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EP-4737828-A1 - AIR SEPARATION UNIT AND AIR SEPARATION METHOD

EP4737828A1EP 4737828 A1EP4737828 A1EP 4737828A1EP-4737828-A1

Abstract

An air separation unit (100) is provided, the air separation unit (100) comprising a column system (10) including a pressure column (11) configured to be operated at a first pressure level and a low pressure column (12) configured to be operated at a second pressure level below the first pressure level and a Joule-Thomson expansion unit (7) configured to expand a Joule-Thomson stream (101) of compressed, pre-purified and cooled feed air into a phase-separating unit (200) provided in the pressure column (11). The phase-separating unit (200) is provided in the pressure column (11) beneath a separation section (16) and the phase-separating unit (200) comprises a roof structure (201) configured to restrict an inflow of cryogenic liquid draining from the separation section (16) into the phase-separating unit (200). A corresponding method is also provided.

Inventors

  • Brown C, Steven
  • CHALAKOVA, MARIYANA
  • Flegiel, Felix
  • Florian, Hanusch
  • Lauchner, Daniel
  • MATAMOROS, LUIS
  • MATTEN, CHRISTIAN

Assignees

  • Linde GmbH

Dates

Publication Date
20260506
Application Date
20241105

Claims (11)

  1. An air separation unit (100) comprising a column system (10) including a pressure column (11) configured to be operated at a first pressure level and a low pressure column (12) configured to be operated at a second pressure level below the first pressure level; and a Joule-Thomson expansion unit (7) configured to expand a Joule-Thomson stream (101) of compressed, pre-purified and cooled feed air into a phase-separating unit (200) provided in the pressure column (11), wherein the phase-separating unit (200) is provided in the pressure column (11) beneath a separation section (16) and the phase-separating unit (200) comprises a roof structure (201) configured to restrict an inflow of a cryogenic liquid draining from the separation section (16) into the phase-separating unit (200).
  2. The air separation unit (100) according to claim 1, wherein the phase-separating unit (200) comprises an upper compartment (210) and a lower compartment (220) arranged beneath the upper compartment, the upper compartment (210) being delimited to a region above the upper compartment (210) by said roof structure (201) and to the lower compartment (220) by a dividing structure (202) including liquid passages (203).
  3. The air separation unit (100) according to claim 2, wherein the liquid passages (203) are provided as slits and/or holes in the same or different positions, sizes and/or densities in the dividing structure (202).
  4. The air separation unit (100) according to claim 2 or 3, wherein the upper compartment (210) is comprises a feed port (211) configured to be supplied with the Joule-Thomson stream (101) downstream of the Joule-Thomson expansion unit (7) and the lower compartment (220) comprises a withdrawal port (221) configured to withdraw liquid from the lower compartment (220).
  5. The air separation unit (100) according to any one of claims 2 to 4, wherein the upper compartment (210) is provided with a longitudinal shape comprising two longitudinal side walls (212), a first transverse side wall (213) and a second transverse side wall (214), the feed port (214) being provided in the first transverse side wall (214) and the second transverse side wall (214) being arranged to provide an opening (215) between an upper edge of the second transverse side wall (214) and the roof structure (201) to an inner space of the pressure column (11).
  6. The air separation unit (100) according to any of claims 2 to 5, wherein the lower compartment (220) is provided with a longitudinal shape comprising two longitudinal side walls (222), a first transverse side walls (223) and a second transverse side wall (224), the lower compartment (220) comprising an opening (225) towards an inner space of the pressure column (11), the withdrawal port (221) being provided in the first transverse side wall (223) of the lower compartment (220) and beneath the feed port (211) to the upper compartment (210), and the opening (225) being a horizontal opening of the lower compartment (220) being adjacent to the second transverse side wall (224) of the lower compartment (220).
  7. The air separation unit (100) according claim 6, further comprising a longitudinal trough unit (300) comprising parallel side walls (302), a width of the trough unit (300) being smaller than a width of the upper compartment (210) of the phase-separating unit (200), the upper compartment (210) of the phase-separating unit (200) being arranged in the trough unit (300) such that the longitudinal side walls (222) are arranged in parallel and in a distance to the parallel side walls (302) of the trough unit (300), forming liquid channels.
  8. The air separation unit (100) according claim 7, wherein a bottom wall (303) of the trough unit (300) is arranged in parallel with and/or at a same geodetic elevation as the dividing structure (202) of the phase-separating unit (200), the trough unit (300) comprising a liquid weir configured to provide a liquid level (305) in the trough unit (300).
  9. A method for cryogenic separation of air, comprising: providing an air separation unit (100) comprising a column system (10) including a pressure column (11), a low pressure column (12), a Joule-Thomson expansion unit (7) and a phase-separating unit (200), the phase-separating unit (200) being arranged in the pressure column (11) beneath a separation section (16) thereof, and comprising a roof structure (201); operating the pressure column (11) at a first pressure level and the low pressure column (12) at a second pressure level; and expanding a Joule-Thomson stream (101) of compressed, pre-purified and cooled feed air into a phase-separating unit (200) provided in the pressure column (11) using the Joule-Thomson expansion unit (7), wherein an inflow of a cryogenic liquid draining from the separation section (16) into the phase-separating unit (200) is restricted by the roof structure (201).
  10. The method according to claim 9, further comprising: forming a biphasic stream by said expanding the Joule-Thomson stream (101); phase separating the biphasic stream using the phase-separating unit (200), forming a liquid phase and a gaseous phase; passing at least a major part of the gaseous phase from the phase-separating unit (200) into an inner space (17) of the pressure column (11); and withdrawing at least a major part of the liquid phase from the phase-separating unit (200) and from the pressure column (11) separately from further liquid withdrawn from the pressure column (11).
  11. The method according to claim 9 or 10, wherein an air separation unit (100) according to any of claims 1 to 8 is used.

Description

Field The present disclosure relates to an air separation unit and an air separation method. Background The production of air products in liquid or gaseous state by cryogenic separation of feed air in air separation units is well known and described, for example, in textbooks such as H.-W. Haring (ed.), "Industrial Gases Processing", Wiley-VCH, 2006, especially section 2.2.5, "Cryogenic Rectification". Air separation units may include rectification column systems provided as two-column systems, especially as double-column systems such as classical Linde double-column systems, but also as single-column, three-column or multi-column systems. In addition to rectification columns for the recovery of nitrogen and/or oxygen in the liquid and/or gaseous state, i.e. rectification columns for nitrogen-oxygen separation, such rectification column systems may comprise rectification columns for the recovery of other air components, in particular of noble gases. There is the desire for improvements in air separation units and corresponding processes, particularly in connection with the production of argon. Summary Against this background, an air separation unit and an air separation method comprising the features of the independent claims are proposed herein. Embodiments are the subject of the dependent claims and of the description that follows hereinbelow. An air separation unit provided according to the present disclosure comprises a column system including a pressure column configured to be operated at a first pressure level and a low pressure column configured to be operated at a second pressure level below the first pressure level and a Joule-Thomson expansion unit configured to expand a Joule-Thomson stream of compressed, pre-purified and cooled feed air into a phase-separating unit provided in the pressure column. The phase-separating unit is provided in the pressure column beneath a separation section and the phase-separating unit comprises a roof structure configured to restrict an inflow of a cryogenic liquid draining from the separation section into the phase-separating unit. As explained below in more detail, the biphasic throttle or Joule-Thomson stream may, after expansion, directly fed to the pressure column of an air separation unit in order to be able to dispense of an external separator. The vapor phase is supposed to remain in the pressure column, while the vast majority of the liquid phase (so-called Joule-Thomson liquid) is withdrawn and fed to the low pressure column. The liquid draining downwards in the pressure column has a higher argon content than the incoming Joule-Thomson liquid. If those liquids are mixed, the argon concentration in the stream withdrawn from the pressure column will increase by 2 to 3%. When fed into the low pressure column, the argon would then be vented together with "waste nitrogen" if the feed location is below the nitrogen section. In this case, some argon is lost. The phase-separating unit particularly reduces mixing of the liquid draining downwards in the pressure column with Joule-Thomson liquid, which is not the case in the current feed trough designs. One challenge is that there can be a net feed of the Joule-Thomson liquid into the column as well as a net draw. So while mixing should be avoided in principle, some liquid exchange must be possible. This challenge is overcome by embodiments proposed herein. Using the phase-separating unit provided herein both liquid phases can be kept separate to a certain extent, but a controlled exchange of liquids is still allowed. Embodiments proposed herein may particularly be combined with other proven constructive elements of other air separating unit internals. The phase-separating unit as proposed herein particularly comprises a trough-in-trough arrangement which allows for simultaneous vapor-liquid separation and liquid degassing and simultaneously avoids mixing of liquid draining downwards in the pressure column and the Joule-Thomson liquid. At the same time, the solution allows for a net liquid feed or draw if required by the process. The arrangement will not increase column height and can be accommodated with given trough dimensions. In certain embodiments proposed herein, the phase-separating unit comprises an upper compartment and a lower compartment arranged beneath the upper compartment, the upper compartment being delimited to a region above the upper compartment by said roof structure and to the lower compartment by a dividing structure including liquid passages. This allows an even downflow of Joule-Thomson liquid from the upper compartment to the lower compartment and may serve in reducing mixing with the liquid draining downwards in the pressure column. In certain embodiments proposed herein, the liquid passages are provided as slits and/or holes in the same and/or different positions, sizes and/or densities in the dividing structure. In such embodiments, the flow conditions may be adjusted by performing adapta