Air cooling column is a mixed heat exchange device. The function is to make the cooling water fully contact with the air and being mixed fully to increase the heat transfer area and enhance the heat transfer, usually using "packed column" or "sieve plate".
The packed column is a round steel container with packing (ceramic ring, plastic ring, etc.). Cooling water is ejected from the top of the column and mixed with air flowing upward from the bottom for heat and mass exchange. Air transfers heat to the cooling water, lowering its temperature and raising its temperature. In order to prevent the generation of water droplets in the air, the raschig ring (or stainless steel wire mesh) packing separator (also known as trapping layer) and mechanical water separator (inertial separation) are usually installed on the upper part of the column. The cooling water ejected from the spray device flows downward to the packing layer through the distributor, and an overflow ring is provided to redistribute water in the packing layer at regular intervals, so as to avoid direct downward flow of water to the vessel wall and affect the heat transfer effect of the container. The cooling water with increased temperature is drawn from the bottom and sent to the water cooling column or discharged. The cooled air is discharged from the top of the column and then sent to the air separation column or molecular sieve adsorber. The disadvantage of packed column is that the packing is easy to be blocked by scale, and the packing forms a large block, which is difficult to clean and replace.
The sieve plate column is similar to the sieve plate column of distillation column, but the number of trays is small (usually about 5), and the diameter and distance between holes are large (aperture is about 5 mm, hole spacing is about 9 mm). The cooling water is ejected from the top through the spray device and flows down to the tray layer by layer through the screen holes. The air flows downward from the bottom of the column and bubbles upward through the screen holes. The gas-liquid two phase movement on the sieve plate forms a foam layer, which increases the gas-liquid contact area and disturbance degree, and makes the gas and liquid energy conduct good heat and mass transfer, and the effect is better than that of packed column.
