Principle of equipment setting in chemical demineralization system
(1) The cation exchanger is located in front of the anion exchanger. The reasons are as follows: a. the exchange capacity of strong base anion exchange resin is low, and the ion exchange reaction efficiency of strong base anion resin in acidic water (H-type cation resin exchange water) is high, and the working exchange capacity can be fully utilized. b. After the raw water is exchanged by H-type cation resin, the generated H2CO3 can be removed by decarbonizer, reducing the load of anion exchanger. c. If the raw water passes through the hydroxide anion exchanger first, calcium hydroxide precipitation will be generated.
(2) Decarbonizer is set in front of anion exchanger. However, when the alkalinity in raw water is ≤ 0.6mmol/l, decarbonizer can not be set.
According to the above, the simplest chemical desalination system is:
Raw water → cation exchanger → decarbonizer → anion exchanger → demineralized water
The system that carries out one cation and anion exchange reaction in sequence is called the primary chemical desalination system. The system for sequential secondary cation and anion exchange reaction is called secondary chemical desalination system.
(3) After primary chemical desalting, there is almost no CO2 or HCO3 - in the water, so decarbonizer will not be set in the secondary desalting system.
(4) In order to realize the deep desalination of water, in addition to the multi-stage cation and anion exchange reaction system, one-stage desalination and mixed bed can also be used. Infinite multistage cation and anion exchange reactions are realized in the mixed bed. Due to the minimal counter ion effect, this reaction is quite thorough and the effluent quality is very high.
(5) When the raw water quality is poor, the operation cycle of the exchanger of the primary desalination system is short, and the consumption of acid and alkali regenerants is large, the combined application process of strong and weak resin can be adopted. The process gives full play to the characteristics of large exchange capacity of weak resin and high regeneration efficiency, and expands the applicable water quality range of chemical desalination.
English
