Solar pond evaporation

Solar evaporation Solarization Solar panels Solar ponds Solar power systems Solar radiation Solar salt... 

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). 

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. 

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,... 

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. 

A proposal is made to use a solar pond supply of bottom pond hot water at 100 kPa and 80° C to operate a steam turbine. The 100 kPa-pressure bottom pond water is throttled into a flash evaporator chamber, which forms liquid and vapor at a lower pressure of 20kPa. The liquid is discarded while the saturated vapor feeds the turbine and exits at lOkPa. Cooling water is available at 15°C. Find the turbine power per unit geothermal hot-water mass flow rate. The turbine efficiency is 80%. Find the power produced by the solar pond power plant. 

In this article only the term evaporation will be used. Evaporation will be defined as processes carried out in process equipment conventionally classified as evaporators. This, in turn, implies that nonequipment-contained classes of evaporation, such as solar ponds and oil tanker spills, will be ignored. 

Our objective in Ex 1.3 was the demonstratiou of a moving (evaporating or condensing) boundary in terms of a simple problem. Accordingly, we assumed the entire solar energy to be absorbed at the top surface of a liquid layer. In the more realistic case associated with solar ponds, this energy is absorbed over a thickness which may even extend beyond the depth of the pond. The present example deals with a simple problem for this case based on the assumption of a constant depth. 

Attempts to model solar pond operations have been made for existing commercial productions of Na2C03 IOH2O (Manguo and Schwartz, 1985) and KCl (Klein et aL, 1987). The use of weather-station data in the design and operation of solar ponds is discussed by Butts (1993) and correlations for solar evaporation rates using weather variables have been proposed by Lukes and Lukes (1993). 

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. 

This leads to the replacement of the impure mother liquor by the wash solution, before the suspension becomes separated on the centrifuge. It has the advantage that the mother liquor in the crude crystallization, respectively the second crop, can be more concentrated that is, higher yields can be realized. Even solid impurities can be separated, if their settling rates are smaller than those of the product crystals. This is, for example, the case in the recrystallization of table salt from solar salt or in the case of the direct evaporative crystallization from solar pond concentrates, where... 

In many cases, therefore, salt from solar ponds is processed downstream by some purification steps. These are, for example, a combined grinding and washing process or even the complete recrystallization by the evaporative vacuum crystallization. A modern alternative is the combination of the energy-saving solar pond concentration with industrial crystallization. In such cases, the seawater... 

Nowadays, there is the possibility to combine solar evaporation with modern salt crystallisation for improving salt quality. Figures 9.26 and 9.27 show the flow sheet of a sodium chloride crystallisation unit, which is energy saving-wise operated with concentrated liquor from a solar pond. 

A plant of this type was erected for the treatment of 601 h concentrated liquor from a solar pond on the coast of the Mediterranean Sea. The plant is producing 2.5 th grain-size salt of >2 mm average crystal size and 6.51 h" of normal vacuum salt. Per hour it consumes lit of steam and evaporates 341 of water. By... 

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