EP3682178A1 - Process for utilizing of multi stage compressors intercoolers blowdown as a coolant for process air - Google Patents

Process for utilizing of multi stage compressors intercoolers blowdown as a coolant for process air

Info

Publication number
EP3682178A1
EP3682178A1 EP18759398.3A EP18759398A EP3682178A1 EP 3682178 A1 EP3682178 A1 EP 3682178A1 EP 18759398 A EP18759398 A EP 18759398A EP 3682178 A1 EP3682178 A1 EP 3682178A1
Authority
EP
European Patent Office
Prior art keywords
air
cooling
cooling medium
intercoolers
blowdown
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.)
Withdrawn
Application number
EP18759398.3A
Other languages
German (de)
French (fr)
Inventor
Hamad Mohammed MUDIJ
Nayef Nazzal AL HUSSAINI
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.)
SABIC Global Technologies BV
Original Assignee
SABIC Global Technologies BV
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
Publication date
Application filed by SABIC Global Technologies BV filed Critical SABIC Global Technologies BV
Publication of EP3682178A1 publication Critical patent/EP3682178A1/en
Withdrawn legal-status Critical Current

Links

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
    • F25J3/04406—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
    • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
    • F25J3/04012—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling
    • F25J3/04018—Providing pressurised feed air or process streams within or from the air fractionation unit by compression of warm gaseous streams; details of intake or interstage cooling of main feed air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/58—Cooling; Heating; Diminishing heat transfer
    • F04D29/582—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps
    • F04D29/5826—Cooling at least part of the working fluid in a heat exchanger
    • F04D29/5833—Cooling at least part of the working fluid in a heat exchanger flow schemes and regulation thereto
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/58—Cooling; Heating; Diminishing heat transfer
    • F04D29/582—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps
    • F04D29/5846—Cooling; Heating; Diminishing heat transfer specially adapted for elastic fluid pumps cooling by injection
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/0002—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the fluid to be liquefied
    • F25J1/0012—Primary atmospheric gases, e.g. air
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/02—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process
    • 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
    • F25J3/06—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation
    • F25J3/063—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by partial condensation characterised by the separated product stream
    • 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
    • F25J2205/00—Processes or apparatus using other separation and/or other processing means
    • F25J2205/02—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum
    • F25J2205/04—Processes or apparatus using other separation and/or other processing means using simple phase separation in a vessel or drum in the feed line, i.e. upstream of the fractionation step
    • 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
    • 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
    • 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
    • F25J2215/58—Argon
    • 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
    • F25J2230/02—Compressor intake arrangement, e.g. filtering or cooling
    • 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
    • F25J2230/04—Compressor cooling arrangement, e.g. inter- or after-stage cooling or condensate removal
    • 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
    • F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream

Definitions

  • the present invention generally relates to air compression processes. More specifically, the present invention relates to an air compression process that uses water blowdown from intercoolers of a multistage compressor as a cooling medium to cool the air feeding into the multistage compressor.
  • Atmospheric air is generally processed in an air separation plant to produce nitrogen, oxygen, argon and other inert gases. These products separated from air are utilized in many industries including chemical industry, medical industry, and semiconductor industry.
  • atmospheric air is first cleaned via filters to remove dust suspended in the air. Clean atmospheric air is subsequently compressed by an air compressor unit. In the compression process, clean air is compressed and cooled by a series of air compressors and intercoolers. Water fraction from the clean air is condensed in intercoolers and separated from the air. After trace water is further removed from the compressed air via molecular sieve, a heat exchanger is generally used to liquefy at least part of the compressed air, to form purified oxygen. The remaining gas is further distilled in a high pressure column and a low pressure column to produce purified nitrogen and purified argon. [0005] However, the conventional air separation process is highly energy intensive.
  • the method provides a solution for the above mentioned problems associated with air separation process.
  • the solution resides in a method of processing air prior to separating the components of the air.
  • the atmospheric air feeding into the compressor becomes denser and the temperature of the atmospheric air can be reduced. This can be beneficial for reducing the energy consumption of the multistage compressor as the volume of the air is reduced when it is cooled, thereby lowering the power required to compress the air.
  • the cooling process of the atmospheric air can be performed using the blowdown water collected from the intercoolers of the multistage compressor as the cooling medium, thus avoiding additional costs for cooling medium.
  • the blowdown water from each of the intercoolers of the multistage compressor can be collected in a storage tank and used to spray and mix in the atmospheric air, via a water sprinkler and/or water mister, thereby cooling the atmospheric air.
  • the energy required by the method to compress the atmospheric air can be reduced compared to using the currently available method.
  • Embodiments of the invention include a method of processing air prior to separating components of the air.
  • the method comprises cooling the air with a cooling medium to produce cooled air.
  • the method may further include compressing the cooled air in a compressor unit that comprises one or more compressors and one or more intercoolers.
  • the method includes collecting water blowdown from the one or more intercoolers, wherein the water blowdown is used as the cooling medium.
  • Embodiments of the invention include a method of processing air prior to separating components of the air.
  • the method includes cooling the air with a cooling medium to produce cooled air.
  • the method may further include compressing the cooled air in a multistage compressor unit.
  • the multistage compressor unit comprises at least two compressors for two compression stages and at least one intercooler for cooling compressed air from the at least two compressors.
  • the method further includes collecting water blowdown from the at least one intercooler of the multistage compressor unit. In this method, the water blowdown is used as the cooling medium.
  • Embodiments of the invention include a method of processing air prior to separating components of the air. The method includes measuring humidity and temperature of the air.
  • the air is cooled by a cooling medium if humidity of the air exceeds a predetermined humidity value and temperature of the air exceeds a predetermined temperature value.
  • the method further includes compressing the cooled air in a multistage compressor unit.
  • the multistage compressor unit includes at least three compressors for three compression stages and at least two intercoolers. Still further, the method includes collecting water blowdown from at least one of the intercoolers of the multistage compressor unit. The water blowdown is used as the cooling medium.
  • wt.% refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component.
  • substantially and its variations are defined to include ranges within
  • Embodiment 1 is a method of processing air prior to separating components of the air.
  • the method includes the steps of cooling the air with a cooling medium to produce cooled air; compressing the cooled air in a compressor unit that comprises one or more compression stages and one or more intercoolers to produce compressed process air; and collecting water blowdown from the one or more intercoolers, wherein the water blowdown is used as the cooling medium.
  • Embodiment 2 is the method of embodiment 1, wherein the compressor unit is a multi-stage compressor unit.
  • Embodiment 3 is the method of embodiment 2, wherein the multi-stage compressor unit includes at least two compression stages and at least one intercooler for cooling compressed air from the at least two compression stages.
  • Embodiment 4 is the method of any of embodiments 2 and 3, wherein the multi-stage compressor unit includes at least three compression stages in series and at least two intercoolers for cooling compressed air from the at least three compression stages.
  • Embodiment 5 is the method of any of embodiments 1 to 4, further including a step, before the cooling, of measuring humidity and temperature of the air, wherein the step of cooling the air with a cooling medium is performed in response to the humidity of the air greater than a predetermined humidity value and temperature of the air greater than a predetermined temperature value.
  • Embodiment 6 is the method of embodiment 5, wherein the predetermined humidity value include a humidity ratio of 8.42> ⁇ 10 "3 .
  • Embodiment 7 is the method of any of embodiments 5 and 6, wherein the predetermined temperature value is about 15°C.
  • Embodiment 8 is the method of any of embodiments 1 to 7, wherein the water blowdown is used as the cooling medium at an air to cooling medium ratio of 37: 1 to 1000: 1.
  • Embodiment 9 is the method of any of embodiments 1 to 8, wherein the water blowdown directly contacts the air in the cooling step.
  • Embodiment 10 is the method of any of embodiments 1 to 9, wherein cooling the air with a cooling medium is performed by spraying the air with the cooling medium and mixing the air with the cooling medium.
  • Embodiment 11 is the method of any of embodiments 1 to 10, wherein the water blowdown is collected and stored in a storage tank.
  • Embodiment 12 is the method of any of embodiments 1 to 11, wherein the cooled air has a temperature in a range of 15 to 30°C.
  • Embodiment 13 is the method of any of embodiments 1 to 12, wherein the cooled air has a density in a range of 1.05> ⁇ 10 "3 to 1.25x 10 " 3 g/cm 3 .
  • Embodiment 14 is the method of any of embodiments 1 to 13, wherein the intercooler includes a heat exchanger.
  • Embodiment 15 is the method of any of embodiments 1 to 14, wherein the cooling medium has a temperature of 10 to 35°C.
  • Embodiment 16 is the method of any of embodiments 1 to 15, wherein the compressed process air is at a pressure of 0.54 to 0.59 MPa.
  • Embodiment 17 is the method of any of embodiments 1 to 16, wherein the compressed process air is gaseous.
  • Embodiment 18 is the method of any of embodiments 1 to 17, wherein the compressed process air is sent to a cryogenic separation unit and separated into one or more of nitrogen, oxygen, and argon.
  • Embodiment 19 is a method of processing air prior to separating components of the air.
  • the method includes the steps of measuring humidity and temperature of the air; if humidity of the air exceeds a predetermined humidity value and temperature of the air exceeds a predetermined temperature value, cooling the air with a cooling medium to produce cooled air; compressing the cooled air in a multi-stage compressor unit, the multi-stage compressor unit including at least three compression stages and at least two intercoolers; and collecting water blowdown from at least one of the intercoolers of the multi-stage compressor unit, wherein the water blowdown is used as the cooling medium.
  • FIG. 1 shows a schematic diagram of an air compression system, according to embodiments of the invention
  • FIG. 2 shows a schematic flow chart of a method of compressing air, according to embodiments of the invention
  • FIG. 3 shows results of sensitivity analysis based on simulation runs on a method of compressing air, according to embodiments of the invention.
  • the currently available method of compressing atmospheric air includes directly compressing atmospheric (or cleaned atmospheric) air by a multistage compressor. This is highly energy intensive especially when the temperature of the atmospheric air is elevated, and the volume of atmospheric air is expanded.
  • the present invention provides a solution to this problem.
  • the solution is premised on a method of compressing atmospheric air that includes a step of cooling the atmospheric air feeding into a multistage compressor prior to flowing the air into the multistage compressor. Therefore, the volume of the atmospheric air can be reduced, decreasing the power required to compress the air.
  • the cooling medium used in the cooling step can be at least some of the blowdown water collected from the intercooler of the multistage compressor, thereby recycling the water in the atmospheric air and saving costs for cooling medium.
  • the humidity level in the atmospheric air may be sufficient to provide all the cooling medium needed in the method of the present invention.
  • An air compression system can be part of cryogenic air separation unit, providing compressed air for the subsequent cryogenic air separation processes.
  • atmospheric air or filtered atmospheric air is directly fed into the inlet of a multistage compressor.
  • the volume of the air can be expanded when the outdoor temperature is elevated.
  • atmospheric air can be highly expanded in the summer when the ambient temperature is greater than 35 °C, or even greater than 40 °C. This may escalate the power load of the existing air compressor system, further increasing the operating costs for the overall air separation process.
  • the present invention provides a system that can cool down the atmospheric air prior to the inlet of the multistage air compressor, thereby reducing the power load of the air compressor.
  • the present invention requires minimal capital expenditure and substantially no additional operating cost to facilitate the cooling of the atmospheric air prior to the multistage compression.
  • the air compression system of the present invention uses water blowdown collected from the intercoolers of the multistage air compressor as cooling medium for the atmospheric air, avoiding need of any other coolants.
  • the water blowdown can be simply sprayed and mixed into the atmospheric air via a water sprinkler or water mister, thereby requiring minimal costs for equipment or instruments.
  • FIG. 1 a schematic diagram shows air compression system
  • air compression system 100 may include air cooler 101 adapted to receive and cool down atmospheric air.
  • air cooler 101 may be a spray water cooler.
  • the spray water cooler may include a water sprinkler or a water mister adapted to mix water with atmospheric air.
  • An outlet of air cooler 101 may be in fluid communication with an inlet of a multistage air compressor unit.
  • the multistage air compressor unit may include one or more compressors and one or more intercoolers.
  • the multistage air compressor unit can include at least two compressors (two compression stages) and at least one intercooler for cooling compressed air from a first stage compressor.
  • the at least two compressors are installed in series.
  • An intercooler may be installed between two adjacent compressor stages.
  • Non- limiting examples of the intercooler include a heat exchanger with various cooling media such as cooling water or other cooled media.
  • the multistage air compressor unit may include three compressors in series (three compression stages) and two intercoolers, each of which is installed between two adjacent compressors (compression stages).
  • first stage compressor 102 (first compression stage) is in fluid communication with air cooler 101.
  • First stage compressor 102 (first compression stage) may be adapted to receive cooled air stream 11 from air cooler 101 and compress cooled air to form first compressed air stream 12.
  • First compressed air stream 12 may have a pressure of 0.22 MPa to 0.27 MPa and all values and ranges there between including 0.23 MPa, 0.24 MPa, 0.25 MPa, 0.26 MPa.
  • An outlet of first stage compressor 102 may be in fluid communication with an inlet of first stage intercooler 103, which is adapted to cool down first compressed air stream 12 to form first cooled and compressed air stream 13 and first water blowdown stream 14.
  • first stage intercooler 103 may be configured to reduce a temperature of compressed air stream 12 by 75 to 80 °C including 76 °C, 77 °C, 78 °C, and 79 °C.
  • a water outlet of first stage intercooler 103 may be in fluid communication with an inlet of blowdown storage tank 104, which is configured to receive first water blowdown stream 14 from first stage intercooler 103.
  • an outlet of blowdown storage tank 104 may be in fluid communication with air cooler 101.
  • Second stage compressor 105 may be configured to further compress cooled and compressed air stream 13 to form second compressed air stream 15.
  • second compressed air stream 15 may have a pressure in a range of 0.39 MPa to 0.45 MPa and all values and ranges there between including 0.40 MPa, 0.41 MPa, 0.42 MPa, 0.43 MPa, and 0.44 MPa.
  • An outlet of second stage compressor 105 may be in fluid communication with an inlet of second stage intercooler 106.
  • Second stage intercooler 106 may be adapted to cool down second compressed air stream 15 to form second cooled and compressed air stream 16 and second water blowdown stream 17.
  • Second intercooler 106 may be configured to reduce a temperature of second compressed air stream 15 for 60 to 65 °C and all ranges and values there between including 61 °C, 62 °C, 63 °C, and 64 °C.
  • a water outlet of second stage intercooler 106 may be in fluid communication with blowdown storage tank 104 for flowing second water blowdown stream 17 into blowdown storage tank 104.
  • An air outlet of second stage intercooler 106 may be in fluid communication with third stage compressor 107 (third compression stage), which is configured to further compress second cooled and compressed air stream 16 to form compressed process air stream 18.
  • compressed process air stream 18 may have a pressure of 0.54 to 0.59 MPa and all ranges and values there between including 0.55 MPa, 0.56 MPa, 0.57 MPa, and 0.58 MPa.
  • a temperature of compressed process air stream 18 may be in a range of 80 to 90 °C and all ranges and values there between including 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, 86 °C, 87 °C, 88 °C, and 89 °C.
  • third stage compressor 107 may be in fluid communication with an air separation unit.
  • the air separation unit may include cryogenic high pressure distillation column and cryogenic low pressure distillation column.
  • water blowdown from each intercooler may be collected in blowdown storage tank 104 as cooling medium for water cooler 101.
  • the last air compressor (the last compression stage) that the air passes through may be in fluid communication with the air separation unit.
  • air compression system 100 may further include a control system adapted to control flowrate of blowdown water used to cool down atmospheric air that is flowed into air cooler 101.
  • the control system may include a temperature sensor configured to measure a temperature of the atmospheric air that is flowed into air cooler 101.
  • the control system may further include a humidity sensor configured to measure a humidity a humidity level of the atmospheric air that is flowed into air cooler 101.
  • the control system may still further include a flow controller configured to adjust a flowrate of water blowdown in air cooler 101 in response to measurements of the temperature sensor and/or the humidity sensor.
  • the blowdown water can be used to spray the atmospheric air flowed into the air cooler.
  • the humidity measurement from the humidity sensor is less than about 8.42> ⁇ 10 "3
  • no water blowdown can be collected in blowdown storage tank 104, thereby flow rate of blowdown water in water cooler may be substantially zero.
  • flow rate of blowdown water may be set to zero by the flow controller as spraying water on the atmospheric air may result in dew formation instead of cooling atmospheric air.
  • FIG. 2 shows method 200 for processing air prior to separating components of the air.
  • Method 200 may be implemented by air compression system 100 as shown in FIG. 1.
  • method 200 may include measuring humidity and/or temperature of the air.
  • the measuring at block 201 may be performed at an inlet of water cooler 101.
  • the 200 may include cooling the air with a cooling medium to produce cooled air.
  • the air may be cooled by latent heat of the cooling medium and the cooling medium may be vaporized during the cooling at block 202.
  • the cooling medium may include water blowdown collected from one or more of first stage intercooler 103 and second stage intercooler 106.
  • the cooling medium at block 202 may directly contact the air.
  • the water blowdown can be sprayed to and mixed in the air in the cooling step at block 202.
  • an air to cooling medium ratio in the step of cooling the air may be in a range of 37: 1 to 1000: 1 and all ranges and values there between including ranges of 37: 1 to 50: 1, 50: 1 to 100: 1, 100: 1 to 150: 1, 150: 1 to 200: 1, 200: 1 to 250: 1, 250: 1 to 300: 1, 300: 1 to 350: 1, 350: 1 to 400: 1, 400: 1 to 450: 1, 450: 1 to 500: 1, 500: 1 to 550: 1, 550: 1 to 600: 1, 600: 1 to 650: 1, 650: 1 to 700: 1, 700: 1 to 750: 1, 750: 1 to 800: 1, 800: 1 to 850: 1, 850: 1 to 900: 1, 900: 1 to 950: 1, and 950: 1 to 1000: 1.
  • 202 may be performed in response to the humidity of the air measured at block 201 being no less than a predetermined humidity value and the temperature of the air measured at block
  • the predetermined humidity value may include a humidity ratio of about 8.42 ⁇ 10 "3 .
  • the predetermined temperature value may be about 15 °C.
  • water blowdown from one or more intercoolers of the air compressor unit may not be used as the cooling medium in the step of cooling the air at block 202.
  • the humidity ratio of the air is less than 8.42> ⁇ 10 "3 , no water blowdown may be collected as cooling medium.
  • the step of cooling the air at block 202 may reduce a temperature of the air by 10 to 16 °C and all ranges and values there between.
  • the cooled air may have a density in a range of 1.05 > ⁇ 10 "3 to 1.25> ⁇ 10 "3 g/cm 3 and all ranges and values there between including 1.05 x l0 "3 to 1.07x l0 "3 g/cm 3 , 1.07x l0 "3 to 1.09x 10 "3 g/cm 3 , 1.09x l0 "3 to l .
  • method 200 may further include compressing the cooled air in a compressor unit, as shown in block 203.
  • the compressor unit may be the multistage air compressing unit of air compressor system 100. More particularly, the step of compressing at block 203 may include compressing cooled air stream 1 1 in first stage compressor 102 (first compression stage) to form first compressed air stream 12. In certain aspects, first compressed air stream 12 may have a pressure of 0.22 to 0.27 MPa and all ranges and values there between.
  • the step of compressing at block 203 may further include cooling first compressed air stream 12 in first stage intercooler 103 to form first cooled and compressed air stream 13 and first water blowdown stream 14.
  • the cooling in the first stage intercooler 103 may reduce the temperature of first compressed air stream 12 by 0.75 to 80 °C and all ranges and values there between including ranges of 0.75 to 1 °C, 1 to 5 °C, 5 to 10 °C, 10 to 15 °C, 15 to 20 °C, 25 to 30 °C, 30 to 35 °C, 35 to 40 °C, 40 to 45 °C, 45 to 50 °C, 50 to 55 °C, 55 to 60 °C, 60 to 65 °C, 65 to 70 °C, 70 to 75 °C, and 75 to 80 °C.
  • First cooled and compressed air stream 13 may be further compressed in second stage compressor 105 (second compression stage) to form second compressed air stream 15.
  • second compressed air stream 15 may have a pressure of 0.39 to 0.45 MPa and all ranges and values there between including 0.40 MPa, 0.41 MPa, 0.42 MPa, 0.43 MPa, and 0.44 MPa.
  • second compressed air stream 15 may be cooled by second stage intercooler 106 to form second cooled and compressed air stream 16 and second water blowdown stream 17.
  • the cooling in the second stage intercooler 106 may reduce the temperature of second compressed air stream 15 by 60 to 65 °C and all ranges and values there between including 61 °C, 62 °C, 63 °C, and 64 °C.
  • Second cooled and compressed air stream 16 may be further compressed in third stage compressor 107 (third compression stage) to form compressed process air stream 18.
  • compressed process air stream 18 may have a pressure of 0.54 to 0.59 MPa and all ranges and values there between including 0.55 MPa, 0.56 MPa, 0.57 MPa, and 0.58 MPa.
  • Compressed process air stream 18 may be at a temperature of 80 to 90 °C and all ranges and values there between including 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, 86 °C, 87 °C, 88 °C, and 89 °C.
  • the multistage compressor unit of air compressor system 100 may include n compressor (n compression stages) and n- ⁇ intercoolers, where n represents the number of compression stages in the multistage compressor unit (n is a positive integer and n>2).
  • the compressing at block 203 may include compressing cooled air stream 1 1 by the n compressors in series and cooling the compressed air by the n- ⁇ intercoolers, each of which is installed between two adjacent compression stages.
  • the compressed process air from the rP 1 compressor may have a pressure of 0.54 to 0.8 MPa and a temperature of 75 to 90 °C.
  • the compressed process air may be in gas form (only for gaseous air). Water blowdown may be formed in and collected from at least one of the n- ⁇ intercoolers.
  • method 200 may further include collecting water blowdown from the one or more intercoolers.
  • the collected water blowdown may be used as the cooling medium at block 202.
  • water blowdown may be collected from first stage intercooler 103 and/or second stage intercooler 106 to blowdown storage tank 104.
  • the water blowdown from blowdown storage tank 104 may be sprayed to and mixed in the air in air cooler 101.
  • the water blowdown collected from intercoolers may have a temperature of 10 to 35 °C and all values and ranges there between including 10 to 12 °C, 12 to 14 °C, 14 to 16 °C, 16 to 18 °C, 18 to 20 °C, 20 to 22 °C, 22 to 24 °C, 24 to 26 °C, 26 to 28 °C, 28 to 30 °C, 30 to 32 °C, and 32 to 35 °C.
  • the water blowdown collected from intercoolers is sufficient to cool down the air in air cooler 101 when the humidity ratio of the air is above 0.842%.
  • the cooling at block 202 may be performed in a closed loop without adding make up water to air cooler 101 and/or blowdown storage tank 104.
  • make up water may be added to air cooler 101 and/or blowdown storage tank 104 when the humidity ratio of the air is less than 2.70%. When the air humidity reaches saturation (maximum humidity), spraying water on air can cause dew formation.
  • the method of processing air prior to separating components of the air was simulated in ASPEN PLUS platform.
  • the model for the simulation runs was built and validated using real process data from an air separation unit.
  • the initial condition for the air feeding into the air compression system included a temperature of 17.4 °C and a pressure of 1.01 bar.
  • the flow rate of the air feeding into the air compression system was 403839 Normal Cubic Meter per Hour.
  • the compositions of the air included 74.62 mol.% nitrogen, 22 mol.% oxygen, 0.89 mol.% argon, and 2.4 mol.% water.
  • the results of the simulations show that the method of the present invention reduced power consumption of the compressor in terms of withdrawn megawatts when compared to the traditional method, which does not apply cooling at the inlet of multistage compressor.
  • Sensitivity analysis was conducted to optimize the fraction of water blowdown being recycled as cooling medium using the simulation results. According to the results shown in FIG. 3, under the aforementioned initial conditions, the optimal fraction of water blowdown being recycled as cooling medium is about 80%, where the power consumption for air compressor unit is at its lowest point of about 31.2 megawatts and the mix air (i.e. temperature of stream 11) temperature is about 29 °C.

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Abstract

A system and a method for processing air prior to separating components of the air are disclosed. The system comprises an air cooler, one or more compression stages operated in series, and one or more intercoolers installed between two adjacent compression stages. A blowdown storage tank is configured to collect water blowdown from one or more intercoolers and provide cooling medium to the air cooler. Atmospheric air is first sprayed by the water blowdown in the air cooler to form a cooled air stream. The cooled air stream is subsequently compressed in the one or more compression stages and cooled by the intercoolers between two adjacent compression stages. The water blowdown from one or more of the intercoolers is collected and recycled as the cooling medium to cool the atmospheric air before it enters the first compression stage.

Description

PROCESS FOR UTILIZING OF MULTI STAGE COMPRESSORS
INTERCOOLERS BLOWDOWN AS A COOLANT FOR PROCESS AIR
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/559, 166, filed September 15, 2017, which is hereby incorporated by reference in its entirety.
FIELD OF INVENTION
[0002] The present invention generally relates to air compression processes. More specifically, the present invention relates to an air compression process that uses water blowdown from intercoolers of a multistage compressor as a cooling medium to cool the air feeding into the multistage compressor.
BACKGROUND OF THE INVENTION
[0003] Atmospheric air is generally processed in an air separation plant to produce nitrogen, oxygen, argon and other inert gases. These products separated from air are utilized in many industries including chemical industry, medical industry, and semiconductor industry.
[0004] Typically, atmospheric air is first cleaned via filters to remove dust suspended in the air. Clean atmospheric air is subsequently compressed by an air compressor unit. In the compression process, clean air is compressed and cooled by a series of air compressors and intercoolers. Water fraction from the clean air is condensed in intercoolers and separated from the air. After trace water is further removed from the compressed air via molecular sieve, a heat exchanger is generally used to liquefy at least part of the compressed air, to form purified oxygen. The remaining gas is further distilled in a high pressure column and a low pressure column to produce purified nitrogen and purified argon. [0005] However, the conventional air separation process is highly energy intensive.
Energy consumption analysis for the whole cryogenic air separation process shows that even though the process involves several cooling steps and high pressure and low pressure distillation processes, it is the multistage air compressor that consumes the most energy in the cryogenic air separation unit. Therefore, improvements in the field are needed. BRIEF SUMMARY OF THE INVENTION
[0006] A method has been discovered for compressing air for an air separation unit.
The method provides a solution for the above mentioned problems associated with air separation process. The solution resides in a method of processing air prior to separating the components of the air. Notably, by cooling the atmospheric air before it is fed into the multistage compressor, the atmospheric air feeding into the compressor becomes denser and the temperature of the atmospheric air can be reduced. This can be beneficial for reducing the energy consumption of the multistage compressor as the volume of the air is reduced when it is cooled, thereby lowering the power required to compress the air. Furthermore, the cooling process of the atmospheric air can be performed using the blowdown water collected from the intercoolers of the multistage compressor as the cooling medium, thus avoiding additional costs for cooling medium. By way of example, in this method, the blowdown water from each of the intercoolers of the multistage compressor can be collected in a storage tank and used to spray and mix in the atmospheric air, via a water sprinkler and/or water mister, thereby cooling the atmospheric air. As a result of cooling, the energy required by the method to compress the atmospheric air can be reduced compared to using the currently available method.
[0007] Embodiments of the invention include a method of processing air prior to separating components of the air. The method comprises cooling the air with a cooling medium to produce cooled air. The method may further include compressing the cooled air in a compressor unit that comprises one or more compressors and one or more intercoolers. Still further, the method includes collecting water blowdown from the one or more intercoolers, wherein the water blowdown is used as the cooling medium.
[0008] Embodiments of the invention include a method of processing air prior to separating components of the air. The method includes cooling the air with a cooling medium to produce cooled air. The method may further include compressing the cooled air in a multistage compressor unit. The multistage compressor unit comprises at least two compressors for two compression stages and at least one intercooler for cooling compressed air from the at least two compressors. The method further includes collecting water blowdown from the at least one intercooler of the multistage compressor unit. In this method, the water blowdown is used as the cooling medium. [0009] Embodiments of the invention include a method of processing air prior to separating components of the air. The method includes measuring humidity and temperature of the air. The air is cooled by a cooling medium if humidity of the air exceeds a predetermined humidity value and temperature of the air exceeds a predetermined temperature value. The method further includes compressing the cooled air in a multistage compressor unit. The multistage compressor unit includes at least three compressors for three compression stages and at least two intercoolers. Still further, the method includes collecting water blowdown from at least one of the intercoolers of the multistage compressor unit. The water blowdown is used as the cooling medium. [0010] The following includes definitions of various terms and phrases used throughout this specification.
[0011] The terms "about" or "approximately" are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, preferably, within 5%, more preferably, within 1%, and most preferably, within 0.5%.
[0012] The terms "wt.%", "vol.%" or "mol.%" refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol.% of component. [0013] The term "substantially" and its variations are defined to include ranges within
10%, within 5%, within 1%, or within 0.5%.
[0014] The term "avoiding" or any variation of the term, when used in the claims and/or the specification, includes any measurable decrease or complete inhibition to achieve a desired result. [0015] The term "effective," as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result.
[0016] The use of the words "a" or "an" when used in conjunction with the term
"comprising," "including," "containing," or "having" in the claims or the specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one."
[0017] In the context of the present invention at least nineteen embodiments are now described. Embodiment 1 is a method of processing air prior to separating components of the air. The method includes the steps of cooling the air with a cooling medium to produce cooled air; compressing the cooled air in a compressor unit that comprises one or more compression stages and one or more intercoolers to produce compressed process air; and collecting water blowdown from the one or more intercoolers, wherein the water blowdown is used as the cooling medium. Embodiment 2 is the method of embodiment 1, wherein the compressor unit is a multi-stage compressor unit. Embodiment 3 is the method of embodiment 2, wherein the multi-stage compressor unit includes at least two compression stages and at least one intercooler for cooling compressed air from the at least two compression stages. Embodiment 4 is the method of any of embodiments 2 and 3, wherein the multi-stage compressor unit includes at least three compression stages in series and at least two intercoolers for cooling compressed air from the at least three compression stages. Embodiment 5 is the method of any of embodiments 1 to 4, further including a step, before the cooling, of measuring humidity and temperature of the air, wherein the step of cooling the air with a cooling medium is performed in response to the humidity of the air greater than a predetermined humidity value and temperature of the air greater than a predetermined temperature value. Embodiment 6 is the method of embodiment 5, wherein the predetermined humidity value include a humidity ratio of 8.42>< 10"3. Embodiment 7 is the method of any of embodiments 5 and 6, wherein the predetermined temperature value is about 15°C. Embodiment 8 is the method of any of embodiments 1 to 7, wherein the water blowdown is used as the cooling medium at an air to cooling medium ratio of 37: 1 to 1000: 1. Embodiment 9 is the method of any of embodiments 1 to 8, wherein the water blowdown directly contacts the air in the cooling step. Embodiment 10 is the method of any of embodiments 1 to 9, wherein cooling the air with a cooling medium is performed by spraying the air with the cooling medium and mixing the air with the cooling medium. Embodiment 11 is the method of any of embodiments 1 to 10, wherein the water blowdown is collected and stored in a storage tank. Embodiment 12 is the method of any of embodiments 1 to 11, wherein the cooled air has a temperature in a range of 15 to 30°C. Embodiment 13 is the method of any of embodiments 1 to 12, wherein the cooled air has a density in a range of 1.05>< 10"3 to 1.25x 10" 3 g/cm3. Embodiment 14 is the method of any of embodiments 1 to 13, wherein the intercooler includes a heat exchanger. Embodiment 15 is the method of any of embodiments 1 to 14, wherein the cooling medium has a temperature of 10 to 35°C. Embodiment 16 is the method of any of embodiments 1 to 15, wherein the compressed process air is at a pressure of 0.54 to 0.59 MPa. Embodiment 17 is the method of any of embodiments 1 to 16, wherein the compressed process air is gaseous. Embodiment 18 is the method of any of embodiments 1 to 17, wherein the compressed process air is sent to a cryogenic separation unit and separated into one or more of nitrogen, oxygen, and argon.
[0018] Embodiment 19 is a method of processing air prior to separating components of the air. The method includes the steps of measuring humidity and temperature of the air; if humidity of the air exceeds a predetermined humidity value and temperature of the air exceeds a predetermined temperature value, cooling the air with a cooling medium to produce cooled air; compressing the cooled air in a multi-stage compressor unit, the multi-stage compressor unit including at least three compression stages and at least two intercoolers; and collecting water blowdown from at least one of the intercoolers of the multi-stage compressor unit, wherein the water blowdown is used as the cooling medium.
[0019] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] For a more complete understanding, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: [0021] FIG. 1 shows a schematic diagram of an air compression system, according to embodiments of the invention; [0022] FIG. 2 shows a schematic flow chart of a method of compressing air, according to embodiments of the invention; and
[0023] FIG. 3 shows results of sensitivity analysis based on simulation runs on a method of compressing air, according to embodiments of the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The currently available method of compressing atmospheric air includes directly compressing atmospheric (or cleaned atmospheric) air by a multistage compressor. This is highly energy intensive especially when the temperature of the atmospheric air is elevated, and the volume of atmospheric air is expanded. The present invention provides a solution to this problem. The solution is premised on a method of compressing atmospheric air that includes a step of cooling the atmospheric air feeding into a multistage compressor prior to flowing the air into the multistage compressor. Therefore, the volume of the atmospheric air can be reduced, decreasing the power required to compress the air. The cooling medium used in the cooling step can be at least some of the blowdown water collected from the intercooler of the multistage compressor, thereby recycling the water in the atmospheric air and saving costs for cooling medium. The humidity level in the atmospheric air may be sufficient to provide all the cooling medium needed in the method of the present invention. [0025] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.
A. Air Compression System
[0026] An air compression system can be part of cryogenic air separation unit, providing compressed air for the subsequent cryogenic air separation processes. For conventional air compression systems, atmospheric air or filtered atmospheric air is directly fed into the inlet of a multistage compressor. As atmospheric air is typically obtained from an outdoor environment, the volume of the air can be expanded when the outdoor temperature is elevated. For instance, atmospheric air can be highly expanded in the summer when the ambient temperature is greater than 35 °C, or even greater than 40 °C. This may escalate the power load of the existing air compressor system, further increasing the operating costs for the overall air separation process. The present invention provides a system that can cool down the atmospheric air prior to the inlet of the multistage air compressor, thereby reducing the power load of the air compressor. Furthermore, the present invention requires minimal capital expenditure and substantially no additional operating cost to facilitate the cooling of the atmospheric air prior to the multistage compression. More particularly, the air compression system of the present invention uses water blowdown collected from the intercoolers of the multistage air compressor as cooling medium for the atmospheric air, avoiding need of any other coolants. The water blowdown can be simply sprayed and mixed into the atmospheric air via a water sprinkler or water mister, thereby requiring minimal costs for equipment or instruments.
[0027] With reference to FIG. 1, a schematic diagram shows air compression system
100 for reducing power load of a multistage air compressor, according to embodiments of the invention. As shown in FIG. 1, air compression system 100 may include air cooler 101 adapted to receive and cool down atmospheric air. In embodiments of the invention, air cooler 101 may be a spray water cooler. In some aspects, the spray water cooler may include a water sprinkler or a water mister adapted to mix water with atmospheric air. An outlet of air cooler 101 may be in fluid communication with an inlet of a multistage air compressor unit. [0028] According to embodiments of the invention, the multistage air compressor unit may include one or more compressors and one or more intercoolers. In more particular embodiments, the multistage air compressor unit can include at least two compressors (two compression stages) and at least one intercooler for cooling compressed air from a first stage compressor. In embodiments of the invention, the at least two compressors are installed in series. An intercooler may be installed between two adjacent compressor stages. Non- limiting examples of the intercooler include a heat exchanger with various cooling media such as cooling water or other cooled media.
[0029] In embodiments of the invention, as shown in FIG. 1, the multistage air compressor unit may include three compressors in series (three compression stages) and two intercoolers, each of which is installed between two adjacent compressors (compression stages). In more particular embodiments of the invention, as shown in FIG. 1, first stage compressor 102 (first compression stage) is in fluid communication with air cooler 101. First stage compressor 102 (first compression stage) may be adapted to receive cooled air stream 11 from air cooler 101 and compress cooled air to form first compressed air stream 12. First compressed air stream 12 may have a pressure of 0.22 MPa to 0.27 MPa and all values and ranges there between including 0.23 MPa, 0.24 MPa, 0.25 MPa, 0.26 MPa. [0030] An outlet of first stage compressor 102 may be in fluid communication with an inlet of first stage intercooler 103, which is adapted to cool down first compressed air stream 12 to form first cooled and compressed air stream 13 and first water blowdown stream 14. In certain aspects, first stage intercooler 103 may be configured to reduce a temperature of compressed air stream 12 by 75 to 80 °C including 76 °C, 77 °C, 78 °C, and 79 °C. A water outlet of first stage intercooler 103 may be in fluid communication with an inlet of blowdown storage tank 104, which is configured to receive first water blowdown stream 14 from first stage intercooler 103. According to embodiments of the invention, an outlet of blowdown storage tank 104 may be in fluid communication with air cooler 101. Blowdown storage tank 104 may be configured to provide water as cooling medium for cooling down atmospheric air. In more particular embodiments, blowdown storage tank may be adapted to provide water to water sprinkler and/or water mister of air cooler 101 for mixing atmospheric air with water blowdown. In some aspects, blowdown storage tank may further include an overflow valve, which is adapted to drain overflowing water blowdown when excess amount of water blowdown is collected therein. [0031] According to embodiments of the invention, a cooled air outlet of first stage intercooler may be in fluid communication with second stage compressor 105 (second compression stage) for flowing first cooled and compressed air stream 13 from first stage intercooler 103 to second stage compressor 105. Second stage compressor 105 (second compression stage) may be configured to further compress cooled and compressed air stream 13 to form second compressed air stream 15. In certain aspects, second compressed air stream 15 may have a pressure in a range of 0.39 MPa to 0.45 MPa and all values and ranges there between including 0.40 MPa, 0.41 MPa, 0.42 MPa, 0.43 MPa, and 0.44 MPa.
[0032] An outlet of second stage compressor 105 (second compression stage) may be in fluid communication with an inlet of second stage intercooler 106. Second stage intercooler 106 may be adapted to cool down second compressed air stream 15 to form second cooled and compressed air stream 16 and second water blowdown stream 17. Second intercooler 106 may be configured to reduce a temperature of second compressed air stream 15 for 60 to 65 °C and all ranges and values there between including 61 °C, 62 °C, 63 °C, and 64 °C. A water outlet of second stage intercooler 106 may be in fluid communication with blowdown storage tank 104 for flowing second water blowdown stream 17 into blowdown storage tank 104. An air outlet of second stage intercooler 106 may be in fluid communication with third stage compressor 107 (third compression stage), which is configured to further compress second cooled and compressed air stream 16 to form compressed process air stream 18. In certain aspects, compressed process air stream 18 may have a pressure of 0.54 to 0.59 MPa and all ranges and values there between including 0.55 MPa, 0.56 MPa, 0.57 MPa, and 0.58 MPa. A temperature of compressed process air stream 18 may be in a range of 80 to 90 °C and all ranges and values there between including 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, 86 °C, 87 °C, 88 °C, and 89 °C. According to embodiments to the invention, third stage compressor 107 (third compression stage) may be in fluid communication with an air separation unit. Non-limiting examples for the air separation unit may include cryogenic high pressure distillation column and cryogenic low pressure distillation column. In embodiments of the invention, for air compression system 100 that includes more than three air compressors (three compression stages) and more than two intercoolers, water blowdown from each intercooler may be collected in blowdown storage tank 104 as cooling medium for water cooler 101. The last air compressor (the last compression stage) that the air passes through may be in fluid communication with the air separation unit.
[0033] In more particular embodiments, air compression system 100 may further include a control system adapted to control flowrate of blowdown water used to cool down atmospheric air that is flowed into air cooler 101. In certain aspects, the control system may include a temperature sensor configured to measure a temperature of the atmospheric air that is flowed into air cooler 101. The control system may further include a humidity sensor configured to measure a humidity a humidity level of the atmospheric air that is flowed into air cooler 101. The control system may still further include a flow controller configured to adjust a flowrate of water blowdown in air cooler 101 in response to measurements of the temperature sensor and/or the humidity sensor. In certain aspects, when the humidity measurement from the humidity sensor is no less than about 8.42x 10"3 and/or the temperature measurement from the temperature sensor is no less than about 15 °C, the blowdown water can be used to spray the atmospheric air flowed into the air cooler. When the humidity measurement from the humidity sensor is less than about 8.42>< 10"3, no water blowdown can be collected in blowdown storage tank 104, thereby flow rate of blowdown water in water cooler may be substantially zero. When the temperature measurement from the temperature sensor is less than about 15 °C, or when humidity of the air is saturation humidity, flow rate of blowdown water may be set to zero by the flow controller as spraying water on the atmospheric air may result in dew formation instead of cooling atmospheric air.
B. Method of Processing Air Prior to Separation
[0034] In embodiments of the invention, there are provided methods of processing air prior to separating components of the air. FIG. 2 shows method 200 for processing air prior to separating components of the air. Method 200 may be implemented by air compression system 100 as shown in FIG. 1. As shown in block 201, method 200 may include measuring humidity and/or temperature of the air. In embodiments of the invention, the measuring at block 201 may be performed at an inlet of water cooler 101.
[0035] According to embodiments of the invention, as shown in block 202, method
200 may include cooling the air with a cooling medium to produce cooled air. In certain aspects, the air may be cooled by latent heat of the cooling medium and the cooling medium may be vaporized during the cooling at block 202. In more particular embodiments, the cooling medium may include water blowdown collected from one or more of first stage intercooler 103 and second stage intercooler 106. The cooling medium at block 202 may directly contact the air. In certain aspects, the water blowdown can be sprayed to and mixed in the air in the cooling step at block 202. In embodiments of the invention, an air to cooling medium ratio in the step of cooling the air may be in a range of 37: 1 to 1000: 1 and all ranges and values there between including ranges of 37: 1 to 50: 1, 50: 1 to 100: 1, 100: 1 to 150: 1, 150: 1 to 200: 1, 200: 1 to 250: 1, 250: 1 to 300: 1, 300: 1 to 350: 1, 350: 1 to 400: 1, 400: 1 to 450: 1, 450: 1 to 500: 1, 500: 1 to 550: 1, 550: 1 to 600: 1, 600: 1 to 650: 1, 650: 1 to 700: 1, 700: 1 to 750: 1, 750: 1 to 800: 1, 800: 1 to 850: 1, 850: 1 to 900: 1, 900: 1 to 950: 1, and 950: 1 to 1000: 1.
[0036] In certain aspects, the step of cooling the air with the water blowdown at block
202 may be performed in response to the humidity of the air measured at block 201 being no less than a predetermined humidity value and the temperature of the air measured at block
201 being no less than a predetermined temperature value. The predetermined humidity value may include a humidity ratio of about 8.42χ 10"3. The predetermined temperature value may be about 15 °C. In embodiments of the invention, when the humidity of the air measured at block 201 is less than the predetermined humidity value and/or the temperature of the air measure at block 201 is less than the predetermined temperature value, water blowdown from one or more intercoolers of the air compressor unit may not be used as the cooling medium in the step of cooling the air at block 202. As described above, when the humidity ratio of the air is less than 8.42>< 10"3, no water blowdown may be collected as cooling medium. When the temperature of the air is less than 15 °C, or when humidity of the air is saturation humidity, the spraying of the water blowdown may lead to dew formation instead of cooling down the air. In certain aspects, the temperature of the air before the cooling at block 202 may be greater than 30 °C, greater than 35 °C, and greater than 40 °C. [0037] In certain aspects, the cooled air may have a temperature in a range of 15 to 30
°C and all ranges and values there between including 15 to 18 °C, 18 to 21 °C, 21 to 24 °C, 24 to 27 °C, and 27 to 30 °C. The step of cooling the air at block 202 may reduce a temperature of the air by 10 to 16 °C and all ranges and values there between. The cooled air may have a density in a range of 1.05 >< 10"3 to 1.25>< 10"3 g/cm3 and all ranges and values there between including 1.05 x l0"3 to 1.07x l0"3 g/cm3, 1.07x l0"3 to 1.09x 10"3 g/cm3, 1.09x l0"3 to l . l l x lO"3 g/cm3, l . l l x lO"3 to 1.13 X 10"3 g/cm3, 1.13 x l0"3 to 1.15 x l0"3 g/cm3, 1.15 x l0"3 to 1.17x l0"3 g/cm3, 1.17X 10"3 to 1.19x l0"3 g/cm3, 1.19x l0"3 to 1.21 x lO"3 g/cm3, 1.21 x lO"3 to 1.23 x l0"3 g/cm3, and 1.23 x l0-3 to 1.25 x l0-3 g/cm3.
[0038] According to embodiments of the invention, method 200 may further include compressing the cooled air in a compressor unit, as shown in block 203. The compressor unit may be the multistage air compressing unit of air compressor system 100. More particularly, the step of compressing at block 203 may include compressing cooled air stream 1 1 in first stage compressor 102 (first compression stage) to form first compressed air stream 12. In certain aspects, first compressed air stream 12 may have a pressure of 0.22 to 0.27 MPa and all ranges and values there between. The step of compressing at block 203 may further include cooling first compressed air stream 12 in first stage intercooler 103 to form first cooled and compressed air stream 13 and first water blowdown stream 14. In certain aspects, the cooling in the first stage intercooler 103 may reduce the temperature of first compressed air stream 12 by 0.75 to 80 °C and all ranges and values there between including ranges of 0.75 to 1 °C, 1 to 5 °C, 5 to 10 °C, 10 to 15 °C, 15 to 20 °C, 25 to 30 °C, 30 to 35 °C, 35 to 40 °C, 40 to 45 °C, 45 to 50 °C, 50 to 55 °C, 55 to 60 °C, 60 to 65 °C, 65 to 70 °C, 70 to 75 °C, and 75 to 80 °C. [0039] First cooled and compressed air stream 13 may be further compressed in second stage compressor 105 (second compression stage) to form second compressed air stream 15. In certain aspects, second compressed air stream 15 may have a pressure of 0.39 to 0.45 MPa and all ranges and values there between including 0.40 MPa, 0.41 MPa, 0.42 MPa, 0.43 MPa, and 0.44 MPa. Similarly, second compressed air stream 15 may be cooled by second stage intercooler 106 to form second cooled and compressed air stream 16 and second water blowdown stream 17. In certain aspects, the cooling in the second stage intercooler 106 may reduce the temperature of second compressed air stream 15 by 60 to 65 °C and all ranges and values there between including 61 °C, 62 °C, 63 °C, and 64 °C. Second cooled and compressed air stream 16 may be further compressed in third stage compressor 107 (third compression stage) to form compressed process air stream 18. In certain aspects, compressed process air stream 18 may have a pressure of 0.54 to 0.59 MPa and all ranges and values there between including 0.55 MPa, 0.56 MPa, 0.57 MPa, and 0.58 MPa. Compressed process air stream 18 may be at a temperature of 80 to 90 °C and all ranges and values there between including 81 °C, 82 °C, 83 °C, 84 °C, 85 °C, 86 °C, 87 °C, 88 °C, and 89 °C.
[0040] In embodiments of the invention, the multistage compressor unit of air compressor system 100 may include n compressor (n compression stages) and n-\ intercoolers, where n represents the number of compression stages in the multistage compressor unit (n is a positive integer and n>2). The compressing at block 203 may include compressing cooled air stream 1 1 by the n compressors in series and cooling the compressed air by the n-\ intercoolers, each of which is installed between two adjacent compression stages. The compressed process air from the rP1 compressor may have a pressure of 0.54 to 0.8 MPa and a temperature of 75 to 90 °C. In embodiments of the invention, the compressed process air may be in gas form (only for gaseous air). Water blowdown may be formed in and collected from at least one of the n-\ intercoolers.
[0041] In embodiments of the invention, as shown in block 204, method 200 may further include collecting water blowdown from the one or more intercoolers. The collected water blowdown may be used as the cooling medium at block 202. In some more particular embodiments, water blowdown may be collected from first stage intercooler 103 and/or second stage intercooler 106 to blowdown storage tank 104. The water blowdown from blowdown storage tank 104 may be sprayed to and mixed in the air in air cooler 101. In certain aspects, the water blowdown collected from intercoolers may have a temperature of 10 to 35 °C and all values and ranges there between including 10 to 12 °C, 12 to 14 °C, 14 to 16 °C, 16 to 18 °C, 18 to 20 °C, 20 to 22 °C, 22 to 24 °C, 24 to 26 °C, 26 to 28 °C, 28 to 30 °C, 30 to 32 °C, and 32 to 35 °C. In more particular embodiments, the water blowdown collected from intercoolers is sufficient to cool down the air in air cooler 101 when the humidity ratio of the air is above 0.842%. Therefore, the cooling at block 202 may be performed in a closed loop without adding make up water to air cooler 101 and/or blowdown storage tank 104. In certain aspects, make up water may be added to air cooler 101 and/or blowdown storage tank 104 when the humidity ratio of the air is less than 2.70%. When the air humidity reaches saturation (maximum humidity), spraying water on air can cause dew formation.
[0042] Although embodiments of the present invention have been described with reference to blocks of FIG. 2, it should be appreciated that operation of the present invention is not limited to the particular blocks and/or the particular order of the blocks illustrated in FIG. 2. Accordingly, embodiments of the invention may provide functionality as described herein using various blocks in a sequence different than that of FIG. 2.
[0043] As part of the disclosure of the present invention, a specific example is included below. The example is for illustrative purposes only and is not intended to limit the invention. Those of ordinary skill in the art will readily recognize parameters that can be changed or modified to yield essentially the same results. EXAMPLE
(Simulation of the Air Compression Process)
[0044] The method of processing air prior to separating components of the air, according to embodiments of the invention, was simulated in ASPEN PLUS platform. The model for the simulation runs was built and validated using real process data from an air separation unit. The initial condition for the air feeding into the air compression system included a temperature of 17.4 °C and a pressure of 1.01 bar. The flow rate of the air feeding into the air compression system was 403839 Normal Cubic Meter per Hour. The compositions of the air included 74.62 mol.% nitrogen, 22 mol.% oxygen, 0.89 mol.% argon, and 2.4 mol.% water. The results of the simulations show that the method of the present invention reduced power consumption of the compressor in terms of withdrawn megawatts when compared to the traditional method, which does not apply cooling at the inlet of multistage compressor.
[0045] Sensitivity analysis was conducted to optimize the fraction of water blowdown being recycled as cooling medium using the simulation results. According to the results shown in FIG. 3, under the aforementioned initial conditions, the optimal fraction of water blowdown being recycled as cooling medium is about 80%, where the power consumption for air compressor unit is at its lowest point of about 31.2 megawatts and the mix air (i.e. temperature of stream 11) temperature is about 29 °C.
[0046] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

1. A method of processing air prior to separating components of the air, the method comprising:
cooling the air with a cooling medium to produce cooled air; compressing the cooled air in a compressor unit that comprises one or more compression stages and one or more intercoolers to produce compressed process air; and
collecting water blowdown from the one or more intercoolers, wherein the water blowdown is used as the cooling medium.
2. The method of claim 1, wherein the compressor unit is a multi-stage compressor unit.
3. The method of claim 2, wherein the multi-stage compressor unit comprises at least two compression stages and at least one intercooler for cooling compressed air from the at least two compression stages.
4. The method of any of claims 2 and 3, wherein the multi-stage compressor unit comprises at least three compression stages in series and at least two intercoolers for cooling compressed air from the at least three compression stages.
5. The method of any of claims 1 to 2, further comprising, before the cooling, measuring humidity and temperature of the air, wherein the step of cooling the air with a cooling medium is performed in response to the humidity of the air greater than a predetermined humidity value and temperature of the air greater than a predetermined temperature value.
6. The method of claim 5, wherein the predetermined humidity value include a humidity ratio of 8.42 10-3.
7. The method of claim 5, wherein the predetermined temperature value is about 15 oC.
8. The method of any of claims 1 to 2, wherein the water blowdown is used as the cooling medium at an air to cooling medium ratio of 37: 1 to 1000: 1.
9. The method of any of claims 1 to 2, wherein the water blowdown directly contacts the air in the cooling step.
10. The method of any of claims 1 to 2, wherein cooling the air with a cooling medium is performed by spraying the air with the cooling medium and mixing the air with the cooling medium.
1 1. The method of any of claims 1 to 2, wherein the water blowdown is collected and stored in a storage tank.
12. The method of any of claims 1 to 2, wherein the cooled air has a temperature in a range of 15 to 30 oC.
13. The method of any of claims 1 to 2, wherein the cooled air has a density in a range of 1.05 10-3 to 1.25 10-3 g/cm3.
14. The method of any of claims 1 to 2, wherein the intercooler includes a heat exchanger.
15. The method of any of claims 1 to 2, wherein the cooling medium has a temperature of 10 to 35 oC.
16. The method of any of claims 1 to 2, wherein the compressed process air is at a pressure of 0.54 to 0.59 MPa.
17. The method of any of claims 1 to 2, wherein the compressed process air is gaseous.
18. The method of any of claims 1 to 2, wherein the compressed process air is sent to a cryogenic separation unit and separated into one or more of nitrogen, oxygen, and argon.
A method of processing air prior to separating components of the air, the method comprising:
measuring humidity and temperature of the air; if humidity of the air exceeds a predetermined humidity value and temperature of the air exceeds a predetermined temperature value, cooling the air with a cooling medium to produce cooled air; compressing the cooled air in a multi-stage compressor unit, the multi-stage compressor unit comprising at least three compression stages and at least two intercoolers; and collecting water blowdown from at least one of the intercoolers of the multistage compressor unit, wherein the water blowdown is used as the cooling medium.
EP18759398.3A 2017-09-15 2018-07-25 Process for utilizing of multi stage compressors intercoolers blowdown as a coolant for process air Withdrawn EP3682178A1 (en)

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US5282726A (en) * 1991-06-21 1994-02-01 Praxair Technology, Inc. Compressor supercharger with evaporative cooler
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FR2878294A1 (en) * 2004-11-24 2006-05-26 Air Liquide Compressor useful in apparatus for separating gas mixture, especially air, comprises two compression stages and directly water-cooled intercooler
FR2946099A1 (en) * 2009-05-26 2010-12-03 Air Liquide Humid air flow compressing method for separating air by cryogenic distillation, involves sending part of condensed water to upstream of compression stage, where water partially enters stage at liquid state and is partly vaporized in stage

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