Kore, Sileshi (2006) Modeling and Simulation of Solar Evaporative Crystallization of Lake Brine (The Case of Lake Abijata/Shalla). Masters thesis, Addis Ababa University.
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Abstract
Abijata Lake water constitutes the raw material for the production of salt in solar salt works. The salts are: Industrial salts------Sodium carbonate (Na2CO3) Edible salt-----------Sodium chloride (NaCl) The concentration of the Lake water through solar evaporation results in the successive crystallization of less soluble salts (Na2CO3, NaHCO3) first, followed by NaCl. Salt work uses the empirical Baume (OBe) Scale, to measure the concentration of the brines. According to that scale the Lake water concentration is 4.22 OBe (specific gravity of 1.03).The crystallization of Trona (Na2CO3.NaHCO3.2H2O) begins at 26.13 OBe (specific gravity of 1.22) and sodium chloride (NaCl) crystallize at 39.16 OBe (specific gravity of 1.37) Solar crystallization Processes Producing salt from the lake water involves the selective recovery of pure Trona (Na2CO3.NaHCO3.2H2O) and sodium chloride (NaCl), free of other soluble or non-soluble salts and other substances. To this end, an appropriate quantity of Lake Water is concentrated through natural evaporation, which leads to the fractional crystallization of all salts contained: a process based on their varying solubility. The basic step in the processes of salt recovery from the Lake water was made with the division of the evaporation basins in to two: The first basin, usually called nurse pond (pre-concentration pond), was used for the production of saturated brine, which was feed in to second basin, usually called crystallizer. What basically elevates Salt works to ecosystem is the fact for Lake Water to be concentrated up to the point salt crystallization. 90% of its salt content has to be evaporate, thus requires a vast surface. For this reason ponds (pre-concentration ponds) take up 90% of the salt work area. Crystallizers take up approximately 10% of the salt work area. Crystallizes take up the remaining 10% of the area. These basins are especially designedix and have their bottom leveled and concentrated, aiming to facilitate and optimize the collection of salt with machinery. The first pond of the salt work is feed with Lake Water (raw material) usually via pumping. As the lake water flows along the pond, its concentration raises continuously through natural evaporation. The evaporation (concentration) of brine is achieved by exposure to solar radiation and with the help of the prevailing microclimate in the area, especially the winds, rainfall, air temperature and humidity and duration of sunshine. So an increasing salinity (concentration) gradient is created throughout the ponds of the salt works with a simultaneous and continuous reduction of the volume of Lake Water, which initially entered the system of ponds. This is the physicochemical process of salt production.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Mechanical Engineering |
| Subjects: | Q Science > Q Science (General) T Technology > T Technology (General) T Technology > TC Hydraulic engineering. Ocean engineering T Technology > TJ Mechanical engineering and machinery T Technology > TK Electrical engineering. Electronics Nuclear engineering |
| Divisions: | Africana |
| Depositing User: | Andriamparany Edilbert RANOARIVONY |
| Date Deposited: | 27 Nov 2018 13:07 |
| Last Modified: | 27 Nov 2018 13:07 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/7750 |
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