There are two forms of air cooling column in precooling system: closed cycle (the air cooling column is divided into upper and lower sections, and the chilled water circulates between the upper section of the air cooling column and the water cooling column) and open cycle (into the circulating water system). Closed cycle is mainly used in chemical units with poor water quality, and fresh water and chemicals need to be supplemented; The open cycle is widely used, but the circulating water system also needs to supplement fresh water regularly, and the precooling system also needs to consider the working condition in summer.
The bottom of air cooling column is generally designed to be 1m φ 76 stainless steel Bauer ring (high temperature resistant), 3M φ 76 reinforced polypropylene Bauer ring (high flux), 4m φ 50 reinforced polypropylene Bauer ring.
There are also two types of water cooling column: two-stage type (when there is no external cooling source, the cooling capacity of dry sewage nitrogen is fully recovered, so that the precooling system is guaranteed, but the resistance is twice as large, (7m + 7m) φ 50 polypropylene Bauer ring) and one-stage (with external cold source, 8m φ 50 polypropylene Bauer ring).
In addition, the pre-cooling system should be equipped with filters (generally 6 sets: 4 pumps, water into the water cooling column, water into the evaporation side of the water chiller) to prevent impurities from entering the system. The results show that the outlet gas of the lower 4m packing section is 1 ℃ lower than that of the inlet water; The outlet gas of the upper 8m packing section is 1 ℃ higher than that of water. Generally, a thermometer is set in the middle of the air cooling column.
