Sepration Techniques Used In Industies

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Sepration Techniques used in Industries Made By Aakshat Kumar Rohilla

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Separation Science & technology Reviewing its past to map out of its future Separation technology is fundamental to all chemical production processes. The separation techniques used are common to a range of industries and are continuously developing. As with cross-industry best practice, the application of processes and developments in one industry can find applications in another, which may be completely unrelated. SCI’s Separation Science and Technology .Group aims to promote this and to provide a forum for information exchange across the industrial and academic spectrum.

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Separation Processes Based on Magnetic and Electric Forces Solids can be classified as ferromagnetic, paramagnetic, or diamagnetic. Relatively few are ferromagnetic, but those that are respond to magnetic force so strongly that magnetic separation is the most common and efficient method for separating them. The ferromagnetic class includes iron and most steels, some other metals, and a few minerals, such as magnetite. The separation environment can be wet or dry, and the equipment is designed to lift the ferromagnetics out of mixtures. Permanent magnets can be used, but most industrial processes employ electromagnets. Paramagnetic materials exhibit some susceptibility to magnetic force, but it is much weaker than for ferromagnetic. This difference dictates that much stronger magnets be used and that equipment be designed to minimize the "air gap" over which the field must operate. Capacities would also be lower because the weaker forces require longer separation times. Nevertheless, paramagnetic separations are very widely used, and major advances have been made in both magnet strength and equipment design. Cryogenic magnets are being used more widely, and equipment is designed for optimally configured field gradients. A vivid example is provided by the machines used to separate paramagnetic iron minerals from kaolin slurries intended for use in making very high quality paper. The magnetic force is so weak that time must be allowed for the iron-bearing particles to overcome the drag forces of water. High gradients are achieved by using stainless-steel wool as a secondary magnet in a field generated by a powerful cryogenic magnet.

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Magnetic separation does not depend on the electrical conductivity of the material being treated; in fact, many conductors are diamagnetic. Because they are conductors, some materials experience a force when passed through a variable magnetic field due to the generation of eddy currents, which are induced in conductive particles as a result of time dependent variations of a magnetic field. Eddy currents, in turn, interact with the magnetic field to generate repulsive forces, the magnitude of which are related to the conductivity, shape, mass, and size of the particles and the intensity of the magnetic field. Eddy current separators are based on either rotating disc permanent magnets or linear motor electromagnets for the generation of time dependent magnetic fields. The particles are passed through the magnetic field and physically separated according to the degree of thrust exerted on individual particles by the magnetic field. This method is now used for certain industrial separations, the separation of various nonferrous metals from the product of shredding old white goods and automobiles, for example, and the separation of aluminum cans from mixed packaging materials. Electrical separations take advantage of charges, either natural or induced, on solid particles. In a simple form, particles passed between two oppositely charged plates are attracted or repelled according to their own charges and can thereby be separated. This technique is called electrostatic separation because the charge relationships are not changed. In electrodynamic separation, however, charged particles brought into contact with a grounded drum lose their charges at different rates and are repelled more or less strongly, which is the basis for the separation.

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CROSS-CUTTING SEPARATION ISSUES Conclusions and Recommendations Separation processes are essential elements of the technological foundations of the seven IOF industries included in this report. For the chemical and petroleum refining industries, separation processes are used to separate and purify the products of reactions. For the aluminum, steel, and metal casting industries, separation processes are used, among other things, to purify molten metal and to sort scrap. For the glass industry, separation processes are essential to the recycling of preand postconsumer cullet, and for the forest products industry, separations are involved in nearly all process steps of pulping and papermaking. In addition to the importance of separation technologies in industrial processes, separation processes also present opportunities for waste reduction and more efficient use of energy and raw materials. New developments in separation technologies are, therefore, critical for the continued productivity and global competitiveness of these industries.

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Separation Processes for the Chemical and Petroleum Refining Industries The chemical and petroleum refining industries have a number of separation issues in common. In addition to general improvements in process efficiency, the panel identified two separation technology areas with the potential to meet some of the needs of both industries: separation methods that use multiple driving forces, including processes in which a naturally occurring driving force for a specific operation is enhanced by an intervention that changes the system thermodynamics or in which two or more separation techniques are coupled (combined membrane separations and distillation; affinity-based adsorbent separations; and electrically aided separations) separations associated with chemical reactions, in other words, methods that combine reaction and separation in one process step (reactive metal complex sorbents and chemically facilitated transport membranes; coupled chemical synthesis and separation processes; membrane reactors; and electrochemical methods of separation)

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