Circulating water treatment under high pH conditions

Adopting a naturally balanced pH value for circulating water treatment, although it reduces corrosion, controls scaling, and avoids accidents that may occur due to acid addition operations, its pH value can still only be controlled within the weakly alkaline range, and water treatment agents are needed to solve the problems of corrosion and scaling, which does not completely solve the problem of phosphorus discharge. Moreover, under such pH conditions, it is the optimal environment for microbial growth, while alkaline conditions also significantly reduce the killing effect of chlorine based biocides. So there is still room for further development of water treatment technology.

We found from the principle of boiler water treatment that further increasing the pH value of circulating water operation (adjusting with alkali), as shown in the figure below, when the pH value of water quality is increased to 10-12, the corrosion rate of carbon steel is the smallest, and the hardness components in the water are not easy to form scale on the surface of the equipment. Therefore, exploring the use of high pH methods to treat circulating water can not only meet the requirements of industrial production for water treatment efficiency, but also avoid the use of corrosion inhibitors, scale inhibitors, and fungicides containing carbon, nitrogen, and phosphorus, without polluting the environment.

Boilers are heat exchange equipment that generate steam and hot water, and the boiler system can also cause corrosion, scaling, and other problems during operation. In order to prevent corrosion of metal materials by boiler feed water, it is usually necessary to adjust the pH value of the feed water, and generally control it within a higher pH range. A protective film of Fe304 is formed on the surface of carbon steel within a high pH range to prevent its corrosion at high temperatures.

At the same time, under high pH conditions, the calcium carbonate deposition ions in the boiler cannot be arranged in a regular lattice order to generate hard scale that adheres to the heating surface. Instead, suspended water slag is generated in the boiler, which can be prevented from scaling through boiler discharge. At this point, the concentration of calcium ions in the boiler water decreases, which is beneficial for preventing the formation of calcium sulfate and calcium silicate.

In addition, studies have shown that microorganisms are difficult to survive in environments with pH values of 10-12. High pH values have a significant effect on heterotrophic bacteria

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