For air separation cooling water, we generally use hard water. This kind of water contains many impurities and is easy to block the cooler channel, filter screen and valve. Calcium, magnesium and other bicarbonates are easy to form calcium carbonate (CaCO3) and magnesium carbonate (MgCO3) precipitates when the water temperature rises, that is, scale formation.
The scale reduces the cooling effect, and it is easier to scale when the water temperature is high. Generally, the water temperature above 45 ℃ begins to form scale, which is attached to the tube wall of cooler, packing, nozzle or sieve of nitrogen water precooler, not only affects the heat exchange, but also hinders the circulation of cooling water or air. In serious cases, it will cause equipment failure, such as water in nitrogen water precooler, freezing the accumulator (or switching heat exchanger). The scale is hard and hard to remove. It is simple and effective to soften water with magnetic water separator, and the effect of air separation cooling water is acceptable.
There are different requirements for the water quality of cooling and water shortage in other air separation units. First, the temperature of compressor cooling water is generally required not to be higher than 28 ℃, and the drainage temperature is less than 40 ℃; second, the water supply and drainage of nitrogen water precooling system is an independent circulation system, because the temperature rise of cooling water in the column is large, the drainage temperature is high, and the scaling is serious, so the make-up water of the system is required to use low hardness water or soft water as far as possible The other requirements are the same as the cooling water of the compressor; third, the lubricating water of the cylinder of the high pressure oxygen compressor for bottle filling should be distilled water or soft water.
