Cleaning process and cleaning system for plastic recovery production

Abstract

The invention is applied to the technical field of plastic recovery, and discloses a plastic recovery production cleaning system which comprises a pre-sorting table, a crushing module, a hot alkaline water soaking mechanism, a flushing mechanism, a friction cleaning machine, a dehydrator and a dryer. The pre-sorting table is composed of a conveying belt and a sorting table, and the waste plastic is manually sorted and sorted to the conveying belt to be conveyed; and the crushing module consists of a vibration feeder and a crusher. According to the plastic recycling, producing and cleaning system, manual sorting is combined with the conveying belt, large impurities and plastic parts which are not suitable for cleaning and recycling can be effectively removed, a pure raw material basis is provided for follow-up treatment, classified conveying is conducted according to materials, colors and pollution degrees, the follow-up treatment is more targeted, the overall cleaning efficiency is improved, and the labor intensity of workers is lowered. And a vibration feeder in the crushing module is matched with a crusher, so that the waste plastics are crushed into proper granularity, subsequent soaking and cleaning are facilitated, and the treatment uniformity is improved.

Description

Technical Field

[0001] The invention relates to the technical field of plastic recycling, and in particular to a plastic recycling production cleaning process and a cleaning system thereof. Background Art

[0002] As global environmental awareness continues to increase, plastic recycling and reuse has become an important issue. However, there are many problems with the existing plastic recycling and cleaning systems and processes. The pulverization process often results in uneven pulverization particle size, which brings difficulties to subsequent soaking and cleaning. The large difference in size of particles may cause small particles to be over-soaked and large particles to be incompletely cleaned. In addition, the performance of the pulverizing equipment is unstable and prone to failure, affecting production efficiency. The hot alkaline water soaking process has prominent problems. The temperature and concentration control are not accurate, which affects the cleaning effect. The temperature is too low or the concentration is insufficient to effectively remove stains and impurities. Too high or too high may damage the performance of the plastic. The stirring effect is not good, some plastic particles are not fully soaked, the soaking tank has poor thermal insulation performance, heat is easily lost, and energy consumption is increased. In the rinsing process, the pressure and time settings are unreasonable, resulting in unstable cleaning effects, and the pressure is too low. Or the time is too short to wash away the residual alkaline water and stains, too high or too long to waste water resources and may damage the plastic particles, the water tank water recovery and treatment system is not perfect, and the water resources cannot be effectively recycled, the friction cleaning machine design is not optimized, the unreasonable blade shape affects the cleaning effect, the improper size and number of wear-resistant rubber balls reduce efficiency, and cannot be adjusted according to different materials and pollution levels. It lacks specificity, dehydration and drying links, equipment performance is insufficient, the dehydrator filtration area and the number of drainage holes are insufficient, the dehydration effect is not good, the water content is too high, the dryer material tray has poor air permeability, which affects the hot air circulation and reduces the drying efficiency, and there is a lack of real-time monitoring equipment, and the hot air temperature and air volume cannot be automatically adjusted. In summary, the existing plastic recycling production cleaning system and process need to be improved to improve efficiency and quality and achieve efficient recycling of resources. Summary of the invention

[0003] The object of the present invention is to provide a plastic recycling production cleaning process and a cleaning system thereof, so as to solve the problem of poor cleaning effect of the existing process mentioned in the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solutions: a plastic recycling production cleaning system, the cleaning system comprising a pre-sorting table, a crushing module, a hot alkaline water soaking mechanism, a flushing mechanism, a friction cleaning machine, a dehydrator and a dryer;

[0005] Pre-sorting table: It consists of a conveyor belt and a sorting table. It sorts the waste plastics manually and puts them on the conveyor belt for transportation.

[0006] Crushing module: It consists of a vibrating feeder and a crusher. The waste plastics dropped from the vibrating feeder fall into the crusher for crushing;

[0007] Hot alkaline water soaking mechanism: It consists of a soaking tank, a heater, a temperature sensor and a stirrer. The crushed waste plastics fall into the alkaline water in the soaking tank. The heater cooperates with the temperature sensor to heat the alkaline water, and the stirrer stirs the waste plastics to achieve a better soaking effect.

[0008] Flushing mechanism: It is composed of a high-pressure water gun and a water tank. The waste plastics soaked in hot alkaline water are flushed by the high-pressure water gun. A filtering structure is arranged in the water tank to circulate and filter the flushing water for use.

[0009] A plastic recycling production cleaning process, the cleaning process comprising the following steps:

[0010] S1. Pre-sorting: Preliminary sorting of recycled plastics to remove larger impurities, such as stones, metals, etc., as well as plastic parts that are obviously not suitable for cleaning and recycling. After sorting, the plastics are classified according to material, color and degree of contamination and placed on different conveyor belts for transportation;

[0011] S2. Crushing: crush the sorted plastics into smaller particles with a particle size of 3-10 mm;

[0012] S3, hot alkaline water soaking: the crushed plastic particles are soaked in a hot alkaline water solution, the concentration of the alkaline water is 5%-10% by mass, the temperature is controlled at 60℃-80℃, and the soaking time is 30-60 minutes;

[0013] S4, first rinse: the soaked plastic particles are taken out from the hot alkaline aqueous solution and rinsed for the first time with a high-pressure water gun at a pressure of 2-3 MPa for 5-10 minutes;

[0014] S5, friction cleaning: the plastic particles after the first rinse are sent to a friction cleaning machine for friction cleaning, the cleaning time is 20-30 minutes, and the speed of the cleaning machine is 500-800 rpm;

[0015] S6. Second flushing: After friction cleaning, the plastic particles are flushed again with a high-pressure water gun at a flushing pressure of 1.5-2MPa for 3-5 minutes;

[0016] S7, dehydration and drying: the washed plastic particles are sent to a dehydrator for dehydration, and then the dehydrated plastic particles are sent to a dryer for drying at a temperature of 80°C-100°C until the water content of the plastic particles drops below 0.5%.

[0017] Preferably, in the pre-sorting step:

[0018] All stones with a diameter greater than 2 cm were removed;

[0019] Magnetic metals in metal impurities are removed by magnet adsorption, and non-magnetic metals are thicker than 1mm and larger than 2cm in area. 2 removal of;

[0020] All plastic parts that are not suitable for cleaning and recycling are removed, including severely aged, deformed and irreversible plastic parts and plastic parts containing hazardous substances.

[0021] Preferably, in the pulverizing step:

[0022] PE and PP plastics, the crushing particle size is controlled at 4-8mm;

[0023] For PVC and PS plastics, the particle size is controlled at 3-6mm.

[0024] Preferably, in the hot alkaline water soaking step:

[0025] The alkaline water formula includes sodium hydroxide, sodium carbonate, and sodium silicate;

[0026] The concentration of alkaline water is monitored in real time by an online concentration monitor. When the concentration is lower than the set lower limit, alkaline solution is automatically added, and when the concentration is higher than the set upper limit, clean water is automatically added.

[0027] The PID temperature control system is used to achieve a temperature control accuracy of ±1°C for alkaline water, and multiple temperature sensors are set at different locations in the soaking tank;

[0028] Add a thermal insulation layer to the soaking tank. The thermal insulation layer material is polyurethane foam with a thickness of 5-8cm.

[0029] Use a variable frequency agitator, with a stirring speed of 80-100 rpm in the initial stage of soaking and reduced to 30-50 rpm in the later stage of soaking.

[0030] Preferably, in the first flushing step:

[0031] The high-pressure water gun nozzle adopts an adjustable design, which can adjust the spray angle and water flow shape according to the shape and accumulation of plastic particles and increase the moving track of the high-pressure water gun;

[0032] The water after the first flushing is collected through the recovery tank of the water tank, and is initially treated by sedimentation, filtration, etc., and then further purified by the reverse osmosis membrane. After meeting the water quality standards, it can be reused in the hot alkaline water soaking tank or other links with lower water quality requirements.

[0033] Preferably, in the friction cleaning step:

[0034] The blade shape of the friction cleaning machine is designed to be a curved spiral. The size and number of wear-resistant rubber balls are determined according to the volume of the cleaning machine and the amount of plastic particles. The diameter of the rubber balls is 3-5cm, and the number is 50-80 per cubic meter of cleaning machine space. Raised rubber strips are added to the inner wall of the friction cleaning machine.

[0035] Adjust the speed and cleaning time of the cleaning machine according to different plastic materials and pollution levels. For lightly polluted plastic particles, the speed is 400-600 rpm and the cleaning time is 15-20 minutes. For heavily polluted plastic particles, the speed is 600-800 rpm and the cleaning time is 25-30 minutes.

[0036] Vibration sensors and overload protection are installed to monitor the cleaning process.

[0037] Preferably, in the second rinsing step:

[0038] The flushing pressure is adjusted according to the material of the plastic particles and the cleanliness after the first flushing. For PE and PS, the flushing pressure is 1-1.5MPa, and for PP and PVC, the flushing pressure is 1.5-2MPa.

[0039] Install online monitoring equipment to observe the turbidity of flushing water in real time. When the turbidity reaches the set standard, stop flushing;

[0040] Add ultraviolet sterilization equipment in the water tank and regularly test the water quality in the tank, including indicators such as pH, hardness, and microbial content.

[0041] Preferably, in the dehydration and drying step:

[0042] The dehydrator uses a high-efficiency centrifugal dehydrator, increases the internal filtration area and the number of drainage holes, and installs automatic balancing and overload protection equipment;

[0043] A multi-layer material tray is set inside the dryer, and the tray is made of stainless steel mesh with good air permeability;

[0044] Install humidity sensors and temperature sensors to monitor the humidity and temperature in the dryer in real time, and automatically adjust the hot air temperature and air volume according to the moisture content of the plastic particles and the drying progress.

[0045] Compared with the prior art, the beneficial effects of the present invention are: the plastic recycling production cleaning system:

[0046] 1. Through manual sorting combined with conveyor belts, large impurities and plastic parts that are not suitable for cleaning and recycling can be effectively removed, providing a pure raw material basis for subsequent processing. The materials are classified and transported according to the material, color and degree of contamination, making the subsequent processing more targeted and improving the overall cleaning efficiency. The vibration feeder and crusher in the crushing module cooperate to crush the waste plastic into a suitable particle size, which is convenient for subsequent soaking and cleaning, and improves the uniformity of processing;

[0047] 2. Utilize the synergistic effect of the heater, temperature sensor and stirrer to accurately control the temperature and concentration of alkaline water to ensure the soaking effect. At the same time, adjust the stirring speed at different stages to further improve the cleaning quality. With two flushing steps, the high-pressure water gun combined with the adjustable nozzle and the moving track can accurately flush according to the situation of the plastic particles. Through the filtration and purification of the water tank, the water can be recycled, saving resources while ensuring the flushing effect;

[0048] 3. The friction cleaning machine adjusts the speed and cleaning time according to different materials and degrees of pollution, and cooperates with curved spiral blades, wear-resistant rubber balls and inner wall rubber strips to greatly improve the cleaning effect. At the same time, the high-efficiency centrifugal dehydrator increases the filtration area and the number of drainage holes, and cooperates with the multi-layer breathable tray and humidity and temperature sensors in the dryer to automatically adjust the hot air temperature and air volume, ensuring that the plastic particles reach the ideal moisture content and improving the quality of recycled plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a schematic diagram of the system composition of the present invention;

[0050] Figure 2 It is a schematic diagram of the process flow of the present invention. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] See also Figure 1-Figure 2 , the present invention provides a technical solution: a plastic recycling production cleaning system.

[0053] Embodiment 1

[0054] Recycled plastics: The main recycled products are some common PE (polyethylene) and PP (polypropylene) plastic products, such as plastic bottles, plastic barrels, etc. The degree of pollution of these plastic products is relatively light, mainly some dust and a small amount of label residues and other common stains.

[0055] Specific operation process:

[0056] Pre-sorting: On the pre-sorting table, stones with a diameter greater than 2 cm are carefully removed manually, and magnetic metal impurities are removed by magnet adsorption. For non-magnetic metals, the thickness is greater than 1 mm and the area is greater than 2 cm. 2 The plastic parts that are severely aged, deformed and cannot be restored to their shape, as well as plastic parts containing harmful substances are also removed, and then the PE and PP plastics are placed on different conveyor belts for transportation according to their materials.

[0057] Crushing: The sorted plastics are sent to the crushing module. Since they are PE and PP plastics, the crushing particle size is controlled at 4-8mm.

[0058] Soaking in hot alkaline water: Put the crushed plastic particles into a hot alkaline water solution. The alkaline water formula contains sodium hydroxide, sodium carbonate and sodium silicate. The mass fraction of the alkaline water concentration is set to 8%. It is monitored in real time by an online concentration monitor. The temperature is controlled at 70°C. The PID temperature control system is used to ensure that the temperature control accuracy reaches ±1°C. Multiple temperature sensors are set at different positions in the soaking tank. A 6 cm thick polyurethane foam insulation layer is added to the soaking tank. A variable frequency agitator is used. The stirring speed is 90 rpm in the initial soaking stage and reduced to 40 rpm in the later soaking stage. The soaking time is 45 minutes.

[0059] First rinse: The soaked plastic particles are fished out and rinsed for the first time with a high-pressure water gun. The nozzle of the high-pressure water gun adopts an adjustable design. The spray angle and water flow shape are adjusted according to the shape and accumulation of the plastic particles. The flushing pressure is 2.5MPa and the flushing time is 8 minutes. The flushing water is collected through the recovery tank of the water tank, and after preliminary treatment such as sedimentation and filtration, it is further purified by the reverse osmosis membrane and then reused in the hot alkaline water soaking tank.

[0060] Friction cleaning: The plastic particles after the first rinse are sent into the friction cleaning machine. Because the degree of pollution is relatively light, the speed of the cleaning machine is set to 500 rpm and the cleaning time is 20 minutes. The blade shape of the friction cleaning machine is a curved spiral. The diameter of the wear-resistant rubber ball is 4 cm. 60 balls are placed in every cubic meter of the cleaning machine space. Raised rubber strips are added to the inner wall of the friction cleaning machine. Vibration sensors and overload protection are installed to monitor the cleaning process.

[0061] Second flushing: After friction cleaning, the plastic particles are flushed again with a high-pressure water gun. Since they are PE and PP plastics, the flushing pressure is 1.2MPa. Online monitoring equipment is installed to observe the turbidity of the water after flushing in real time. When the turbidity reaches the set standard, the flushing is stopped, ultraviolet disinfection equipment is added to the water tank, and the water quality in the water tank is regularly tested, including indicators such as pH, hardness, and microbial content.

[0062] Dehydration and drying: The rinsed plastic particles are sent to a high-efficiency centrifugal dehydrator for dehydration. The dehydrator increases the internal filtration area and the number of drainage holes, and is equipped with automatic balancing and overload protection equipment. The dehydrated plastic particles then enter the dryer. A multi-layer material tray is set in the dryer. The tray is made of stainless steel mesh with good air permeability. Humidity sensors and temperature sensors are installed to monitor the humidity and temperature in the dryer in real time. The hot air temperature and air volume are automatically adjusted according to the moisture content and drying progress of the plastic particles. Drying is carried out at a temperature of 90°C until the moisture content of the plastic particles drops below 0.5%.

[0063] Embodiment 2

[0064] Situation of recycled plastics: Among the recycled plastics, some are PVC (polyvinyl chloride) and PS (polystyrene) plastic products, such as plastic pipes, plastic foam boards, etc., and the degree of pollution is relatively serious, and there may be impurities such as oil, glue, etc.

[0065] Specific operation process:

[0066] Pre-sorting: On the pre-sorting table, larger impurities such as stones with a diameter greater than 2 cm are removed according to the requirements. Magnetic metals are removed by magnet adsorption, and non-magnetic metals with a thickness greater than 1 mm and an area greater than 2 cm are removed. 2 Plastic parts that are not suitable for cleaning and recycling, such as severely aged, deformed and irreversible plastic parts and plastic parts containing harmful substances, are all removed. Then PVC and PS plastics are classified according to material, color and degree of contamination and placed on the conveyor belt.

[0067] Crushing: Crushing the sorted plastics. Because they are PVC and PS plastics, the crushing particle size is controlled at 3-6mm.

[0068] Soaking in hot alkaline water: Put the crushed plastic particles into a hot alkaline water solution. The alkaline water formula remains unchanged, the mass fraction of the alkaline water concentration is 6%, and the temperature is controlled at 75°C. The alkaline water concentration is monitored in real time by an online concentration monitor. When the concentration is lower than the set lower limit, alkaline solution is automatically added. When the concentration is higher than the set upper limit, clean water is automatically added. The PID temperature control system is used to make the alkaline water temperature control accuracy reach ±1°C. Multiple temperature sensors are set at different positions in the soaking tank. A 7cm thick polyurethane foam insulation layer is added to the soaking tank. A variable frequency agitator is selected. The stirring speed is 85 rpm in the initial soaking stage and reduced to 35 rpm in the later soaking stage. The soaking time is 50 minutes.

[0069] First rinse: Take out the soaked plastic particles from the hot alkaline aqueous solution and rinse them for the first time with a high-pressure water gun. The nozzle of the high-pressure water gun can adjust the spray angle and water flow shape. The flushing pressure is 2.8MPa and the flushing time is 9 minutes. The water tank collects the flushing water. After sedimentation, filtration, reverse osmosis membrane purification and other treatments, it can be reused in other links with lower water quality requirements.

[0070] Friction cleaning: The plastic particles after the first rinse are sent into the friction cleaning machine. Due to the heavy pollution, the speed of the cleaning machine is set to 700 rpm and the cleaning time is 28 minutes. The blades of the friction cleaning machine are curved spirals, and the diameter of the wear-resistant rubber balls is 4.5 cm. 70 balls are placed in every cubic meter of the cleaning machine space. Raised rubber strips are added to the inner wall of the friction cleaning machine, and vibration sensors and overload protection devices are installed.

[0071] Second flushing: After friction cleaning, the plastic particles are flushed again with a high-pressure water gun. Because they are PVC and PS plastics, the flushing pressure is 1.8MPa. Online monitoring equipment is installed to observe the turbidity of the water after flushing. When the turbidity reaches the standard, the flushing is stopped. Ultraviolet sterilization equipment is added to the water tank and the water quality of the water in the water tank is tested regularly.

[0072] Dehydration and drying: The rinsed plastic particles are sent to a high-efficiency centrifugal dehydrator for dehydration. The dehydrator increases the internal filtration area and the number of drainage holes and is equipped with automatic balancing and overload protection equipment. The dehydrated plastic particles enter the dryer. The dryer is equipped with a multi-layer stainless steel mesh tray with good air permeability, and a humidity sensor and a temperature sensor are installed to monitor the humidity and temperature in the dryer in real time. The plastic particles are dried at a temperature of 95°C until the moisture content of the plastic particles drops below 0.5%.

[0073] Embodiment 3

[0074] Situation of recycled plastics: The types of recycled plastics are relatively complex, including PE, PP, PVC, PS and other plastics, and the degree of pollution varies. Some plastics have serious stains and impurities.

[0075] Specific operation process:

[0076] Pre-sorting: Operate on the pre-sorting table in strict accordance with the standards, remove all kinds of impurities and plastic parts that are not suitable for recycling, and classify plastics of different materials, colors and contamination levels and place them on the conveyor belt.

[0077] Crushing: Crushing is carried out according to different plastic materials. The particle size of PE and PP plastics is controlled at 4-8mm, and the particle size of PVC and PS plastics is controlled at 3-6mm.

[0078] Soaking in hot alkaline water: The alkaline water formula remains the same. The mass fraction of the alkaline water concentration is adjusted between 5% and 10% according to the contamination of different batches of plastics. The temperature is controlled between 65℃ and 80℃. The soaking time is selected between 30-60 minutes according to the degree of contamination of the plastics. Online concentration monitors, PID temperature control systems, multiple temperature sensors, etc. are used to ensure precise control of the alkaline water concentration and temperature. A 5-8cm thick insulation layer is added to the soaking tank. A variable frequency agitator is used to adjust the stirring speed according to the soaking stage.

[0079] First flushing: adjust the spray angle and water flow shape of the high-pressure water gun nozzle according to the shape and accumulation of the plastic particles. The flushing pressure is adjusted between 2-3MPa and the flushing time is 5-10 minutes. The flushing water is collected in the water tank and reused after sedimentation, filtration, reverse osmosis membrane purification and other treatments.

[0080] Friction cleaning: According to different plastic materials and pollution degree, adjust the rotation speed and cleaning time of the friction cleaning machine. For lightly polluted plastic particles, the rotation speed is 400-600 rpm and the cleaning time is 15-20 minutes; for heavily polluted plastic particles, the rotation speed is 600-800 rpm and the cleaning time is 25-30 minutes. The blades of the friction cleaning machine are curved spirals. The diameter of the wear-resistant rubber balls is 3-5cm, and the number is determined according to the volume of the cleaning machine and the amount of plastic particles. Raised rubber strips are added to the inner wall, and vibration sensors and overload protection devices are installed.

[0081] Second flushing: The flushing pressure is adjusted according to the material of the plastic particles and the cleanliness after the first flushing. The flushing pressure of PE and PS is 1-1.5MPa, and the flushing pressure of PP and PVC is 1.5-2MPa. Install online monitoring equipment to monitor the turbidity of the water after flushing, add ultraviolet disinfection equipment in the water tank and test the water quality regularly.

[0082] Dehydration and drying: Use a high-efficiency centrifugal dehydrator for dehydration. The dehydrator increases the internal filtration area and the number of drainage holes and installs automatic balancing and overload protection equipment. A multi-layer stainless steel mesh tray is set in the dryer, and humidity sensors and temperature sensors are installed. The hot air temperature and air volume are automatically adjusted according to the moisture content and drying progress of the plastic particles. Drying is carried out at a temperature of 80℃-100℃ until the moisture content of the plastic particles drops below 0.5%.

[0083] The following are the final cleaning effect test data of the three embodiments

[0084] Example 1 Test data (mildly contaminated PE and PP plastic products)

[0085] 1. Appearance cleanliness:

[0086] Residual stains: 100 cleaned plastic particles were randomly selected for inspection, and it was found that only 2 plastic particles had slight stains with a diameter of less than 2mm on the surface, and there were no obvious visible stains on the surfaces of the remaining plastic particles. The residual stain rate was 2%.

[0087] Impurity removal: Through the screening method, the cleaned plastic particles were screened using a sieve with a pore size of 1mm. No impurities with a diameter greater than 1mm were found, indicating that the removal effect of larger impurities was good.

[0088] 2. Chemical residues:

[0089] Alkali residue detection: The acid-base titration method was used to detect the alkali residue on the surface of the plastic particles. The average alkali residue was 0.03%, which met the requirements for alkali residue in subsequent processing.

[0090] 3. Physical properties:

[0091] Moisture content: The moisture content of the plastic particles was tested using a moisture meter. The average moisture content was 0.3%, which met the requirement that the moisture content of the plastic particles after drying must be reduced to below 0.5%.

[0092] Particle size distribution: After the crushing and cleaning process, the particle size of the plastic particles was tested again, and it was found that the particle size distribution was in the range of 4-8mm, which was consistent with the set crushing particle size control standard, indicating that the cleaning process had no significant effect on the particle size.

[0093] Example 2 Test data (moderately contaminated PVC and PS plastic products)

[0094] 1. Appearance cleanliness:

[0095] Residual stains: 80 plastic samples were selected for inspection, and it was found that 5 plastic samples had some stains on the surface that were difficult to clean, but the diameter of the stains was less than 5mm. The residual stain rate was 6.25%. Compared with lightly contaminated plastics, moderately contaminated plastics had relatively more residual stains, but overall it was still within an acceptable range.

[0096] Impurity removal: Using a sieve with a pore size of 1mm for screening, occasionally a very small amount of fine impurities will be found to remain, but the number of these impurities is very small, with the weight of impurities in every 100g of plastic particles being less than 0.05g, which has little impact on subsequent processing.

[0097] 2. Chemical residues:

[0098] Alkali residue detection: The acid-base titration test results showed that the average alkali residue was 0.05%, which was slightly higher than that of lightly contaminated plastics, but still within an acceptable range and would not have adverse effects on the subsequent use of the plastics.

[0099] 3. Physical properties:

[0100] Moisture content: The average moisture content detected by the moisture meter is 0.4%, which meets the drying requirements.

[0101] Particle size distribution: The particle size after crushing is controlled within the range of 3-6mm, which meets the crushing particle size requirements of this type of plastic.

[0102] Example 3 Test data (heavily contaminated mixed plastic products)

[0103] 1. Appearance cleanliness:

[0104] Residual stains: 120 plastic samples were randomly selected, of which 10 samples had obvious stains on their surfaces, with a residual stain rate of 8.33%. These stains were mainly oil stains and pigments with strong adhesion, and some of them still remained after cleaning, but the remaining stain area was relatively small.

[0105] Impurity removal: Screening tests found that the weight of impurities in every 100g of plastic particles is about 0.1g. The impurities mainly include some fine fibers and dust. Compared with lightly and moderately contaminated plastics, impurity removal is more difficult, but the overall impurity content is still within an acceptable range.

[0106] 2. Chemical residues:

[0107] Alkali residue detection: The average alkali residue is 0.08%. Since heavily contaminated plastics require longer cleaning and processing, the alkali residue is relatively high, but still within a reasonable range.

[0108] 3. Physical properties:

[0109] Moisture content: The average moisture content is 0.45%, slightly higher than lightly and moderately contaminated plastics, but still meets the dryness standard.

[0110] Particle size distribution: Since it is a mixed plastic, the particle size distribution of different plastics is different, but overall it is within the required particle size range. The particle size of PE and PP is 4-8mm, and the particle size of PVC and PS is 3-6mm.

[0111] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention are included in the protection scope of the present invention.

Claims

1. A plastic recycling production cleaning system, characterized in that: The cleaning system includes a pre-sorting table, a crushing module, a hot alkaline water soaking mechanism, a flushing mechanism, a friction cleaning machine, a dehydrating machine and a drying machine; Pre-sorting table: It consists of a conveyor belt and a sorting table. It sorts the waste plastics manually and puts them on the conveyor belt for transportation. Crushing module: It consists of a vibrating feeder and a crusher. The waste plastics dropped from the vibrating feeder fall into the crusher for crushing; Hot alkaline water soaking mechanism: It consists of a soaking tank, a heater, a temperature sensor and a stirrer. The crushed waste plastics fall into the alkaline water in the soaking tank. The heater cooperates with the temperature sensor to heat the alkaline water, and the stirrer stirs the waste plastics to achieve a better soaking effect. Flushing mechanism: It is composed of a high-pressure water gun and a water tank. The waste plastics soaked in hot alkaline water are flushed by the high-pressure water gun. A filtering structure is arranged in the water tank to circulate and filter the flushing water for use.

2. A plastic recycling production cleaning process according to claim 1, characterized in that: The cleaning process includes the following steps: S1. Pre-sorting: Preliminary sorting of recycled plastics to remove larger impurities, such as stones, metals, etc., as well as plastic parts that are obviously not suitable for cleaning and recycling. After sorting, the plastics are classified according to material, color and degree of contamination and placed on different conveyor belts for transportation; S2. Crushing: crush the sorted plastics into smaller particles with a particle size of 3-10 mm; S3, hot alkaline water soaking: the crushed plastic particles are soaked in a hot alkaline water solution, the concentration of the alkaline water is 5%-10% by mass, the temperature is controlled at 60℃-80℃, and the soaking time is 30-60 minutes; S4, first rinse: the soaked plastic particles are taken out from the hot alkaline aqueous solution and rinsed for the first time with a high-pressure water gun at a pressure of 2-3 MPa for 5-10 minutes; S5, friction cleaning: the plastic particles after the first rinse are sent to a friction cleaning machine for friction cleaning, the cleaning time is 20-30 minutes, and the speed of the cleaning machine is 500-800 rpm; S6. Second flushing: After friction cleaning, the plastic particles are flushed again with a high-pressure water gun at a flushing pressure of 1.5-2MPa for 3-5 minutes; S7, dehydration and drying: the washed plastic particles are sent to a dehydrator for dehydration, and then the dehydrated plastic particles are sent to a dryer for drying at a temperature of 80°C-100°C until the water content of the plastic particles drops below 0.5%.

3. A plastic recycling production cleaning process according to claim 2, characterized in that: In the pre-sorting step: All stones with a diameter greater than 2 cm were removed; Magnetic metals in metal impurities are removed by magnet adsorption, and non-magnetic metals are thicker than 1mm and larger than 2cm in area. 2 removal of; All plastic parts that are not suitable for cleaning and recycling are removed, including severely aged, deformed and irreversible plastic parts and plastic parts containing hazardous substances.

4. A plastic recycling production cleaning process according to claim 2, characterized in that: In the comminution step: PE and PP plastics, the crushing particle size is controlled at 4-8mm; For PVC and PS plastics, the particle size is controlled at 3-6mm.

5. A plastic recycling production cleaning process according to claim 2, characterized in that: In the hot alkaline water soaking step: The alkaline water formula includes sodium hydroxide, sodium carbonate, and sodium silicate; The concentration of alkaline water is monitored in real time by an online concentration monitor. When the concentration is lower than the set lower limit, alkaline solution is automatically added, and when the concentration is higher than the set upper limit, clean water is automatically added. The PID temperature control system is used to achieve a temperature control accuracy of ±1°C for alkaline water, and multiple temperature sensors are set at different locations in the soaking tank; Add a thermal insulation layer to the soaking tank. The thermal insulation layer material is polyurethane foam with a thickness of 5-8cm. Use a variable frequency agitator, with a stirring speed of 80-100 rpm in the initial stage of soaking and reduced to 30-50 rpm in the later stage of soaking.

6. A plastic recycling production cleaning process according to claim 2, characterized in that: In the first flushing step: The high-pressure water gun nozzle adopts an adjustable design, which can adjust the spray angle and water flow shape according to the shape and accumulation of plastic particles and increase the moving track of the high-pressure water gun; The water after the first flushing is collected through the recovery tank of the water tank, and is initially treated by sedimentation, filtration, etc., and then further purified by the reverse osmosis membrane. After meeting the water quality standards, it can be reused in the hot alkaline water soaking tank or other links with lower water quality requirements.

7. A plastic recycling production cleaning process according to claim 2, characterized in that: In the friction cleaning step: The blade shape of the friction cleaning machine is designed to be a curved spiral. The size and number of wear-resistant rubber balls are determined according to the volume of the cleaning machine and the amount of plastic particles. The diameter of the rubber balls is 3-5cm, and the number is 50-80 per cubic meter of cleaning machine space. Raised rubber strips are added to the inner wall of the friction cleaning machine. Adjust the speed and cleaning time of the cleaning machine according to different plastic materials and pollution levels. For lightly polluted plastic particles, the speed is 400-600 rpm and the cleaning time is 15-20 minutes. For heavily polluted plastic particles, the speed is 600-800 rpm and the cleaning time is 25-30 minutes. Vibration sensors and overload protection are installed to monitor the cleaning process.

8. A plastic recycling production cleaning process according to claim 2, characterized in that: In the second washing step: The flushing pressure is adjusted according to the material of the plastic particles and the cleanliness after the first flushing. For PE and PS, the flushing pressure is 1-1.5MPa, and for PP and PVC, the flushing pressure is 1.5-2MPa. Install online monitoring equipment to observe the turbidity of flushing water in real time. When the turbidity reaches the set standard, stop flushing; Add ultraviolet sterilization equipment in the water tank and regularly test the water quality in the tank, including indicators such as pH, hardness, and microbial content.

9. A plastic recycling production cleaning process according to claim 2, characterized in that: In the dehydration and drying step: The dehydrator uses a high-efficiency centrifugal dehydrator, increases the internal filtration area and the number of drainage holes, and installs automatic balancing and overload protection equipment; The dryer is equipped with multi-layer material trays, which are made of stainless steel mesh with good air permeability; Install humidity sensors and temperature sensors to monitor the humidity and temperature in the dryer in real time, and automatically adjust the hot air temperature and air volume according to the moisture content of the plastic particles and the drying progress.

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