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
  • 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
  • F25J1/0002—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
  • F25J1/003—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
  • F25J1/0032—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
  • F25J1/0042—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 the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by liquid expansion with extraction of work
• • 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
  • F25J1/003—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
  • F25J1/0057—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 after expansion of the liquid refrigerant stream with extraction of work
• • 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
  • F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
  • F25J1/008—Hydrocarbons
  • F25J1/0092—Mixtures of hydrocarbons comprising possibly also minor amounts of nitrogen
• • 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
  • F25J1/0239—Purification or treatment step being integrated between two refrigeration cycles of a refrigeration cascade, i.e. first cycle providing feed gas cooling and second cycle providing overhead gas cooling
  • F25J1/0241—Purification or treatment step being integrated between two refrigeration cycles of a refrigeration cascade, i.e. first cycle providing feed gas cooling and second cycle providing overhead gas cooling wherein the overhead cooling comprises providing reflux for a 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
  • 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
• • 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
  • F25J1/0258—Construction and layout of liquefaction equipments, e.g. valves, machines vertical layout of the equipments within in the cold box
• • 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
  • F25J1/0263—Details of the cold heat exchange system using different types of heat exchangers
• • 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.
  • F25J1/0295—Shifting of the compression load between different cooling stages within a refrigerant cycle or within a cascade refrigeration system
• • 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
  • F25J2205/50—Processes or apparatus using other separation and/or other processing means using absorption, i.e. with selective solvents or lean oil, heavier CnHm and including generally a regeneration step for the solvent or lean oil
• • 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
  • F25J2210/00—Processes characterised by the type or other details of the feed stream
  • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
• • 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
  • F25J2210/00—Processes characterised by the type or other details of the feed stream
  • F25J2210/60—Natural gas or synthetic natural gas [SNG]
• • 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
  • F25J2210/00—Processes characterised by the type or other details of the feed stream
  • F25J2210/62—Liquefied natural gas [LNG]; Natural gas liquids [NGL]; Liquefied petroleum gas [LPG]
• • 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
• • 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
• • 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
  • F25J2240/00—Processes or apparatus involving steps for expanding of process streams
  • F25J2240/30—Dynamic liquid or hydraulic expansion with extraction of work, e.g. single phase or two-phase turbine
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
  • F25J2290/62—Details of storing a fluid in a tank

Definitions

• the invention relates to a method and a plant for the production of liquefied natural gas according to the preambles of the independent claims.
• Natural gas must be cooled down to temperatures of around -160 ° C for liquefaction and pressureless storage. In this state, the liquefied natural gas can be transported economically by cargo ship or truck, since it has only 1/600 the volume of the gaseous substance at atmospheric pressure.
• Natural gas usually contains a mixture of methane and higher hydrocarbons as well as nitrogen, carbon dioxide and other undesirable components. Before liquefaction, these components have to be partially removed in order to avoid solidification during liquefaction or to meet customer requirements.
• the methods used for this, such as adsorption, absorption and cryogenic rectification, are well known.
• mixed refrigerants made from different hydrocarbon components and nitrogen are used in natural gas liquefaction.
• methods are known in which two mixed refrigerant circuits are used (Dual Mixed Refrigerant, DMR).
• DMR Dual Mixed Refrigerant
• natural gas which in addition to methane contains even higher hydrocarbons such as ethane, propane, butane, etc., but has already been suitably freed from acid gases and dried, can be subjected to a separation of the higher hydrocarbons and a subsequent liquefaction.
• the separation of the higher hydrocarbons is accompanied by a separation of benzene, which in the remaining liquefied natural gas is undesirable.
• Benzene is used as a key or marker component in corresponding processes and can also be used as an indicator component for the separation.
• the present invention therefore has the object of improving the liquefaction of natural gas using two mixed refrigerant circuits.
• the present invention proposes a method for producing liquefied natural gas and a corresponding plant according to the preambles of the respective independent claims. Refinements are the subject matter of the dependent claims and the following description.
• pressure level and "temperature level” to characterize pressures and temperatures, which is intended to express that corresponding pressures and temperatures do not have to be used in a corresponding system in the form of exact pressure or temperature values. However, such pressures and temperatures typically move in certain ranges, for example ⁇ 10% of a mean value. Corresponding pressure levels and temperature levels can be in disjoint areas or in areas that overlap. In particular, pressure levels include, for example, unavoidable or expected pressure losses. The same applies to temperature levels.
• the pressure levels specified here in bar are absolute pressures. If “expansion machines” are mentioned here, this is typically understood to mean known turboexpander that have radial impellers arranged on a shaft.
• a corresponding expansion machine can, for example, be mechanically braked or coupled to a device such as a compressor or a generator.
• An expansion of a mixed refrigerant within the scope of the present invention is typically not carried out using an expansion machine, but rather using an expansion valve.
• a “heat exchanger” for use in the context of the present invention can be designed in any conventional manner. It is used for the indirect transfer of heat between at least two fluid flows, for example, which flow countercurrently to one another, here in particular a comparatively warm feed natural gas flow or a gaseous fraction formed from it and one or more cold mixed refrigerant flows.
• a corresponding heat exchanger can be formed from a single or several parallel and / or serially connected heat exchanger sections, e.g. from one or more wound heat exchangers or corresponding sections. In addition to wound heat exchangers of the type already mentioned, other types of heat exchangers can also be used within the scope of the present invention.
• a countercurrent absorber is typically a liquid fraction ("bottom liquid”) and a gaseous fraction ("top gas”) from a lower area ("bottom”) or from an upper area ("top).
• Countercurrent absorbers are from the field of separation technology Generally known. They are used for absorption in countercurrent flow and are therefore also referred to as countercurrent columns.
• the releasing gas phase flows upwards through an absorption column.
• the receiving solution phase flows, added from above and withdrawn from below, towards the gas phase "Washed” with the solution phase.
• internals are typically provided, which for a stepwise (trays,
• a liquid flow also referred to as "absorption liquid"
• a countercurrent absorber with which components are washed out of a gaseous flow which is fed in deeper.
• feed natural gas is used below, this should be understood, as already mentioned, to mean natural gas which has, in particular, been subjected to acid gas removal and optional further processing.
• heavy hydrocarbons such as butanes and / or pentanes and hydrocarbons with six or more carbon atoms can already have been separated from the corresponding feed natural gas.
• the natural gas used is in particular anhydrous and has a methane content of, for example, more than 85% and the remainder contains in particular ethane and propane. Nitrogen, helium and other light components can also be included.
• liquefied natural gas is mentioned below, this is understood to mean a cryogenic liquid at the atmospheric boiling point of methane or below, in particular at -160 to -164 ° C, which is more than 85%, especially more than 90% methane and whose methane content is always higher than that of the feed natural gas used.
• the liquefied natural gas is significantly lower in benzene than the natural gas used and only contains benzene in a maximum content specified below.
• the natural gas used can be cooled in a first cooling step, depending on its composition, to a temperature in the range from -20 ° C to -70 ° C and then fed into the countercurrent absorber.
• the countercurrent absorber can have a sump heater. Sump liquid that separates out in the countercurrent absorber contains at least some of the higher hydrocarbons from the natural gas used. Some of the bottom liquid can be returned to the countercurrent absorber as absorption liquid and, if necessary, also partially fed to a top gas of the countercurrent absorber after it has been removed from the countercurrent absorber.
• the top gas of the countercurrent absorber is depleted in at least some of the higher hydrocarbons and is then subjected to a second cooling step which brings about the liquefaction.
• Benzene is also used here as a key component, which may be contained in the top gas of the countercurrent absorber and thus in the natural gas to be liquefied, in particular less than 1 ppm on a molar basis. The contents of other higher hydrocarbons result from this; however, these are typically less critical. Benzene is particularly critical in liquefying natural gas because it can solidify at the low temperatures used.
• mixed refrigerants are used in corresponding refrigerant circuits.
• a first mixed refrigerant (Warm Mixed Refrigerant, WMR) can be subjected to gaseous compression in the following sequence, condensed by cooling, subcooled, expanded, heated in the first heat exchanger, in particular completely evaporated, and then subjected to compression again become.
• the subcooling of the first mixture refrigerant can in particular take place in the first heat exchanger, the previous cooling in another heat exchanger.
• a second mixed refrigerant (Cold Mixed Refrigerant, CMR) in gaseous form can be subjected to compression, condensed by cooling, supercooled, expanded, heated in the second heat exchanger, in particular completely evaporated, and then subjected to compression again.
• the subcooling of the second mixed refrigerant can in particular take place in the second heat exchanger, the previous cooling in the first and the second heat exchanger.
• the first and second heat exchangers are designed in particular as coiled heat exchangers (Coil Wound Heat Exchanger, CWHE) of a type known per se, with the heating of the mixed refrigerants after their expansion taking place in particular on the jacket side, ie in a jacket space surrounding the heat exchanger tubes which the mixture refrigerant is relaxed.
• the media to be cooled are routed on the pipe side, i.e. through the appropriately provided heat exchanger pipes.
• the heat exchanger tubes are provided in bundles in corresponding heat exchangers, so that the term “tube side” or “bundle side” is used here for a corresponding current flow.
• Processes for liquefying natural gas must be flexibly adaptable to different plant capacities and operating conditions.
• the explained methods using two mixed refrigerant circuits are preferably used when large ambient temperature fluctuations lead to significantly different refrigerant condensation conditions. These can be taken into account more efficiently if a mixture of refrigerant components is used instead of a single pure component such as propane.
• a compact system layout (e.g. mandatory for offshore installations) can be achieved by minimizing the number of system components and by reducing the space between the systems, which can be determined by safety aspects.
• System components known to be dangerous include pumps for liquid hydrocarbons (risk of leakage and leakage) and all types of equipment that contain significant amounts of liquid propane.
• the present invention eliminates the problems explained by dispensing with hydrocarbon pumps and largely dispensing with propane as a refrigerant component in corresponding mixed refrigerants.
• a total of a feed natural gas of the type explained above, which contains methane and higher hydrocarbons, including benzene is in a first cooling step using a first ("warm") mixed refrigerant to a first temperature level, in particular from -20 ° C to -70 ° C, cooled and then subjected to countercurrent absorption using an absorption liquid to form a gas fraction depleted in benzene.
• the gas fraction depleted in benzene has in particular a content of less than 1 ppm on a molar basis of benzene, the content of benzene in the feed natural gas being significantly higher, for example 5 to 500 ppm.
• the gas fraction formed is enriched in methane, especially compared to the natural gas used, and depleted in the higher hydrocarbons.
• gas fraction can also be (essentially) free of hydrocarbons with five and possibly more carbon atoms, so that a depletion (essentially) to zero can take place.
• Hydrocarbons may be contained, and a sump liquid formed during countercurrent absorption can also contain certain proportions of methane.
• the degree of separation or enrichment and depletion achieved in countercurrent absorption depends on the subsequent use of appropriate fractions and the respective tolerable levels of the components mentioned.
• part of the gas fraction that is depleted in benzene (and other higher hydrocarbons) (or essentially free thereof) from the countercurrent absorption is reduced to a second temperature level of in particular in a second cooling step using a second ("cold") mixed refrigerant Cooled from -145 ° C to -165 ° C and liquefied to liquefied natural gas.
• Liquefied natural gas formed in this way can be subjected to any further processing or conditioning (expansion, subcooling, etc.).
• the first and second mixed refrigerants are low in propane (with a content of less than 5 mol percent propane) or (essentially) propane-free, and the absorption liquid for countercurrent absorption is formed from a further part of the gas fraction from countercurrent absorption, which (geodetically) condenses above the countercurrent absorption and is returned to the countercurrent absorption without pumps.
• propane with a content of less than 5 mol percent propane
• propane-free propane-free
• the absorption liquid for countercurrent absorption is formed from a further part of the gas fraction from countercurrent absorption, which (geodetically) condenses above the countercurrent absorption and is returned to the countercurrent absorption without pumps.
• the present invention reduces or eliminates the use of significant amounts of propane-containing media by the proposed measures.
• propane is considered a dangerous refrigerant due to its combination of high volatility and high molecular weight.
• a corresponding refrigerant must inevitably be conveyed using machines with an increased probability of propane escaping. This is no longer the case within the scope of the present invention, so that it is also particularly suitable for system layouts with limited installation space, e.g. modularized systems and / or floating systems, in which the floor space is limited and safety equipment requiring additional installation space is difficult to install and is beneficial.
• the absorption liquid for the countercurrent absorption is formed from the further part of the gas fraction from the countercurrent absorption, is condensed above the countercurrent absorption and is returned to the countercurrent absorption without pumps, there is no disadvantageous use of pumps with the problems explained for this medium (possibly containing propane) required.
• the invention thus creates a solution in which the use of appreciable amounts of propane-containing media is essentially dispensed with by either using propane-free or low-propane-containing mixed refrigerants beforehand or a propane-containing top gas from the countercurrent absorption is pumped free.
• propane-free or low-propane-containing mixed refrigerants beforehand or a propane-containing top gas from the countercurrent absorption is pumped free.
• a countercurrent absorber is advantageously used in the countercurrent absorption, which is operated with a top condenser arranged above an absorption area of the countercurrent absorber, the top condenser being used to condense the further part of the gas fraction.
• An “absorption area” is to be understood here as the area with internals as explained above.
• the top condenser can be integrated into the countercurrent absorber or at least partially arranged within the countercurrent absorber.
• An integrated head condenser comprises a heat exchange structure in a common column jacket, in which mass transfer structures of the type explained above are also arranged, the heat exchange structure, for example a cooling coil or the like, being separated from an area containing the mass transfer structures, in particular by a liquid dust base or a liquid-tight base. The latter allows a controlled return of condensate to the area with the mass transfer structures.
• a head capacitor arranged outside, however, is not arranged in a common column jacket with the mass transfer structures.
• the first mixed refrigerant advantageously has a total of more than 90 mol percent ethane, isobutane and n-butane and a total of less than 10, preferably less than 5 mol percent nitrogen, methane, propane and hydrocarbons with five or more carbon atoms.
• the small amount of propane proves to be unproblematic.
• the second mixed refrigerant advantageously has a total of more than 98 mol percent nitrogen, methane and ethane and a total of less than 2 mol percent propane and higher hydrocarbons.
• a first heat exchanger is advantageously used in the first cooling step, the first mixed refrigerant being subjected to a gaseous, in particular single-stage, compression in a first mixed refrigerant circuit, condensed by cooling, subcooled, relaxed, heated in the first heat exchanger, in particular completely evaporated, and then subjected to compaction again.
• the subcooling of the first mixed refrigerant can in particular take place in the first heat exchanger, the previous cooling in a further heat exchanger.
• the first mixed refrigerant is compressed in particular in one stage and without intermediate cooling, which would create a risk of partial condensation and the need to convey the condensate to the high-pressure side of the compressor. This disadvantage is eliminated here.
• a second heat exchanger is advantageously used in the second cooling step, the second mixed refrigerant being subjected to a gaseous, in particular multi-stage compression in a second mixed refrigerant circuit, condensed by cooling, subcooled, relaxed, heated in the second heat exchanger, in particular completely evaporated, and then subjected to compaction again.
• the subcooling of the second mixed refrigerant can in particular take place in the second heat exchanger, the previous cooling in the first and the second heat exchanger.
• the first and second heat exchangers can be designed as wound heat exchangers and, in particular, each with one or two (serial) bundles in a common jacket.
• a collector for the second mixed refrigerant which absorbs this after its condensation, can be designed in the context of the present invention in particular for a pressure that is 2 to 10 bar above an intake pressure of a compressor or a first of several compressors that occur when the second mixed refrigerant is compressed used lies.
• a series of three compressors can be used to compress the first and the second mixed refrigerant, a first of which compresses the first and the other two compress the second mixed refrigerant.
• These compressors can be designed for (almost) identical shaft outputs, i.e. 33 1/3 ⁇ 3% of the total power consumption.
• the second mixed refrigerant is advantageously used after the heating and evaporation in the second heat exchanger and before the compression in the condensation of the further part of the gas fraction from the countercurrent absorption and is further heated in the process. This results in a particularly advantageous use of this second mixed refrigerant.
• the first (but not the second) heat exchanger is advantageously used to cool the first mixed refrigerant and / or the second (and additionally the first) heat exchanger is used to cool the second mixed refrigerant. Further cooling after compression or after compression steps can take place in a known manner, for example using air or water coolers.
• an ascending gas phase is formed in an alternative, at least in part, by feeding in further feed natural gas that was not subjected to the first cooling step. This saves a reboiler, but requires a higher separation efficiency in the countercurrent absorption.
• the rising gas phase can, however can also be provided at least in part by evaporation of part of a bottom liquid formed in the countercurrent absorption.
• work-performing liquid expanders can be used at any point instead of expansion valves. This reduces energy consumption.
• the present invention is suitable for typical natural gases, so that the natural gas used can in particular contain at least 80% methane and at least 50% ethane and propane in the remaining methane-free remainder.
• the liquefied natural gas advantageously contains at least 90% methane, a methane content in the liquefied natural gas being higher than in the feed natural gas.
• the present invention also extends to a plant for the production of liquefied natural gas, for whose specific features reference is made to the corresponding independent patent claim.
• a plant for the production of liquefied natural gas for whose specific features reference is made to the corresponding independent patent claim.
• Such a system is advantageously set up to carry out a method, as was previously explained in various configurations.
• FIG. 1 illustrates a system according to an embodiment of the present invention in the form of a simplified process flow diagram.
• FIG. 2 illustrates a system according to a further embodiment of the invention in the form of a simplified process flow diagram.
• FIG. 1 a system in accordance with a particularly preferred embodiment of the present invention is shown in the form of a greatly simplified, schematic process flow diagram and denoted overall by 100.
• the plant 100 illustrated in FIG. 1 is supplied with feed natural gas NG, which is initially divided into two partial flows.
• a first partial flow is cooled in a first heat exchanger E1, which can in particular be designed as a wound heat exchanger, in a first cooling step to a first temperature level of, for example, -20 ° C to -70 ° C and then fed approximately centrally into a countercurrent absorber T1.
• the second partial flow of the feed natural gas NG which is expanded via a valve V6, is also fed into a lower region of the countercurrent absorber T 1 and rises there essentially in gaseous form.
• Gas is withdrawn from an upper region of the countercurrent absorber T1, which gas is cooled in a top condenser E2, which can for example be designed as a plate heat exchanger, and is fed into a headspace of the countercurrent absorber T 1.
• the liquid that separates here is fed back to the countercurrent absorber T 1 as a return and washes out heavier components from the feed natural gas, which are converted into a sump liquid of the countercurrent absorber T1.
• the sump liquid of the countercurrent absorber T1 can be expanded via a valve V5 and discharged from the system 100 as a heavy fraction HHC (heavy hydrocarbons).
• Head gas of the countercurrent absorber T1 i.e. a methane-rich gas fraction, on the other hand, is cooled to a liquefaction temperature in a second heat exchanger E3, which can also be designed as a wound heat exchanger, and after expansion is discharged from the system 100 as liquefied natural gas LNG via a valve V4.
• the system 100 comprises two mixed refrigerant circuits.
• a first (“warm”) mixed refrigerant WMR in gaseous form is subjected to a single-stage compression in a compressor C1 and then cooled in an air cooler and / or water cooler E4 and thereby condensed.
• Condensate can be obtained in a separator tank D1. This is first further cooled on the bundle side in the first heat exchanger E1, then expanded via a valve V1 and fed into the jacket space of the first heat exchanger E1, where it is heated, completely evaporated and then subjected to compression again.
• the first mixed refrigerant is compressed in the single-stage compressor C1 without intermediate cooling, which would create a risk of partial condensation and the need to convey the condensate to the high-pressure side of the compressor. This disadvantage is eliminated here.
• a second mixed refrigerant CMR in gaseous form is subjected to a step-by-step compression in compressors LP C2 and HP C2 and each after-cooled, for example in air coolers and / or water coolers E5 and E6. Further cooling takes place on the bundle side in the first heat exchanger E1 and then in the second heat exchanger E3. After a subsequent expansion in a valve V2, it is fed into a buffer container D2. Condensate withdrawn therefrom is expanded via a valve V3 and fed into the shell side into the second heat exchanger E2, where it is heated and completely evaporated. Before it is subjected to the compression again, the gaseous second mixed refrigerant CMR is used as refrigerant in the already mentioned top condenser E2.
• top condenser E2 which is operated using sensible heat from the second mixed refrigerant, which leaves the second heat exchanger E3 in vapor form, above the countercurrent absorber T 1, a return pump can be dispensed with.
• the return flow formed from the gas from the countercurrent absorber T1 is returned to the countercurrent absorber T 1 purely by the action of gravity.
• FIG. 2 an installation according to a further embodiment of the present invention is shown in the form of a greatly simplified, schematic process flow diagram and is designated as a whole by 200.
• a first difference to the configuration of the system 100 according to FIG. 1 is that the countercurrent absorber T 1 is not fed with a partial flow of the feed natural gas, but instead a reboiler E7 is provided, which evaporates part of the bottom liquid of the countercurrent absorber T1 and thus part the rising gas phase in the countercurrent absorber T 1 forms.
• top condenser E3 is relocated in the form of corresponding heat exchanger structures into the head space of the countercurrent absorber T1, which may save corresponding installation space.
• expansion of the liquefied natural gas LNG leaving the second heat exchanger E3 via an expansion machine X1 and a corresponding expansion of the cooled second mixed refrigerant CMR in an expansion machine X2 are provided.
• the valve V1 can also be replaced by an expansion machine X3 (not shown).

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• 2020
  • 2020-07-10 AU AU2020324268A patent/AU2020324268A1/en active Pending
  • 2020-07-10 US US17/597,181 patent/US20220307765A1/en active Pending
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