1. The structure of the air filter
The air purification process can be divided into four stages: primary efficiency filtration, medium efficiency filtration, sub-high efficiency filtration, and high-efficiency filtration. The equipment required for each stage is the primary effect filter, medium effect filter, sub-high efficiency filter, and high-efficiency filtration. Device.
(1) Initial filter
The primary effect filter is the first stage of air purification treatment. It mainly filters large particles of dust and various foreign materials. The diameter of trapped particles is 10%. The structure of the main form of two kinds of plate and bag, as shown in Figure 3-14. Due to the large gap of the initial effect filter, the resistance is small and the higher wind speed (0.4 to 1.2) can be used for filtration.
For the convenience of cleaning, the filter material of the primary effect filter generally adopts thick, medium-diameter foamed plastic or non-woven fabric, and can be replaced and cleaned periodically according to the dust concentration of the fresh air imported from the filter, so as to keep the filter resistance low. And higher air intake.
(2) Medium Efficiency Filter
The medium-efficiency filter is mainly used to filter particles with a diameter in the range of 1 to 10. Generally used filter media are washable medium and fine-pore foam plastics, glass fibers, synthetic fibers or non-woven fabrics. The filtration speed of air is 0.2-0.4.
The structure of medium-efficiency filters is mainly wedge-type and bag-type. The medium efficiency filter is often designed in positive pressure before the high efficiency filter to extend the life of the high efficiency filter.
(3) Sub-high efficiency filter
(3) Sub-high efficiency filter
Sub-high-efficiency filter is mainly used to remove dust particles with a diameter of less than 5, widely used in places where the clean level is equal to or less than 100,000, as well as places with high requirements for environmental dust removal and sterilization, and is a terminal filter for 300,000-class clean workshops. . The filter media mainly includes sub-efficient glass fiber filter paper, perchloroethylene fiber filter cloth and polypropylene fiber filter cloth. Its structure is divided, tube, bag type.
(4) High efficiency filter
The high efficiency filter is used to filter out particles smaller than 1 in diameter and can filter 99.97% 0.3 dust particles. It is the final filter for clean workshops and local purification equipment. Its structure is shown in Figure 3-15.
High-efficiency filters are mainly made of ultra-fine glass fiber filter paper or asbestos. They are non-renewable filter media. Therefore, high-efficiency filters must be installed with intermediate or sub-high-efficiency filters for protection.
High-efficiency air filters generally use a folding filter assembly. In order to ensure the filtration efficiency and provide adequate air flow, the high-efficiency filter uses a lower wind speed, the wind speed is maintained at 0.01 to 0.03, and the larger filter area.
2. Air purification process
The composition of the clean room air purification system includes air dust removal system, air disinfection system, and airflow organization system. The main equipment of air purification project consists of induced draft fan, pre-filter, main filter (electrostatic precipitator), ozone sterilization layer, activated carbon filter, negative ion generator and other parts. In addition, to ensure the humidity and temperature in the air, additional heating or cooling, constant humidity and other devices can also be added.
(1) Induced Draft Fans Multi-stage centrifugal fans are generally used, which can ensure the air volume and ensure the pressure, while the noise is small. The use of electrostatic precipitators can also be selected with cross-flow fans.
(2) Pre-filter The primary filter and medium-efficiency filter are designed to remove more than 5 particles in the fresh air and protect the subsequent high-performance filter equipment.
(3) Main filter Removes particles smaller than 1. Choose one of high efficiency filter and electrostatic precipitator. Among them, the proportion of electrostatic dust collectors is 90%.
(4) Ozone sterilization layer The ozone generator generates ozone to sterilize and sterilize the air.
(5) Activated carbon filter After passing through the main filter, it is filtered through the activated carbon column to remove ozone and acid gas, and it can purify the dust, aerosol and steam in the gas.
(6) Negative ion generator The anion generator can negatively charge the particles floating in the air, making these particles easy to be trapped or precipitated, thus making the air in the workshop more fresh. Therefore, most air cleaning systems are equipped with negative ion generators to improve air quality.
