Methods for controlling scale and dirt in Circulating cooling water system

Methods for controlling scale

1) Ion exchange resin method

Let the water go through the ion exchange resin to displace the calcium ions and magnesium ions from the water and bind them to the resin to achieve the purpose of removing calcium ions and magnesium ions from the water.

2) Lime softening method

Before the make-up water enters the circulating cooling water system, proper lime shall be added during pretreatment to allow the calcium bicarbonate in the water to react with the lime in the clarification tank to form calcium carbonate precipitation, thereby removing calcium ions in the water.

3) Adding acid

Sulfuric acid is usually added, because adding hydrochloric acid will bring in chloride ions and increase the corrosiveness of the water; adding nitric acid will bring in nitrate, which is conducive to the reproduction of nitrifying bacteria.

4) Inject the CO2 gas

Inject the carbon dioxide gas or flue gas into the water to disrupt the precipitation balance and move it to the left, thereby stabilizing the bicarbonate.

Methods for controlling dirt

1) Reduce the turbidity of supplementary water

Natural water bodies constitute the turbidity of water bodies because of sediment, corrosive organisms, various suspended solids and colloids, etc. As for circulating water, the lower the turbidity, the better, indicating that the circulating water has less impurities. When the quality of circulating cooling water is not good, pretreatment must be performed. The concentration of suspended solids in circulating water treatment should not be greater than 20mg/L, and when the form of the heat exchanger is plate type or finned tube type and spiral plate type, it should not be greater than 10 mg/L.

2) Process the water quality treatment of circulating cooling water well

Circulating cooling water is mainly to prevent scale and corrosion. When the influent water quality is not good, it will inevitably lead to the production of scale and corrosion. At the same time, there will be a large number of bacteria breeding, thereby forming fouling. Therefore, the water quality treatment is a way to reduce the fouling of the system.

3) Add side filter treatment

Even the water quality treatment is done very well, the turbidity of the influent water is well controlled, but the turbidity of the circulating water will still continue to rise, thereby increasing the formation of dirt.

The reason why the turbidity of the circulating cooling water system will increase under stable operation is that when the cooling water go through the cooling tower and comes into contact with the air, dust in the air will be carried into the water, resulting the increase in turbidity. Adding bypass filter treatment can reduce dust entering the circulating water. As long as the bypass flow and the turbidity of the inlet and outlet bypass treatment are controlled, it can be ensured that the turbidity of the system will not increase under long-term operation, and will remain within the controlled index, thereby reducing the generation of dirt.

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