A method and apparatus for separating air in which production of the liquid products can be selectively varied between high and low production rates by varying the pressure ratio across a turboexpander used in imparting refrigeration with the use of a branched flow path. The branched flow path has a system of valves to selectively and gradually introduce a compressed refrigerant air stream into either a booster compressor branch having a booster compressor to increase the pressure ratio during high modes of liquid production or a bypass branch that bypasses the booster compressor to decrease the pressure ratio during low modes of liquid production. A recycle branch is connected to the booster compressor branch to allow compressed air to be independently recycled from the outlet to the inlet of the booster compressor during turndown from the high to the low liquid mode of liquid production to prevent surge.

An ultra-high-purity oxygen production method and apparatus are provide, in which the method can include a step in which feed oxygen comprising low-boiling-point components as impurities is introduced from a warm end of a main heat exchanger and cooled, then introduced into an oxygen rectification column, and product ultra-high-purity oxygen from which the low-boiling-point components have been removed is drawn as a gas or a liquid from a lower portion of the oxygen rectification column.

Process for producing gaseous oxygen by cryogenic distillation of air, wherein a portion of the feed air flow is brought to a pressure P.sub.1, by means of a first compressor, the suction temperature T.sub.0 of which is between 0 and 50 C., the gas at the pressure P.sub.1 is cooled, in order to generate an air stream at the pressure P.sub.1 and the temperature T1 between 5 and 45 C., a portion of the air compressed in the first compressor undergoes an additional compression step starting from the temperature T.sub.1 and pressure P.sub.1 to a pressure P.sub.2 greater than P.sub.1, then is cooled, to the temperature T.sub.2 where T.sub.2 and T.sub.1 differ by less than 10 C.

A system and method for supplying a backup product in an air separation device, as well as a system and method for supplying a lower-pressure product to a user by means of pressurization of a cryogenic liquid pump during normal operation of an air separation device, i.e., when the cryogenic liquid pump is in the cold standby state. By means of the system and method, a cryogenic liquid product taken from a storage tank is pressurized by the cryogenic liquid pump to produce a lower-pressure product by taking full advantage of the low-speed operation of the cryogenic liquid pump in the cold standby state, and the lower-pressure product is transmitted to product supply lines of a user, to achieve the function of supplying the lower-pressure product to the user. The system and method not only reduce the energy loss of the cryogenic liquid pump in the cold standby state for a long time, but also avoid the bleeding rate of the cryogenic liquid product generated by sending a part of the cryogenic liquid product back to the storage tank, so that the advantage of quickly starting the cryogenic liquid pump from the cold standby state is ensured, and the requirements of the user to the higher-pressure product and the lower-pressure product can be satisfied.

An air separation unit comprises a first rectification column, having a top condenser and a second rectification column placed side by side, a heat exchanger, a first pump and a second pump connected in parallel, the first pump being capable of producing liquid at a first liquid pressure and the second pump being capable of producing liquid at a second liquid pressure, higher than the first pressure, each pump having an inlet connected to the second column, a first outlet of the first pump being connected to a first outlet conduit, a second outlet of the second pump being connected to a second outlet conduit, the first and second outlet conduits being connected to the condenser section

A method of obtaining a liquefied hydrocarbon-rich fraction (product fraction) having a nitrogen content of 1 mol %, wherein the hydrocarbon-rich fraction is liquefied and subcooled with a refrigeration circuit and then subjected to a rectificative removal of nitrogen is disclosed.

An apparatus for separation of air by cryogenic distillation comprising: a system of columns; a first turbine; a warm compressor coupled to the first turbine; a second turbine; a cold compressor coupled to the second turbine; a heat exchanger; means for sending air cooled in the heat exchanger at an intermediate temperature of the heat exchanger to the cold compressor; means for sending expanded air from the second turbine to the system of columns; means for sending air compressed in the cold compressor to an intermediate point of the heat exchanger and then at least in part to the system of columns via a first valve; means for sending air compressed in the cold compressor to the inlet of the first turbine via a second valve without passing through the heat exchanger, wherein the means for sending air compressed in the cold compressor to the inlet of the first turbine via the second valve without passing through the heat exchanger is also connected to the inlet of the first turbine; means for sending a fraction of air cooled in the heat exchanger to an intermediate temperature of the latter to the first turbine; means for sending expanded air from the first turbine to the system of columns; and a bypass line provided with an expansion valve configured to send air from the cold compressor to the system of columns without passing through the heat exchanger.

A cooling arrangement for an at least two-stage compressed air generator comprises an intercooler arranged between a first and a second compressor stage, an aftercooler arranged after the second compressor stage, and a subassembly cooler, which absorbs heat from further subassemblies of the compressed air generator. A coolant circuit comprises a main cooler, the cold side supplying a cooled coolant parallel to the respective coolant inlet of the intercooler, of the aftercooler and of the subassembly cooler, and the hot side receiving the heated coolant exiting in parallel at the respective coolant outlet of the intercooler and of the aftercooler. The coolant outlet of the subassembly cooler is connected to a feed inlet of the intercooler and/or of the aftercooler.

A system and method for separating air in an air separation plant is provided. The disclosed systems and methods divert a portion of the compressed, purified air stream to a bypass system configured to selectively produce a higher pressure compressed output stream or a lower pressure compressed output stream. The higher pressure and/or lower pressure compressed output streams are cooled in a main heat exchanger by indirect heat transfer with a plurality of product streams from the air separation plant and then rectified in the distillation column system. A second portion of the compressed, purified air stream is partially cooled in the main heat exchanger and expanding in a turbo-expander to produce power and an exhaust stream which is directed to the distillation column system of the air separation plant where it imparts additional refrigeration generated by the expansion of the compressed air stream in the turbo-expander.

A cooling arrangement for an at least two-stage compressed air generator comprises an intercooler arranged between a first and a second compressor stage, an aftercooler arranged after the second compressor stage, and a subassembly cooler, which absorbs heat from further subassemblies of the compressed air generator. A coolant circuit comprises a main cooler, the cold side supplying a cooled coolant parallel to the respective coolant inlet of the intercooler, of the aftercooler and of the subassembly cooler, and the hot side receiving the heated coolant exiting in parallel at the respective coolant outlet of the intercooler and of the aftercooler. The coolant outlet of the subassembly cooler is connected to a feed inlet of the intercooler and/or of the aftercooler.