Slurry Processing

Glaze, engobe and body slurries are suspensions and they are an integral part of ceramic production. In almost all cases slurries can exist because the electrolytic properties of clay particles present create a gel that suspends the other particles.

Ceramic slurries may be such as part of the processing of a material: For example, powders don't screen well below about 60 mesh, so a clay might be put into slurry form to enable sieving out of impurities and oversize particles (after which the water is removed). Slurries are also much better for magnetic separation to remove iron impurities. And clay suspensions are better for grinding in ball mills. Slurries also enable the removal of dissolved soluble salts present in some materials.

As noted, slurries often need to be dewatered. In the case of clay bodies that are mixed and wet-processed, this is normally done by filter pressing or centrifuging. For the production of a powder and pellets, spray and rotary dry are also common. All of these are energy-intensive.

Often slurries are such to enable their use in ceramic production (e.g. glazes, engobes, casting slips). Industries (suppliers and users) need to be able to efficiently and consistently mix slurries and transport, pump, spray, roll, pour, store and monitor and adjust their rheological properties. The science, materials and equipment associated with the handling of suspensions and slurries create an entire industry in itself (another is dedicated to the handling of powders).

The oil industry processes drilling mud in tremendous volumes, often doing so well below 200 mesh. How. They throw horsepower and PSI at problems! Decanting centrifuges are an example, hundreds of gallons a minute, and crystal clear water comes out one spout, fine slurry out another, and oversize particles out a third. They also employ multi-level screen shakers that can handle large volumes of slurry.

Related Information

Links

URLs	https://www.nov.com/products/hs-3400-series-centrifuge Brandt dewatering decanter centrifuge for clay slurries
URLs	https://www.slb.com/drilling/drilling-fluids-and-well-cementing/solids-control/centrifuges/cd-500-hv-centrifuge MI Swaco slurry solids separating centrifuge
URLs	https://www.smac.it/en/dettaglio.php?idprod=58 MAP-2M glaze tank with pump and agitator
URLs	https://www.smac.it/en/dettaglio.php?idprod=210 D-Glaze automatic glaze density controller
URLs	https://www.smac.it/en/dettaglio.php?idprod=226 V-Check glaze slurry viscosity monitoring device
URLs	https://www.smac.it/en/dettaglio.php?idprod=239 K-Flow automatic glaze flow rate controller for spray nozzles
Glossary	Suspension In ceramics, glazes are slurries. They consist of water and undissolved powders kept in suspension by clay particles. You have much more control over the properties than you might think.
Glossary	Rheology In ceramics, this term refers to the flow and gel properties of a glaze or body suspension (made from water and mineral powders, with possible additives, deflocculants, modifiers).
Glossary	Sieve Sieves are important in ceramics for removing particulates and agglomerates from glaze, engobe and body slurries.

By Tony Hansen
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