Evaporation of brine

Parallel feed involves the introduc tion of raw feed and the withdrawal of produc t at each effect of the evaporator. It is used primarily when the feed is substantiallv saturated and the product is a sohd. An example is the evaporation of brine to make common salt. Evaporators of the types shown in Fig. 11-122Z or e are used, and the produc t is withdrawn as a shiny. In this case, parallel feed is desirable because the feed washes impurities from the salt leaving the body. 

The Zag meteorite fell in the western Sahara of Morocco in August 1998. This meteorite was unusual in that it contained small crystals of halite (table salt), which experts believe formed by the evaporation of brine (salt water). It is one of the few indications that liquid water, which is essential for the development of life, may have existed in the early solar system. The halite crystals in the meteorite had a remarkably high abundance of 128Xe, a decay product of a short-lived iodine isotope that has long been absent from the solar system. Scientists believe that the iodine existed when the halite crystals formed. The xenon formed when this iodine decayed. For this reason, the Zag meteorite is believed to be one of the oldest artifacts in the solar system. In this lab, you will use potassium-argon radiochemical dating to estimate the age of the Zag meteorite and the solar system. 

Sediment usually consists of finely divided solids that may be dispersed in the oil or carried in water droplets. The solids may be drilling mud or sand or scale picked up during the transport of the oil, or may consist of chlorides derived from evaporation of brine droplets in the oil. In any event, the sediment can lead to serious plugging of the equipment, corrosion due to chloride decomposition, and a lowering of residual fuel quality. 

The use of open pits or ponds for evaporation of brine is widely practiced in southwestern states where evaporation exceeds precipitation [23]. For example, about 75% of all oil and gas waste fluids are disposed of by evaporation pits in New Mexico [30]. Evaporation ponds require large land areas, and they may contaminate groundwater. Today regulators view evaporation pits with disfavor because faulty pond design and operation have allowed salts to migrate into usable groundwater reservoirs [9]. 

Frantz, J.F., The evaporation of brine solutions in a fluidized salt bed, PhD thesis, Louisiana State University, 1958. 

Lithium may be recovered from natural chloride brines. Such recovery processes may require additional steps depending on the magnesium and calcium content of the brine. The process involves evaporation of brine, followed by removal of sodium chloride and interferring ions such as calcium and magnesium. Calcium is removed by precipitation as sulfate while magnesium is removed by treating the solution with lime upon which insoluble magnesium hydroxide separates out. Addition of sodium carbonate to the filtrate solution precipitates hthium carbonate. 

The Stassfurt deposits have been the subject of elaborate investigations by J. H. van t Hoff and his school.16 In 1849, J. Usiglio 17 studied the deposition of salts when sea.water is cone, by evaporation, and examined the residues analytically. He found that calcium carbonate was first eliminated, then calcium sulphate, then sodium chloride, and the more soluble salts accumulated in the mother liquid. This method of investigation does not allow sufficient time for the various salts to attain a state of equilibrium, and it therefore follows that the natural evaporation of brines probably furnishes somewhat different results. Moreover, it is difficult, if not impossible, to identify the several substances which separate from the mother liquid formed during the later stages of the evaporation. J. H. van t Hoff followed the synthetic method in his study of this subject. He started from simple soln. like those of sodium and potassium chlorides, under definite conditions of temp., and gradually added the pertinent constituents until the subject became so complicated that the crystallization of the constituents from concentrating sea water was reduced to a special case of a far more comprehensive work. 

Many special types of equipment have been developed for particular industries, possibly extreme examples being the simple open ponds for solar evaporation of brines and recovery of salt, and the specialized vacuum pans of the sugar industry that operate with syrup on the tubeside of calandrias and elaborate internals to eliminate entrainment. Some modifications of basic types of crystallizers often carry the inventor s or manufacturer s name. For their identification, the book of Bamforth (1965) may be consulted. 

Grainer salt is made by surface evaporation of brine in flat pans open to the atmosphere. Heat usually is furnished by steam pipes located a few inches below tlie tank bottom. Crystals form at the surface of the brine and are held tliere temporarily by surface tension. Thus, they grow laterally for awhile and form thin flakes. But, as they grow, they tend to sink and this process imparts a peculiar, hollow pyramid-like structure to them. Such crystals are called hopper crystals. Ultimately, the crystals sink to the bottom where they are scraped to one end of the pan. The crystals are fragile and during handling they break up, finally assuming a flake-like shape. Thus, tlie term flake salt. 

Sodium compounds are important largely because they are inexpensive and soluble in water. Sodium chloride is readily mined as rock salt, which is a deposit of sodium chloride left as ancient oceans evaporated and it is also obtained from the evaporation of brine from present-day seas and salt lakes (Fig. 14.19). Sodium chloride is used in large quantities in the electrolytic production of chlorine and sodium hydroxide from brine. 

Evaporation of brine in a basin-type still can be carried to high concentrations without precipitation. 

The elements of group I (Li, Na, K, Rb, Cs, Fr) are collectively known as alkali metals. They occur in nature only as +1 ions. They are the most electropositive in nature and their compounds are most ionic. The salts of alkali metals are quite soluble in water and thus they are found in large quantities in water and salt deposits which have formed by the evaporation of brine. However many in soluble clays also contain alkali metals as complex metal silicates. 

Turk, L. J. Evaporation of brine A field study on the Bonneville Salt Flats, Utah. Water Resour. Res. 1209-1215 (1970). 

Jones B. F., Carmody R. and Frape S. K. (1997) Variations in principal solutes and stable istopes of Cl and S on evaporation of brines form the Great Salt Lake, Utah. Geological Society of America, Abstracts with programs, vol. 29, no. 6, p. 261. 

Potassium chloride occurs naturally as the mineral sylvite or sylvine it also occurs in other minerals such as sylvinite, camallite, and kainite. Commercially, potassium chloride is obtained by the solar evaporation of brine or by the mining of mineral deposits. 

All calculations are made relative to one kg H2O. As there is no mass balance for the elements H and O, there is no formal provision for keeping track of the amount of water used in reactions such as hydration and dehydration of solids. This is a source of error, for example, in simulation of the evaporation of brines when hydrated minerals are precipitated and remove water from solution. 

The evaporation of brines in shallow ponds, using energy from solar radiation, has been practised for thousands of years and still provides an important means of recovering salts from saline waters in many parts of the world (Sonnenfeld, 1984). An excellent example is the recovery of salts from Dead Sea waters (Novomeysky, 1936). 

The distribution of the coUecting sites along the eastern margin of the Lewis CUff ice tongue and within the adjacent ice-cored moraine ridges indicates that the minerals formed both by evaporation of brines that were extruded through near-vertical fractures in the ice as well as by subglacial precipitation. The salt deposits that occur in the soil of the ice-free vaUeys and associated with saline lakes and ponds in this area are presented in Chapter 19. 

Parallel-feed multiple-effect evaporators. Parallel feed in multiple-effect evaporators involves the adding of fresh feed and the withdrawal of concentrated product from each effect. The vapor from each effect is still used to heat the next effect. This method of operation is mainly used when the feed is almost saturated and solid crystals are the product, as in the evaporation of brine to make salt. 

Salt was obtained by lixiviating salt earth or pulverized salt rock. The operations involved included outcrop mining, pulverizing, hydrolysis, filtration and crystallization. Effluent was separated for alternative uses as manure and asphalt. Solar evaporation of brine of natural springs was done in large masonry evaporation pans. Salt has also been produced by boiling... 

Sodium chloride occurs in nature as mineral halite, and is produced by mining, by evaporation of brine from imdergroimd salt deposits, and from sea water by solar evaporation. It is white, odorless and has a saline taste, the pharmacopeial specifications are as follows. 

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