METHOD AND APPARATUS FOR REMOVING NITROGEN FROM A CRYOGENIC HYDROCARBON COMPOSITION

摘要

Nitrogen is removed from a cryogenic hydrocarbon composition. A least a first portion of the cryogenic hydrocarbon composition is fed to a nitrogen stripper column. The nitrogen stripper column operates at a stripping pressure. A stripping vapour is passed into the nitrogen stripper column, comprising at least a stripping portion of a compressed process vapour that has been produced from the nitrogen-stripped liquid which has been depressurized after drawing it from the nitrogen stripper column. Reflux is generated involving partially condensing overhead vapour of the nitrogen stripper column by passing heat from the overhead vapour to an auxiliary refrigerant stream at a cooling duty. An off gas consisting of a, non-condensed, vapour fraction from the overhead vapour is discharged. The cooling duty is adjusted to regulate a heating value of the vapour fraction being discharged.

主权项

1. Method of removing nitrogen from a cryogenic hydrocarbon composition, the method comprising:
providing a cryogenic hydrocarbon composition comprising a nitrogen- and methane-containing liquid phase; feeding a first nitrogen stripper feed stream, at a stripping pressure, into a nitrogen stripper column comprising at least one internal rectifying section and at least one internal stripping section positioned within the nitrogen stripper column gravitationally lower than said rectifying section, said first nitrogen stripper feed stream comprising a first portion of the cryogenic hydrocarbon composition; drawing a nitrogen-stripped liquid from a sump space of the nitrogen stripper column below the stripping section; producing at least a liquid hydrocarbon product stream and a process vapor from the nitrogen-stripped liquid, comprising at least a step of depressurizing the nitrogen-stripped liquid to a flash pressure; compressing said process vapor to at least the stripping pressure, thereby obtaining a compressed vapor; passing a stripping vapor stream into the nitrogen stripper column at a level gravitationally below said stripping section, said stripping vapor stream comprising at least a stripping portion of said compressed vapor; forming a partially condensed intermediate stream from an overhead vapor obtained from an overhead part of the nitrogen stripping column above the rectifying section, said partially condensed intermediate stream comprising a condensed fraction and a vapor fraction, said forming comprising partially condensing the overhead vapor by heat exchanging the overhead vapor against an auxiliary refrigerant stream and thereby passing heat from the overhead vapor to the auxiliary refrigerant stream at a cooling duty; separating the condensed fraction from the vapor fraction, at a separation pressure; discharging the vapor fraction as off gas, said vapor fraction having a heating value; passing at least a fuel portion of the vapor fraction to a combustion device; allowing at least a reflux portion of the condensed fraction into the nitrogen stripper column starting at a level above said rectifying section; adjusting the cooling duty to regulate the heating value of the vapor fraction being discharged to match with an actual demand of heating power by the combustion device.