solvents.

[0045] Example 2:

[0046] Use the waste plastic resource treatment equipment of the present invention to treat a batch of waste plastics mainly composed of multi-layer plastic packaging materials.

[0047] The specific steps are as follows:

[0048] Put the recycled waste plastics into a large rotary sieve for screening, classify the plastics into three levels of large, medium and small according to the size, and export them through three different material flows respectively. An air separator is set in each material flow. After the infrared imaging system identifies the plastic category, the air compressor emits compressed air through the nozzle to blow out impurities such as foil paper in the plastics to complete the preliminary separation.

[0049] Identify and scan the plastics through the infrared imaging system, the air compressor emits compressed air through the nozzle, separate the plastics in segments in sequence according to different categories, and export the plastics of different categories in segments. Manually sort the exported material flows to sort out the substances other than plastics and non-recyclable wastes, and the non-recyclable wastes are used for energy recovery incineration.

[0050] Press the sorted plastics of a single material into blocks as secondary raw materials. Crush and decompose the sorted multi-layer plastics into small pieces and conduct preliminary cleaning.

[0051] Put the small pieces of multi-layer plastics after preliminary cleaning into a high-pressure container, seal the container, heat and pressurize it to a pressure exceeding 7.4 - 8.2 MPa, and keep the temperature at 30°C - 50°C to make carbon dioxide reach the supercritical state and maintain it for a certain time. After rapid depressurization, filter the filter residue.

[0052] Put the filtered filter residue into a container filled with cyclohexane, stir for 2 hours to dissolve the PE layer, add ethanol to the PE solution after separation, stir for 30 minutes, and collect the precipitated PE and wash and dry it.

[0053] Put the undissolved plastics into a container filled with DMF, stir at 60°C for 3 hours to dissolve the EVOH, filter, add water to the solution, stir for 30 minutes and then let it stand, and collect the precipitated EVOH and wash and dry it.

[0054] Put the undissolved plastic to be processed into a container filled with ethyl acetate, stir for 2 hours at room temperature to dissolve PET, add water to the solution after filtration, stir for 30 minutes, collect the precipitated PET and wash and dry it. Recover the solvents in each step by distillation to achieve recycling.

[0055] Example III

[0056] Use the waste plastic resource treatment equipment of the present invention to process a batch of mixtures containing various types of waste plastics. The specific steps are as follows:

[0057] Put the recycled waste plastics into a large rotary sieve, screen them according to the size, and different-sized plastics are led out through three different material flows. An air separator is set in each material flow. After the infrared imaging system identifies the plastics, the air compressor emits compressed air through the nozzle to blow out impurities such as foil paper in the plastics.

[0058] Identify and scan the plastics through the infrared imaging system, the air compressor emits compressed air through the nozzle, separate the plastics into segments in sequence according to different categories, and lead out different categories of plastics. Manually sort the led-out material flows, remove substances other than plastics and non-recyclable wastes, and use the non-recyclable wastes for energy recovery incineration.

[0059] Press the sorted plastics of a single material into blocks as secondary raw materials. Crush and decompose the sorted multi-layer plastics into small pieces and initially wash to remove surface impurities.

[0060] Put the initially washed small multi-layer plastic pieces into a high-pressure container, seal the container, heat and pressurize to the supercritical state (pressure exceeding 7.4 - 8.2 MPa, temperature above 30 - 50 °C), keep for a period of time and then quickly depressurize to cause the plastic layer to expand, and filter to obtain the filter residue.

[0061] Put the filter residue into a container filled with cyclohexane, stir for 2 hours at room temperature to dissolve the PE layer, add ethanol to the PE solution after separation, stir for 30 minutes, and collect the precipitated PE and wash and dry it.

[0062] Put the undissolved plastics into a container filled with DMF, stir for 3 hours at 60 °C to dissolve EVOH, add water to the solution after filtration, stir for 30 minutes and then let it stand, collect the precipitated EVOH and wash and dry it.

[0063] Put the undissolved plastic to be treated into a container filled with ethyl acetate, stir for 2 hours at room temperature to dissolve PET, add water to the solution after filtration, stir for 30 minutes, collect the precipitated PET and wash and dry it. Recover cyclohexane and ethanol, DMF and water, ethyl acetate and water by distillation to realize the recycling of solvents.

[0064] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recycling waste plastics, characterized in that, It includes the following steps; Step 1: Put the recycled waste plastics into a large rotary sieve for screening, so that the waste plastics are classified according to size, and different plastics are discharged through at least three different material flows; Step 2: Identify and scan the plastics through an infrared imaging system. The air compressor emits compressed air through a nozzle to sequentially separate the plastics in segments according to different categories, so that plastics of different categories are discharged in segments, and manually sort the discharged material flows to sort the plastics other than the mixture composed of plastics and non-recyclable wastes; Step 3: Press the sorted plastics of a single material into blocks for secondary processing as secondary raw materials. Crush and decompose the sorted multi-layer plastics into small plastic pieces, and conduct preliminary cleaning on the small plastic pieces; Step 4: Put the preliminarily cleaned multi-layer plastic pieces into a high-pressure container, seal the container, heat and pressurize it until carbon dioxide reaches the supercritical state for a period of time, then quickly depressurize the sealed container and filter the filter residue; Step 5: Put the filtered filter residue into a container filled with cyclohexane, stir for 2 hours at room temperature, use a filtering device to separate the cyclohexane solution dissolved with PE from the undissolved plastics, then slowly add ethanol as a non-solvent to the cyclohexane solution while stirring, and collect the precipitate by centrifugal separation or filtration after stirring for 30 minutes; Step 6: Put the undissolved plastics filtered in Step 5 into a container filled with DMF, stir at 60 °C for 3 hours, filter the undissolved plastics to be treated, slowly add water as a non-solvent to the DMF solution containing EVOH while stirring, and stir for 30 minutes, then let it stand for a period of time, and collect the precipitate by centrifugation or filtration; Step 7: Put the undissolved plastics to be treated obtained after filtration into a container filled with ethyl acetate, stir at room temperature for 2 hours, and filter the undissolved impurities. Slowly add water as a non-solvent to the ethyl acetate solution of PET while stirring, stir for 30 minutes, and collect the precipitate by centrifugation or filtration.

2. The method for recycling waste plastics according to claim 1, characterized in that: In Step 1, an air separator is provided in each material flow, and the air separator blows compressed air towards the foil paper in the recycled plastics.

3. The method for recycling waste plastics according to claim 1, characterized in that: In Step 3, the plastics and non-recyclable wastes are used for energy recovery incineration.

4. A method for recycling waste plastics as described in claim 1, characterized in that: In Step 4, the pressure in the high-pressure container is set to 7.4 - 8.2 MPa, and the temperature is maintained at 30 °C - 50 °C to reach the supercritical state.

5. A method for recycling waste plastics as claimed in claim 1, characterized in that: The rapid depressurization in Step 4 is to reduce the pressure in the high-pressure container by more than 50% within 30 seconds, triggering a rapid expansion of the volume of the plastic layer.

6. The method for recycling waste plastics according to claim 1, characterized in that: Step 5 further includes recovering cyclohexane and ethanol by distillation. Step 6 further includes recovering DMF and water by distillation. Step 7 further includes recovering ethyl acetate and water by distillation.

7. A waste plastic resource treatment device, which is applied to the waste plastic resource treatment method described in claims 1-6, and is characterized in that, It includes a large rotary sieve, an infrared imaging system, an air compressor, multiple air separators, a manual sorting platform, a briquetting device, a crushing and cleaning device, a high-pressure container, multiple stirring containers and corresponding filtering devices, a centrifugal separation device; Among them, the large rotary sieve is used to receive and screen waste plastics, and discharge plastics of different sizes through at least three different material flows; The infrared imaging system cooperates with an air compressor to emit compressed air through a nozzle to identify and segment and separate plastics; The manual sorting platform is arranged at the material flow outlet end and is used for manually sorting plastics other than the sorted mixture; The briquetting device is used for briquetting single-material plastics; The crushing and cleaning device is responsible for crushing and decomposing multi-layer plastics and performing preliminary cleaning; The high-pressure vessel is used for sealing, heating and pressurizing to make carbon dioxide reach the supercritical state and performing a filtering operation on the filter residue; Each stirring container is respectively used for loading corresponding solvents such as cyclohexane, DMF, ethyl acetate, etc., and cooperates with a temperature control and stirring device to realize the dissolution and separation of different plastic components. The corresponding filtering device and centrifugal separation device are used for collecting the precipitated plastic recyclables.

8. A waste plastic resource treatment device according to claim 7, characterized in that: The waste plastic resource treatment equipment is also provided with an energy recovery incineration device, which is connected to the manual sorting platform and is used for treating the sorted plastics and non-recyclable wastes, performing energy recovery incineration on them, and the generated heat can provide energy for each extraction solution recovery process through an energy conversion device; meanwhile, each treatment device is coordinately controlled through an automatic control system, and monitoring sensors are arranged at key treatment links for real-time monitoring of treatment parameters and feedback to the control system.

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