Separation process for the recovery of desalted water and chemical products from indigenous saline water resources
[Thesis]
A. A. Ibrahim
King Fahd University of Petroleum and Minerals (Saudi Arabia)
1993
399
Ph.D.
King Fahd University of Petroleum and Minerals (Saudi Arabia)
1993
A modified Solvay process was experimentally carried out for the separation of sodium chloride salt from highly saline indigenous water resources. The technical viability of the process as a non-conventional approach to desalination was investigated. The proposed process utilizes a series of chemical reactions involving the conversion of both usdNa\sp+usd and usdCl\sp-usd into usdNaHCO\sb3usd that precipitates under experimental conditions and usdNH\sb4Clusd which can be separated by crystallization respectively. Synthetic saline and sabkha waters were used. The effects of relevant parameters on the conversion (such as temperature, initial concentrations of usdNH\sb3usd and NaCl, and usdNH\sb3usd/NaCl ratio), were studied. The optimum values of operating temperature and pH range are found to be 22 and 8-10, respectively. A higher concentration of usdNH\sb3usd enhances the separation, while a higher concentration of NaCl reduces the conversions, and an optimum value for the ratio of usdNH\sb3usdNaCl is found to be 1.2. The maximum conversions obtained were 82.2% and 66.7% for the synthetic saline and the sabkha waters, respectively. Hydrodynamic parameters of the bubble column (reactor), in which carbonation of an ammoniated brine occurs, are reported. These include: interfacial area, mass transfer coefficient, gas holdup and mixing efficiency. The absorption process was shown to be an instantaneous diffusion-controlled chemical reaction. A mathematical model involving the formulation of an algorithm to find the values of unreacted ammonia and unconverted sodium chloride in water is presented using the concept of mass balance and the fundamentals of chemical reactions. The free energy of formation of terminal chemical products is utilized to drive the reactions, and the total Gibbs free energy for the conversion of NaCl solution of 20% by weight into usdNaHCO\sb3usd and usdNH\sb4Clusd has a value of 85.4kJ/kg.