Filter Pockets Business
Dust removal principle The sedimentation mechanism of dust particles such as inertial collision, diffusion, gravity and electrostatic force is the theoretical basis for analyzing the dust filtration mechanism of f8 bag filter. The dust filtration process of Filter Pockets Business is relatively complicated. Generally speaking, the sedimentation of dust particles on the capture body, that is, separation filtration, is not the result of only one sedimentation filtration mechanism, but the result of the combined action of multiple sedimentation separation filtration mechanisms.
According to the different mechanical properties of the movement of dust of different particle sizes in the fluid, the filtration dust removal mechanism involves the following aspects.
----------------------------Screening effect----------------------------
The filter mesh of the filter is generally 5~50um. When the dust particle size is larger than the mesh or pore diameter or the dust is deposited in the gap between dust particles between the filter materials, the dust is retained. For new fabric filter materials, since the gaps between fibers, that is, the pore size, are much larger than the dust particle size, the screening effect is very small, but when a large amount of dust is deposited on the surface of the fiberglass pocket filter material to form a dust layer, the screening effect is significantly enhanced.
----------------------------Inertial collision effect----------------------------
Generally, dust with larger particle size is mainly captured by inertial collision effect. When the dust-laden airflow approaches the fiber of the filter material, the airflow will bypass the fiber. The larger particles (larger than 1um) will deviate from the airflow streamline due to inertia, continue to move in the original direction of movement, and collide with the fiber and be captured. All large dust particles within the critical line of the dust trajectory can reach the fiber surface and be captured. This inertial collision effect is enhanced as the dust particle size and airflow velocity increase. Therefore, increasing the airflow velocity through the filter material can increase the inertial collision effect.
----------------------------Interception effect----------------------------
When the dust-laden airflow approaches the filter pockets material fiber, the finer dust particles flow around with the airflow. If the dust particle radius is greater than the distance from the dust particle to the fiber edge, the dust particle is intercepted due to contact with the fiber.
----------------------------Diffusion effect----------------------------
For dust particles smaller than 1um, especially submicron particles smaller than 0.2um, they will break away from the streamline under the impact of gas molecules and perform Brownian motion like gas molecules. If they come into contact with the fiber during the movement, they can be separated from the airflow. This effect is called diffusion, which increases with the decrease of flow rate and the decrease of fiber and dust diameter.
----------------------------Electrostatic effect----------------------------
Many fiber-woven filter materials will generate static electricity due to friction when air flows through them. At the same time, dust will be charged due to friction and other reasons during transportation, which will form a potential difference between the filter material and dust particles. When dust moves toward the filter material with air flow, the Coulomb force causes the dust and pocket bag filter material fibers to collide and enhances the adsorption force of the filter pockets material on the dust, so that the dust is captured and the collection efficiency is improved.
----------------------------Gravity sedimentation effect----------------------------
When the slowly moving dust-laden air flow enters the dust collector, dust particles with large particle size and density may naturally settle down due to gravity.
Generally speaking, various dust removal mechanisms are not effective at the same time, but one or several work together. Moreover, with the changes in the gaps in the pocket filter water material, the air flow velocity, the dust particle size and other reasons, the various mechanisms have different effects on the filtration performance of different filter materials. In fact, the dust removal efficiency of new filter materials is very low when they start to filter pockets dust. After a period of use, coarse dust will form a layer of dust on the surface of the pocket filters cloth.
The changes in the gaps of the filter material, air flow velocity, dust particle size and other reasons, various mechanisms have different effects on the filtration performance of different filter materials. In fact, the dust removal efficiency of new filter materials is very low when they start to filter dust. After a period of use, coarse dust will form a layer of dust on the surface of the pocket filters cloth. As shown in Figure 10-2, the dust filtering process of the filter cloth. Due to the dust filtering effect of the dust initial layer and the dust layer gradually accumulated on it, the filtration efficiency of the pocket water purifier material continues to increase, but the resistance is also increased accordingly. When cleaning, the initial layer must not be destroyed, otherwise the efficiency will decrease. The structure of the dust initial layer plays a very important role in the efficiency, resistance and cleaning effect of the bag dust collector.
----------------------------Types and properties of filter pockets insulation fiber materials----------------------------
Asbestos:
Asbestos is a general term for magnesium-containing silicate minerals that can be stripped into flexible and slender fibers. According to the type of mineral, asbestos can be divided into three categories: serpentine asbestos, amphibole asbestos and brucite asbestos. Among them, serpentine asbestos, also known as chrysotile asbestos, is widely used. Asbestos has good thermal insulation, alkali resistance, insulation, corrosion resistance and other properties, and good spinnability. The long-term use temperature of asbestos insulation material is 400℃~450℃, and the short-term use can reach 700cc. Asbestos insulation fiber products can be divided into the following types according to their production process: weaving, such as asbestos yarn, asbestos thread, asbestos rope, asbestos cloth, asbestos tape, asbestos quilt, asbestos clothing, etc.; papermaking, such as asbestos paper, asbestos pad, asbestos insulation board, etc.; molding, such as asbestos calcium silicate board, magnesium carbonate asbestos tube, foam asbestos, etc.; coating, such as asbestos silicate composite coating, asbestos mortar, etc. Since open asbestos and its products can cause damage to human lungs, they have been gradually banned by various countries in recent years.
----------------------------Rockwool----------------------------
Rockwool, also known as rock wool or rock mineral wool, is an inorganic fiber made from natural rocks such as basalt and diabase as basic raw materials, after melting and fiberization. Domestic rock wool felt with phenolic resin as binder (3% to 5%)
The long-term use temperature of rock wool felt is about 400℃. Rock wool is mainly used for building insulation, including wall, roof, door and window, floor insulation, etc. The factory can prefabricate various rock wool sandwich composite panels; industrial insulation, including high-temperature pipes, tanks, boilers, heat exchangers and other equipment; ship bulkheads, etc.
----------------------------Glass wool----------------------------
Glass wool is short glass fiber, which is made of natural minerals such as quartz sand, dolomite, wax stone, etc., with other chemical raw materials such as alkali, boron, etc., and is drawn, blown or thrown in a molten state. It is a fine fibrous material. According to the content of alkali metal oxides in its chemical composition, it can be divided into alkali-free, medium-alkali and high-alkali glass wool; according to the production method, it can be divided into flame glass wool, centrifugal blowing glass wool and steam (or compressed air) vertical blowing glass wool. According to the type of binder, glass wool products can be divided into three types: low temperature, medium temperature and high temperature. For products using resin as a binder, the use temperature should not exceed 200℃, and the use temperature of products without binder or using inorganic binder is about 550℃. There are many varieties of glass fibers. In industrially developed areas, glass wool and its products are a widely used building insulation material, including the insulation of various pipes of heating, water supply, power and other equipment. Among them, glass wool felt is mainly used for building insulation, air conditioning and ventilation equipment insulation, computer room, cold storage insulation, and aircraft, ships, rail vehicles, tunnels and other insulation. Glass wool and its products can also be used for high-temperature gas purification in power plants, cement, petroleum, chemicals, coal, locomotives, etc.
----------------------------Aluminum silicate fiber----------------------------
Aluminum silicate fiber, also known as refractory fiber, can be divided into three types: low-temperature type (<900℃), standard type (>1200℃) and high-temperature type (1400℃～1600℃). Due to the high production cost of aluminum silicate refractory fiber, its current application is mainly in special industrial fields, including the lining of atomic reactors, metallurgical furnaces and petrochemical reaction devices, metal material heat treatment furnaces, and ceramic kilns. In recent years, it has been found that aluminum silicate fiber products will produce harmful substances to the human body due to the change of their crystal phase under long-term high temperature. Therefore, some manufacturers have stopped using this fiber and replaced it with high-silica fiber made of alkali-free glass fiber.
----------------------------Filter Pockets Business Thermal insulation mechanism and influencing factors----------------------------
pocket filters insulation fiber materials are mainly composed of solid matrix and pores, and the solid matrix and pores are continuous phases. The basic ways of heat transfer are mainly heat conduction, heat convection and heat radiation. The thermal insulation mechanism of the material can be explained by the microscopic theory of thermal conductivity. The value of effective thermal conductivity is generally between the thermal conductivity of the solid phase and the thermal conductivity of the gas constituting the insulation material. It depends on the structure of the insulation material, the porosity and the properties of the solid and gas phase materials constituting the insulation material.
Bag filter insulation fiber materials can generally work together on solid phase, gas phase and liquid phase as well as radiation heat transfer. Humidity is a very important factor affecting the thermal conductivity of insulation fiber materials, which is greatly affected by external conditions. Since the thermal conductivity of water is about 25 times that of air, and the thermal conductivity of ice is even greater, the thermal conductivity of the insulation fiber material will increase significantly after absorbing water or moisture. The external conditions for liquid phase heat transfer are the presence of groundwater, rainy and foggy weather, and moisture in the air (i.e., relative humidity of the air), and the internal factors for liquid phase heat transfer are the hygroscopicity of the material itself and the capillary effect of the fiber aggregate. Most insulation fiber materials need to be covered with a layer of aluminum foil to reduce or block the transfer of radiant heat. Under high temperature conditions, there is no wet heat transfer phenomenon. At higher temperatures, part of the solid phase can be directly sublimated into a gas phase.
Bulk density, porosity, and thermal conductivity are the basic parameters of insulation fiber materials. Bulk density refers to the mass of the insulation fiber material per unit volume, and porosity refers to the volume fraction of pores in the entire volume of the insulation fiber material. Controlling the effective thermal conductivity according to the Fourier heat transfer law is one of the main means to optimize the insulation performance of insulation fiber materials. For fibrous thermal insulation materials, there are thermal conductivity parallel to the fiber direction and thermal conductivity perpendicular to the fiber direction, and the former is much larger than the latter. In engineering practice, for the laying of thermal insulation fiber materials for vertical heat dissipation surfaces or vertical heat flow pipes, the laying direction of the fibers needs to be specially designed. Since the release direction of heat flow is vertically upward (the direction of hot and humid air flow), the fibers should be laid not only parallel to the heat dissipation surface, but also parallel to the ground, so that the heat loss direction is as perpendicular to the fiber direction as possible, so that the effective thermal conductivity is reduced. Similarly, for the fiber mesh wrapping of horizontal pipes or the fiber insulation prefabricated parts wrapping, a certain amount of fibers should be kept parallel to the pipe so that the heat loss direction is perpendicular to the fiber direction. In practice, the fiber felts with messy fiber directions are mostly used, between vertical and parallel, and the intermediate value of the thermal conductivity of parallel fiber arrangement and the thermal conductivity of vertical fiber arrangement can be taken, so the impact is not significant.
The factors that affect the thermal conductivity of thermal insulation fiber materials are: first, fiber morphology characteristics, including fiber geometry and pore shape. Fibers with a microporous surface structure have lower thermal conductivity than fibers with a smooth surface. Generally, the smaller the average pore diameter, the smaller the thermal conductivity of the fiber insulation material. In addition, the thinner the fiber, the smaller the thermal conductivity of the fiber insulation material. Second, the porosity. The material should maintain a high and stable porosity, that is, the static air content should be high and stable. Third, the thermal conductivity of the material. Generally, the smaller the ratio of solid-phase to gas-phase thermal conductivity, the better. Fourth, the bulk density. A lighter fiber material with a certain degree of distortion should be selected. In addition, temperature and humidity also affect thermal conductivity.
Keywords: rigid pocket filter | pocket air filter | Filter Pockets Business | air purifier pocket | f8 bag filter | fiberglass pocket filter
