There are some 14,000 commercial applications for salt ranging from use in pulp-and-paper production to explosives. Ands then of course there is road salt, which makes Canada the world's highest salt consumers with 360kg.
The world's largest salt mine is in Goderich, Ontario extending several kilometers under Lake Huron., In Canada, salt was at one time sold in blocks, then ground at home, much like roasted coffee beans that are roasted just before grinding for brewing. This way the aromatics of coffee can be appreciated much better.
On an industrial scale salt is produced in one of two principal ways: the evaporation of salt water (brine) or by mining. Evaporation can either be solar evaloration or using some heating device.
Solar evaporation of seawater
In the correct climate (one for which the ratio of evaporation to rainfall is suitably high) it is possible to use solar evaporation of sea water to produce salt. Brine is evaporated in a linked set of ponds until the solution is sufficiently concentrated by the final pond that the salt crystalises on the pond's floor.
Open pan production from brine
One of the traditional methods of salt production in more temperate climates is using open pans. In an open pan salt works brine is heated in large, shallow open pans. Earliest examples date back to prehistoric times and the pans were made of ceramics known as briquetage, or lead. Later examples were made from iron. This change coincided with a change from wood to coal for the purpose of heating the brine. Brine would be pumped into the pans, and concentrated by the heat of the fire burning underneath. As crystals of salt formed these would be raked out and more brine added.
Closed pan production under vacuum
The open pan salt works has effectively been replaced with a closed pan system where the brine solution is evaporated under a partial vacuum.
In the second half of the 19th century industrial mining and drilling techniques originally from China made the discovery of more and deeper deposits possible, mine salt. Although more expensive than solar evaporation of seawater and extracting solar salt from brine, the result of this was that the price of salt became more reasonable due to less monopolisation. Extraction of salt from brine is still heavily used: for example vacuum salt produced by British Salt in Middlewich has 57% of the UK market for salt used in cooking.
The above facts came from the following websites:
From Wikipedia, the free encyclopedia