Process and apparatus for the separation by cryogenic distillation of a mixture of methane, carbon dioxide and hydrogen

Patent metadata

Field	Value
Publication number	US-10337791-B2
Application number	US-201314398980-A
Country	US
Kind code	B2
Filing date	Apr 29, 2013
Priority date	May 7, 2012
Publication date	Jul 2, 2019
Grant date	Jul 2, 2019

Abstract

In a process for the cryogenic separation of a feed mixture of at least carbon monoxide, hydrogen and methane, the feed mixture is separated in a methane wash column fed by a liquid methane stream at the top of the methane wash column to produce a gas enriched in hydrogen, a liquid stream from the bottom of the methane wash column is treated to produce a mixture of carbon monoxide and methane, the mixture of carbon monoxide and methane is separated in a separation column to produce a gas enriched in carbon monoxide and a liquid methane flow at least part of which forms a purge stream, the purge stream being varied to take account of load variations.

First claim

The invention claimed is:

1. A process for controlling a cryogenic separation of a feed mixture comprising carbon monoxide, hydrogen and at least 2% methane, the process comprising the steps of:
i) providing the feed mixture to a cold box, wherein the feed mixture is sourced from a syngas production facility, wherein a flow rate of the feed mixture is measured;
ii) cooling the feed mixture in a heat exchanger to produce a cold feed mixture at a first temperature;
iii) introducing the cold feed mixture to a methane wash column to produce a gas enriched in hydrogen and a liquid reduced in hydrogen;
iv) withdrawing the liquid reduced in hydrogen from the methane wash column and introducing the liquid reduced in hydrogen to a flash column to produce an impure hydrogen gas at a top portion of the flash column and a bottoms liquid comprising carbon monoxide and methane, wherein the flash column comprises a bottom reboiler;
v) introducing the bottoms liquid to a distillation column to produce a carbon monoxide-rich top gas and a methane-rich bottoms liquid;
vi) removing the methane-rich bottoms liquid from a bottom section of the distillation column;
vii) introducing a first portion of the methane-rich bottoms liquid to the methane wash column;
viii) vaporizing a second portion of the methane-rich bottoms liquid in the heat exchanger against the feed mixture;
wherein the bottom section of the distillation column comprises a liquid distributor, a reboiler section, and a storage section, wherein the liquid distributor is configured to receive falling liquid from within the distillation column and send the falling liquid to the reboiler section, wherein the storage section is configured to receive an overflow liquid from the reboiler section, wherein the liquid distributor is disposed above the storage section and the reboiler section, wherein the reboiler section and the storage section are disposed side by side within the bottom section of the distillation column, wherein a partition wall separates the storage section from the reboiler section, wherein the methane-rich bottoms liquid removed in step vi) is removed from the storage section of the bottom section; and
ix) adjusting a flow rate of the methane-rich bottoms liquid removed from the bottom section in step vi) based on the flow rate of the feed mixture,
wherein a flow rate of the second portion of the methane-rich bottoms liquid that is vaporized in the heat exchanger is adjusted higher if the measured flow rate of the feed mixture increases and is adjusted lower if the measured flow rate of the feed mixture decreases,
wherein the flow rate of the second portion of the methane-rich bottoms liquid vaporized in the heat exchanger is adjusted in order to maintain the cold feed mixture at the first temperature.

2. The process according to claim 1 , wherein a volume of liquid kept in the storage section fluctuates while the reboiler section is configured to operate with a constant liquid level.

3. The process according to claim 1 , wherein a liquid level within the methane wash column is controlled by adjusting a flow rate of the liquid reduced in hydrogen withdrawn from the methane wash column in step iv), wherein the liquid level within the methane wash column has a set point that is based on the measured flow rate of the feed mixture.

4. The process according to claim 1 , wherein a set point of a liquid level in the methane wash column is adjusted lower if the measured flow rate of the feed mixture increases and is adjusted higher if the measured flow rate of the feed mixture decreases.

5. The process according to claim 1 , wherein, in the event of a change in the measured flow rate of the feed mixture, a sump level within the flash column is maintained constant by altering a flow rate of the bottoms liquid withdrawn from the flash column.

6. The process according to claim 1 , wherein a volume of liquid in the storage section varies inversely based on the measured flow rate of the feed mixture while the reboiler section is configured to operate with a constant liquid level.

7. A process for controlling a cryogenic separation of a feed mixture comprising carbon monoxide, hydrogen and at least 2% methane, the process comprising the steps of:
i) providing the feed mixture to a cold box, wherein the feed mixture is sourced from a syngas production facility, wherein a flow rate of the feed mixture is measured;
ii) cooling the feed mixture in a heat exchanger to produce a cold feed mixture at a first temperature;
iii) introducing the cold feed mixture to a methane wash column to produce a gas enriched in hydrogen and a liquid reduced in hydrogen;
iv) withdrawing the liquid reduced in hydrogen from the methane wash column and introducing the liquid reduced in hydrogen to a flash column to produce an impure hydrogen gas at a top portion of the flash column and a bottoms liquid comprising carbon monoxide and methane, wherein the flash column comprises a bottom reboiler;
v) introducing the bottoms liquid to a distillation column to produce a carbon monoxide-rich top gas and a methane-rich bottoms liquid;
vi) removing the methane-rich bottoms liquid from a bottom section of the distillation column;
vii) introducing a first portion of the methane-rich bottoms liquid to the methane wash column;
viii) vaporizing a second portion of the methane-rich bottoms liquid in the heat exchanger against the feed mixture;
wherein the bottom section of the distillation column comprises a liquid distributor, a reboiler section, and a storage section, wherein the liquid distributor is configured to receive falling liquid from within the distillation column and send the falling liquid to the reboiler section, wherein the storage section is configured to receive an overflow liquid from the reboiler section, wherein the liquid distributor is disposed above the storage section and the reboiler section, wherein the reboiler section and the storage section are disposed side by side within the bottom section of the distillation column, wherein a partition wall separates the storage section from the reboiler section, wherein the methane-rich bottoms liquid removed in step vi) is removed from the storage section of the bottom section; and
ix) adjusting a flow rate of the methane-rich bottoms liquid removed from the bottom section in step vi) based on the flow rate of the feed mixture,
wherein a volume of liquid kept in the storage section fluctuates while the reboiler section is configured to operate with a constant liquid level,
wherein a set point of a liquid level in the methane wash column is adjusted lower if the measured flow rate of the feed mixture increases and is adjusted higher if the measured flow rate of the feed mixture decreases,
wherein, in the event of a change in the measured flow rate of the feed mixture, a sump level within the flash column is maintained constant by altering a flow rate of the bottoms liquid withdrawn from the flash column,
wherein a flow rate of the second portion of the methane-rich bottoms liquid that is vaporized in the heat exchanger is adjusted higher if the measured flow rate of the feed mixture increases and is adjusted lower if the measured flow rate of the feed mixture decreases, wherein the flow rate of the second portion of the methane-rich bottoms liquid vaporized in the heat exchanger is adjusted in an amount effective to maintain the cold feed mixture at the first temperature,
wherein a volume of liquid in the storage section reduces when the flow rate of the second portion of the methane-rich bottoms liquid vaporized in the heat exchanger increases, wherein the volume of liquid in the storage section increases when the flow rate of the second portion of the methane-rich bottoms liquid vaporized i

Assignees

• Air Liquide

Inventors

• Briglia Alain
• Brocheriou Emmanuelle
• Marty Pascal
• Prasad Bhadri

Classifications

• F25J5/005

  in a reboiler-condenser, e.g. within a column · CPC title

• F25J3/0261 Primary

  separation of carbon monoxide (production of carbon monoxide containing gas in general C01B32/40, C10J, C10K) · CPC title

• F25J3/0223

  H2/CO mixtures, i.e. synthesis gas; Water gas or shifted synthesis gas (production of carbon monoxide containing gas in general C01B32/40, C10J, C10K; production of hydrogen containing gas C01B3/00) · CPC title

• F25J2205/30

  using a washing, e.g. "scrubbing" or bubble column for purification purposes · CPC title

• F25J2280/02

  Control in general, load changes, different modes ("runs"), measurements · CPC title