Solar salt production

Feed brines for solar salt recovery may be derived from seawater with salinity of about 3.5%, or from one of the enclosed seas or natural salt lakes of higher salinities (Table 6.3). The Caspian Sea is not used for solar salt production because of its much lower salinity (1.3%) and its temperate location. Also, its salts content is about 25% lower in chloride and about three times higher in sulfate than ordinary sea salt. 

The bittern (spent brine) from solar salt production contains 300 00 g/L dissolved solids relatively enriched in the less concentrated salt impurities. This may be either discarded or further worked to recover other elements of value. Brine from the Great Salt Lake, for instance, is processed for magnesium chloride hexahydrate recovery [10], which occurs at a density of 1.26g/cm. This is later converted to metallic magnesium [12]. The Dead Sea brines are processed primarily for potassium chloride (potash), but are also worked for sodium and magnesium chlorides and derived products such as bromine and hydrochloric acid [16] (Sections 6.2.2 and 8.8). 

H.W.J. Lee, Optimal Control of the Solar Salt Production Process. CSIRO, Canberra, ACT, 1993. 

Some potassium chemicals are currently separated from sea water by fractional crystallization of the bittern from solar salt production. Several years ago the Dutch operated a process which utilized dipicrylamine to precipitate potassium from sea water, but this reagent is rather costly. We are developing a... 

Salt mining is a large-scale specialized activity. Few chlorine producers mine salt or have much control over the process. Section 7.1.2 therefore gives only a brief review of the subject of mechanical mining of rock salt. Solar salt production, on the other hand, is closely tied to chlorine plants in some parts of the world. A fuller description of its production seems appropriate and appears in Section 7.1.3. 

We should also consider a variation on solar salt production in which the ponds are preconcentrators, with final salt production in conventional evaporators. Figure 7.5 shows the steam required to produce a ton of dry NaQ in a triple-effect evaporator as a function of the incoming seawater concentration. 

High concentrations of uranium may also occur in inland waters where evaporative processes prevail a study of the uranium content in brines during solar salt production has shown that the evaporating water body becomes enriched in uranium while CaS04 and NaCl precipitate. ... 

Davis, J. S. Importance of microorganisms in solar salt production. nProceedings of the 4" Symposium on Salt, Vol. I, Coogan, A. L. (Ed.), Northern Ohio Geological Society Cleveland, 1974, pp. 369-372. 

Fig. 1. Principal salt deposits and dry salt production sites in North America, where H represents the salt deposits and D, x, and Q correspond to evaporated, rock, and solar production sites, respectively. Sites in Canada, Hsted by company name (location), are Alberta, , Canadian (Lindberg) Saskatchewan, , Sifto/Namsco (Unity) and Canadian (BeUe Plaine) Ontario, and x, Sifto/Namsco (Goderich) , Canadian (Windsor) x, Canadian (Ojibway) New Bmnswick, x. Potash Corp. of Saskatchewan (Sussex) and Nova Scotia, and x, Canadian (Pugwash) and Mines Seleine (Quebec), and,...

Similar to processing mined rock salt, solar salt may be cmshed, screened, and kiln dried or fluidized-bed dried. Coarse solar salt is a premium product because of high purity and relatively large crystal size. It is in particular demand for use to regenerate the resin in cation-exchange water softeners... 

Electrodialysis. Electro dialytic membrane process technology is used extensively in Japan to produce granulated—evaporated salt. Filtered seawater is concentrated by membrane electro dialysis and evaporated in multiple-effect evaporators. Seawater can be concentrated to a product brine concentration of 200 g/L at a power consumption of 150 kWh/1 of NaCl (8). Improvements in membrane technology have reduced the power consumption and energy costs so that a high value-added product such as table salt can be produced economically by electro dialysis. However, industrial-grade salt produced in this manner caimot compete economically with the large quantities of low cost solar salt imported into Japan from Austraha and Mexico. 

Sodium nitrate is also used in formulations of heat-transfer salts for he at-treatment baths for alloys and metals, mbber vulcanization, and petrochemical industries. A mixture of sodium nitrate and potassium nitrate is used to capture solar energy (qv) to transform it into electrical energy. The potential of sodium nitrate in the field of solar salts depends on the commercial development of this process. Other uses of sodium nitrate include water (qv) treatment, ice melting, adhesives (qv), cleaning compounds, pyrotechnics, curing bacons and meats (see Food additives), organics nitration, certain types of pharmaceutical production, refining of some alloys, recovery of lead, and production of uranium. 

Solar salt operations can be found along the shores of the Great Salt Lake and in the San Francisco Bay area (6—10). Salt production from these areas represents 10% of the total salt produced in the United States. 

Total solar salt, NaCl, produced in the world is 90 million tons. Well over that amount of salt is produced in preconcentration ponds as an intermediate step in the production of other chemicals such as potassium chloride. For example, the Dead Sea faciUties produce 40 million tons of salt each year but sell none because of the high cost of transportation to markets. 

Solar-grade silicon, production of, 22 507-508 Solar heat control, use of gold in, 12 703 Solarization effect, 19 203 Solar photocatalysis, 23 23-24 Solar photocatalytic detoxification, 19 76 Solar photocatalytic processes, 19 100-101 Solar photocatalytic reactor, using deposited titania, 19 99 Solar photoreactors, 19 95-99 Solar salt harvesting, 22 802, 806-808 Solar spectrum, 23 2 Solar still, 26 89-92 Solar thermal converters, 23 10-13 Solar transmittance, for thin films, 23 19 Solatene, 24 558 Solder, 3 53... 

E.-F. GeofEroy stated that sal ammoniac, because of its volatility and die manner in which it used to be prepared, was often called the heavenly eagle, the flying lUtle bird, die solar salt, or die mercurial soot (43). Herman Boerhaave believed diat, since Vesuvius and other volcanoes eject sal ammoniac, it is therefore necessary to class this salt with die fossils, although it is believed that that which is now being brought to us is an animal production (75). By die word fossil Boerhaave and his contemporaries meant a mineral, or substance dug from the earth. 

Naphthol Green B. A dye used in crystallizing solar salt, it increases the evaporation rate by added absorption of energy 5 ppm is said to increase salt production 15-20%. 

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