Mechanical Operations

Mechanical Operations (CH 31007)

Unit operations

There are many physical operations that are common to a number

of the individual industries, and may be regarded as unit

operations

Some of these operations involve particulate solids

many of them are aimed at achieving a separation of the

components of a mixture

03-09-2015 CH 31007 2

Mechanical operations

Chemical Engineering unit operations :

Fluid flow processes: fluids transportation, filtration, and solids

fluidization

Heat transfer processes: evaporation, condensation, and heat

exchange

Mass transfer processes: gas absorption, distillation, extraction,

adsorption, and drying

Thermodynamic processes: gas liquefaction, and refrigeration

Mechanical processes: solids transportation, crushing and

pulverization, and screening and sieving

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Why mechanical operations!

Foundation of designs of chemical plants, factories, and equipment used

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Particulate Solids

Solids are difficult than Fluids !

complex geometrical arrangements

basic problem of defining completely the physical state of the

material

The most important characteristics of an individual

particle

its composition, properties as density and conductivity [provided

the particle is completely uniform]

size and shape

03-09-2015 CH 31007 5

Particulate Solids

Particle size affects properties such as the surface per unit volume

and the rate at which a particle will settle in a fluid

Particle shape ?

Industrial scale: Large quantities of particles are handled and it is

frequently necessary to define the system as a whole

Not the particle size

But the particle size distribution

Mean size

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Particulate Solids

To reduce the size of particles

To enlarge the size of particles or form them into

aggregates or sinters

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What will I cover?

Crushing and grinding

Mean particle size

Size distribution

Crushers and mills

Screening

Sieve or membrane: Screen of filter

Settling: different rate of sedimentation of particles or drops as they move through gas or

liquid

Special cases: Electrostatic, magnetic etc.

Slurry Transport

Mixing and Segregation

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Few things to remember!

Mid-Sem 30 Sep 14 - 22, 2015End-Sem 50 Nov 18, 2015 onwardTA 20 ??

03-09-2015 CH 31007 9

Coulson & Richardsons Chemical Engineering Vol. 2: Particle

Technology and Separation Processes: Richardson, J. F., Harker, J. H., and

Backhurst, J. R.) [Butterworth-Heinemann]

Unit Operations of Chemical Engineering: McCABE, W. L., SMITH, J. C. and

HARRIOTT, P. [McGraw-Hill]

Particle Size ReductionMechanical Operations (CH 31007)

Background

3-Sep-15 CH 31007 2

Materials are rarely found in the size range required

Often necessary either to decrease or to increase the size

While decreasing in size

particle size will have to be progressively reduced in stages

Most appropriate type of machine at each stage depends

size of the feed and of the product

properties as compressive strength, brittleness and stickiness

Background

Sometimes very fine powders are too difficult to handle

Hazardous dust clouds during transportation

Size enlargement processes include

granulation for the preparation of fertilisers

compaction using compressive forces to form the tablets

in pharmaceuticals

3-Sep-15 CH 31007 3

Single particles

The sphere of the same volume as the particle.

The sphere of the same surface area as the particle.

The sphere of the same surface area per unit volume as the particle.

The sphere of the same area as the particle when projected on to a plane

perpendicular to its direction of motion.

The sphere of the same projected area as the particle, as viewed from above, when

lying in its position of maximum stability such as on a microscope slide for example.

The sphere which will just pass through the same size of square aperture as the

particle, such as on a screen for example.

The sphere with the same settling velocity as the particle in a specified fluid.

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Sphericity

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Size Reduction of Solids (Comminution)

To increase the surface area

most reactions involving solid particles, the rate of reactions is

directly proportional to the area of contact with a second

phase

drying of porous solids, where reduction in size causes both an

increase in area and a reduction in the distance the

moisture must travel within the particles in order to reach the

surface

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Size Reduction of Solids (Comminution)

Necessary to break a material into very small particles in

order to separate two constituents, especially where

one is dispersed in small isolated pockets

Colour and covering power of a pigment is considerably

affected by the size of the particles

More intimate mixing of solids can be achieved if the

particle size is small

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Mechanism of Size Reduction

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A single lump of material is subjected to a sudden impact/blow

few relatively large particles

a number of fine particles

relatively few particles of intermediate size

Energy in the blow is increased

the larger particles will be of a rather smaller size & more

numerous

the number of fine particles will be appreciably increased, but

their size will not be much altered

Mechanism of Size Reduction

Size of the fine particles: closely connected with the

internal structure of the material

Size of the larger particles: more closely connected

with the process by which the size reduction is effected

Grind limit: After some time there seems to be little

change in particle size but may result in a change

in shape rather than in size

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Effect of progressive grinding on size distribution

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persistent mode

transitory mode

Method of Application of the Force

Impact: particle concussion by a single rigid force

Compression: particle disintegration by two rigid forces

Cutting or Shear: produced by a fluid or by particle

particle interaction

Attrition or Rubbing: arising from particles scraping

against one another or against a rigid surface

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Method of Application of the Force

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Impact: Coarse, medium, or fine particles

Compression: Coarse and relatively few fine particles

Cutting / Shear: definite particle size & shape, no fines

Attrition / Rubbing: very fine particles

Crushing + Attrition

Stress applied between two surfaces (either surfaceparticle or particleparticle) at low velocity, 0.0110 m/s

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Jaw Crusher

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Gyratory Crusher

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Crushing Rolls

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Impact + Attrition

Stress applied at a single solid surface (surfaceparticle or particleparticle) at high velocity, 10200 m/s

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Hammer Mill

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Fluid Energy Mill

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Shear + Attrition

Stress applied by carrier mediumusually in wet grinding to bring about disagglomeration

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Sand Mill

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Colloid Mill

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Ball Mill

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Ball mill

May be used wet or dry although wet grinding facilitates

the removal of the product.

The costs of installation and power are low.

May be used with an inert atmosphere and therefore can

be used for the grinding of explosive materials.

The grinding medium is cheap.

Suitable for materials of all degrees of hardness.

May be used for batch or continuous operation.

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Hammer Mill

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Hardinge conical ball

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Question!

If a ball mill, 1.2 m in diameter, is operating at 0.80 Hz, suggest the

modification in operating condition to achieve its improved

efficiency.

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Ideal Crusher or Grinder !!

Large capacity

Product of single size or size distribution

Requirement of small power input per unit of product

Size reduction is a very inefficient process and only between 0.1 and

2.0 per cent of the energy supplied to the machine appears as

increased surface energy in the solids

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Energy Requirements

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for p = -2

Rittingers law

fc is the crushing strength of the materialThe energy required for size reduction the increase in surface

Energy Requirements

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for p = -1

Kicks law

The energy required for size reduction the reduction ratio

Energy Requirements

Neither of these two laws permits an accurate calculation of the energy

requirements

Rittingers law is applicable mainly to that part of the process where

new surface is being created and holds most accurately for fine

grinding where the increase in surface per unit mass of material is large

Kicks law, more closely relates to the energy required to effect elastic

deformation before fracture occurs

Kicks law is more accurate than Rittingers law for coarse crushing

where the amount of surface produced is considerably less

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Energy Requirements

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for p = -3/2

Work index: the amount of energy required to reduce unit mass of material from an infinite particle size to a size L2 of 100 m

Bonds law

Problem

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Classification of size reduction equipment

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Nature of the material to be crushed

Hardness The hardness of the material affects the power consumption and the wear on the machine.

With hard and abrasive materials it is necessary to use a low-speed machine and to protect

the bearings from the abrasive dusts that are produced.

Structure Normal granular materials such as coal, ores and rocks can be effectively crushed employing

the normal forces of compression, impact, and so on. With fibrous materials a tearing action

is required

Moisture content It is found that materials do not flow well if they contain between about 5 and 50 per cent

of moisture. In general, grinding can be carried out satisfactorily outside these limits.

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Crushing strength The power required for crushing is almost directly proportional to the

crushing strength of the material.

Friability The friability of the material is its tendency to fracture during normal

handling. In general, a crystalline material will break along well-defined planes and the power required for crushing will increase as the particle size is reduced.

Stickiness A sticky material will tend to clog the grinding equipment and it should

therefore be ground in a plant that can be cleaned easily.

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Soapiness

In general, this is a measure of the coefficient of friction of the

surface of the material. If the coefficient of friction is low, the

crushing may be more difficult.

Explosive materials

must be ground wet or in the presence of an inert atmosphere.

Hazardous materials

Materials yielding dusts that are harmful to the health must be

ground under conditions where the dust is not allowed to escape.

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Types of Crushing Equipment

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Crushers (coarse & fine)

Grinders (intermediate & fine) Ultrafine grinders Cutting machines

Jaw crushers Hammer millsHammer mills with internal classification

Knife cutters

Gyratory crusher Bowl mills, Roller mills Fluid-energy mills Dicers

Crushing rolls Attrition mills Agitated mills Slitters

Tumbling mills(Ball mill, Rod mill, pebble mill, Tube mill)

Methods of operating crushers

Free crushing

feeding the material at a comparatively low rate so that the

product can readily escape

short residence time prevents the production of appreciable

quantities of undersize material

Choke feeding

the machine is kept full of material

discharge of the product is blocked so that the material remains

in the crusher for a longer period

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Methods of operating crushers

Open circuit grinding choke feeding

Closed circuit grinding free crushing

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Recap

3-Sep-15 CH 31007 44

Particle Size Distribution

Single particle size !!

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It is important to use the method of size measurement

which directly gives the particle size which is relevant to

the situation or process of interest.

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3-Sep-15

Why!

Quantitative indication of the mean size and of the spread of sizes

Results of a size analysis can most conveniently be represented by

means of a cumulative mass fraction curve

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Size frequency curve

Size frequency curve

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Cumulative distribution

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Differential frequency distribution

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Different distributions

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Conversion between distributions

Many modern instruments actually measure a number

distribution, which is rarely needed in practice

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If N is the total number of particles in the population,

the number of particles in the size range

the surface area of these particles

aS is the factor relating the linear dimension of the particle

to its surface area

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S is the total surface area of the population of particles

For a given population of particles, the total number of

particles, N, and the total surface area, S are constant.


assuming particle shape is independent of size,

i.e. aS is constant

3-Sep-15


Similarly, for the distribution by volume

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3-Sep-15

Describing the mixture by a single number

The mode

Most frequently occurring size in the sample

For the same sample, different modes would be obtained for

distributions by number, surface and volume

The median

Easily read from the cumulative distribution as the 50% size

The size which splits the distribution into two equal parts

Different means including arithmetic, geometric, quadratic,

harmonic, etc.

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Different means

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Mean sizes based on volume

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Considering unit mass of particles consisting of n1 particles of

characteristic dimension d1, constituting a mass fraction x1

mean volume diameter

volume mean diameter

Different means

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Problem

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Solution

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Problem

3-Sep-15

Solution

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0

3-Sep-15

Quiz!

The size analysis of a powdered material on a mass basis is represented by

a straight line from 0% mass at 1 micron particle size to 100% mass at 101

micron particle size. What is the surface mean diameter of the particles

constituting the system?

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3-Sep-15 CH 31007 75

Recap

Frequency distribution curves

Cumulative curves

Cumulative distribution is the integral of the frequency

distribution

Distributions can be by number, surface, mass or volume

3-Sep-15

Methods of particle size measurement

Sieving (>50 m)

dry sieving using woven wire sieves is a simple, cheap method

gives a mass distribution and a size known as the sieve diameter

sieve series are arranged so that the ratio of aperture sizes on

consecutive sieves is 2, 21/2 or 21/4 according to the closeness of

sizing

horizontal & vertical vibration

lower limit of size!!

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Screen efficiency

F = feed, D = overflow, B = underflow

xF , xD , xB mass fraction of material A

(1-xF), (1-xD), (1-xB), mass fraction of material C

F = B + D

F xF = D xD + B xB

=

=

Screen efficiency

= ; based on oversize = (1)(1); based on undersize = = (1)(1); overall effectiveness = ()()(1)()2 1

Capacity and effectiveness of screens

The capacity of a screen is measured by the mass of

material that can be fed per unit time to a unit area of

the screen.

Capacity and effectiveness are opposing factors.

To obtain maximum effectiveness, the capacity must be

small, and large capacity is obtainable only at the

expense of a reduction in effectiveness.

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For coarse crushing, Kicks law may be used

mean diameter of feed = 45 mm, mean diameter of product = 4 mm,

energy consumption = 13.0 kJ/kg, compressive strength = 22.5 N/m2

mean diameter of feed = 42.5 mm, mean diameter of product = 0.50 mm

compressive strength = 45 MN/m2


Microscopic analysis (1100 m)

measurement of the projected area of the particle and also

enables an assessment to be made of its 2-D shape

3-Sep-15 CH 31007 86


Sedimentation and elutriation methods (>1 m)

the rate of sedimentation of a sample of particles in a liquid

The suspension is dilute and so the particles are assumed to fall

at their single particle terminal velocity in the liquid (usually

water)

Stokes law is assumed to apply

the method using water is suitable only for particles typically less

than 50 mm in diameter

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terminal falling velocity of a particle in a fluid increases with size

Assumptions

The suspension is sufficiently dilute for the particles to

settle as individuals (i.e. not hindered settling)

Motion of the particles in the liquid obeys Stokes law

(true for particles typically smaller than 50 mm)

Particles are assumed to accelerate rapidly to their

terminal free fall velocity UT so that the time for

acceleration is negligible

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Sedimentation

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Particles are assumed to accelerate rapidly to their terminal free fall velocity

UT so that the time for acceleration is negligible

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Ergun Equation

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Permeametry

This is a method of size analysis based on fluid flow

through a packed bed

The pressure gradient across a packed bed of known

voidage is measured as a function of flow rate

The diameter we calculate from the CarmanKozeny

equation is the arithmetic mean of the surface

distribution

3-Sep-15 CH 31007 93

Electrozone Sensing

Particles are held in suspension in a dilute electrolyte which is drawn

through a tiny orifice with a voltage applied across it

As particles flow through the orifice a voltage pulse is recorded

The amplitude of the pulse can be related to the volume of the particle

passing the orifice

Thus, by electronically counting and classifying the pulses according to

amplitude this technique can give a number distribution of the

equivalent volume sphere diameter

The lower size limit is dictated by the smallest practical orifice and the

upper limit is governed by the need to maintain particles in suspension

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Although liquids more viscous than water may be used to reduce

sedimentation, the practical range of size for this method is 0.31000 mm

SAMPLING

In practice, the size distribution of many tonnes of powder are often

assumed from an analysis performed on just a few grams or

milligrams of sample

The importance of that sample being representative of the bulk

powder cannot be overstated

The powder should be in motion when sampled

The whole of the moving stream should be taken for many short

time increments

3-Sep-15 CH 31007 96


Microscopic analysis (1100 m)

measurement of the projected area of the particle and also

enables an assessment to be made of its 2-D shape

3-Sep-15 CH 31007 2


Sedimentation and elutriation methods (>1 m)

the rate of sedimentation of a sample of particles in a liquid

The suspension is dilute and so the particles are assumed to fall

at their single particle terminal velocity in the liquid (usually

water)

Stokes law is assumed to apply

the method using water is suitable only for particles typically less

than 50 mm in diameter

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3-Sep-15 CH 31007 4

terminal falling velocity of a particle in a fluid increases with size

Assumptions

The suspension is sufficiently dilute for the particles to

settle as individuals (i.e. not hindered settling)

Motion of the particles in the liquid obeys Stokes law

(true for particles typically smaller than 50 mm)

Particles are assumed to accelerate rapidly to their

terminal free fall velocity UT so that the time for

acceleration is negligible

3-Sep-15 CH 31007 5

Sedimentation

3-Sep-15 CH 31007 6

Particles are assumed to accelerate rapidly to their terminal free fall velocity

UT so that the time for acceleration is negligible

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Ergun Equation

3-Sep-15 CH 31007 8

Permeametry

This is a method of size analysis based on fluid flow

through a packed bed

The pressure gradient across a packed bed of known

voidage is measured as a function of flow rate

The diameter we calculate from the CarmanKozeny

equation is the arithmetic mean of the surface

distribution

3-Sep-15 CH 31007 9

Electrozone Sensing

3-Sep-15 CH 31007 10

Although liquids more viscous than water may be used to reduce

sedimentation, the practical range of size for this method is 0.31000 mm

Electrozone Sensing

Particles are held in suspension in a dilute electrolyte which is drawn

through a tiny orifice with a voltage applied across it

As particles flow through the orifice a voltage pulse is recorded

The amplitude of the pulse can be related to the volume of the particle

passing the orifice

Thus, by electronically counting and classifying the pulses according to

amplitude this technique can give a number distribution of the

equivalent volume sphere diameter

The lower size limit is dictated by the smallest practical orifice and the

upper limit is governed by the need to maintain particles in suspension

3-Sep-15 CH 31007 11

SAMPLING

In practice, the size distribution of many tonnes of powder are often

assumed from an analysis performed on just a few grams or

milligrams of sample

The importance of that sample being representative of the bulk

powder cannot be overstated

The powder should be in motion when sampled

The whole of the moving stream should be taken for many short

time increments

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Particle in a Fluid

To develop an understanding of the forces resisting the

motion of a single particle

To provide methods for the estimation of the steady

velocity of the particle relative to the fluid

3-Sep-15

Motion of Solid Particles in a Fluid

The drag force resisting very slow steady relative motion

(creeping motion) between a rigid sphere and a fluid of

infinite extent

where U is the relative velocity, x is the sphere dia.

Stokes law

3-Sep-15

Stokes law

Stokes law is found to hold for single particle Reynolds

number,

almost exactly for Rep 0.1

within 9% for Rep 0.3

3-Sep-15

Drag Coefficient

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Particles falling under gravity through a fluid

3-Sep-15

A particle falling from rest in a fluid will initially experience a high

acceleration as the shear stress drag, which increases with relative

velocity, will be small.

As the particle accelerates the drag force increases, causing the

acceleration to reduce.

Eventually a force balance is achieved when the acceleration is zero and

a maximum or terminal relative velocity is reached. This is known as the

single particle terminal velocity.

Particle terminal velocity

3-Sep-15

where UT is the single particle terminal velocity


3-Sep-15

in the Stokes law region

terminal velocity is proportional to the square of the particle diameter


In the Newtons law region

terminal velocity is independent of the fluid viscosity and

proportional to the square root of the particle diameter

3-Sep-15


In the intermediate region no explicit expression

Generally, when calculating the terminal velocity for a

given particle or the particle diameter for a given

velocity, it is not known which region of operation is

relevant.

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For a given particle size

3-Sep-15

Archimedes number

produce a straight line of slope 2 if plotted on the

logarithmic coordinates (log CD versus log Rep) of the

standard drag curve. The intersection of this straight line with

the drag curve gives the value of Rep.

For a given UT

3-Sep-15

Non-Spherical Particles

3-Sep-15

Shape affects drag coefficient far more in the intermediate

and Newtons law regions than in the Stokes law region.

In the Stokes law region particles fall with their longest surface

nearly parallel to the direction of motion, whereas, in the

Newtons law region particles present their maximum area to the

oncoming fluid.

3-Sep-15

Sand particles falling from rest in air

(particle density, 2600 kg/m3)

3-Sep-15 CH 31007 27

Effect of boundaries on terminal velocity

When a particle is falling through a fluid in the presence

of a solid boundary the terminal velocity reached by the

particle is less than that for an infinite fluid.

In practice, this is really only relevant to the falling

sphere method of measuring liquid viscosity, which is

restricted to the Stokes region.

3-Sep-15

Effect of boundaries on terminal velocity

In the case of a particle falling along the axis of a

vertical pipe this is described by a wall factor,

the ratio of the velocity in the pipe, UD to the velocity in an

infinite fluid, Ua.

3-Sep-15

A sphere of diameter 10 mm and density 7700 kg/m3 falls under gravity at terminal

conditions through a liquid of density 900 kg/m3 in a tube of diameter 12 mm. The

measured terminal velocity of the particle is 1.6 mm/s. Calculate the viscosity of the

fluid. Verify that Stokes law applies.

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Separation

Separation can be divided into 2 classes:

Diffusional operations: transfer of material between phases

Mechanical separation: based on physical differences, e.g. size,

shape, density

Mechanical separation are applied to heterogeneous

mixtures, NOT to homogeneous mixtures

3-Sep-15

Mechanical Separation

Separation of solids from gases

liquid drops from gases

solids from solids

solids from liquids

Mechanical separation can be achieved by: Sieve or membrane: Screen of filter

Settling: different rate of sedimentation of particles or drops as they move through gas or liquid

Special cases: Electrostatic, magnetic etc.

3-Sep-15

Screening

Separating particles due to size ONLY

Single screen gives unsized fractions

Series of screens provides sized fractions

Commonly applied for large scale for the separation

Generally applicable for particles of a size as small as

about 50 m

3-Sep-15

Screening

For very fine materials

difficulty of producing accurately woven fine gauze of sufficient

strength

screens become clogged

other methods of separation are usually more economical

Woven wire cloth is generally used for fine sizes and

perforated plates for the larger meshes

3-Sep-15

Screening

Commonly done in dry mode, occasionally in wet mode

With coarse solids the screen surface may be

continuously washed by means of a flowing stream of

water

to keep the particles apart

to remove the finer particles from the surface of larger particles

to keep the screen free of adhering materials

3-Sep-15

Screening

Fine screens are normally operated wet, with the solids

fed continuously as a suspension

Concentrated suspensions have high effective viscosities

and frequently exhibit shear-thinning non-Newtonian

characteristics

By maintaining a high cross-flow velocity over the surface of the

screen, or by rapid vibration, the apparent viscosity of the

suspension may be reduced and the screening rate substantially

increased.

3-Sep-15

Multiphase systems

3-Sep-15

Dissolved or dispersed phase

Continuous medium

Solution Colloid Coarse dispersion

Gas GasGas mixture: air (oxygen and other gases in nitrogen)

None None

Liquid Gas NoneAerosols of liquid particles: fog, mist, vapor, hair sprays

Aerosol

Solid Gas NoneAerosols of solid particles: smoke, cloud, air particulates

Solid aerosol: dust

Gas Liquid Solution: oxygen in water Liquid foam: whipped cream, shaving cream Foam

Liquid Liquid Solution: alcoholic beverages Emulsion Emulsion: milk, mayonnaise, hand cream

Solid Liquid Solution: sugar in water Liquid sol: pigmented ink, bloodSuspension: mud (soil, clay or silt particles are suspended in water)

Gas Solid Solution: hydrogen in metals Solid foam: aerogel Foam: dry sponge

Liquid Solid Solution: amalgam Gel: agar, gelatin, silica gel, opal Wet sponge

Solid Solid Solution: alloys Solid sol: cranberry glass Gravel, granite

Source: Wikipedia

Non-Newtonian fluid

3-Sep-15

Non-Newtonian fluid

3-Sep-15

Time-dependent viscosity

RheopecticApparent viscosity increases with duration of stress

Printer ink

ThixotropicApparent viscosity decreases with duration of stress

Yogurt, aqueous iron oxide gels, gelatin gels, some clays, some drilling muds, many paints, colloidal suspensions

Time-independent viscosity

Shear thickening(dilatant)

Apparent viscosity increases with increased stress

Suspensions of corn starch in water, sand in water

Shear thinning(pseudoplastic)

Apparent viscosity decreases with increased stress

Nail polish, whipped cream, ketchup, molasses, syrups, paper pulp in water, latex paint, blood, some silicone oils, some silicone coatings

Generalized Newtonian fluids

Viscosity is constantStress depends on normal and shear strain rates and also the pressure applied on it

Custard, Water

Screening Equipment

In most cases, the particles drop through the openings

by gravity

Coarse particles drop through easily, but with fine

particles, screen must be agitated

Agitation can be done by

shaking

vibrating

mechanically or electrically

3-Sep-15

Stationary screen & Grizzly

Made of longitudinal bars up to 3 m long, fixed in a

rectangular framework

Space between bars is 2 8 in.

Usually inclined at an angle to the horizontal

Greater the angle, the greater is the throughput BUT the

screening efficiency is reduced

Effective for very coarse free-flowing solids containing

few fine particles

3-Sep-15

Grizzlies

3-Sep-15 Source: Google Image

Electromagnetic screen

3-Sep-15The screen itself is vibrated

Mechanical screen

3-Sep-15The whole assembly is vibrated

Mechanical screen

As very rapid accelerations and retardations are produced, the

power consumption and the wear on the bearings are high

Generally mounted in a multi-deck fashion with the coarsest

screen on top, either horizontally or inclined at angles up to

45

With the horizontal machine, the vibratory motion fulfils the

additional function of moving the particles across the screen

3-Sep-15

Mechanical screen

The screen area which is required for a given operation

cannot be predicted without testing the material under

similar conditions on a small plant

In particular, the tendency of the material to clog the

screening surface can only be determined experimentally

3-Sep-15

Trommel

3-Sep-15

A very large mechanically operated screen

Electrostatic separator

3-Sep-15

3-Sep-15

Cyclone separator

1. IntroductionMechanical Operations (CH 31007)Unit operationsMechanical operationsWhy mechanical operations!Particulate SolidsParticulate SolidsParticulate SolidsWhat will I cover?Few things to remember!

2. Particle Size Reduction and EnlargementParticle Size ReductionMechanical Operations (CH 31007)BackgroundBackgroundSingle particlesSphericitySlide Number 6Slide Number 7Size Reduction of Solids (Comminution)Size Reduction of Solids (Comminution)Mechanism of Size ReductionMechanism of Size ReductionEffect of progressive grinding on size distributionMethod of Application of the ForceMethod of Application of the ForceCrushing + AttritionJaw CrusherGyratory CrusherCrushing RollsImpact + AttritionHammer MillFluid Energy MillShear + AttritionSand MillColloid MillBall MillBall millHammer MillHardinge conical ballQuestion!Ideal Crusher or Grinder !!Energy RequirementsEnergy RequirementsEnergy RequirementsEnergy RequirementsProblemSlide Number 36Classification of size reduction equipmentNature of the material to be crushedNature of the material to be crushedNature of the material to be crushedTypes of Crushing EquipmentMethods of operating crushersMethods of operating crushersRecapParticle Size DistributionSingle particle size !!Slide Number 47Slide Number 48Why!Size frequency curveCumulative distributionDifferential frequency distributionDifferent distributionsConversion between distributionsConversion between distributionsConversion between distributionsConversion between distributionsConversion between distributionsConversion between distributionsDescribing the mixture by a single numberDifferent meansSlide Number 62Slide Number 63Mean sizes based on volumeDifferent meansProblemSolutionSlide Number 68Slide Number 69ProblemSolutionSlide Number 72Slide Number 73Quiz!Slide Number 75RecapMethods of particle size measurementSlide Number 78Screen efficiencyScreen efficiencyCapacity and effectiveness of screensSlide Number 82Slide Number 83Slide Number 84Slide Number 85Methods of particle size measurementMethods of particle size measurementSlide Number 88AssumptionsSedimentationSlide Number 91Ergun EquationPermeametryElectrozone SensingSlide Number 95SAMPLING

3. Particle in fluidSlide Number 1Methods of particle size measurementMethods of particle size measurementSlide Number 4AssumptionsSedimentationSlide Number 7Ergun EquationPermeametryElectrozone SensingElectrozone SensingSAMPLINGParticle in a FluidMotion of Solid Particles in a FluidStokes lawDrag CoefficientSlide Number 17Particles falling under gravity through a fluidParticle terminal velocityParticle terminal velocityParticle terminal velocityParticle terminal velocityFor a given particle sizeFor a given UTNon-Spherical ParticlesSlide Number 26Sand particles falling from rest in air (particle density, 2600 kg/m3)Effect of boundaries on terminal velocityEffect of boundaries on terminal velocitySlide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34Slide Number 35SeparationMechanical SeparationScreeningScreeningScreeningScreeningMultiphase systemsNon-Newtonian fluidNon-Newtonian fluidScreening EquipmentStationary screen & GrizzlyGrizzliesElectromagnetic screenMechanical screenMechanical screenMechanical screenTrommelElectrostatic separatorSlide Number 54

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Mechanical Operations