Solids dewatering

Cone classifier (N-S) Similar to cylindrical tank classifier, except tank is conical to eliminate need for rake. 0.6 to 3.7 600 im to 45 im (6 mm) 2 to 100 Not critical 5 to 30. 35 to 60 None Low cost (simple enough to he made locally), and simplicity can justify relatively inefficient separation. Used for desliming and primary dewatering. Solids buildup can be a problem. 

Important auxiliary equipment in a flotation plant includes feeder and controls, sampling and weighing devices, slurry pumps, filter and thickeners for dewatering solids, reagent storage and makeup equipment, and analytical devices for process control. 

Metals precipitated with chemicals are removed by settlement in a basin. Because industrial metals removal processes frequently include filtration, basin effluent passes through a rudimentary filter of straw, conventional filters being considered impractical for unattended operation at a site lacking electricity. Also, provision is made to spray neutralized effluent upstream of the basin to strip carbon dioxide that may inhibit flocculation by depressing the pH,11 as ample hydraulic head is available at the site. Dewatered solids would be placed in a mine cavity. 

Purpose (circle those which apply) recover solids, dewater solids, wash solids, classify solids, recover liquor, clarify liquor, separate 2 liquids,... 

It is more efficient to mechanically dewater solids than thermally, due... 

So far the major consfiaint in the application of multiple-effect evaporation to industrial drying has been the decreasing fluidity of the processed material in the course of water evaporation. The use of oil as a carrier medium, which is the essence of the Carver-Greenfield process, solved this problem, allowing this energy-efficient method to be used to dewater solids in the process stream to virtually zero moisture content. 

In most cases, the percent solids content of a dewatered solids is set by the requirements for subsequent treatment and disposal. Each treatment technology has an optimum range of percent solid, above or below which the technology will not operate efficiently and economically, if at all. For example, combustion requires that the solid content be greater than 24 %, preferably in foe 28-30 % range for more economical operation. Particulates will vary in percent sohd depending on foe technology and application. 

A Japanese firm, Kuri Chemical Engineers, has a vertical screw press, with the dewatered solids discharging at the bottom. A scraper part of the screw leaves a thin heel of cake which acts as a precoat, which is either formed directly from the process slurry or from a filter aid such as diatomite. The filtration screen (wedge wire screen of 25 pm aperture) is cleaned automatically by back-washing. The tests reported were with potassium chloride crystals in a solution of PVC in acetone, and with activated carbon in an aqueous solution of alanine. Particle size ranged from 1 to 100 pm. 

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