Application of integrated solar pond with evaporation system for heat generation to recover minerals in rejected brine

Desalination plants are known to discharge large value of brine as waste from the distillation process which is increasing globally over time. Although the desalination techniques has a positive impact to the eco-socio and industrial sector by solving the problem of water shortage, it also contributes negatively to the environment during discharge of the concentrated brine back to the sea or landfill. However, the treatment of the brine could be effectively utilized by converting it into by-products via solar pond technology. Generation of heat using solar pond technology has certain limitations, but in case of Saudi Arabia all these limitations can be effectively addressed. This research focused on the use of a solar pond with the integration of heat, power and the concentrated brine. The result from the characteristics of seawater and brine demonstrated that the level of mineral and salt in brine was very high compared to sea water. With respect to economic value of the minerals, it was found that a potential revenue of 18.46 billion USD/per year in brine at AL-Khobar desalination plant is from Na+, Mg2+, K+, Ca2+ and Cu2+. To recover minerals, evaporation pond used to evaporate water from brine with the integration of solar pond for heat generation. For the designing and fabrication of the solar pond, it was found that the maximum temperature of about 65ºC could be generated from solar pond. The experiment on evaporation rate using the evaporation pond showed that the best temperatures were from 45 oC to 70 oC, where evaporation rate increases linearly over the increment of temperature. This temperatures are used for faster evaporation to make brine more concentrate which have about 5% moisture content. This moisture need to be dried further to meet salt market specification over the world, and produced salt could be used for multiple purpose.This research used microwave oven for salt drying process which was powered by solar PV technique. For harvesting maximum radiation of PV tracking surface, it should be determine the angle of PV setup to use the output power for powering microwave which required 700 watts power for operation. The gain made by this tracker relative to flat plate collector was 35% and 81% in the summer and winter solstice days,respectively. Four solar panels were set at 27 degree to obtain maximum output to operate the microwave. It was found that, microwave drying process achieved faster drying by 16 times compared to the conventional heating on an average. The research has shown the best concept of recovering minerals from brine, using the integrated solar pond with evaporation pond by utilizing a PV panel to powering microwave.

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