MECHANICAL SEPARATIONS

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Course Outline

Introduction to Separation Processes Role of Mechanical Separations in Chemical

Engineering Fundamentals of different mechanical separations;

Filtration, Sedimentation, Clarification, Flotation, Centrifugal separations, Jigging, tabling, magnetic and electrostatic separations, Sonic Agglomeration

Different types of mechanical separation equipment

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Introduction to Separation Processes

Separation process is used to transform a mixture of substances into two or more distinct products.

The mixture can be a combination of any two or more states: solid-solid, solid-liquid, solid-gas, liquid-liquid, liquid-gas, gas-gas, solid-liquid-gas mixture, etc.

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Phase creation

Phase addition

Barrier

Solid agent

External field

Separation Process Mechanisms

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How separation is carried out?

In order to affect a separation, separating agents are needed in the form of either:

Energy input (heat, electricity, magnetism,) Withdrawal of energy ( cooling, freezing) Medium (filter, membrane, screens) May be any phase as well as any chemical

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Classification of Separation processes

The classification can be based on the means of separation;1. Mechanical Processes2. Chemical processes

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Why Separations are needed?

Isolating valuable chemicals from mixtures Removing impurities from raw materials Purification of products

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Mechanical Separations

Mechanical Separations are applicable to heterogeneous mixtures, not to homogenous solutions. The techniques are based on the physical differences b/w the particles such as size, shape or density.

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Relatively less Energy Requirements

Ease of Operation

Ease of Maintenance

No special Feed pretreatment required

Not applicable for separating Components in homogeneous phase

Not versatile i.e. in same state may be one element can be separated

and other don’t.

Applicable to low flow rates

Advantages

Disadvantages

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Classification On the basis of characteristics

Depending on the difference in size or shape Depending on the difference in phase density Depending on fluid and particle mechanics Depending on surface, electrical or magnetic properties

On the basis of phases involved S-S L-L G-L L-G S-L L-S S-G

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Our focus will be the…

Solid – Solid Separation Solid – Liquid Separation Solid – Gas Separation

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Objective – to separate the mixture of solids into two or more fractions

Dry basis Screening Electrostatic

magnetic

Wet basis Classification

Solid – Solid Separation

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Objective – to separate the solids and liquid from each other

Filtration

Sedimentation – gravitational settling Centrifugal separators

Solid – Liquid Separation

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Objective – to separate the solids from gas

Filtration

Gravitational settling Centrifugation

Solid – Gas Separation

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Filtration

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Sedimentation

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Centrifugal Separation

                                                                  

                              

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Magnetic Separation

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Electrostatic Separation