In facilities when process steam is easily accessible, production of pure water from seawater is commonly carried out by multistage flash (MSF) and multi-effect desalination (MED) units. The major problem encountered is the deposition of scale onto the heat transfer surfaces which can lead to a serious loss of efficiency and production. CREST Water’s solutions for thermal desalination will help your plant operate at its optimum runlength and prevent unwanted shutdown of the plant for cleaning.
The scales that are found in thermal desalination units can be generally divided into two main types:
- Alkaline scales, e.g., calcium carbonate and magnesium hydroxide
- Non-alkaline scales, e.g., calcium sulphate
Some of the factors that influence the rate of formation of calcium carbonate and magnesium hydroxide in seawater include:
- concentration of bicarbonate ions,
- concentration of Ca2+ and Mg2+ ions, and
- total dissolved solids.
On the other hand, calcium sulphate exists in three forms: anhydrite, hemihydrate and gypsum. These forms of calcium are more soluble than calcium carbonate and magnesium hydroxide, and will form when the seawater is supersaturated with respect to calcium sulphate.
The CrestoPro T series of thermal antiscalants aim to control potential scale formation in both MED and MSF units to achieve their optimum distillate production. Our solutions have been built upon the proven enhanced maleates chemistries and some further improved to suit today’s ever-changing landscape as your plant seeks to product more pure water. To complement our thermal antiscalant range of products, CrestoPro T635 is a non-silicone based antifoam, incorporating a wetting agent to help reduce the tendency of hot spots forming on the tubes in a MED unit.
Along with monitoring tools and the technical know-how to interpret operating parameters before selecting and applying the appropriate thermal antiscalant solutions, our team of experts will work together with you to achieve your goals.