US20090188277A1 - Method and apparatus for controlling a refrigerant compressor, and method for cooling a hydrocarbon stream - Google Patents
Method and apparatus for controlling a refrigerant compressor, and method for cooling a hydrocarbon stream Download PDFInfo
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- US20090188277A1 US20090188277A1 US12/262,028 US26202808A US2009188277A1 US 20090188277 A1 US20090188277 A1 US 20090188277A1 US 26202808 A US26202808 A US 26202808A US 2009188277 A1 US2009188277 A1 US 2009188277A1
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- 239000003507 refrigerant Substances 0.000 title claims abstract description 169
- 238000000034 method Methods 0.000 title claims description 54
- 239000004215 Carbon black (E152) Substances 0.000 title claims description 52
- 229930195733 hydrocarbon Natural products 0.000 title claims description 52
- 150000002430 hydrocarbons Chemical class 0.000 title claims description 52
- 238000001816 cooling Methods 0.000 title claims description 35
- 238000010438 heat treatment Methods 0.000 claims abstract description 37
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 38
- 239000003345 natural gas Substances 0.000 claims description 17
- 238000007906 compression Methods 0.000 claims description 14
- 238000004891 communication Methods 0.000 claims description 9
- 230000008569 process Effects 0.000 claims description 9
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical group CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 claims description 8
- 239000001294 propane Substances 0.000 claims description 4
- 238000005057 refrigeration Methods 0.000 description 20
- 239000007789 gas Substances 0.000 description 7
- 239000003949 liquefied natural gas Substances 0.000 description 6
- 239000007788 liquid Substances 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 230000008859 change Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000006835 compression Effects 0.000 description 3
- 238000011144 upstream manufacturing Methods 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 1
- OFBQJSOFQDEBGM-UHFFFAOYSA-N Pentane Chemical class CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000009530 blood pressure measurement Methods 0.000 description 1
- 238000009529 body temperature measurement Methods 0.000 description 1
- 235000013844 butane Nutrition 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- MDOAAHGPXOGVQG-UHFFFAOYSA-N ethene;propane Chemical compound C=C.CCC MDOAAHGPXOGVQG-UHFFFAOYSA-N 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 239000002737 fuel gas Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical class CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- QQONPFPTGQHPMA-UHFFFAOYSA-N propylene Natural products CC=C QQONPFPTGQHPMA-UHFFFAOYSA-N 0.000 description 1
- 125000004805 propylene group Chemical group [H]C([H])([H])C([H])([*:1])C([H])([H])[*:2] 0.000 description 1
- 230000010349 pulsation Effects 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Images
Classifications
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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
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
- F04D27/02—Surge control
- F04D27/0284—Conjoint control of two or more different functions
-
- 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
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B1/00—Compression machines, plants or systems with non-reversible cycle
- F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
-
- 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
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/40—Fluid line arrangements
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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
- 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
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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
- 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
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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
- F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
- F25J1/007—Primary atmospheric gases, mixtures thereof
- F25J1/0072—Nitrogen
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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
- F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
- F25J1/008—Hydrocarbons
- F25J1/0087—Propane; Propylene
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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
- 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
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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
- 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.
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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
- 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.
- F25J1/0294—Multiple compressor casings/strings in parallel, e.g. split arrangement
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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
- 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.
- F25J1/0298—Safety aspects and control of the refrigerant compression system, e.g. anti-surge control
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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
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/01—Heaters
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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
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
- F25B2400/07—Details of compressors or related parts
- F25B2400/075—Details of compressors or related parts with parallel compressors
Definitions
- the present invention relates to a method and apparatus for controlling a refrigerant compressor.
- Such a method and apparatus may be used in a method of cooling a hydrocarbon stream, such as a natural gas stream. Accordingly, aspects of the invention relate to a method of cooling a hydrocarbon stream, and to a use of the apparatus in a process for cooling, and a use of the apparatus in a process for liquefying, a hydrocarbon feed stream.
- LNG liquefied natural gas
- the natural gas comprising predominantly methane, enters an LNG plant at elevated pressure and is pre-treated to produce a purified feed steam suitable for liquefying at cryogenic temperatures.
- the purified gas is processed through a plurality of cooling stages using heat exchangers involving one or more refrigeration circuits with compressors, to progressively reduce its temperature until liquefaction is achieved.
- Compressors for gaseous streams are used in many situations, systems and arrangements.
- a vapour recycle or recirculation line around the compressor to avoid surge.
- a compressor is said to be ‘in deep surge’ when the main flow through the compressor reverses its direction. Normally, this is related to a discharge pressure being lower than the pressure downstream of the compressor outlet. This can cause rapid pulsations in flow, which is generally termed ‘surge’.
- Refrigerant circuits are used in liquefaction systems, facilities and plants, such as for the production of a liquefied hydrocarbon stream such as liquefied natural gas (LNG).
- LNG liquefied natural gas
- the refrigerant is evaporated in one or more stages to cool the hydrocarbon stream, and one or more refrigerant compressors are used to recompress the evaporated refrigerant in one or more stages.
- Refrigerant compressors running at an effectively constant speed require relatively constant inflow of a gaseous stream to their suction side. Where the inflow of a gaseous stream falls for whatever reason below a certain minimum value, surge can occur.
- U.S. Pat. No. 4,464,720 discloses a surge control system which utilizes an algorithm to calculate a desired orifice differential pressure, and which compares the calculated result with an actual differential pressure. Pressure and temperature measurements are made on both the suction side and discharge side of a centrifugal compressor, and thus enter a control system so that the actual differential pressure is substantially equal to the desired differential pressure. A suction temperature of gas entering the centrifugal compressor is measured and used.
- the complex algorithm and values required for the calculations in U.S. Pat. No. 4,464,720 do not address any of the problems described above.
- the present invention provides a method of controlling a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream, the method at least comprising the steps of:
- the present invention also provides a method of cooling a hydrocarbon stream such as natural gas, the method at least comprising the steps of:
- the present invention also provides apparatus for controlling a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream, the apparatus at least comprising:
- At least one heat exchanger through which the refrigerant stream passes to provide a first at least partially evaporated stream and a second at least partially evaporated stream;
- a first refrigerant compressor through which passes the first compressor feed stream to provide a first compressed stream
- a combiner to combine the first and second compressed streams at a common pressure
- one or more heaters to either heat the first at least partially evaporated stream or the first compressor feed stream to control the second compressor
- the present invention also provides the use of such an apparatus in a process for cooling a hydrocarbon stream, wherein said cooling comprises passing the hydrocarbon stream through the at least one heat exchanger of the apparatus whereby heat is transferred from the hydrocarbon stream to the refrigerant stream.
- the present invention also provides the use of such an apparatus in a process for liquefying a hydrocarbon stream, wherein said liquefying comprises cooling of the hydrocarbon stream, said cooling comprising passing the hydrocarbon stream through the at least one heat exchanger of the apparatus whereby heat is transferred from the hydrocarbon stream to the refrigerant stream.
- FIG. 1 schematically shows a method of controlling a refrigerant compressor according to a first embodiment of the present invention
- FIG. 2 schematically shows a method of controlling four refrigerant compressors according to another embodiment of the present invention
- FIG. 3 schematically shows an alternative arrangement to the method shown in FIG. 2 .
- the present invention is particularly suitable for, but not limited to, controlling two or more connected and multi-stage refrigerant compressors having a plurality of inlets accepting refrigerant at different pressure levels.
- the refrigerant compressor(s) may be used in one or more refrigerant circuits for cooling, optionally including liquefying, a hydrocarbon stream such as natural gas.
- the present invention may provide an improved method of controlling one or more refrigerant compressors, in particular two or more refrigerant compressors, used for compression of a multi-pressure level refrigerant.
- the present invention is particularly suitable, but not limited to, where there are two or more refrigerant compressors in the same refrigerant circuit for different compressor feed streams, more particularly where the compressor feed streams are at different pressure levels.
- the method of the present invention allows all the refrigerant compressors to be controlled, especially to avoid surge.
- the present invention is particularly useful where a refrigerant stream is evaporated at different pressure levels, but requiring each evaporated fraction to be recompressed to a unified pressure for re-use as a refrigerant.
- the method is for controlling three or more, preferably four, refrigerant compressors, and two, three, four or five compressor feed streams based on two, three, four or five at least partly evaporated refrigerant streams respectively, wherein at least one of the evaporated refrigerant streams or at least one of the compressor feed streams is heated prior to passing through its respective refrigerant compressor.
- the method of the present invention comprises four compressor feed streams at four different pressures passing through four refrigerant compressors.
- the cooling of the hydrocarbon stream may partly or wholly liquefy the hydrocarbon stream so as to provide a liquefied hydrocarbon stream, such as LNG.
- the cooling of the hydrocarbon stream to provide the cooled hydrocarbon stream may also be followed by further cooling of the cooled hydrocarbon stream to further liquefy and/or sub-cool the cooled hydrocarbon stream.
- the or each refrigerant compressor involved in the present invention may be any suitable refrigerant compressor, optionally having two or more compression stages or pressure sections.
- Use of the term ‘refrigerant compressors’ herein extends to a single refrigerant compressor having multiple pressure sections in one casing, and able to receive two or more gaseous streams at different pressures.
- the hydrocarbon cooling or liquefying plant or facility may also involve one or more other refrigerant or other compressors not involved in the present invention.
- the first and second compressors may have a vapour recirculation line.
- the first and second compressor feed streams are a combination of at least a fraction of the vapour recirculation stream in the vapour recirculation line and the first and second at least partially evaporated refrigerant streams respectively.
- the or each recirculation line useable in the present invention may be any suitable line able to transfer a recirculation stream, which can be liquid, gaseous or mixed phase, from the discharge side of a refrigerant compressor to its suction side or a relevant suction drum.
- the or each recirculation line may be divided or separated in a manner known in the art, to supply a recirculated stream part or fraction to two or more refrigerant compressors.
- a refrigerant stream may comprise a single component such as propane or nitrogen, preferably propane, or comprise a mixture of two or more selected from the group comprising: nitrogen, methane, ethane, ethylene propane, propylene, butanes, pentanes.
- the heating of the relevant stream or streams in step (e) can be provided by any method of heating.
- the heating may involve use of one or more dedicated heaters, optionally using a fuel gas, and/or by heat exchange against a stream capable of releasing heat to the relevant stream of streams, such as a warmer stream or streams, in one or more heat exchangers.
- a cooling and/or liquefaction process or plant there are typically a number of sources of a warmer stream or streams, which could be routed to provide, when required, the heating for step (e).
- the common post-compression communication of the first and second refrigerant compressors which allows combining of the first and second compressed streams at a common pressure, can be any form of combining, either by a dedicated combiner such as a junction or T-piece, or by their common collection, for example in a cooler or accumulator.
- the method of the present invention is able to prevent surge in a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream.
- a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream.
- heating the first at least partially evaporated stream or the first compressor feed stream is to prevent surge in the second compressor
- heating the second at least partially evaporated stream or the second compressor feed stream is to prevent surge in the first compressor.
- FIG. 1 shows a simplified and general scheme 1 of a method for controlling a refrigerant compressor for a refrigerant stream.
- FIG. 1 there is also shown a method of cooling a hydrocarbon stream such as natural gas.
- a hydrocarbon feed stream 5 passes through a refrigeration zone 42 to provide a cooled hydrocarbon stream 6 , for example, having a temperature below 0° C., for example between ⁇ 10° C. and ⁇ 70° C.; optionally partly liquefied.
- the refrigeration zone 42 may be part of a liquefaction plant (not shown), wherein the cooled hydrocarbon stream 6 is subsequently fully liquefied.
- the hydrocarbon feed stream 5 is cooled by heat exchange against a refrigerant stream 40 circulating in a refrigerant circuit 2 .
- the refrigerant stream 40 passes through at least two heat exchangers ( 32 , 34 ) in the refrigeration zone 42 .
- first heat exchanger 32 from which a fraction of the refrigerant stream 40 is expanded and evaporated to provide a first at least partially evaporated stream 40 a
- second heat exchanger 34 usually at a lower pressure than that of the first heat exchanger 32 , which receives the remaining fraction of the refrigerant stream 40 from the first heat exchanger 32 , expands and evaporates the remaining fraction, to provide a second at least partially evaporated stream 40 b .
- Expansion may be performed by means of a valve upstream of the respective relevant heat exchanger, such as valve 66 upstream of the first heat exchanger 32 for the expansion in the first heat exchanger 32 and another valve (not shown) in the line between the first and second heat exchangers for the expansion in the second heat exchanger 34 .
- a valve upstream of the respective relevant heat exchanger such as valve 66 upstream of the first heat exchanger 32 for the expansion in the first heat exchanger 32 and another valve (not shown) in the line between the first and second heat exchangers for the expansion in the second heat exchanger 34 .
- Each of the evaporated refrigerant streams 40 a , 40 b are typically wholly evaporated to achieve maximum cooling in the heat exchangers 32 , 34 , although partial-evaporation is also a possibility covered by the invention.
- the first evaporated stream 40 a is at a higher pressure than the second evaporated stream 40 b although the present invention is not limited thereto.
- each of the first and second evaporated streams 40 a , 40 b are passed through first and second suction drums 16 , 18 respectively, to provide first and second compressor feed streams 20 a , 20 b respectively.
- the first and second compressor feed streams 20 a , 20 b then pass through first and second refrigerant compressors 12 , 14 respectively to provide first and second compressed streams 50 a , 50 b respectively.
- the first and second compressed streams 50 a , 50 b can be combined by a combiner 52 to provide a combined stream 60 , which can be first cooled by a first ambient heat exchanger such as one or more water and/or air coolers 54 , to provide a cooler compressed stream 60 a.
- the cooler compressed stream 60 a can be divided by a divider 56 , for instance in the form of a stream-splitter, into a continuing refrigerant stream 60 b and a vapour recirculation stream 30 passing through a vapour recirculation line 30 .
- the divider 56 may be any arrangement able to divide a stream into two or more fractions or parts, such as a manifold or dedicated unit, or more simply, a T-piece.
- the continuing refrigerant stream 60 b passes through one or more further coolers 58 , one or more accumulators 62 , one or more yet further coolers 64 , prior to expansion through an expansion valve 66 to provide the refrigerant stream 40 and recirculation through the refrigeration zone 42 .
- the vapour recirculation stream 30 may then be divided by any suitable divider 31 into two part-recirculation streams 30 a , 30 b , expanded through suitable control valves 68 a , 68 b in a manner known in the art, and subsequently combined with the first and second at least partially evaporated streams 40 a , 40 b respectively to provide first and second combined feed streams 10 a , 10 b respectively.
- vapour recirculation provides the ability to increase flow through a compressor, more particularly to maintain minimum flow where there is a reduction in the flow of evaporated refrigerant which normally forms the major component of the compressor feed stream.
- Every compressor requires a balance between its inlet pressure and outlet or discharge pressure.
- the inlet and outlet pressures are usually significantly determined by two vapour pressures; firstly from the heat exchangers using the cooling duty of the refrigerant stream, and secondly from the post-compression refrigerant accumulator.
- a benefit of the present invention is recognising that where there are two or more refrigerant compressors having a common post-compression communication, such as a common discharge, then the discharge pressure from each refrigerant compressor can affect the other refrigerant compressor. That is, using the post-compression common pressure to allow the action of one refrigerant compressor to control an associated or connected refrigerant compressor.
- the method of the present invention involves heating of the first at least partially evaporated stream 40 a and/or the first combined feed stream 10 a and/or the first compressor feed stream 20 a , to control the second compressor 14 .
- FIG. 1 shows one or more heaters such as a heat exchanger 22 in the path of the first at least partially evaporated stream 40 a , which allows heating, preferably rapid heating, of the first at least partially evaporated stream 40 a upstream of the first suction drum 16 .
- the mass flow in the subsequent first compressor feed stream 20 a is reduced.
- the same amount of cooling duty provided by the first and further coolers 54 , 58 increases the amount or degree of cooling of the flow of refrigerant therethrough, such that the temperature of refrigerant in the accumulator 62 is lower than normal, such that there is less vapour pressure created therefrom. With less vapour pressure from the accumulator 62 , this feeds back to reducing the pressure on the discharge side of the second compressor 14 , such that it is less likely to go into surge.
- heating of the second at least partially evaporated stream 40 b or the second combined feed stream 10 b or the second compressor feed stream 20 b provides control of the first compressor 12 .
- a heater such as a similar heat exchanger 24 in the path of the second at least partially evaporated stream 40 b for this purpose.
- first and second heat exchangers 22 , 24 which may comprise one or more heat exchangers in parallel, series or both.
- FIG. 2 shows a second scheme 101 involving another refrigeration circuit 102 comprising a second refrigeration zone 142 .
- the second refrigeration zone 142 may comprise two or more, such as four, separate heat exchangers, or it may comprise a single heat exchanger involving the outlet of refrigerant at different pressure levels. Such arrangements are well known in the art, and examples are shown in WO 01/44734 A2 and Wo 2005/057110 A1.
- the second refrigeration zone 142 can be for withdrawing heat from a stream, for example one or more hydrocarbon streams 100 such as a natural gas stream to be liquefied.
- hydrocarbon streams 100 such as a natural gas stream to be liquefied.
- Examples of methods for liquefying natural gas are mentioned in U.S. Pat. No. 6,389,844 and U.S. Pat. No. 6,370,910 B1 which are hereby incorporated by reference.
- a plant is described for liquefying natural gas wherein the plant comprises a pre-cooling heat exchanger having an inlet for natural gas and an outlet for cooled natural gas, and a pre-cool refrigerant circuit for removing heat from the natural gas in the pre-cooling heat exchanger.
- the second refrigeration zone 142 may be equivalent to or an extension of the first refrigeration zone 42 shown in FIG. 1 .
- cooling, preferably liquefying, of a hydrocarbon stream 100 involves two or more stages, such as a first stage to lower the temperature of the hydrocarbon stream 100 below 0° C., and a second stage to further lower the hydrocarbon stream to a temperature below ⁇ 90° or ⁇ 100° C.
- the second refrigeration zone 142 could act as the cooling for the first stage.
- the second refrigeration zone 142 has first, second, third and fourth heat exchangers 132 , 134 , 136 , 138 , and first, second, third and fourth outlets 143 , 144 , 145 , 146 , for a refrigerant stream 140 evaporated at different pressure levels, with decreasing pressure from the first outlet 143 to the fourth outlet 146 .
- the first outlet 143 is intended for gaseous refrigerant released at a high-high pressure as a first evaporated stream 140 a
- the second outlet 144 for gaseous refrigerant released at a high pressure as a second evaporated stream 140 b
- the fourth outlet 146 for gaseous refrigerant released at a low pressure as a fourth evaporated stream 140 d
- the second refrigeration zone 142 may have further outlets.
- Each evaporated stream 140 a - d is passed into a corresponding suction drum or gas/liquid separator such as knockout drums 148 a - d , from which there are respective overhead gaseous compressor feed streams 120 a - d.
- the fourth compressor feed stream 120 d passes into a first refrigerant compressor 112 d to provide a compressed stream 150 d , which is combined with the second compressor feed stream 120 b to enter a second refrigerant compressor 112 b to provide a first final compressed stream 160 .
- the first and second refrigerant compressors 112 d , 112 b may be separate refrigerant compressors, or may be in one casing, having two inlets and one or two sections to accommodate the different pressure levels of the second and fourth compressor feed streams 120 b , 120 d.
- the third compressor feed stream 120 c passes into a third refrigerant compressor 112 c , and its compressed stream 150 c is combined with the first compressor feed stream 120 a to pass into a fourth refrigerant compressor 112 a and provide a second final gaseous stream 170 .
- the third and fourth refrigerant compressors 112 a , 112 b may be separate refrigerant compressors, or may be in one casing having two inlets and different sections to accommodate the different pressures of the first and third streams 120 a , 120 c.
- the first and second final compressed streams 160 , 170 are themselves combined to form an overall combined compressed stream 180 , which is cooled by a first cooler 162 such as an ambient water and/or air cooler known in the art.
- the first cooler 162 may comprise one or more coolers in parallel, series or both, and provides a cooled compressed stream 190 .
- the cooled compressed stream 190 can be divided when desired or necessary between a continuing stream 200 and a vapour recirculation stream 130 by use of a divider 156 , e.g. in the form of a stream splitter.
- the vapour recirculation stream 130 may be divided into four separate fraction streams 130 a - d to pass through separate respective control valves 152 a - d and be combined with the evaporated refrigerant streams 140 a - d respectively to provide combined feed streams 110 a - d respectively.
- the first continuing steam 200 is further cooled and mostly or fully condensed, for example by a second cooler 172 being one or more coolers such as water and/or air coolers, which provides a cooled continuing steam 210 .
- the cooling provided by the second cooler 172 preferably fully condenses the cooled continuing stream 210 .
- the cooled continuing stream 210 passes into an accumulator 166 .
- the accumulator 166 provides a liquid stream 220 which can be further cooled by a third cooler 168 , being one or more coolers such as water and/or air coolers, to provide a reconstituted or reformed generally liquid refrigerant stream ready for passage through a valve 177 and return and use as stream 140 in the second refrigeration zone 142 .
- a third cooler 168 being one or more coolers such as water and/or air coolers, to provide a reconstituted or reformed generally liquid refrigerant stream ready for passage through a valve 177 and return and use as stream 140 in the second refrigeration zone 142 .
- heating of the first evaporated stream 140 a affects the volume flow of the subsequent compressor feed stream 120 a , and hence the properties of the second combined compressed stream 170 , the overall compressed stream 180 , and therefore the pressure of the first final compressed stream 160 , and hence the second compressor 112 b .
- heating of the second evaporated stream 140 b such as via a second heat exchanger 116 b , will allow control of the fourth compressor 112 a .
- heating of the third evaporated stream 140 c by a third heat exchanger 116 c will affect the first compressor 112 d
- heating of the fourth evaporated stream 140 d by a fourth heat exchanger 116 d will affect the third compressor 112 c.
- the heating of the first evaporated stream 140 a (to affect the properties of the second combined compressed stream 170 , the overall compressed stream 180 , the pressure of the first final compressed stream 160 , and hence the second compressor 112 b ), can also affect the first compressor 112 d , as it is in series with the second compressor 112 b .
- the heating of the first evaporated stream 140 a may have a greater effect on the second compressor 112 b than the first compressor 112 d , but it may nevertheless assist a degree of control over the first compressor 112 d.
- the heating of the second evaporated stream 140 b may allow control of the fourth compressor 112 a and the third compressor 112 c .
- heating of the third evaporated stream 140 c by a third heat exchanger 116 c may affect both the first compressor 112 d and the second compressor 112 b
- heating of the fourth evaporated stream 140 d by a fourth heat exchanger 116 d may affect the third compressor 112 c and the fourth compressor 112 a.
- FIG. 3 shows a third scheme 301 using a third refrigeration circuit 302 similar to the second scheme 101 and second refrigeration circuit 102 shown in FIG. 2 .
- the second compressor feed stream 120 b is now combined with the compressed stream 150 c from the third compressor 112 c prior to passage of the combined stream into the fourth refrigerant compressor 112 a .
- the first compressor feed stream 120 a is combined with the compressed stream 150 d from the first compressor 112 d for entry into the second refrigerant compressor 112 b .
- This arrangement of evaporated refrigerant streams and refrigerant compressors from a refrigeration zone is shown in WO 2005/057110 A1.
- the two final compressed steams 360 , 370 are further combined as an overall combined compressed stream 180 , first cooled, and a vapour recirculation stream 130 is optionally provided and divided into four fraction streams for combining with each of the evaporated refrigerant streams 140 a - d .
- the first continuing stream 200 is further cooled by a second cooler 164 , and passed into an accumulator 166 as described hereinbefore.
- heating of the first evaporated stream 140 a affects the volume flow of the subsequent compressor feed stream 120 a , and hence the properties of the first final compressed stream 360 , the overall combined compressed stream 180 , and therefore the pressure of the second combined compressed stream 370 , and hence the fourth compressor 112 a (and possibly the third compressor 112 c ).
- heating of the second evaporated stream 140 b such as via a second heat exchanger 116 b , will allow control of the second compressor 112 b (and possibly the first compressor 112 d ).
- heating of the third evaporated stream 140 c by a third heat exchanger 116 c will affect the first compressor 112 d (and possibly the second compressor 112 b ), and heating of the fourth evaporated stream 140 d by a fourth heat exchanger 116 d , will effect the third compressor 112 c (and possibly the fourth compressor 112 a ).
- Table 1 shows percentage changes in pressures and volume flows for a working example of the present invention based on the arrangement for refrigerant compressors for a refrigerant circuit shown in FIG. 2 .
- Heating of the first evaporated stream 140 a increases the pressure of the subsequent compressor feed stream 120 a into the fourth refrigerant compressor 112 a (by 7.09%) with a small reduction in its volume flow ( ⁇ 1.73%).
- the effect of this increase in pressure on the compressor feed stream 120 a into the fourth refrigerant compressor 112 a is to increase the volume flow through the second refrigerant compressor 112 b (by +3.30), such that the second compressor 112 b moves away from surge.
- heating the second evaporated stream 140 b increases the pressure of the second compressor feed stream ( 120 b ) on the second refrigerant compressor 112 b (by +6.42), which at least increases the volume flow through the third refrigerant compressor 112 c.
- Heating the third evaporated stream 140 c increases the pressure of the third compressor feed stream 120 c (by +1.31), which has the effect of increasing the volume flow through both the first refrigerant compressor 112 d (by +0.28) and the second refrigerant compressor 112 b (by 0.06), to move them both away from surge.
- heating of the fourth evaporated stream 140 d increases the pressure of the fourth compressor feed stream 120 d and the pressure of the first refrigerant compressor 112 d , and increases the volume flow (by 0.29%) through the third refrigerant compressor 112 c so that the third refrigerant compressor moves away from surge.
- valves including flow-control valves, recirculation valves and expansion valves. Some valves required in any circuit or process may not be specifically or generally mentioned or referenced herein. The skilled man is aware of the type and arrangement of valve or valves required to affect processing of a line, stream, flow, circuit, etc.
Abstract
A refrigerant stream is passed through at least one heat exchanger to provide a first at least partially evaporated stream and a second at least partially evaporated stream. A first compressor feed stream is provided from the first partially evaporated stream, and a second compressor feed stream is provided from the second partially evaporated stream. The first compressor feed stream is passed through a first refrigerant compressor and the second compressor feed stream through a second compressor, to provide first and second compressed streams, which are combined at a common pressure. The first refrigerant compressor is controlled by heating the second at least partially evaporated stream or the second compressor feed stream, or vice versa.
Description
- This application claims priority from European Patent Application No. 07119862.6, filed on Nov. 2, 2007, which is incorporated herein by reference.
- The present invention relates to a method and apparatus for controlling a refrigerant compressor.
- Such a method and apparatus may be used in a method of cooling a hydrocarbon stream, such as a natural gas stream. Accordingly, aspects of the invention relate to a method of cooling a hydrocarbon stream, and to a use of the apparatus in a process for cooling, and a use of the apparatus in a process for liquefying, a hydrocarbon feed stream.
- Several methods of cooling, usually liquefying, a natural gas stream, thereby obtaining liquefied natural gas (LNG), are known. It is desirable to liquefy a natural gas stream for a number of reasons. As an example, 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.
- As an example of liquefying natural gas, the natural gas, comprising predominantly methane, enters an LNG plant at elevated pressure and is pre-treated to produce a purified feed steam suitable for liquefying at cryogenic temperatures. The purified gas is processed through a plurality of cooling stages using heat exchangers involving one or more refrigeration circuits with compressors, to progressively reduce its temperature until liquefaction is achieved.
- Compressors for gaseous streams are used in many situations, systems and arrangements. Typically there is a vapour recycle or recirculation line around the compressor to avoid surge. A compressor is said to be ‘in deep surge’ when the main flow through the compressor reverses its direction. Normally, this is related to a discharge pressure being lower than the pressure downstream of the compressor outlet. This can cause rapid pulsations in flow, which is generally termed ‘surge’.
- Surge is often accompanied by excessive vibration and noise. This flow reversal is accompanied with a very violent change in energy, which causes a reversal of the thrust force. The surge process can be cyclic in nature, and if allowed to continue for sometime, irreparable damage can occur to the compressor.
- Where a compressor is dealing with ambient temperature gases or other non-critical situations, recycling of discharge gas via a vapour recycle line to avoid surge is a simple and common operation without complications. Any change in temperature of the compressor flow is not significant.
- Compressors used in refrigerant circuits have particular problems associated to them, especially when they are driven by fixed rotational speed drivers, such as a gas turbine. Refrigerant circuits are used in liquefaction systems, facilities and plants, such as for the production of a liquefied hydrocarbon stream such as liquefied natural gas (LNG). In a refrigerant circuit, the refrigerant is evaporated in one or more stages to cool the hydrocarbon stream, and one or more refrigerant compressors are used to recompress the evaporated refrigerant in one or more stages. Refrigerant compressors running at an effectively constant speed require relatively constant inflow of a gaseous stream to their suction side. Where the inflow of a gaseous stream falls for whatever reason below a certain minimum value, surge can occur.
- U.S. Pat. No. 4,464,720 discloses a surge control system which utilizes an algorithm to calculate a desired orifice differential pressure, and which compares the calculated result with an actual differential pressure. Pressure and temperature measurements are made on both the suction side and discharge side of a centrifugal compressor, and thus enter a control system so that the actual differential pressure is substantially equal to the desired differential pressure. A suction temperature of gas entering the centrifugal compressor is measured and used. However, the complex algorithm and values required for the calculations in U.S. Pat. No. 4,464,720 do not address any of the problems described above.
- The present invention provides a method of controlling a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream, the method at least comprising the steps of:
- (a) passing the refrigerant stream through at least one heat exchanger to provide a first at least partially evaporated stream and a second at least partially evaporated stream;
(b) providing a first compressor feed stream from the first partially evaporated stream and a second compressor feed stream from the second partially evaporated stream;
(c) passing the first compressor feed stream through the first refrigerant compressor and the second compressor feed stream through the second compressor to provide first and second compressed streams;
(d) combining the first and second compressed streams at a common pressure; and
(e) either heating the first at least partially evaporated stream or the first compressor feed stream to control the second compressor,
or heating the second at least partially evaporated stream or the second compressor feed stream to control the first compressor. - The present invention also provides a method of cooling a hydrocarbon stream such as natural gas, the method at least comprising the steps of:
- (a) providing a hydrocarbon feed stream;
(b) cooling the hydrocarbon feed stream by heat exchange against a refrigerant stream to provide a cooled hydrocarbon stream and an at least first and second partly evaporated refrigerant streams;
(c) compressing the first and second partly evaporated refrigerant streams using at least first and second refrigerant compressors in a method as herein defined. - The present invention also provides apparatus for controlling a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream, the apparatus at least comprising:
- at least one heat exchanger through which the refrigerant stream passes to provide a first at least partially evaporated stream and a second at least partially evaporated stream;
- a first compressor feed stream provided from the first partially evaporated stream;
- a second compressor feed stream provided from the second partially evaporated stream;
- a first refrigerant compressor through which passes the first compressor feed stream to provide a first compressed stream;
- a second compressor through which passes the second compressor feed stream to provide a second compressed stream;
- a combiner to combine the first and second compressed streams at a common pressure; and
- one or more heaters to either heat the first at least partially evaporated stream or the first compressor feed stream to control the second compressor,
- or to heat the second at least partially evaporated stream or the second compressor feed stream to control the first compressor.
- The present invention also provides the use of such an apparatus in a process for cooling a hydrocarbon stream, wherein said cooling comprises passing the hydrocarbon stream through the at least one heat exchanger of the apparatus whereby heat is transferred from the hydrocarbon stream to the refrigerant stream.
- The present invention also provides the use of such an apparatus in a process for liquefying a hydrocarbon stream, wherein said liquefying comprises cooling of the hydrocarbon stream, said cooling comprising passing the hydrocarbon stream through the at least one heat exchanger of the apparatus whereby heat is transferred from the hydrocarbon stream to the refrigerant stream.
- Embodiments and examples of the present invention will now be described by way of example only, and with reference to the accompanying non-limiting drawings in which:
-
FIG. 1 schematically shows a method of controlling a refrigerant compressor according to a first embodiment of the present invention; -
FIG. 2 schematically shows a method of controlling four refrigerant compressors according to another embodiment of the present invention; -
FIG. 3 schematically shows an alternative arrangement to the method shown inFIG. 2 . - For the purpose of this description, a single reference number will be assigned to a line as well as a stream carried in that line. Same reference numbers refer to similar components.
- The present invention is particularly suitable for, but not limited to, controlling two or more connected and multi-stage refrigerant compressors having a plurality of inlets accepting refrigerant at different pressure levels. The refrigerant compressor(s) may be used in one or more refrigerant circuits for cooling, optionally including liquefying, a hydrocarbon stream such as natural gas.
- It has been surprisingly found that where two refrigerant compressors have a common post-compression communication, for example a common discharge or common accumulator, the heating of one compressor feed stream, or its main component being its evaporated stream from a heat exchanger, can control the other connected refrigerant compressor. This is because the heating of such a stream affects its subsequent compression, and thus the pressure of the other stream being compressed via their common post-compression communication. This is further discussed hereinafter.
- The present invention may provide an improved method of controlling one or more refrigerant compressors, in particular two or more refrigerant compressors, used for compression of a multi-pressure level refrigerant.
- The present invention is particularly suitable, but not limited to, where there are two or more refrigerant compressors in the same refrigerant circuit for different compressor feed streams, more particularly where the compressor feed streams are at different pressure levels. When using multiple refrigerant compressors, either as separate compressors or one or more compressors having multiple pressure sections and having multiple inlets for different gas pressures, and optionally multiple recirculation lines, the method of the present invention allows all the refrigerant compressors to be controlled, especially to avoid surge.
- The present invention is particularly useful where a refrigerant stream is evaporated at different pressure levels, but requiring each evaporated fraction to be recompressed to a unified pressure for re-use as a refrigerant.
- Thus, in one embodiment, the method is for controlling three or more, preferably four, refrigerant compressors, and two, three, four or five compressor feed streams based on two, three, four or five at least partly evaporated refrigerant streams respectively, wherein at least one of the evaporated refrigerant streams or at least one of the compressor feed streams is heated prior to passing through its respective refrigerant compressor.
- More preferably, the method of the present invention comprises four compressor feed streams at four different pressures passing through four refrigerant compressors.
- The cooling of the hydrocarbon stream may partly or wholly liquefy the hydrocarbon stream so as to provide a liquefied hydrocarbon stream, such as LNG. The cooling of the hydrocarbon stream to provide the cooled hydrocarbon stream may also be followed by further cooling of the cooled hydrocarbon stream to further liquefy and/or sub-cool the cooled hydrocarbon stream.
- The or each refrigerant compressor involved in the present invention may be any suitable refrigerant compressor, optionally having two or more compression stages or pressure sections. Use of the term ‘refrigerant compressors’ herein extends to a single refrigerant compressor having multiple pressure sections in one casing, and able to receive two or more gaseous streams at different pressures. The hydrocarbon cooling or liquefying plant or facility may also involve one or more other refrigerant or other compressors not involved in the present invention.
- The first and second compressors may have a vapour recirculation line. Preferably, the first and second compressor feed streams are a combination of at least a fraction of the vapour recirculation stream in the vapour recirculation line and the first and second at least partially evaporated refrigerant streams respectively.
- The or each recirculation line useable in the present invention may be any suitable line able to transfer a recirculation stream, which can be liquid, gaseous or mixed phase, from the discharge side of a refrigerant compressor to its suction side or a relevant suction drum. The or each recirculation line may be divided or separated in a manner known in the art, to supply a recirculated stream part or fraction to two or more refrigerant compressors.
- A refrigerant stream may comprise a single component such as propane or nitrogen, preferably propane, or comprise a mixture of two or more selected from the group comprising: nitrogen, methane, ethane, ethylene propane, propylene, butanes, pentanes.
- The heating of the relevant stream or streams in step (e) can be provided by any method of heating. The heating may involve use of one or more dedicated heaters, optionally using a fuel gas, and/or by heat exchange against a stream capable of releasing heat to the relevant stream of streams, such as a warmer stream or streams, in one or more heat exchangers. In a cooling and/or liquefaction process or plant, there are typically a number of sources of a warmer stream or streams, which could be routed to provide, when required, the heating for step (e).
- The common post-compression communication of the first and second refrigerant compressors, which allows combining of the first and second compressed streams at a common pressure, can be any form of combining, either by a dedicated combiner such as a junction or T-piece, or by their common collection, for example in a cooler or accumulator.
- In another embodiment, the method of the present invention is able to prevent surge in a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream. Preferably heating the first at least partially evaporated stream or the first compressor feed stream is to prevent surge in the second compressor, and heating the second at least partially evaporated stream or the second compressor feed stream is to prevent surge in the first compressor.
- Referring to the drawings,
FIG. 1 shows a simplified and general scheme 1 of a method for controlling a refrigerant compressor for a refrigerant stream. - In
FIG. 1 , there is also shown a method of cooling a hydrocarbon stream such as natural gas. Ahydrocarbon feed stream 5 passes through arefrigeration zone 42 to provide a cooledhydrocarbon stream 6, for example, having a temperature below 0° C., for example between −10° C. and −70° C.; optionally partly liquefied. Therefrigeration zone 42 may be part of a liquefaction plant (not shown), wherein the cooledhydrocarbon stream 6 is subsequently fully liquefied. - The
hydrocarbon feed stream 5 is cooled by heat exchange against arefrigerant stream 40 circulating in arefrigerant circuit 2. Therefrigerant stream 40 passes through at least two heat exchangers (32, 34) in therefrigeration zone 42. - In the scheme 1 shown in
FIG. 1 , there is afirst heat exchanger 32, from which a fraction of therefrigerant stream 40 is expanded and evaporated to provide a first at least partially evaporatedstream 40 a, and asecond heat exchanger 34, usually at a lower pressure than that of thefirst heat exchanger 32, which receives the remaining fraction of therefrigerant stream 40 from thefirst heat exchanger 32, expands and evaporates the remaining fraction, to provide a second at least partially evaporatedstream 40 b. Expansion may be performed by means of a valve upstream of the respective relevant heat exchanger, such asvalve 66 upstream of thefirst heat exchanger 32 for the expansion in thefirst heat exchanger 32 and another valve (not shown) in the line between the first and second heat exchangers for the expansion in thesecond heat exchanger 34. - Each of the evaporated
refrigerant streams heat exchangers stream 40 a is at a higher pressure than the second evaporatedstream 40 b although the present invention is not limited thereto. - Typically, each of the first and second evaporated
streams refrigerant compressors compressed streams compressed streams combiner 52 to provide a combinedstream 60, which can be first cooled by a first ambient heat exchanger such as one or more water and/orair coolers 54, to provide a coolercompressed stream 60 a. - When desired or necessary, the cooler compressed
stream 60 a can be divided by adivider 56, for instance in the form of a stream-splitter, into a continuingrefrigerant stream 60 b and avapour recirculation stream 30 passing through avapour recirculation line 30. Thedivider 56 may be any arrangement able to divide a stream into two or more fractions or parts, such as a manifold or dedicated unit, or more simply, a T-piece. The continuingrefrigerant stream 60 b passes through one or morefurther coolers 58, one ormore accumulators 62, one or more yetfurther coolers 64, prior to expansion through anexpansion valve 66 to provide therefrigerant stream 40 and recirculation through therefrigeration zone 42. - The
vapour recirculation stream 30 may then be divided by anysuitable divider 31 into two part-recirculation streams suitable control valves streams - It is known that vapour recirculation provides the ability to increase flow through a compressor, more particularly to maintain minimum flow where there is a reduction in the flow of evaporated refrigerant which normally forms the major component of the compressor feed stream.
- Every compressor requires a balance between its inlet pressure and outlet or discharge pressure. For a refrigerant compressor in a refrigerant circuit, the inlet and outlet pressures are usually significantly determined by two vapour pressures; firstly from the heat exchangers using the cooling duty of the refrigerant stream, and secondly from the post-compression refrigerant accumulator.
- However, there can be occasions or periods where the pressure balance is upset, such that the discharge pressure from a refrigerant compressor can be insufficient compared to the inlet pressure, leading to surge. One example of this is an insufficiency in the provision of an evaporated stream from a heat exchanger. With an insufficient flow of evaporated stream to provide the compressor feed stream, the compressor can go towards surge.
- A benefit of the present invention is recognising that where there are two or more refrigerant compressors having a common post-compression communication, such as a common discharge, then the discharge pressure from each refrigerant compressor can affect the other refrigerant compressor. That is, using the post-compression common pressure to allow the action of one refrigerant compressor to control an associated or connected refrigerant compressor.
- Referring to the Scheme 1 shown in
FIG. 1 , there is the possibility of the secondrefrigerant compressor 14 heading towards surge where, for example, the pressure of the secondcompressor feed stream 20 b is decreasing, such that the relationship of its pressure with the pressure of the secondcompressed stream 50 b is unbalanced. - The method of the present invention involves heating of the first at least partially evaporated
stream 40 a and/or the first combinedfeed stream 10 a and/or the firstcompressor feed stream 20 a, to control thesecond compressor 14. For example,FIG. 1 shows one or more heaters such as aheat exchanger 22 in the path of the first at least partially evaporatedstream 40 a, which allows heating, preferably rapid heating, of the first at least partially evaporatedstream 40 a upstream of thefirst suction drum 16. - By heating the first at least partially evaporated
stream 40 a, there will be the same volume flow in this stream, but the mass flow in the subsequent firstcompressor feed stream 20 a is reduced. With less mass flow in the subsequent firstcompressed stream 50 a, the same amount of cooling duty provided by the first andfurther coolers accumulator 62 is lower than normal, such that there is less vapour pressure created therefrom. With less vapour pressure from theaccumulator 62, this feeds back to reducing the pressure on the discharge side of thesecond compressor 14, such that it is less likely to go into surge. - In the same way, heating of the second at least partially evaporated
stream 40 b or the second combinedfeed stream 10 b or the secondcompressor feed stream 20 b provides control of thefirst compressor 12. In scheme 1, there is shown by way of example a heater such as asimilar heat exchanger 24 in the path of the second at least partially evaporatedstream 40 b for this purpose. - A person skilled in the art will be aware of the nature and provision of the first and
second heat exchangers -
FIG. 2 shows asecond scheme 101 involving anotherrefrigeration circuit 102 comprising asecond refrigeration zone 142. Thesecond refrigeration zone 142 may comprise two or more, such as four, separate heat exchangers, or it may comprise a single heat exchanger involving the outlet of refrigerant at different pressure levels. Such arrangements are well known in the art, and examples are shown in WO 01/44734 A2 and Wo 2005/057110 A1. - The
second refrigeration zone 142 can be for withdrawing heat from a stream, for example one ormore hydrocarbon streams 100 such as a natural gas stream to be liquefied. Examples of methods for liquefying natural gas are mentioned in U.S. Pat. No. 6,389,844 and U.S. Pat. No. 6,370,910 B1 which are hereby incorporated by reference. In these patent documents, a plant is described for liquefying natural gas wherein the plant comprises a pre-cooling heat exchanger having an inlet for natural gas and an outlet for cooled natural gas, and a pre-cool refrigerant circuit for removing heat from the natural gas in the pre-cooling heat exchanger. - The
second refrigeration zone 142 may be equivalent to or an extension of thefirst refrigeration zone 42 shown inFIG. 1 . For example, where cooling, preferably liquefying, of ahydrocarbon stream 100 involves two or more stages, such as a first stage to lower the temperature of thehydrocarbon stream 100 below 0° C., and a second stage to further lower the hydrocarbon stream to a temperature below −90° or −100° C., thesecond refrigeration zone 142 could act as the cooling for the first stage. - In the arrangement shown in
FIG. 2 , thesecond refrigeration zone 142 has first, second, third andfourth heat exchangers fourth outlets refrigerant stream 140 evaporated at different pressure levels, with decreasing pressure from thefirst outlet 143 to thefourth outlet 146. For example, thefirst outlet 143 is intended for gaseous refrigerant released at a high-high pressure as a first evaporatedstream 140 a, thesecond outlet 144 for gaseous refrigerant released at a high pressure as a second evaporatedstream 140 b, thethird outlet 145 for gaseous refrigerant released at a medium pressure as a third evaporatedstream 140 c, and thefourth outlet 146 for gaseous refrigerant released at a low pressure as a fourth evaporatedstream 140 d. Thesecond refrigeration zone 142 may have further outlets. - Each evaporated
stream 140 a-d is passed into a corresponding suction drum or gas/liquid separator such as knockout drums 148 a-d, from which there are respective overhead gaseous compressor feed streams 120 a-d. - The fourth
compressor feed stream 120 d passes into a firstrefrigerant compressor 112 d to provide acompressed stream 150 d, which is combined with the secondcompressor feed stream 120 b to enter a secondrefrigerant compressor 112 b to provide a first finalcompressed stream 160. The first and secondrefrigerant compressors - Similarly, the third
compressor feed stream 120 c passes into a thirdrefrigerant compressor 112 c, and itscompressed stream 150 c is combined with the firstcompressor feed stream 120 a to pass into a fourthrefrigerant compressor 112 a and provide a second finalgaseous stream 170. As above, the third and fourthrefrigerant compressors third streams - The arrangement of the
refrigeration zone 142, the outlets and gaseous streams therefrom, and the refrigerant compressors 112 a-d are known in the art, and are shown and described for example in WO 01/44734 A2. - The first and second final
compressed streams compressed stream 180, which is cooled by afirst cooler 162 such as an ambient water and/or air cooler known in the art. Thefirst cooler 162 may comprise one or more coolers in parallel, series or both, and provides a cooledcompressed stream 190. - In the same manner as described above for the arrangement shown in
FIG. 1 , the cooledcompressed stream 190 can be divided when desired or necessary between a continuingstream 200 and avapour recirculation stream 130 by use of adivider 156, e.g. in the form of a stream splitter. Thevapour recirculation stream 130 may be divided into fourseparate fraction streams 130 a-d to pass through separate respective control valves 152 a-d and be combined with the evaporatedrefrigerant streams 140 a-d respectively to provide combinedfeed streams 110 a-d respectively. - The first continuing
steam 200 is further cooled and mostly or fully condensed, for example by asecond cooler 172 being one or more coolers such as water and/or air coolers, which provides a cooled continuingsteam 210. The cooling provided by thesecond cooler 172 preferably fully condenses the cooled continuingstream 210. The cooled continuingstream 210 passes into anaccumulator 166. - The
accumulator 166 provides aliquid stream 220 which can be further cooled by athird cooler 168, being one or more coolers such as water and/or air coolers, to provide a reconstituted or reformed generally liquid refrigerant stream ready for passage through avalve 177 and return and use asstream 140 in thesecond refrigeration zone 142. - In the same manner as described in
FIG. 1 , heating of the first evaporatedstream 140 a, for example by using one or more heaters such as aheat exchanger 116 a in its path, affects the volume flow of the subsequentcompressor feed stream 120 a, and hence the properties of the second combined compressedstream 170, the overallcompressed stream 180, and therefore the pressure of the first finalcompressed stream 160, and hence thesecond compressor 112 b. In the same way, heating of the second evaporatedstream 140 b, such as via asecond heat exchanger 116 b, will allow control of thefourth compressor 112 a. Similarly, heating of the third evaporatedstream 140 c by athird heat exchanger 116 c, will affect thefirst compressor 112 d, and heating of the fourth evaporatedstream 140 d by afourth heat exchanger 116 d, will affect thethird compressor 112 c. - Indeed, depending on the arrangement and relationship of the streams and compressors in the
second scheme 101 shown inFIG. 2 , the heating of the first evaporatedstream 140 a (to affect the properties of the second combined compressedstream 170, the overallcompressed stream 180, the pressure of the first finalcompressed stream 160, and hence thesecond compressor 112 b), can also affect thefirst compressor 112 d, as it is in series with thesecond compressor 112 b. Typically, the heating of the first evaporatedstream 140 a may have a greater effect on thesecond compressor 112 b than thefirst compressor 112 d, but it may nevertheless assist a degree of control over thefirst compressor 112 d. - Similarly, again depending on the arrangement and relationship of the streams and compressors in the
second scheme 101 shown inFIG. 2 , the heating of the second evaporatedstream 140 b may allow control of thefourth compressor 112 a and thethird compressor 112 c. Similarly, heating of the third evaporatedstream 140 c by athird heat exchanger 116 c may affect both thefirst compressor 112 d and thesecond compressor 112 b, and heating of the fourth evaporatedstream 140 d by afourth heat exchanger 116 d may affect thethird compressor 112 c and thefourth compressor 112 a. -
FIG. 3 shows athird scheme 301 using athird refrigeration circuit 302 similar to thesecond scheme 101 andsecond refrigeration circuit 102 shown inFIG. 2 . However, in thesecond refrigeration circuit 302, the secondcompressor feed stream 120 b is now combined with thecompressed stream 150 c from thethird compressor 112 c prior to passage of the combined stream into the fourthrefrigerant compressor 112 a. Meanwhile, the firstcompressor feed stream 120 a is combined with thecompressed stream 150 d from thefirst compressor 112 d for entry into the secondrefrigerant compressor 112 b. This arrangement of evaporated refrigerant streams and refrigerant compressors from a refrigeration zone is shown in WO 2005/057110 A1. - In a similar arrangement to that shown in
FIG. 2 , the two finalcompressed steams compressed stream 180, first cooled, and avapour recirculation stream 130 is optionally provided and divided into four fraction streams for combining with each of the evaporatedrefrigerant streams 140 a-d. The first continuingstream 200 is further cooled by asecond cooler 164, and passed into anaccumulator 166 as described hereinbefore. - In the same manner as described in
FIG. 2 , heating of the first evaporatedstream 140 a, for example by using aheat exchanger 116 a in its path, affects the volume flow of the subsequentcompressor feed stream 120 a, and hence the properties of the first finalcompressed stream 360, the overall combinedcompressed stream 180, and therefore the pressure of the second combined compressedstream 370, and hence thefourth compressor 112 a (and possibly thethird compressor 112 c). In the same way, heating of the second evaporatedstream 140 b, such as via asecond heat exchanger 116 b, will allow control of thesecond compressor 112 b (and possibly thefirst compressor 112 d). Similarly, heating of the third evaporatedstream 140 c by athird heat exchanger 116 c, will affect thefirst compressor 112 d (and possibly thesecond compressor 112 b), and heating of the fourth evaporatedstream 140 d by afourth heat exchanger 116 d, will effect thethird compressor 112 c (and possibly thefourth compressor 112 a). - Table 1 shows percentage changes in pressures and volume flows for a working example of the present invention based on the arrangement for refrigerant compressors for a refrigerant circuit shown in
FIG. 2 . -
TABLE 1 Heated Refrigerant Pressure (bar) Volume Flow Stream Compressor % change % change 140a 112d 1.35 −0.50 112c 4.00 −4.34 112b 1.51 3.30 112a 7.09 −1.73 140b 112d 4.84 −5.99 112c 1.76 2.42 112b 6.42 −10.67 112a −0.02 0.93 140c 112d 0.32 0.28 112c 1.31 −1.69 112b 0.14 0.06 112a 0.23 −0.33 140d 112d 2.60 −3.56 112c 0.33 0.29 112b 0.67 −0.94 112a 0.09 −0.06 - Heating of the first evaporated
stream 140 a increases the pressure of the subsequentcompressor feed stream 120 a into the fourthrefrigerant compressor 112 a (by 7.09%) with a small reduction in its volume flow (−1.73%). The effect of this increase in pressure on thecompressor feed stream 120 a into the fourthrefrigerant compressor 112 a is to increase the volume flow through the secondrefrigerant compressor 112 b (by +3.30), such that thesecond compressor 112 b moves away from surge. - Meanwhile, heating the second evaporated
stream 140 b increases the pressure of the second compressor feed stream (120 b) on the secondrefrigerant compressor 112 b (by +6.42), which at least increases the volume flow through the thirdrefrigerant compressor 112 c. - Heating the third evaporated
stream 140 c increases the pressure of the thirdcompressor feed stream 120 c (by +1.31), which has the effect of increasing the volume flow through both the firstrefrigerant compressor 112 d (by +0.28) and the secondrefrigerant compressor 112 b (by 0.06), to move them both away from surge. - Lastly, heating of the fourth evaporated
stream 140 d increases the pressure of the fourthcompressor feed stream 120 d and the pressure of the firstrefrigerant compressor 112 d, and increases the volume flow (by 0.29%) through the thirdrefrigerant compressor 112 c so that the third refrigerant compressor moves away from surge. - There are references hereinabove to various types of “valves” including flow-control valves, recirculation valves and expansion valves. Some valves required in any circuit or process may not be specifically or generally mentioned or referenced herein. The skilled man is aware of the type and arrangement of valve or valves required to affect processing of a line, stream, flow, circuit, etc.
- Persons skilled in the art will readily understand that the present invention may be modified in many ways without departing from the scope of the appended claims.
Claims (20)
1. A method of controlling a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream, the method at least comprising the steps of:
(a) passing the refrigerant stream through at least one heat exchanger to provide a first at least partially evaporated stream and a second at least partially evaporated stream;
(b) providing a first compressor feed stream from the first partially evaporated stream and a second compressor feed stream from the second partially evaporated stream;
(c) passing the first compressor feed stream through the first refrigerant compressor and the second compressor feed stream through the second compressor to provide first and second compressed streams;
(d) combining the first and second compressed streams at a common pressure; and
(e) either heating the first at least partially evaporated stream or the first compressor feed stream to control the second compressor,
or heating the second at least partially evaporated stream or the second compressor feed stream to control the first compressor.
2. Method as claimed in claim 1 , wherein the first and second compressors have a vapour recirculation line, and wherein the first and second compressor feed streams are a combination of at least a fraction of the vapour recirculation stream in the vapour recirculation line and the first and second at least partially evaporated refrigerant streams respectively.
3. Method as claimed in claim 1 , wherein the refrigerant in the refrigerant circuit is propane.
4. Method as claimed in claim 1 , wherein the first and second evaporated streams have different pressures.
5. Method as claimed in claim 1 for controlling three or more refrigerant compressors, and two, three, four or five compressor feed streams based on two, three, four or five at least partly evaporated refrigerant streams respectively, wherein at least one of the evaporated refrigerant streams or at least one of the compressor feed streams is heated prior to passing through its respective refrigerant compressor.
6. Method as claimed in claim 5 , comprising four compressor feed streams at four different pressures passing through four refrigerant compressors.
7. A method as claimed in claim 1 , wherein heating the first at least partially evaporated stream or the first compressor feed stream is to prevent surge in the second compressor, and
heating the second at least partially evaporated stream or the second compressor feed stream is to prevent surge in the first compressor.
8. A method of cooling a hydrocarbon stream, the method at least comprising the steps of:
(a) providing a hydrocarbon feed stream;
(b) cooling the hydrocarbon feed stream comprising heat exchanging the hydrocarbon feed stream against a refrigerant stream to provide a cooled hydrocarbon stream and at least first and second partly evaporated refrigerant streams;
(c) compressing the first and second partly evaporated refrigerant streams using at least first and second refrigerant compressors in a method as defined in claim 1 .
9. Method as claimed in claim 8 , wherein the cooling comprises liquefying the hydrocarbon feed stream to provide a liquefied hydrocarbon stream.
10. Method as claimed in claim 9 , wherein the liquefied hydrocarbon stream is an LNG stream.
11. Method as claimed in claim 8 , wherein the hydrocarbon feed stream comprises natural gas.
12. Method as claimed in claim 8 , wherein the hydrocarbon feed stream consists essentially of natural gas.
13. Apparatus for controlling a refrigerant compressor being one of at least a first refrigerant compressor and a second refrigerant compressor having a common post-compression communication in a refrigerant circuit circulating a refrigerant stream, the apparatus at least comprising:
at least one heat exchanger through which the refrigerant stream passes to provide a first at least partially evaporated stream and a second at least partially evaporated stream;
a first compressor feed stream provided from the first partially evaporated stream;
a second compressor feed stream provided from the second partially evaporated stream;
a first refrigerant compressor through which passes the first compressor feed stream to provide a first compressed stream;
a second compressor through which passes the second compressor feed stream to provide a second compressed stream;
a combiner to combine the first and second compressed streams at a common pressure; and
one or more heaters to either heat the first at least partially evaporated stream or the first compressor feed stream to control the second compressor,
or to heat the second at least partially evaporated stream or the second compressor feed stream to control the first compressor.
14. Use of the apparatus of claim 13 in a process for cooling a hydrocarbon stream, wherein said cooling comprises passing the hydrocarbon stream through the at least one heat exchanger of the apparatus whereby heat is transferred from the hydrocarbon stream to the refrigerant stream.
15. Use of the apparatus of claim 13 in a process for liquefying a hydrocarbon stream, wherein said liquefying comprises cooling of the hydrocarbon stream, said cooling comprising passing the hydrocarbon stream through the at least one heat exchanger of the apparatus whereby heat is transferred from the hydrocarbon stream to the refrigerant stream.
16. Method as claimed in claim 2 , wherein the refrigerant in the refrigerant circuit is propane.
17. Method as claimed in claim 2 , wherein the first and second evaporated streams have different pressures.
18. Method as claimed in claim 3 , wherein the first and second evaporated streams have different pressures.
19. Method as claimed in claim 1 for controlling four refrigerant compressors, and two, three, four or five compressor feed streams based on two, three, four or five at least partly evaporated refrigerant streams respectively, wherein at least one of the evaporated refrigerant streams or at least one of the compressor feed streams is heated prior to passing through its respective refrigerant compressor.
20. Method as claimed in claim 2 for controlling three or more refrigerant compressors, and two, three, four or five compressor feed streams based on two, three, four or five at least partly evaporated refrigerant streams respectively, wherein at least one of the evaporated refrigerant streams or at least one of the compressor feed streams is heated prior to passing through its respective refrigerant compressor.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
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EP07119862.6 | 2007-11-02 | ||
EP07119862 | 2007-11-02 |
Publications (1)
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US20090188277A1 true US20090188277A1 (en) | 2009-07-30 |
Family
ID=39580681
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US12/262,028 Abandoned US20090188277A1 (en) | 2007-11-02 | 2008-10-30 | Method and apparatus for controlling a refrigerant compressor, and method for cooling a hydrocarbon stream |
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US (1) | US20090188277A1 (en) |
GB (1) | GB2454344A (en) |
Cited By (3)
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US20120060538A1 (en) * | 2009-05-26 | 2012-03-15 | Mitsubishi Electric Corporation | Heat pump apparatus |
CN104567064A (en) * | 2015-01-06 | 2015-04-29 | 东华工程科技股份有限公司 | Energy-saving compression refrigeration method |
US20180223856A1 (en) * | 2015-07-09 | 2018-08-09 | Nuovo Pignone Tecnologie Srl | Compressor system with a cooling arrangement between the anti-surge valve and the compressor suction side and relevant method |
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DE102016004606A1 (en) * | 2016-04-14 | 2017-10-19 | Linde Aktiengesellschaft | Process engineering plant and process for liquefied gas production |
CN110500910B (en) * | 2019-08-26 | 2023-09-15 | 华北电力大学 | Thermal mass decoupling method of thermal mass decoupling heat exchanger |
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Also Published As
Publication number | Publication date |
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GB2454344A (en) | 2009-05-06 |
GB0819783D0 (en) | 2008-12-03 |
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