Technical assistance: Circulating water in fine chemical plants
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This post was last edited by cdpulin on 2011-1-18 at 21:05. The main condenser in our factory’s workshop was removed just 20 days ago, and now its heat exchange capacity is once again insufficient. When it was taken apart today, it was found that there were many milky-white solids on the walls of the circulation water pipes, and the inner walls of the heat exchanger were completely blocked. What could be the cause of this? Is there any way to solve it?
The original poster had better find the source and test the quality of the circulating water; it seems that a treatment device needs to be installed at the inlet side
1) Check if any materials have entered the circulating water； 2) Check the quality of the water from which the circulating water is obtained, and whether the levels of calcium and magnesium are high ； 3) The system is equipped with a filtering bypass to eliminate the impact of suspended solids ； 4) Select an appropriate scale inhibitor ； 5) Is the return water temperature of the main condenser too high?
It doesn’t seem to be calcium and magnesium precipitates; it’s likely the material itself
Has the material entered the circulating water system? This has not happened here; we could consider installing filtering measures
If it’s not a material leak, LZ, the make-up water you’re using might be groundwater; no scale inhibitor was used, or the scale inhibitor used is ineffective or inappropriate. Circulating water must be treated with scale inhibitors and other water treatment agents, such as algaecides. At the same time, the make-up water needs to be properly treated; if its hardness and alkalinity are too high, the concentration ratio should not be too high. If water conservation is indeed necessary, acids can be used to control the alkalinity. Moreover, the scale and corrosion inhibitors chosen must be appropriate, otherwise the problems mentioned by LZ will occur.
If it’s not a problem with the materials, then it indicates that the water quality is very poor; generally, scale inhibitors cannot solve this issue. I recommend using ultrasonic descaling to remove the hardened scale deposits at any time. Additionally, an overestimated circulating water temperature is also a significant cause, or the designed flow rate of the circulating water is too low. Secondly, it is the insufficient cooling capacity of the circulating water cooling tower, which leads to high water temperatures and an accelerated rate of scaling.
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The poster might want to lower the pH value of the circulating water; keeping it at 7 should be sufficient
Could you be more specific? Were there any tests conducted on the quality of the circulating water? Are there any data available? Please provide those data.
It’s probably not calcium and magnesium scale; after more than 20 days of operation, it’s impossible for scaling to become this severe even without the use of chemicals. You can remove the white solid and heat it; the weight loss at 550 degrees indicates the content of organic substances, while the weight loss at 550–950 degrees indicates the content of carbon dioxide (i.e., carbonate scale). If the substance does not dissolve in acid, it indicates the presence of silica scale and calcium sulfate scale