PARTICLE SIZE ANALYSIS

Nupoor Agrawal , Shwetanshu Suman

2nd year, Metallurgical and Materials Science Engineering

National Institute Of Technology ,Jamshedpur

Under the supervision of

Professor Ranjit Prasad

Table of contents

Introduction

Methods

How we choose a particular method?

Explanation of methods

Graphical representation of sizing analyses

Applications

References

INTRODUCTION

Particle size analysis is the collective name of the technical procedures, or laboratory techniques which determines the size range or mean size of the particles in a powder or liquid sample.

In order to keep manufacturing costs low and to ensure the product itself is of a high quality, the particle size distribution of required material needs to be measured and controlled.

Particle-size analysis helps in increasing the effectiveness of materials being processed in an operation . As oversize materials will cause damage to equipment and slow down production.

 unwanted materials will contaminate products if they are not detected.

Various methods have been discovered till now to do particle size analysis.

METHODS FOR DETERMINING THE PARTICLES SIZE Test sieving

Sedimentation

Laser diffraction

Electro resistance counting

Elutriation

Electron Microscopy

Classification of Powder d50 Sieve Opening (µm)

Very Coarse > 1000

Coarse 355–1000

Moderately Fine 180–355

Fine 125–180

Very Fine 90–125

How we choose a particular method?

Criteria for selection Nature of the material to be analyzed like estimated particle size and

their range, solubility ,toxicity ,flow ability ,intended use , ease of handling etc.

Economic factors

Specified requirements

Time factors

Methods Approximate useful range(microns)

Test sieving 100,000-10

Elutriation 40-5

Microscopy (optical) 50-0.25

Sedimentation (gravity) 40-1

Sedimentation (centrifugal) 5-0.05

Electron microscopy 1-0.005

Sieve analysis It is accomplished by passing a known weight of sample successively

through finer sieves and weighing the amount collected on each sieve to determine the percentage weight in each size fraction.

The effectiveness of a sieving test depends on the amount of material put on the sieve and the type of movement imparted to the sieve.

Equations used:- % Retained = Wsieve X 100 %

Wtotal

% Passing = W below X 100%

W total

Results of a typical sieve testSieve size range (µm)

Sieve wt fractions(g)

Sieve % wt fractions

Nominal aperture size (µm)

Cumulative % undersize

Cumulative % oversize

+250 0.02 0.1 250 99.9 0.1

-250 + 180 1.32 2.9 180 97.0 3.0

-180 + 125 4.23 9.5 125 87.5 12.5

-125 + 90 9.44 21.2 90 66.3 33.7

-90 + 63 13.10 29.4 63 36.9 63.1

-63 +45 11.56 26.0 45 10.9 89.1

-45 4.87 10.9

Sedimentation method A single solid sphere settling in a fluid has a terminal velocity

which is related to its diameter.

Terminal velocity of a particle in a fluid increases with size.

Stokes's Law :

It is based on the measurement of the rate of settling of the powder particles uniformly dispersed in a fluid .the principle used is beaker’s decantation.

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Laser diffraction method Laser diffraction analysis, also known as laser diffraction

spectroscopy, is a technology that utilizes diffraction patterns of a laser beam passed through any object ranging from nanometres to millimetres in size to quickly measure geometrical dimensions of a particle.

This process does not depend on volumetric flow rate, the amount of particles that passes through a surface over time.

The angle of diffraction increases as particle size decreases and so the method is best for measuring ultrafine particles.

Electroresistance counting It measures the momentary changes in the conductivity of a

liquid passing through an orifice that take place when individual non conducting particles pass through.

The particle count is obtained by counting pulses ,and the size is dependent on the size of each pulse. Example :-coulter counter

A Coulter counter  is an apparatus for counting and sizing particles suspended in electrolytes. It is used for cells, bacteria, prokaryotic cells and virus particles.

Elutriation Elutriation is a process for separating particles based on their size,

shape and density, using a stream of gas or liquid flowing in a direction usually opposite to the direction of sedimentation. 

All elutriators consist of one or more “sorting columns” in which the fluid is rising at a constant velocity.

 The smaller or lighter particles rise to the top (overflow) because their terminal sedimentation velocities are lower than the velocity of the rising fluid.

The terminal velocities of any particle in any medium can be calculated using Stokes' Law if the particle Reynolds number is below 0.2.

Graphical representations of sizing analyses

Applications The coulter counter technique has been used to diagnose a variety of

diseases, and is the standard method for obtaining red blood cell counts (RBCs) and white blood cell counts (WBCs).

The laser diffraction technique is used to observe distribution of sediments such as clay , mud, with an emphasis on silt and the sizes of bigger samples of clay.

 particle size distribution can change mechanical, transport and densification properties of ceramics accordingly as per the requirement.

polystyrene a type of plastic requires particle size analysis.

 the Coulter Principle has been adapted to the nanoscale to produce a novel nanoparticle characterization technique called Tunable Resistive Pulse Sensing, or TRPS.

Having properly sized particles allow aggregate companies to create long-lasting roads and other products.

References

Principle of mineral dressing by A.M Gaudin

Mineral processing technology by Barry .A.Wills

http://ranjit.rds.net.in/2013/03/11/assignment-for-2k11-batch-g-m-b-mme/

http://www.smartdogmining.com/tools/Notebook/Notebook.html

http://en.wikipedia.org/wiki/Coulter_counter

http://en.wikipedia.org/wiki/Sieve_analysis

http://en.wikipedia.org/wiki/Particle_size_analysis

http://en.wikipedia.org/wiki/Laser_diffraction_analysis

Thank you