(Fluid-Particles Systems) Separation II (Fluid-Particles Systems) Course Code: CHPE402 Lecturer: Dr. Abdul Ameer Bandar Office Number: 5D-44E-mail: abdulameer@uniwa.edu.om

Course Description

Learning Outcome

Assessment Methods

Assignment format The student required to submit the hard copy of the assignment. The hard copy should not exceed 10 pages A4 size, including front page, appendices, etc.). The text should be made in 12pt font using Times New Roman style with 1.5 line spacing. Finally, references should be written in standard scientific way (check the literature). 5

Reviewing Procedure A peer review practice will be applied to all presentations. The student should submit their presentation 2 days in advance to the reviewing group. The reviewing group should meet and submit not more than 1 page of comments and recommendations. The student should take action on these comments by revising their presentation based on these comments. 6

1. Particle Size Analysis & Measurements. Particle Characterization 1. Particle Size Analysis & Measurements. 2. Particle Agglomeration (Chapter 1)

Goals To be able to define different terminology of particle sizes. To describe general principles and methods of particle size analysis.

What do you need to consider before you select the method for particle size measurement?

Dr Mustafa Nasser @2010

Particulate Solids Properties of particulate solids Define the physical state of the solid materials Single particle: Its composition; size and shape Bulk particle: distribution of particle; mean size

Particulate Solids Properties of particulate solids Composition Determines properties such as density and conductivity for the uniformed particles (non porous particles) Size and shape Important in that this affects properties such as the surface per unit volume and the rate at which a particle will settle in a fluid Regular shape: spherical or cubic  precise definition Irregular shape: a piece of broken glass  in terms of some particular characteristics of a regular shaped particle (degree of sphericity)

Selecting a Method and Sampling (1) Selecting the method for determining particle size (or size distribution) Select a definition of particle size that is appropriate for the application. (ii) Select a method of measurement that is appropriate to the definition.

Describing Size of A Single Particle The size of irregular shape particle can be defined in terms of the size of an equivalent sphere such as: The sphere of the same volume as the particle (Equivalent Volume Sphere Diameter) The sphere of the same surface areas per unit volume as the particle ( Surface-Volume/ Equivalent Sphere Diameter). Circle with area equal to projected area of particle Equivalent circle diameter

Describing Size of A Single Particle Feret’s diameter (The mean distance apart of two parallel lines which are tangential to the particle in an arbitrarily fixed direction) Sphericity, : Measure particle shape Parallel tangents Feret’s diameter Asv: Surface area of sphere of same volume as particle Ap : Surface area of particle

IS CHEMICAL PROPERTY IMPORTANT? Dr Mustafa Nasser @2010

Methods of Particle Size Measurement Sieving Microscopy Sedimentation Permeability Laser Diffraction Electrozone Sensing – For eg. Coulter Counter

Methods of Particle Size Measurement 1) Sieving (> 45 m) Can be a nest of sieves, each lower size being smaller aperture size

Ratios of aperture sizes on consecutive sieves: 2, 21/2, 21/4 Mounted on a vibrator or hand shaken Orientation, not only the size, would affect the passed particles Standard Sieves sizes US Tyler UK British Standard IMM US ASTM

Dr Mustafa Nasser @2010

…Continued 1) Sieving Commonly used and cheap Though based on a linear dimension, generally assuming spherical particles Mean particle diameter retained by a screen is the sum of the aperture of the screen on which the material is retained, plus the aperture of the next largest screen, divided by 2.

…Continued 1) Sieving The results of a sieve analysis may be presented as a plot of: cumulative percent undersize (falling through) vs aperture size cumulative percent oversize (retained on screen) vs aperture size weight or percent retained on each screen used in sequence versus aperture size (or average diameter)

Efficiency of screening Efficiency of screening: the ratio of the mass of material which passes the screen to that which is capable of passing If w is the mass of particles of a particular size on the screen at a time t, then: where k is a constant for a given size and shape of particle and for a given screen

Methods of Particle Size Measurement 2) Microscopic analysis (1 - 100 m) Permits measurement of the projected area of the particle Enable the assessment to be made of its two-dimensional shape Automatic scanning uses the electron microscope, where the lower limit of size can be reduced to about 0.001 m Coupled with image analysis system, microscope can provide number distributions of size and shape. Image of ash particles taken using SEM

Scanning Electron Microscopy An insect coated in gold for viewing with a scanning electron microscope. http://en.wikipedia.org/wiki/Electron_microscope

Different Types of Electron Microscopy TEM (Transmission Electron Microscopy) SEM http://en.wikipedia.org/wiki/Scanning_Electron_Microscope

Methods of Particle Size Measurement 3) Sedimentation methods (> 1m) Terminal falling velocity of a particle in a fluid increases with size Pipette method Samples are abstracted from the settling suspension at a fixed horizontal level at intervals time Andreason pipette (2-100 m) Suspension sampling level Sampling tube

Methods of Particle Size Measurement 3) Elutriation method is a reverse sedimentation process in which the particles are dispersed in an upward flowing stream of fluid.

Methods of Particle Size Measurement 4) Permeability methods (> 1m) Depends on the fact that at low flowrates the flow through a packed bed is directly proportional to the pressure difference The proportional constant being proportional to the square of the specific surface (surface: volume ratio) of the powder Possible to obtain the diameter of the sphere with the same specific surface as the powder

Methods of Particle Size Measurement 5) Laser Diffraction

Methods of Particle Size Measurement Laser Diffraction Laser diffraction is the most widely used technique for particle size analysis. In laser diffraction, a representative cloud or ensemble of particle passes through a broadened beam of laser light which scatters the incident light onto a Fourier lens. This lens focuses the scattered light onto detector array and, using an inversion algorithm, a particle size distribution is obtained. Practical range of size  0.1-2000 m

Methods of Particle Size Measurement 6) Coulter Counter (Electrozone Sensing Method) Advanced method for particle size measurement A Coulter Counter www.paint.ugent.be

Coulter Counter (Electrozone Sensing method) Particles are held in suspension in a dilute electrolyte which is drawn through the orifice with a voltage applied across it. Voltage pulse is recorded as particles flow through the orifice. Amplitude of pulse can be related to volume of particle. Sketch of a coulter counter found online on the homepages of Pulver Technology Ltd (c). folk.uio.no/anderne/research.html

Methods of Particle Size Measurement Coulter Counter (Electrozone Sensing method) Not only measure the particle sizes, but also provide the size distribution of the particles Particle size distribution: By number By length By surface By mass (or volume) Reported as: Frequency or cumulative distributions?

Particle Agglomeration Objectives To understand the mechanism of agglomeration To study key rate processes of agglomeration To illustrate the different types of agglomeration equipments

What is Agglomeration?

Agglomeration Agglomeration happens when small particles stick together, forming aggregates which are of larger sizes.

Scaled up agglomerates (Source: NIZO food research)

What are the Objectives of Agglomeration?

Objectives of Agglomeration Production of useful structural forms  For eg. in pressing of intricate shapes in powder metallurgy Provision of a defined quantity for dispensing and metering  Agricultural chemical granules or pharmaceuticals tablets Elimination of dust handling hazards or losses  Briquetting of waste fines Improved product appearance  Food Reduced caking and lump formation  Fertilizer

Objectives of Agglomeration Improved flow properties  Pharmaceutics, ceramics Increased bulk density for storage  Detergents Creation of non-segregating blends of powder ingredients Control of solubility Control of porosity and surface-to-volume ratio Improvement of heat transfer Removal of particles from liquid

1) Agglomeration by Agitation Methods Will be referred to as granulation, where a particulate feed is introduced to a process vessel and is agglomerated to form a granulated product Liquid binder used to form interparticle bonds Agitation of “wet mass” to promote liquid binder dispersion and granule growth

1) Agglomeration by Agitation Methods Feeds: a mixture of solid ingredients (formulation), which includes an active or key ingredient, binders, diluents, flow acids, surfactants, wetting agents, lubricants, fillers or end-use aids (e.g. sintering aids, colors or dyes, taste modifiers) Induction: solvents addition; heat (lead to controlled sintering) Include fluid-bed, pan, drum, and mixer granulators Spray drying is an extreme case with no further, intended agglomeration taking place after granule formation

2) Agglomeration by Compression Methods X=(x1, x2,..., xn) Y=(y1, y2,..., yn) Compression vessel Feed P=(p1, p2,..., pj) % x y Product (x or y) = (size, voidage, strength, surface properties, quality metric) Where the mixture of particulate matter is fed to a compression device which promotes agglomeration due to pressure. Usually dry, sometimes liquid as lubricant.

2) Agglomeration by Compression Methods Products: briquette or tablet Induction: heat or cooling; carrier fluids (wet extruded) Processes: Continuous: roll presses; briquetting machines; extrusion Batch: tabletting Semi-continuous: Ram extrusion

2) Agglomeration by Compression Methods This is a forming process controlled by mechanical properties of the feed in relationship to applied stresses and strains Mechanical processes controlled by microlevel processes such as friction, hardness, size, shape and elastic modulus Particles deform and break during compaction Compaction processes give the highest density agglomerates and can operate without liquid binder

Agglomeration Circuit Dr Mustafa Nasser @2010

Size-Enlargement methods and Application (Adapted from Table 20-36 in Perry’s Handbook) Product Size (mm) Granule Density Scale of operation Typical application Tumbling granulators 0.5 to 20 Moderate 0.5-800 ton/hr Fertilizers, iron ore, non-ferrous ore, agricultural chemicals Mixer granulators Continuous high shear Batch high shear 0.1 to 2 Low to high High Up to 50 ton/hr Up to 500 kg batch Chemicals, detergents, clays, carbon black Centrifugal granulators 0.3 to 3 Moderate to high Up to 200 kg batch Pharmaceuticals, agricultural chemicals Pressure compaction Extrusion Roll press Tablet press >0.5 >1 10 High to very high Up to 5 ton/hr Up to 1 ton/hr Pharmaceuticals, catalysts, clays, minerals, ceramics, organic and inorganic chemicals

Example

EXERCISE 1.2: Repeat Exercise 1.1 for a regular cylinder of diameter 0.100 mm and length 1.00 mm. calculate the following diameters: (a) the equivalent volume sphere diameter (b) the equivalent surface sphere diameter (c) the surface-volume diameter (the diameter of a sphere having the same external surface to volume ratio as the particle). (d) the sieve diameter (the width of the minimum aperture through which the particle will pass) (e) the projected area diameters (the diameter of a circle having the same area as the projected area of the particle resting in a stable position).