Deionized water equipment

1. Equipment introduction

Deionized water equipment is an ion exchange system. Ion exchange occurs when water passes through an ion exchange column, exchanging cations and anions (such as HCO₄ ions) with the H+ of the cation resin and the OH₄ of the anion resin in the column, thereby achieving desalination. Different combinations of mixed cation and anion columns can achieve even higher water quality requirements. Ion exchangers are categorized as cation exchangers (softeners), anion exchangers, and mixed ion exchangers. Their disadvantage is that once the resin is saturated, it requires regeneration with acid or alkali.

2. Industrial process

Deionized water processes can be broadly categorized into four types:
The first method uses cation and anion exchange resins to produce deionized water. After passing through cation and anion exchange resins, the effluent conductivity can generally be reduced to below 10 µs/cm. Further processing through a mixed bed can reduce this to below 1 µs/cm. However, this method is costly and contains excessive particulate matter, making it less than ideal. It is now less commonly used.
The second method involves pretreatment (i.e., sand-carbon filter + precision filter) + reverse osmosis + mixed bed process.
This method is currently more commonly used because the investment cost of reverse osmosis is relatively low. It can remove over 90% of ions from water. The remaining ions are then removed through mixed bed exchange, resulting in an effluent conductivity of approximately 0.06.
The third method uses a two-stage reverse osmosis process.

 The process is as follows:

 Tap water → Multi-media filter → Activated carbon filter → Water softener → Intermediate water tank → Low-pressure pump → Precision filter → First-stage reverse osmosis → pH adjustment → Mixer → Second-stage reverse osmosis (positively charged reverse osmosis membrane surface) → Pure water tank → Pure water pump → Microporous filter → Water point

The fourth method uses reverse osmosis for pretreatment, similar to the second method, but the subsequent mixed bed uses EDI continuous desalination membrane blocks instead. This eliminates the need for acid-base regeneration resins, instead using electrical regeneration. This ensures a completely pollution-free process, and the treated water quality can reach over 15M. However, this method requires a relatively high initial investment, but operating costs are low. Investments should be tailored to each company's needs. The process is as follows:

 

Raw water → Multi-media filter → Activated carbon filter → Water softener → Intermediate water tank → Low-pressure pump → pH adjustment system → High-efficiency mixer → Precision filter → High-efficiency reverse osmosis → Intermediate water tank → EDI pump → EDI system → Microporous filter → Water point

3.Equipment process characteristics

 Ion exchange equipment is a traditional deionized water treatment system, offering stable water quality and relatively low cost. Traditionally, power plant boiler feed water treatment has utilized a cation bed, anion bed, and mixed bed process.

With the development of reverse osmosis and EDI processes, the drawbacks of ion exchange equipment, such as complex operation, difficulty in automation, waste of acid and alkali, and high operating costs, have become more prominent. Consequently, it is increasingly used in reverse osmosis advanced treatment.

Small ion exchange equipment often uses organic glass exchange columns, which facilitates observation of resin operation. This includes monitoring the adequacy of regeneration and stratification in mixed ion exchangers, cation poisoning, and resin loss. Large ion exchange equipment uses carbon steel lined with epoxy resin or rubber, with a central viewing device for online monitoring of the regeneration fluid level during ion regeneration.

4.Application areas

(1). Industrial ultrapure water treatment processes.
(2). In the food industry, ion exchange resins can be used in industrial equipment for sugar production, monosodium glutamate, wine refining, and bioproducts.
(3). In the synthetic chemistry and petrochemical industries, acids and bases are often used as catalysts for reactions such as esterification, hydrolysis, transesterification, and hydration in organic synthesis.

(4). Removal of metal ions from electroplating wastewater and recovery of useful substances from film production wastewater.

(5). In hydrometallurgy and other applications, ion exchange resins can be used to separate, concentrate, and purify uranium from depleted uranium ores, as well as to extract rare earth elements and precious metals.

5.Equipment classification

According to the different process water requirements and raw water quality of various industries, different industrial deionized water equipment can be customized to meet the water use standards.