Experimental study of forced circulation evaporator in zero discharge desalination process

Zero discharge desalination process is the most promising technology to prevent salinity and thermal shocks to ecosystem by effluent streams of desalination unit drained into the sea. Pretreatment, solar pond and forced circulation crystallizer are the major steps of one option to provide the purposes of zero discharge desalination process. Reduction of total hardness of wastewater occurs in pretreatment unit and the solar pond is proposed for effluent concentrated brine wastewater of pretreatment unit which seeks production of potable water and concentrated brine.The effluent stream from solar pond is conveyed to one forced circulation evaporator in order to produce salt and distilled water. This work presents the effective optimum parameters of one forced circulation evaporator such as occupied capacity of crystallizer main body, residence time, optimum temperature of heat exchanger, flow rate of cooling water, color and size distribution of salt crystals, amount of distilled water and energy consumption. Results show that the suitable range of crystal growth (700–830 μm) occurs when the occupied capacity of crystallizer is 70%. Also, the flow rate of cooling water in condenser is 10 kg/min and the efficient residence time is 4 h.

► Optimum operating conditions of a forced circulation evaporator are investigated.
► Occupied capacity of evaporator and temperature of heat exchanger are surveyed.
► Color, size distribution of salt crystals and energy consumption are surveyed.
► Best crystal growth in the range of (700–830 μm) is occurred.
► Optimum cooling water flow rate and residence time is 10 kg/min and 4 h.