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Salt consists of colorless crystals and has a distinctive taste. Salt is a general name for sodium chloride (NaCl). It is most familiar for being a food supplement, a flavor enhancer. However, only 5% of the production is used to this end. For 70% salt is used in the chemical industry, as chlorine source. Salt is also used to clear the roads of snow and ice, to soften water, to conserve food and to stabilize the earth for building.
Salt can be obtained from brine or from rock deposits (halite). Salt rocks are the result of the evaporation of oceans in prehistoric times. This salt can be excavated or it can be injected with water en sucked up. When water is sprayed, brine is obtained. Brine comes from oceans, salt water lakes (like the Dead sea) or underground pools. Apart from the NaCl the sources of salt contain many other salts, slate and quartz.
Production process of salt from rocks
When a salt rock or mine is discovered the salt is excavated. A similar way of excavating coal is used.
First and second grinding
Under the ground the crystals are ground one time, the pieces of salt are still very large (about 23 cm length). Afterwards the salt crystals are transported to the surface. Above the ground they are ground for a second time so that a length of about 8 cm is obtained.
The salt crystals, that are still very large, are brought under a magnet. The magnet removes all iron particles from the salt. Afterwards, stones are removed. To achieve this goal the salt crystals are thrown in a rotating drum of stainless steel. By the force with which the salt crystals are thrown in the drum they break and go through holes in the sides of the drum. Stones are harder than salt and do not break. Therefore they cannot go through the holes.
In the third grinding process the salt crystals are reduced to a size of 2.5 cm. If smaller salt crystals are desired the salt should be reground. If more pure salt is desired the crystals can be dissolved and further processed as in the brine process.
Production process of salt from brine
The brine can be further processed (purification and drying) in several ways. The brine can be purified and dried in an open pan
by means of the sun, a multi-stage vacuum evaporator or mechanic evaporator.
Producing salt with the help of the sun can only happen in hot, dry and sunny areas. The brine is exposed to the sun in an open pan
. The water and the soluble matters evaporate. Because insoluble or hardly soluble matters deposit as soon as the evaporation starts, the brine is pumped to a second pan. The evaporation continues and the salt begins to crystallize. The brine is now pumped to a third evaporation pan. After a time of evaporation a brine comes to being with a very high concentration of salt, but the concentration of magnesium chloride and magnesium sulphate is also high.
Afterwards, the strongly concentrated brine is washed with a very concentrated salt solution and subsequently with pure water. After 2 to 3 months draining a salt comes to being with a purity of 99.4%. The purity can be increased by repeating the washing process. In this way, salt with a purity of 99.8% can be obtained, which can be used in the food industry.
The crystals are dried in a hot air oven at 185°C and subsequently they are sorted by size.
Multi-stage vacuum evaporator
The brine is chemically purified in order to remove the calcium and magnesium components. Afterwards, the kettles of the evaporators are filled with brine. The first kettle is heated with steam, the brine is boiled and hot water vapor rises. This vapor heats the second kettle and so on. Because the installation is kept under vacuum the boiling point of the brine is lower than with atmospheric pressure. This makes sure that less energy (in the form of steam) has to be added to bring the brine to and keep it at the right temperature.
The brine looses a lot of water during the evaporation process and a fat salt slurry remains. The slurry is removed, dried in an oven and sorted by size.
The production of salt is also possible by means of mechanical evaporation. First, the calcium and magnesium components are removed by a chemical process. Afterwards, the brine is pumped in large open pans and it is heated by tubes through which steam is flowing. It is heated to a temperature just below the boiling point, usually to 90°C. During the evaporation process flakes of salt are formed on the surface. With lower temperatures larger flakes and with higher temperatures smaller flakes are formed. The flakes grow until they deposit in the pan. These flakes are caught and dried. When the brine is first partly evaporated by means of a vacuum evaporator a combination of flakes and crystals comes into being.
Continuation of both processes
Iodine (in the form of potassium iodide) is added to salt that is used in the food industry and by consumers. The iodine prevents thyroid diseases. Nowadays iodine salt is used in bread and is added to edible salt.
Subsequently magnesium carbonate, calcium silicate, calcium phosphate, magnesium silicate or calcium carbonate are added to prevent lumping and therefore to increase the dispersion.
Nitrite is added to salt for the meat industry.
The salt is now ready to be packed. Usually the salt is packed in paper bags. It is important that the salt is stored at a dry place because moisture can permeate the packing.
Salt consists of colorless crystals and has a distinctive taste. Salt is a general name for sodium chloride (NaCl). It is most familiar for being a food supplement, a flavor enhancer. However, only 5% of the production is used to this end. For 70%... read full description