Air separation process description

The air separation equipment is a set of air separation equipment with a pressurized turbo expander, which is used for the adsorption purification of molecular sieves and the production of hydrogen-free argon gas at normal temperature in conventional packed towers. The process flow is as follows:

4.1 Filtration, compression, pre-cooling and purification

The original process air is sucked in from the suction port, enters the self-cleaning air filter, filters out dust and mechanical impurities, and enters the centrifugal air compressor for compression. The compressed gas enters the air cooling tower in the air pre-cooling system. Cool and wash inside. The air cooling tower uses circulating cooling water and low-temperature chilled water cooled by the water cooling tower, which is further cooled by the ice machine. The top of the air cooling tower is equipped with an inertial separator and a screen separator to prevent free water from being brought out of the process air.

The process air from the air pre-cooling system enters the air purification system for adsorption and removal of water, carbon dioxide, and hydrocarbons. The adsorber in the purification system consists of two vertical containers. The two adsorption containers adopt a double adsorption tower structure. The bottom part is activated alumina and the upper part is molecular sieve. When one of them is running, the other one is heated and regenerated by the dirty nitrogen from the cold box through the heater.

4.2 Air distillation

Most of the clean process air from the air purification system enters the main heat exchanger in the cold box and is cooled by the refluxed gas. The air close to the dew point enters the bottom of the lower tower for the first fractionation. In the distillation tower, the rising gas fully contacts the downstream liquid. After heat and mass transfer, the nitrogen concentration in the rising gas gradually increases. In the main condensing evaporator, nitrogen is condensed and liquid oxygen is vaporized. The liquid air and liquid nitrogen produced in the lower tower are subcooled by the cooler and throttled to the upper tower as reflux liquid from the upper tower. In the upper column, product nitrogen, product oxygen, liquid oxygen and dirty nitrogen are obtained after distillation again.

4.3 Cold production

Most of the cooling required by the equipment is provided by the turboexpander.

The remaining clean air from the air cleaning system enters a supercharger driven by a turboexpander to increase its pressure. It is then cooled by the cooler after the supercharger, enters the main heat exchanger in the cold box, where it is cooled to a certain temperature, and then enters the turboexpander. This expanded air is expanded and cooled in the expander, and then enters the upper tower to participate in distillation.

4.4 Argon purification

The latest full distillation argon production technology is used to extract argon. In order to produce argon, an argon fraction gas is drawn from an appropriate position in the upper and lower parts of the fractionating tower and sent to the crude argon column I for distillation to reduce the oxygen content; crude argon column I The reflux liquid is liquid crude argon drawn from the bottom of the crude argon column II by a liquid pump. The gas drawn from the top of crude argon column I enters crude argon column II, where deep argon and oxygen separation is carried out. After distillation in crude argon column II, crude argon gas with oxygen content ≤1PPm is obtained at the top of crude argon column II. A condensing evaporator is installed at the top of the crude argon tower II. The liquid air drawn out from the subcooler is throttled and sent into it as a cold source. Most of the crude argon gas is condensed by the condensing evaporator and used as the reflux liquid of the crude argon tower. The rest is drawn from the top of the crude argon tower (crude argon with oxygen content ≤1PPm) and sent to the refined argon tower. An evaporator is installed at the bottom of the refined argon tower. The medium-pressure nitrogen at the bottom of the tower is used as a heat source to evaporate liquid argon. At the same time, the nitrogen is evaporated. liquefaction. A condenser is installed at the top of the purified argon tower. The liquid nitrogen of the purified argon evaporator is used as a cold source to condense most of the rising gas into the reflux of the purified argon tower. After distillation in the purified argon tower, the product is obtained at the bottom of the purified argon tower. The 99.999% Ar refined argon liquid is drawn out of the cold box as the product liquid argon.

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4.6 Equipment design and technical characteristics.

4.6.1 Adopt full low-pressure process molecular sieve adsorption, supercharged turbo expander refrigeration, fully distilled argon, and oxygen external compression process. Advanced technology, mature technology, reliable operation, easy operation, safety and low consumption.

4.6.2 The pre-cooling system uses nitrogen and dirty nitrogen to enter the water cooling tower to reduce the temperature of the cooling water. The air cooling tower structure adopts reliable anti-liquid immersion measures.

4.6.3 The channel of the main condensing evaporator adopts a special structure to prevent acetylene from accumulating in liquid oxygen and ensure the safety of the main condensing evaporator and the system.

4.6.4 The upper tower, crude argon tower and refined argon tower all adopt conventional packed towers.

4.6.5 The equipment has the ability to operate under variable working conditions and the equipment has variable load. The equipment's variable load capacity ranges from 75% to 105%.

4.6.6 Adopt DCS centralized control system.