Solids discharge

For estimating purposes for direct-heat drying applications, it can be assumed that the average exit-gas temperature leaving the sohds bed wih approach the final solids discharge temperature on an ordi-naiy unit carrying a 5- to 15-cm-deep bed. Calculation of the heat load and selec tion of an inlet-air temperature and superficial velocity (Table 12-32) will then permit approximate sizing, provided an approximation of the minimum required retention time can be made. 

Solids Discharge The type of discharge mechanism utilized is dependent upon the necessity of sealing the atmosphere inside the fluidized-bea reactor and the subsequent treatment of the sohds. The simplest solids discharge is an overflow weir. This can be used only when the escape of fluidizing gas does not present any hazards due to... 

Either trickle (flapper) or star (rotaiy) valves are effective sealing devices for solids discharge. Each functions with a head of sohds above it. Bottom of the bed discharge is also acceptable via a slide valve with a head of solids. 

FIG. 17-17 Quench tank for overflow or cyclone solids discharge. [Gilfillan et al., "The FluoSolids Reactor as a Source of Sulphur Dioxide, J. Chem. Metall. Min. See. S. Afr. (May 1954).]... 

Table 18-15 summarizes the several types of commercial centrifuges, their manner of liquid and solids discharge, their unloading speed, and their relative volumetric capacity. When either the liquid or the solids discharge is not continuous, the operation is said to be cycHc. Cyclic or batch centrifuges are often used in continuous processes by providing appropriate upstream and downstream surge capacity. 

Method of separation Rotor type Centrifuge type Manner of liquid discharge Manner of solids discharge or removal Centrifuge speed for solids discharge Capacity ... 

Route solid discharge directly into receiver tank... 

Because the radius of the solid discharge port is ususally less than the radius of the liquid overflow at the broader end of the bowl, part of the settled solids is submerged in the pond. 

Cake The solids discharged from a dewatering apparatus. 

A plant produces 100 kg/s of titanium dioxide pigment which must be 99 per cent pure when dried. The pigment is produced by precipitation and the material, as prepared, is contaminated with 1 kg of salt solution containing 0.55 kg of salt/kg of pigment. The material is washed countercurrently with water in a number of thickeners arranged in series. How many thickeners will be required if water is added at the rate of 200 kg/s and the solid discharged from each thickeners removes 0.5 kg of solvent/kg of pigment ... 

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