|
|
|
|
|
|
|
Refined salt, which is most widely used presently, is mainly sodium chloride. Food
grade salt accounts for only a small part of salt production in industrialised countries
although worldwide, food uses account for 17.5% of salt production. The majority
is sold for industrial use. Salt has great commercial value because it is a necessary
ingredient in the manufacturing of many things. A few common examples include: the
production of pulp and paper, setting dyes in textiles and fabrics, and the making
of soaps and detergents.
|
|
Table salt is typical of the fine, granulated-evaporated salt produced in vacuum
evaporators. Virtually all food grade salt sold or used to produced by vacuum evaporation
of brine. Prior to mechanical evaporation, the brine may be treated to remove minerals
that can cause scaling in the evaporators and adversely affect salt purity. Chemical
treatment of the brine, followed by settling, reduces levels of dissolved calcium,
magnesium and sulfate. Sulfuric acid treatment or chlorination may be used to remove
hydrogen sulfide, and hydrochloric acid will neutralize brine used in diaphragm
cell production of chlorine and caustic soda. Brine purification has become increasingly
important to produce high purity salt for use in chlor-alkali production, particularly
where dry salt is used extensively for this purpose.
|
|
Ultimately, weak brine from either process is recycled to the solution mined cavern.
|
|
Crystallized salt is produced as slurry which is dewatered first by centrifuging
or vacuum drying and then in kiln or fluidized-bed dryers where moisture content
of the final product is reduced to 0.05% or less. During this century, salt producers
have made significant advances in lowering energy consumption and in reducing salting
and scaling in evaporators
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|