Chemical Engineering License Review, Second Edition
This text contains 146 problems with detailed step-by-step solutions, and is an ideal study guide and the first truly practical, no-nonsense review for the difficult PE Exam.
TABLE OF CONTENTS Chemical Engineering License Review, Second Edition
Chapter 7: Leaching
Leaching calculations can be done by (1) stage-to-stage algebraic calculations using the material balance and equilibrium relationship and (2) graphical methods such as the use of the right triangular, Ponchon-Savarit, or McCabe-Thiele diagram. The multistage countercurrent leaching is the most important and should be reviewed in detail.
Equilibrium Relationship in Leaching
The assumptions generally made to simplify the leaching calculations are as follows: (1) The system consists of three components, a solute, a solvent and an inert solid; (2) the inert solid (solute-free) is insoluble in the solvent, and the flow rate of the inerts from stage to stage is constant; and (3) in the absence of adsorption of the solute by the inerts, an equilibrium is attained on complete solution of the solute in the solvent. The nonequilibrium condition is taken into consideration by an efficiency factor.
If the conditions of equilibrium are met, the concentration of the solution leaving a state is the same as the concentration of the solution adhering to the inerts. The equilibrium relationship is, therefore, x e = y e.
Representation of Equilibrium Data
The published data on a particular system are generally given in terms of the amount of the solution retained by the inerts and the extract composition. These can be used to construct the triangular or Ponchon-Savarit diagram. Example 7-1 illustrates the method of the calculation of the equilibrium data for the triangular diagram.
Example 7-1
The experimental data on the retention of oil by livers are given in...
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