Water is the first need of industrial production. It covers three quarters of the earth's surface area. Since water can dissolve various substances in the crust and atmosphere to a certain extent, when water circulates underground, on the surface or in the air, it will contain certain suspended solids and dissolved solids: clay particles, animal and plant residues, plankton, bacteria, various salts and minerals (chlorides, sulfates, carbonates, iron and aluminum oxides, etc.), Organic substances and gases.

Water and its impurities, as well as impurities and impurities, are not simply mixed, but interact with each other, which determines the physical and chemical characteristics of natural water.

Impurities contained in water will scale and salt in the boiler water wall tubes and the steam flow passage in the water supply system of thermal power plants, which will cause corrosion on the metal surfaces contacting it and become an important reason affecting the safe and economic operation of thermal equipment. Therefore, according to the physical and chemical characteristics of natural water and its water quality type, necessary treatment shall be carried out before and after use to make it suitable for the intended use and relevant discharge standards.

In thermal power plants, petroleum and chemical industries, microelectronics industries, nuclear industries, food and pharmaceutical industries and other industries, water close to the quality of distilled water is required. With the rapid development of industrial technology, not only the water consumption is growing rapidly, but also the requirements for water quality are constantly improving.

Up to now, ion exchange is still the most important, advanced and economical water treatment technology. Whether it is softened water, demineralized water, demineralized water, pure water or ultrapure water, it is mainly prepared by ion exchange method. Industrial water treatment is the largest user of ion exchange resin. The resin consumed by industrial water treatment accounts for about 70% of the total output, both at home and abroad.

Chemical desalination refers to the process in which various ions contained in water are removed by ion exchange reaction with ion exchange resin, also known as ion exchange demineralized water treatment. When various cations in the water react with the cation exchange resin, the water only contains hydrogen ions exchanged from the cation exchange resin; After the various anions in the water react with the anion exchange resin, the water only contains hydroxide ions exchanged from the anion exchange resin. Hydrogen ions and hydroxyl ions can combine with each other to generate water, thus realizing chemical desalination of water. Obviously, the cation exchange resin used must be hydrogen type, and the anion exchange resin used must be hydrogen oxygen type. This is the basic principle of chemical desalting.

When various ions in the water are exchanged into hydrogen ions and hydroxyl ions, the deep chemical desalination of water is achieved. If certain cations or anions remain in the water, partial chemical desalting of the water is achieved.

In order to realize deep chemical desalination, a system with strong acidic cation resin and strong alkaline anion resin must be adopted. If only partial chemical desalination is achieved, various systems composed of cation resin and anion resin can be used, including the system composed of weak acid cation resin and weak base anion resin, as well as amphoteric resin unit equipment containing only weak acid groups and weak base groups.

After deep chemical desalting, a lot of surface water and well water can be made into pure water; After partial chemical desalting, surface water and well water containing more salt can be made into fresh water.