| Pretreatment process of seawater distillation (Multi-Effect Distillation, Multi-Stage Flash, etc.) is to remove particles, molecules and ions like suspended solids, colloidal, carbon dioxide and oxygen, thus reducing the impact of scaling or corrosion. On the other hand, with the continuous development and application of Low-Temperature Multi-Effect Desalination (LT-MED) technology, higher top brine temperature has become one of the major issues. However, what comes next is the scaling problem of heat transfer surfaces. Thus, the success of distillation desalination and its further development depends primarily on the reasonability of pretreatment process.This paper analyzes two different types of scale samples encountered in the lab experiments of LT-MED system, (a gray-brown chunky scale sample of mixed solid particles; a blocky transparent solid scale sample mixed with a small amount of gray brown fine solid particles). Scale samples were studied by water/acid-base solubility experiments, loss on drying and elemental analysis to determine the compositions, and then the formation and the prevention and treatment methods were discussed.Raw water samples with pH value of 8.5,28℃, turbidity of 44.57NTU were studied by a set of enhanced-coagulation pretreatment experiments. Orthogonal experiments were made to study the impact factors of turbidity like adding concentrations and types of coagulations, mixing time, water quality, pH value of water, etc. to determine the optimal operating scheme of coagulation process.An optimized design of large scale LT-MED pretreatment technology is presented to investigate the process design and verification of pretreatment equipments-vacuum degassing tower and multi-media filter to offer a design basis for implementation and operation of seawater desalination plant.For small scaled seawater desalination equipments, Fluent is used to simulate the fluid flow and heat transfer characteristics in the Plate Heat Exchanger.
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