1. KANKESHWARI DEVI INSTITUTE OF TECHNOLOGY,JAMNAGAR a Presentation on “Leaching” 5th sem sub:- MTO-I Prepared by Pansheriya Rahul Patel Akshay D Patel Akshay N.

2. OUTLINES Introduction to leaching. Leaching equipments.
Principles of Continuous Countercurrent Leaching.

3. INTRODUCTION TO LEACHING
Leaching / solid extraction – methods of removing one constituent from a solid by means of a liquid solvent.
Examples:
1. Making coffee from ground coffee beans
and tea from tea leaves.
(The complex mixture of chemicals that give coffee and tea their odor, taste, and physiological effects
are leached from the solid by hot water)
2. Extraction of oil from soybean flakes
3. Extraction of coconut milk from coconut
The amount of soluble material removed is often greater than in ordinary filtration washing.
The coarse, hard or granular feed solids may disintegrate in pulp or mush when their content of soluble material is removed.

4. Dispersed-solid Leaching
LEACHING EQUIPMENTS
Stationary Solid Beds
Moving-bed Leaching
Dispersed-solid Leaching
DESIRED OUTPUT

5. Dispersed-solid Leaching
LEACHING EQUIPMENTS
Stationary Solid Beds
Moving-bed Leaching
Dispersed-solid Leaching
DESIRED YIELD

6. Bollman Extractor
MOVING-BED LEACHING
Rotocel Extractor

7. BOLLMAN EXTRACTOR Contains a bucket elevator in a closed casing.
The buckets are loaded with flaky solids such as soybeans.
The solids are sprayed with appropriate amount of half miscella as they travel downward.
Half miscella is the intermediate solvent containing some extracted oil and some small solid particles.
As solids and solvent flow concurrently down the right-hand side of the machine, the solvent extracts more oil from the beans.

8. Fig. 23.1 (a) Bollman extractor

9. Bollman Extractor
MOVING-BED LEACHING
Rotocel Extractor

10. ROTOCEL EXTRACTOR
A horizontal basket is divided into walled compartments with a floor that is permeable to the liquid.
The basket rotates slowly about a vertical axis.
Solid are admitted to each compartment at feed point.
The compartments then pass a number of solvent sprays, a drainage section and a discharge point.
To give countercurrent extraction, the fresh solvent is fed only to the last compartment before the discharge point.

12. PRINCIPLE OF CONTINUOUS COUNTERCURRENT LEACHING
The most important method of leaching is the continuous countercurrent method suing stages.
The solid is not moved physically from stage to stage.
The liquids is being moved from stage to stage.

13. PRINCIPLES OF CONTINUOUS COUNTERCURRENT LEACHING
Ideal Stages In Countercurrent Leaching
Equilibrium
Operating Line
Constant And Variable Underflow
Number of ideal stages for constant underflow
Number of ideal stages for variable underflow

14. IDEAL STAGES IN COUNTERCURRENT LEACHING
V phase = the liquid phase (from stage N to stage 1)
L phase = the liquid carried with the solid (from stage 1 to stage N)
Exhausted solids leave Stage N
Concentrated solution overflow from Stage 1

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