GB2180923A - Process and apparatus for the production of pressurized nitrogen - Google Patents
Process and apparatus for the production of pressurized nitrogen Download PDFInfo
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- GB2180923A GB2180923A GB08615737A GB8615737A GB2180923A GB 2180923 A GB2180923 A GB 2180923A GB 08615737 A GB08615737 A GB 08615737A GB 8615737 A GB8615737 A GB 8615737A GB 2180923 A GB2180923 A GB 2180923A
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- 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
- F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
- F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
- F25J3/04309—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of nitrogen
- F25J3/04315—Lowest pressure or impure nitrogen, so-called waste nitrogen expansion
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- 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
- F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
- F25J3/04163—Hot end purification of the feed air
- F25J3/04169—Hot end purification of the feed air by adsorption of the impurities
- F25J3/04181—Regenerating the adsorbents
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- 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
- F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
- F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
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- 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
- F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
- F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
- F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
- F25J3/04303—Lachmann expansion, i.e. expanded into oxygen producing or low pressure column
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- 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
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- 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
- F25J3/0443—A main column system not otherwise provided, e.g. a modified double column flowsheet
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- 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
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/04—Processes or apparatus using separation by rectification in a dual pressure main column system
- F25J2200/06—Processes or apparatus using separation by rectification in a dual pressure main column system in a classical double column flow-sheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
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- 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
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/20—Processes or apparatus using separation by rectification in an elevated pressure multiple column system wherein the lowest pressure column is at a pressure well above the minimum pressure needed to overcome pressure drop to reject the products to atmosphere
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- 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
- F25J2200/00—Processes or apparatus using separation by rectification
- F25J2200/50—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column
- F25J2200/54—Processes or apparatus using separation by rectification using multiple (re-)boiler-condensers at different heights of the column in the low pressure column of a double pressure main column system
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- 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
- F25J2215/00—Processes characterised by the type or other details of the product stream
- F25J2215/50—Oxygen or special cases, e.g. isotope-mixtures or low purity O2
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- 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
- F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
- F25J2230/50—Processes or apparatus involving steps for increasing the pressure of gaseous process streams the fluid being oxygen
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- 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
- F25J2245/00—Processes or apparatus involving steps for recycling of process streams
- F25J2245/50—Processes or apparatus involving steps for recycling of process streams the recycled stream being oxygen
Abstract
A process and apparatus is provided for the production of nitrogen with over-atmospheric pressure by two-stage rectification of air at low temperatures. Air (1) is compressed (2), pre-purified (4, 6), cooled (33) in heat exchange with products of fractionation, and fed to the rectification device. An oxygen-enriched liquid (19) from the sump of the low-pressure stage (13) is vaporized (15) in contraflow to condensing nitrogen in the top of the low-pressure stage. Nitrogen (27) is extracted from the top of the low-pressure stage and may be mixed with nitrogen (30) from the top of the pressure stage (10). The vaporized oxygen-enriched liquid may be heated and used to regenerate the molecular sieves or screens (4, 6) used for pre-purification. <IMAGE>
Description
SPECIFICATION
Process and apparatus for the production of pressurized nitrogen
This invention relates to a process and apparatus for the production of pressurised nitrogen with overatmospheric pressure. More particularly it concerns a two-stage rectification of air at low temperatures, in which the air is compressed, pre-purified, cooled in heat exchange with products of fractionation and fed to a rectification device, in which process a liquid enriched with oxygen is extracted from the sump ofthe low-pressure stage ofthe rectification device and is at least partially vaporized, and in which process nitrogen is extracted from the top of the low-pressure stage. The invention also relates to an apparatus for performing the process.
A process of this type has already been disclosed in German Offenlegungsschrift DE-OS 3307181, wherein air is first compressed and then freed from undesired impurities, particularly H20 and CO2. The air is subsequently split up into two component streams, one of which is cooled during a heat exchange with products of decomposition and is fed to the pressure stage of a rectification device, whilstthe other component stream is first pressurised and then cooled, before it is fed to the pressure stage of the rectification device, is condensed in heat exchange with an oxygen-enriched liquid from the sump ofthe low-pressure stage of the device. The oxygen-rich liquid vaporizing during this heat exchange is expanded to perform work and is extracted as residual gas.
The cooling required for operation oftheair- fractionation plant is produced by the expansion of the residual gas. The nitrogen product is extracted from the top of the low-pressure stage of the rectification device, Although this process operates satisfactorily in itself, it has the disadvantage that, by exhausting the nitrogen under pressure, the subsequent secondary compression requires a relatively large amount of energy.
Hence, it is an object of the present invention to develop a process of the type described above but which enables the production of nitrogen at above atmospheric pressure and which has a low energy requirement.
According to the invention, in a process for prod
ucing pressurised nitrogen by two-stage rectification of air at low temperature, the air is compressed, prepurified, cooled in heat exchange with products of fractionation and fed to a rectification device, oxygen-enriched liquid is extracted from the sump of the low-pressure stage of the rectification device and
is at least partially vaporized, nitrogen is extracted from the top of the low-pressure stage, and at least a
portion of the oxygen-enriched liquid is vaporized in the top ofthe low-pressure stage ofthe device in heat
exchange with nitrogen which is condensing therein.
In contrasttothe process known hitherto, the
oxygen-enriched liquid is not vaporized against a component stream of the airto be fractionated, but is vaporized against (in heat exchange with) nitrogen in
an additional condenser-vaporized in the top ofthe low-pressure stage ofthe rectification device. The nitrogen condensing in the top ofthe low-pressure stage at the same time serves as a return-flow liquid for this column. The condenser-vaporizer in the top of the low-pressure stage is connected in series with the condenser-vaporizer which is conventionally used in two-stage rectification and which is located between the pressure stage and the low-pressure stage.
Since two condensers are provided in the process ofthe invention, that is to say, one between the two stages and one in the top ofthe low-pressure stage, a relatively high air pressure is necessary owing to the thermodynamic conditions during rectification.
Hence, the geometric dimensions of the components, such as a molecular sieve or scree station for the pre-purification of air, the heat exchangerfor cooling the air to be decomposed, the rectification column and the pipes, can be kept small, an advantage of considerable importance, particularly in the case of large airfractionation plant.
The additional condenser-vaporizer in the top of the low-pressure stage does not constitute any additional expenditure on apparatus, since it partially replaces the condenser-vaporizer between the two rectification stages and the latter may be of correspondinglysmallerconstruction.
In a preferred development of the process in accordance with the invention, the liquid is super-cooled and throttled before vaporization.
The pressure of the oxygen-enriched liquid must be reduced to an extent that the vaporization temperature at this pressure is below the condensation temperature of the nitrogen in the top ofthe lowpressure stage.
Ifthe airto be decomposed is pre-purified in molecular sieves or screens, the latter must be regenerated at certain intervals oftime. In a preferred development ofthe process in accordance with the invention, regeneration is effected bythevapour formed during the vaporization oftheoxygen- enriched liquid.
In this connection, it proves to be advantageous if, in accordance with a development ofthe process of the invention, the vapour is heated before it is used as regenerating gas.
In a preferred application of the process ofthe in- vention, gaseous nitrogen is extracted from the top of the pressure stage and is mixed with the nitrogen from the top of the low-pressure stage.
As result of vaporizing the oxygen-enriched liquid in thetop of the low-pressure stage, a smallerquan tity ofthis liquid isvapourized in the condenservaporizer between the two stages. This perm its the extraction of an equivalent quantity of nitrogen from the pressure stage. However, this quantity of nitrogen is not lost from the low-pressure stage as a return-flow liquid, since, in accordance with the invention, liquid nitrogen is produced as a return flow as a result ofthe vaporization of oxygen-enriched liquid in the low-pressure stage.
In a preferred development of the process ofthe invention, a portion of the air to be fractionated is compressed to higher pressure, cooled and expanded to perform work.
In a further preferred embodiment of the process of the invention, the airexpandedto perform work is expanded approximatelyto the pressure of the lowpressure stage and is fed to the latter.
Preferably, the energy obtained during the expansion ofthe air is used for compressing the air.
In a further preferred embodiment of the process ofthe invention, a stream of gas from the lowpressure stage is expanded to perform work, and all the air to be fractionated is fed to the pressure stage.
This mode of operation renders it possible to obtain pure oxygen as a product in addition to the nit rogen,theoxygen being extracted in liquid form from the sump ofthe low-pressure stage and being vaporized in the top ofthe low-pressure stage against (in heat exchange with) the nitrogen then condensing.
Advantageously, the stream of gas expanded to perform work is used to regenerate molecular sieves or screens forthe pre-purification of the air.
In apparatus for performing the process in accordance with the invention comprising a two-stage re ctifying column device which has afeed linefor cooled, pre-purified air, and extraction lines connected to the sump and to the top of the low-pressure stage, the extraction line connected to the sump of the low-pressure stage opens into the vaporizer end of a condenser-vapourizer in the top of the lowpressure stage.
The invention will now be further described byway of examples with referenceto embodiments illustrated diagrammatically in the accompanying drawings, in which Figure I shows a process in accordance with the invention, and
Figure2 shows a further embodiment of the process in accordance with the invention.
Referring to Figure 1,334700 Nm3ofairarefed by way ofa line 1 to an aircompressor2inwhich itis compressed to a pressure of approximately 9.3 bar.
Afterthe heat resulting from such compression has been dissipated in a cooler 3, the compressed air is conducted through a separator 4from which condensed water is led away th rough line 32.
The pre-dried air is fed through a line 5to a molecularsieve, two molecular sieving adsorbers 6 of which are shown. The airto be fractionated, and a regenerating gas, flow alternately through the two molecularadsorbers 6. Undesired constituents, particularly H2O and CO2 are separated from the air by the molecular sieve. The purified air (332 600 Nm3) is extracted from the molecular sieve byway of a line 7 and is split up into two component streams 8,9. The larger component stream 8 (approximately 295200 Nm3) is cooled in heat exchange with products of fractionation in a heat exchanger 33. Itstemperature thereby drops from approximately 293 Kto approximately 107 K.The cooled air is subsequently fed to the pressure stage 10 of a two-stage rectifying column which is operated at a pressure of approximately9.1 bar.
The second component stream 9 of the air to be decomposed (approximately 37400 Nm3) is compressed to approximately 11.7 bar in a booster 34 and, after dissipation of the heat resulting from such compression in an aftercooler 11, is conducted also at a temperature of 293 K into a further flow path of the heat exchanger33, where it is cooled to approximately 171 K in heat exchange with products of decomposition, and is extracted from the heat exchanger33 upstream of the cold end thereof. The component stream 9 is then expanded in an expansion device 12 to a pressure of approximately 4.6 bar to perform work, and cooled to approximately 137 K.
The expanded component stream is then fed to the low-pressure stage 13 of the rectifying column.
The rectifying column contains a condenservaporizer 14 between the pressure stage 10 and the low-pressure stage 13, and a further condenser vaporizer 15 in the top of the low-pressure stage.
Oxygen-enriched liquid is extracted from the sump ofthe pressure stage 10 byway of a line 16, and a liquid enriched with nitrogen is extracted from the top ofthe pressure stage 10 byway of a iine 17, and the liquids are cooled against nitrogen product in a heatexchanger 18,throttled,and conducted intothe low-pressure stage 13 at different points according to their compositions. A liquid enriched with oxygen (approximately 64.9% oxygen) is formed in the sump of the low-pressure stage 13 and is extracted by way of a line 19, super-cooled in a heat exchanger20, throttled to a pressure of approximately 1.4 bar in a valve 21, and is fed to the vaporizer end of the condenser-vaporizer 15 in the top of the low-pressure stage 13.A portion of the liquid enriched with oxygen vaporizes in heat exchange with nitrogen in the top of the low-pressure stage 13, and is thereby condensed and forms the return flow in the low-pressure stage required for rectification. The vaporous portion of the oxygen-rich liquid is extracted by way of a line 22 and is heated in the heat exchanger 20. It is subsequently mixed with an oxygen-enriched gas which is extracted from the low-pressure stage 13 by way of a line 23 and which isthrottle-expanded.Themixture is fed through a line24tothe heat exchanger 33 in which it is heated to approximately 290 Kin heat exchange with the air to be fractionated. The oxygenrich gas is heated if required (not illustrated and is used to regenerate the molecular sieves 6. Surplus gas is extracted by way of line 25.
Liquid enriched with oxygen if required may be extracted from the vaporizer end of the condenservaporizer 15 by way of a line 26.
Approximately 128640 Nm3 of pure nitrogen (oxygen purity 1 ppm) with a pressure of approximately 4.4 bar are obtained in the top of lowpressure stage 13. This nitrogen is extracted byway of a line 27, and is heated in the heat exchanger 18 and subsequently fed to the heat exchanger 33 in which it is heated to approximately 20 K. The heated nitrogen is compressed to a pressure of approximately 8.9 bar in a compressor 28 and is mixed with a further stream of nitrogen afterthe heat resulting from such compression has been dissipated in an aftercooler 29. The further stream of nitrogen is extracted from the top of the pressure stage 10 by way of line 30 at a pressure of approximately 9.0 bar and with an oxygen purity of 1 ppm. The quantity ofthe further stream of nitrogen is 94760 Nm3. This stream of nitrogen is heated to 290 K in the heat exchanger 33 and is subsequentlyfed tothe consuming device together with the stream of nitrogen from the compressor28. If the nitrogen is required ata higherpressure, it is compressed to the desired pressure of, for example, 77 bar in a compressor31.
The same reference numerals as used in Figure 1 are used for analogous components in the diagram ofthe alternative process diagrammatically illustrated in Figure 2.
In this embodiment, all the air to be decomposed is fed to the pressure stage 10. The stream of gas extracted from the low-pressure stage 13 byway ofthe line 23 is not mixed with the oxygen in the line 22, but is conducted through a partofthe heatexchanger33 and thereby heated, and is then expanded in a workperforming manner in an expansion device 34 and is finally heated to approximately the ambienttem- perature in the heat exchanger. The heated gas is used for the regeneration of the molecular sieves 6.
By extracting the quantity of residual gas by way of the line 23, it is possible to obtain pure oxygen (approximately 9.5% purity) in the low-pressure stage 13 in addition to the nitrogen product in the sump ofthe column.The liquid oxygen is extracted through the line 19 and is at least partiallyvaporized inthecon- denser-vaporizer 15. The substantially pressureless oxygen vapourthus formed is extracted by way of the line 22, heated in the heat exchangers 20,33, and is subsequently compressed in the booster compressor 34 connected to the expansion device 12.
The energy requirementforthe production of compressed nitrogen can be perceptibly reduced by the process in accordance with the invention. While the energy requirement for the production of nitrogen at 77 barwas approximately 0.27 kW/Nm3when using the known process, it is only approximately 0.25 kW/ Nm3 when using the process in accordance with the invention. This corresponds to a saving of energy of approximately 8%.
The process in accordance with the invention is generally suitable when the nitrogen is required at an increased pressure, for, for example, ammonia synthesis orforthe conditioning of natural gas.
Claims (13)
1. A process for producing pressurised nitrogen by two-stage rectification of air at low temperatures, in which the air is compressed, pre-purified, cooled in heat exchange with products of fractionating and fed to a rectification device, oxygen-enriched liquid is extracted from the sump ofthe low-pressure stage ofthe rectification device and is at least partially vaporised, nitrogen is extracted from the top ofthe low-pressure stage, and at least a portion of the oxygen-enriched liquid is vaporized in the top ofthe low-pressure stage of the device in heat exchange with nitrogen which is condensing therein.
2. A process as claimed in claim 1, wherein the oxygen-enriched liquid is supercooled and throttled before vaporization.
3. A process as claimed in claim 1 or2,wherein thevapourformed during vaporization ofthe oxygen-enriched liquid, is used for the regeneration ofmolecularsieves orscreensforthe pre
purification ofthe air.
4. A process as claimed in claim 3, wherein the
vapour is heated before it is used as a regenerating
gas.
5. A process as claimed in any one of claims 1 to
4, wherein gaseous nitrogen is extracted from the top
of the pressure stage ofthe rectification device and is
mixed with nitrogen from the top ofthe low-pressure
stage ofthe device.
6. A process as claimed in any one of claims 1 to 5, wherein a portion ofthe airto be fractionated is
compressed to an higher pressure, cooled, and ex
panded to perform work.
7. A process as claimed in claim 6, wherein the air
expanded to perform work is fed to the low-pressure stage of the rectification device.
8. A process as claimed in claim 6 or 7, wherein the energy obtained during expansion ofthe air is used to compress the air.
9. A process as claimed in claims 1 or 2, wherein the stream of gas from the low-pressure stage ofthe
rectification device is expanded to perform work, and all the air to be fractionated is fed to the pressure stage ofthe device.
10. A process as claimed in claim 9, wherein the stream of gas expanded to perform work is used for the regeneration of molecular sieves or screens for the pre-purification ofthe air.
11. Apparatus for performing the process as claimed in anyone of claims 1 to 10 having atwostage rectification column device which has a feed lineforcooled, pre-purified air, and extraction lines connected to the sump and to the top ofthe lowpressure stage, wherein the extraction line connected to the sump of the low-pressure stage of the device opens into the vaporizer end of a condenservaporizer in the top of the low-pressure stage.
12. Processes for producing pressurised nitrogen by two-stage rectification of air at lowtem peratures substantially as herein described with reference to the accompanying drawings.
13. Apparatus according to claim 11 forproduc ing pressurised nitrogen by two-stage rectification of air at low temperature substantially as herein described with reference to and as diagrammatically illustrated in the accompanying drawings.
13. Apparatus for producing pressurised nitrogen by two-stage rectification of air at low tem- peratures substantially as herein described with reference to and as diagrammatically illustrated in the accompanying drawings.
Amendments to the claims have been filed, and have the following effect: (a) Claims 11 and 13 above have been deleted or textually amended.
(b) Newortextuallyamended claims have been filed asfollows:
11. Apparatus when used in the process as claimed in any one of claims 1 to 10 having a twostage rectification column device which has a feed line for cooled, pre-purified air, and extraction lines connected to the sump and to thetop ofthe low- pressure stage, wherein the extraction line connected to the sump of the low-pressure stage of the device opens into the vaporizer end of a condenservaporizer in the top of the low-pressure stage.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19853528374 DE3528374A1 (en) | 1985-08-07 | 1985-08-07 | METHOD AND DEVICE FOR PRODUCING NITROGEN WITH OVER-ATMOSPHERIC PRESSURE |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8615737D0 GB8615737D0 (en) | 1986-08-06 |
| GB2180923A true GB2180923A (en) | 1987-04-08 |
Family
ID=6277956
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08615737A Withdrawn GB2180923A (en) | 1985-08-07 | 1986-06-30 | Process and apparatus for the production of pressurized nitrogen |
Country Status (3)
| Country | Link |
|---|---|
| DE (1) | DE3528374A1 (en) |
| GB (1) | GB2180923A (en) |
| NO (1) | NO863184L (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2190477A (en) * | 1986-05-14 | 1987-11-18 | Voest Alpine Ag | Production of oxygen by air separation |
| US4964901A (en) * | 1988-05-20 | 1990-10-23 | Linde Aktiengesellschaft | Low-temperature separation of air using high and low pressure air feedstreams |
| EP0877219A2 (en) * | 1997-04-29 | 1998-11-11 | Air Products And Chemicals, Inc. | Process to produce nitrogen using a double column and three reboiler/condensers |
| WO1999041557A1 (en) * | 1998-02-12 | 1999-08-19 | Shell Internationale Research Maatschappij B.V. | Air prepurification for a large scale cryogenic air separation plant |
| FR2874249A1 (en) * | 2004-08-10 | 2006-02-17 | Air Liquide | Air separation by cryogenic distillation using medium and low pressure columns, for production of oxygen and/or nitrogen, with residual stream extracted from low pressure column to maintain product purity |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4127224C2 (en) * | 1991-05-11 | 1997-09-18 | Foerster Hans Dr Ing | Process for refrigeration with air as a refrigerant and refrigerant |
| GB9213776D0 (en) * | 1992-06-29 | 1992-08-12 | Boc Group Plc | Air separation |
| DE4441920C1 (en) * | 1994-11-24 | 1996-04-04 | Linde Ag | Method and appliance for obtaining nitrogen by cryogenic separation of air |
| US5678425A (en) * | 1996-06-07 | 1997-10-21 | Air Products And Chemicals, Inc. | Method and apparatus for producing liquid products from air in various proportions |
| DE19735154A1 (en) * | 1996-10-30 | 1998-05-07 | Linde Ag | Producing compressed nitrogen@ by low temperature distillation of air in rectifier system |
| DK0878678T3 (en) * | 1997-05-15 | 2003-03-10 | Linde Ag | Method and apparatus for extracting nitrogen by low temperature fractionation of air |
| JPH11151415A (en) * | 1997-09-17 | 1999-06-08 | Taiyo Toyo Sanso Co Ltd | Production of ultra clean air and device therefor |
| DE19742319A1 (en) * | 1997-09-25 | 1999-04-08 | Zbigniew Dr Ing Boguslawski | Method of Compressed and liquefied nitrogen as a propulsion medium for vehicles |
| DE19819263C2 (en) * | 1998-04-30 | 2003-08-21 | Linde Ag | Process and device for the production of pressurized nitrogen |
| EP0955509B1 (en) * | 1998-04-30 | 2004-12-22 | Linde Aktiengesellschaft | Process and apparatus to produce high purity nitrogen |
| JP5005894B2 (en) | 2005-06-23 | 2012-08-22 | エア・ウォーター株式会社 | Nitrogen generation method and apparatus used therefor |
| TWI459999B (en) * | 2012-10-15 | 2014-11-11 | China Steel Corp | A device for injecting a shaft seal gas into a crude argon pump |
| CN109855389B (en) * | 2019-01-04 | 2020-11-13 | 曹建喜 | Method for producing liquid oxygen and liquid nitrogen by using LNG cold energy and single-tower rectification process |
| WO2021242308A1 (en) * | 2020-05-26 | 2021-12-02 | Praxair Technology, Inc. | Enhancements to a dual column nitrogen producing cryogenic air separation unit |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1215377A (en) * | 1968-01-18 | 1970-12-09 | Vnii Kislorodnogo I Kriogennog | Air rectification plant for the production of pure nitrogen |
| GB1576910A (en) * | 1978-05-12 | 1980-10-15 | Air Prod & Chem | Process and apparatus for producing gaseous nitrogen |
| US4448595A (en) * | 1982-12-02 | 1984-05-15 | Union Carbide Corporation | Split column multiple condenser-reboiler air separation process |
| GB2131148A (en) * | 1982-12-02 | 1984-06-13 | Union Carbide Corp | Dual column high pressure nitrogen process |
| GB2131147A (en) * | 1982-12-02 | 1984-06-13 | Union Carbide Corp | Double column multiple condenser-reboiler high pressure nitrogen process |
-
1985
- 1985-08-07 DE DE19853528374 patent/DE3528374A1/en not_active Withdrawn
-
1986
- 1986-06-30 GB GB08615737A patent/GB2180923A/en not_active Withdrawn
- 1986-08-06 NO NO863184A patent/NO863184L/en unknown
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1215377A (en) * | 1968-01-18 | 1970-12-09 | Vnii Kislorodnogo I Kriogennog | Air rectification plant for the production of pure nitrogen |
| GB1576910A (en) * | 1978-05-12 | 1980-10-15 | Air Prod & Chem | Process and apparatus for producing gaseous nitrogen |
| US4448595A (en) * | 1982-12-02 | 1984-05-15 | Union Carbide Corporation | Split column multiple condenser-reboiler air separation process |
| GB2131148A (en) * | 1982-12-02 | 1984-06-13 | Union Carbide Corp | Dual column high pressure nitrogen process |
| GB2131147A (en) * | 1982-12-02 | 1984-06-13 | Union Carbide Corp | Double column multiple condenser-reboiler high pressure nitrogen process |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2190477A (en) * | 1986-05-14 | 1987-11-18 | Voest Alpine Ag | Production of oxygen by air separation |
| GB2190477B (en) * | 1986-05-14 | 1990-09-26 | Voest Alpine Ag | Process and apparatus for the production of oxygen by cyrogenic rectrification of air |
| US4964901A (en) * | 1988-05-20 | 1990-10-23 | Linde Aktiengesellschaft | Low-temperature separation of air using high and low pressure air feedstreams |
| EP0877219A2 (en) * | 1997-04-29 | 1998-11-11 | Air Products And Chemicals, Inc. | Process to produce nitrogen using a double column and three reboiler/condensers |
| EP0877219A3 (en) * | 1997-04-29 | 1999-02-10 | Air Products And Chemicals, Inc. | Process to produce nitrogen using a double column and three reboiler/condensers |
| WO1999041557A1 (en) * | 1998-02-12 | 1999-08-19 | Shell Internationale Research Maatschappij B.V. | Air prepurification for a large scale cryogenic air separation plant |
| FR2874249A1 (en) * | 2004-08-10 | 2006-02-17 | Air Liquide | Air separation by cryogenic distillation using medium and low pressure columns, for production of oxygen and/or nitrogen, with residual stream extracted from low pressure column to maintain product purity |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3528374A1 (en) | 1987-02-12 |
| NO863184D0 (en) | 1986-08-06 |
| NO863184L (en) | 1987-02-09 |
| GB8615737D0 (en) | 1986-08-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |