Dry cleaning system and process for waste plastics

Abstract

The invention relates to the technical field of plastic dry cleaning, in particular to a dry cleaning system and process for waste plastics. The dry cleaning system comprises a blower device for providing pulse airflow; the pulsed fluidized bed for cleaning the waste plastics comprises a tank body and an air chamber detachably connected with the bottom of the tank body, the tank body is provided with an air outlet and a feeding port, the air chamber is provided with an air inlet connected with the blower device, the tank body is filled with gravel, and the detached air chamber serves as a discharging port for cleaning the waste plastics and the gravel; the dust removal device is connected with a gas inlet of the pulsed fluidized bed and is used for removing dust from gas discharged by the pulsed fluidized bed; and the screening device is used for screening the cleaned waste plastics and gravels. Compared with the prior art, the dry-method cleaning device and the dry-method cleaning process have the advantages that the pulse airflow and the gravel are used as cleaning media in the pulse fluidized bed, and the dry-method cleaning device and the dry-method cleaning process are high in cleaning effect and adaptability.

Description

Technical Field

[0001] The invention relates to the technical field of dry cleaning of plastics, and in particular to a dry cleaning system and process for waste plastics. Background Art

[0002] At present, mechanical treatment is the main way to recycle waste plastics. However, in the actual recycling process, the inconsistent quality of recycled raw materials often leads to a decrease in the mechanical properties of recycled plastics. The pollutants attached to the surface of plastics after use are one of the main reasons for the uneven quality of recycled plastics. The cleanliness of waste plastics directly affects the quality of recycled plastic products. Therefore, the surface of waste plastics needs to be cleaned before mechanical treatment. Traditional wet cleaning requires the use of a large amount of water and chemical cleaning agents. The energy consumption of wastewater treatment and plastic drying reduces the sustainability and economy of plastic recycling. Therefore, plastic cleaning urgently needs the application of new technologies.

[0003] The dry cleaning process is different from the traditional wet cleaning technology. It does not require the participation of solvents such as water. It uses friction media such as river sand and air to clean waste plastics. It does not need to be dried after cleaning, which can avoid the high energy consumption problem in the cleaning process. Gao Yuxin et al. (Gao Yuxin. Dry Cleaning and Equipment Research of Waste Plastic Film [D]. Kunming University of Science and Technology, 2006) use high-speed air to clean recycled plastics, but this method has high requirements on the internal structure of the equipment. The number of round rods in the cavity reaches 200, which is not conducive to equipment maintenance. In addition, the cleaning effect is limited, and the cleaning rate is less than 80%, which is difficult to meet the raw material requirements for producing high-quality recycled plastics. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a dry cleaning system and process for waste plastics. In a pulsed fluidized bed, pulsed airflow and sand and gravel are used as cleaning media to obtain a dry cleaning device and process with higher cleaning effect and stronger adaptability.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] In one aspect, the present invention provides a dry cleaning system for waste plastics, comprising:

[0007] A blower device providing a pulsed air flow;

[0008] A pulse fluidized bed for cleaning waste plastics, comprising a tank body and an air chamber detachably connected to the bottom thereof, the tank body being provided with a gas outlet and a feeding port, the air chamber being provided with a gas inlet connected to the blasting device, the tank body being filled with sand and gravel, and the air chamber being disassembled to serve as a discharge port for cleaning waste plastics and sand and gravel;

[0009] a dust removal device connected to the gas inlet of the pulse fluidized bed and used for removing dust from the gas discharged from the pulse fluidized bed;

[0010] And a screening device for screening and cleaning waste plastics and sand and gravel.

[0011] The pulse airflow is generated by the blowing device, enters the air chamber from the gas inlet, and then enters the tank body, so that the sand and gravel therein are in a fluidized state, and the waste plastics are cleaned by using the high-pressure pulse airflow and sand and gravel. The pulse gas is discharged from the gas outlet and enters the dust removal device for dust removal. The air chamber is removed, and the clean waste plastics and sand and gravel are poured into the screening device for screening to obtain clean waste plastic products and sand and gravel.

[0012] Furthermore, the specific conditions of the pulse airflow provided by the blowing device are: surface wind speed of 0.5-0.9 m / s, pulse frequency of 1-4 Hz, pulse amplitude of 0.1-0.4 m / s, and temperature of 15-35° C. When the pulse frequency is too high, the pulse airflow is no different from the uniform airflow, that is, the pulse airflow loses its effect advantage;

[0013] The cleaning time of the waste plastics in the pulse fluidized bed is 40 seconds to 30 minutes, preferably 5 to 15 minutes. When the cleaning time is 40 seconds, the dry cleaning system can achieve basic cleaning of the waste plastics.

[0014] Furthermore, the waste plastics include film plastics, hard plastics, and plastic particles, wherein the film plastics have a size of 20 to 40 mm.

[0015] Furthermore, the sand and gravel filled in the tank body include quartz sand particles with a particle size of 0.1 to 0.5 mm, and the mass ratio of the waste plastic to the sand and gravel is 1:250 to 1000.

[0016] Furthermore, the blowing device includes a high-pressure blower for generating high-pressure pulsed airflow and a heater for controlling the air temperature of the pulsed airflow. The high-pressure blower can fully fluidize the pulsed fluidized bed, and the heater can control the temperature of the pulsed airflow, and its inlet is connected to the outlet of the high-pressure blower.

[0017] Furthermore, the high-pressure fan includes a high-pressure blower, the power is preferably 1-5kw, the wind speed can be adjusted according to the cleaning conditions, and the preferred surface wind speed is 0.5-0.9m / s, which is the surface wind speed of the pulse airflow in the fluidized bed.

[0018] Furthermore, the heater is an industrial hot air blower.

[0019] Furthermore, the high-pressure blower, the heater and the pulse fluidized bed are connected via PVC pipes.

[0020] Furthermore, the tank body comprises a reaction section, an expansion section and an outlet section which are sequentially connected from bottom to top, the reaction section is the main cleaning area for waste plastics, and the expansion section is used to prevent sand and gravel in the pulse fluidized bed from being carried out with the pulse airflow;

[0021] A vertically arranged agitator is arranged in the tank body;

[0022] A gas distribution plate is provided between the gas chamber and the reaction section;

[0023] The gas outlet is arranged in the reaction section, and the feed port is arranged in the outlet section.

[0024] Furthermore, the rotation speed of the stirrer is 20 to 60 r / min.

[0025] Furthermore, the agitator is a frame-type agitator.

[0026] Furthermore, the agitator is arranged at the top of the outlet section.

[0027] Furthermore, the gas distribution plate is a hood distribution plate, with a total of 40 to 70 gas outlet pipes, and each gas outlet pipe has a number of holes obliquely downward to ensure uniform distribution of gas.

[0028] Furthermore, the reaction section, the gas distribution plate and the gas chamber are connected by flanges, and the material can be unloaded by disassembling the gas chamber at the bottom.

[0029] Furthermore, a plurality of pressure measuring points and a plurality of temperature measuring points are arranged on the side of the pulse fluidized bed for measuring the pressure and temperature parameters during the operation of the pulse fluidized bed.

[0030] Furthermore, the pressure measuring points are respectively arranged in the gas chamber, the reaction section and the expansion section, and the temperature measuring point is arranged in the reaction section.

[0031] Furthermore, the temperature measuring point is a thermocouple, which is used to measure the temperature of the pulse fluidized bed reaction section, and is preferably a digital thermometer.

[0032] Furthermore, the gas inlet is a 90° elbow, and the elbow is downward, and the pulse gas flow enters directly below the pulse fluidized bed to ensure uniform distribution of the gas.

[0033] Furthermore, the dust removal device includes a bag dust collector, a cyclone dust collector or an electric dust collector.

[0034] Furthermore, the screening device includes a screen and a screening machine.

[0035] Furthermore, the screen is a 5-10 mesh screen. For the cleaning process mainly polluted by dust, the sand and gravel can be directly returned to the pulse fluidized bed for repeated use. For the cleaning process contaminated with a small amount of organic matter, the sand and gravel can be transferred to the incinerator for thermal treatment and recovery after multiple uses according to the surface pollution.

[0036] Furthermore, the dry cleaning system also includes a control device connected to the blowing device, the pulse fluidized bed, and the dust removal device, which is controlled by PLC.

[0037] Furthermore, the dry cleaning system also includes a shearing device, which is a shredder or a shearing crusher, for shearing the waste plastics to a specified size.

[0038] In another aspect, the present invention further provides a dry cleaning method for waste plastics, which is implemented using the above-mentioned dry cleaning system. The dry cleaning method comprises the following steps:

[0039] S1. Pre-treatment: air-dry the waste plastics and cut them into specific sizes;

[0040] S2, adjustment: adding sand and waste plastics into the pulse fluidized bed;

[0041] S3, cleaning: controlling the pulse frequency and pulse amplitude of the pulse airflow in the blowing device to fluidize the sand and gravel in the pulse fluidized bed to clean the waste plastics;

[0042] S4, separation: the blowing device is turned off, the waste plastics and sand and gravel are discharged from the tank body and then screened through the screening device to obtain clean waste plastic products and sand and gravel.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] (1) The present invention uses a gas-solid pulse fluidized bed to dry clean waste plastics, and uses the friction between high-speed air and the cleaning medium quartz sand and the blowing effect of high-speed air to achieve dry cleaning of waste plastics. The present invention further improves the fluidization effect of the fluidized bed through controllable pulse airflow, improves the cleaning efficiency, promotes the fluidization process with the help of an agitator, solves the load problem of the cleaning process, and increases the amount of plastic added in a single cleaning.

[0045] (2) The present invention can achieve a better cleaning effect by changing conditions such as stirring speed, wind speed, pulse frequency, pulse amplitude, etc., and can enhance the cleaning effect of pulse airflow, shorten the cleaning time, improve the cleaning effect, and reduce the cleaning cost.

[0046] (3) The cleaning process of the present invention is efficient and does not cause wastewater discharge and drying energy consumption problems. It can provide a plastic cleaning method for areas with water shortages and promote plastic recycling. The present invention uses cheap sand and gravel as a cleaning medium. When the pollutants are mainly dust, the medium has self-cleaning ability, and the sand and gravel can be reused multiple times, reducing the cost of solid waste treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a schematic diagram of a dry cleaning system shown in Example 1;

[0048] Figure 2 is a flow chart of the dry cleaning method shown in Example 1;

[0049] Figure 3 It is a schematic diagram of the structure of the pulse fluidized bed shown in Example 1;

[0050] Figure 4 This is a schematic diagram of the structure of the gas distribution plate shown in Example 1;

[0051] Figure 5 This is a schematic diagram of the gas distribution plate hood structure shown in Example 1;

[0052] Figure 6 is a schematic diagram of a dry cleaning system shown in Example 2;

[0053] Figure 7 It is a comparison chart of the cleaning effects of Comparative Examples 2 to 6.

[0054] Description of the markings in the figure:

[0055] 1-blowing device, 11-high pressure fan, 12-heater;

[0056] 2-pulse fluidized bed, 21-tank body, 211-reaction section, 212-expansion section, 213-exit section, 22-gas chamber, 23-gas outlet, 24-feeding port, 25-gas inlet, 26-agitator, 27-gas distribution plate, 28-pressure measuring point, 29-temperature measuring point;

[0057] 3-Dust removal device;

[0058] 4- Control device;

[0059] 5-Screening device. DETAILED DESCRIPTION

[0060] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments are implemented based on the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments. In the following embodiments or embodiments, if there is no special description of the functional components or structures, it means that they are all conventional components or conventional structures used in the art to achieve the corresponding functions.

[0061] It should be noted that in the description of the present invention, the terms "upper", "lower", "inner", "outer", "front end", "rear end", "two ends", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0062] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] The present invention provides a dry cleaning system for waste plastics, comprising:

[0064] A blower 1 for providing a pulsed airflow;

[0065] The pulse fluidized bed 2 for cleaning waste plastics comprises a tank body 21 and an air chamber 22 detachably connected to the bottom thereof, the tank body 21 is provided with a gas outlet 23 and a feeding port 24, the air chamber 22 is provided with a gas inlet 25 connected to the blast device 1, the tank body 21 is filled with sand and gravel, and the air chamber 22 is disassembled to serve as a discharge port for cleaning waste plastics and sand and gravel;

[0066] A dust removal device 3 connected to the gas inlet 25 of the pulse fluidized bed 2 and used for removing dust from the gas discharged from the pulse fluidized bed 2;

[0067] And a screening device 5 for screening the cleaned waste plastics and sand and gravel.

[0068] The pulse airflow is generated by the blowing device 1, enters the air chamber 22 from the gas inlet 25, and then enters the tank body 21, so that the sand and gravel therein are in a fluidized state, and the waste plastics are cleaned by using the high-pressure pulse airflow and sand and gravel. The pulse gas is discharged from the gas outlet 23 and enters the dust removal device 3 for dust removal. The air chamber 22 is removed, and the clean waste plastics and sand and gravel are poured into the screening device 5 for screening to obtain clean waste plastic products and sand and gravel.

[0069] As one of the preferred embodiments, the specific conditions of the pulse airflow provided by the blower 1 are: surface wind speed of 0.5-0.9 m / s, pulse frequency of 1-4 Hz, pulse amplitude of 0.1-0.4 m / s, and temperature of 15-35° C. When the pulse frequency is too high, the pulse airflow is no different from the uniform airflow, that is, the pulse airflow loses its effect advantage;

[0070] The cleaning time of the waste plastics in the pulse fluidized bed is 40 seconds to 30 minutes, preferably 5 to 15 minutes. When the cleaning time is 40 seconds, the dry cleaning system can achieve basic cleaning of the waste plastics.

[0071] As one of the preferred implementations, the waste plastics include film plastics, hard plastics, and plastic particles, wherein the film plastics have a size of 20 to 40 mm.

[0072] As one of the preferred implementations, the sand and gravel filled in the tank body 21 include quartz sand particles with a particle size of 0.1 to 0.5 mm, and the mass ratio of the waste plastic to the sand and gravel is 1:250 to 1000.

[0073] As one of the preferred embodiments, the blast device 1 includes a high-pressure blower 11 for generating a high-pressure pulsed airflow, and a heater 12 for controlling the air temperature of the pulsed airflow. The high-pressure blower 1 can fully fluidize the pulsed fluidized bed 2, and the heater 12 can control the temperature of the pulsed airflow, and its inlet is connected to the outlet of the high-pressure blower 11.

[0074] As one of the preferred embodiments, the high-pressure fan 11 includes a high-pressure blower, and the power is preferably 1 to 5 kW. The wind speed can be adjusted according to the cleaning conditions. The preferred surface wind speed is 0.5 to 0.9 m / s, and the surface wind speed is the surface wind speed of the pulse airflow in the fluidized bed.

[0075] As one of the preferred implementations, the heater 12 is an industrial hot air blower.

[0076] As one of the preferred implementations, the high-pressure blower 11, the heater 12, and the pulse fluidized bed 2 are connected via PVC pipes.

[0077] As one of the preferred embodiments, the tank body 21 includes a reaction section 211, an expansion section 212 and an outlet section 213 connected in sequence from bottom to top, the reaction section 211 is the main cleaning area for waste plastics, and the expansion section 212 is used to prevent sand and gravel in the pulse fluidized bed 2 from being carried out with the pulse airflow;

[0078] A vertically arranged agitator 26 is arranged in the tank body 21;

[0079] A gas distribution plate 27 is provided between the gas chamber 22 and the reaction section 211;

[0080] The gas outlet 23 is disposed in the reaction section 211 , and the feed port 24 is disposed in the outlet section 213 .

[0081] As one of the preferred implementations, the rotation speed of the stirrer 26 is 20 to 60 r / min.

[0082] As one of the preferred implementations, the agitator 26 is a frame-type agitator.

[0083] As one of the preferred implementations, the agitator 26 is disposed at the top of the outlet section 213 .

[0084] As one of the preferred implementations, the gas distribution plate 27 is a hood distribution plate, with a total of 40 to 70 gas outlet pipes, each of which has a number of holes obliquely downward to ensure uniform distribution of gas.

[0085] As one of the preferred implementations, the reaction section 211, the gas distribution plate 27 and the gas chamber 22 are connected by flanges, and the material can be unloaded by disassembling the gas chamber 22 at the bottom.

[0086] As one of the preferred implementations, a plurality of pressure measuring points 28 and a plurality of temperature measuring points 29 are provided on the side of the pulse fluidized bed 2 for measuring the pressure and temperature parameters during the operation of the pulse fluidized bed 2 .

[0087] As one of the preferred implementations, the pressure measuring points 28 are respectively arranged in the gas chamber 22 , the reaction section 211 , and the expansion section 212 , and the temperature measuring point 29 is arranged in the reaction section 211 .

[0088] As one of the preferred implementations, the temperature measuring point 29 is a thermocouple, which is used to measure the temperature of the reaction section 211 of the pulse fluidized bed 2, and is preferably a digital thermometer.

[0089] As one of the preferred implementations, the gas inlet 25 is a 90° elbow, and the elbow is downward, and the pulse gas flow enters directly below the pulse fluidized bed 2 to ensure uniform distribution of the gas.

[0090] As one of the preferred implementations, the dust removal device 3 includes a bag dust collector, a cyclone dust collector or an electrostatic precipitator.

[0091] As one of the preferred implementations, the screening device 5 includes a screen and a screening machine.

[0092] As one of the preferred embodiments, the screen is a 5-10 mesh screen. For the cleaning process mainly polluted by dust, the sand and gravel can be directly returned to the pulse fluidized bed 2 for repeated use. For the cleaning process contaminated with a small amount of organic matter, the sand and gravel can be transferred to the incinerator for thermal treatment and recovery according to the surface pollution after multiple uses.

[0093] As one of the preferred embodiments, the dry cleaning system further comprises a control device 4 connected to the blowing device 1, the pulse fluidized bed 2 and the dust removal device 3, which is PLC controlled.

[0094] As one of the preferred embodiments, the dry cleaning system further comprises a shearing device, which is a shredder or a shearing crusher, for shearing the waste plastics to a specified size.

[0095] The present invention also provides a dry cleaning method for waste plastics, which is implemented by using the above-mentioned dry cleaning system. The dry cleaning method comprises the following steps:

[0096] S1. Pre-treatment: air-dry the waste plastics and cut them into specific sizes;

[0097] S2, adjustment: adding sand and waste plastics into the pulse fluidized bed 2;

[0098] S3, cleaning: controlling the pulse frequency and pulse amplitude of the pulse airflow in the blowing device 1, so that the sand and gravel in the pulse fluidized bed 2 are in a fluidized state, and the waste plastics are cleaned;

[0099] S4, separation: the blowing device 1 is closed, the waste plastics and sand and gravel are discharged from the tank body 21 and then screened through the screening device 5 to obtain clean waste plastic products and sand and gravel.

[0100] Example 1

[0101] The present invention provides a dry cleaning system for waste plastics, such as Figures 1 to 3 As shown, including:

[0102] A blower 1 for providing a pulsed airflow;

[0103] The pulse fluidized bed 2 for cleaning waste plastics comprises a tank body 21 and an air chamber 22 detachably connected to the bottom thereof, the tank body 21 is provided with a gas outlet 23 and a feeding port 24, the air chamber 22 is provided with a gas inlet 25 connected to the blast device 1, the tank body 21 is filled with sand and gravel, and the air chamber 22 is disassembled to serve as a discharge port for cleaning waste plastics and sand and gravel;

[0104] A dust removal device 3 connected to the gas inlet 25 of the pulse fluidized bed 2 and used for removing dust from the gas discharged from the pulse fluidized bed 2;

[0105] And a screening device 5 for screening the cleaned waste plastics and sand and gravel.

[0106] The pulse airflow is generated by the blowing device 1, enters the air chamber 22 from the gas inlet 25, and then enters the tank body 21, so that the sand and gravel therein are in a fluidized state, and the waste plastics are cleaned by using the high-pressure pulse airflow and sand and gravel. The pulse gas is discharged from the gas outlet 23 and enters the dust removal device 3 for dust removal. The air chamber 22 is removed, and the clean waste plastics and sand and gravel are poured into the screening device 5 for screening to obtain clean waste plastic products and sand and gravel.

[0107] In this embodiment, the blowing device 1 includes a high-pressure fan 11 for generating a high-pressure pulse airflow, and a heater 12 for controlling the air temperature of the pulse airflow. The high-pressure fan 1 can fully fluidize the pulse fluidized bed 2, and the heater 12 can control the temperature of the pulse airflow, and its inlet is connected to the outlet of the high-pressure fan 11. The high-pressure fan 11 is a high-pressure blower, and its model is RB-71D-3, and its power is preferably 3kw, and the wind speed can be adjusted according to the cleaning conditions. The heater 12 is an industrial hot air blower, and its model is RPL-35-60-60. The high-pressure fan 11, the heater 12, and the pulse fluidized bed 2 are connected by PVC pipes.

[0108] In this embodiment, the tank body 21 includes a reaction section 211, an expansion section 212 and an outlet section 213 connected in sequence from bottom to top. The reaction section 211 is the main cleaning area for waste plastics. The reaction section 211 is filled with 2.5 kg of 0.1-0.5 mm quartz sand. The reaction section 211 is 800 mm high. The expansion section 212 is used to prevent sand and gravel in the pulse fluidized bed 2 from being carried out by the pulse airflow. It is 240 mm high and its diameter is expanded from 200 mm at the connection of the reaction section 211 to 300 mm at the top outlet section 213. A vertically arranged agitator 26 is arranged in the tank body 21; a gas distribution plate 27 is arranged between the gas chamber 22 and the reaction section 211; the gas outlet 23 is arranged in the reaction section 211, and the diameter of the gas outlet 23 is 50 mm; the feeding port 24 is arranged in the outlet section 213, and the diameter of the feeding port 24 is 100 mm, and the diameter of the gas inlet 25 is 50 mm. The height of the gas chamber 22 is 250 mm, and the height of the outlet section 213 is 50 mm. The agitator 26 is a frame agitator, model 80BL110S25-415TK9, and the agitator 26 is arranged at the top of the outlet section 213. Figure 4 and 5 As shown, the gas distribution plate 27 is a hood distribution plate, with a total of 57 outlet pipes, each of which has 4 holes with a diameter of 3 mm diagonally downward to ensure uniform distribution of gas. The reaction section 211, the gas distribution plate 27 and the gas chamber 22 are connected by flanges, and the gas chamber 22 can be disassembled at the bottom to unload.

[0109] In this embodiment, a plurality of pressure measuring points 28 and a plurality of temperature measuring points 29 are provided on the side of the pulse fluidized bed 2 for measuring the pressure and temperature parameters during the operation of the pulse fluidized bed 2. The pressure measuring points 28 are respectively provided in the gas chamber 22, the reaction section 211, and the expansion section 212, wherein there are 1 gas chamber, 2112 reaction sections, and 1 expansion section 212. The temperature measuring point 29 is provided in the reaction section 211, and there is 1 temperature measuring point. The temperature measuring point 29 is a digital thermometer for measuring the temperature of the reaction section 211 of the pulse fluidized bed 2, and the model is LCD-06058.

[0110] In this embodiment, the gas inlet 25 is a 90° elbow, and the elbow is downward, and the pulse gas flow enters directly below the pulse fluidized bed 2 to ensure uniform distribution of the gas.

[0111] In this embodiment, the dust removal device 3 is a bag dust collector, which is connected to the gas outlet 22 in the pulse fluidized bed 2 and is used to remove dust from the gas discharged from the pulse fluidized bed 2 and discharge the dust-removed gas.

[0112] In this embodiment, the screening device 5 is a screen and a screening machine. The screen is a 7-mesh screen. For the cleaning process mainly polluted by dust, the sand and gravel can be directly returned to the pulse fluidized bed 2 for repeated use. For the cleaning process contaminated with a small amount of organic matter, the sand and gravel can be transferred to the incinerator for thermal treatment and recovery according to the surface pollution after multiple uses.

[0113] In this embodiment, the dry cleaning system further comprises a shearing device, which is a shearing shredder, for shearing the waste plastics to a specified size.

[0114] In this embodiment, the waste plastic is a supermarket shopping bag contaminated by soil, and the material is a 4-filament PE plastic film, which is cut to a size of 20-40 mm and used as a cleaning material. The sand and gravel filled in the tank 21 are quartz sand particles with a particle size of 0.1-0.5 mm, and the mass ratio of the waste plastic to the sand and gravel is 1:250. The specific conditions of the pulse airflow provided by the blowing device 1 are: the frequency of the high-pressure fan 1 is 22 Hz, the surface wind speed of the pulse fluidized bed 2 is 0.85 m / s, the pulse frequency is 1 Hz, the pulse amplitude is 0.25 m / s, the heated pulse airflow enters from the gas inlet 25, the rotation speed of the agitator 26 is set to 40 r / min, and the temperature of the gas outlet 23 is set to 20 ° C. The cleaning time of the waste plastic in the pulse fluidized bed 2 is 10 min.

[0115] In this embodiment, the dry cleaning method implemented by the above-mentioned dry cleaning system includes the following steps:

[0116] S1. Pretreatment: air-dry the waste plastics, cut them into 20-40 mm by a shearing crusher, and use them as cleaning raw materials;

[0117] S2, adjustment: set the frequency of the high-pressure blower 1 to 22 Hz, the surface wind speed of the pulse fluidized bed 2 to 0.85 m / s, the pulse frequency to 1 Hz, the pulse amplitude to 0.25 m / s, the heated pulse airflow enters from the gas inlet 25, set the speed of the agitator 26 to 40 r / min, add 2.5 kg of sand and gravel from the feeding port 24 to the reaction section 211 of the pulse fluidized bed 2, so that the sand and gravel in the pulse fluidized bed 2 are in a fluidized state after the high-pressure blower 11 is turned on;

[0118] S3, cleaning: turn on the high-pressure fan 11 and the heater 12, set the temperature of the gas outlet 23 to 20°C, the temperature is based on the temperature at the temperature measuring point 29, after the temperature stabilizes, add 0.01 kg of pre-treated waste film plastic from the feeding port 24, close the feeding port 24 to clean the waste film plastic, and the cleaning time is 10 minutes;

[0119] S4, separation: after the cleaning is completed, turn off the heater 12, the high-pressure air 11 and the agitator 26, remove the air chamber 22 at the bottom of the pulse fluidized bed 2 from the gas distribution plate 27, collect the quartz sand and the cleaned film plastic product, and sieve the quartz sand and the film plastic with a 7-mesh screen. The quartz sand can be used for the next dry cleaning, and the film plastic can be used for cleaning evaluation.

[0120] Example 2

[0121] like Figure 6 As shown, compared with Example 1, most of them are the same, except that in this embodiment, the dry cleaning system also includes a control device 4 connected to the blowing device 1, the pulse fluidized bed 2, and the dust removal device 3, which is controlled by PLC.

[0122] The film plastic used in this embodiment has the same source as that of the film plastic in Embodiment 1.

[0123] Example 3

[0124] Compared with Example 1, most of them are the same, except that the waste plastic is a plastic bottle contaminated by dust and the material is a 10-filament PET plastic film.

[0125] Example 4

[0126] Compared with Example 1, most of the contents are the same, except that the waste plastic is a mixed plastic film obtained by mixing a 10-filament PET plastic film and a 4-filament PE plastic film contaminated by dust in a ratio of 1:1.

[0127] Example 5

[0128] Compared with Example 1, most of them are the same, except that the cleaning time in step S3 is adjusted to 40 seconds.

[0129] The film plastic used in this embodiment has the same source as that of the film plastic in Embodiment 1.

[0130] Example 6

[0131] Compared with Example 1, most of them are the same, except that the pulse amplitude of the pulse airflow is 0.15 m / s and the pulse frequency is 1.66 Hz.

[0132] Comparative Example 1

[0133] The same film plastic as in Example 1 was taken as a sample, washed with 2000 ml of water for 15 min by stirring, rinsed with 1500 ml of water for 3 times, and then dried in an oven at 55° C. to constant weight.

[0134] The film plastic used in this comparative example has the same source as that of the film plastic in Example 1.

[0135] Comparative Example 2

[0136] Compared with Example 1, most of them are the same, except that the cleaning time in step S3 is adjusted to 40 seconds, and the pulse airflow in the high-pressure fan 1 is adjusted to a uniform airflow of 22 Hz.

[0137] The film plastic used in this comparative example has the same source as that of the film plastic in Example 1.

[0138] Comparative Example 3

[0139] Compared with Comparative Example 2, most of the steps are the same, except that the cleaning time in step S3 is adjusted to 60 seconds.

[0140] The film plastic used in this comparative example has the same source as that of the film plastic in Example 1.

[0141] Comparative Example 4

[0142] Compared with Comparative Example 2, most of the steps are the same, except that the cleaning time in step S3 is adjusted to 2 minutes.

[0143] The film plastic used in this comparative example has the same source as that of the film plastic in Example 1.

[0144] Comparative Example 5

[0145] Compared with Comparative Example 2, most of the steps are the same, except that the cleaning time in step S3 is adjusted to 5 min.

[0146] The film plastic used in this comparative example has the same source as that of the film plastic in Example 1.

[0147] Comparative Example 6

[0148] Compared with Comparative Example 2, most of the steps are the same, except that the cleaning time in step S3 is adjusted to 10 min.

[0149] The film plastic used in this comparative example has the same source as that of the film plastic in Example 1.

[0150] The film plastic used in this embodiment has the same source as that of the film plastic in Embodiment 1.

[0151] Performance Test:

[0152] In order to evaluate the cleaning effect of the cleaning process, two evaluation methods are defined, namely, the gravimetric cleaning effect (PRIm) and the spectral cleaning effect (PRIt).

[0153] (1) Definition: The cleaning effect of the gravimetric method reflects the weight change before and after cleaning, which is the ratio of the initial mass, the mass after contamination and the mass after cleaning. The calculation formula is:

[0154]

[0155] Among them, m 0 is the initial mass of the plastic film, in g; m 1 is the mass of the contaminated plastic film, in g; m 2 is the mass of the plastic film after cleaning, in g.

[0156] (2) Definition: Spectral cleaning effect reflects the change in transmittance before and after cleaning. Transmittance is the degree of transmission of visible light through the plastic sheet, expressed as a percentage. The spectral cleaning effect is the ratio of initial transmittance, transmittance after contamination, and transmittance after cleaning. The calculation formula is:

[0157]

[0158] Among them, T 0 is the initial light transmittance of the plastic film, in %; T 1 is the light transmittance of the contaminated plastic film, in %; T 2 is the light transmittance of the plastic film after cleaning, in %. The cleaning effects obtained in Examples 1, 3, 4 and Comparative Examples 1 to 7 are shown in Table 1.

[0159] Table 1 Comparison of cleaning effects of different embodiments and comparative examples

[0160]

[0161] From Table 1 and Figure 7 It can be seen that the dry cleaning system using pulsed airflow is used to clean the film plastic. When cleaning for 40s (Comparative Example 8), the cleaning effect is more than 90% by weight, reaching 90.3%, and 68.51% by spectral method. However, its cleaning effect is equivalent to that of the dry cleaning system using uniform airflow (Comparative Example 2). The cleaning effect of using uniform airflow for 40s is 90.48% by weight and 42.53% by spectral method. This is because the cleaning time is short, only the basic cleaning of the plastic surface is completed, and the easily removable pollutants are removed first, so the pulsed airflow and uniform airflow perform similarly. It can be seen from the spectral method that the pulsed airflow has better cleaning effect and cleaning uniformity, so compared with the uniform airflow, the pulsed airflow has certain advantages.

[0162] When the cleaning time reaches 10 minutes, the cleaning effect of the dry cleaning system (Example 1) using pulsed airflow can reach 99.8% by weight and 97.34% by spectral method; the cleaning effect of the dry cleaning system (Comparative Example 6) using uniform airflow is 94.89% by weight and 73.29% by spectral method. The cleaning effect of the dry cleaning system using pulsed airflow in the present invention is much greater than that of the dry cleaning system using uniform airflow. It can be seen that under the same cleaning time and fan frequency, the pulsed airflow can achieve a better cleaning effect than the average airflow, indicating that the device and process have the potential to further improve the dry cleaning effect under the condition of pulsed airflow. The fluidization process of the fluidized bed is more uniform under the action of pulsed airflow, which can significantly reduce problems such as dead zones and improve cleaning uniformity. At the same time, the pulsed airflow can enhance the movement of particles in the vertical direction, further enhance the friction between the cleaning medium and the plastic sheet, and further improve the cleaning effect.

[0163] It can be seen from Comparative Examples 3 to 7 that as the cleaning time increases, the cleaning effect increases, and the spectral cleaning effect tends to be stable after 5 minutes of cleaning. Therefore, the cleaning time of waste plastics in the pulse fluidized bed 2 is 40s to 30min, preferably 5 to 15min, and a better cleaning effect can be achieved under a shorter cleaning time. The cleaning time study based on uniform airflow can reveal the relationship between pulse airflow and different cleaning times.

[0164] It can be seen from Examples 1, 3, and 4 that the cleaning effects of the 4-filament PE plastic film, the 10-filament PET plastic film, and the mixed plastic film measured by weight are 99.8%, 97.2%, and 98.0%, respectively; and the cleaning effects of the 4-filament PE plastic film and the 10-filament PET plastic film measured by spectral method are 97.34% and 94.18%, respectively, all of which achieve relatively high cleaning effects, indicating that relatively high cleaning effects can be achieved under this equipment and process.

[0165] The cleaning effect of the weight method in Example 1 is 99.8%, which is close to the effect of 99.91% in Comparative Example 1. The cleaning effect of the spectral method in Example 1 is 97.34%, which is better than the cleaning effect of 77.65% in Comparative Example 1. This shows that the dry cleaning of the device and process can achieve an effect comparable to that of wet cleaning, and does not require water cleaning, which can meet the cleaning requirements of thin film plastics in water-scarce areas.

[0166] The effects of the gravimetric method in Example 1 and Example 6 are similar, while the effects of the spectral method are quite different. At this time, the pollutants on the plastic surface have been basically removed, while the fine dust adsorbed on the plastic surface affects the cleaning effect in the spectral method. Therefore, the gravimetric method indicators cannot well evaluate the cleaning effects of the two processes. On the basis of comparing the gravimetric method indicators, the cleaning effect can be further evaluated by comparing the spectral method indicators.

[0167] Due to equipment limitations, the pulse amplitude will also change when the pulse frequency changes. According to Example 1 and Example 6, the pulse frequency and pulse amplitude of the pulse airflow have a certain influence on the cleaning effect of waste plastics. Under the conditions of the pulse frequency of the pulse fluidized bed being 1 Hz, the pulse amplitude being 0.25 m / s, and the pulse frequency being 1.66 Hz, and the pulse amplitude being 0.15 m / s, the dry cleaning system of the present invention can play a good cleaning role, and when the pulse frequency of the pulse fluidized bed is 1 Hz and the pulse amplitude is 0.25 m / s, the particle fluidization effect is better, the interaction between the cleaning medium and the plastic is stronger, and the cleaning effect is better. The cleaning effects calculated by the weight method and the spectral method both reach more than 97%.

[0168] Although the present invention has been described in detail above by means of general description, specific implementation methods and tests, it is obvious to those skilled in the art that some modifications or improvements may be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A dry cleaning system for waste plastics, characterized in that: include: A blower device (1) for providing a pulsed airflow; A pulse fluidized bed (2) for cleaning waste plastics, comprising a tank body (21) and an air chamber (22) detachably connected to the bottom thereof, the tank body (21) being provided with a gas outlet (23) and a feeding port (24), the air chamber (22) being provided with a gas inlet (25) connected to the blast device (1), the tank body (21) being filled with sand and gravel, and the air chamber (22) being disassembled to serve as a discharge port for cleaning waste plastics and sand and gravel; A dust removal device (3) connected to the gas inlet (25) of the pulse fluidized bed (2) and used for removing dust from the gas discharged from the pulse fluidized bed (2); And a screening device (5) for screening the cleaned waste plastics and sand and gravel.

2. A dry cleaning system for waste plastics according to claim 1, characterized in that: The specific conditions of the pulse airflow provided by the blowing device (1) are: surface wind speed of 0.5-0.9 m / s, pulse frequency of 1-4 Hz, pulse amplitude of 0.1-0.4 m / s, temperature of 15-35°C; the cleaning time of waste plastics in the pulse fluidized bed is 40s-30min.

3. A dry cleaning system for waste plastics according to claim 1, characterized in that: The waste plastics include film plastics, hard plastics and plastic particles, wherein the film plastics have a size of 20 to 40 mm.

4. A dry cleaning system for waste plastics according to claim 1, characterized in that: The sand and gravel filled in the tank body (21) include quartz sand particles with a particle size of 0.1 to 0.5 mm, and the mass ratio of the waste plastic to the sand and gravel is 1:250 to 1000.

5. A dry cleaning system for waste plastics according to claim 1, characterized in that: The air blowing device (1) comprises a high-pressure blower (11) for generating a high-pressure pulse airflow, and a heater (12) for controlling the air temperature of the pulse airflow.

6. A dry cleaning system for waste plastics according to claim 1, characterized in that: The tank body (21) comprises a reaction section (211), an expansion section (212) and an outlet section (213) which are sequentially connected from bottom to top; A vertically arranged agitator (26) is arranged in the tank body (21); A gas distribution plate (27) is provided between the gas chamber (22) and the reaction section (211); The gas outlet (23) is arranged in the reaction section (211), and the feed port (24) is arranged in the outlet section (213).

7. A dry cleaning system for waste plastics according to claim 1, characterized in that: A plurality of pressure measuring points (28) and a plurality of temperature measuring points (29) are arranged on the side of the pulse fluidized bed (2).

8. A dry cleaning system for waste plastics according to claim 1, characterized in that: The dust removal device (3) comprises a bag dust collector, a cyclone dust collector or an electric dust collector.

9. A dry cleaning system for waste plastics according to claim 1, characterized in that: The dry cleaning system also includes a control device (4) connected to the blowing device (1), the pulse fluidized bed (2), and the dust removal device (3), and the control device (4) is PLC controlled.

10. A dry cleaning method for waste plastics, which is implemented by using the dry cleaning system according to any one of claims 1 to 9, characterized in that: The dry cleaning method comprises the following steps: S1. Pre-treatment: air-dry the waste plastics and cut them into specific sizes; S2, adjustment: adding sand and waste plastics into the pulse fluidized bed (2); S3, cleaning: controlling the pulse frequency and pulse amplitude of the pulse airflow in the blowing device (1) so that the sand and gravel in the pulse fluidized bed (2) are in a fluidized state to clean the waste plastics; S4, separation: the blowing device (1) is closed, the waste plastics and sand and gravel are discharged from the tank body (21), and then screened through the screening device (5) to obtain clean waste plastic products and sand and gravel.

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