Air separation unit maintenance work

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 redist

The amount of liquid nitrogen removed from the lower column of the air separation unit will affect the purity of the liquid nitrogen in the lower column and the oxygen enriched liquid air at the bottom of the column. When the liquid nitrogen removal amount of the lower column increases, the reflux liquid participating in the heat and mass exchange of the lower column will be reduced, the temperature rise of the rising steam on the column plate will be correspondingly reduced, the condensation of the rising steam will not be sufficient, the oxygen component will be condensed less, the purity of nitrogen at the column top will be reduced, and the purity of liquid nitrogen will be naturally reduced. At the same time, the temperature rise of the downflow liquid will increase, the liquid evaporation will be more sufficient, more nitrogen components will be evaporated to the top of the column, and the purity of the liquid air at the bottom of the column will be improved accordingly.