Abstract: The process and the apparatus serve for the low-temperature fractionation of air. Compressed and prepurified feed air (3, 5) is introduced into a rectification system for nitrogen-oxygen separation which has a pressure column (6). At least a part of the compressed and prepurified feed air is fed (5) to the pressure column (6). An oxygen-enriched fraction (13) is taken off from the pressure column (6) and passed (14) to a further working step (7) within the rectification system. The oxygen-enriched fraction (13) is taken off at least one theoretical or actual plate (15) above the point at which the compressed and prepurified feed air (5) is fed to the pressure column. From the bottom of the pressure column (6) a purge fraction (16) is removed in the. liquid state, fed in the liquid state to a purification stage (17), in which N2O is removed, and is taken off from the purification stage (17) as purified purge fraction (18).

Abstract: The invention relates to a method for extracting xenon and eventually also krypton from a liquid oxygen (LOX) charge, as it accrues in a cryogenic air separation system (LZA) during a rectification of the air, mostly as a bottom product of a low-pressure, column, namely with xenon (Xe), krypton (Kr) and hydrocarbons (CxHy) in a small concentration and approximately 99 mol % oxygen (O2). According to the inventive method, the LOX charge is fed to a first column, the oxygen of the LOX charge is extensively removed by stripping with an inert gas, and is extracted in the top gas, whereas the inert gas is withdrawn in the form of a liquid from the bottom of the first column with little O2 and nearly the total mass of CxHy, Kr, Xe. According to the invention, the liquid discharge is fed to a second column without prior catalytic and/or adsorptive removal of CxHy. A Kr fraction is extracted as top gas of the second column, and an Xe fraction is withdrawn from the bottom of the second column.

Abstract: The invention relates to a process and a liquefier for the production of liquid air with an oxygen content of between 16 and 21 mol % in a low-temperature process, whereby atmospheric air is used as a feed gas; in a warm part of the process, H2O, carbon dioxide and contaminants entrained in the air are removed in a purification step, e.g. adsorption; cold is produced by compression and engine expansion of process streams. Liquid air is obtained as a liquid head product in a cold part of the process by low-temperature rectification in a column having less than four theoretical plates. In addition, a liquid bottoms product is obtained in the rectification, used exergetically and vented as a warm residual gas into the atmosphere or used at least partially in the purification step.

Abstract: The process and the apparatus serve to produce pressurized nitrogen by low-temperature fractionation of air in a rectification system which has a pressure column (4) and a low-pressure column (5). Feed air (1, 3) is passed into the pressure column (4). An oxygen-containing liquid fraction (11) is taken off from the pressure column (4) and fed into the low-pressure column (5). Gaseous nitrogen (18) from the low-pressure column (5) is at least partially condensed in a top condenser (17) by indirect heat exchange with an evaporating liquid (13). Nitrogen from the low-pressure column is produced as gaseous pressurized nitrogen product (24, 25, 29) at a pressure which is higher than the operating pressure of the low-pressure column (5). Liquid nitrogen (20) withdrawn from the low-pressure column is brought (21) in the liquid state to a pressure which exceeds the pressure of the low-pressure column (5).

Abstract: In a process for the production of a pressurized gaseous product by low-temperature separation of air, which is at times done in a gas operation and at times in a combined operation, whereby in the gas operation and in the combined operation (a) purified charging air is cooled under pressure, partially liquefied, and subjected to rectification to produce gaseous and liquid fractions, (b) extremely cold liquid of at least one of the liquid fractions from the rectification is evaporated under elevated pressure by indirect heat exchange with feed air, heated, and obtained as a pressurized gaseous product, whereby in combined operation, (c) the cold that is required for this purpose is generated in an air-refrigeration cycle, by air being compressed in the refrigeration cycle and work expanded, in which case heat is removed from the air, and the actively depressurized air that is partially in countercurrent is heated again with the charging air that is to be cooled and then repressurized, (d) extremely cold liqui