CN111609668A - Low-temperature air separation method for air separation equipment - Google Patents

Low-temperature air separation method for air separation equipment Download PDF

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Publication number
CN111609668A
CN111609668A CN202010431151.8A CN202010431151A CN111609668A CN 111609668 A CN111609668 A CN 111609668A CN 202010431151 A CN202010431151 A CN 202010431151A CN 111609668 A CN111609668 A CN 111609668A
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air
tower
air flow
argon
molecular sieve
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周占盈
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Qidong Kelan Mechanical And Electrical Equipment Co Ltd
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Qidong Kelan Mechanical And Electrical Equipment Co Ltd
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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
    • 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
    • F25J3/04242—Cold end purification of the feed air
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/54—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms
    • B01D46/543—Particle separators, e.g. dust precipitators, using ultra-fine filter sheets or diaphragms using membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/56—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with multiple filtering elements, characterised by their mutual disposition
    • B01D46/62—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours with multiple filtering elements, characterised by their mutual disposition connected in series
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/26—Drying gases or vapours
    • B01D53/261—Drying gases or vapours by adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/26—Drying gases or vapours
    • B01D53/28—Selection of materials for use as drying agents
    • 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
    • F25J3/04624—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 integrated mass and heat exchange, so-called non-adiabatic rectification, e.g. dephlegmator, reflux exchanger
    • F25J3/0463—Simultaneously between rectifying and stripping sections, i.e. double dephlegmator
    • 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
    • F25J3/04636—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 hybrid air separation unit, e.g. combined process by cryogenic separation and non-cryogenic separation techniques
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
    • B01D2253/10—Inorganic adsorbents
    • B01D2253/106—Silica or silicates
    • B01D2253/108—Zeolites
    • 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
    • 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
    • F25J2200/32—Processes or apparatus using separation by rectification using a side column fed by a stream from the 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
    • F25J2200/00—Processes or apparatus using separation by rectification
    • F25J2200/34—Processes or apparatus using separation by rectification using a side column fed by a stream from the low 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/60—Processes or apparatus using other separation and/or other processing means using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end
    • F25J2205/64—Processes or apparatus using other separation and/or other processing means using adsorption on solid adsorbents, e.g. by temperature-swing adsorption [TSA] at the hot or cold end by pressure-swing adsorption [PSA] at the hot end
    • 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
    • F25J2215/42—Nitrogen or special cases, e.g. multiple or low purity N2
    • F25J2215/44—Ultra high purity nitrogen, i.e. generally less than 1 ppb impurities
    • 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
    • F25J2215/56—Ultra high purity oxygen, i.e. generally more than 99,9% O2

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Separation By Low-Temperature Treatments (AREA)

Abstract

The invention discloses a method for separating air at low temperature by air separation equipment, which comprises the steps of firstly leading air into a compressor after sequentially passing through a plurality of layers of filtering membranes with different apertures, then circularly cooling the compressed air by utilizing multi-section circulating cooling water in a condensing tower, then symmetrically arranging two groups of molecular sieve adsorbers at an outlet of the condensing tower, purifying the cooled air, dividing the air into a first air flow and a second air flow after heat exchange by a first heat exchanger, respectively leading the first air flow and the second air flow into lower tower bottoms of a two-stage rectifying tower after respectively leading the first air flow and the second air flow into different pressure reduction equipment for pressure reduction, rectifying by utilizing the heat transfer temperature difference of upper and lower towers of the two-stage rectifying tower, recovering by argon synergy, simultaneously extracting gas at the upper part of the upper tower, leading fractions in the lower tower into a device for argon synergy, and carrying out adsorption separation on the fractions by utilizing a group of the molecular sieve adsorbers, the purity of the prepared separation product is improved.

Description

Low-temperature air separation method for air separation equipment
Technical Field
The invention relates to the technical field of low-temperature air separation, in particular to a low-temperature air separation method for air separation equipment.
Background
Atmospheric air contains many different gaseous components, primarily nitrogen and oxygen, but also small amounts of other substances, such as noble gases (e.g. argon), methane, water vapor and carbon dioxide. One or more components of atmospheric air may be separated using air separation methods and systems and provided in purified form. There are known techniques for air separation processes such as cryogenic distillation (e.g., cryogenic air separation cycles), membrane separation, Pressure Swing Adsorption (PSA), and Vacuum Pressure Swing Adsorption (VPSA), as well as the separation of oxygen from air in high temperature oxygen ion transport ceramic mixed oxide membrane systems. Among the available methods, cryogenic distillation is particularly advantageous for separating air into high purity and high pressure components, but the purity of the separated products obtained after cryogenic distillation is not high at present.
Disclosure of Invention
The invention aims to provide a method for separating air at low temperature by using air separation equipment, which improves the purity of a separation product prepared by low-temperature distillation.
To achieve the above object, the present invention provides a method for low-temperature separation of air in an air separation plant, comprising:
after being compressed, the air is introduced into a condensing tower for cooling;
purifying air by using two groups of molecular sieve adsorbers;
dividing the purified air into two parts, depressurizing, and introducing into the bottom of the lower tower of the two-stage rectifying tower;
and (3) rectifying by utilizing the heat transfer temperature difference of the upper tower and the lower tower of the double-stage rectifying tower, and recovering by argon synergism.
Wherein the method further comprises:
and sequentially passing air through a plurality of layers of filtering membranes with different pore diameters and then introducing the air into a compressor, wherein the pore diameters of the plurality of layers of filtering membranes are gradually reduced towards the compressor.
Wherein, after compressing the air, leading into the condensing tower and cooling, include:
and after the filtered air is compressed by a compressor, circularly cooling the air to be less than 20 ℃ by utilizing multiple sections of circulating cooling water in a condensing tower.
Wherein, utilize two sets of molecular sieve adsorbers to purify the air, include:
after being connected in parallel two by two, the four molecular sieves are symmetrically arranged at the outlet of the condensation tower as two groups of molecular sieve adsorbers, and the molecular sieves in each group of molecular sieve adsorbers respectively carry out adsorption and regeneration.
Wherein, divide into two parts with the air after the purification and reduce pressure to leading to the lower bottom of doublestage rectifying column, include:
the method comprises the steps of dividing purified air into a first air flow and a second air flow after heat exchange of a first heat exchanger, respectively introducing the first air flow and the second air flow into different pressure reduction equipment for pressure reduction, and introducing the first air flow and the second air flow into the bottom of a lower tower of a double-stage rectifying tower.
Wherein directing the first air stream into a pressure reducing device for pressure reduction comprises:
and dividing one third of the air subjected to heat exchange into first air flow, performing heat exchange by using liquid nitrogen through a second heat exchanger, reducing the pressure by using a throttle valve, and adjusting the temperature to 103K.
Wherein directing the second air stream into a pressure reducing device for pressure reduction comprises:
and dividing two thirds of air after heat exchange into a second air flow, introducing the second air flow into an expansion machine for isentropic expansion, and reducing the temperature to 103K.
Wherein, utilize the heat transfer difference in temperature of upper and lower tower of doublestage rectifying column to carry out the rectification to retrieve through the argon increase, include:
and according to the pressure difference between the upper tower and the lower tower in the double-stage rectifying tower, the condensing evaporator has heat transfer temperature difference corresponding to the pressure difference, and the compressed air is rectified from the lower tower to the upper tower.
Wherein, utilize the heat transfer difference in temperature of upper and lower tower of doublestage rectifying column carries out the rectification to retrieve through the argon increase, still include:
and after extracting the gas at the upper part of the upper tower, respectively introducing the fractions in the upper tower and the lower tower into an argon synergistic device for recycling.
Wherein the method further comprises:
and before the fraction in the lower tower is introduced into the argon synergy device, carrying out adsorption separation on the fraction by using a group of molecular sieve adsorbers.
The invention relates to a method for separating air at low temperature by air separation equipment, which comprises the steps of firstly leading air into a compressor after sequentially passing through a plurality of layers of filtering membranes with different apertures, then circularly cooling the compressed air to be less than 20 ℃ by utilizing multi-section circulating cooling water in a condensation tower, then connecting four molecular sieves in parallel in pairs, symmetrically arranging the four molecular sieves at an outlet of the condensation tower as two groups of molecular sieve adsorbers, purifying the cooled air, dividing the air into a first air flow and a second air flow after heat exchange by a first heat exchanger, respectively leading the first air flow and the second air flow into different pressure reduction equipment for pressure reduction, leading the first air flow and the second air flow into the bottom of a lower tower of a two-stage rectification tower, rectifying by utilizing the heat transfer synergistic temperature difference of the upper tower and the lower tower of the two-stage rectification tower, recovering by argon, simultaneously extracting the gas at the upper part of the upper tower, and leading fractions in the lower tower, and carrying out adsorption separation on the fractions by utilizing a group of molecular sieve adsorbers, and improving the purity of a separation product prepared by low-temperature distillation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a process for the cryogenic separation of air in an air separation plant in accordance with the present invention.
FIG. 2 is a schematic diagram of an air separation plant according to the present invention.
The system comprises a 1-filtering membrane, a 2-compressor, a 3-condensing tower, a 4-molecular sieve adsorber, a 5-first heat exchanger, a 6-second heat exchanger, a 7-throttling valve, an 8-expansion machine, a 9-double-stage rectifying tower and a 10-argon synergistic device.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
Referring to fig. 1, the present invention provides a method for low-temperature air separation in an air separation plant, comprising:
s101, compressing the air, and then introducing the compressed air into a condensing tower 3 for cooling.
Specifically, the air sequentially passes through the multi-layer filtering membranes 1 with different apertures and then is led into the compressor 2, dust, impurities and the like in the air are filtered, the purity of a product obtained by fractionation is guaranteed, wherein the apertures of the multi-layer filtering membranes 1 are gradually decreased towards the position close to the compressor 2, the filtering membranes 1 are composed of honeycomb-shaped filter elements, the apertures of the filter elements are changed along with the diameters of the filtering membranes 1, impurities with smaller diameters can be gradually filtered, the purity is further guaranteed, then the filtered air is compressed by the compressor 2 to obtain air with a pressure value of at least 3 bar and a temperature of more than 150 ℃, and finally, the air is circularly cooled to be less than 20 ℃ by utilizing multiple sections of circulating cooling water in the condensing tower 3, specifically, the air is circularly cooled by utilizing upper-section circulating refrigeration water and lower-section circulating cooling water in the condensing tower 3, at the bottom of condensing tower 3, the temperature of recirculated cooling water reduces gradually, carries out the first cooling to the air after the compression, then along with the rising of air, the air quilt upper segment circulation refrigerated water further cools off, and is repeated going on, makes compressed air furthest's cooling, the convenience is to the subsequent processing of air.
S102, purifying the air by using two groups of molecular sieve adsorbers 4.
Specifically, after being connected in parallel two by two, four molecular sieves are symmetrically arranged between the outlet of the condensing tower 3 and the first heat exchanger 5 as two groups of molecular sieve adsorbers 4, and by utilizing the adsorption capacity of the molecular sieves, water vapor, carbon dioxide and hydrocarbon in the air at the outlet of the condensing tower 3 can be adsorbed, and the molecular sieves in each group of molecular sieve adsorbers 4 are respectively subjected to adsorption and regeneration work, namely, two molecular sieves, one molecular sieve is subjected to adsorption work, the other molecular sieve is subjected to regeneration work, and the regeneration work can be divided into four steps: pressure relief, heating, cold blow and pressurize, it is right after can utilizing the nitrogen gas that the fractionation obtained to advance the superheating the molecular sieve regenerates, later cold blow the molecular sieve that regeneration was ended with nitrogen gas, makes the nitrogen gas that makes can make full use of, reduce cost, because two the molecular sieve can not adsorb simultaneously, in order to guarantee the adsorption effect maximize, consequently utilize two sets of molecular sieve adsorbers 4 symmetry set up in 3 export both sides of condensing tower guarantee the molecular sieve adsorber 4 of 3 both sides of condensing tower can all be normal carry out the adsorption, can improve and carry out the adsorption efficiency to vapor, carbon dioxide, hydrocarbon in the air, further guarantee the purity of fractionation product.
And S103, dividing the purified air into two parts, reducing the pressure, and introducing the two parts into the bottom of the lower tower of the double-stage rectifying tower 9.
Specifically, divide into first air current and second air current after the air after will purifying through the heat transfer of first heat exchanger 5, wherein, to utilizing when first heat exchanger 5 carries out the heat exchange, also can utilize the liquid nitrogen that follow-up fractionation made to cool off the air, further improve the utilization ratio of fractionating the product, practice thrift the cost, then direct-in different step-down equipment respectively and step down, specifically do: dividing one third of the air after heat exchange into first air flow, performing heat exchange by using liquid nitrogen through a second heat exchanger 6, reducing the temperature, and adjusting the temperature to 103K (Kelvin) by using a throttle valve 7; and dividing two thirds of air after heat exchange into a second air flow, introducing the second air flow into an expansion machine 8 for isentropic expansion, and reducing the temperature to 103K. The first air flow and the second air flow are introduced to the bottom of the lower tower of the double-stage rectifying tower 9, when the expansion machine 8 is used for carrying out isentropic expansion on gas, the temperature is reduced more than that of the throttle valve 7, a part of compression work can be recovered, and the energy consumption of equipment can be reduced, so that the equipment is more economical and practical than the step-down by using the throttle valve 7, most of gas in the purified air is reduced in pressure by using the isentropic expansion, the pressure reduction effect is ensured, and the cost is saved.
And S104, rectifying by utilizing the heat transfer temperature difference of the upper tower and the lower tower of the double-stage rectifying tower 9, and recovering by argon synergism.
Specifically, as shown in the schematic structural diagram of the air separation apparatus provided in fig. 2, the dual-stage rectification column 9 includes an upper column, a lower column and a condensation evaporator, when the first air stream and the second air stream enter the lower column, they are liquefied, and since liquid nitrogen has a lower boiling point than liquid oxygen, most of the bottom of the lower column is oxygen-enriched liquid air, and the oxygen content is generally 30% to 40%, according to the pressure difference between the upper column and the lower column in the dual-stage rectification column 9, the pressure of the lower column is greater than the pressure of the upper column, and further the temperature of the upper column is greater than the temperature of the lower column, so that the condensation evaporator has a heat transfer temperature difference corresponding to the pressure difference, so that heat is transferred from the inside of the tube to the outside of the tube, thereby cooling the lower column and heating the upper column, and air is rectified from the lower column to the upper column, so that the concentration of nitrogen having a low boiling point is gradually increased in the upper column, condensing into liquid nitrogen in the condensing evaporator, wherein a part of the liquid nitrogen can be used as cooling liquid of the second heat exchanger 6 and for regenerating the molecular sieve, while the oxygen-enriched gas at the bottom of the lower tower is accumulated between the tubes of the condensing evaporator, the oxygen content can reach more than 99%, the content of the separated product is improved, but the purity of the liquid nitrogen and the liquid oxygen is not very high because inert gas exists in the air, so that argon with the boiling point between nitrogen and oxygen is extracted in the middle of the upper tower, helium and neon with the boiling point lower than that of the nitrogen are extracted above the liquid nitrogen, krypton and xenon with the boiling point higher than that of the liquid oxygen and gaseous oxygen accumulated at the bottom of the upper tower are extracted, and the extracted argon, helium, neon, krypton and xenon can be respectively used for preparing raw materials of argon, helium, neon, krypton and xenon, the utilization rate of energy sources is increased, in order to ensure the accuracy of the extracted gas, the corresponding temperature can be measured at the extraction position and then the extraction is carried out, can further ensure the accuracy of the extracted gas and the purity of the product obtained by fractionation, then the fractions in the upper tower and the lower tower are respectively led into an argon synergistic device 10 for recycling, thereby reducing the energy consumption, improving the separation efficiency, and the argon in the argon synergy device 10 can be prepared by utilizing the extracted argon, thereby further saving the cost, improving the utilization rate of fractionation products, and before the liquid oxygen in the lower tower is led into the argon synergy device 10, according to different adsorption capacities of nitrogen and oxygen, one or two groups of molecular sieve adsorbers 4 are used for carrying out adsorption separation on the fractions, nitrogen in the liquid oxygen is adsorbed, and the purity of the prepared separation product is further improved.
The invention relates to a method for separating air at low temperature by air separation equipment, which comprises the steps of firstly leading air into a compressor 2 after sequentially passing through a plurality of layers of filtering membranes 1 with different apertures, then circularly cooling the compressed air to be less than 20 ℃ by utilizing multi-section circulating cooling water in a condensing tower 3, then connecting four molecular sieves in parallel in pairs, symmetrically arranging the four molecular sieves at an outlet of the condensing tower 3 as two groups of molecular sieve adsorbers 4, purifying the cooled air, dividing the air into a first air flow and a second air flow after heat exchange by a first heat exchanger 5, respectively leading the first air flow and the second air flow into different pressure reduction equipment for pressure reduction, leading the first air flow and the second air flow into the bottom of a lower tower of a two-stage rectifying tower 9, rectifying by utilizing the heat transfer temperature difference of the upper tower and the lower tower of the two-stage rectifying tower 9, recovering the air by argon, and simultaneously extracting the, and before the fraction in the lower tower is led into the argon synergy device 10, a group of molecular sieve adsorbers 4 are used for carrying out adsorption separation on the fraction, so that the purity of a separation product prepared after low-temperature distillation is improved.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. A method of cryogenically separating air in an air separation plant, comprising:
after being compressed, the air is introduced into a condensing tower for cooling;
purifying air by using two groups of molecular sieve adsorbers;
dividing the purified air into two parts, depressurizing, and introducing into the bottom of the lower tower of the two-stage rectifying tower;
and (3) rectifying by utilizing the heat transfer temperature difference of the upper tower and the lower tower of the double-stage rectifying tower, and recovering by argon synergism.
2. A method of cryogenically separating air in an air separation plant according to claim 1 wherein the method further comprises:
and sequentially passing air through a plurality of layers of filtering membranes with different pore diameters and then introducing the air into a compressor, wherein the pore diameters of the plurality of layers of filtering membranes are gradually reduced towards the compressor.
3. The method of claim 1, wherein compressing the air prior to introduction into the condensing tower for cooling comprises:
and after the filtered air is compressed by a compressor, circularly cooling the air to be less than 20 ℃ by utilizing multiple sections of circulating cooling water in a condensing tower.
4. The method of claim 3, wherein the purifying the air using two sets of molecular sieve adsorbers comprises:
after being connected in parallel two by two, the four molecular sieves are symmetrically arranged at the outlet of the condensation tower as two groups of molecular sieve adsorbers, and the molecular sieves in each group of molecular sieve adsorbers respectively carry out adsorption and regeneration.
5. The method of claim 4, wherein said dividing the purified air into two portions for depressurization and introduction into the bottom of the lower column of the two-stage rectification column comprises:
the method comprises the steps of dividing purified air into a first air flow and a second air flow after heat exchange of a first heat exchanger, respectively introducing the first air flow and the second air flow into different pressure reduction equipment for pressure reduction, and introducing the first air flow and the second air flow into the bottom of a lower tower of a double-stage rectifying tower.
6. The method of claim 5, wherein directing the first air stream into a pressure reduction device for pressure reduction comprises:
and dividing one third of the air subjected to heat exchange into first air flow, performing heat exchange by using liquid nitrogen through a second heat exchanger, reducing the pressure by using a throttle valve, and adjusting the temperature to 103K.
7. The method of claim 5, wherein directing the second air stream into a pressure reduction device for pressure reduction comprises:
and dividing two thirds of air after heat exchange into a second air flow, introducing the second air flow into an expansion machine for isentropic expansion, and reducing the temperature to 103K.
8. The method of claim 5, wherein the rectification by the heat transfer temperature difference between the upper and lower columns of the double-stage rectification column and the recovery by argon synergy comprises:
and according to the pressure difference between the upper tower and the lower tower in the double-stage rectifying tower, the condensing evaporator has heat transfer temperature difference corresponding to the pressure difference, and the compressed air is rectified from the lower tower to the upper tower.
9. The method of claim 8, wherein the air is rectified by the difference in heat transfer temperature between the upper and lower columns of the dual-stage rectification column and recovered by argon enhancement, and further comprising:
and after extracting the gas at the upper part of the upper tower, respectively introducing the fractions in the upper tower and the lower tower into an argon synergistic device for recycling.
10. The method of claim 9 for the cryogenic separation of air in an air separation plant, the method further comprising:
and before the fraction in the lower tower is introduced into the argon synergy device, carrying out adsorption separation on the fraction by using a group of molecular sieve adsorbers.
CN202010431151.8A 2020-05-20 2020-05-20 Low-temperature air separation method for air separation equipment Pending CN111609668A (en)

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