Dear  Stephen, The disposal ...

Dear  Stephen,

The disposal or management of desalination brine (concentrate) is expensive and faces major environmental challenges. In spite of the scale of this economical and environmental problem, the options for brine management have been limited. This brief review presents an overview of the existing methods on brine treatment, minimization, and disposal practices based on the newest and most updated technologies. Calcium sulfate is the predominant chemical compound present in the feed to the brine concentrator.It is desirable to maintain operation at design conditions to help prevent scale deposits.calcium sulfate scale is more soluble than other mineral scales such as CaCO3, BaSO4, and SrSO4, once it has developed it is difficult to eradicate mechanically and is insoluble in mineral acids and other conventional solvents.

High TDS and saturation of low-solubility scaling salts such as calcium sulphate (CaSO4) and silica (SiO2) limit the percentage of water that can be recovered in a conventional evaporator system.The brine concentrator uses a unique process called seeded slurry evaporation to overcome the limitation imposed on conventional evaporators by the saturation limits of low solubility scaling compounds. The seeded slurry process involves establishing and maintaining slurry of CaSO4 seed crystals in the circulating brine in the evaporator. With careful thermal and mechanical design, CaSO4 and SiO2 can precipitate preferentially on the recirculating seed crystals instead on the tubes. The ultimate concentration achievable in the brine concentrator is limited by the boiling point elevation of the brine, the relative concentrations of sulphate and chloride (e.g. the double salt, CaSO4•Na2SO4 does not form), and the solubility of the sodium salts. The brine discharged from the brine concentrator is further concentrated in the crystallizer.

Following are the procedure of Scaling removing,

1. Muraitic acid to be used for descaling
2. Vinegar also to be used for descaling
3. High pressure water jetting about 300-400 bar to be used.
4. ​Install a ball cleaning system to keep the ​internal walls. Intermediate brine treatment process to remove scale-forming chemicals
5. Mechanical brushing to be done.
6. To prevent the scale formation sulfuric acid is added to the feed tank to react with the calcium carbonate.
7. Addition of anti-scale compounds such as sodium hexametaphosphate (NaPO3)
8. The high tubes velocities help reduce scale formation. Low velocity promotes sedimentation of the salts causing scaling.
9. Lime softening is used for the removal of sulfate via the precipitation of gypsum (CaSO4•2H2O).