US20120103011A1 - Method and apparatus for producing a cooled hydrocarbon stream - Google Patents

Method and apparatus for producing a cooled hydrocarbon stream Download PDF

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Publication number
US20120103011A1
US20120103011A1 US13/377,621 US201013377621A US2012103011A1 US 20120103011 A1 US20120103011 A1 US 20120103011A1 US 201013377621 A US201013377621 A US 201013377621A US 2012103011 A1 US2012103011 A1 US 2012103011A1
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stream
refrigerant
cooled
hydrocarbon
refrigerant stream
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Francois Chantant
Tolulope Bilikisu Longe
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Shell USA Inc
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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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • 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
    • F25J1/00—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures
    • F25J1/003—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production
    • F25J1/0047—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle
    • F25J1/0052—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using an "external" refrigerant stream in a closed vapor compression cycle by vaporising a liquid refrigerant 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
    • 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
    • F25J1/0022—Hydrocarbons, e.g. natural gas
    • 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
    • F25J1/0211—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 using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle
    • F25J1/0214—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 using a multi-component refrigerant [MCR] fluid in a closed vapor compression cycle as a dual level refrigeration cascade with at least one MCR cycle
    • 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
    • F25J1/0228—Coupling of the liquefaction unit to other units or processes, so-called integrated processes
    • F25J1/0235—Heat exchange integration
    • F25J1/0237—Heat exchange integration integrating refrigeration provided for liquefaction and purification/treatment of the gas to be liquefied, e.g. heavy hydrocarbon removal from natural gas
    • F25J1/0238—Purification or treatment step is integrated within one refrigeration cycle only, i.e. the same or single refrigeration cycle provides feed gas cooling (if present) and overhead gas 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
    • 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
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0244—Operation; Control and regulation; Instrumentation
    • F25J1/0245—Different modes, i.e. 'runs', of operation; Process control
    • F25J1/0249—Controlling refrigerant inventory, i.e. composition or quantity
    • 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
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0244—Operation; Control and regulation; Instrumentation
    • F25J1/0252—Control strategy, e.g. advanced process control or dynamic modeling
    • 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
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
    • F25J1/0262—Details of the cold heat exchange system
    • F25J1/0264—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams
    • F25J1/0265—Arrangement of heat exchanger cores in parallel with different functions, e.g. different cooling streams comprising cores associated exclusively with the cooling of a refrigerant stream, e.g. for auto-refrigeration or economizer
    • 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
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • 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
    • F25J1/0243—Start-up or control of the process; Details of the apparatus used; Details of the refrigerant compression system used
    • F25J1/0279—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc.
    • F25J1/0281—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc. characterised by the type of prime driver, e.g. hot gas expander
    • F25J1/0283—Gas turbine as the prime mechanical driver
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
    • G05B13/02—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric
    • G05B13/04—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion electric involving the use of models or simulators
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
    • G05B15/00—Systems controlled by a computer
    • G05B15/02—Systems controlled by a computer electric
    • 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
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/62—Separating low boiling components, e.g. He, H2, N2, 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
    • F25J2220/00—Processes or apparatus involving steps for the removal of impurities
    • F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
    • F25J2220/64—Separating heavy hydrocarbons, e.g. NGL, LPG, C4+ hydrocarbons or heavy condensates in general

Definitions

  • the present invention provides a method of producing a cooled hydrocarbon stream, comprising cooling of a hydrocarbon stream.
  • the present invention also provides an apparatus for producing a cooled hydrocarbon stream from a hydrocarbon stream.
  • a common hydrocarbon stream to be cooled is a natural gas stream.
  • a natural gas stream may be cooled to the extent that it is liquefied, in which case it is typically referred to as liquefied natural gas (LNG).
  • LNG liquefied natural gas
  • natural gas can be stored and transported over long distances more readily as a liquid than in gaseous form, because it occupies a smaller volume and does not need to be stored at high pressures.
  • Such liquefied natural gas can be stored at atmospheric pressure if maintained at cryogenic temperatures, such as at ⁇ 160° C. or below.
  • U.S. Pat. No. 6,370,910 discloses a method of liquefying a stream enriched in methane.
  • a natural gas stream is passed to a scrub column in which heavier hydrocarbons are removed to provide a gaseous overhead stream.
  • the gaseous overhead stream from the scrub column is partly condensed in an auxiliary (pre-cooling) heat exchanger.
  • a condensate stream is then removed from the partly condensed overhead gaseous stream to provide a stream enriched in methane.
  • the stream enriched in methane is then liquefied in a tube arranged in a main heat exchanger by indirect heat exchange with a multicomponent refrigerant evaporating at low pressure in the shell side of the main heat exchanger.
  • the multi-component refrigerant can be withdrawn from the shell side of the main heat exchanger and compressed.
  • the compressed multi-component refrigerant can then be partly condensed at elevated refrigerant pressure in a tube arranged in an auxiliary (pre-cooling) heat exchanger by indirect heat exchange with an auxiliary (pre-cooling) multi-component refrigerant evaporating at low pressure in the shell side of the auxiliary heat exchanger.
  • the partly condensed multi-component refrigerant can then be returned to the main heat exchanger.
  • U.S. Pat. No. 6,370,910 discloses an embodiment wherein the step of partly condensing the compressed multi-component refrigerant comprises cooling it at elevated pressure in a tube arranged in a first auxiliary heat exchanger by indirect heat exchanger with an auxiliary multi-component refrigerant evaporating at intermediate pressure in the shell side of the first auxiliary heat exchanger.
  • the multi-component refrigerant is then further cooled in a tube arranged in a second auxiliary heat exchanger by indirect heat exchange with an auxiliary multicomponent refrigerant evaporating at a low pressure in the shell side of the second auxiliary heat exchanger.
  • the present invention provides a method of producing a cooled hydrocarbon stream comprising cooling of a hydrocarbon stream.
  • the method comprises at least the steps of:
  • set of controlled variables comprises:
  • the temperature of at least one of the one or more cooled second streams the temperature difference between the first warmed first refrigerant stream and at least one of (i) the compressed first refrigerant stream and (ii) the first stream, the temperature difference between the second warmed first refrigerant stream and at least one of (i) the second portion of the first cooled first refrigerant stream and (ii) one of the one or more second streams in the form of the cooled first stream and/or the dependent stream derived from the cooled first stream, at least one of (i) the temperature difference between the first cooled first refrigerant stream and the first expanded first refrigerant stream and (ii) the temperature difference between the further cooled first refrigerant stream and the second expanded first refrigerant stream, and the power being consumed by the first compressor; and wherein the set of parameters to be optimised comprises the production rate of the cooled hydrocarbon stream and/or the cooling efficiency of the first refrigerant circuit.
  • the invention provides an apparatus for producing a cooled hydrocarbon stream from a hydrocarbon stream, comprising:
  • a first refrigerant circuit comprising an inventory of a first mixed refrigerant; a first expansion device; a second expansion device; a first compressor and one or more first coolers to cool a compressed stream from the first compressor thereby to provide a compressed first refrigerant stream; a first heat exchanger arranged to cool a first stream and the compressed first refrigerant stream, against a first expanded first refrigerant stream at a first pressure level, to provide a cooled first stream, a first cooled first refrigerant stream and a first warmed first refrigerant stream, the first expansion device being arranged to receive a first portion of the first cooled first refrigerant stream and to provide the first expanded first refrigerant stream; a second heat exchanger arranged to cool one or more second streams and a second portion of the first cooled first refrigerant stream, against a second expanded first refrigerant stream to provide one or more cooled second streams, a further cooled first refrigerant stream and a second warmed first refrig
  • set of controlled variables comprises:
  • the temperature of at least one of the one or more cooled second streams the temperature difference between the first warmed first refrigerant stream and at least one of (i) the compressed first refrigerant stream and (ii) the first stream, the temperature difference between the second warmed first refrigerant stream and at least one of (i) the second portion of the first cooled first refrigerant stream and (ii) one of the one or more second streams in the form of the cooled first stream and/or the dependent stream derived from the cooled first stream, at least one of (i) the temperature difference between the first cooled first refrigerant stream and the first expanded first refrigerant stream and (ii) the temperature difference between the further cooled first refrigerant stream and the second expanded first refrigerant stream; and the power being consumed by the first compressor; and wherein the set of parameters to be optimised comprises the production rate of the cooled hydrocarbon stream and/or the cooling efficiency of the first refrigerant circuit.
  • the cooling efficiency may reflect the power consumed in the first compressor in relation to the mass of cooled hydrocarbon stream produced over time.
  • FIG. 1 is a diagrammatic scheme of a method of and apparatus for cooling a hydrocarbon stream according to a first embodiment
  • FIG. 2 is a diagrammatic scheme of a method of and apparatus for cooling and liquefying a hydrocarbon stream according to a second embodiment.
  • the term “setting” is intended to represent a measure of the opening of a device, such as a valve.
  • controlling a controlled variable means keeping the controlled variable at a pre-determined value (set point) or within a pre-determined range (set range).
  • the term “optimizing a parameter” is intended to refer to maximizing or minimizing the parameter and to maintaining the parameter at a predetermined value.
  • the methods and apparatuses disclosed herein cool a hydrocarbon steam, preferably as part of a liquefaction process for the hydrocarbon.
  • the cooling process is controlled using an advanced process controller based on model predictive control, to optimise the production rate of the cooled hydrocarbon stream and/or the efficiency of the refrigeration process.
  • the setting of the expansion devices are manipulated variables.
  • Manipulating the setting of the expansion devices delivering the first mixed refrigerant to the first and second heat exchangers allows the optimisation of the cooling method.
  • the change in pressure of the first mixed refrigerant across the expansion devices can be manipulated. This in turn adjusts the change in temperature of the first refrigerant across the expansion devices, allowing the temperature at which the expanded first refrigerant streams cool the first and second streams to be manipulated.
  • Model predictive control or model based predictive control in itself is a known technique, as disclosed, for example, in Perry's Chemical Engineers' Handbook, 7 th Edition, pages 8-25 to 8-27.
  • U.S. Pat. No. 6,272,882 it has been applied in a process of liquefying a gaseous, methane-rich feed to obtain a liquefied product and mass flow rates of refrigerant fractions and stream to be cooled were utilized as manipulated variables.
  • the temperature difference at the warm end and midpoint of the main heat exchanger as controlled variables in order to optimise the production of a liquefied product.
  • U.S. Pat. No. 6,272,882 is primarily concerned with the operation of the main heat exchanger, rather than the pre-cooling heat exchanger(s).
  • Application of the advanced process control principles disclosed in U.S. Pat. No. 6,272,882, which utilises different compositions and flow rates of light and heavy mixed refrigerant fractions at a single pressure level is unsuitable for the control of a mixed refrigerant at different pressure levels as is the case in the present invention.
  • U.S. Pat. No. 6,272,882 uses as the manipulated variables the mass flow rates of light and heavy fractions of the mixed refrigerant. Applying this to the cooling of the first and second streams in the present case would have lead to the manipulation of the mass flow of the first mixed refrigerant. It has been found that manipulation of the mass flow of the first mixed refrigerant does not allow an acceptable optimisation of the production of the cooled hydrocarbon stream.
  • the method of the present invention utilizes control of temperature differential across at least one of the first and second expansion devices, rather than mass flow control of the refrigerant streams.
  • An advantage of the present invention is the ease with which the cooling curve of the first mixed refrigerant can be matched with the cooling curves of the first and second streams.
  • U.S. Pat. No. 6,272,882 teaches the use of two mixed refrigerant compositions, namely a light gaseous and a heavy liquid fraction, which are controlled by the separation of a partly condensed refrigerant stream in a separation vessel. It is difficult and time consuming to vary the overall composition of such a mixed refrigerant in order to modify the individual compositions of the light and heavy refrigerant fractions.
  • the present invention allows the cooling curve of the first mixed refrigerant to be changed by controlling the temperature differences of the first mixed refrigerant.
  • the cooling curve of a single mixed refrigerant composition can be optimised to closely match those of the first and second streams.
  • FIG. 1 shows a first embodiment an apparatus 1 for carrying out the method of cooling a hydrocarbon stream 50 to provide a cooled second stream in the form of a cooled hydrocarbon stream 60 .
  • the apparatus comprises a first refrigerant circuit 100 comprising an inventory of a first mixed refrigerant.
  • the first refrigerant circuit 100 comprises a first compressor 105 and one or more first coolers 115 a to 115 c , to cool a compressed effluent stream 110 from the first compressor 105 .
  • the effluent stream from the last one of the first coolers (here: 115 c ) is a compressed first refrigerant stream 120 .
  • the apparatus of FIG. 1 further comprises a first heat exchanger 125 .
  • the first heat exchanger 125 is arranged to cool a first stream (e.g. in the form of second refrigerant stream 220 ) as well as the compressed first refrigerant stream 120 , each stream in a tube side 221 respectively 121 .
  • the cooling medium is formed by a first expanded first refrigerant stream 140 in the shell side of the first heat exchanger 125 .
  • At the cold end of the first heat exchanger 125 there are outlets to provide at least one cooled first stream, e.g. in the form of cooled second refrigerant stream 230 , and a first cooled first refrigerant stream 130 .
  • a first expansion device 135 is arranged to receive a first portion 130 a of the first cooled first refrigerant stream 130 and to provide the first expanded first refrigerant stream 140 to the shell side of the first heat exchanger 125 .
  • the apparatus further comprises a second heat exchanger 145 arranged to cool the cooled first stream, which may be the cooled second refrigerant stream 230 , the hydrocarbon stream 50 and a second portion 130 b of the first cooled first refrigerant stream 130 , each stream in a tube side 231 respectively 51 respectively 131 .
  • the cooling medium is formed by a second expanded first refrigerant stream 170 in the shell side of the second heat exchanger 145 .
  • At the cold end of the second heat exchanger 145 there are outlets to provide at least a cooled hydrocarbon stream 60 , a further cooled first stream (for instance in the form of further cooled second main refrigerant stream 240 ), and a further cooled first refrigerant stream 160 .
  • a second expansion device 165 is arranged to receive at least a first portion of the further cooled first refrigerant stream 160 and to provide the second expanded first refrigerant stream 170 to the shell side of the second heat exchanger 145 .
  • the compressor 105 is arranged to compress gaseous fractions of the first warmed first refrigerant stream 150 and the second warmed first refrigerant stream 180 . It has a low pressure suction inlet arranged to receive the gaseous fraction 180 ′ of the second warmed first refrigerant stream 180 and an intermediate pressure suction inlet arranged to receive the gaseous fraction 150 ′ of the first warmed first refrigerant stream 150 .
  • a plurality of compressors may be used.
  • the hydrocarbon stream 50 is a (first) of one or more second streams passed to one or more second heat exchangers 145 .
  • the hydrocarbon stream 50 is supplied to a second heat exchanger hydrocarbon stream tube 51 in the second heat exchanger 145 , where it is cooled by indirectly heat exchanging with the first mixed refrigerant evaporating a low pressure in the shell side of the second heat exchanger 145 . It is preferred that the hydrocarbon stream 50 is partly condensed in the second heat exchanger 145 .
  • the cooled, preferably partly condensed, hydrocarbon exits the second heat exchanger 145 as a cooled hydrocarbon stream 60 , which is a cooled second stream.
  • the operation of the first mixed refrigerant which may be a pre-cooling refrigerant in a pre-cooling refrigerant circuit, is discussed in greater detail below.
  • the line-up of FIG. 1 further discloses the cooling of a further second stream, e.g. in the form of cooled second refrigerant stream 230 , and one or more first streams (e.g. comprising second refrigerant stream 220 ).
  • the method disclosed herein is particularly advantageous for the cooling of a second mixed refrigerant, which can be used in the further cooling and preferably liquefaction of cooled hydrocarbon stream 60 in a second cooling stage (not shown).
  • a second cooling stage is described in more detail in relation to the embodiment of FIG. 2 .
  • the second mixed refrigerant is preferably cooled, and more preferably partially condensed in two stages.
  • the second mixed refrigerant can be passed through one or both of the first and second heat exchangers 125 , 145 in the first cooling stage.
  • the first mixed refrigerant can be passed to second heat exchanger 125 as a (first) first stream in the form of second refrigerant stream 220 .
  • the second second mixed refrigerant is cooled at elevated pressure by indirect heat exchange with the first mixed refrigerant evaporating at intermediate pressure in the shell side of the first heat exchanger 125 . Cooled second mixed refrigerant exits the first heat exchanger 125 as cooled first stream in the form of a cooled second refrigerant stream 230 .
  • Cooled second refrigerant stream 230 may be passed to second heat exchanger 145 as (second) second stream 230 .
  • the cooled second mixed refrigerant stream is further cooled, and preferably partly condensed, at elevated pressure by indirect heat exchange with first refrigerant evaporating a low pressure in the shell side of the second heat exchanger 145 .
  • the further cooled second refrigerant exits the second heat exchanger 145 as a (second) cooled second stream which may be in the form of a further cooled second main refrigerant stream 240 .
  • the further cooled second refrigerant stream 240 may then be passed to a main heat exchanger (not shown) to provide cooling.
  • first warmed first refrigerant stream 150 the first mixed refrigerant evaporated at intermediate pressure in the shell side of the first heat exchanger 125 is removed therefrom as first warmed first refrigerant stream 150 at approximately the intermediate pressure level.
  • the first warmed first refrigerant stream 150 may be passed to a first knock out drum 155 to remove any liquid phase, prior to passing the gaseous components of the first warmed first refrigerant stream 150 to first compressor 105 as gaseous first warmed first refrigerant stream 150 ′.
  • the first compressor 105 may be a two-stage compressor.
  • the first compressor may be provided in the form of one or more first compressors (e.g. in serial configuration where one of the one or more first compressors perform one or more stages of compression and a subsequent one of the one or more first compressors perform one or more subsequent stages of compression; or in parallel arrangement where each of the parallel arranged compressors compress a portion of the total gaseous first warmed first refrigerant stream 150 ′) together acting as first compressor.
  • First compressor 105 may be driven by a first driver D 1 , such as a gas turbine, a steam turbine, an electric motor or combinations thereof.
  • the mixed gaseous first warmed first refrigerant stream 150 ′ is compressed to elevated pressure to provide compressed stream 110 .
  • Heat of compression together with at least a part of the heat absorbed from the first and second streams (for which can be used any of 120 , 50 , 130 b , 230 ) and the compressed first refrigerant stream 120 is removed using one or more first cooling devices 115 , such as ambient air coolers 115 a , 115 b to provide (first) and (second) cooled compressed first refrigerant streams 114 a , 114 b respectively.
  • the majority of the heat present in the compressed stream 110 is absorbed from the second refrigerant stream 220 as a first stream and the cooled second refrigerant stream 230 as a second stream.
  • first refrigerant accumulator 117 (Second) cooled compressed first refrigerant stream 114 b is shown being passed to a first refrigerant accumulator 117 .
  • First refrigerant accumulator 117 may also be fed by one or more first refrigerant component make-up streams 116 .
  • FIG. 1 shows first and second first refrigerant component make-up streams 116 a , 116 b which may replenish components that have been removed from or leaked from the first refrigerant inventory in the first refrigerant circuit 100 .
  • Selective addition of first and second components may alter the composition of the first mixed refrigerant.
  • a first refrigerant drain stream may be provided.
  • the first refrigerant can be removed from the (first) cooled compressed first refrigerant stream 114 a via first refrigerant drain stream 119 .
  • This is preferred if it is desired to remove both light and heavy components from the inventory of the first mixed refrigerant in the first refrigerant circuit 100 .
  • one or more first refrigerant drain streams may be removed from first refrigerant accumulator 117 . If the first refrigerant drain stream is overhead from accumulator 117 , light, vaporous components of the first mixed refrigerant may be preferentially removed. If the first refrigerant drain stream is at or near the bottom of accumulator 117 , heavy, liquid components of the first mixed refrigerant may be preferentially removed. In this way, it is possible to adjust the composition of the first mixed refrigerant.
  • the first mixed refrigerant can be drawn from first refrigerant accumulator 117 as first refrigerant feed stream 118 , which may be cooled in cooling device 115 c , such as an ambient cooler, to provide the compressed first refrigerant stream 120 .
  • the compressed first refrigerant stream 120 is passed to first heat exchanger 125 as a (second) first stream.
  • the compressed first refrigerant stream 120 is passed through a (second) first stream tube 121 in the first heat exchanger 125 , in which it is cooled to provide a first cooled first refrigerant stream 130 .
  • the first cooled first refrigerant stream 130 is divided into first portion 130 a and second portion 130 b , for instance using a splitter such as a T-piece, maintaining the composition of the first and second portions the same as the composition of the first cooled first refrigerant stream 130 .
  • the first portion 130 a of the first cooled first refrigerant stream 130 is passed through the first expansion device 135 , e.g. in the form of a Joule-Thomson valve, to the cold end of the shell side of the first heat exchanger 125 , in which it is allowed to evaporate at an intermediate pressure level.
  • the evaporating first refrigerant extracts heat from the two first streams (compressed first refrigerant stream 120 and second refrigerant stream 220 ) flowing through the tubes 121 and 221 .
  • the remainder of the first cooled first refrigerant stream 130 i.e. second portion 130 b of the first cooled first refrigerant stream 130 is passed to the second heat exchanger 145 .
  • the second portion 130 b is passed to a second first refrigerant tube 131 arranged in the second heat exchanger 145 , in which it is cooled to provide a further cooled first refrigerant stream 160 .
  • the further cooled first refrigerant stream 160 is passed to the second expansion device 165 , such as a Joule-Thomson valve, to provide second expanded first refrigerant stream 170 .
  • the second expanded first refrigerant stream 170 is at a lower pressure than the first expanded first refrigerant stream 140 .
  • the second expanded first refrigerant stream 170 is passed to the cold end of the shell side of the second heat exchanger 145 , in which it is allowed to evaporate at low pressure.
  • the evaporating first refrigerant extracts heat from the second streams (e.g. hydrocarbon stream 50 and/or cooled second refrigerant stream 230 ) flowing through the tubes 51 and 231 , and from the second portion 130 b of the first cooled first refrigerant stream 130 in tube 131 .
  • Evaporated first mixed refrigerant at low refrigerant pressure is removed from the shell side of the second heat exchanger 145 as second warmed first refrigerant stream 180 .
  • the second warmed first refrigerant stream 180 may be passed to second knock out drum 185 to remove any liquid phase prior to passing the gaseous components of the second warmed first refrigerant stream 180 to first compressor 105 in the form of gaseous second warmed first refrigerant stream 180 ′.
  • the first mixed refrigerant is compressed to elevated pressure to provide compressed stream 110 .
  • first coolers 115 may be water coolers, rather than air coolers and, if required, can be supplemented by heat exchangers in which a further coolant is used.
  • the first and/or second expansion devices 135 , 165 can be replaced or supplemented by expansion turbines.
  • the first and second heat exchangers 125 , resp. 145 can be independently selected from spool wound or plate-fin heat exchangers, although the above description has been made with specific reference to spool wound type heat exchangers.
  • the hydrocarbon stream may be cooled in both first and second heat exchangers.
  • FIG. 2 discloses a line-up comprising two, i.e. first and second, first heat exchangers 125 a , 125 b , both operating at intermediate pressure, and one second heat exchanger 145 operating at low pressure.
  • a hydrocarbon feed stream 20 is provided and passed to the second first heat exchanger 125 b , where it is cooled.
  • the hydrocarbon feed stream 20 has preferably been pre-treated to remove undesirable components such as acid gases, as will be discussed further below.
  • the second first heat exchanger 125 b can be used to knock out any (remaining) H 2 O present in the hydrocarbon feed stream 20 .
  • the hydrocarbon feed stream 20 may be present in a first heat exchanger hydrocarbon stream tube 21 , and cooled against the first mixed refrigerant in the shell side of the second first heat exchanger 125 b an intermediate pressure level.
  • the second first heat exchanger 125 b can be a kettle heat exchanger, a spoolwound or a fin plate type heat exchanger as desired.
  • the first mixed refrigerant is allowed to evaporate as it cools the hydrocarbon feed stream 20 , to provide a second first warmed first refrigerant stream 150 b , and a cooled hydrocarbon feed stream 30 as a cooled first stream.
  • the second first warmed first refrigerant stream 150 b is provided by a second first expanded first refrigerant stream 140 b , by passing a third portion 130 c of the first cooled first refrigerant stream 130 through a (second) first expansion device 135 b , such as a Joule-Thomson valve or turbine expander.
  • a (second) first expansion device 135 b such as a Joule-Thomson valve or turbine expander.
  • the first cooled first refrigerant stream 130 is provided as a first cooled stream from a different heat exchanger, in this case first first heat exchanger 125 a , which may be a coil wound heat exchanger or fin plate type heat exchanger.
  • the first first heat exchanger 125 a cools one first stream (in the form of a second refrigerant stream 220 ) as well as the compressed first refrigerant stream 120 , in a similar manner to the embodiment of FIG. 1 .
  • first streams are provided, the hydrocarbon feed stream 20 and the second refrigerant stream 220 , and are cooled in separate first heat exchangers 125 a , 125 b.
  • a first first warmed first refrigerant stream 150 a is provided from the shell side of the first first heat exchanger 125 a . This can be combined with the (second) first warmed first refrigerant stream 150 b from the second first heat exchanger, and passed to the intermediate pressure stage suction inlet of the first compressor 105 .
  • the first compressor 105 provides a compressed stream 110 , which can be passed to one or more first coolers 115 , such as ambient air or water coolers which remove heat of compression together with at least a part of the heat absorbed form the first and second streams (e.g. streams represented by 120 , 50 , 130 b , 230 ) and the self cooling of the first mixed refrigerant.
  • the first coolers 115 provide a cooled first compressed refrigerant stream 114 which can be passed to first accumulator 117 .
  • the composition of the first mixed refrigerant inventory can be adjusted in the first accumulator 117 in a similar manner to the embodiment of FIG. 1 .
  • the first accumulator 117 provides the compressed first refrigerant stream 120 to the first first heat exchanger 125 a.
  • this may be passed to a natural gas liquids (NGL) recovery column 45 , such as a fractionation column or scrub column, e.g. in the form of a demethanizer, which provides a liquid bottoms stream such as a natural gas liquids stream 40 from at or near the bottom of the column, and an overhead gaseous stream, which is the hydrocarbon stream 50 .
  • NNL natural gas liquids
  • the hydrocarbon stream 50 is cooled in the second heat exchanger 145 as a second stream, together with the cooled second refrigerant stream 230 as a further second stream, and the second portion 130 b of the first cooled first refrigerant stream 130 in a similar manner to the embodiment of FIG. 1 .
  • the cooled hydrocarbon stream 60 which is a cooled second stream provided by the second heat exchanger 145 , can be passed to a first separator 65 .
  • First separator 65 provides a fraction of the cooled hydrocarbon stream 60 in the form of methane rich stream 70 overhead and a methane-depleted bottoms stream 80 .
  • the methane-depleted bottoms stream 80 can be passed to the NGL recovery column 45 as a reflux stream.
  • the methane-depleted bottoms stream 80 can be sent first to a reflux knock-out vessel (not shown) to remove the gaseous fraction.
  • the liquid portion of the methane-depleted bottoms stream can then be pressurised by reflux stream pump 75 , to provide (pressurised) methane-depleted bottoms stream 80 a which can be fed to NGL recovery column 45 at or slightly above the column operating pressure.
  • the methane depleted bottoms stream 80 can be returned to the upper part of fractionating column 45 .
  • the reflux stream can be provided at a lower temperature compared to a line-up where this pre-cooling is not carried out.
  • the temperature of this reflux determines the upper limit of the temperature of the cooled hydrocarbon stream 60 supplied to the NGL recovery column 45 .
  • This allows the provision of a more efficient process, because the methane rich stream 70 withdrawn from the top of NGL recovery column 45 can be cooled, and preferably partly condensed, at a much lower temperature.
  • the temperature at the cold end of the second heat exchanger 145 can be much lower.
  • the temperature to which the first mixed refrigerant is cooled is much lower and this results in a lower circulation rate of the refrigerant.
  • the methane rich stream 70 can then be passed to one or more main heat exchangers 85 , in which it can be cooled and at least partially, preferably fully, liquefied in a main heat exchanger methane rich stream tube 71 , against the second refrigerant in the shell side of the main heat exchanger 85 .
  • the operation of the second refrigerant which can be a second mixed refrigerant in a second refrigerant circuit, is known to those skilled in the art. An example of the operation of the second refrigerant can be found in U.S. Pat. No. 6,370,910.
  • the main heat exchanger 85 may be a main cryogenic heat exchanger.
  • the main heat exchanger 85 provides an at least partially, preferably fully, liquefied stream in the form of partially, preferably fully, liquefied hydrocarbon stream 90 .
  • the pressure of the at least partially, preferably fully, liquefied hydrocarbon stream 90 can be reduced in an end flash expansion device 87 , such as a Joule-Thomson valve and/or an expander, to provide an expanded hydrocarbon stream 91 .
  • an end flash expansion device 87 such as a Joule-Thomson valve and/or an expander
  • the expanded hydrocarbon stream 91 can be passed to an end flash separation vessel 95 , to provide an end flash stream 97 and a liquefied hydrocarbon product stream 99 .
  • the liquefied hydrocarbon product stream 99 will be an LNG stream.
  • the methods and apparatuses of cooling described herein are controlled using an advanced process controller.
  • the model used in the controller is based upon predictive control to determine simultaneously control actions for a set of manipulated variables in order to optimise at least one of a set of parameters to be optimized whilst controlling at least one or a set of controlled variables.
  • the set of manipulated variables comprises:
  • the advanced process controller may advantageously give more weight to the device which has the lowest pressure change across it, such that it provides the lowest temperature reduction of the first mixed refrigerant.
  • the setting of the first and second expansion devices 135 , 165 can be changed by an actuator operated by a control signal from the advanced process controller. Such a controller may also instruct actuators on one or more of the first drain stream and one or more first refrigerant component make-up streams, via a control signal, to adjust the composition of the first mixed refrigerant inventory in the first refrigerant circuit 100 .
  • any manipulation of the composition of the first mixed refrigerant inventory can be carried out via first refrigerant accumulator 117 .
  • the composition of the first mixed refrigerant inventory in the first refrigerant circuit 100 can be varied, the composition of the first mixed refrigerant in the compressed first refrigerant stream 120 and one or preferably both of the first warmed first refrigerant stream 150 and the second warmed first refrigerant stream 180 are identical.
  • the composition of the first refrigerant stream passing through the first expansion device 135 is identical to the composition of the first refrigerant stream passing through the second expansion device 165 .
  • the set of controlled variables comprises one or more of the group:
  • the temperature of at least one of the one or more cooled second streams (e.g. in the form of cooled hydrocarbon stream 60 and/or further cooled second main refrigerant stream 240 ), preferably the temperature of the cooled hydrocarbon stream 60 , the temperature difference between the first warmed first refrigerant stream 150 and at least one of (i) the compressed first refrigerant stream 120 and (ii) the first stream (e.g. in the form of the hydrocarbon feed stream 20 and/or second refrigerant stream 220 ), the temperature difference between the second warmed first refrigerant stream 180 and at least one of (i) the second portion 130 b of the first cooled first refrigerant stream 130 and (ii) one of the one or more second streams (e.g.
  • any of 30 , 50 , 230 in the form of the cooled first stream (cooled hydrocarbon feed stream 30 and/or cooled second refrigerant stream 230 ) and/or a stream derived from the cooled first stream 30 which will be referred to as “dependent stream”, at least one of (i) the temperature difference between the first cooled first refrigerant stream 130 and the first expanded first refrigerant stream 140 and (ii) the temperature difference between the further cooled first refrigerant stream 160 and the second expanded first refrigerant stream 170 , and the power consumed by the one or more first compressors 105 .
  • the second and third controlled variables listed above seek to define the change in temperature between the warmed first refrigerant exiting the first or second heat exchanger and at least one of the streams entering the warm end of that exchanger.
  • the difference in temperature between the first warmed first refrigerant stream 150 and the temperature of at least one of the streams at the warm end of the first heat exchanger 125 is determined.
  • Said stream at the warm end of the first heat exchanger 125 can be selected from the group consisting of the first stream and the compressed first refrigerant stream 120 .
  • the first stream may be preferably selected from the group consisting of the hydrocarbon feed stream 20 (as discussed in relation to FIG. 2 ) and the second refrigerant stream 220 in a second refrigerant circuit (not shown). It is preferred that the combination of streams giving rise to the lowest temperature difference is given relatively more weight as controlled variable.
  • the difference in temperature between the second warmed first refrigerant stream 180 and the temperature of at least one of the streams at the warm end of the second heat exchanger 145 is determined.
  • Said stream at the warm end of the second heat exchanger 145 can be selected from the group consisting of the second portion 130 b of the first cooled first refrigerant stream 130 and one of the one or more second streams (for which can be used one or more of streams 30 , 50 , 230 ) in the form of the cooled first stream 30 , 230 and/or the dependent stream derived from the cooled first stream. It is preferred that the temperature difference of the combination of streams giving rise to the lowest temperature difference is given relatively more weight as controlled variable.
  • the temperatures and temperature differences required to determine the first four controlled variables listed above can be measured by temperature sensors monitoring the temperatures in the relevant streams.
  • the temperature sensors can transmit temperature sensor signals to the advanced process controller, which operates the control method described herein.
  • control signals can be sent to, for instance, actuators for the expansion devices and/or first refrigerant drain and component make-up streams, in order to change one or more of the manipulated variables.
  • the power requirements of the first compressor(s) can be measured by sensors in the compressor(s) or corresponding first compressor driver(s), and transmitted to the advanced process controller.
  • the set of parameters to be optimised comprises the production rate of the cooled hydrocarbon stream and/or the cooling efficiency of the first refrigerant circuit.
  • the production rate of the cooled hydrocarbon stream may be determined by measuring the mass flow, or a related property, for instance using a flow sensor.
  • the cooling efficiency of the first refrigerant circuit can be calculated by known techniques based upon the power requirements of the first compressors in relation to the mass of cooled hydrocarbon stream 60 produced over time.
  • model predictive control is that future behaviour is predicted using a model and available measurements of the controlled variables.
  • the controller outputs are calculated so as to optimize a performance index, which can be a linear or quadratic function of the predicted errors and the calculated future control moves.
  • a performance index can be a linear or quadratic function of the predicted errors and the calculated future control moves.
  • the control calculations are repeated and the predictions updated based upon current measurements.
  • a suitable model is one which comprises a set of empirical step-response models expressing the effects of a step-response of a manipulated variable on the controlled variables.
  • An optimum value of the parameter to be optimised can be obtained from a separate optimization step, or the variable to be optimized can be included in the performance function.
  • step changes of the manipulated variables on the variable to be optimised and on the controlled variables is first determined.
  • This operation provides a set of step-response coefficients.
  • the set of step response coefficients forms the basis of the model predictive control of the cooling process.
  • the performance index can include two terms, a first term representing the sum over the future control moves of the predicted error for each control move and a second term representing the sum over the future control moves of the change in the manipulated variables for each control move.
  • the predicted error is the difference between the predicted value of the controlled variable and a reference value of the controlled variable.
  • the predicted errors are multiplied with a weighting factor, and the changes in the manipulated variables for a control move are multiplied with a move suppression factor.
  • the performance index would be linear.
  • the terms may be a sum of squared terms, in which case the performance index is quadratic.
  • Constraints can be set on the manipulated variables, the change in manipulated variables and on controlled variables. This results in a separate set of equations that are solved simultaneously with the minimization of the performance index.
  • the parameters to be optimized are included as controlled variables in the predicted error for each control move and the optimization gives a reference value for the controlled variables.
  • the reference values of the controlled variables are pre-determined steady state values which remain constant.
  • the performance index is minimized taking into account the constraints to give the values of the manipulated variables for the future control moves. However, only the next control move is executed. Then the calculation of the performance index for future moves starts again.
  • the models with the step response coefficients and the equations for model predictive control can be part of a computer program which is executed in order to control the cooling process.
  • a computer loaded with such a program which can handle model predictive control is called an advanced process controller.
  • Basic program packages, absent of the particular model predictive control disclosed herein, are commercially available and will be known to the skilled person.
  • the methods and apparatuses described herein benefit from the advantageous selection of the sets of the manipulated and controlled variables.
  • the manipulated variable comprising the composition of the inventory of the first mixed refrigerant in the first refrigerant circuit 100 can comprise manipulating one or more of the methane, ethane and propane content in the first refrigerant inventory.
  • LNG liquefied natural gas
  • the hydrocarbon stream may thus be any suitable gas stream to be cooled and optionally liquefied, but is suitably a natural gas stream obtained from natural gas or petroleum reservoirs.
  • the natural gas stream may also be obtained from another source, also including a synthetic source such as a Fischer-Tropsch process.
  • a natural gas stream is a hydrocarbon composition comprised substantially of methane.
  • the hydrocarbon feed stream comprises at least 50 mol % methane, more preferably at least 80 mol % methane.
  • Hydrocarbon compositions such as natural gas may also contain non-hydrocarbons such as H 2 O, N 2 , CO 2 , Hg, H 2 S and other sulphur compounds, and the like.
  • the natural gas may be pre-treated before cooling and any liquefying. This pre-treatment may comprise reduction and/or removal of undesired components such as CO 2 and H 2 S or other steps such as early cooling, pre-pressurizing or the like. As these steps are well known to the person skilled in the art, their mechanisms are not further discussed here.
  • hydrocarbon stream may also include a composition prior to any treatment, such treatment including cleaning, dehydration and/or scrubbing, as well as any composition having been partly, substantially or wholly treated for the reduction and/or removal of one or more compounds or substances, including but not limited to sulphur, sulphur compounds, carbon dioxide, water, Hg, and one or more C 2 + hydrocarbons.
  • treatment including cleaning, dehydration and/or scrubbing, as well as any composition having been partly, substantially or wholly treated for the reduction and/or removal of one or more compounds or substances, including but not limited to sulphur, sulphur compounds, carbon dioxide, water, Hg, and one or more C 2 + hydrocarbons.
  • natural gas may contain varying amounts of hydrocarbons heavier than methane such as in particular ethane, propane and the butanes, and possibly lesser amounts of pentanes and aromatic hydrocarbons.
  • hydrocarbons heavier than methane such as in particular ethane, propane and the butanes, and possibly lesser amounts of pentanes and aromatic hydrocarbons.
  • the composition varies depending upon the type and location of the gas.
  • C 2 + hydrocarbons can be separated from, or their content reduced in a hydrocarbon feed stream by a demethaniser, which will provide an overhead hydrocarbon stream which is methane-rich and a bottoms methane-lean stream comprising most of the C 2 + hydrocarbons.
  • the bottoms methane-lean stream can then be passed to further separators to provide Liquefied Petroleum Gas (LPG) and condensate streams.
  • LPG Liquefied Petroleum Gas
  • the hydrocarbon stream so produced can be cooled. This is shown e.g. by line 50 in FIG. 2 above.
  • the cooling could be provided by a number of methods known in the art, including so-called double mixed refrigerant (DMR) processes, such as but not limited to the processes explained above and in e.g. U.S. Pat. No. 5,826,444; U.S. Pat. No. 6,041,619; U.S. Pat. No. 6,105,389; U.S. Pat. No. 7,096,688; U.S. Pat. No.
  • DMR double mixed refrigerant
  • the hydrocarbon stream is passed against one or more refrigerant streams in one or more refrigerant circuits.
  • a refrigerant circuit can comprise one or more compressors to compress an at least partly evaporated refrigerant stream to provide a compressed refrigerant stream.
  • the compressed refrigerant stream can then be cooled in a cooler, such as an air or water cooler, to provide the refrigerant stream.
  • the compressors can be driven by one or more turbines.
  • the cooling of the hydrocarbon stream can be carried out in one or more stages.
  • Initial cooling also called pre-cooling or auxiliary cooling, can be carried out using a pre-cooling mixed refrigerant of a pre-cooling refrigerant circuit, in two or more pre-cooling heat exchangers, to provide a cooled hydrocarbon stream.
  • the cooled hydrocarbon stream us preferably partially liquefied, such as at a temperature below 0° C.
  • such pre-cooling heat exchangers could comprise a pre-cooling stage, with any subsequent cooling being carried out in one or more main heat exchangers to liquefy a fraction of the hydrocarbon stream in one or more main and/or sub-cooling cooling stages.
  • the first and second heat exchangers discussed in the embodiments above may be such pre-cooling heat exchangers in a pre-cooling stage, and the first mixed refrigerant may be a pre-cooling mixed refrigerant.
  • each cooling stage may comprise one to five heat exchangers.
  • the or a fraction of a hydrocarbon stream and/or the mixed refrigerant may not pass through all, and/or all the same, the heat exchangers of a cooling stage.
  • the hydrocarbon cooling process may comprise a single cooling stage.
  • the hydrocarbon may be cooled and liquefied in a method comprising two or three cooling stages.
  • a pre-cooling stage is preferably intended to reduce the temperature of a hydrocarbon feed stream to below 0° C., usually in the range ⁇ 20° C. to ⁇ 70° C.
  • a main cooling stage is preferably separate from the pre-cooling stage. That is, the main cooling stage comprises one or more separate main heat exchangers.
  • the main cooling stage may be refrigerated using the second refrigerant stream discussed hereinabove.
  • a main cooling stage is preferably intended to reduce the temperature of a hydrocarbon stream, usually at least a fraction of a hydrocarbon stream cooled by a pre-cooling stage, to below ⁇ 100° C.
  • Heat exchangers for use as the two or more pre-cooling or any main heat exchangers are well known in the art.
  • the pre-cooling heat exchangers are preferably shell and tube heat exchangers.
  • At least one of any of the main heat exchangers is preferably a spool-wound cryogenic heat exchanger known in the art.
  • a heat exchanger could comprise one or more cooling sections within its shell, and each cooling section could be considered as a cooling stage or as a separate ‘heat exchanger’ to the other cooling locations.
  • one or both of the mixed pre-cooling refrigerant stream and any mixed main refrigerant stream can be passed through one or more heat exchangers, preferably two or more of the pre-cooling and main heat exchangers described hereinabove, to provide cooled mixed refrigerant streams.
  • the mixed refrigerant in a mixed refrigerant circuit may be formed from a mixture of two or more components selected from the group comprising: nitrogen, methane, ethane, ethylene, propane, propylene, butanes, pentanes, etc.
  • the present invention may involve the use of one or more other refrigerants, in separate or overlapping refrigerant circuits or other cooling circuits.
  • a mixed refrigerant or a mixed refrigerant stream as referred to herein comprises at least 5 mol % of two different components. More preferably, the mixed refrigerant comprises two or more of the group comprising: methane, ethane, ethylene, propane, propylene, butanes and pentanes.
  • a common composition for a mixed refrigerant can be:
  • the total composition comprises 100 mol %.
  • the cooled hydrocarbon stream such as a cooled natural gas stream can be further cooled to provide a liquefied hydrocarbon stream, such as an LNG stream.
  • the cooled hydrocarbon stream provided by the method and apparatus described herein can be used to provide a liquefied hydrocarbon stream which can be stored in one or more storage tanks.
  • the liquefied hydrocarbon stream may be further processed, if desired.
  • the obtained liquefied hydrocarbon may be depressurized by means of a Joule-Thomson valve or by means of a cryogenic turbo-expander.
  • the liquefied hydrocarbon stream is passed through an end gas/liquid separator such as an end-flash vessel to provide an end-flash gas stream overhead and a liquid bottom stream, the latter optionally for storage in a storage tank as the liquefied product, such as LNG.
  • the end-flash gas can be compressed in an end-flash gas compressor to provide a compressed end-flash gas stream and cooled to provide a cooled end-flash gas stream, which can be passed to one or more fuel gas headers, or for export as fuel gas.

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019110770A1 (en) 2017-12-07 2019-06-13 Shell Internationale Research Maatschappij B.V. Method of operating a liquefied natural gas production facility
WO2019110769A1 (en) 2017-12-07 2019-06-13 Shell Internationale Research Maatschappij B.V. Compact lng production train and method
US10481018B2 (en) * 2016-04-19 2019-11-19 General Electric Company Evaluating performance of a fluid transport system using limited sensor data
WO2024008330A1 (en) * 2022-07-04 2024-01-11 Nuovo Pignone Tecnologie - S.R.L. Gas liquefaction system with multiple refrigerant cycles

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103542692B (zh) * 2012-07-09 2015-10-28 中国海洋石油总公司 基于缠绕管式换热器的非常规天然气液化系统
IN2015DN03309A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 2012-11-16 2015-10-09 Exxonmobil Upstream Res Co
AU2013375185B2 (en) * 2013-01-24 2016-03-31 Exxonmobil Upstream Research Company Liquefied natural gas production
MY190843A (en) * 2016-03-10 2022-05-12 Jgc Corp Method of determining mixed refrigerant composition for natural gas liquefying apparatus
RU2645095C1 (ru) * 2017-04-03 2018-02-15 Общество с ограниченной ответственностью "Научно-исследовательский институт природных газов и газовых технологий - Газпром ВНИИГАЗ" Способ частичного сжижения природного газа
AU2020450354B2 (en) * 2020-05-27 2024-03-07 Chiyoda Corporation Method and system for determining operating conditions of liquefied natural gas plant

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4274849A (en) * 1974-11-21 1981-06-23 Campagnie Francaise d'Etudes et de Construction Technip Method and plant for liquefying a gas with low boiling temperature
US5108476A (en) * 1990-06-27 1992-04-28 Union Carbide Industrial Gases Technology Corporation Cryogenic air separation system with dual temperature feed turboexpansion
US5826444A (en) * 1995-12-28 1998-10-27 Institut Francais Du Petrole Process and device for liquefying a gaseous mixture such as a natural gas in two steps
US20040255615A1 (en) * 2003-01-31 2004-12-23 Willem Hupkes Process of liquefying a gaseous, methane-rich feed to obtain liquefied natural gas
US20050113468A1 (en) * 2003-10-16 2005-05-26 Beatrice Fischer Natural gas liquefaction and conversion method
US20090025422A1 (en) * 2007-07-25 2009-01-29 Air Products And Chemicals, Inc. Controlling Liquefaction of Natural Gas

Family Cites Families (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2074594B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) * 1970-01-08 1973-02-02 Technip Cie
US5139548A (en) * 1991-07-31 1992-08-18 Air Products And Chemicals, Inc. Gas liquefaction process control system
MY118329A (en) 1995-04-18 2004-10-30 Shell Int Research Cooling a fluid stream
FR2764972B1 (fr) 1997-06-24 1999-07-16 Inst Francais Du Petrole Procede de liquefaction d'un gaz naturel a deux etages interconnectes
US5791160A (en) * 1997-07-24 1998-08-11 Air Products And Chemicals, Inc. Method and apparatus for regulatory control of production and temperature in a mixed refrigerant liquefied natural gas facility
EG22293A (en) 1997-12-12 2002-12-31 Shell Int Research Process ofliquefying a gaseous methane-rich feed to obtain liquefied natural gas
FR2778232B1 (fr) 1998-04-29 2000-06-02 Inst Francais Du Petrole Procede et dispositif de liquefaction d'un gaz naturel sans separation de phases sur les melanges refrigerants
TW477890B (en) * 1998-05-21 2002-03-01 Shell Int Research Method of liquefying a stream enriched in methane
TW480325B (en) 1999-12-01 2002-03-21 Shell Int Research Plant for liquefying natural gas
FR2829569B1 (fr) 2001-09-13 2006-06-23 Technip Cie Procede de liquefaction de gaz naturel, mettant en oeuvre deux cycles de refrigeration
AU2007275118B2 (en) 2006-07-21 2010-08-12 Shell Internationale Research Maatschappij B.V. Method and apparatus for liquefying a hydrocarbon stream
AU2007286291B2 (en) * 2006-08-14 2010-08-12 Shell Internationale Research Maatschappij B.V. Method and apparatus for cooling a hydrocarbon stream
JP5530180B2 (ja) 2006-10-11 2014-06-25 シエル・インターナシヨネイル・リサーチ・マーチヤツピイ・ベー・ウイ 炭化水素流を冷却する方法及び装置
EP1921406A1 (en) * 2006-11-08 2008-05-14 Honeywell Control Systems Ltd. A process of liquefying a gaseous methane-rich feed for obtaining liquid natural gas
CN101688752B (zh) 2007-07-12 2012-09-05 国际壳牌研究有限公司 用于使烃流冷却的方法和装置
US20100293996A1 (en) * 2007-11-16 2010-11-25 Michiel Gijsbert Van Aken Method and apparatus for liquefying a hydrocarbon stream and floating vessel or offshore platform comprising the same
CN102405389B (zh) * 2008-02-08 2014-12-03 国际壳牌研究有限公司 用于冷却低温换热器的方法和设备以及使烃流液化的方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4274849A (en) * 1974-11-21 1981-06-23 Campagnie Francaise d'Etudes et de Construction Technip Method and plant for liquefying a gas with low boiling temperature
US5108476A (en) * 1990-06-27 1992-04-28 Union Carbide Industrial Gases Technology Corporation Cryogenic air separation system with dual temperature feed turboexpansion
US5826444A (en) * 1995-12-28 1998-10-27 Institut Francais Du Petrole Process and device for liquefying a gaseous mixture such as a natural gas in two steps
US20040255615A1 (en) * 2003-01-31 2004-12-23 Willem Hupkes Process of liquefying a gaseous, methane-rich feed to obtain liquefied natural gas
US20050113468A1 (en) * 2003-10-16 2005-05-26 Beatrice Fischer Natural gas liquefaction and conversion method
US20090025422A1 (en) * 2007-07-25 2009-01-29 Air Products And Chemicals, Inc. Controlling Liquefaction of Natural Gas

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10481018B2 (en) * 2016-04-19 2019-11-19 General Electric Company Evaluating performance of a fluid transport system using limited sensor data
WO2019110770A1 (en) 2017-12-07 2019-06-13 Shell Internationale Research Maatschappij B.V. Method of operating a liquefied natural gas production facility
WO2019110769A1 (en) 2017-12-07 2019-06-13 Shell Internationale Research Maatschappij B.V. Compact lng production train and method
WO2024008330A1 (en) * 2022-07-04 2024-01-11 Nuovo Pignone Tecnologie - S.R.L. Gas liquefaction system with multiple refrigerant cycles

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