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 A briquette (or briquet) is a block of flammable matter used as fuel to start and maintain a fire.

Objectives of Agglomeration Improved flow properties  Pharmaceutics, ceramics Increased bulk density for storage  Detergents 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

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