# LEACHING PRINCIPLES

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```					LEACHING PRINCIPLES
LEACHING PROCESS
DESCRIPTION
• PROCESS TO CONTACT A SOLID WITH A
LIQUID PHASE.
• SIMILAR TO EXTRACTION BECAUSE OF
TWO IMMISCIBLE PHASES
• SIMILAR TO ABSORPTION BECAUSE TWO
PHASES ARE NORMALLY PRESENT
• DISSIMILAR TO OTHERS BECAUSE ONLY
EQUILIBRIUM IN LIQUID PHASES IS
CONSIDERED
LEACHING EQUILIBRIUM
• SOLVENT FORMS A LIQUID SOLUTION -
CARRIER MAY BE TOTALLY IMMISCIBLE
• SOME SOLUTION IS NORMALLY RETAINED
BY THE SOLID - HAS THE SAME
COMPOSITION AS THE LIQUID SOLUTION.
• WHEN THE AMOUNT OF RETAINED
SOLUTION IS CONSTANT THE SYSTEM HAS
CONSTANT SOLUTION UNDERFLOW.
• VARIABLE UNDERFLOW EXISTS WHEN THE
AMOUNT RETAINED IS A FUNCTION OF
CONCENTRATION
TYPICAL EQUILIBRIUM
DIAGRAM
• NOTE THE SOLID PHASE IS
REPRESENTED BY THE UPPER LINE
• SOLUTION EQUILIBRIUM ON McCABE
IS x = y LINE FOR THIS SITUATION
SOLID PHASE

Y=B/(A+C)

LIQUID PHASE

0                                         1
xA, yA
SINGLE STAGE LEACHING

• MODELED LIKE A SINGLE STAGE LLX

xb,Lb                xa,La

Y=B/(A+C)

yb,Vb
0   ya,Va            1
xA, yA
MULTIPLE CROSS CURRENT
LEACHING
• MODEL IS BASED ON AMOUNT IN
EACH PHASE

(xb,Lb)1 = (xa, La)2       xa,La
(xb,Lb)2

Y=B/(A+C)
M2

M1
yb,Vb
0            (ya,Va)1                 1
(ya,Va)2         xA, yA
MULTIPLE CROSS CURRENT
LEACHING EXAMPLE
https://portal.navf
ac.navy.mil/portal/
pls/portal/docs/1/3
196547.JPG
MULTISTAGE
COUNTERCURRENT LEACHING
• RESULTS FOR DESIGN
ARE SIMILAR TO
SHOWN IN FIG. 12.10-2
• FOR SYSTEM WITH
CONSTANT L/V RATIO,
THE APPROACH IS TO
MODEL USING
ABSORPTION FACTORS
FOR ALL STAGES
AFTER THE FIRST MIX
MULTISTAGE
COUNTERCURRENT
LEACHING CONFIGURATION

http://beta.cheresources.com/articles/basics-of-leaching.html
MULTISTAGE COUNTERCURRENT LEACHING
MODEL

http://beta.cheresources.
com/articles/basics-of-
leaching.html

```
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