The results from an L9(34) OFF experiment design indicated that the flow rates on the feed and permeate sides are the principal factors controlling CMDC performance, whereas the temperatures either on the feed or permeate sides are not main factors. The optimal operating parameter values based on four factors and three levels are a flow rate and temperature on the feed side of 0.64 L min鈭? and 338 K, respectively, and on the permeate side of 0.35 L min鈭? and 303 K, respectively. These operating conditions not only affect the pure water and NaCl solid production, but also the quality of the crystals obtained from the crystallizer.
Factors affecting the crystal size distribution were investigated and indicated that the sodium chloride crystals had a narrow size distribution. The feed flow rate and inlet temperature had more influence on the mean crystal size and crystal size distribution, whereas the permeate flow rate and inlet temperature had relatively less effect. Therefore, CMDC operation was found not only to produce a high quality water product but also sodium chloride crystals with a relatively narrow size distribution. These results are beneficial to a better understanding of the CMDC process and improving its performance to realize zero salty water discharge to the environment.