Requirements and suggestions on cooling water source of nitrogen generator

At present, most of the large equipments which need cooling water use rivers, lakes or underground water as cooling water. This kind of water usually contains suspended solids (sediment and other dirt) and calcium, magnesium and other heavy carbonate [-Ca (HCO₃) 2 and Mg (HCO₃) 2], called hard water. When there are many suspended substances, it is easy to block the passage, filter screen, Valve and so on of the cooler. Calcium carbonate, magnesium and other heavy carbonate are easy to generate calcium carbonate (CaCO₃), Magnesium carbonate (MgCO₃) Sediment, that is to form the commonly called scale. Generally, when the water temperature is above 45℃, scale will begin to form, and the higher the water temperature is, the easier it is to scale. The scale attaches to the tube wall of the cooler, the stuffing of nitrogen-water precooler, nozzle or sieve hole, which not only affects the heat transfer and reduces the cooling effect, but also hinders the circulation of cooling water or air, in severe cases, equipment failure will be caused, for example, nitrogen water precooler with water will freeze the cooler (or switching heat exchanger. Scale hard, attached to the wall is not easy to clear. Therefore, cooling water is better to be softened. It is relatively simple and effective to use the magnetic device for softening treatment. Sedimentation tank should be set for removing suspended solids. If the cooling water is recycled, it is beneficial to the softening of water quality, but it covers a larger area and has a larger infrastructure investment. The cooling water of the air separation plant is generally required to be not higher than 28℃, and the drainage temperature is less than 40℃.

Requirements for water quality:
1. Temporary hardness is not more than 17 °dh
2. Chloride ion (C1-) (mass fraction) is less than 50 × 10^-6
3. The oil content is less than 5 mg/L
4. Ph value 6.5 ~ 8.0
5. The suspended matter content is not more than 50 mg/L
6. Sulfate radical (SO₄-2) (mass score) less than 50 x^10-6

Suggestions:
Nitrogen gas precooling system water supply and drainage is independent circulation system. Because the temperature of cooling water in the Tower is high, the drainage temperature is high, and the scale is serious, it is required that the supplement water of this system should use low hardness water or soft water as much as possible, and its temporary hardness should generally be no more than 8.5 °dh.