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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.
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Particle Agglomeration Objectives • To understand the mechanism of agglomeration • To study key rate processes of agglomeration • To illustrate the different types of agglomeration equipments
Agglomeration Agglomeration happens when small particles stick together, forming aggregates which are of larger sizes.
Scaled up agglomerates (Source: NIZO food research)
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
P=(p1, p2,..., pj) Y=(y1, y2,..., yn) X=(x1, x2,..., xn) Product Feed Compression vessel % % (x or y) = (size, voidage, strength, surface properties, quality metric) x y 2) Agglomeration by Compression Methods • 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)