Three words come up again and again when talking about salt production lines: washing, drying and refining. They are sometimes taken to be similar stages, but each has a different purpose, and not every line needs all three.
Washing: removing what is on the crystal surface
Washing removes dirt, suspended impurities and part of the soluble impurities on the surface of raw salt crystals. It is usually done with saturated brine rather than fresh water, so the salt itself does not dissolve. Equipment related to this stage includes washing augers, tanks and hydrocyclones.
After washing, the salt is wet with brine, which is separated in a hydrocyclone and then a centrifuge. More on the salt washing lines page.
Drying: reducing moisture
Even after centrifuging, salt keeps some moisture. Drying reduces it so the salt flows freely and does not cake in storage and packaging. This takes place in a dryer — a rotary or surface dryer, for example — where the salt meets hot air supplied by a heater and moved by a blower.
Drying does not change the purity of the salt; it only changes its water content. See salt drying lines.
Refining: raising purity
Refining aims for higher purity than washing alone can achieve, and is needed when the final specification calls for it. Methods vary with the type of impurities and the purity required, and may include multi-stage washing, brine treatment, separation and drying. See salt refining lines.
Does your line need all three?
Not necessarily. Some industrial uses only need grinding and screening; some lines need washing and drying only; a high-purity product needs refining. What decides this is the final product and its specification, and the condition of the raw salt.
This article is general guidance. Every project needs its own information reviewed before any technical recommendation.
