CN112588428A - Method for separating PET and PVC based on low-temperature plasma induced flotation - Google Patents
Method for separating PET and PVC based on low-temperature plasma induced flotation Download PDFInfo
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- CN112588428A CN112588428A CN202011435237.4A CN202011435237A CN112588428A CN 112588428 A CN112588428 A CN 112588428A CN 202011435237 A CN202011435237 A CN 202011435237A CN 112588428 A CN112588428 A CN 112588428A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B03—SEPARATION OF SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS; MAGNETIC OR ELECTROSTATIC SEPARATION OF SOLID MATERIALS FROM SOLID MATERIALS OR FLUIDS; SEPARATION BY HIGH-VOLTAGE ELECTRIC FIELDS
- B03B—SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS
- B03B5/00—Washing granular, powdered or lumpy materials; Wet separating
- B03B5/28—Washing granular, powdered or lumpy materials; Wet separating by sink-float separation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
- B29C71/0081—After-treatment of articles without altering their shape; Apparatus therefor using an electric field, e.g. for electrostatic charging
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Abstract
The invention belongs to the technical field of pollution prevention and recycling of solid wastes, and relates to a method for separating PET and PVC based on low-temperature plasma induced flotation. The method comprises the steps of taking polyvinyl chloride (PVC) and polyethylene terephthalate (PET) with different sources and mass ratios as raw materials, sequentially connecting the raw materials in series through four process links (pretreatment step 1 → plasma contact induction → pretreatment step 2 → flotation unit), discharging the flotation unit, wherein a floating product is the PET, and a sinking tailing is the separated PVC. The method has simple flow, particularly no solvent is added in the plasma contact induction process, no oxidant or additional catalytic agent is used, the method is nontoxic and harmless to the environment, the cost is saved, the secondary pollution of the water body can be effectively reduced, and meanwhile, the method is simple to operate and beneficial to industrial large-scale application.
Description
Technical Field
The invention belongs to the technical field of pollution prevention and recycling of solid wastes, particularly relates to a flotation separation technology, and particularly relates to a method for enhancing flotation separation of PET (polyethylene terephthalate) and PVC (polyvinyl chloride) mixed plastics by utilizing low-temperature plasma induced modification as pretreatment.
Background
Economic and environmental losses caused by waste plastics are increasingly serious, the proportion of the waste plastics in common solid waste streams such as household garbage is continuously increased, and the recycling treatment is widely concerned. Polyethylene terephthalate (PET) and polyvinyl chloride (PVC) are widely used in the disposable packaging industry due to their excellent hot workability and stability, and they have an obvious coexistence relationship in recycled waste and are difficult to separate by manual sorting. The waste PET has high recycling value, material circulation can be realized through simple remolding process treatment, and the regenerated PET can obtain high quality and be repeatedly used for non-food-grade packaging; and the doping of waste PVC in PET can cause the negative problems of main body polymerization cracking, decoloration, embrittlement and the like in the recovery process, and the quality of the regenerated PET is seriously reduced. In addition, the high halogen content (Cl) in PVC has the secondary environmental pollution problems of hydrogen chloride, dioxin and the like in the thermal process of the recovery link. Therefore, how to separate the impurity PVC in an efficient and environment-friendly manner has extremely important practical significance for recycling the PET, and is also a hotspot of the separation research of the mixed plastics at present.
Besides manual sorting, the reported methods for sorting waste plastics also include electrostatic, spectroscopic and hydrocyclone sorting methods, but these methods have defects in application range, cost, sorting efficiency and purity, and are not applied in large-scale industrialization. The flotation technology is a technical means for realizing separation based on floatability difference of fine particle materials, is witnessed in the industrialization degree of the mineral processing industry, and has a plurality of excellent performances such as continuity, high grade, low cost and the like. However, existing researches show that direct flotation of PET and PVC mixed plastics is limited by the close physicochemical properties of the two and the weak selectivity of common inhibitors, and effective separation cannot be achieved, so that a pretreatment unit needs to be matched before flotation, and the difference of floatability of the two is increased by surface modification of similar oxidation type (Fenton or similar Fenton oxidation), so as to achieve subsequent separation. For example, in the existing operation, a large amount of oxidants such as hydrogen peroxide, ferric sulfite, hypochlorous acid, ammonium persulfate and the like need to be used in the pretreatment process, and meanwhile, higher temperature, treatment time or additional catalysts are also needed for activating the oxidants.
Disclosure of Invention
In view of the defects in the prior art, the invention aims to provide a method for separating PET and PVC based on low-temperature plasma induced flotation, so as to solve the problems of high cost, low efficiency and poor environmental protection in the existing separation method.
In order to achieve the technical purpose, the inventor of the invention has diligently researched through a great deal of experimental research, and finally obtains a method for enhancing flotation separation of mixed plastics PET and PVC by using low-temperature plasma induced modification as pretreatment. Specifically, the technical scheme of the invention is summarized as follows:
a method for separating PET and PVC based on low-temperature plasma induced flotation comprises the following steps:
(1) pretreatment step 1: collecting mixed plastics as a feed material, wherein the mixed plastics comprise PET and PVC, cleaning to remove stains, performing coarse crushing, and controlling the feed thickness to be less than or equal to 10mm to finish the sheeting of the feed material;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under atmospheric pressure, wherein the plasma is generated by a corona discharge or radio frequency plasma torch generator in the atmosphere or oxygen or nitrogen atmosphere, and the unit activation energy generated by controlling the induction of the plasma in the process is 12-18 kJ/m2；
(3) A pretreatment step 2: finely grinding the mixed plastic after the plasma contact induction in the step (2), and controlling the equivalent diameter to be 0.5-5 mm (more than 90% by mass) by using a particle size sieve to finish feeding and fine granulation;
(4) a flotation unit: placing the fine granulated mixed plastic obtained in the step (3) into a flotation containerAdding tap water as a solution medium, wherein the solid-to-liquid ratio is as follows in kg: m is3Adding a non-ionic foaming agent according to the ratio of (15-25) to 1, operating for 3-15 min under the condition of air aeration of 150-300L/h, and collecting and separating floating products.
Further preferably, the method for separating PET and PVC based on low-temperature plasma induced flotation is as described above, wherein the mass ratio of PET to PVC in the mixed plastic in the step (1) is (0.43-2.33): 1. the source of the mixed plastic is PET and PVC products commonly found in domestic garbage solid waste streams, such as beverage bottles, preservation boxes, toys, building accessories, packaging materials and the like.
Further preferably, the method for separating PET and PVC based on low temperature plasma induced flotation as described above, wherein the washing in step (1) is performed by: soaking in tap water containing detergent (preferably cleaning powder), stirring, washing with tap water, and separating solid from liquid.
Further preferred is a process for separating PET and PVC based on low temperature plasma induced flotation as described above, wherein the coarse crushing in step (1) controls the feed thickness to be ≤ 6 mm.
Further preferably, the method for separating PET and PVC based on low-temperature plasma induced flotation is as described above, wherein corona discharge is performed in step (2) by using a corona machine, parameters of working electrodes in the corona machine are 500mm in length, 1mm in width and 1.5mm in distance, sinusoidal alternating voltage is 220VAC/50Hz for power supply, maximum output power is 1kW, and maximum linear speed of a feeding roller is 15 m/min.
Further preferably, the method for separating PET and PVC based on low temperature plasma induced flotation as described above, wherein the specific activation energy for controlling the plasma induced generation in the step (2) is 15kJ/m2。
Further preferably, the method for separating PET and PVC based on low-temperature plasma induced flotation is as described above, wherein the refining in the step (3) is ball milling, and the equivalent diameter of the refined material is controlled to be 3-5 mm (more than 90% by mass).
Further preferably, the method for separating PET and PVC based on low-temperature plasma induced flotation as described above, wherein the flotation container in the step (4) is columnar, and the diameter-depth ratio (inner diameter: high) is less than or equal to 1: 4.
Further preferably, the method for separating PET and PVC based on low temperature plasma induced flotation as described above, wherein the non-ionic foaming agent in step (4) is pine oil, and the dosage is 15-30mg/L.
Further preferably, the method for separating PET and PVC based on low-temperature plasma induced flotation as described above, wherein after the non-ionic foaming agent is added in the step (4), the operation is carried out for 5min under the condition of 200L/h of air aeration, and the floating product is collected to complete the separation.
Compared with the prior art, the method for separating PET and PVC based on low-temperature plasma induced flotation has the following advantages and remarkable progress:
(1) the invention provides an effective sorting method for PET and PVC, which is simple to operate and beneficial to industrial large-scale application.
(2) The method has simple flow, particularly no solvent is added in the plasma contact induction process, no oxidant or additional catalytic agent is used, the method is nontoxic and harmless to the environment, the cost is saved, and the secondary pollution of the water body can be effectively reduced.
(3) The invention belongs to mild treatment, is carried out at normal temperature and normal pressure, has no high-temperature pressurization link, and has high separation safety and efficiency.
(4) The invention can realize the on-line automatic operation in all links by depending on the conveying device, and is convenient to be popularized and applied by combining the existing large-scale flotation equipment.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments. It will be understood by those skilled in the art that the following examples are illustrative of the present invention only and should not be taken as limiting the scope of the invention. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
The method comprises four process links including a pretreatment step 1, a plasma contact induction step, a pretreatment step 2 and a flotation unit; the four process links are sequentially connected in series (pretreatment step 1 → plasma contact induction → pretreatment step 2 → flotation unit), and can be continuously operated on line; the feed in the pretreatment step 1 is mixed plastic, and the mixed plastic comprises polyvinyl chloride (PVC) and polyethylene terephthalate (PET) with different sources and mass ratios; and discharging by the flotation unit, wherein the floating product is PET, and the sinking tailing is separated PVC.
Example 1
The feeding composition of the embodiment is a mixture of PET and PVC products, the sources of the mixture are respectively building accessories and beverage bottles, the mass ratio distribution of the PET and the beverage bottles is close to 1, and the separation operation method comprises the following steps:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional dimension of coarse crushed materials to be less than 10mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in the atmospheric atmosphere by corona discharge (corona machine), and controlling the unit activation energy generated by plasma induction in the process to be 12kJ/m2(ii) a The size (length multiplied by width multiplied by spacing) of a working electrode of the corona machine is 500mm multiplied by 1mm multiplied by 1.5mm, the sine alternating voltage is 220VAC/50Hz for supplying power, the output power is 300W, and the linear speed of a feeding roller is 3.0 m/min;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90 mass percent) of a fine grinding product to be 0.5-1.5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:4), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 25: 1, adding a non-ionic foaming agent, namely, terpineol oil (20mg/L), operating for 5min under the condition of air aeration of 150L/h, and collecting a floating product to finish separation.
Example 2
The feeding composition of the embodiment is a mixture of PET and PVC products, the sources of the mixture are respectively a toy and a preservation box, and the mass ratio distribution of the PET to the PVC is close to 0.43: 1, the separation operation method comprises the following steps:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional dimension of coarse crushed materials to be smaller than 8mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in the atmospheric atmosphere by corona discharge (corona machine), and controlling unit activation energy generated by plasma induction in the process to be 15kJ/m2(ii) a The size (length multiplied by width multiplied by spacing) of a working electrode of the corona machine is 500mm multiplied by 1mm multiplied by 1.5mm, the sine alternating voltage is 220VAC/50Hz for supplying power, the output power is 300W, and the linear speed of a feeding roller is 2.4 m/min;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90% of the mass) of a fine grinding product to be 1.5-3 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:5), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent, namely pinitol oil (25mg/L), operating for 5min under the condition of air aeration of 200L/h, and collecting floating products to finish separation.
Example 3
The feeding composition of the embodiment is a mixture of PET and PVC products, the sources of the mixture are respectively a toy and a preservation box, the mass ratio distribution of the PET and the PVC is close to 0.43, and the separation operation method comprises the following steps:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional size of coarse crushed materials to be less than 6mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in the atmospheric atmosphere by corona discharge (corona machine), and controlling unit activation energy generated by plasma induction in the process to be 15kJ/m2(ii) a The size (length multiplied by width multiplied by spacing) of a working electrode of the corona machine is 500mm multiplied by 1mm multiplied by 1.5mm, the sine alternating voltage is 220VAC/50Hz for power supply, the output power is 600W, and the linear speed of a feeding roller is 4.8 m/min;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90% of the mass) of a fine grinding product to be 3-5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:4), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent, namely pinitol oil (25mg/L), operating for 5min under the condition of air aeration of 200L/h, and collecting floating products to finish separation.
Example 4
The feed composition of this example was a mixture of PET and PVC articles from packaging and beverage bottles, respectively, with a PET to PVC mass ratio distribution of approximately 2.33, and the separation procedure was:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional size of coarse crushed materials to be less than 6mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in an oxygen atmosphere by corona discharge (corona machine), and controlling unit activation energy generated by plasma induction in the process to be 15kJ/m2(ii) a The size (length, width and distance) of the working electrode of the corona machine is 500mm, 1mm, 1.5mm, the sine alternating voltage is 220VAC/50Hz, the output power is 600W, and the linear speed of the feeding roller is 4.8m/min; the flow rate of oxygen as carrier gas is about 30 sccm;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90% of the mass) of a fine grinding product to be 3-5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:4), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent, namely pinitol oil (25mg/L), operating for 5min under the condition of air aeration of 200L/h, and collecting floating products to finish separation.
Example 5
The feeding composition of the embodiment is a mixture of PET and PVC products, the sources of the mixture are toys and beverage bottles respectively, the mass ratio distribution of the PET and the PVC is close to 1.58, and the separation operation method comprises the following steps:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional size of coarse crushed materials to be less than 6mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma anode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in a nitrogen atmosphere by a radio frequency plasma torch generator, and controlling the unit activation energy generated by plasma induction in the process to be 15.0kJ/m2(ii) a The distance between parallel electrodes of the radio frequency (13.56MHz) plasma torch and the diameter are respectively 110mm and 200 mm; the gas supply flow rate of nitrogen as carrier gas is about 60 sccm;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90% of the mass) of a fine grinding product to be 3-5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:4), adding tap water as a solution medium, and mixing the fine granulated mixed plastic with the tap water in a solid-liquid ratio (kg:m3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent, namely pinitol oil (25mg/L), operating for 5min under the condition of air aeration of 200L/h, and collecting floating products to finish separation.
Example 6
The feeding composition of the embodiment is a mixture of PET and PVC products, the sources of the mixture are respectively building accessories and packaging materials, the mass ratio distribution of the PET and the PVC is close to 2.33, and the separation operation method comprises the following steps:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional dimension of coarse crushed materials to be less than 10mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in the atmospheric atmosphere by corona discharge (corona machine), and controlling the unit activation energy generated by plasma induction in the process to be 18kJ/m2(ii) a The size (length multiplied by width multiplied by spacing) of a working electrode of the corona machine is 500mm multiplied by 1mm multiplied by 1.5mm, the sine alternating voltage is 220VAC/50Hz for power supply, the output power is 600W, and the linear speed of a feeding roller is 4.0 m/min;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90% of the mass) of a fine grinding product to be 1.5-3.5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:5), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 25: 1, adding a non-ionic foaming agent, namely pinitol oil (15mg/L), operating for 15min under the condition of air aeration of 150L/h, and collecting floating products to finish separation.
Example 7
The feeding composition of the embodiment is a mixture of PET and PVC products, the sources of the mixture are respectively building accessories and a preservation box, the mass ratio distribution of the PET and the PVC is close to 1.98, and the separation operation method comprises the following steps:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional dimension of coarse crushed materials to be smaller than 8mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in the atmospheric atmosphere by corona discharge (corona machine), and controlling the unit activation energy generated by plasma induction in the process to be 13.5kJ/m2(ii) a The size (length multiplied by width multiplied by spacing) of a working electrode of the corona machine is 500mm multiplied by 1mm multiplied by 1.5mm, the sine alternating voltage is 220VAC/50Hz for supplying power, the output power is 300W, and the linear speed of a feeding roller is 2.7 m/min;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90 mass percent) of a fine grinding product to be 0.5-1.5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:6), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 15: 1, adding a non-ionic foaming agent, namely, terpineol oil (30mg/L), operating for 10min under the condition of 200L/h of air aeration, and collecting a floating product to finish separation.
Example 8
The feed composition of this example was a mixture of PET and PVC articles from building accessories and beverage bottles, respectively, with a PET to PVC mass ratio distribution of approximately 0.69, separated by the following procedure:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional dimension of coarse crushed materials to be smaller than 8mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: subjecting the sheeted mixed plastic obtained in step (1) to atmospheric pressureThe positive electrode of the plasma is in double-sided contact, the plasma is generated in an atmospheric atmosphere by corona discharge (corona machine), and the unit activation energy induced by the plasma is controlled to be 16.5kJ/m in the process2(ii) a The size (length multiplied by width multiplied by spacing) of a working electrode of the corona machine is 500mm multiplied by 1mm multiplied by 1.5mm, the sine alternating voltage is 220VAC/50Hz for power supply, the output power is 600W, and the linear speed of a feeding roller is 4.4 m/min;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90% of the mass) of a fine grinding product to be 3-5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:6), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding non-ionic foaming agent pinitol oil (15mg/L), operating for 3min under the condition of air aeration of 150L/h, and collecting floating products to finish separation.
Example 9
The feeding composition of the embodiment is a mixture of PET and PVC products, the sources of the mixture are respectively a toy and a preservation box, the mass ratio distribution of the PET and the PVC is close to 0.43, and the separation operation method comprises the following steps:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional size of coarse crushed materials to be less than 6mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in the atmospheric atmosphere by corona discharge (corona machine), and controlling unit activation energy generated by plasma induction in the process to be 15kJ/m2(ii) a The size (length multiplied by width multiplied by spacing) of a working electrode of the corona machine is 500mm multiplied by 1mm multiplied by 1.5mm, the sine alternating voltage is 220VAC/50Hz for power supply, the output power is 600W, and the linear speed of a feeding roller is 4.8 m/min;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90% of the mass) of a fine grinding product to be 3-5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:4), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent methyl isobutyl carbinol (25mg/L), operating for 5min under the condition of air aeration of 200L/h, and collecting floating products to finish separation.
Example 10
The feeding composition of the embodiment is a mixture of PET and PVC products, the sources of the mixture are respectively a toy and a preservation box, the mass ratio distribution of the PET and the PVC is close to 0.43, and the separation operation method comprises the following steps:
(1) pretreatment step 1: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, carrying out solid-liquid separation, crushing by using a small crusher, and controlling the smallest three-dimensional size of coarse crushed materials to be less than 6mm by using a thickness sieve to finish feeding sheeting;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under the atmospheric pressure, generating plasma in the atmospheric atmosphere by corona discharge (corona machine), and controlling unit activation energy generated by plasma induction in the process to be 15kJ/m2(ii) a The size (length multiplied by width multiplied by spacing) of a working electrode of the corona machine is 500mm multiplied by 1mm multiplied by 1.5mm, the sine alternating voltage is 220VAC/50Hz for power supply, the output power is 600W, and the linear speed of a feeding roller is 4.8 m/min;
(3) a pretreatment step 2: carrying out fine grinding on the mixed plastic subjected to the plasma contact induction in the step (2) by using a ball mill, and controlling the equivalent diameter (more than 90% of the mass) of a fine grinding product to be 3-5 mm by using a particle size sieve to finish fine granulation;
(4) a flotation unit: adding the fine granulated mixed plastic obtained in the step (3) into a flotation column (the diameter-depth ratio is 1:4), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent polyethylene glycol (25mg/L), and operating for 5m under the condition of air aeration of 200L/hAnd in, collecting floating products to complete separation.
In addition, regardless of the plasma induction process using the present invention, comparative experiments were conducted using only the flotation method, and the comparative examples were specifically operated as follows:
comparative example 1
The feeding composition of the comparative example is a mixture of PET and PVC products, the sources of the mixture are respectively a toy and a preservation box, the mass ratio distribution of the PET and the PVC is close to 0.43, and the separation operation method comprises the following steps:
(1) pretreatment: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, directly performing fine grinding by using a ball mill after solid-liquid separation, and controlling the equivalent diameter (more than 90 mass%) of a fine grinding object to be 3-5 mm by using a particle size sieve to finish fine granulation;
(2) flotation: adding the fine granulated mixed plastic obtained in the step (1) into a flotation column (the diameter-depth ratio is 1:4), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent, namely pinitol oil (25mg/L), operating for 5min under the condition of air aeration of 200L/h, and collecting floating products to finish separation.
Comparative example 2
The feeding composition of the comparative example is a mixture of PET and PVC products, the sources of the mixture are respectively a toy and a preservation box, the mass ratio distribution of the PET and the PVC is close to 0.43, and the separation operation method comprises the following steps:
(1) pretreatment: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, directly performing fine grinding by using a ball mill after solid-liquid separation, and controlling the equivalent diameter (more than 90 mass%) of a fine grinding object to be 3-5 mm by using a particle size sieve to finish fine granulation;
(2) flotation: adding the fine granulated mixed plastic obtained in the step (1) into a flotation column (the diameter-depth ratio is 1:4), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent methyl isobutyl carbinol (25mg/L), operating for 5min under the condition of air aeration of 200L/h, and collecting floating products to finish separation.
Comparative example 3
The feeding composition of the comparative example is a mixture of PET and PVC products, the sources of the mixture are respectively a toy and a preservation box, the mass ratio distribution of the PET and the PVC is close to 0.43, and the separation operation method comprises the following steps:
(1) pretreatment: firstly, soaking, stirring and feeding tap water containing detergent powder for 10min to remove stains, then re-washing and removing the detergent by using the tap water, directly performing fine grinding by using a ball mill after solid-liquid separation, and controlling the equivalent diameter (more than 90 mass%) of a fine grinding object to be 3-5 mm by using a particle size sieve to finish fine granulation;
(2) flotation: adding the fine granulated mixed plastic obtained in the step (1) into a flotation column (the diameter-depth ratio is 1:4), adding tap water serving as a solution medium, and obtaining a solid-liquid ratio (kg: m)3) Controlling the ratio to be 20: 1, adding a non-ionic foaming agent polyethylene glycol (25mg/L), operating for 5min under the condition of air aeration of 200L/h, and collecting and separating floating products.
After drying the floated product collected for use in examples 1 to 10 and comparative examples 1 to 3, the components were carefully selected and classified into different components according to color, texture and reflection factor, wherein the mass of PET was divided by the mass of PET in the feed as a recovery rate (in%) and the mass of PET was divided by the mass of the floated product as a purity (in%), and the results are shown in Table 1.
TABLE 1 recovery and purity of PET in the supernatant product collected in the examples and comparative examples
| Item | Recovery (%) | Purity (%) |
| Example 1 | 93.50 | 78.60 |
| Example 2 | 93.18 | 92.83 |
| Example 3 | 94.15 | 96.56 |
| Example 4 | 85.83 | 96.16 |
| Example 5 | 87.92 | 90.49 |
| Example 6 | 83.72 | 86.29 |
| Example 7 | 92.28 | 85.91 |
| Example 8 | 94.37 | 90.85 |
| Example 9 | 92.60 | 90.14 |
| Example 10 | 89.11 | 84.07 |
| Comparative example 1 | 89.28 | 49.16 |
| Comparative example 2 | 78.01 | 43.82 |
| Comparative example 3 | 70.50 | 41.34 |
As can be seen from Table 1, the comparative examples 1 to 3, which only adopt the flotation process, can not effectively separate the mixture of PET and PVC, the purity of PET is less than 50%, and the PET has no value in use, while the recovery rate of PET separated by the inventive examples 1 to 10 is above 83%, and the purity is basically above 80%, especially for the example 3, the recovery rate is above 94%, and the purity is above 96%. Therefore, the separation effect of the invention on PET is better, and the relevant parameters of the embodiment 3 in the separation process are selected to be optimal values in terms of purity.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the present invention in any way. Any simple modification, change and equivalent changes of the above embodiments according to the technical essence of the invention are still within the protection scope of the technical solution of the invention.
Claims (10)
1. A method for separating PET and PVC based on low-temperature plasma induced flotation is characterized by comprising the following steps:
(1) pretreatment step 1: collecting mixed plastics as a feed material, wherein the mixed plastics comprise PET and PVC, cleaning to remove stains, performing coarse crushing, and controlling the feed thickness to be less than or equal to 10mm to finish the sheeting of the feed material;
(2) plasma contact induction: carrying out plasma positive electrode double-sided contact on the laminated mixed plastic in the step (1) under atmospheric pressure, wherein the plasma is generated by a corona discharge or radio frequency plasma torch generator in the atmosphere or oxygen or nitrogen atmosphere, and the unit activation energy generated by controlling the induction of the plasma in the process is 12-18 kJ/m2；
(3) A pretreatment step 2: fine grinding the mixed plastic after the plasma contact induction in the step (2), and controlling the equivalent diameter to be 0.5-5 mm by using a particle size sieve to finish fine feeding particles;
(4) a flotation unit: placing the mixed plastic after the fine granulation in the step (3) into a flotation container, adding tap water as a solution medium, wherein the solid-to-liquid ratio is as follows: m is3Adding a non-ionic foaming agent according to the ratio of (15-25) to 1, operating for 3-15 min under the condition of air aeration of 150-300L/h, and collecting and separating floating products.
2. The method for separating PET and PVC based on low-temperature plasma induced flotation according to claim 1, wherein the mass ratio of PET to PVC in the mixed plastic in the step (1) is (0.43-2.33): 1.
3. the method for separating PET and PVC based on low temperature plasma induced flotation according to claim 1, wherein the cleaning process in step (1) is as follows: soaking in tap water containing detergent while stirring, re-washing with tap water to remove detergent, and separating solid from liquid.
4. The method for separating PET and PVC based on low-temperature plasma induced flotation according to claim 1, wherein the coarse crushing control feed thickness in step (1) is less than or equal to 6 mm.
5. The method for separating PET and PVC based on low-temperature plasma induced flotation according to claim 1, characterized in that corona discharge is performed by using a corona machine in the step (2), parameters of working electrodes in the corona machine are 500mm in length, 1mm in width and 1.5mm in distance, sinusoidal alternating voltage is 220VAC/50Hz for power supply, maximum output power is 1kW, and maximum linear speed of a feeding roller is 15 m/min.
6. The method for separating PET and PVC based on low-temperature plasma induced flotation according to claim 1, wherein the specific activation energy for controlling the plasma induction generation in the step (2) is 15kJ/m2。
7. The method for separating PET and PVC based on low-temperature plasma induced flotation according to claim 1, wherein the fine grinding in the step (3) is ball milling treatment, and the equivalent diameter of the material after fine grinding is controlled to be 3-5 mm.
8. The method for separating PET and PVC based on low-temperature plasma induced flotation according to claim 1, wherein the flotation container in the step (4) is columnar, and the diameter-depth ratio is less than or equal to 1: 4.
9. The method for separating PET and PVC based on low-temperature plasma induced flotation according to claim 1, wherein the non-ionic foaming agent in the step (4) is terpineol oil, and the adding amount is 15-30mg/L.
10. The method for separating PET and PVC based on low-temperature plasma induced flotation according to claim 1, wherein after the non-ionic foaming agent is added in the step (4), the operation is carried out for 5min under the condition of 200L/h of air aeration, and the floating product is collected to complete the separation.
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| DE19519865A1 (en) * | 1994-08-05 | 1996-02-15 | Daimler Benz Ag | Selective sepn. of various plastics from particle mixt. by flotation |
| US5566832A (en) * | 1994-08-05 | 1996-10-22 | Daimler-Benz Ag | Method for sorting plastics from a particle mixture composed of different plastics |
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