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Air filter structure principle
Air filter structure principleThe air filter is a device that captures dust from the gas-solid two-phase flow and purifies the gas through the action of porous filter materials. It purifies the air with low dust content and sends it into the room to ensure the process requirements of the clean room and the air cleanliness in the general air-conditioned room.The air filter (AirFilter) refers to an air filtration device, that is generally used in clean workshops, clean factories, laboratories, and clean rooms, or for dust prevention of electronic machinery and communication equipment. There are primary filters, medium-efficiency filters, high-efficiency filters, and sub-high-efficiency models. Various models have different standards and usage efficiency. In pneumatic technology, air filters, pressure-reducing valves, and oil misters are called the three major pneumatic parts. To obtain multiple functions, these three air source processing components are often assembled in sequence, which is called a pneumatic triple. It is used for air source purification, filtration, pressure reduction, and lubrication. The installation order of the three major parts are air filter, pressure reducing valve, and oil mister according to the air intake direction. The three major components are indispensable air source devices in most pneumatic systems. They are installed near the air-using equipment and are the final guarantee of compressed air quality. In addition to ensuring the quality of the three major components themselves, their design and installation must also consider factors such as space-saving, easy operation and installation, and arbitrary combination. Classification (1) Coarse filter The filter material of the coarse filter is generally non-woven fabric, metal wire mesh, glass fiber, nylon mesh, etc. Commonly used coarse filters include ZJK-1 automatic winding herringbone air filter, TJ-3 automatic winding flat air filter, CW air filter, etc. Its structural forms include plate type, folding type, belt type, and winding type. (2) Medium filter Commonly used medium filters include M-I, II, IV foam plastic filters, YB glass fiber filters, etc. The filter materials of medium filters mainly include glass fiber, medium-fine pore polyethylene foam plastics, and synthetic fiber felt made of polyester, polypropylene, acrylic, etc. (3) High efficiency filter Commonly used high-efficiency filters include GB type and GWB type. The filter material is ultra-fine glass fiber filter paper with very small pores. A very low filtration rate is used, which enhances the screening and diffusion of small dust particles, so it has a very high filtration efficiency. (1) Foam plastic filter Foam plastic filter uses polyethylene or polyester foam plastic as the filter layer. The foam plastic is chemically treated in advance to penetrate the internal pore film so that it has a series of interconnected pores. When dust-laden air passes through, the air is purified due to inertia and diffusion. Its pore size is generally 200~300μm. It can be divided into box-type foam plastic filters and rolled foam plastic filters. The thickness of the foam plastic layer is generally 10~15μm, and the final resistance is 200Pa. (2) Fiber-filled filter Fiber-filled filter consists of a frame and filter material and uses fibers of different coarseness and fineness as fillers, such as glass fiber and synthetic fiber (polystyrene). The filler should be selected according to the purification efficiency and resistance requirements. The filling density has a great influence on the efficiency and resistance. Commonly used glass fiber filters have a fiber filler layer with wire mesh on both sides. Each unit consists of two filter blocks. Dust particles enter the unit from the middle and are purified by the filter layers on both sides. (3) Fiber felt filter uses non-woven fabric (felt) made of various fibers (such as polyester, nylon, etc.) as filter material, generally made into bag type or winding type. Bag-type fiber filters use non-woven filter material to make folded or V-shaped filter bags, with high purification efficiency, and are often used as medium-efficiency filters; automatic winding filters use foam plastic or non-woven filter material as filter material. Each roll of filter material is 20m long. The filter consists of an upper box, a lower box, a cabinet, a material barrier, a transmission mechanism, and a filter material roll. After the filter material accumulates dust, it can be automatically rolled up and updated. When the entire roll of filter material is dusty, it can be removed and replaced. It is often used as a coarse-effect air filter with a filtration wind speed of 0.8~2.5m/s and a final resistance of 90~100Pa. There are two forms of constant pressure control and timing control. (4) Paper filter uses plant cellulose filter paper, blue asbestos fiber filter paper, and ultra-fine glass fiber filter paper as filter material. The filter paper can be made into a foldable type to increase the filter area. The filter end frame and the filter paper must be sealed with sealant. The filter area of each unit is 12m3, the rated air volume is 1000m3/h, and the initial resistance is 200~250Pa. It should be protected by coarse and medium-efficiency air filters in front. (5) Electrostatic filter The electrostatic filter uses the electricity generated by the electric field to separate dust particles from the airflow. It adopts a dual-zone structure, consisting of a charging zone and a dust collection zone. The charging zone is a series of streamlined cylindrical grounding electrodes installed in parallel at equal distances. Corona wires are installed between the columns. The corona wires are connected to the positive electrode. The discharge electrode voltage is 10~20kV. The dust-collecting electrode in the dust-collection zone is made of aluminum plates. The distance between the plates is about 10mm. The inter-electrode voltage is 5~7kV. A uniform electric field is formed between the plates. Dust particles obtain positive ions in the charging zone and then enter the dust collection zone. Positively or negatively charged dust is respectively deposited on the plates with opposite polarity. The dust particles on the plates need to be washed off regularly with water or oil. Application The purpose of the air filter is to obtain clean air that meets the standards. Generally, ventilation filters are used to capture and adsorb dust particles of different particle sizes in the air to improve air quality. In addition to adsorbing dust, chemical filters can also adsorb odors. They are usually used in biopharmaceuticals, hospitals, airport terminals, human settlements, etc. The general purpose of ventilation filters is quite extensive, and they are needed in the microelectronics industry, coating industry, food and beverage industry, etc. In other words, the filter is just a means to achieve the goal of cleanliness. |
