Studies on a polyoxypropylene glycol-based antifoaming agent in MSF plants

Salt carry-over due to excessive foaming in a multistage flash (MSF) distil ler and detrimental foaming in the deaerator section have been reported in the Saline Water Conversion Corporation (SWCC) of Saudi Arabia and other de salination plants. The application of a suitable antifoaming agent has prev ented distillate contamination and improved release of dissolved oxygen in the deaerator section, thus improving the operating efficiency of MSF plant s. The developer of a polyoxypropylene glycol-based antifoaming agent colla borated with SWCC in carrying out trial runs to show that their product was as effective and economical as the one currently being used (a polyglycol blend in a hydrocarbon solvent) in SWCC plants. Trial tests were carried ou t at laboratory, pilot and commercial plant levels. Miscibility of this age nt in water was determined initially in the laboratory, followed by field t rial runs in an MSF pilot plant and the commercial plants of Al-Jubail I an d II. Foam control, non-interference with antiscalant performance, distilla te purity and stability at a low dose rate over a wide range of temperature s were some of the important criteria evaluated during testing of this anti foaming agent. During MSF plant runs, distillate conductivity and dissolved oxygen level in the feed were regularly monitored and found within the acc eptable limits. Compatibility of this agent with antiscalant was also asses sed. Heat transfer and plant performance data were found satisfactory confi rming that this agent did not exhibit any adverse effect on the antiscalant used in Al-Jubail plants. Results of laboratory and field trial runs of th is antifoaming agent are discussed.