The principle of electrostatic adsorption
When an object with static electricity is close to another object without static electricity, due to electrostatic induction, the inside of the object without static electricity will be close to the side with static electricity. The accumulation of charges with the opposite polarity to the charge carried by the charged object (the same number of charges of the same polarity is generated on the other side), because the charges of the opposite sex attract each other, it will show the phenomenon of "electrostatic adsorption".
Application of electrostatic adsorption
The static electricity generated by the electrostatic generator is applied to the object to be adsorbed, and the object is immediately charged with static electricity and adsorbed on the object, making the original unevenness like the surroundings Upwardly uneven objects such as non-woven cloth, paper, etc. can be smoothly absorbed on metal plates, wood boards, etc. after adding static electricity for the next step. This method is used in steel production, wood production and mold industries. Wide range of applications.
Using an electrostatic generator to apply static electricity to an object to produce adsorption has many applications in other industries. When using it, the output of the electrostatic generator can be adjusted according to the situation to adjust the size of the adsorption force.
The EST series electrostatic generator has a protection circuit, which can protect the output in the event of a short circuit accidentally. At the same time, it can also protect the operator from improper use and will not cause safety problems for human life due to high voltage static electricity.
This kind of electrostatic generator usually does not need very high precision or very high voltage. Therefore, according to different situations, choose the low-priced EST801 electrostatic generator (0-8kv) or JDF-1 electrostatic The generator (0-80kV) is sufficient. Of course, if economic conditions are possible, the use of a high-precision electrostatic generator can better ensure the effect and quality.
Purification and regeneration of waste lubricating oil based on electrostatic adsorption technology
Electrostatic adsorption device
Using an electrostatic generator connected to the electrode to generate a high-voltage electrostatic field to make the oil Pollutants are polarized to show positive and negative electricity respectively. By controlling and adjusting the intensity of the high-voltage electrostatic field, the charged pollutants move in opposite directions under the action of the electric field. The neutral particles are squeezed and moved by the stream of charged particles, and finally All impurities, including solid particles, water, colloid and gas, are adsorbed on the adsorption material, so as to achieve the purpose of high purification.
Electrostatic adsorption and regeneration of waste lubricating oil process
1. Pre-treatment of waste lubricating oil
Waste lubricating oil has a certain viscosity change after use. It will affect the subsequent processing process. In order to reduce the difficulty of processing and increase the processing speed during the processing, the waste lubricating oil is heated in the early stage. According to Stokes's law, the formula (1) is obtained:
W = D(d1-d2) /18η (1)
where: W is the sedimentation velocity of the particles, m·s-1; D is the particle diameter, m; d1 is the particle density, kg·m-3; d2 is the oil density, kg·m- 3; η is the absolute viscosity of the oil at the settling temperature, kg·(m2·s)-1.
From the formula, we can see that the higher the viscosity, the slower the sedimentation speed. Appropriate heating can reduce the oil viscosity and increase the sedimentation speed. However, if the temperature is too high, it will cause the oxidation of the oil. Therefore, an appropriate heating temperature should be selected in the early stage.
2. Treatment of waste lubricating oil moisture and mechanical impurities
Lubricating oil will invade moisture and produce mechanical impurities due to various reasons during use. The lubricating oil that invades moisture will deteriorate the oil quality and reduce the performance of the lubricating oil; the simultaneous presence of mechanical impurities and moisture will not only produce a catalytic effect in the oil, but also affect the subsequent electrostatic adsorption function. The moisture content of the waste lubricating oil used in the electrostatic adsorption device is required to be below 0.05%. Therefore, it is necessary to deal with mechanical impurities and moisture in the early stage.
3. Treatment process of waste lubricating oil
Figure 2 is the process flow of treating waste lubricating oil based on electrostatic adsorption technology.
The waste lubricating oil in the waste lubricating oil tank is transported to the vacuum dehydration device ZK through the pre-filter device YL through the feed pump B1, and the waste lubricating oil is dehydrated. The vacuum dehydration device is set to vacuum It is -0.08MPa. In the meantime, the waste lubricating oil is heated in two stages, the first stage heating temperature is 50℃, and the second stage heating temperature is 70℃. Studies have proved that the pressure and temperature will not affect the effective components of the waste lubricating oil, and the dehydration effect is obvious. The oily wastewater is finally collected, condensed, and left for standing treatment. The oil and water are collected in FY. After condensing and standing treatment, the oil moisture is 2 layers, the lower layer is water, the upper layer is oil, and the middle is open. The water can be directly used as condensed water for recycling or flocculation treatment After it is discharged directly, the upper layer oil can be collected and processed again. In order to improve the purification and regeneration effect, strengthen the electrostatic adsorption device to capture small pollutants, and exert the adsorption capacity and pollution holding capacity of micro water, colloid and gas. It is transported by the discharge pump to the filter device for parallel three-stage filtration. The first and second-stage filters are bag filters
DS1 and DS2 are used for filtration. The filter screens are 300 mesh and 200 mesh, respectively. Filter the larger particles and impurities in the waste lubricating oil, and the three-stage filter is the electrostatic adsorption device JD. The processing time of each level is controlled by EVB1, EVB2 and EVB3 electric valves. In order to improve the processing speed and effect of subsequent electrostatic adsorption, the waste lubricating oil has been continuously recycled for many times. After pre-filtration-vacuum dehydration-three-stage parallel filtration of waste lubricating oil, the moisture content in the lubricating oil is reduced to less than 0.05%, and the dirt and impurities with larger particles are filtered. After electrostatic adsorption, the oil in the sub-micron level The dirt and impurities are treated by adsorption. The filter screen of the bag filter can be reused after backwashing; after the adsorption plate is powered off, the debris will fall off due to gravity and be discharged from the drain hole. After the quick connector is opened, it can be carefully cleaned. The oily waste residue after treatment can be harmlessly incinerated.
The entire process is automatically controlled, and the processing devices of each processing link are equipped with automatic pressure alarm devices. When the pressure difference is too large, it can automatically alarm, indicating that the filter bag or the electrostatic adsorption device needs to be replaced Sewage treatment.
Application and improvement in the field of film stretching
Principle of electrostatic adsorption
The attached sheet of electrostatic adsorption device is commonly used in the production of flat film stretching technology The attached sheet method is particularly suitable for the stretching process of producing PET (polyester), PA (nylon) and other materials. Its function is to make the cast sheet and the quench roll closely contact, and prevent the rapid rotation of the quench roll from entraining air to ensure transmission. Heat and cooling effect. The electrostatic adsorption device is composed of a metal wire electrode (0.15～0.18mm molybdenum wire or tungsten wire), a high-voltage generator and an electrode wire crimping motor. Its working principle is: using the direct current voltage of thousands to tens of thousands of volts (6-12k V) generated by the high-voltage generator to make the electrode wire and the casting roll become the negative electrode and the positive electrode respectively (the casting roll is grounded), and the high voltage of the film is here. Due to electrostatic induction in the electrostatic field, an electrostatic charge with the opposite polarity to the casting roll is carried. Under the action of the attraction of opposite sexes, the film and the surface of the quench roll are closely adsorbed together to achieve the purpose of eliminating air and uniformly cooling the film. Since the electrode wire is easy to absorb the volatiles of the membrane material during the production process and affect the adsorption effect, the electrostatic wire must be designed to move at a certain speed to keep the electrode wire updated in real time. The electrostatic adsorption device is mainly composed of the following parts: wire electrode wire take-up end, wire electrode wire discharge end, high voltage generator, three-dimensional position adjustment mechanism and other related components.
The structure and improvement of the electrostatic adsorption device
The following focuses on the structure and improvement process of the electrostatic adsorption device.
1. The structure and working principle of the electrostatic adsorption device
The electrostatic wire (0.15～0.18mm molybdenum wire or tungsten wire) is connected to the high voltage power supply (6～12k V), Driven by the servo motor at the take-up end, the take-up wheel at the take-up end is rolled into the take-up reel at the take-up end at a slow speed (about 0.5m～1m/min). In order to keep the electrostatic wire straight, the electrostatic wire needs to maintain a certain tension. Through the three-dimensional adjustment mechanism, the electrostatic wire and the casting roll are kept in the correct working position.
2. Improvement of the damping device
The damping device provides suitable and stable tension for the static wire to maintain a straight working state. The following two devices that provide tension for the winding are now carried out Compare.
1) Permanent magnet hand-adjustable tension damper
In order to make the electrostatic adsorption wire always in a tight state without being broken, it needs to be set up between the retracting and unwinding reels A certain tension, the initial design is to install a permanent magnet brake on the unwinding shaft, the tension of the static wire can be judged based on experience to manually adjust the brake torque, but as the outer diameter of the unwinding wheel decreases, the static electricity The tension of the wire is also attenuated. In this way, the permanent magnet brake must be frequently adjusted. This design not only increases the labor intensity of the operator, but also puts forward higher requirements for the operator's operating experience.
2) Hysteresis automatic tension damper
In view of the many shortcomings of permanent magnet manual tension dampers, we replaced the permanent magnet brake with a hysteresis brake, which can be adjusted by current Torque, and install a tension sensor on the take-up end, set the tension on the host computer, and according to the set tension, the system automatically adjusts the current of the hysteresis brake, and closes the loop to control the torque to achieve the effect of automatic tension adjustment. The improved electrostatic wire runs smoothly, the tension remains basically constant, and the adhesion effect is significantly improved.
3. Improvement of the winding wheel arranging mechanism
The static wire must walk at a very slow speed while discharging static electricity to achieve the purpose of real-time update. This process It is realized by the take-up end servo motor to drive the take-up wheel to rotate. The outer diameter×inner diameter×height of the take-up wheel is: Φ90×Φ60×15; if the static wire is always wound at a position of the width of the take-up wheel, it will inevitably form a sharp point, which will easily cause collapse and cause the tension of the static wire Instantaneous fluctuations will affect the attachment effect, and even cause the electrostatic wire to contact the diaphragm to discharge and break down the diaphragm. Therefore, an electrostatic wire arranging device must be designed at the take-up end so that the electrostatic wire is in the width direction of the take-up wheel. Orderly arrangement, which is very beneficial to the stability of the tension of the electrostatic wire. We have also made many improvements to the arranging mechanism of the electrostatic wire to form today's design effect. The following is the improvement process.
1) The bevel gear drive guide wheel travel line
The initial design is to install a bevel gear pair on the winding spindle, and the bevel gear pair drives the rotation of the camshaft. The vertical reversing movement, through the movement of the cam pair, drives the guide wheel on the linear guide rail to reciprocate up and down, so as to achieve the orderly arrangement of the electrostatic wire on the take-up wheel. Through the practice of the production process, it was found that there are many defects in the above design. First, the installation accuracy of the complex structure is difficult to guarantee; second, due to the limitation of the structure, the speed ratio of the bevel gear cannot be very large (currently 1:2). After turning for 2 weeks, the guide wheel will travel for a cycle, which will not only cause the tension of the static wire to fluctuate, but also the excessively large wire gap, which causes the take-up wheel gap to be too large, and the take-up wheel is replaced too frequently.
2) Reciprocating threaded guide wheel wiring
In order to simplify the structure, we draw lessons from the wiring mechanism of the wire production industry, and use the grooved cylinder with reciprocating threads as the guide wheel to achieve static electricity. The arrangement of the wire on the take-up wheel. Although the structure is greatly simplified, the outer diameter of the grooved barrel cannot be large in diameter due to the limitation of the structure, and the reciprocating thread is also difficult to achieve a multi-turn structure, and the above defects cannot be effectively overcome.
3) Worm drive sheave mechanism take-up wheel swimming arranging line
Through the defect analysis of the above two arranging mechanisms, we have identified two key issues that need to be broken through: One is that the guide wheel swimming is a forced winding, which will cause the tension of the static wire to fluctuate; if the speed of the second winding is too close to the rotation speed of the take-up wheel, it will cause the winding gap to be too large, and the static wire will be retracted. The gap on the wire wheel is too large, and the take-up wheel is replaced too frequently. Grasping the above key points, our R&D has a clear direction. By referring to similar mechanisms (fishing rod reel, etc.), we have designed a third set of solutions: the main drive shaft is designed as a spline shaft, and the spline shaft A single-head worm is set on the top, and an eccentric roller is installed on the end surface of the worm gear matched with the worm. The eccentric roller drives the sliding body on the linear guide to move up and down. The sliding body is equipped with a dial mechanism, which is driven by the dial to cooperate with the spline shaft. The spline sleeve reciprocates, and the take-up wheel rigidly connected with the spline sleeve reciprocates at the same time. Since the guide wheel does not reciprocate, and the movement of the take-up wheel will not cause the forced movement of the electrostatic wire, and the electrostatic wire can be neatly arranged in the width space of the take-up wheel, and it will not cause static electricity. The tension of the silk fluctuates violently, so the first problem is solved. As for the second question, because it is a worm gear drive, which is characterized by a large speed ratio, we mentioned earlier that the height of the take-up wheel is 15mm; the diameter of the electrostatic wire is 0.15～0.18mm; we will arrange the gap of the electrostatic wire Set to 0.2mm, so that the width of the take-up wheel is full: 15mm/0.2mm=75 turns; that is to say, the take-up wheel rotates 75 revolutions, and it moves for one cycle from upstream to downstream, that is, a worm wheel equipped with an eccentric roller Rotate 1/2 circle; in this way, we calculate that the transmission ratio of the worm gear needs to be 1:150 (75×2), so that every 150 revolutions of the take-up wheel (worm), the worm wheel rotates once, and the eccentric roller on the worm wheel has a cycle. It can be known from the speed ratio that the number of teeth of the worm wheel needs 150 teeth, and the index circle diameter of the worm wheel with a modulus of 1 is d=m×z=150×1=φ150mm. Due to space constraints, the outer diameter of the worm wheel is best limited to φ60mm. We take the worm gear indexing circle diameter d=φ58, the number of teeth z=58, the outer diameter φ60mm, and the speed ratio=1:58, that is, the worm wheel rotates 0.5 times and the take-up wheel is filled with a height, 58/2=29 turns, inverse calculation , The electrostatic wire spacing is approximately equal to 0.5mm. In this way, the arrangement gap of the electrostatic wire is greatly reduced, and the efficiency of the use of the take-up wheel is effectively improved.