The daily operation of the ion exchange method used to prepare pure water consumes a lot of acid and alkali, and produces a lot of waste water, and the treatment cost is high. If Na-type resin is used for softening treatment, the cost of purchasing industrial salt is higher, which may be brought into the regeneration process. A large amount of Cl-ion increases the corrosion tendency of cooling water.
The application of weak acid cation exchange resin in water softening treatment can effectively remove carbonate hardness in water (in theory, the hardness can be removed to the equivalent of HCO3-alkalinity), and its working exchange capacity is more than twice that of strong acid resin (Usually it can reach 2000 mmol/L), the regenerant consumption is about 1.05 to 1.10 times the theoretical value, so it is very economical. The regenerant can be hydrochloric acid or sulfuric acid (the cost of the former is 3 times that of the latter), but when sulfuric acid is used, the concentration and flow rate of the regenerant must be strictly controlled to suppress the formation of CaSO4. The use of dual-flow ion exchanger can save investment, water consumption and land occupation, and can obtain higher regeneration efficiency.
Research on the use of weak acid resins for side-stream treatment of circulating cooling water began in 1998. Studies have shown that the construction scale of the weak acid system is related to the alkalinity that the circulating cooling water scale inhibitor can maintain. The higher the alkalinity, the smaller the throughput and the better the economy. The disadvantage of the weak acid resin softening process is that the presence of suspended solids and organic matter in the water has a serious impact on the operating cycle of the resin. The high price of the resin and the complex regeneration operation also limit its application.
Heating and evaporating the sewage—vapor compression and condensation can concentrate the harmful components in the cooling water, and make 95% of the sewage be recovered in the form of condensate and returned to the system as circulating water and boiler make-up water. But this method The energy consumption is too high, and it can only be used in areas where water is particularly scarce. The use of phosphate to control the release of water treatment agents can achieve constant-rate dosing. The use of automatic dosing devices and improved water treatment technology can help improve the water quality of circulating cooling water, increase the concentration ratio, and save water. In addition, petrochemical companies often use grease traps to remove oil that enters the cooling water system due to leakage. However, the side-stream removal process of orthophosphate and silica in cooling water has not been reported.