Separation equipment

This chapter provides a very elementary overview of the engineering basics of four important mass separation techniques. Fundamental concepts are stressed rather than actual equipment, largely because equipment and applications are often specific as opposed to off-the-shelf or standardized designs. The techniques are based on widely different separation techniques than those that rely on physical means, such as filtration, settling, centrifugation, and others. Physical separation technologies and equipment are discussed in Chapter 6. The subject matter treated presently is 

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On a land site where space and weight are not normally constraints, advantage can be taken of tank type separation equipment such as wash tanks and settling tanks, and batch processing methods. Such equipment is generally cheaper to maintain than continuous throughput vessels, though a combination of both may be required. 

The natural process of bringing particles and polyelectrolytes together by Brownian motion, ie, perikinetic flocculation, often is assisted by orthokinetic flocculation which increases particle coUisions through the motion of the fluid and velocity gradients in the flow. This is the idea behind the use of in-line mixers or paddle-type flocculators in front of some separation equipment like gravity clarifiers. The rate of flocculation in clarifiers is also increased by recycling the floes to increase the rate of particle—particle coUisions through the increase in soUds concentration. 

The hydrocyclone, commonly referred to simply as cyclone, is a nonmechanical sedimentation-type classifier (2,6,10,27) (Fig. 7). It has no moving parts or power attachments directly connected to it. The hydrocyclone has become the workhorse of most mineral processing operations because of its simplicity, short residence time, compactness, and low cost of operation. It is, however, characterized by lack of sharpness of separation. Equipment... 

D. R. Bennett and co-workers, Cyogenic Air Separation Equipment Design, AIChE Tutorial on Cryogenic Technology, Houston, Tex., 1993. 

Another furnace that does not require fuel preparation is the stoker boiler, which was used by New York State Electric Gas Corporation (NYSEG) in its TDE tests. At NYSEG, the stoker boiler, which has a 1649°C (3000°E) flame temperature (as does the cyclone boiler), has routinely blended low quaUty coal, and more recently, wood chips with its standard coal to reduce fuel costs and improve combustion efficiency. In the tire-chip tests, NYSEG burned approximately 1100 t of tire chips (smaller than 5x5 cm) mixed with coal and monitored the emissions. The company determined that the emissions were similar to those from burning coal alone. In a second test-bum of 1900 t of TDE, magnetic separation equipment removed metal from the resulting ash, so that it could be recycled as a winter traction agent for roadways. 

The oxide exiting either the Barton or ball mill reactor is conveyed by an air stream to separating equipment, ie, settling tank, cyclone, and baghouse, after which it is stored in large hoppers or dmmmed for use in paste mixing. Purity of the lead feed stock is extremely critical because minute quantities of some impurities can either accelerate or slow the oxidation reaction markedly. Detailed discussions of the oxide-making process and product are contained in references 55—57. 

To reduce catalyst losses even further, additional separation equipment external to the regenerator can be installed. Such equipment includes third-stage cyclones, electrostatic precipitators, and more recentiy the Shell multitube separator, which is Hcensed by the Shell Oil Co., UOP, and the M. W. Kellogg Co. The Shell separator removes an additional 70—80% of the catalyst fines leaving the first two cyclones. Such a third-stage separator essentially removes from the due gas stream all particles greater than 10 p.m (36). 

Clear-Hquor advance reduces the quantity of Hquor that must be processed by soHd—Hquid separation equipment (for example, a filter or a centrifuge). The reduction in Hquor flow through the separation equipment may allow use of smaller equipment for a fixed production rate or increased production through fixed equipment. 

A. Ruston, Selection and Use oJUiquidjSolid Separation Equipment, Institution of Chemical Engineers, 1982. 

Overseas Construction Costs Although Table 9-55 gives location factors for the construction of chemical plants of similar function in various countries at 1993 values, these may vaiy differentially over a period of time owing to local changes in labor costs and productivity. Hence, it is often necessaiy to estimate the various components of overseas construction costs separately. Equipment and material prices will depend on local labor costs and the availability of raw materials. If the basic materials have to be imported, costs in the source area become important and import duties and freight charges must be added. 

Pneumatic-Conveyor Dryers A pneumatic-conveyor dryer consists of a long tube or duct carrying a gas at high velocity, a fan to propel the gas, a suitable feeder for addition and dispersion of particulate solids in the gas stream, and a cyclone collector or other separation equipment for final recoveiy of sohds from the gas. 

Spray dryers may operate under positive, negative, or neutral pressures. In general, pressure drop in a complete system will range from 15 to 50 cm of water, depending on duct size and separation equipment employed. 

Purchas (ed.), Solid/Liquid Separation Equipment Scale-Up, Uplands Press, Croydon, England, 1977.]... 

Assistance in problem definition and in developing a test program should be sought from persons experienced in the field. If your organization has a consultant in separations of this land, by all means m e use of the expertise available. If not, it may be wise to employ an outside consultant, whose special knowledge and guidance can save time, money, and headaches. It is important to do this early after the separation equipment has been installed, there is httle a consultant can do to remedy the sometimes disastrous effects of a poor selection. Often it is best to work with established equipment manufacturers throughout the selection process, unless the problem is unusually sensitive or confidential. Their experience with problems similar to yours may be most helpful and avoid many false starts. 

Particle size distribution (R) Design of separation equipment Toxic hazard Environmental impact Wide range including Microscopy Holography Light scatter Sieving... 

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