Energy saving and emission reduction of cryogenic air separation equipment

The air separation cold box is filled with insulation material, generally pearlite, and the pearlite particles are filled with air. After the operation of the air separation unit, the temperature of the insulation material and the air will decrease, and the volume will decrease. At this time, if the cold box is well sealed, negative pressure will be formed in the cold box, and the cold box may be compressed under the effect of internal and external pressure difference. If the cold box is not well sealed, the moisture outside the cold box will enter the cold box, making the insulation material damp, and the cold loss of the unit will be greatly increased. In order to prevent the cold box from being compressed and the thermal insulation material from becoming damp, dry nitrogen or crude nitrogen is usually filled into the cold box after the unit is running to keep the cold box at slightly positive pressure.

In the upper column fractionation, below the liquid air inlet is called the stripping section, and above the liquid air inlet is called the distillation section. The stripping section realizes the separation of oxygen and argon, and the distillation section realizes the separation of oxygen and nitrogen. Because the boiling points of oxygen and argon are relatively close, the separation is difficult. In order to ensure the purity of oxygen, the separation of oxygen in the distillation section is not clean, and argon escapes with oxygen and nitrogen. If high purity nitrogen is to be obtained, argon will condense with oxygen in the distillation section, which will affect the purity of oxygen. In order to ensure the purity of oxygen and obtain high purity nitrogen, it is necessary to extract part of the gas with high argon concentration in the distillation section.