A device and method for cryogenic separation and purification of nitrogen and liquid nitrogen

Abstract

The invention relates to a device and a method for cryogenic separation and purification of nitrogen and liquid ammonia. According to the method, the air as a raw material sequentially passes through an air compression system for compression, a pre-cooling system for cooling, and a purification system for impurity removal, followed by entering a fractionating tower; the air entering the fractionating tower is divided into two parts, wherein one part of the air enters a pressure boost end for boosting pressure, is subjected to heat exchange through a cooler, and enters a main heat exchanger, the air is pumped by the lower portion of the main heat exchanger to enter an expansion end for heat insulation expansion, and the expanded air is recuperated by the main heat exchanger and discharged out of a cooling box; the other part of the air directly enters the main heat exchanger to be cooled to a liquefaction point and then enters a single-stage rectifying tower for rectification. A nitrogen product is pumped from the top of the single-stage rectifying tower, is recuperated to a normal temperature by the main heat exchanger, and enters a nitrogen collection unit through a valve, a liquid ammonia product is pumped from a main cooled liquid nitrogen side, the liquid ammonia product and a small part of returned liquid ammonia are subjected to heat exchange and supercooling through a liquid ammonia supercooler, and subsequently, the liquid ammonia product enters a liquid ammonia collection unit through a valve. According to the device and the method for cryogenic separation and purification of the nitrogen and the liquid ammonia, the process flow is simple in operation, high in extraction rate, low in energy consumption, and meanwhile, device investment costs are low.

Description

technical field [0001] The invention relates to the field of air separation, in particular to a device and method for cryogenically separating and purifying nitrogen and liquid nitrogen. Background technique [0002] With the rapid development of industry, nitrogen has been widely used in chemical industry, electronics, metallurgy, food, machinery and other fields. Nitrogen is a chemically inert gas that does not react easily with other substances. Therefore, nitrogen is widely used as protective gas and sealing gas in metallurgical industry, food refrigeration, electronic industry and chemical industry. Generally, the purity requirement of protective gas is 99.99%, and some require pure nitrogen above 99.998%. [0003] As the demand for nitrogen products increases, the scale of pure nitrogen equipment is also increasing. The process form of pure nitrogen equipment has also been changing and introducing new ones. [0004] At present, the processes adopted by pure nitrogen...

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Problems solved by technology

The above process forms are suitable for small-scale nitrogen-generating equipment. With the expansion of the scale of nitrogen-generating equipment, the disadvantages of the above-mentioned process forms are high energy consumption, complicated operation, and not easy for users to operate.

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