|M.Sc Student||Fine Larissa|
|Subject||Remineralization of Desalinated Water by Micronized CaCO3|
|Department||Department of Chemical Engineering||Supervisors||Professor Emeritus Raphael Semiat|
|Professor Emeritus David Hasson|
|Dr. Hilla Shemer|
The objective of this research was to investigate a novel process for re-mineralizing desalinated water with calcium and bicarbonate. The process is based on dissolution of a micron size calcite powder with either CO2 or H2SO4, in a pipe flow system. A pilot system was constructed providing dissolution of the calcite powder slurry under continuous mixed flow conditions.
Systematic experiments were carried out to measure the calcium and bicarbonate hardening levels obtained under different conditions. The parameters varied were the acidifying medium, the acid concentration, the inlet slurry concentration and the retention time. Two major series of experiments were carried out: runs at relatively long retention times and runs at relatively short retention times. Results of the experiments were compared to two derived theoretical models: a model describing dissolution under excess concentration of the powder relative to the acid concentration and a model describing dissolution under deficiency of the powder concentration relative to the acid.
The calcium and alkalinity levels measured in the long retention time experiments were found to provide conversions coinciding virtually with equilibrium conditions and, therefore, were not adequate for establishing the validity of the kinetic model. Results of all runs carried out at short retention times and low slurry concentrations showed excellent agreement with predictions of the kinetic models. As expected, a required calcium level may be achieved with a lower H2SO4 dosage as compared to CO2. Also, results show that steady state conditions are more rapidly achieved with H2SO4 as compared to CO2.
Preliminary cost estimates were carried out to evaluate remineralization of desalinated water by the acidified slurry powder dissolution technique as compared to remineralization by the conventional packed bed system. Using Mekorot published cost data, optimum conditions for powder dissolution were found to be at a retention time of 3 minutes and a split fraction of 0.36. Results indicate an economic advantage to remineralization of desalinated water by the acidified slurry powder dissolution process.