1、 To achieve phase change separation of oxygen and nitrogen, the condensation evaporator utilizes the difference in boiling points of oxygen and nitrogen to complete the phase change process through heat exchange. The high-pressure gas nitrogen (containing a small amount of impurities such as argon) at the top of the lower tower enters the high-temperature side channel of the condensation evaporator, releases the latent heat of condensation, and condenses into liquid nitrogen. The reflux liquid oxygen (containing trace amounts of argon) at the bottom of the upper tower enters the low-temperature side channel, absorbs the heat released by gas nitrogen, and evaporates into gas oxygen. The heat absorption of liquid oxygen evaporation is equal to the heat release of gas nitrogen condensation, and the heat exchange efficiency directly affects the production of oxygen and nitrogen.
2、 Maintaining the gas-liquid equilibrium of the distillation system, the gas oxygen generated by the evaporation of liquid oxygen in the upper tower provides necessary upward vapor for the upper tower distillation, promoting full contact between the gas-liquid phases in the tray or packing layer, and achieving stepwise separation of oxygen and nitrogen. Part of the liquid nitrogen is directly returned to the lower tower as reflux liquid for distillation, improving the purity of nitrogen products. The other part of liquid nitrogen is depressurized to near the upper tower pressure through a throttle valve and sent to the top of the upper tower as reflux liquid to participate in the upper tower distillation and further purify the oxygen product.
3、 Optimize system energy efficiency and product purity, achieve efficient countercurrent heat transfer between gas nitrogen and liquid oxygen through plate fin or tube shell structures, and reduce cooling loss. Part of the design uses a condensing evaporator to supercool liquid nitrogen, reducing flash losses after throttling expansion and increasing liquid nitrogen production.
