The Boc Group, Inc.

Stephen Roger Clare

John Douglas Oakey

Paul Higginbotham

David Mark Stuart

Martin Imre Mayer

Robert Hartley

Nitrogen is rejected from a pressurized feed gas stream comprising methane and nitrogen by cooling the feed gas stream in a main heat exchanger and rectifying the cooled feed gas stream in a double rectification column comprising a higher pressure rectification column, a lower pressure rectification column, and a condenser-reboiler placing the higher pressure column in heat exchange relationship with the lower pressure column. A pump withdraws a methane product stream from the column. The methane product stream is pressurized by the pump and is vaporized in the main heat exchanger. The pressurized feed gas stream is expanded with the performance of external work in an expansion turbineupstream of the main heat exchanger.

Nitrogen rejection method and apparatus

Nitrogen is rejected from a pressurised feed gas stream comprising methane and nitrogen by cooling the feed gas stream in a main heat exchangerand rectifying the cooled feed gas stream in a double rectification columncomprising a higher pressure rectification columna lower pressure rectification column, and a condenser-reboilerplacing the higher pressure columnin heat exchange relationship with the lower pressure columnA pumpwithdraws a methane product stream from the columnThe methane product stream is pressurised by the pumpand is vaporised in the main heat exchangerThe pressurised feed gas stream is expanded with the performance of external work in an expansion turbineupstream of the main heat exchanger

A method of supplying both an oxygen steelmaking process and an ironmaking process with oxygen. The oxygen is separated from air by rectification of the air. A first stream of oxygen from the rectification to the steelmaking process. A second stream of oxygen is also supplied from the rectification to the ironmaking process. The first and second streams of oxygen are both withdrawn from essentially the same stage of the rectification and both contain from about 97 to about 98% by volume of oxygen and less than about 100 parts per million of nitrogen.

Steelmaking method with oxygen from rectification of air

Air is raised in pressure by a compressor and pre-purified by removal of impurities, particularly H.sub.2 O vapor and CO.sub.2, in an adsorption unit. The resulting air is cooled in a heat exchanger, and is subjected to a first rectification in a rectification column in which the air is separated into a nitrogen-rich fraction and an oxygen-rich fraction. A further oxygen fraction enriched in argon is subjected to a second rectification in which argon is separated from oxygen in a second rectification column. First and second argon products of different purity are withdrawn from the second rectification column through outlets thereof.

Air separation

Air is compressed in compressors, cooled in a main heat exchanger, and separated into oxygen and nitrogen products in a double rectification column comprising a higher pressure rectification column and a lower pressure rectification column. A liquid oxygen product is withdrawn from the lower pressure column via a conduit. A liquid nitrogen product is also formed. An argon-enriched oxygen vapour stream is withdrawn from the lower pressure column through an outlet and has argon separated from it in an argon column. In order to help meet the requirements of the higher pressure column for reflux, a nitrogen vapour stream is withdrawn from the top of the lower pressure column, is warmed by passage through the heat exchanger, is recompressed in a compressor, and is liquefied by passage back through the heat exchanger from its warm end to its cold end and passage through a valve. A high liquid make and a high argon recovery can both be achieved.

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Bognor Regis, United Kingdom

Stephen Roger Clare