Pretreatment of Seawater Using Precipitation Agents to Retard Scale Formation in Multi-Stage Flash Evaporators

The objective of this study is to investigate the formation of scale at the level of multi-stage flash evaporators (MSF). Scale (tartar) is the result of the precipitation of insoluble species such as calcium sulfate, calcium carbonate, and magnesium hydroxide. As a solution to this problem, we propose to pre-treat seawater before introducing it into evaporators. Pre-processing by the precipitation process is a method that protects evaporators (MSF). Our strategy consists of pre-treating seawater by three different ways using potassium hydroxide at a temperature of 25 ℃, sodium carbonate at different temperatures 25, 35, 50, and 100 ℃, and the combination of potassium hydroxide and sodium carbonate at 25 and 100 ℃. As a result, we noticed that the treatment of 1 L of seawater heated at 100 ℃ using 10 g of sodium carbonate completely eliminated the calcium ions and reduced the concentration of magnesium ions from 747.22 to 142.8 mg/L. The treatment of the filtered solution of 10 g/L of sodium carbonate heated to 100 ℃ with 3 g of potassium hydroxide, however, allowed the removing of the remaining magnesium ions. On the other hand, the pre-treatment of seawater carried out with a mixture of sodium carbonate and potassium hydroxide and heated at 100 ℃ gave the best result through the total elimination of both ions of sodium carbonate and magnesium.