Thermal desalination processes involve the heating of seawater to form water vapor which is then condensed to produce salt ffee water. Multiple Effect Evaporation (ME) and Multiple-Stage Flash distillation (MSF) are the two main processes used for thermal distillation. MSF distillation, currently is the dominant process. MSF distillation is run under pressure at relatively high temperatures (90- 125 °C). Scale formation is one of the most critical problems affecting both processes. In the case of MSF, calcium carbonate, magnesium hydroxide and calcium sulfate are the main scale forming salts. The fwst two scale former salts are usually controlled by keeping neutral the pH of the system by the addition of acid. Scale inhibitors are used to prevent calcium sulfate scale. Because of economical reasons, the trend in the industry is to operate systems at as high a temperature and concentration factor as possible in order to increase purified water production at a lower cost. Safety concerns have also increased the need for acid feed elimination as a mean of controlling pH. These practices increased the scaling tendencies in MSF processes and created the need for more effective treatment programs to control scale formation on heat exchangers. A new multicomponent
inhibitor program that enable operation of MSF systems without the need of acid feed for pH control has been developed. The program prevent scale formation and allows to operate the system under typical or higher concentration factors and temperatures than normally found in MSF evaporators operating with acid feed.