Powder Processing

An entire industry is dedicated to the science, materials and equipment associated with the handling of powders.

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An entire industry is dedicated to the science, materials and equipment associated with the handling of powders. In no industry is this more true than ceramics, almost every material used is supplied in powdered form. Close to 100% of powders used are insoluble and most are inert. Potters deal with ceramic powders hands-on, mixing glazes and bodies by hand. Each one flows and dusts differently when handled. They come in every color and they can have vastly different densities - some feel as light as feathers and others as heavy as lead. Certain powders are much more difficult to clean up than others. Some mix easily with water, others will only do so if first mixed with other powders. Some do not suspend in water at all, others will stay suspended for months. Some contain soluble salts that discolor the water in which they are mixed (after they settle). Some are plastic and sticky when mixed with water, others not at all. Some powders settle and pack in storage, others stay loose. With others, particles agglomerate on storage, making high-energy propeller mixing and sieving necessary (to remove the lumps).

In raw material production powders need to be hammer, roller or ball milled; chemically and magnetically treated; sieved and classified; purified; pelletized; calcined or roasted; moved or elevated by air, pipe or conveyor belt; held in hoppers; tumbled in mixers; slurried; pugged; etc. Factories producing ware likewise must deal with many of the same processes in addition to all the knowhow needed to turn powdered ingredients into fired ceramics. Producers have learned to make powders of smaller and smaller particle sizes (e.g. nano particles). The science of powders is constantly advancing, it is an interesting and exciting field for engineers.

Dust presents occupational hazards depending on the particle shape, size, surface topography and mineralogy. Ceramic materials are typically rated as irritants, dangerous (typical because they contain quartz) or toxic. Most countries enforce workplace regulations to control labelling and precautions in handling and usage.

Related Information

Links

Glossary	Ultimate Particles Utlimate particles of ceramic materials are finer than can be measured even on a 325 mesh screen. These particles are the key players in the physical presence of the material.
Glossary	Particle Size Distribution Knowing the distribution of particle sizes in a ceramic material is often very important in assessing its function and suitability for an application.
Glossary	Particle Sizes
Glossary	Dust Pressing Many ceramic products, especially tile, are formed by pressing high-moisture or binder-containing dust or pelletized dust into steel molds at high pressures.
Hazards	Dealing With Dust in Ceramics A checklist for changes and additions to your tools and equipment and suggestions for habit you need to develop to control dust in your workplace.
Typecodes	Materials/Powder Handling Conveyors, elevator, hoppers, metering, bagging.
Typecodes	Grinding Equipment Hammer mills, roller mills, ball mills.
Typecodes	Powder Classification Equipment Air classifiers, vibrating screens.
Typecodes	Materials Drying Equipment Spray drying, tunnel drying.

By Tony Hansen
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