Filtration, purification and post-treatment of the

2022-08-14
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Filtration, purification and post-treatment of metal cutting fluid

1 The purification device of cutting fluid

during the use of cutting fluid, due to the mixing of fine chips, grinding debris, grinding wheel dust and other impurities, it seriously affects the surface roughness of the workpiece, reduces the service life of tools and grinding wheels, and accelerates the wear of machine tools and circulating pumps. In addition, due to the oil leakage of the machine tool, the lubricating oil falls into the water-based cutting fluid, making the emulsion produce emulsion. The surfactant in the synthetic fluid acts with the lubricating oil and turns into emulsion, which changes the quality of the water-based cutting fluid, resulting in the decline of cooling performance and shrinkage. 4. The load display is incorrect and the service cycle is short. Therefore, when using cutting fluid, impurities and floating oil must be removed at any time to ensure the quality of coolant circulation

(1) sedimentation and separation device: 1) sedimentation tank, 2) cyclone separator, 3) magnetic separator, 4) floating separator, 5) centrifugal separator, 6) electrostatic separator

(2) medium filtration device: medium filtration is to use porous substances as the filter medium to separate the debris, chips, grinding wheel dust and other impurities in the cutting (grinding) fluid. Whether there is a trend of increase or decrease in some sizes, which shows that the machining conditions are still changing. There are two kinds of filter media: 1) durable, woven with steel wire, stainless steel wire, and plain or twill filter cloth woven with nylon synthetic fiber. These filter media can be cleaned when the screen hole is blocked, and their filtering accuracy depends on the size of the screen hole diameter. When a certain amount of chips are accumulated, their filtering accuracy will be higher. Other filter media such as linoleum, glass fiber combined with compressed materials, its filtering accuracy can reach several microns. 2) Disposable filter media, i.e. discarded after use, include filter paper, felt or gauze, with a filtration accuracy of about 20um-5um. There are other coated filter media such as diatomite and activated earth, whose filtration accuracy can reach 2um-1um, but sometimes extreme pressure additives and other additives are filtered out

filter devices are divided into gravity, vacuum and pressure

2. Waste liquid treatment of cutting fluid

(1) waste liquid treatment of oil-based cutting fluid: Oil-based cutting fluid generally does not stink and deteriorate. The main reasons for replacing cutting fluid are the chemical changes of cutting fluid, the increase of chip mixing, the large amount of machine tool emulsified oil without any side effects, and the mixing of water. The following measures can be taken: 1) improve the purification device of oil-based cutting fluid; 2) Regularly clean the chips of oil-based cutting fluid; 3) Prevent lubricating oil leakage by overhauling the machine tool; 4) Regularly supplement cutting lubricating additives; 5) Heat to remove moisture, add some cutting oil lubricating additives after precipitation and filtration, and then restore the quality and continue to use

the final waste oil treatment of oil-based cutting fluid is generally combustion treatment. In order to save resources, waste oil can also be regenerated

(2) waste liquid treatment of water-based cutting fluid. Waste liquid treatment of water-based cutting fluid can be divided into physical treatment, chemical treatment, biological treatment and combustion treatment. 1) The purpose of physical treatment is to separate the suspended substances in the waste liquid (refer to chips, abrasive powder, oil particles, etc. with particle diameter of more than 10um) from the aqueous solution. There are three ways: degradation separation and floating separation by using the density difference between suspended solids and water, filtration separation by using filter materials, and centrifugal separation by using centrifugal devices. 2) The purpose of chemical treatment is to treat the fine suspended particles or colloidal particles (substances with a particle diameter of 0.um) that have not been separated in physics, or chemically treat the harmful components in the waste liquid to make them harmless. There are four methods: using inorganic coagulants (polyaluminum chloride, bauxite sulfate, etc.) or organic coagulants (polyacrylamide), etc. to promote the formation of fine particles Coacervation of substances such as colloidal particles; Oxidation reduction method that uses oxidants such as oxygen and ozone or electro decomposition oxidation-reduction reaction to treat harmful components in waste liquid; An adsorption method that uses active solids such as activated carbon to adsorb harmful components in waste liquid on the surface of solid input and other processes to achieve the purpose of treatment; It is an ion exchange method that uses ion exchange resin to exchange the harmful components of ionic system in waste liquid to achieve the purpose of treatment. 3) Biological treatment. The purpose of biological treatment is to treat the organic substances (such as organic amines, non-ionic active agents, polyols) in the waste liquid that are difficult to be removed by physical and chemical treatment. The representative methods include bacteria adding sludge method and apron filter bed method. The method of adding bacteria and sludge is to mix the bacteria and sludge (microbial proliferators) with the waste liquid for ventilation, and use microorganisms to decompose and treat the harmful substances (organics) in the waste liquid. The bulk filter bed method uses microorganisms to decompose and treat the organic matter in the waste liquid when the waste liquid flows through the surface of the filter material filled bed (filter bed) covered by microorganisms. 4) Combustion treatment includes direct combustion method and "evaporation concentration method" in which waste liquid is evaporated and concentrated before combustion treatment

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