Salt mining, solution

Solution Mining. Solution mining, also known as brining, is the recovery of sodium chloride or any soluble salt in an underground deposit by dissolving it in situ and forcing the resultant solution to the surface. 

A detailed description of salt mining will be postponed until the next chapter, but it is important to note that soda ash is made from both limestone and salt, the two major raw materials. As outlined in Fig. 5.2, the brine (salt solution) is mixed with ammonia in a large ammonia absorber. A lime kiln, using technology similar to that discussed earlier, serves as the source of carbon dioxide, which is mixed with the salt and ammonia in carbonation towers to form ammonium bicarbonate and finally sodium bicarbonate and ammonium chloride. Filtration separates the less soluble sodium bicarbonate from the ammonium chloride in solution. 

There are three important methods of salt isolation and purification brine solution, rock salt mining, and the open pan or grainer process. The percentages of these methods have not changed dramatically in the last few years and are 54% brine, 32% rock salt, and 14% grainer salt. 

Seawater is invaded into the groundwater and thus groundwater sometimes contains sodium chloride, which is called the seawater-type one. One of the possible sites for the repository is a salt mine. It is assumed that the site does not receive water invasion for so long, and this indicates the stability of the site. If groundwater invade the site, saline solution would be irradiated. Thus understanding of the radiolysis of water containing NaCl is also taken into consideration after the corrosion of the overpack of the HLW. Chloride ion is one species... 

The three main industrial methods used to produce salt are the solar evaporation method, mining of rock salt, and solution mining. The solar evaporation method is the oldest process used to obtain salt. This method is applied in geographic areas with high solar input and low... 

A third major process for extracting salt is solution mining this is especially useful for concentrated deep deposits. In solution mining injection wells are drilled into a salt deposit and water is pumped into it. The salt dissolves in the water to produce brine that is pumped back to the surface where it is processed to obtain salt. 

There are three methods of salt production and purification brine solution, rock salt mining, and the open pan or grainer process. 

The production cycle starts with the extraction of sodium chloride. About 20% of the world s salt consumption goes into soda ash production [24]. The next step after rock salt mining is the production and purification of brine yielding a concentrated aqueous sodium chloride solution [8,25-27]. A parallel step is the production of carbon dioxide gas by calcination of limestone. The brine is treated with ammonia and carbon dioxide under precipitation of the less-soluble sodium hydrogen-carbonate. Ammonia is recovered by mixing the mother liquor with calcium hydroxide and stripping off the ammonia with steam. Thermal decomposition of sodium hydrogencarbonate yields synthetic soda ash [8,20,22,23,28-38]. The output of soda ash produced by the ammonia-soda process amounts to about two-thirds of the world production [22,23]. 

Open www.saltiiisdtute.ai or a site dealing with the salt industry, (a) Name three states within the United States that have rock salt mines, (b) Of the sodium chloride mined (solid or solution), what percent of it is used to de-ice roads ... 

Figure 4.16 Extraction of rock salt by solution mining... 

On page 80 you saw that when a solution of sodium chloride is electrolysed, hydrogen and chlorine bubble off at the electrodes. Sodium ions and hydroxide ions are left in solution. This method is used in industry for making sodium hydroxide. The starting material is brine, a concentrated solution of sodium chloride in water, pumped up from salt mines. 

Locally, chlorides may also stem from the pollution emitted by plants using chloride solutions for the production of chlorine or sodium hydroxide, or from rock salt mining. 

Early demand for chlorine centered on textile bleaching, and chlorine generated through the electrolytic decomposition of salt (NaCl) sufficed. Sodium hydroxide was produced by the lime—soda reaction, using sodium carbonate readily available from the Solvay process. Increased demand for chlorine for PVC manufacture led to the production of chlorine and sodium hydroxide as coproducts. Solution mining of salt and the avadabiHty of asbestos resulted in the dominance of the diaphragm process in North America, whereas soHd salt and mercury avadabiHty led to the dominance of the mercury process in Europe. Japan imported its salt in soHd form and, until the development of the membrane process, also favored the mercury ceU for production. 

Brine Preparation. Sodium chloride solutions are occasionally available naturally but they are more often obtained by solution mining of salt deposits. Raw, near-saturated brines containing low concentrations of impurities such as magnesium and calcium salts, are purified to prevent scaling of processing equipment and contamination of the product. Some brines also contain significant amounts of sulfates (see Chemicals FROMBRINe). Brine is usually purified by a lime—soda treatment where the magnesium is precipitated with milk of lime (Ca(OH)2) and the calcium precipitated with soda ash. After separation from the precipitated impurities, the brine is sent to the ammonia absorbers. 

Resources for Potash Fertilizers. Potassium is the seventh most abundant element in the earth s cmst. The raw materials from which postash fertilizer is derived are principally bedded marine evaporite deposits, but other sources include surface and subsurface brines. Both underground and solution mining are used to recover evaporite deposits, and fractional crystallization (qv) is used for the brines. The potassium salts of marine evaporite deposits occur in beds in intervals of haUte [14762-51-7] NaCl, which also contains bedded anhydrite [7778-18-9], CaSO, and clay or shale. The K O content of such deposits varies widely (see Potassium compounds). 

MIBK is a highly effective separating agent for metals from solutions of their salts and is used in the mining industries to extract plutonium from uranium, niobium from tantalum, and zirconium from hafnium (112,113). MIBK is also used in the production of specialty surfactants for inks (qv), paints, and pesticide formulations, examples of which are 2,4,7,9-tetramethyl-5-decyn-4,7-diol and its ethoxylated adduct. Other appHcations include as a solvent for adhesives and wax/oil separation (114), in leather (qv) finishing, textile coating, and as a denaturant for ethanol formulations. 

This shift in emphasis by the mining iadustry has led to the development and use of a variety of improved techniques, in particular the commercial avadabihty of several metal specific extractants. These techniques are particularly useful in the separations and recycling of metals from metal sludges and metal salt solutions. 

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