Patent DE-102009015766-A1 (DE)
Title: Liquefying hydrocarbon-rich nitrogen-containing fraction, comprises carrying out the cooling and liquefaction of the hydrocarbon-rich fraction in indirect heat exchange against refrigerant or refrigerant mixture of refrigeration circuit
Inventor: SCHMIDT HANS
IPC: F24V30/00
Filed: 2009-03-31
Abstract: The method comprises carrying out the cooling and liquefaction of the hydrocarbon-rich fraction (1) in indirect heat exchange against the refrigerant or refrigerant mixture of a refrigeration circuit (20, 21), temporarily storing the liquefied hydrocarbon-rich fraction, carrying out a nitrogen separation during the liquefaction of the hydrocarbon-rich fraction, compressing and re-liquefying the biol-off-gas fraction (8) occurring during the storage of the liquefied fraction, and carrying out the re-liquefaction of the biol-off-gas fraction against the refrigeration circuit. The method comprises carrying out the cooling and liquefaction of the hydrocarbon-rich fraction (1) in indirect heat exchange against the refrigerant or refrigerant mixture of a refrigeration circuit (20, 21), temporarily storing the liquefied hydrocarbon-rich fraction, carrying out a nitrogen separation during the liquefaction of the hydrocarbon-rich fraction, compressing and re-liquefying the biol-off-gas fraction (8) occurring during the storage of the liquefied fraction, and carrying out the re-liquefaction of the biol-off-gas fraction against the refrigeration circuit and then subjecting to the nitrogen separation, where the nitrogen fraction (4) obtained in the nitrogen separation has a methane residual content of less than 1 vol.%, which allows to deliver the nitrogen fraction to the environment air or to use as low calorific fuel gas. The nitrogen separation takes place in a separator and/or a rectification column (T). In the case of provision of several separators and/or rectification columns, the separators and/or rectification columns are arranged in a cascade manner and/or are operated at different pressures. The boil-off-gas fraction to be re-liquefied is added to the hydrocarbon-rich fraction to be liquefied before its feeding into the liquefaction process and/or during the liquefaction process but certainly before the feeding into the nitrogen separation. The boil-off-gas fraction to be re-liquefied is mutually compressed with the hydrocarbon-rich fraction to be liquefied. The hydrocarbon-rich fraction to be liquefied is subjected to a separation of heavy hydrocarbons, C 2+hydrocarbons and/or C 3+hydrocarbons. The nitrogen separation takes place in the rectification column. A partial stream of the hydrocarbon-rich fraction to be liquefied is fed to the rectification columns or one of the rectification columns as stripping gas stream into a sump of the rectification columns and/or a partial stream of the hydrocarbon-rich fraction to be liquefied is cooled in a reboiler of the rectification columns or one of the rectification columns and is fed as further feed stream to the rectification columns or one of the rectification columns. The nitrogen separation takes place in one of the rectification columns. The adjustment of the nitrogen content in the nitrogen fraction removed from the rectification column takes place using a condenser provided in the rectification column.