And solar ponds

However, the phenomena of super-saturation of brines containing magnesium sulfate, borate is often found both in natural salt lakes and solar ponds around the world. Especially for salt lake brine and seawater systems, the natural evaporation is in a autogenetic process with the exchange of energy and substances in the open-ended system, and it is controlled by the radiant supply of solar energy with temperature difference, relative humidity, and air current, etc. In other word, it is impossible to reach the thermodynamic stable equilibrium, and it is in the status of thermodynamic non-equilibrium. 

Gale (1945). Garrett (1996) (Searles Lake, Upper and Lower Structure brine Sau Pan, Botswana Bonneville Salt Flats, Utah, brine and solar pond end liquor). ... 

Other salts crystallize. Lake Abijdata in Ethiopia has similar brines and solar ponds, but is a much smaller soda ash operation. The Sebka El Adhibate, Tunisia has about a 16 ppm Li concentration in a seawater-type brine, and after solar evaporation for potential potash production the end-liquor would contain 250-340 ppm Li (Hamzaoui et al, 2000). There are several other solar evaporation or mineral recovery projects throughout the world with end-liquors that might also be considered for potential lithium recovery. 

At Great Salt Lake Minerals Corporation (Utah), solar-evaporated brines are winter-chilled to —3° C in solar ponds. At this low temperature, a relatively pure Glauber s salt precipitates. Ponds are drained and the salt is loaded into tmcks and hauled to a processing plant. At the plant, Glauber s salt is dissolved in hot water. The resulting Hquor is filtered to remove insolubles. The filtrate is then combined with soHd-phase sodium chloride, which precipitates anhydrous sodium sulfate of 99.5—99.7% purity. Great Salt Lake Minerals Corporation discontinued sodium sulfate production in 1993 when it transferred production and sales to North American Chemical Corporation (Trona, California). 

A third source of brine is found underground. Underground brines ate primarily the result of ancient terminal lakes that have dried up and left brine entrained in their salt beds. These deposits may be completely underground or start at the surface. Some of these beds ate hundreds of meters thick. The salt bed at the Salat de Atacama in Chile is over 300 m thick. Its bed is impregnated with brine that is being pumped to solar ponds and serves as feedstock to produce lithium chloride, potassium chloride, and magnesium chloride. Seades Lake in California is a similar ancient terminal lake. Brine from its deposit is processed to recover soda ash, borax, sodium sulfate, potassium chloride, and potassium sulfate. 

Solar Evaporation. Recovery of salts by solar evaporation (1 3) is favored in hot dry climates. Solar evaporation is also used in temperate 2ones where evaporation exceeds rainfall and in areas where seasons of hot and dry weather occur. Other factors (4,5) affecting solar pond selection are wind, humidity, cloud cover, and land terrain. 

Solar ponds are typically 15—50 cm deep. They are usually built over flat areas, where silts and clays have settled to make a tight soil base to prevent leakage through the bottom of the pond. In areas where soils are not tight, artificial liners of mbber or poly(vinyl chloride) (PVC) are used. 

Until the 1970s, solar ponds were constmcted and operated as more of an art than a science. Since then, rising land value, environmental conscientiousness, limited space, and rising costs have forced a scientific approach to solar pond optimization, design, and operation to make ponds more productive. 

In 1981, seven faciUties extracted minerals from Great Salt Lake brine, but flooding in 1983 and 1984 reduced the number to five. By 1992, four companies were operating. AH Great Salt Lake mineral extracting faciUties have solar ponds as the first stage in processing minerals from brine. 

Recovery Process. Lithium is extracted from brine at Silver Peak Marsh, Nevada, and at the Salar de Atacama, Chile. Both processes were developed by Foote Mineral Corp. The process at Silver Peak consists of pumping shallow underground wells to solar ponds where brines are concentrated to over 5000 ppm. Lithium ion is then removed by precipitation with soda ash to form a high purity lithium carbonate [554-13-2]. At the Atacama, virgin brine with nearly 3000 ppm lithium is concentrated to near saturation in lithium chloride [7447-41 -8]. This brine is then shipped to Antofagasta, Chile where it is combined with soda ash to form lithium carbonate. 

Recovery Process. The Texas Gulf, Cane Creek potash operation (60) of Moab, Utah produces KCl by solution mining (61—64). Brine is pumped from underground to 1.6 x 10 (400 acres) of solar ponds where a mixture of KCl and NaCl is crystallized in a salt mass called sylvinite. 

Production of KCl at the Wendover, Utah operation employs a large 7000 acre complex of solar ponds. Both shallow brine wells and deeper wells are used to pump brine into the pond complex. In the preconcentration ponds water is evaporated and sodium chloride is crystallized. Later the brine is transferred to production ponds where sylvinite is deposited. Brine is then transferred to other ponds where camaUite is crystallized. Sylvinite is removed from drained ponds with self-loading scrapers and taken to the plant were KCl is separated by flotation with an amine oil collector. The camaUite,... 

Great Salt Lake Minerals Corp. near Ogden, Utah, produces potassium sulfate and several other products from Great Salt Lake brines. Presently 81 X 10 (20,000 acres) is divided into 80 solar ponds with 81 million m of expansion scheduled in 1992. Two years are requked to process brine... 

Recovery Process. Figure 5 shows a typical scheme for processing sodium chlodde. There are two main processes. One is to flood solar ponds with brine and evaporate the water leaving sodium chlodde crystallized on the pond floor. The other is to artificially evaporate the brine in evaporative crystallizers. Industrial salt is made from solar ponds, whereas food-grade salt, prepared for human consumption, is mosdy produced in the crystallizers. 

Factors considered to affect pond performance are air temperature, relative humidity, wind speed, and solar radiation. Items appearing to have only a minor effect include heat transfer between the earth and the pond, changing temperature and humidity of the air as it traverses the water, and rain. 

A solar pond does not concentrate solar radiation, hut collects solar energy in the pond s water by absorbing both the direct and diffuse components of sunlight. Solar ponds contain salt in high concentrations near the bottom, with decreasing concentrations closer to the surface. This variation in concentration, known as a salt-density gradient, suppresses the natural tendency of hot water to rise, thus... 

BASE AND METHODOLOGY FOR THE ESTIMATION OF WORKER INJURY RATES. THERMAL ENERGY STORAGE SYSTEMS. ROUTINE FAILURE HAZARDS. OFF-NORMAL EVENTS. SOLAR PONDS. (1979) (Spon-... 

Build a small-scale model of a solar pond and test how it traps and stores solar energy. 

Collect temperature data as the solar pond model heats and cools. 

Position the 150-watt lightbulb about 15 to 20 cm over the top of the solar pond model. Turn on the light. Press ENTER on the calculator to begin collecting data. After about 6 to 8 minutes, turn off the lightbulb and move it away from the solar pond model. Do not disturb the experiment until the calculator is finished with its 30-minute run. 

Comparing and Contrasting Which layer of your solar pond model did the best job of trapping and storing heat ... 

The El Paso Solar Pond was the first in the world to successfully use solar pond technology to store and supply heat for industrial processes. It was built with three main layers a top layer that contains little salt, a middle layer with a salt content that increases with depth, and a very salty bottom layer that stores the heat. Which layer has the greatest density The least density Why doesn t the storage layer in the El Paso Solar Pond cool by convection ... 

Finkelstein, E. J. Heat Recovery Syst. 3 (1983) 431-437. On solar ponds critique, physical fundamentals and engineering aspects. 

Much of this chapter has been concerned with various modifications to the simple Rankine cycle at high temperature. In the following five sections, the Rankine cycle that makes possible use of energy sources at low temperature, such as solar, geothermal, ocean thermal, solar pond, and waste heat, will be discussed. Because of the small temperature range available, only a simple Rankine cycle can be used and the cycle efficiency will be low. This is not critical economically, because the fuel is free. 

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