chee2940 lecture 1 - overview

THE UNIVERSITY OF NEWCASTLE

DISCIPLINE OF CHEMICAL ENGINEERING

CHEE2940 – PARTICLE PROCESSING

Lecture Notes – 2006

Associate Professor Anh V. Nguyen Original course notes in this work are copyright to the University of Newcastle. Copyright in works, or parts of works, copied under the provisions of Part VB of the Copyright Act 1968 and reproduced herein, remain with the original author or copyright owner. © 2005 The University of Newcastle. Chee 2940: Lecture 1

Lecture 1: Overview of Particle Processing This Lecture Covers Overview: particle technology Modules of particle processing What are particles? Particle products Unit operations in particle processing

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1.1 PARTICLE TECHNOLOGY

WHAT IS PARTICLE TECHOLOGY?

• .Particle technology is defined as the art of the handling and processing of particles.

• Particles can be bulk solids, particulate solids and granular solids; liquid drops (emulsions) and gas bubbles.

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WHAT ARE THE MOST IMPORTANT PARAMETERS USED IN PARTICLE PROCESSING? • Physical parameters: size, shape and density of particle; density and viscosity of the continous phase, etc.

• Surface parameters: wettability, surface charge, Hamaker constants, adsorption, etc.

• Properties of additives (salts, surfactants) added to the continous phase.

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1.2 MODULES OF PARTICLE PROCESSING

ICLE PROCESSING

Module 2: Suspension Rheology & Surface Chemistry.

Mo Pa & Un The

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The last 6 weeks

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MODULE 1: PARTICLE CHARACTERISATION AND UNIT

OPERATION

• Particle size distribution and measurement • Size reduction and enlargement • Particle processing unit operations • Hopper design • Flow through packed beds • Fluidisation.

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MODULE 2: SURSPENSION RHEOLOGY AND SURFACE

CHEMISTRY

• Principle of rheology & rheological meas. • Surface chemistry • Some examples of particulate and emulsion and food processing

• Small wet particles • Foams • Emulsions • Pastes.

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1.3 WHAT ARE “PARTICLES”? • Primary particles: Individual objects of mass • Solid: Typical particles (powders) • Liquid: Drops (emulsions) • Gas: Foams.

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PARTICLES IN CONTINOUS PHASE

Particle: Dispersed phase Continous phase Solid particle Fluid Drop (liquid) Gas Emulsion (liquid) Liquid Bubble (air) Liquid Particulate particle (solid) Liquid Granular particle (solid) Gas

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Size Range of Particles

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Particle sizes considered in this course

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1.4 MANY PARTICLE PRODUCTS Mining and Mineral Processing: coal, gravel, sand, ceramics, iron ore, alumina, and clay.

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Food: flour, cereals, coffee (beans & instant), rice, spices, sugar, salt, etc.

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Pharmaceuticals: capsules, tablets, and emulsions.

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Household products: paints, laundry powder, paper, pool chlorine, dishwashing powder, etc.

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Agriculture: seeds, fertilizers

Others: bricks, concrete, dust, smoke, ash, bacteria, and blood cells. Chee 2940: Lecture 1 15

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Handle free- and non-free-flowing bulk products of particles including problematic materials and blends

Particles found in different industries

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1.5 PROCESS PROPERTIES OF INTEREST

Powder = group of particles. Granular material = group of granules. Behaviour of powder (or granular materials) effects processing and performance of products. Properties of particles affect the behaviour of powders: Chee 2940: Lecture 1 18

- Concentration of particles (volume fraction), - Size and shape of particles, - And interactions (forces) among particles.

Properties of Interest: Flow behaviour (rheology) Packing density (porosity) Strength of particle aggregates Mixability and segregation. Chee 2940: Lecture 1 19

Large or Small • Surface area to volume ratio • Large (>10 microns) – body forces dominates:

F = mg; F = ma (easy to understand). • Small (<10microns) – surface forces dominates: Colloidal particles (nanometre to 1 microns) & Macromolecules. Need specialist knowledge to understand

(surface chemistry)! Chee 2940: Lecture 1 20

Dry or Wet Fluid dynamic forces and surface forces!

Dry – aerodynamics negligible due to low viscosity of air in all but the smallest and least dense particles (dust, smoke). Wet – hydrodynamics is important, and solution and surface chemistry can be used to control surface forces in colloidal particles.

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Surface Chemistry Suspensions, emulsions and foams Forces between particles

- Attraction - Repulsion Effect of forces

- Sedimentation (creaming) - Dispersion

- Rheology.

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Rheology

Non-Newtonian fluids Measurements of rheological properties Effects of “particle” characteristics Effect of forces.

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1.6 UNIT OPERATIONS

Size Reduction: crushing and grinding

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Size Enlargement: agglomeration, granulation, pelletisation, pressing, tableting, spray drying.

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Conveying

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Handling, storage and packing

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