Method for preparing liquid by low-temperature rectification

Abstract

The invention relates to a method for preparing liquid by low-temperature rectification. The method comprises the steps that 1, raw material air passes through an air compressor, an air pre-cooling system and an air purification system; 2, the purified air enters the heat exchanger continuously, and air in the heat exchanger is divided into two strands, the first strand of air passes through the heat exchanger to be condensed into liquid to enter a rectifying lower tower, the second strand of air is pumped out and then enters a low-temperature expansion machine for expansion, part of the air enters the rectifying lower tower, and the other part of the air is returned to the air compressor inlet or the air pre-cooling system after being subjected to repeated thermal expansion by the heat exchanger; 3, liquefied air after throttling which flows into the lower tower and the expanded part of air into the rectifying lower tower for rectification, so as to obtain a liquid nitrogen product;and rectifying is carried out again through a rectifying upper tower to obtain the liquid oxygen product. According to the method, the exhaust pressure of the circulating air compressor is effectivelyreduced, the unit refrigerating capacity of the expansion machine is improved, and the purposes of enabling the equipment to be easy to operate and reducing the primary investment of the equipment are achieved.

Description

technical field [0001] The invention relates to a method for producing liquid by low-temperature rectification. Background technique [0002] At present, the demand for liquid air separation products is still greater, but when the liquid volume is large and the variety requirements are large, the number of moving equipment involved in the air separation system and the working pressure will be relatively high. Conventional process for producing a large amount of liquid products: the raw gas air compressor is compressed and boosted to 0.62MPaA by three stages, and then enters the pre-cooling and purification system to remove impurities. Except part of the purified air is used as instrument air for the air separation unit, the rest All enter the circulating air compressor to pressurize. After the supercharged air is finally cooled, part of it is pumped into the high-pressure main exchanger for cooling, then goes to the high-temperature expander for expansion, reheats and retur...

AI Technical Summary

Problems solved by technology

On the one hand, this situation virtually increases the investment cost of the equipment and increases the floor area. Another important shortcoming is that the working pressure of the equipment is high and it is not easy to operate.

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