In the air separation unit, the water cooling column is a hybrid heat exchange equipment which uses the crude nitrogen to reduce the temperature of the cooling water from the air cooling column after cooling air, so as to provide the air cooling column with recycling. In the water cooling column, the crude nitrogen from the reversible heat exchanger (or accumulator) is 27-28 ℃ and the relative humidity is about 30%, while the temperature of the cooling water from the air cooling column is 35-45 ℃. When the crude nitrogen meets the hot water sprayed, it absorbs heat, thus reducing the water temperature. Generally, the structure of water cooling column is packed column, cyclone plate column and sieve plate column.
1.Packed column: at present, the Alpha Pall ringswith large flow capacity, small resistance, good heat transfer effect and high strength is generally selected as the packing of water cooling columnin China, which can ensure that the heat transfer temperature difference at the hot end is about 0.5 ℃, and the negative temperature difference of outlet water can reach 4-9 ℃.
2.The hydrocyclone plate type of water cooling columnis composed of several metal structure swirl columnplates, which has the characteristics of small resistance and not easy to be damaged, but the heat transfer effect is inferior to that of packed water cooling column.
3.The sieve plate type water cooling columnadopts the spray columnplate with larger pore diameter and hole spacing. Nitrogen and water pass through the sieve hole and exchange heat. Because the work of the water cooling column is not continuous and stable, the cooling effect of the sieve plate type water cooling column is not as good as that of the packing type water cooling column.
The best heat transfer effect and cooling effect should be ensured when choosing the type of water cooling column. At the same time, the flow resistance should be reduced to prevent limescale.