Production of sea salt

In the production of sea salt in China, the salt drying method is generally adopted, which is also called "beach salt drying method", that is, the coastal beach is used to build a dam to open up a salt field, and seawater is pumped by tidal waves to attract seawater to fill the pool, which is evaporated by sunlight into brine. When the concentration of brine evaporates to 25 degrees Pompeii, sodium chloride precipitates out, which is the original salt. The production of crude salt by solarization has the advantages of energy saving and low cost. However, due to the influence of geography and climate, it is impossible to build salt pans on all coastal beaches, and it is impossible to dry salt in all seasons. Air drying, long sunshine time, large evaporation and high salt production, on the contrary, low production. In salt fields in northern China, only March to165438+1October is the salt drying season.

The process of producing crude salt by solarization is generally divided into four processes: absorbing moisture, making brine, crystallizing and collecting salt.

1. Nachao

In fact, it is the extraction process of raw materials for producing raw salt. Seawater is the raw material for making salt. In order to ensure the normal production, we must do everything possible to ensure the supply of raw materials. At present, there are two kinds of tidal absorption methods, one is natural tidal absorption and the other is dynamic tidal absorption. Natural tide absorption is to let seawater flow naturally along the tidal channel at high tide; Axial flow pump is generally used to introduce seawater into tidal power generation, which is characterized by being free from natural conditions.

Make salt water

Salt water production is carried out in a huge evaporation pool. According to the daily evaporation, the water depth of the evaporation pool is properly controlled, so that the salt water concentration gradually increases and finally condenses into saturated salt water.

crystal

In the process of continuous evaporation and concentration of seawater, the concentration of various salts is increasing. When the salt concentration reaches saturation, it will precipitate in the form of crystals. In supersaturated solution, the crystal can continue to grow by keeping the supersaturated state of the solution.

Collect salt

It is to put away the salt that grows and pile it up manually or mechanically.

(2) Mine salt production

The production of well salt is mainly divided into two links: brine extraction and salt making. Different types of ores adopt different brine extraction methods. The methods of extracting natural brine include salvage method, gas lift method, pumping oil to extract brine, deep well submerged brine pump, self-spraying brine and so on. In rock salt-type mining areas, most of them adopt drilling solution mining method, some adopt single-well convection method, and some adopt double-well hydraulic fracturing method.

1. Convection method

This method is one of the commonly used methods for mining rock salt deposits at home and abroad at present, with high mechanization and low cost. It uses the water-soluble property of rock salt ore for mining. The concrete methods are: drilling a well to the salt layer, running two layers of casing, sealing the outer casing with oil-filled cement, injecting water from one layer of pipeline to dissolve the salt layer, and pumping salt water from the other layer of pipeline.

2. Fracturing method

This method is to drill two wells on the ground, run casing, seal the well pipe with the borehole wall, squeeze out high-pressure water from one well, form a channel in the salt layer, dissolve the salt layer, form saturated brine, and squeeze out the ground from the other well for production. Salt is made in a factory. The brine purified from the brine storage tank is input into the storage tank and heated by steam to make the water evaporate continuously. After the brine is evaporated, it becomes semi-salt and semi-water salt slurry, which is dehydrated by centrifuge and dried in boiling bed to obtain the finished salt. If the brine contains more mirabilite, mirabilite can be extracted by freezing mother liquor or thermal method; Jiangxi Salt Mine has introduced the salt and nitrate co-production process of Sulzer Company of Switzerland, which is a leading representative. If the brine contains more gypsum, gypsum should be put forward to ensure the quality of salt.

(3) production of lake salt

Lake salt is primary salt and regenerated salt, and mining method or beach drying method is mainly used. In terms of mining, some lakes have been evaporated for a long time, and sodium chloride is deposited at the bottom of the lake, so it can be directly fished without treatment. For example, the salt lake in the Qaidam basin has experienced tens of millions of years of changes; A dry lake formed, and its salt was exposed on the surface. At present, salt pickers or salt pickers are used in various places for production, and the process flow is roughly as follows: peeling plastic film-salt pickers-pipeline transportation (or automobile transportation)-washing and dehydration-conveying a finished salt lump with a belt conveyor. As for the beach drying method, it is similar to the sea salt production process.