PROCESS AND APPARATUS FOR SEPARATION OF HYDROCARBONS AND NITROGEN

摘要

The invention provides a process and apparatus for the separation of nitrogen from a gaseous feed comprising a mixture of hydrocarbons and nitrogen gas, the process comprising the steps of: (i) cooling (02) and at least partially condensing the gaseous feed (01); (ii) feeding the cooled and at least partially condensed feed from step (i) to a first fractionation (08) to produce an overhead vapour stream (19) having an enriched nitrogen content and a condensed product (09) having a reduced nitrogen content which is subjected to a second fractionation (15), which comprises reboil (04), at a lower pressure than the first fractionation; (iii) partially condensing (04) the overhead vapour stream, and separating (21)to provide a liquid stream (22), which is used to provide reflux to the first fractionation, and a separated vapour stream (23), which is condensed (10) to provide reflux (27) to the second fractionation; and (iv) sub-cooling (10) the condensed product of the first fractionation and dividing the resulting sub-cooled product into at least two streams: a first stream (14) being expanded (13) and fed to the second fractionation, and a second stream (17) being expanded (16) and reheated in heat exchange (10) with the separated vapour stream (23) from step (ii) before being fed to the second fractionation; (v) removing a hydrocarbon product stream (31) low in nitrogen from the second fractionation; and (vi) removing a nitrogen rich stream (28) from the second fractionation.