EP1797384A1 - Air separation process using cryogenic distillation - Google Patents

Air separation process using cryogenic distillation

Info

Publication number
EP1797384A1
EP1797384A1 EP05779057A EP05779057A EP1797384A1 EP 1797384 A1 EP1797384 A1 EP 1797384A1 EP 05779057 A EP05779057 A EP 05779057A EP 05779057 A EP05779057 A EP 05779057A EP 1797384 A1 EP1797384 A1 EP 1797384A1
Authority
EP
European Patent Office
Prior art keywords
column
less
oxygen
diameter
pressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP05779057A
Other languages
German (de)
French (fr)
Other versions
EP1797384B1 (en
Inventor
Olivier Bruder
Patrick Le Bot
Richard Dubettier-Grenier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Original Assignee
Air Liquide SA
LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Application filed by Air Liquide SA, LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude filed Critical Air Liquide SA
Publication of EP1797384A1 publication Critical patent/EP1797384A1/en
Application granted granted Critical
Publication of EP1797384B1 publication Critical patent/EP1797384B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/0489—Modularity and arrangement of parts of the air fractionation unit, in particular of the cold box, e.g. pre-fabrication, assembling and erection, dimensions, horizontal layout "plot"
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
    • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/04896—Details of columns, e.g. internals, inlet/outlet devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
    • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
    • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
    • F25J3/04763—Start-up or control of the process; Details of the apparatus used
    • F25J3/04866—Construction and layout of air fractionation equipments, e.g. valves, machines
    • F25J3/04896—Details of columns, e.g. internals, inlet/outlet devices
    • F25J3/04909—Structured packings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/10—Mathematical formulae, modeling, plot or curves; Design methods
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/12—Particular process parameters like pressure, temperature, ratios
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/20—Particular dimensions; Small scale or microdevices

Definitions

  • the present invention relates to an air separation process using cryogenic distillation.
  • it relates to air separation processes for the production of large quantities of oxygen with a content of greater than 90 mol% with a yield of greater than 90% in a unit comprising at least one column operating at low pressure and at least one column operating at high pressure, at least one column of which containing at least one section of structured packings of the cross-corrugated type.
  • US-A-5653126 describes the use of cross-corrugated structured packings having a density of at least 500 m 2 /m 3 with a low HETP for the separation of air.
  • cross-corrugated packings have corrugations at 45° with the axis of the column in which they are installed.
  • the packings may or may not be perforated and are generally formed by folded metal foil strips .
  • the object of the present invention is to alleviate the problems of the prior art by allowing the column diameters to be reduced for a given oxygen production.
  • One object of the invention is to provide a process for the separation of air into at least one constituent by cryogenic distillation of air in a system of columns comprising at least one column a) for producing at least gaseous oxygen as product, such that the oxygen yield is greater than 90% (preferably 95%) and the oxygen purity is greater than 90 mol% oxygen (preferably 95 mol% oxygen or even 99 mol% oxygen) and/or b) for producing at least nitrogen such that the nitrogen yield is greater than 85% (preferably greater than 90%) and the nitrogen purity is greater than 99 mol% nitrogen (preferably 99.99 mol% nitrogen or even 99.999 mol% nitrogen) characterized in that:
  • Q a ir is the sum of the flow rates in Sm /h of the air feeding the column system;
  • K is the capacity per unit area of the column and equals at least 21000 Sm 3 /m 2 (preferably at least 23000 Sm 3 /m 2 or even at least 25000 Sm 3 /m 2 ) ;
  • Po is equal to 2 bar abs .
  • the yield is the percentage number of oxygen molecules in all the oxygen-rich products relative to the number of oxygen molecules in the feed air for the separation unit.
  • the capacity per unit area of the column is the ratio of the molar volume of gas sent into the column to the mean cross section of the column.
  • the largest-diameter column of the column system contains at least one section filled with a gas/liquid contactor allowing material exchange between the gaseous phase and the liquid phase such that its effectiveness is defined by a TUH (Transfer Unit Height) of less than 350 mm (preferably less than 300 mm) ;
  • the gas/liquid contactor is composed of cross-corrugated structured packings having a density of less than 500 m 2 /m 3 , preferably less than 400 m 2 /m 3 ;
  • the column system comprises at least one double column formed by a medium-pressure column and a low-pressure column, the medium-pressure column being thermally coupled to the low-pressure column, and the low-pressure column constituting the largest-diameter column;
  • the ratio of the oxygen produced to the cross section of the low-pressure column is greater than or equal to 150 t/d/m 2 ; the ratio of the flow rate of air sent to the column system to the cross section of the low-pressure column is not less than 21000 S
  • At least one section of the medium-pressure column contains cross-corrugated structured packings with a density not exceeding 500 m 2 /m 3 , or even 400 m 2 /m 3 .
  • this is economically advantageous as even if the height of the columns is increased and the architecture is modified, the diameter reduction effect is predominant.
  • the drawback of the increased height can be resolved by placing the column sections at the desired height, side by side with fluid transfer pipes.
  • the largest-diameter column contains only cross-corrugated structured packings having a density not exceeding 500 m 2 /m 3 , or even 400 m 2 /m 3 .
  • all the columns of the column system contain only cross-corrugated structured packings having a density not exceeding 500 m 2 /m 3 , or even 400 m 2 /m 3 .
  • a fluid will be called a "product" if it is output from the air separation unit with the content of one of its constituents being: greater than 85 mol%, if the constituent is oxygen; - greater than 95 mol%, if the constituent is nitrogen.
  • the extraction efficiency of a constituent will be defined by the ratio of the molar quantity of the said constituent entering the separation unit via the feed fluids to the molar quantity of the same constituent leaving via the product (s), the content of this constituent being greater than or equal to those mentioned above.
  • Cross-corrugated structured packings with a density not exceeding 500 m 2 /m 3 , or even 400 m 2 /m 3 may be installed in the medium-pressure column and/or the low-pressure column of a double column, in the medium-pressure column and/or the low-pressure column and/or the intermediate-pressure column of a triple (Etienne) column, an argon column, a mixing column or any other type of air gas separation column.
  • a packing has a density of less than 500 m 2 /m 3 if its mean density (without deducting the area of any perforations) does not exceed 500 m 2 /m 3 .
  • FIG 1 shows an air separation unit according to the invention.
  • a double column comprises a medium-measure column 1 operating at between 5 bar abs and 20 bar abs and a low-pressure column 3 operating at apressure between 1.2 bar abs and 8 bar abs.
  • the low-pressure column is larger in diameter than the medium-pressure column, but it is possible in some cases for the medium-presure column to be larger in diameter than the low pressure column.
  • the two columns are thermally coupled to each other by a reboiler/condensor 5, for example of the bath type.
  • the low-pressure column 3 contains only sections of structured packings 2 having a density not exceeding 500 m 2 /m 3 , for example having a density of 400 m 2 /m 3 .
  • the medium-pressure column 1 contains only sections of structured packings 2 having a density close or identical to the above values .
  • a stream of cooled and purified air 7 is sent to the medium-pressure column 1 and oxygen-enriched and nitrogen-enriched liquid streams 9, 11 are sent from the medium-pressure column to the low-pressure column after an expansion step.
  • gaseous oxygen 13 Withdrawn from the bottom of the low-pressure column is a stream of gaseous oxygen 13 as product, with an oxygen yield of greater than 90% (preferably greater than 95%) .
  • the oxygen purity is greater than 90 mol% oxygen (preferably greater than 95 mol% oxygen or even 99 mol% oxygen) .
  • gaseous nitrogen 15 is withdrawn with a nitrogen yield of greater than 85% (preferably greater than 90%) .
  • the purity of the nitrogen is greater than 99 mol% nitrogen (preferably greater than 99.99 mol% nitrogen or even 99.999 mol% nitrogen) .
  • a stream of waste nitrogen 17 is withdrawn from an upper level of the low-pressure column.
  • the diameter (in metres) of the low-pressure column is less than:
  • Q a ir is the sum of the flow rates in Sm 3 /h of the air feeding the column system
  • K is the capacity per unit area of the column and equals at least 21000 Sm 3 /m 2 (preferably at least 23000 SmVm 2 or even at least 25000 Sm 3 /m 2 ) ;
  • Po is equal to 2 bar abs .

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Separation By Low-Temperature Treatments (AREA)
  • Fertilizers (AREA)

Abstract

[ 4   Q air π   K  ( P P 0 )  0.35 ]  1 / 2 ( I ) In a process for the separation of air into at least one constituent by cryogenic distillation of air in a system of columns (1, 3) comprising at least one column (1, 3) for producing at least gaseous oxygen and/or nitrogen as product, if the operating pressure of the largest-diameter column is P>2 bar abs, then the diameter (in metres) of this column is less than (I), where : Qair is the sum of the flow rates in Sm3/h of the air feeding the column system and K is the capacity per unit area of the column and P0 is equal to 2 bar abs.

Description

Air separation process using cryogenic distillation
The present invention relates to an air separation process using cryogenic distillation. In particular, it relates to air separation processes for the production of large quantities of oxygen with a content of greater than 90 mol% with a yield of greater than 90% in a unit comprising at least one column operating at low pressure and at least one column operating at high pressure, at least one column of which containing at least one section of structured packings of the cross-corrugated type.
Cross-corrugated packings are described in EP-A-O 367 817 and EP-A-O 491 591.
US-A-5653126 describes the use of cross-corrugated structured packings having a density of at least 500 m2/m3 with a low HETP for the separation of air.
Typically, cross-corrugated packings have corrugations at 45° with the axis of the column in which they are installed. The packings may or may not be perforated and are generally formed by folded metal foil strips .
The increase in demand for gas separation units of large capacity (production greater than 2000 tonnes of gas produced per day) has led to the need to design distillation columns of increasing diameter, despite the frequent use of pressurized distillation processes (with columns operating at pressures above 2 bar abs) .
Transport problems become significant when the diameter of the elements exceeds 3m, or even 4.5m, and these are sometimes insurmountable for columns greater than 6m in diameter. If it was desired to increase the ratio of oxygen production (in t/d of pure product) to cross section
(in m2) of the low-pressure column, that is to say to reduce the diameter of the low-pressure column for constant oxygen production (or given air throughput) , for a unit comprising a medium-pressure column thermally coupled to a low-pressure column or for a unit comprising three columns, including a medium-pressure column thermally coupled to a low-pressure column and an intermediate-pressure column fed from the medium-pressure column, the only solutions were:
• to increase the withdrawal of nitrogen from the medium-pressure column (or from the intermediate-pressure column) , but above a level of withdrawal representing between 15-20% of the air throughput, it is found that: o either the oxygen yield of the unit drops dramatically for a given oxygen purity o or the oxygen purity drops dramatically for a given oxygen withdrawal;
• to increase the pressure of the unit (low pressure > 2 bar abs), but this is highly penalizing from the energy standpoint if the pressure of the waste nitrogen is not utilized (that is to say by expansion in order to make liquid, or as product pressure) .
In an air separation unit producing large quantities of oxygen and nitrogen, if it was desired to reduce the diameter of this column, the only solutions were:
• to increase the withdrawal of lean liquid and of liquid nitrogen, but above a certain ratio it is found that the purity of the nitrogen and of the lean liquids dramatically drops and that the oxygen yield of the unit collapses;
• to increase the flow of blown air, but above a certain ratio the performance of the unit is greatly degraded - reduction in oxygen yield (or in oxygen purity) , reduction in medium-pressure gaseous nitrogen (or in purity of medium-pressure gaseous nitrogen) ;
• to increase the liquid air flow, but this flow is set by the production of pumped products and the production of liquid products (liquid oxygen, liquid nitrogen, liquid argon) , or a substantial loss of energy;
• to increase the pressure of the unit (with a medium pressure > 8 bar abs) , but this is highly disadvantageous from the energy standpoint if the pressure of the waste nitrogen is not utilized (that is to say by expansion in order to make liquid, or as product pressure) .
The object of the present invention is to alleviate the problems of the prior art by allowing the column diameters to be reduced for a given oxygen production.
One object of the invention is to provide a process for the separation of air into at least one constituent by cryogenic distillation of air in a system of columns comprising at least one column a) for producing at least gaseous oxygen as product, such that the oxygen yield is greater than 90% (preferably 95%) and the oxygen purity is greater than 90 mol% oxygen (preferably 95 mol% oxygen or even 99 mol% oxygen) and/or b) for producing at least nitrogen such that the nitrogen yield is greater than 85% (preferably greater than 90%) and the nitrogen purity is greater than 99 mol% nitrogen (preferably 99.99 mol% nitrogen or even 99.999 mol% nitrogen) characterized in that:
• if the operating pressure of the largest-diameter column is P<2 bar abs, then the diameter (in metres) of this column is less than:
if the operating pressure of the largest-diameter column is P > 2 bar abs, then the diameter (in metres) of this column is less than:
1A
where:
Qair is the sum of the flow rates in Sm /h of the air feeding the column system; K is the capacity per unit area of the column and equals at least 21000 Sm3/m2 (preferably at least 23000 Sm3/m2 or even at least 25000 Sm3/m2) ; and
Po is equal to 2 bar abs .
The yield is the percentage number of oxygen molecules in all the oxygen-rich products relative to the number of oxygen molecules in the feed air for the separation unit.
The capacity per unit area of the column is the ratio of the molar volume of gas sent into the column to the mean cross section of the column.
According to other optional features : - the largest-diameter column of the column system contains at least one section filled with a gas/liquid contactor allowing material exchange between the gaseous phase and the liquid phase such that its effectiveness is defined by a TUH (Transfer Unit Height) of less than 350 mm (preferably less than 300 mm) ; the gas/liquid contactor is composed of cross-corrugated structured packings having a density of less than 500 m2/m3, preferably less than 400 m2/m3; - the column system comprises at least one double column formed by a medium-pressure column and a low-pressure column, the medium-pressure column being thermally coupled to the low-pressure column, and the low-pressure column constituting the largest-diameter column; - the ratio of the oxygen produced to the cross section of the low-pressure column is greater than or equal to 150 t/d/m2; the ratio of the flow rate of air sent to the column system to the cross section of the low-pressure column is not less than 21000 Sm3/h/m2, preferably not less than 23000 Sm3/h/m2 and even more preferably not less than 25000 Sm3/h/m2; the ratio of the gaseous air sent to the medium-pressure column to the cross section of the low-pressure column is not less than 18000 Sm3/h/m2
(preferably not less than 20000 Sm3/h/m2 and even more preferably not less than 22000 Sm3/h/m2) ; and at least one section of the medium-pressure column contains cross-corrugated structured packings with a density not exceeding 500 m2/m3, or even 400 m2/m3.
It is another object of the invention to provide an air separation unit using cryogenic distillation, comprising a column system, the diameter of the largest-diameter column being between 3 and 6m, the largest-diameter column containing at least one gas/liquid contactor section consisting of cross-corrugated structured packings having a density not exceeding 500 m2/m3, or even 400 m2/m3. Surprisingly, this is economically advantageous as even if the height of the columns is increased and the architecture is modified, the diameter reduction effect is predominant. Moreover, the drawback of the increased height can be resolved by placing the column sections at the desired height, side by side with fluid transfer pipes. Preferably, the largest-diameter column contains only cross-corrugated structured packings having a density not exceeding 500 m2/m3, or even 400 m2/m3.
In certain cases, all the columns of the column system contain only cross-corrugated structured packings having a density not exceeding 500 m2/m3, or even 400 m2/m3.
A fluid will be called a "product" if it is output from the air separation unit with the content of one of its constituents being: greater than 85 mol%, if the constituent is oxygen; - greater than 95 mol%, if the constituent is nitrogen.
The extraction efficiency of a constituent will be defined by the ratio of the molar quantity of the said constituent entering the separation unit via the feed fluids to the molar quantity of the same constituent leaving via the product (s), the content of this constituent being greater than or equal to those mentioned above.
Cross-corrugated structured packings with a density not exceeding 500 m2/m3, or even 400 m2/m3, may be installed in the medium-pressure column and/or the low-pressure column of a double column, in the medium-pressure column and/or the low-pressure column and/or the intermediate-pressure column of a triple (Etienne) column, an argon column, a mixing column or any other type of air gas separation column.
A packing has a density of less than 500 m2/m3 if its mean density (without deducting the area of any perforations) does not exceed 500 m2/m3. The invention will be described in greater detail with reference to the figure.
Figure 1 shows an air separation unit according to the invention.
In a unit according to the invention, a double column comprises a medium-measure column 1 operating at between 5 bar abs and 20 bar abs and a low-pressure column 3 operating at apressure between 1.2 bar abs and 8 bar abs. The low-pressure column is larger in diameter than the medium-pressure column, but it is possible in some cases for the medium-presure column to be larger in diameter than the low pressure column. The two columns are thermally coupled to each other by a reboiler/condensor 5, for example of the bath type.
The low-pressure column 3 contains only sections of structured packings 2 having a density not exceeding 500 m2/m3, for example having a density of 400 m2/m3.
The medium-pressure column 1 contains only sections of structured packings 2 having a density close or identical to the above values .
A stream of cooled and purified air 7 is sent to the medium-pressure column 1 and oxygen-enriched and nitrogen-enriched liquid streams 9, 11 are sent from the medium-pressure column to the low-pressure column after an expansion step.
Withdrawn from the bottom of the low-pressure column is a stream of gaseous oxygen 13 as product, with an oxygen yield of greater than 90% (preferably greater than 95%) . The oxygen purity is greater than 90 mol% oxygen (preferably greater than 95 mol% oxygen or even 99 mol% oxygen) . At the top of the low-pressure column, gaseous nitrogen 15 is withdrawn with a nitrogen yield of greater than 85% (preferably greater than 90%) . The purity of the nitrogen is greater than 99 mol% nitrogen (preferably greater than 99.99 mol% nitrogen or even 99.999 mol% nitrogen) .
A stream of waste nitrogen 17 is withdrawn from an upper level of the low-pressure column.
The diameter (in metres) of the low-pressure column is less than:
where:
Qair is the sum of the flow rates in Sm3/h of the air feeding the column system;
K is the capacity per unit area of the column and equals at least 21000 Sm3/m2 (preferably at least 23000 SmVm2 or even at least 25000 Sm3/m2) ; and
Po is equal to 2 bar abs .
To give a numerical example, it will be assumed that an installation has to treat an air throughput of 500 000 Sm3/h. According to the invention, if the low-pressure column is operated at a pressure below 2 bar abs, the cross section of the low-pressure column will therefore be less than:
(500000/21000)m2
(preferably less than (500000/23000) m2 or even less than (500000/25000) m2) and the diameter less than:
4(500000/21000 1A π i.e. 5.5m (preferably 5.26m, or even at most 5.05m) . If the low-pressure column is operated at 3 bar abs, the cross section of the low-pressure column will therefore be less than:
(500000^ 2
[21000 J m
(preferably less than (500000/23000) m2 or even less than (5000000/25000) m2) and the diameter less than:
i.e. 5.13m (preferably 4.9 m, or even at most 4.7 m) .

Claims

1. Process for the separation of air into at least one constituent by cryogenic distillation of air in a system of columns (1, 3) comprising at least one column (1, 3) a) for producing at least gaseous oxygen as product, such that the oxygen yield is greater than 90%
(preferably 95%) and the oxygen purity is greater than 90 mol% oxygen (preferably 95 mol% oxygen or even 99 mol% oxygen) and/or b) for producing at least nitrogen such that the nitrogen yield is greater than 85% (preferably greater than 90%) and the nitrogen purity is greater than 99 mol% nitrogen (preferably 99.99 mol% nitrogen or even 99.999 mol% nitrogen) characterized in that:
• if the operating pressure of the largest-diameter column (3) is P<2 bar abs, then the diameter (in metres) of this column is less than:
if the operating pressure of the largest-diameter column is P > 2 bar abs, then the diameter (in metres) of this column is less than:
where:
Qair is the sum of the flow rates in Sm3/h of the air feeding the column system;
K is the capacity per unit area of the column and equals at least 21000 Sm3/m2 (preferably at least 23000 SmVm2 or even at least 25000 Sm3/m2) ; and
Po is equal to 2 bar abs .
2. Process according to Claim 1, in which the largest-diameter column (3) of the column system contains at least one section (2) filled with a gas/liquid contactor allowing material exchange between the gaseous phase and the liquid phase such that its effectiveness is defined by a TUH (Transfer Unit Height) of less than 350 mm (preferably less than 300 mm) .
3. Process according to Claim 2, in which the gas/liquid contactor is composed of cross-corrugated structured packings having a density of less than 500 m2/m3, preferably less than 400 m2/m3.
4. Process according to Claim 1, 2 or 3, in which the column system comprises at least one double column formed by a medium-pressure column (3) and a low-pressure column (1), the medium-pressure column being thermally coupled to the low-pressure column, and the low-pressure column constituting the largest-diameter column.
5. Process according to Claim 4, producing oxygen in which the ratio of the oxygen produced to the cross section of the low-pressure column is greater than or equal to 150 t/d/m2.
6. Process according to Claim 4 or 5, in which the ratio of the flow rate of air sent to the column system to the cross section of the low-pressure column is not less than 21000 Sm3/h/m2, preferably not less than 23000 Sm3/h/m2 and even more preferably not less than 25000 Sm3/h/m2.
7. Process according to Claim 4, 5 or 6, in which the ratio of the gaseous air sent to the medium-pressure column (1) to the cross section of the low-pressure column is not less than 18000 Sm3/h/m2 (preferably not less than 20000 Sm3/h/m2 and even more preferably not less than 22000 Sm3/h/m2) .
8. Process according to Claim 7, in which at least one section (2) of the medium-pressure column (1) contains cross-corrugated structured packings with a density not exceeding 500 m2/m3, or even 400 m2/m3.
9. Air separation unit using cryogenic distillation, comprising a column system, the diameter of the largest-diameter column (3) being between 3 and 6m, the largest-diameter column containing at least one gas/liquid contactor section (2) consisting of cross-corrugated structured packings having a density not exceeding 500 m2/m3, or even 400 m2/m3.
EP05779057A 2004-09-21 2005-08-10 Air separation process using cryogenic distillation Revoked EP1797384B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0452099A FR2875588B1 (en) 2004-09-21 2004-09-21 AIR SEPARATION METHOD BY CRYOGENIC DISTILLATION
PCT/EP2005/053938 WO2006048341A1 (en) 2004-09-21 2005-08-10 Air separation process using cryogenic distillation

Publications (2)

Publication Number Publication Date
EP1797384A1 true EP1797384A1 (en) 2007-06-20
EP1797384B1 EP1797384B1 (en) 2009-07-22

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EP05779057A Revoked EP1797384B1 (en) 2004-09-21 2005-08-10 Air separation process using cryogenic distillation

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US (1) US20100115995A1 (en)
EP (1) EP1797384B1 (en)
JP (1) JP2008513719A (en)
CN (1) CN100547327C (en)
AT (1) ATE437347T1 (en)
CA (1) CA2579450A1 (en)
DE (1) DE602005015603D1 (en)
FR (1) FR2875588B1 (en)
WO (1) WO2006048341A1 (en)
ZA (1) ZA200702344B (en)

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CN113654302B (en) * 2021-08-12 2023-02-24 乔治洛德方法研究和开发液化空气有限公司 A device and method for cryogenic air separation

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Also Published As

Publication number Publication date
ZA200702344B (en) 2008-08-27
WO2006048341A1 (en) 2006-05-11
EP1797384B1 (en) 2009-07-22
CN100547327C (en) 2009-10-07
FR2875588A1 (en) 2006-03-24
JP2008513719A (en) 2008-05-01
CA2579450A1 (en) 2006-05-11
FR2875588B1 (en) 2007-04-27
CN101023309A (en) 2007-08-22
ATE437347T1 (en) 2009-08-15
US20100115995A1 (en) 2010-05-13
DE602005015603D1 (en) 2009-09-03

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