Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
  • F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
  • F01K23/04—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled condensation heat from one cycle heating the fluid in another cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
  • F01D15/10—Adaptations for driving, or combinations with, electric generators
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K13/00—General layout or general methods of operation of complete plants
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K13/00—General layout or general methods of operation of complete plants
  • F01K13/02—Controlling, e.g. stopping or starting
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
  • F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
  • F01K25/10—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours the vapours being cold, e.g. ammonia, carbon dioxide, ether
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K9/00—Plants characterised by condensers arranged or modified to co-operate with the engines
  • F01K9/003—Plants characterised by condensers arranged or modified to co-operate with the engines condenser cooling circuits

Definitions

• the present invention relates to a method of producing electrical energy using a combination of several efficiency-enhanced Rankine cycles.
• a stream of a cryogenic liquid such as liquefied natural gas
• it can be used as a source of Rankine cycles cold, and the method according to the invention can ensure regasification of said stream of cryogenic liquid with upgrading of its refrigeration content.
• the liquefied natural gas (LNG) must be regasified, or in other words revaporized, at a pressure of the order of 10 to 90 bar depending on the network.
• This flashback takes place in LNG terminals, generally at room temperature by exchanging heat with seawater, possibly seawater heated with natural gas.
• the refrigeration content of the liquefied natural gas is then in no way valued.
• a known method is based on a direct expansion of natural gas. Liquefied natural gas is pumped at a pressure greater than that of the distribution network, vaporized by heat exchange with a hot source such as sea water, then expanded to network pressure in an expansion turbine associated with an electric generator.
• thermodynamic cycles using an intermediate fluid, or working fluid.
• a working fluid is vaporized under pressure against a source hot such as sea water in a first heat exchanger, then expanded in a turbine coupled to an electric generator.
• the expanded working fluid is then condensed in a second exchanger against LNG which is used as the cold source of the cycle. This results in a low pressure liquid working fluid which is pumped and returned at high pressure to the first exchanger, thus closing the cycle.
• the Rankine cycle can operate with water as the working fluid for applications such as geothermal heat recovery, the use of organic fluids evaporating at low temperature makes it possible to exploit cold sources at low temperature. low temperature. This is then referred to as the Organic Rankine Cycle (or Organic Rankine Cycle).
• ORC cycles are conventionally industrialized using LNG as a cold source and sea water as a hot source, but have relatively low energy yields, of the order of 20 kWh per tonne of vaporized LNG, i.e. - say 0.015 kWh / Nm 3 .
• conventional ORC cycles using propane as working fluid are limited by the low temperature at which they can work, the temperature of the hot source always being that of sea water, given the properties of propane. .
• document US-A-2015/0075164 discloses a combination of several cycles in which a hot source supplies the vaporization exchangers of each cycle in series and a cold source supplies the condensation exchangers of each cycle in parallel.
• a hot source supplies the vaporization exchangers of each cycle in series
• a cold source supplies the condensation exchangers of each cycle in parallel.
• Also known from document U SA-2009/0100845 is a combination of several cycles in which LNG is used as a cold source in the condensation exchanger of the cycles and in which the same working fluid condenses at several pressure levels against the cold source, depending on temperature levels.
• the arrangements according to the prior art are not entirely satisfactory for various reasons.
• US-A-2015/0075164 is suitable for recovering calories contained in a hot source, which gives up its heat to the working fluid and the temperature of which therefore decreases as successive passes through the heat recovery exchangers. .
• This solution does not solve the problem of recovering cold from a cold source.
• US 2009/0100845 uses a single working fluid. In this case, the more the cold source heats up, the higher the condensation pressure. Expansion in the associated turbine therefore generates less power.
• the object of the present invention is to resolve all or part of the above-mentioned problems, in particular by proposing a method for generating electricity in which the recovery of cold is improved and the energy efficiency further increased compared to the prior art. .
• the solution according to the invention is then a method for producing electrical energy implementing at least a first Rankine cycle and a second Rankine cycle, said cycles being operated in at least one heat exchange device comprising several passages. configured for the flow of fluids to be placed in a heat exchange relationship, said first Rankine cycle comprising the following steps:
• step b) outlet of the first working fluid at least partially vaporized in step a) of the first passage and expansion to a first low pressure in a first expansion member cooperating with a first electrical generator so as to produce energy electric
• step c) introduction of the first working fluid expanded in step b) in at least a third passage and condensation of at least part of said first working fluid against at least a first cold stream flowing in at least a fourth passage in relation heat exchange with said at least one third passage, d) exit of said first working fluid at least partially condensed in step c) from the third passage and reintroduction after pressure rise to the first high pressure in the first passage , and the second Rankine cycle comprising the following steps:
• step e) introduction at a second high pressure of a second working fluid into at least a fifth passage and vaporization of at least part of said second working fluid against at least a second hot stream, f) outlet of the second working fluid at least partially vaporized in step e) from the fifth passage and expansion to a second low pressure in a second expansion member cooperating with a second electric generator so as to produce energy electric,
• step g) introduction of the second working fluid relaxed in step f) in at least a sixth passage and condensation of at least a part of said second working fluid against at least a second cold stream flowing in at least a seventh passage in relation heat exchange with at least the sixth passage, h) outlet of said second working fluid at least partially condensed in step g) of the sixth passage and reintroduction, after raising the pressure to the second high pressure, into the fifth passage,
• step e) the second hot stream of the second Rankine cycle is formed at least in part by the first working fluid flowing in step c) in the third passage and, in step c), the first cold stream is formed by the second cold stream leaving the seventh passage.
• the invention may include one or more of the following characteristics:
• the second cold stream is introduced into the seventh passage at a temperature below -100 ° C.
• step c) the first working fluid circulates against the current with the first cold stream and / or in step g), the second working fluid circulates against the current with the second cold stream.
• the first working fluid and the second working fluid comprising respectively a first mixture of hydrocarbons and a second mixture of hydrocarbons, preferably the first and the second second mixture of hydrocarbons each contain at least two hydrocarbons chosen from methane, ethane, propane, butane, ethylene, propylene, butene, isobutane, optionally added with at least one additional component chosen among nitrogen, argon, helium, carbon dioxide, neon.
• the first hot stream is formed of sea water, preferably at a temperature strictly above 0 ° C, preferably also included between 10 and 30 ° C, the sea water having possibly undergone a reheating step before introduction into the second passage.
• the first high pressure is greater than the first low pressure of the first working fluid by a multiplying factor of between 2.5 and 15 and / or the second high pressure is greater than the second low pressure of the second working fluid of a multiplying factor of between 2.5 and 15, preferably, the first and / or second high pressures are between 10 and 40 bar and / or the first and / or second low pressures are between 1, 5 and 5 bar.
• step d) the first working fluid leaving the third passage is introduced into at least a ninth passage in heat exchange relationship with said third, fourth and / or fifth passages, before being reintroduced into the first passage and / or, in step h), the second working fluid leaving the sixth passage is introduced into at least a tenth passage in heat exchange relationship with the sixth and / or seventh passages, before being reintroduced into the fifth pass.
• the second cold stream is a stream of liquefied hydrocarbons such as liquefied natural gas or a stream of cryogenic liquid preferably chosen from: a stream of liquefied nitrogen, a stream of liquefied oxygen, a stream of liquefied hydrogen.
• the second cold stream is a stream of hydrocarbons, in particular of natural gas, introduced completely liquefied in the seventh passage at a temperature between -140 and -170 ° C and the first cold stream leaves at least a fourth passage completely vaporized at a temperature between 5 and 50 ° C.
• the first working fluid has a first temperature and, at the end of step g), the second working fluid has a second temperature lower than the first temperature, with preferably T 1 between -110 and -80 ° C and T2 between -120 and -160 ° C.
• the first cold stream leaving the fourth passage is introduced into at least an eighth passage in order to be heated there against the first hot current and / or the first working fluid, preferably the first cold current leaves the eighth passage fully vaporized at a temperature between 5 and 50 ° C.
• the first, second, third, fourth, fifth, sixth, seventh, eighth, ninth and / or tenth passages form part of at least one heat exchanger of the brazed plate type, said exchanger comprising a stack of several parallel plates and spaced relative to each other so as to delimit between them several series of passages within said exchanger.
• the first and second passages are part of a first heat exchanger
• the third, fourth, fifth and / or ninth passages are part of a second heat exchanger
• the sixth, seventh and / or tenth passages are part of a third heat exchanger, said first, second and third exchangers forming physically distinct entities.
• the third, fourth, fifth and / or ninth passages and the sixth, seventh and / or tenth passages are part of the same heat exchanger, the second cold stream being introduced from a first inlet located at a cold end of said exchanger and having the lowest temperature of the exchanger, the first working fluid expanded in step b) being introduced from a second inlet located at a hot end of said exchanger and having the highest temperature of the exchanger up to a second outlet arranged at a first intermediate level of the exchanger located between the cold end and the hot end and the second working fluid expanded in step f) being introduced into the exchanger by a third inlet arranged at a second intermediate level located between the first intermediate level and the cold end of the exchanger.
• the second cold stream being introduced from a first inlet located at a cold end of said exchanger and having the lowest temperature of the exchanger
• the first hot stream being introduced from a fifth inlet located at a hot end of said exchanger and having the highest temperature of the exchanger
• the first working fluid relaxed in step b) being introduced from a second inlet arranged at a third intermediate level located between the cold end and the hot end and leaving said exchanger through a second outlet arranged at a first intermediate level of the exchanger located between the third intermediate level and the cold end of the exchanger and the second working fluid expanded in step f) being introduced into the exchanger through a third inlet arranged at a second intermediate level located between the first intermediate level and the cold end of the exchanger.
• the second cold stream is a stream of cryogenic liquid introduced into the seventh passage at a temperature below -180 ° C, preferably between -180 and -253 ° C.
• the process implements a third Rankine cycle operated upstream of the second Rankine cycle, the third Rankine cycle comprising the following steps:
• step j) expansion of the third working fluid from step j) to a third low pressure in a third expansion member cooperating with a third electrical generator so as to produce electrical energy
• the first, second and / or third generators are combined one and the same electric generator, the first expansion member, the second expansion member and / or the third expansion member being coupled to this same electric generator so that said generator generates electrical energy simultaneously from the first cycle, second cycle and / or third Rankine cycle.
• the invention relates to an installation for producing electrical energy comprising means for implementing a first Rankine cycle and a second Rankine cycle comprising at least one heat exchange device comprising multiple passages configured for flow of fluids to be placed in a heat exchange relationship, the means for implementing the first Rankine cycle comprising:
• a first expansion member arranged downstream of said first passage and configured to reduce the pressure of the first working fluid leaving the first passage from a first high pressure to a first low pressure
• a first pressure-lifting member arranged downstream of said third passage and configured to increase the pressure of the first working fluid leaving the third passage from the first low pressure to the first high pressure
• a second expansion member arranged downstream of said fifth passage and configured to reduce the pressure of the second working fluid leaving the fifth passage from a second high pressure to a second low pressure, - a second electric generator coupled to the second expansion member,
• a second pressure-lifting member arranged downstream of said sixth passage and configured to increase the pressure of the second working fluid leaving the sixth passage from the second low pressure to the second high pressure
• the fifth passage is brought into heat exchange relation with the third passage so that the second working fluid is vaporized at least in part against the first working fluid introduced into the third passage and in that the seventh passage is arranged upstream of the fourth passage and placed in fluid communication with said fourth passage and so that the first cold stream introduced into the fourth passage is formed by the second cold stream leaving the seventh passage.
• said installation may further comprise at least a ninth passage in heat exchange relationship with said third, fourth and / or fifth passages, said ninth passage being configured so that the first working fluid leaving the third passage is introduced. in said at least a ninth passage before being reintroduced into the first passage.
• said installation may comprise at least a tenth passage in heat exchange relation with the sixth and / or seventh passages in step h), the tenth passage being configured so that the second working fluid exiting of the sixth passage is introduced into the at least a tenth passage before being reintroduced into the fifth passage.
• natural gas refers to any composition containing hydrocarbons including at least methane. This includes a "crude” composition (prior to any treatment or washing), as well as any composition that has been partially, substantially or fully treated for the reduction and / or removal of one or more compounds, including, but not limited to sulfur, carbon dioxide, water, mercury, and certain heavy and aromatic hydrocarbons.
• Fig. 1 schematically shows a method for generating electrical energy according to one embodiment of the invention.
• Fig. 2 schematically shows a method of generating electrical energy according to another embodiment of the invention.
• Fig. 3 shows schematically a method for generating electrical energy according to another embodiment of the invention.
• Fig. 4 shows schematically a method for generating electrical energy according to another embodiment of the invention.
• Fig. 5 shows schematically a method of generating electrical energy according to another embodiment of the invention.
• Fig. 6 shows schematically a method of generating electrical energy according to another embodiment of the invention.
• Fig. 7 shows schematically a method for generating electrical energy according to another embodiment of the invention.
• Fig. 8 shows schematically a method of generating electrical energy according to another embodiment of the invention.
• Fig. 9 shows process exchange diagrams according to embodiments of the invention.
• Fig. 1 shows schematically a process for producing electricity by recovering cold from hydrocarbon streams F2, F1 used as cold streams, i. e. cold springs, in a combination of a first and second Rankine cycle.
• Rankine cycles are implemented in at least one heat exchange device, which can be any device comprising passages suitable for the flow of several fluids and allowing direct or indirect heat exchange between said fluids.
• a method according to the invention can comprise a number greater than two Rankine cycles combined according to the same principles as those set out below in the case of two Rankine cycles.
• the cold streams F2, F1 can be natural gas.
• the various fluids of the process circulate in one or more heat exchangers of the brazed plate and fin type, advantageously formed of aluminum. These exchangers make it possible to work under low temperature differences and with reduced pressure drops, which improves the energy performance of the liquefaction process described above. Plate heat exchangers also offer the advantage of obtaining very compact devices offering a large exchange surface in a limited volume.
• exchangers comprise a stack of plates which extend in two dimensions, length and width, thus constituting a stack of several series of passages, some being intended for the circulation of a circulating fluid, in this case the working fluid. cycle, others being intended for the circulation of a refrigerant, in this case cryogenic liquid such as liquefied natural gas to be vaporized.
• Heat exchange structures such as heat exchange waves or fins, are generally arranged in the passages of the exchanger. These structures include fins that extend between the plates of the exchanger and increase the heat exchange surface of the exchanger.
• heat exchangers can however be used, such as plate heat exchangers, shell and tube heat exchangers, or “core in kettle” type assemblies. That is to say plate or plate and fin exchangers embedded in a shell in which the refrigerant vaporizes.
• Fig. 1 shows schematically an embodiment in which a first Rankine cycle is implemented by means of a first exchanger E1 and a second exchanger E2.
• the exchangers E1, E2 each comprise a stack of several plates (not visible) arranged parallel one above the other with spacing in a so-called stacking direction, which is orthogonal to the plates.
• a plurality of passages are thus obtained for the fluids of the process which are placed in an indirect heat exchange relationship via the plates.
• a passage is formed between two adjacent plates.
• the distance between two successive plates is small compared to the length and the width of each successive plate, so that each passage of the exchanger has a parallelepipedal and flat shape.
• the passages intended for the circulation of the same fluid form a series of passages.
• Each exchanger comprises several series of passages configured to channel the different fluids of the process parallel to an overall direction of flow z, the passages of a series being arranged, in whole or in part, alternately and / or adjacent to all or part of the passages of another series, that is to say intended for the flow of another fluid.
• the leaktightness of the passages along the edges of the plates is generally ensured by lateral and longitudinal sealing bars fixed to the plates.
• the side sealing bars do not completely seal off the passages but leave inlet and outlet openings for the introduction and discharge of fluids.
• These inlet and outlet openings are joined by collectors, generally semi-tubular in shape, ensuring a homogeneous distribution and recovery of the fluid over all the passages of the same series.
• collectors generally semi-tubular in shape
• the first exchanger E1 acts as a vaporizer in the first Rankine cycle. As seen in Fig. 1, a first working fluid W1 circulates in at least one passage 1 from an inlet 1 1 to an outlet 12. A first hot stream is introduced into the first exchanger from an inlet 21 to an outlet 22. The first working fluid W1 is vaporized by heat exchange with the first hot stream C1.
• the first vaporized working fluid W1 is expanded in a first expansion member, preferably a turbine, coupled to a first electrical generator G converting the kinetic energy produced by the expanded fluid into electrical energy.
• a first expansion member preferably a turbine
• the first working fluid W1 is introduced into the second heat exchanger E2 from an inlet 31 to an outlet 32 of at least a third passage 3.
• the first working fluid W1 is put into operation. heat exchange relationship with a first cold stream F1 flowing from at least a fourth passage 4 of the second exchanger E2 from an inlet 41 to an outlet 42.
• the first working fluid W1 is condensed by heating the first cold stream F1 and leaves the outlet 32 to be then returned to the first exchanger E1, after pressurization by a pressure-lifting member such as a pump, which closes the first cycle.
• a pressure-lifting member such as a pump
• hot stream or “cold stream” is meant a stream formed from one or more fluids providing a source of heat or cold by heat exchange with another fluid.
• a second working fluid W2 preferably of a composition different from that of the first working fluid W1 is introduced into the second exchanger E2 through an inlet 51 to an outlet 52 and circulates in at least a fifth passage 5 in which it is vaporized by heat exchange with the first working fluid W1 introduced into the second exchanger E2, said working fluid being cooled and condensed in the third passage 3.
• the second exchanger E2 simultaneously acts as a condenser for the first cycle and vaporizer for the second cycle.
• the second working fluid W2 is expanded according to the same principles as the first cycle and introduced, optionally in the two-phase state, with or without prior separation of the phases of said two-phase fluid, into a third heat exchanger E3 from an inlet 61 to an outlet 62 of at least a sixth passage 6 in which it is condensed by heating a second cold stream F2 flowing in at least a seventh passage.
• the third exchanger forms the condenser of the second cycle.
• the second working fluid W2 from the outlet 62 is pumped by a pressure lifting member and reintroduced through the inlet 51 of passage 5, which closes the second cycle.
• the structural characteristics described above for the E1 and E2 exchangers are applicable in whole or in part to E3.
• the first cold stream F1 of the first Rankine cycle is formed by the second cold stream F2 issuing from the second Rankine cycle, that is to say that the same cold current supplies the cycles in series, in which it is at least partially vaporized and gradually reheated against the second and first working fluids W2, W1, that is to say by heat exchange with said fluids.
• F1 can therefore optionally be a two-phase current.
• the first working fluid W1 introduced into the third passage 3 of the second exchanger is used to form at least part, preferably all, of the hot stream of the second Rankine cycle.
• the hot spring of second cycle is thus provided at least in part by the cooling and condensation of the working fluid of the first cycle.
• Such an arrangement makes it possible to regasify the cold stream while ensuring a more efficient recovery of the cold over the entire temperature gradient between the inlet temperature of the cold stream F2 in the at least a seventh pass and the temperature of the cold stream F1 at the output of at least a fourth pass.
• the recovery of the frigories from the cold stream takes place separately on portions of passages 7, 4 where it has different temperature levels. It is then possible to best adapt the characteristics of each of the first and second working fluids, so that they exhibit boiling temperatures adapted to these temperature levels.
• a large degree of freedom is thus available to increase the energy efficiency of the process, in particular by adjusting the temperatures, the pressures and / or the compositions of the working fluids according to the characteristics of the cold stream F2 to be heated, in particular its pressure, its temperature, its composition ...
• the second cold stream F2 can be vaporized in whole or in part and / or reheated in the second Rankine cycle (passage 7) by heat exchange with the second fluid W2.
• the first cold stream F1 can be vaporized in whole or in part and / or reheated (passage 4) in the first Rankine cycle by heat exchange with the first fluid W1.
• the first cold stream F1 exiting at 42 from the fourth passage 4 is introduced into at least an eighth passage 8 of the first exchanger E1, in order to continue its heating there against the first hot stream C1.
• This is advantageous in cases where the temperature obtained at the outlet 42 of the exchanger E2 is too low and incompatible with the material making up the distribution network, in particular in the case of a natural gas distribution network.
• the cold stream F1 recovered at the end of the outlets 42 or 82 feeds at least one pipe of a fluid distribution network, in particular a hydrocarbon distribution network such as natural gas.
• Fig. 2 shows an alternative embodiment in which the first cold stream F1 continues to heat up in a fourth exchanger E1 ′ physically distinct from the first exchanger E1.
• the exchanger E1 ' comprises the passages 8 for the circulation of the first cold stream F1 and additional passages 2' for the introduction of a first additional hot stream C1 'distinct from the hot stream C1.
• This configuration offers the advantage of being able to use, for the exchangers E1 and E1 ′, simpler technologies such as “shell and tube” type exchangers in which only two fluids circulate. Note that such a variant is applicable to other embodiments, in particular the one illustrated by FIG. 4.
• the inlets and outlets of the condensation passages 3, 6 are arranged so that the first and second working fluids W1, W2 flow, during steps c) and g) in countercurrent with the first and second currents cold F1, F2 respectively.
• the inlets and outlets of the reheating passages 4, 7, 1, 5 are arranged so that the first and second working fluids W1, W2 circulate, during steps a) and e) in co-current with the first and second cold currents F1, F2 respectively.
• the hot currents of the cycles circulate against the current of the working fluids vaporized in each cycle.
• Fig. 3 in particular shows an advantageous embodiment in which the first working fluid W1 condensed out of the passage 3 is reintroduced into the second exchanger E2 to circulate therein in at least a ninth passage 9 between an inlet 91 and an outlet 92, before be reintroduced in passage 1.
• This configuration is preferred when the working fluid W1 is not a pure substance but a mixture of several constituents, because it offers the advantage of further heating the outlet temperature of the working fluid.
• the second working fluid W2 condensed out of the passages 6 can also be reintroduced into at least a tenth passage 10 of the third exchanger, before being reintroduced into the fifth passage 5.
• Either of the first and second condensed working fluids may be subject to such re-introductions.
• the reintroduction of the condensed fluid (s) into the exchanger (s) concerned makes it possible to heat them and to maximize their outlet temperature at the hot end and therefore the production of electricity during their expansion.
• a reintroduction is carried out for each of the working fluids, which makes the process even more favorable in terms of energy.
• Fig. 1 to Fig. 4 illustrate configurations in which the Rankine cycles are operated in exchangers forming physically distinct entities, that is to say, in the case of plate or plate and fin exchangers, each forming at least one distinct stack of plates and passages.
• This embodiment with separate exchangers can be implemented in particular in the case where the passages are formed within exchangers other types than plate or plate and fin exchangers, such as shell and tube exchangers, finned or core-in-kettle type.
• the passages can be formed by the spaces in, around and between the tubes.
• Fig. 5 shows an embodiment in which the second exchanger E2 and the third exchanger E3 form the same common exchanger E.
• the second cold stream F2 circulates from a first inlet 71 located at the cold end of the exchanger E, that is to say the entry point into the exchanger where a fluid, here the stream F2, is introduced. at the lowest temperature of all the temperatures of the exchanger E.
• the second cold stream F2 leaves via a first outlet 42 of the exchanger E, the passages 4 being formed between the same plates of the exchanger E as the passages 7 and being arranged in the continuity of the passages 7.
• each passage of said series forms an extension of a corresponding passage of the other series, and therefore one and the same passage of the exchanger E formed between two same plates.
• a passage 4 and a passage 7 thus forming one and the same passage of the exchanger E delimited between two same plates of the exchanger E and extending from the inlet 71 to the outlet 42.
• the first working fluid W1 is introduced after expansion through a second inlet 31 located at the hot end of the exchanger E and having the highest temperature of all the temperatures of the exchanger E.
• the first working fluid W1 circulates in the third passages 3 up to a second outlet 32 arranged at a first intermediate level located, in the direction of flow z, between the cold end and the hot end of the exchanger E.
• the first working fluid W1 recovered at the outlet 32 can be reintroduced, after pumping, into the passages 9 of the exchanger E before supplying the inlet 1 1 of the first exchanger E1, as illustrated in FIG. 5, or supply the input 1 1 directly (not shown).
• the second working fluid W2 is introduced after expansion, optionally two-phase and optionally with separation of its gas and liquid phases, into the exchanger E through a third inlet 61 arranged at a second intermediate level located, in the direction of flow z, between the first intermediate level and the cold end of the exchanger E.
• the second working fluid W2 is recovered after having been condensed in the passages 6 at the outlet 62 can be reintroduced, after pumping, into the passages 10 by an inlet 101 located at the cold end of the exchanger E, before supplying the passages 5, as illustrated in FIG. 5.
• the passages 5 are arranged in the continuity of the passages 10.
• the second fluid W2 can also directly feed an inlet of the passages 5 located at an intermediate level of the exchanger E (not shown).
• Fig. 6 represents an embodiment in which the first exchanger E1, the second exchanger E2 and the third exchanger E3 form the same common exchanger E.
• the first hot stream C1 is introduced from a fourth inlet 21 located at the hot end of the exchanger E.
• the first working fluid W1 is introduced after expansion, optionally in the two-phase state, by a second inlet 31 arranged at a third intermediate level located between the cold end and the hot end and exits from said exchanger E by a second outlet 32 arranged at a first intermediate level located between the third intermediate level and the cold end of the exchanger E.
• the second working fluid W2 is introduced after expansion, possibly in the two-phase state, by a third inlet 61 arranged at a second intermediate level located, in the direction flow z, between the first intermediate level and the cold end of exchanger E.
• the first working fluid W1 recovered in liquid form at the outlet 32 can be reintroduced after pumping into passages 9 through an inlet 91 before supplying the passages 1, as illustrated in Fig. 6.
• the passages 1 are arranged in the continuity of the passages 9.
• the first fluid W1 can also directly feed an inlet of the passages 1 located at an intermediate level of the exchanger E (not shown).
• the second working fluid W2 recovered at the outlet 62 in liquid form can be reintroduced after pumping into the passages 10 through an inlet 101 located at the cold end of the exchanger E, before supplying the passages 5, as illustrated in Fig. 6.
• the passages 5 are arranged in the continuity of the passages 10.
• the second fluid W2 can also directly feed an inlet of the passages 5 located at an intermediate level of the exchanger E (not shown).
• Fig. 7 and Fig. 8 illustrate embodiments in which one uses the same generator coupled both to the first expansion member and to the second expansion member.
• the first and second generators are therefore combined. This saves a generator and simplifies installation. This arrangement is possible because the two cycles of electricity generation have a generally simultaneous mode of operation.
• the second cold stream F2 may be a stream of liquefied hydrocarbons such as liquefied natural gas or a stream of cryogenic liquid such as a stream of liquefied nitrogen, a stream of liquefied oxygen, a stream of liquefied hydrogen.
• the temperature for introducing the second cold stream F2 into the at least a seventh passage 7 is less than -100 ° C.
• the cold stream F2, F1 is formed from a stream of hydrocarbons, in particular natural gas, preferably comprising, in molar fraction, at least 60% methane (CFU), preferably at least 80%.
• Natural gas can optionally include ethane (C2H6), propane (C3H8), butane (nC 4 Hio) or isobutane (1C4H 10), nitrogen, preferably in amounts between 0 and 10% (mol%). Thanks to the process of the invention, the necessary regasification is carried out before injecting the natural gas into the distribution network, while upgrading the frigories of the liquefied natural gas.
• Cold currents of another nature can advantageously feed the process according to the invention to be vaporized before use.
• liquid oxygen, liquid nitrogen, or even liquid hydrogen can be used.
• the vaporization of such liquids can help ensure a continuity of gas supply when a production plant is shut down, and save some of the energy spent on building up liquid stocks.
• the method according to the invention implements three Rankine cycles with a third Rankine cycle operated upstream of the second Rankine cycle. More precisely, with reference to the configuration according to FIG. 1 without being illustrated there, the second cold stream F2 is introduced into a fifth exchanger E5 arranged upstream of the third exchanger E3. A third working fluid W3 is introduced at a third high pressure Ph3 into at least one additional passage of the third exchanger E3 and vaporizes at least in part against the second working fluid W2 circulating in the at least a sixth passage 6 of the third exchanger E3. The second working fluid W2 thus acts as the third hot stream in the third Rankine cycle.
• the third working fluid W3 leaving the additional passages is expanded to a third low pressure Pb3 in a third expansion member cooperating with a third electrical generator, possibly combined with at least one other generator, so as to produce energy electric.
• the expanded working fluid W3 is introduced into the fourth exchanger and condenses at least in part against the third cold stream F3 which heats up and / or vaporizes at least in part by heat exchange with W3.
• the third working fluid W3 thus condensed leaves the fourth exchanger and is reintroduced, after raising the pressure to the third high pressure Ph3 in the third exchanger E3.
• This embodiment is particularly advantageous in the case where the cold stream to be re-vaporized is a cryogenic liquid at very low temperature, that is to say a temperature which may be less than -170 ° C, or even less than -200 ° vs.
• a reheating of said cold stream is therefore carried out against a third working fluid condensing in a third Rankine cycle then against the second working fluid condensing in the second Rankine cycle then against the first working fluid W1 condensing in the first Rankine cycle.
• the stream will advantageously be reheated by approximately - 250 to -170 ° C in a third thermodynamic cycle, the flow of cryogenic liquid heating up playing the role of the cold source of the cycle, which makes it possible to further increase the production of electricity per unit of vaporized flow.
• a reheating of approximately -170 to -90 ° C approximately in the second Rankine cycle then a reheating of approximately -90 to -50 ° C in the first Rankine cycle .
• the third Rankine cycle is not an organic cycle, the third working fluid W3 preferably being free of organic component.
• the first working fluid W1 and the second working fluid W2 are organic fluids, that is to say fluids comprising one or more organic components such as hydrocarbons.
• Rankine cycles of the process according to the invention are not organic cycles.
• the working fluid of the cycle working at the lowest temperature may include one or more components such as hydrogen, nitrogen, argon, helium, neon in addition to or substitution of all or part of the organic components. It will thus be possible to envisage working with working fluids free of organic components.
• first fluid W1 and / or the second fluid W2 it is possible to use pure substances of a different nature to form the first fluid W1 and / or the second fluid W2.
• ethylene can be used as the second working fluid W2 and ethane as the first working fluid W1.
• This choice can be explained by the physical properties of these constituents, which have saturated vapor pressures for the temperature range swept by the LNG vaporization compatible with good mechanical strength of brazed aluminum exchangers and expansion turbine components.
• ORC cycles allows the design of compact and efficient systems.
• working fluids of different compositions are preferably used in the different Rankine cycles but it should be noted that it is still possible to envisage using working fluids of the same composition, by then adjusting the pressures in an appropriate manner. operating procedures of these fluids. This is possible for relatively small temperature differences between the cold and hot currents of the cycles, for example when the second cold stream is a liquefied gas at very high pressure and the first hot stream is sea water at a sufficiently low temperature. .
• mixed working fluids comprising respectively a first mixture of hydrocarbons and a second mixture of hydrocarbons, preferably the first and the second mixture of hydrocarbons each contain at least two hydrocarbons chosen from methane. , ethylene (C2H4) propane, ethane, propylene, butene, butane or isobutane.
• the first working fluid W1 and the second working fluid W2 can optionally comprise at least one additional component chosen from hydrogen, nitrogen, argon, helium, neon, in addition to or substitution of the organic components, and this in particular if the cryogenic liquid to be vaporized has a lower boiling point than that of methane.
• mixed working fluids makes it possible to reduce the energy losses linked to the irreversibility of heat exchanges between cold and hot fluids by reducing the temperature differences between the cold currents and the fluids working at each point depending on the length of the exchanger.
• the compositions, pressures before and after expansion and / or temperatures of each fluid can be adapted in order to ensure the best possible energy recovery.
• the working fluids are mixed, ie are mixtures, they leave the liquid exchanger (s) at very low temperature and that it is then advantageous to re-introduce the condensed fluids into the fluid (s). heat exchangers concerned in order to heat them and maximize their outlet temperature at the hot end and therefore the production of electricity during their expansion in the turbine.
• the proportions in mole fractions (%) of the components of the first mixture of hydrocarbons can be (mole%):
• Methane 0 to 20%, preferably 0 to 10%
• Propane 20 to 60%, preferably 30 to 50%
• Ethylene 20 to 60%, preferably 30 to 50%
• Isobutane 0 to 20%, preferably 0 to 10%
• the proportions in mole fractions (%) of the components of the second mixture of hydrocarbons can be:
• Methane 20 to 60%, preferably 30 to 50%
• Propane 0 to 20%, preferably 0 to 10%
• Ethylene 20 to 70%, preferably 30 to 60%
• the first hot stream C1, and where appropriate the additional hot stream C1 ’ are formed from seawater, preferably at an inlet temperature in the exchanger of between 10 and 30 ° C.
• the second cold stream F2 is a stream of hydrocarbons introduced fully liquefied at inlet 71 at a temperature between -140 and -170 ° C.
• the temperature of the fluid at the inlet 71 is preferably the order of its equilibrium temperature at the storage pressure.
• the first cold stream F1 has a temperature between -85 and -105 ° C at the outlet 72 of the third exchanger E3, a temperature between -10 and -20 ° C at the outlet 42 of the second exchanger E2 or of exchanger E and / or a temperature between 5 and 25 ° C at the outlet 82 of the first exchanger E3 or exchanger E, to be introduced at this temperature into a distribution network.
• the first cold stream F1 leaves completely vaporized through the outlet 82 or the outlet 42.
• the second cold stream and the first cold stream have pressures of between 10 and 100 bar throughout the passages 7, 4, 8 in which they flow.
• the first working fluid W1 has, after its condensation in the third passage 3, a first temperature T1.
• the second working fluid W2 has, after its condensation in the sixth passage 6, a second temperature T2, with T2 less than T1.
• T1 is between -1 10 and -80 ° C and T2 between -120 and -160 ° C.
• the first working fluid W1 leaves vaporized from the first passage 1 at a temperature of between 5 and 25 ° C and / or the second working fluid W2 leaves vaporized from the fifth passage 5 at a temperature of between 0 and -30 ° vs.
• the first working fluid W1 and the second working fluid W2 leave the third passage 3 and the sixth passage 6 respectively at first and second so-called low pressures Pb1, Pb2 and enter the first passage 1 and the fifth passage 5 respectively at first and second so-called high pressures Ph1, Ph2, with Ph1> Pb1 and Ph2> Pb2.
• the first and / or second high pressures Ph1, Ph2 are between 10 and 40 bar, preferably less than 30 bar, more preferably less than 20 bar and / or the first and / or second low pressures Pb1, Pb2 are between 1 and 5 bar.
• the first high pressure Ph1 is greater than the first low pressure Pb1 by a multiplying factor of between 2.5 and 15 and / or the second high pressure Ph2 is greater than the second low pressure Pb2 by a multiplying factor between 2.5 and 15, preferably between 2.5 and 10.
• the only working fluid was propane.
• the pressure of the working fluid W1 was 7.5 bar at the inlet of the vaporization exchanger and 1.5 bar at the outlet 32 of the condensation exchanger.
• the hot stream was seawater at a pressure of 5 bar and a temperature of 23 ° C at the inlet to the vaporization exchanger.
• the first W1 working fluid was ethane.
• the second working fluid was ethylene.
• the pressure of the first working fluid W1 was 27 bar at the inlet 1 1 and 5.8 bar at the outlet 32.
• the pressure of the second working fluid W2 was 8.1 bar at the inlet 51 and 2.1 bar at outlet 62.
• the natural gas pressure was 90 bar at inlet 71 and 89 bar at outlet 82.
• Hot stream C1 was sea water at a pressure of 5 bar in inlet and outlet of the passages 2. Table 1 shows the fluid temperatures calculated at the inlet or outlet of different passages.
• the first working fluid W1 was a mixture of hydrocarbons comprising 46% ethylene, 38% propane, 8% methane, 8% isobutane (mol%).
• the second working fluid was a mixture of hydrocarbons comprising 55.4% ethylene, 41% methane, 3.6% propane (mol%).
• the pressure of the first working fluid W1 was 12 bar at the inlet 91 and 4.2 bar at the outlet 32.
• the pressure of the second working fluid W2 was 16.7 bar at the inlet 101 and 1 , 7 bar at outlet 62.
• the natural gas pressure was 90 bar at inlet 71 and 89.5 bar at outlet 82.
• the hot stream C1 was sea water at a pressure of 5 bar at the inlet and outlet of passages 2. Table 2 shows the fluid temperatures calculated at the inlet or outlet of various passages.
• the energy efficiency of the second Rankine cycle was 0.0045 kWh / Nm 3 and the energy efficiency of the first Rankine cycle was 0.0134 kWh / Nm 3 , for a total efficiency of 0, 0179 kWh / Nm 3 , representing a gain of around 12% compared to simulation n ° 1.
• the energy efficiency of the second Rankine cycle was 0.012 kWh / Nm 3 and the energy efficiency of the first Rankine cycle was 0.021 kWh / Nm 3 , for a total efficiency of 0.033 kWh / Nm 3 , representing a gain of around 106% compared to simulation n ° 1.
• first working fluid and a second mixed W2 working fluid makes it possible to significantly increase the performance of the process, thanks to the improvement of the exchange diagrams between the liquefied natural gas and the fluids of job.
• the schemes for reintroducing the working fluids into the exchange passages as described above also contribute to the greater energy efficiency of the process.
• Fig. 9 shows a comparison of the exchange diagrams Heat exchanged (“heat flow”) - Temperature (DH - T), or enthalpy curves, obtained on the one hand with a combination of cycles with pure working fluids according to simulation n ° 2 (in (a)) and on the other hand with a combination of cycles with mixed working fluids according to simulation n ° 3 (in (b)).
• the diagrams shown are obtained for a flow rate of 3000 Nm 3 / h of treated LNG (ie approximately a 1/100 scale of an industrial unit).
• Curves A, B, C, D illustrate the evolution of the quantity of heat exchanged as a function of temperature for all the refrigerants which heat up and / or vaporize in the processes, including LNG (curves A and C) and all the circulating fluids which cool and / or condense in the processes, including the first and second working fluids (curves B and D), for each of the two simulated configurations. It can be seen in Fig. 9 (b) that the average temperature difference is significantly reduced by the use of working fluids composed of a mixture of constituents, which explains the better efficiency of this cycle.

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