Aspiration and filtration Распечатать

Effectively operating aspiration improves working conditions, increases fire- and explosion safety  of production, helps to increase the yield and improve the quality of products, and protects the atmospheric air from pollution.

In various industries (for example, in the construction materials industry, chemical and mining), dust is understood as a type of aerosol, i.e., a dispersed system consisting of fine solid particles in suspended conditions in a gaseous medium. In the grain processing industry, industrial dust includes small and light organic and inorganic solid particles that are released into the production room from the grain mass during the movement, processing of grain, as well as various bulk feed components. Moreover, dust includes not only particles suspended in the air (aerosol), but also particles deposited on the surface of equipment and building structures of a building (airgel). Particularly large amounts of dust are generated when grain is processed in impact machines, for example, crushing and grinding machines, hammer mills and roller mills. In these machines, soetimes increased explosive dust concentrations can occur, which can be eliminated by aspirating the equipment. Dust, penetrating through leaks in the equipment case into the air of the room, increases its dustiness, worsens human working conditions, reduces labor productivity, increases friction and wear in machines, contributes to the occurrence of fires, dust explosions, etc. Dust in two states: aerosol (suspended) and aerogel (settled), can move from one state to another. From the first state to the second, dust passes under the influence of gravity, as well as electrical or centrifugal forces. From the second state to the first, dust passes under the action of disturbing forces caused by vibration, impacts or air currents. The dust contents depends on its origin. Industrial dust consists of the same products and substances that are processed in this enterprise. Grain dust consists of two parts: mineral and organic. On elevators, dust contains up to 50% mineral particles. Organic dust prevails in grain cleaning departments of flour mills and groats factories (up to 80...95%). In the milling and packing departments of flour mills, all dust is floury, organic. At enterprises for storage and processing of grain, dust by value can be unusable (black) ash content of more than 6.5% (must be destoyed); fodder (gray) ash content 2...6.5% (can be fed to livestock and poultry); food flour (white) with an ash content of less than 2% (used as a food product in the production of second grade flour). Particle sizes vary widely - from from fractions of a micrometer to 250microns. Depending on the particle size, dust is conventionally divided into coarse (50...250 microns), medium (10...50 microns) and fine (less than 10 microns). At elevators and granary, coarse dust prevails, in the grain cleaning departments of flour mills and grain mills - medium dust, in the milling and packing departments of flour mills - fine dust (70-80% with a particle size of less than 3 microns), in the hulling departments of grain mills and feed mills plants - also fine dust. The harmfulness of dust depends on its size and chemical composition. Coarse dust is less dangerous than fine dust, as it is retained during breathing on the mucous membranes of the nose. Fine dust with a particle size of 5...10 microns is the most dangerous for human health. The chemical composition of dust largely determines its harmfulness, which is assessed by the content of silicon dioxide (silica). The cleanliness of the air in the working rooms should be maintained by dust content at a level not exceeding the maximum permissible concentration (MPC): 4 mg/m3 of grain dust and 6mg/m3 of flour. In places of permanent residence of people, the dust content of the air should not exceed 0,5mg/m3 regardless of the type of dust . The permissible concentration of dust when air is released into the atmosphere after cleaning in aspiration and pneumatic conveying installations is determined by calculating air dispersion. One of the main tasks solved with the help of ventilation and aspiration units is to ensure the cleanliness of the air in terms of dust content, which does not exceed these limits. The purity of the air discharged into the atmosphere can be ensured, among other things, by using highly efficient dust collectors (preferably filters).

Effectively operating aspiration improves working conditions, increases fire- and explosion safety of production, helps to increase the yield and improve the quality of products, and protects the atmospheric air from pollution.

In various industries (for example, in the construction materials industry, chemical and mining), dust is understood as a type of aerosol, i.e., a dispersed system consisting of fine solid particles in suspended conditions in a gaseous medium. In the grain processing industry, industrial dust includes small and light organic and inorganic solid particles that are released into the production room from the grain mass during the movement, processing of grain, as well as various bulk feed components. Moreover, dust includes not only particles suspended in the air (aerosol), but also particles deposited on the surface of equipment and building structures of a building (airgel). Particularly large amounts of dust are generated when grain is processed in impact machines, for example, crushing and grinding machines, hammer mills and roller mills. In these machines, sometimes increased explosive dust concentrations can occur, which can be eliminated by aspirating the equipment. Dust, penetrating through leaks in the equipment case into the air of the room, increases its dustiness, worsens human working conditions, reduces labor productivity, increases friction and wear in machines, contributes to the occurrence of fires, dust explosions, etc. Dust in two states: aerosol (suspended) and aerogel (settled), can move from one state . From the first state to the second, dust passes under the influence of gravity, as well as electrical or centrifugal forces. From the second state to the first, dust passes under the action of disturbing forces caused by vibration, impacts or air currents. The dust contents depends on its origin. Industrial dust consists of the same products and substances that are processed in this enterprise. Grain dust consists of two parts: mineral and organic. On elevators, dust contains up to 50% mineral paricles. Organic dust prevails in grain cleaning departments of flour mills and groats factories (up to 80…95%). In the milling and packing departments of flour mills, all dust is floury, organic. At enterprises for storage and processing of grain, dust by value can be unusable (black) ash content of more than 6.5% (must be destoyed); fodder (gray) ash content 2...6.5% (can be fed to livestock and poultry); food flour (white) with an ash content of less than 2% (used as a food product in the production of second grade flour). Particle sizes vary widely - from fractions of a micrometer to 250 microns. Depending on the particle size, dust is conventionally divided into coarse (50...250 microns), medium (10...50 microns), and fine (less than 10 microns). At elevators and granary, coarse dust prevails, in the grain cleaning departments of flour mills and grain mills - medium dust, in the milling and packing departments of flour mills - fine dust (70-80% with a particle size of less than 3 microns), in the hulling departments of grain mills and feed mills plants - also fine dust. The harmfulness of dust depends on its size and chemical composition. Coarse dust is less dangerous than fine dust, as it is retained during breathing on the mucous membranes of the nose. Fine dust with a particle size of 5...10 microns is the most dangerous for human health. The chemical composition of dust largely determines its harmfulness, which is assessed by the content of silicon dioxide (silica). The cleanliness of the air in the working rooms should be maintained by dust content at a level not exceeding the maximum permissible concentration(MPC): 4mg/m of grain dust and 6mg/m3 of flour. In places of permanent residence of people, the dust content of the air should not exceed 0.5mg/m3, regardless of the type of dust. The permissible concentration of dust when air is released into the atmosphere after cleaning in aspiration and pneumatic conveying installations is determined by calculating air dispersion. One of the main tasks solved with the help of ventilation and aspiration units is to ensure the cleanliness of the air in terms of dust content, which does not exceed these limits. Air cleanliness in working rooms (for dustiness) can be ensured by aspiration units by means of effective aspiration of all equipment in which dust is generated. The purity of the air discharged into the atmosphere can be ensured, among other things, by using highly efficient dust collectors (preferably filters).