Cost of large air separation plant

During the start-up phase, when the liquid volume accumulates in the condensing evaporator, the gas and liquid mixture will pass through the liquid air and liquid nitrogen throttle valves. When the throttle valve begins to close, due to the large opening of the valve, when the amount of gas and liquid mixture from the lower column to the upper column changes little, and the pressure of the lower column does not increase significantly, it means that the temperature difference of the condensing evaporator has not increased. At this time, the condensing evaporator and the surrounding insulation have been cooled to the low temperature required by the liquid accumulation stage. Due to a large amount of cold production and a large amount of gas liquefaction, the liquid evaporation in the condensing evaporator is also increased. The rising steam produced prevents the flow of liquid from the sieve plate hole, and gradually accumulates liquid on the tray, so the liquid level will drop. In ad

In the distillation column of air separation, the air is usually pre separated in the lower column, and then distilled into oxygen rich liquid air and pure nitrogen, and then further distillation in the upper column to obtain oxygen and nitrogen products. As a condensing evaporator connecting the upper and lower columns, the pressure nitrogen of the lower column is used to heat the liquid oxygen of the upper column. When the liquid oxygen is evaporated, the gas nitrogen is condensed. The two-stage distillation column can make oxygen and nitrogen products obtain higher extraction rate and higher purity. The working principle of single-stage distillation column is similar to that of the lower column of two-stage distillation column. Oxygen enriched liquid air is at the bottom of the column, and pure nitrogen gas can be obtained at the top of the column. The single-stage distillation column can't separate the air perfectly, so it is seldom used in practice. However, because of its simple