The first method is solar evaporation. This method is the oldest method of the three. When people saw salt crystals in the sea, they began using it. In solar evaporation, it has to be done in warm places because it occurs when the evaporation rate exceeds the precipitation rate. In most occurances, the salt is received from a pool of water, where the sun has evaporated most of the water and has left the salt. There are two different kinds of ponds that are used during the process. There is a concentrating pond, where the salt water from the ocean is being concentrated. There is also a crystalizin pond where the salt is being produced.
The next method is the rock salt mining method. This method is an underground mining method. Giant machinces go into caves and receive the salt. The temperature of the underground mines usually stay at about 70 degrees year round. Most domes of salt are located from Alabama to Texas. Usually 45 to 65 percent of the salt is taken away, but they must leave some still standing so the cave will not collapse on the workers. The first step is undercutting. Next they drill small holes into the walls. Then they add explosives to the holes. When they explode, several hundreds or thousands of tons of salt are all along the floor of the cave. They then continue to clean it and send it all over the world.
The last method is the vacuum evaporation method. This method is the evaporation of salt brine by steam heat in evaporators. The evaporators are called vacuum pans. The first process is called solution mining. This is when they drill holes into the salt deposits. The process starts by having water being pumped down one side and dissolves the salt. The brine is pushed out to the surface and taken to storage. After that, the brine is put under giant vacuums. The principal that they work around is that 'Whenever the pressure is lowered, the temperature at which water will boil is also lowered'. Steam is fed to the first pan causing the brine to boil. The steam from the first pan will cause the second pan to boil. The pressure of the pans increase, so the steam from the previous one will make the next boil.
ALL INFORMATION AND PICTURES FOUND AT:
"Morton Salt." Morton Salt. N.p., n.d. Web. 16 Feb. 2014. <http://www.mortonsalt.com/salt-facts/salt-production-and-processing>.
