USING DIFFERENT TYPES OF ANTI-SCALANTS AT THE AL-JUBAIL POWER AND DESALINATION PLANT IN SAUDI-ARABIA

The purpose of this paper is to review the results of using different types of anti-sealant chemicals at the Al-Jubail Desalination Plant. A major problem in the desalination of sea-water is the scaling that ta kes place. During the desalination process brine flows inside heat tra nsfer tubes causing a rapid growth of scale within the tubes which eve ntually results in a deterioration of plant performance. The desalinat ion plant at Al-Jubail is considered to be the largest of its kind in the world and is capable of producing 240 migd at a low top brine temp erature of 90 degrees C and 281.6 migd at a high TBT of 112.8 degrees C. Experience has shown that there are only two practical methods to p revent scale in a MSF plant, namely treatment of the scale by acid or by the use of chemical additives. The evaporators used at the plant we re designed to use additive scale control method. Treatment of scale w ith arm acid has not yet been used at the plant to clean the evaporato rs or Condensers. Two different types of anti-sealant treatments are u sed at the plant which are classified into three anti-sealant groups n amely; poly-maleic acid, poly-phosphate and poly-phosphonate. This pap er will compare the results experienced using the above chemicals. Thi s gaper will also discuss the necessity of anti-sealant selection for every operating mode in MSF evaporators. Factors will be reviewed to a ssess and evaluate the quality and performance the anti-sealant. Speci fications of all the above chemicals is provided to assist in the sele ction of anti-sealants by other users without the need for expensive t ests and trials.