Use of Cyclones

An inert force commonly employed in separating solids particles from a gas stream is the centrifugal force. Cyclones and air classifiers represent techniques that make use centrifugal force as a means of performing separation. Air classification may be considered an analytical technique with some industrial applications, while cyclonic separation constitutes one of the most useful industrial operations to treat dust-laden air and gases in a number of processes and applications. 

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Dust Separation It is usuaUy necessaiy to recover the solids carried by the gas leaving the disengaging space or freeboard of the fluidized becl GeneraUy, cyclones are used to remove the major portion of these sohds (see Gas-Sohds Separation ). However, in a few cases, usuaUy on small-scale units, filters are employed without the use of cyclones to reduce the loading of solids in the gas. For high-temperature usage, either porous ceramic or sintered metal has been employed. Multiple units must be provided so that one unit can be blown back with clean gas while one or more are filtering. 

The use of cyclone separators for the removal of suspended dust particles from gases is discussed in Section 1.6. By suitable choice of operating conditions, it is also possible to... 

In this section, the general design of the hydrocyclone and its application in the grading of solid particles, or their separation from a liquid, is considered and then the special features required in hydrocyclones required for the separation of immiscible liquids will be addressed. The use of cyclones for separating suspended particles from gases is discussed in Section 1.6.2. 

Feed Solids Content. A good HMS plant operation keeps the medium as free of fines as possible by effective screening of the heavy-media separation vessel feed. Reduced fines reduce viscosity problems in the medium and result in sharper separation of sink and float products. It also improves magnetic recovery on the magnetic drum separators and gives a cleaner magnetic concentrate. The use of cyclones in the HMS circuit, either as the heavy-media separation vessel or as a densifier for rinse or wash water, increases the solids content and must be evaluated in selecting the media recovery wet dmm separators for plants in which cyclones are used. 

MSC Air-Pollution-Control Systems MSCs generate flue gas that contains particulates, acid gases and trace amounts of organic and volatile metals. Particulates have traditionally been removed Dy use of cyclone separators and electrostatic precipitators. Acid gases require neutralization and removal from the gas stream. This can be accomplished by adding solutions or chemicals to the gas stream and removing the products of the chemical reaction when these materials are mixed together. Two major types of APCs are employed ... 

Collection of powder from an airstream is a large subject of its own. In spray drying, dry collection of powder in a nondestructive way is achieved by use of cyclones, filters with textile bags or metallic cartridges, and electrostatic precipitators. 

A preferred configuration for the study of kinetics in such systems would be a CSTR with both gas and liquid feed and a dispersed catalyst bed. The catalyst must be removed from the effluent stream, a problem best solved when the effluent stream is adequately large to allow the use of cyclone separators. Reactions of this type present a major challenge to the reactor designer and the lack of adequately designed standard experimental reactors for such studies has held back kinetic investigations of these systems. 

Surface moisture is related to the amount of available surface and the wettability of the coal but moisture contents are lower than might be expected from the available surface area because of the low wettability of coal compared with the surfaces of minerals. Surface moisture can be removed from washed higher-rank (bituminous and anthracite) coals by drainage on a screen while the dewatering of washed small coal or coal fines can be accomplished by the use of cyclones or centrifuges. If the moisture content must be reduced to lower levels, there are two alternate methods which involve the use of rotary kilns or fluidized bed dryers. But, such dried coal will reabsorb moisture on exposure to the atmosphere which may give rise to fire hazards as well as explosion hazards. 

The use of cyclones or other separators, in the sampling mode, for on-line particle size measurement is now well established in both dry and wet applications . This involves taking a continuous sample stream through a small cyclone or hydroclone under a given set of operating conditions, and monitoring the recovery of the cyclone. The task of particle size measurement is thus reduced to measurement of solids concentrations in two material streams. 

Catalytic attrition and entrainment represent a problem in bubbling flui-dized-bed reactor, limiting the range of flow rate and dictates the use of cyclones. In the suggested fast fluidization (transport) reformer, the solid movement is exploited to the maximum limit in an integrated circulating configuration. 

Use of cyclonic devices, or flow through a narrow gap to separate gases from liquids, or to remove particles... 

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