Purification of Carbon Dioxide
First Claim
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1. A process for purifying crude carbon dioxide comprising at least one impurity that is less volatile than carbon dioxide, said process comprising:
- feeding crude carbon dioxide feed at sub-ambient temperature to a distillation column system operating at super-atmospheric pressure(s) for separation to produce carbon dioxide-enriched overhead vapour and bottoms liquid enriched with said at least one impurity;
providing carbon dioxide-enriched liquid as reflux for said distillation column system;
at least partially re-boiling a portion of said bottoms liquid by indirect heat exchange to provide vapour for said distillation column system;
removing carbon dioxide-enriched overhead vapour from said distillation column system; and
removing a further portion of said bottoms liquid, or a liquid derived from bottoms liquid, from said distillation column system,wherein re-boiling duty for said distillation column system is provided at least in part by indirect heat exchange against recycle fluids from at least one heat pump cycle using a carbon dioxide-containing fluid from said distillation column system as working fluid, at least one of said recycle fluids having a different pressure from the other recycle fluid(s).
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Abstract
Impurities that are less volatile than carbon dioxide, e.g. hydrogen sulphide, are removed from crude carbon dioxide by processes involving sub-ambient distillation of said crude carbon dioxide in a distillation column system operating at super-atmospheric pressure(s) to produce carbon dioxide-enriched overhead vapour and bottoms liquid enriched with said impurities. Where such processes involve at least one heat pump cycle, significant savings in power consumption are realised when the process uses more than one recycle pressure in the heat pump cycle(s).
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Citations
65 Claims
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1. A process for purifying crude carbon dioxide comprising at least one impurity that is less volatile than carbon dioxide, said process comprising:
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feeding crude carbon dioxide feed at sub-ambient temperature to a distillation column system operating at super-atmospheric pressure(s) for separation to produce carbon dioxide-enriched overhead vapour and bottoms liquid enriched with said at least one impurity; providing carbon dioxide-enriched liquid as reflux for said distillation column system; at least partially re-boiling a portion of said bottoms liquid by indirect heat exchange to provide vapour for said distillation column system; removing carbon dioxide-enriched overhead vapour from said distillation column system; and removing a further portion of said bottoms liquid, or a liquid derived from bottoms liquid, from said distillation column system, wherein re-boiling duty for said distillation column system is provided at least in part by indirect heat exchange against recycle fluids from at least one heat pump cycle using a carbon dioxide-containing fluid from said distillation column system as working fluid, at least one of said recycle fluids having a different pressure from the other recycle fluid(s). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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55. A process for purifying crude carbon dioxide comprising at least one impurity that is less volatile than carbon dioxide, said process comprising:
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feeding crude carbon dioxide feed at sub-ambient temperature to a distillation column system operating at super-atmospheric pressure(s) for separation to produce carbon dioxide-enriched overhead vapour and bottoms liquid enriched with said at least one impurity; removing said carbon dioxide-enriched overhead vapour from said distillation column system and warming at least a portion of said carbon dioxide-enriched overhead vapour by indirect heat exchange to produce warmed carbon dioxide-enriched gas; compressing a first working fluid comprising said warmed carbon dioxide-enriched gas to produce at least one compressed carbon dioxide-enriched gas; cooling and at least partially condensing at least a portion of said compressed carbon dioxide-enriched gas as a first recycle fluid by indirect heat exchange to produce carbon dioxide-enriched fluid; expanding said carbon dioxide-enriched fluid to produce expanded carbon dioxide-enriched fluid and feeding said expanded carbon dioxide-enriched fluid to said distillation column system, at least a portion of which being used as reflux; compressing a second working fluid comprising carbon dioxide-rich gas from said distillation column system to produce at least one second recycle fluid; cooling and optionally condensing at least a portion of said second recycle fluid by indirect heat exchange to produce cooled carbon dioxide-rich fluid; after expansion as required, feeding at least a portion of said cooled carbon dioxide-rich fluid to said distillation column system; at least partially re-boiling a portion of said bottoms liquid by indirect heat exchange to produce vapour for said distillation column system; and removing a further portion of said bottoms liquid, or a liquid derived from bottoms liquid, from said distillation column system, wherein re-boiling duty for said distillation column system is provided at least in part by indirect heat exchange against said first and second recycle fluids, said first recycle fluid having a different pressure from said second recycle fluid. - View Dependent Claims (56, 57, 58, 60, 61, 62, 63, 65)
wherein said first and second compression systems are capable of compressing said warmed carbon dioxide-enriched gas and said carbon dioxide-rich gas respectively to different pressures.
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61. Apparatus of claim 60 comprising a conduit arrangement for feeding compressed carbon dioxide enriched-gas from said first compressor system as feed to said second compressor system.
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62. Apparatus of claim 60 comprising:
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a fifth heat exchanger arrangement for warming a carbon dioxide-rich vapour by indirect heat exchange to produce warmed carbon dioxide-rich gas; a conduit arrangement for feeding carbon dioxide-rich vapour from an intermediate location in said distillation column system to said fifth heat exchanger arrangement; and a conduit arrangement for feeding warmed carbon dioxide-rich gas from said fifth heat exchanger arrangement to said second compressor system.
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63. Apparatus of claim 60, comprising a sixth heat exchanger arrangement for at least partially re-boiling liquid from an intermediate location in said distillation column system to provide additional vapour for said distillation column system.
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65. Apparatus of any of claims 60 to 64, wherein said heat exchanger arrangements are passages within a single main heat exchanger.
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59. A process for purifying crude carbon dioxide comprising at least one impurity that is less volatile than carbon dioxide, said process comprising:
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feeding crude carbon dioxide feed at sub-ambient temperature to a distillation column system operating at super-atmospheric pressure(s) for separation to produce carbon dioxide-enriched overhead vapour and bottoms liquid enriched with said at least one impurity; condensing a portion of said carbon dioxide-enriched overhead vapour by indirect heat exchange to provide reflux for said distillation column system; removing a further portion of said carbon dioxide-enriched overhead vapour from said distillation system; removing carbon dioxide-rich liquid from an intermediate location in said distillation column system and expanding said liquid to produce expanded carbon dioxide-rich liquid; warming and evaporating said expanded carbon dioxide-rich liquid by indirect heat exchange to provide warmed carbon dioxide-rich gas; compressing a working fluid comprising said warmed carbon dioxide-rich gas to produce at least one compressed carbon dioxide-rich gas as a first recycle fluid and at least one further compressed carbon dioxide-rich gas as a second recycle fluid; cooling and optionally at least partially condensing said first recycle fluid by indirect heat exchange to produce cooled first carbon dioxide-rich fluid; combining said cooled first carbon dioxide-rich fluid with crude carbon dioxide fluid to produce said crude carbon dioxide feed for the distillation column system; cooling and at least partially condensing said second recycle fluid by indirect heat exchange to produce cooled second carbon dioxide-rich fluid; expanding said cooled second carbon dioxide-rich fluid to produce expanded carbon dioxide-rich fluid; combining said expanded carbon dioxide-rich fluid with a fluid selected from the group consisting of said carbon dioxide-rich liquid, said expanded carbon dioxide-rich liquid, and said warmed carbon dioxide-rich gas; at least partially re-boiling a portion of said bottoms liquid by indirect heat exchange against at least one “
warm”
process stream to produce vapour for said distillation column system; andremoving a further portion of said bottoms liquid, or a liquid derived from bottoms liquid, from said distillation column system, wherein said re-boiling duty is provided at least in part by indirect heat exchange against said first and second recycle fluids and wherein, in embodiments in which said expanded carbon dioxide-rich fluid is combined with said warmed carbon dioxide-rich gas, said expanded carbon dioxide-rich fluid is first warmed and evaporated by indirect heat exchange to produce further warmed carbon dioxide-rich gas for said combination with said warmed carbon dioxide-rich gas. - View Dependent Claims (64)
wherein, in embodiments in which said expanded carbon dioxide-rich fluid is combined with said warmed carbon dioxide-rich gas, said apparatus comprises sixth heat exchanger arrangement for warming expanded carbon dioxide-rich fluid by indirect heat exchange to produce further warmed carbon dioxide-rich gas for said combination with said warmed carbon dioxide-rich gas.
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Specification