EP3045849A2 - A plant for liquefying methane gas - Google Patents
A plant for liquefying methane gas Download PDFInfo
- Publication number
- EP3045849A2 EP3045849A2 EP16151024.3A EP16151024A EP3045849A2 EP 3045849 A2 EP3045849 A2 EP 3045849A2 EP 16151024 A EP16151024 A EP 16151024A EP 3045849 A2 EP3045849 A2 EP 3045849A2
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- European Patent Office
- Prior art keywords
- flow
- methane
- cryogenic
- outlet
- section
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 170
- 230000006835 compression Effects 0.000 claims abstract description 36
- 238000007906 compression Methods 0.000 claims abstract description 36
- 238000004064 recycling Methods 0.000 claims abstract description 21
- 238000001816 cooling Methods 0.000 claims abstract description 19
- 239000007788 liquid Substances 0.000 claims description 8
- 238000011144 upstream manufacturing Methods 0.000 claims description 2
- 239000007789 gas Substances 0.000 description 21
- 239000007792 gaseous phase Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 239000003949 liquefied natural gas Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 230000003213 activating effect Effects 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000011282 treatment Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 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
- 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
- F25J1/0032—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
- F25J1/004—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by flash gas recovery
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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
- F25J1/0032—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration"
- F25J1/0045—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the kind of cold generation within the liquefaction unit for compensating heat leaks and liquid production using the feed stream itself or separated fractions from it, i.e. "internal refrigeration" by vaporising a liquid return 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
- F25J1/02—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
- F25J1/0201—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using only internal refrigeration means, i.e. without external refrigeration
- F25J1/0202—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using only internal refrigeration means, i.e. without external refrigeration in a quasi-closed internal refrigeration loop
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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
- F25J1/0228—Coupling of the liquefaction unit to other units or processes, so-called integrated processes
- F25J1/0229—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock
- F25J1/023—Integration with a unit for using hydrocarbons, e.g. consuming hydrocarbons as feed stock for the combustion as fuels, i.e. integration with the fuel gas system
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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.
- F25J1/0281—Compression of refrigerant or internal recycle fluid, e.g. kind of compressor, accumulator, suction drum etc. characterised by the type of prime driver, e.g. hot gas expander
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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
- F25J2210/00—Processes characterised by the type or other details of the feed stream
- F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
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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
- F25J2220/00—Processes or apparatus involving steps for the removal of impurities
- F25J2220/60—Separating impurities from natural gas, e.g. mercury, cyclic hydrocarbons
- F25J2220/66—Separating acid gases, e.g. CO2, SO2, H2S or RSH
Definitions
- LNG liquefied natural gas
- a temperature of a little less than -160°C is required so that the gas can be stored at atmospheric pressure, or a little above.
- the present invention relates to a medium-sized plant for methane gas liquefaction, the methane being collected from a low-pressure supply network.
- the prior art includes methane liquefaction plants which comprise a compression unit, drawn by a suitable motor, and devices for generating the required frigories (for example turbines, Joule-Thompson valves) in which a suitable gas is used.
- methane liquefaction plants which comprise a compression unit, drawn by a suitable motor, and devices for generating the required frigories (for example turbines, Joule-Thompson valves) in which a suitable gas is used.
- These motors use relative energy sources, different to methane gas, and gases for generating the frigories, different to the gas to be liquefied, in the present case methane.
- the aim of the invention is to obviate the drawbacks of the prior art by using a plant for liquefaction of methane gas that can realise small or medium-sized flows, the functioning of which is actuated using only methane gas collected from a supply network.
- a further aim is to provide a plant for methane liquefaction that is functional and reliable and able to guarantee an average daily productivity of liquefied methane gas, for example 5 ⁇ 10 tonnes a day.
- the plant of the invention is constituted by a first cryogenic section 200, a second cryogenic section 300 and a storage section 400.
- 1 denotes a pipeline which collects a flow ⁇ N of methane at low pressure (3-4 bar) and ambient temperature (for example about 15°C).
- a fraction of the network flow ⁇ N denoted by ⁇ F , supplies the gas motor M.
- the remaining part ⁇ T of the network ⁇ N crosses a filter 2, precisely an adsorbent bed molecular filter which eliminates all damaging components from the flow ⁇ T (water, carbon dioxide, sulphurous compounds, etc.); a flow of purified methane ⁇ P reaches the filter outlet 2.
- the comburent part ⁇ S of the above-mentioned damaging components goes to supply, together with the flow ⁇ F , the gas motor M which is supplied with a flow ⁇ M .
- the motor M draws in rotation an intercooled reciprocating compressor 5 with four compression stages A, B, C, D, respectively a first, second, third and fourth.
- the first stage (or first phase) of compression is supplied, at an inlet thereof, by the flow ⁇ P coming from the filter 2 and at the remaining inlet by a recycling flow ⁇ 2 (of which more in the following) coming from the first cryogenic section 200.
- the flow ⁇ A in outlet from the first stage A is cooled by a first heat exchanger 11 (air cooler) and sent to one of the inlets of the second compression stage B; a further recycling flow ⁇ 4 (of which more in the following) arrives at the second inlet, coming from the first cryogenic section 200.
- the flow ⁇ B in outlet from the second stage B (at a pressure of 33 bar) is cooled by a second heat exchanger 12 (air cooler) and sent to one of the inlets of the third compression stage C; a further inlet of the flow is supplied by a further recycling flow ⁇ 7 (of which more in the following) coming from the first cryogenic section 200.
- the pressure at outlet from the third stage C is about 90 bar.
- the flow ⁇ C in outlet from the third stage C is cooled by means of a third heat exchanger 13 and sent to the inlet of the fourth stage D.
- the flow ⁇ or main flow in outlet from the fourth stage, is cooled by a fourth heat exchanger (or chiller) 14; this main flow has a pressure of about 250 bar and a temperature of -5°C.
- the main flow ⁇ involves, in order, a first circuit C 1 , included in a first cryogenic exchanger 250 that is a part of the first cryogenic section 200 and, by means of a pipeline 17, a first Joule-Thompson valve 10.
- the separator supplies two pipelines 18, 19 crossed by corresponding flows ⁇ 1 , ⁇ 2 , respectively a first and a second flow.
- the first flow ⁇ 1 is at a pressure of about 33 bar and a temperature of about -96°C.
- the second flow ⁇ 2 comprises traces of methane vapours and methane liquid; the second flow involves a second circuit C 2 of the first main cryogenic heat exchanger 250, by crossing which it yields frigories and therefore heats up; this leads to a passage of the methane vapours and the traces of methane liquids from the gaseous phase.
- the second flow ⁇ 2 via the pipeline 18, is sent on to one of the inlets of the first compression stage A and thus to constitute a recycling flow.
- the first flow ⁇ 1 is sent to the second cryogenic section 300 by means of the pipeline 19 which supplies a second Joules-Thompson valve 20 the function of which consists in further lowering both the methane pressure (about 15 bar) and the temperature thereof (about -15°C.
- the first flow ⁇ 1 downstream of the second valve, is sent on to a second liquid-vapour separator 16 which carries out the same functions as the first separator 15, as it supplies two pipelines 21, 27 involved by the relative third and fourth methane flows ⁇ 3 , ⁇ 4 .
- the fourth flow ⁇ 4 is sent into the first cryogenic exchanger 250, more precisely the third circuit C 3 comprised therein; the fourth flow ⁇ 4 renders frigories to the exchanger 250, and therefore heats up, which enables passage of any methane vapour traces and/or methane drops in the gaseous phase thereof.
- the fourth flow ⁇ 4 in outlet from the exchanger 250, is sent on to one of the inlets of the second compression stage B to constitute a recycling flow.
- the pipeline 21, crossed by the third flow ⁇ 3 supplies two pipelines 22, 23, at least one of which is regulated by regulating means 70, the function of which is to regulate the fifth and sixth flow rates ⁇ 5 , ⁇ 6 , which cross the pipelines.
- the fifth flow ⁇ 5 is destined to be liquefied; for this purpose it is necessary to cool it further, at least down to -156°C, as well as reducing the pressure thereof (about 1.8 bar).
- the above-mentioned cooling is actuated first by a second cryogenic heat exchanger 350 (located in the second cryogenic section 300) and lastly by a third Joule-Thompson valve 30 (see figure 2 ).
- the second cryogenic exchanger 350 involves two circuits F 1 ,F 2 , being a fifth and sixth circuit, with the fifth circuit F 1 , crossed by the fifth flow ⁇ 5 .
- the second circuit F 2 is crossed by a seventh flow ⁇ 7 which is the sum of the sixth flow ⁇ 6 and a flow of methane vapours ⁇ VM of which more in the following.
- the flow ⁇ 6 is destined, in the exchanger 350, to provide the frigories for cooling the fifth flow ⁇ 5 ; for this purpose (see figure 2 ) a fourth Joule-Thompson valve 50 is included in the pipeline 23, which cools the sixth flow ⁇ 6 .
- the flow ⁇ 7 enters the relative circuit F 2 at about -142°C, crosses it and heats up; it follows that the steam ⁇ VM threshold passes to the gaseous phase of the methane.
- the seventh flow ⁇ 7 is directed, by means of a pipeline 24, into the fourth circuit C 4 of the first cryogenic exchanger 250 where it renders further frigories; at the outlet of the fourth circuit C 4 , the flow ⁇ 7 is sent to one of the inlets of the third compression stage C to constitute a recycling flow.
- the fifth flow ⁇ 5 at the outlet of the second cryogenic exchanger 350 has a temperature and pressure that are respectively about -138°C and 15 bar.
- the third Joule-Thompson valve 30 causes a further lowering of the temperature (up to - 156°C) and the pressure (about 1.8 bar) which causes liquefaction of the methane; flow ⁇ L .
- the flow of liquid methane ⁇ L is conveyed into the storage station 400, precisely into a cryogenic tank 450 ( figure 2 ).
- the methane vapours, flow ⁇ VM which are generated by the methane contained in the tank, are conveyed by means of a pipeline 34 into the sixth circuit F 2 of the second cryogenic exchanger 350 to constitute the seventh flow ⁇ 7 which has already been mentioned in the foregoing.
- the first flow ⁇ 1 is about 39% of ⁇ ; obviously the recycling flow ⁇ 2 (the one sent to one of the inlets of the first stage A of the compressor 5) is 61 % of ⁇ .
- the third flow ⁇ 3 is about 29.5% of the main flow ⁇ , while the recycling flow ⁇ 4 (sent to one of the inlets of the second compression stage B) is 9.5% thereof.
- the flow ⁇ L of methane liquid is about 25.8% of the main flow, while the recycling flow ⁇ 7 (sent to one of the inlets of the third compression stage C) is about 3.7% thereof.
- a flow of methane is collected from the supply network 1 thereof that is such as to reintegrate the liquefied methane and so as to enable supply to the gas motor 10.
- the motor 10-compressor 5 group supplies the methane with the power required for circulating in the plant with the aim of cooling and liquefying an amount thereof.
- the lowering of the methane to cryogenic levels is entrusted to the main flow ⁇ , first flow ⁇ 1 and fifth flow ⁇ 5 which are cooled following the crossing of the corresponding first 10, second 20 and third 30 Joule-Thompson valve.
- the main flow ⁇ is also cooled by the first cryogenic exchanger 250 due to the frigories yielded thereto, more precisely the first circuit C 1 , from flows ⁇ 2 , ⁇ 4 , ⁇ 7 passing in circuits C 2 ,C 3 ,C 4 of the heat exchanger 250.
- the fifth flow ⁇ 5 is cooled, upstream of the third Joule-Thompson valve, by the second cryogenic exchanger 250; the cooling is made possible by the accentuated cooling of the sixth flow ⁇ 6 by means of the fourth Joule-Thompson valve 50.
- the plant of the invention comprises the above-mentioned power section 100, the first and second cryogenic section 300, 400 and lastly the storage section 400.
- the power section comprises the gas motor 10 supplied by the low-pressure methane gas network 1 and the comburent part ⁇ S separated from the filter 2 by the purified methane.
- the first cryogenic section 200 is supplied by the power section 100 via the main flow and, in turn, supplies the main flow via the recycling flows ⁇ 2 , ⁇ 4 , ⁇ 7 .
- the second cryogenic section 300 is supplied by the first cryogenic section via the main flow ⁇ 1 and, in turn, supplies the main flow via the recycling flows ⁇ 4 , ⁇ 7 .
- the storage section is supplied by the liquid flow ⁇ L coming from the second section 300, and in turn the second section 300 is supplied by the methane vapour flow ⁇ VM .
- the plant of the invention only uses the methane gas flow ⁇ N collected from the supply network 1.
- the motor 10, of the gas motor type, which provides the power to the plate is supplied by an amount of flow ⁇ F collected by the network that is mixed with the comburent substances ⁇ S separated by the methane gas by means of the filter 2.
- the above-described and illustrated plant is advantageously provided for obtaining medium liquefied methane gas flows, for example comprised between 5 and 20 tonnes of methane per day.
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Abstract
Description
- It is known that liquefied natural gas (LNG) is obtained by subjecting natural gas, following suitable purifying and dehydrating treatments, to successive cooling and liquefying stages.
- For liquefaction a temperature of a little less than -160°C is required so that the gas can be stored at atmospheric pressure, or a little above.
- The present invention relates to a medium-sized plant for methane gas liquefaction, the methane being collected from a low-pressure supply network.
- The prior art includes methane liquefaction plants which comprise a compression unit, drawn by a suitable motor, and devices for generating the required frigories (for example turbines, Joule-Thompson valves) in which a suitable gas is used.
- These motors use relative energy sources, different to methane gas, and gases for generating the frigories, different to the gas to be liquefied, in the present case methane.
- This leads to plant complications and drawbacks deriving from the need to include systems for supplying and storing of both the energy source for the motors and the gas for activating the sources of cooling generation.
- The aim of the invention is to obviate the drawbacks of the prior art by using a plant for liquefaction of methane gas that can realise small or medium-sized flows, the functioning of which is actuated using only methane gas collected from a supply network.
- A further aim is to provide a plant for methane liquefaction that is functional and reliable and able to guarantee an average daily productivity of liquefied methane gas, for example 5÷10 tonnes a day.
- The above-indicated aims are attained as set down in the contents of the claims.
- Further characteristics and advantages of the invention will emerge from the following description which makes reference to the accompanying tables of drawings in which:
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figure 1 schematically illustrates a possible functional diagram of the part of the plant termed "hot"; -
figure 2 schematically illustrates the remaining function part of the plant, the cryogenic part. - With reference to the figures of the drawings, the plant of the invention is constituted by a first cryogenic section 200, a second
cryogenic section 300 and astorage section 400. - In relation to the
power section - A fraction of the network flow φN, denoted by φF, supplies the gas motor M.
- The remaining part φT of the network φN crosses a
filter 2, precisely an adsorbent bed molecular filter which eliminates all damaging components from the flow φT (water, carbon dioxide, sulphurous compounds, etc.); a flow of purified methane φP reaches thefilter outlet 2. - The comburent part φS of the above-mentioned damaging components goes to supply, together with the flow φF, the gas motor M which is supplied with a flow φM.
- The motor M draws in rotation an intercooled
reciprocating compressor 5 with four compression stages A, B, C, D, respectively a first, second, third and fourth. - The first stage (or first phase) of compression is supplied, at an inlet thereof, by the flow φP coming from the
filter 2 and at the remaining inlet by a recycling flow φ2 (of which more in the following) coming from the first cryogenic section 200. - The flow φA in outlet from the first stage A is cooled by a first heat exchanger 11 (air cooler) and sent to one of the inlets of the second compression stage B; a further recycling flow φ4 (of which more in the following) arrives at the second inlet, coming from the first cryogenic section 200.
- The flow φB in outlet from the second stage B (at a pressure of 33 bar) is cooled by a second heat exchanger 12 (air cooler) and sent to one of the inlets of the third compression stage C; a further inlet of the flow is supplied by a further recycling flow φ7 (of which more in the following) coming from the first cryogenic section 200.
- The pressure at outlet from the third stage C is about 90 bar.
- The flow φC in outlet from the third stage C is cooled by means of a
third heat exchanger 13 and sent to the inlet of the fourth stage D. - The flow φ, or main flow in outlet from the fourth stage, is cooled by a fourth heat exchanger (or chiller) 14; this main flow has a pressure of about 250 bar and a temperature of -5°C.
- The main flow φ involves, in order, a first circuit C1, included in a first
cryogenic exchanger 250 that is a part of the first cryogenic section 200 and, by means of apipeline 17, a first Joule-Thompson valve 10. - In the
same pipeline 17, the main flow φ, downstream of thevalve 20, crosses a liquid-steam separator 15. - The separator supplies two
pipelines - The first flow φ1 is at a pressure of about 33 bar and a temperature of about -96°C.
- The second flow φ2 comprises traces of methane vapours and methane liquid; the second flow involves a second circuit C2 of the first main
cryogenic heat exchanger 250, by crossing which it yields frigories and therefore heats up; this leads to a passage of the methane vapours and the traces of methane liquids from the gaseous phase. - The second flow φ2, via the
pipeline 18, is sent on to one of the inlets of the first compression stage A and thus to constitute a recycling flow. - The first flow φ1 is sent to the second
cryogenic section 300 by means of thepipeline 19 which supplies a second Joules-Thompsonvalve 20 the function of which consists in further lowering both the methane pressure (about 15 bar) and the temperature thereof (about -15°C. - The first flow φ1, downstream of the second valve, is sent on to a second liquid-
vapour separator 16 which carries out the same functions as thefirst separator 15, as it supplies twopipelines - The fourth flow φ4 is sent into the first
cryogenic exchanger 250, more precisely the third circuit C3 comprised therein; the fourth flow φ4 renders frigories to theexchanger 250, and therefore heats up, which enables passage of any methane vapour traces and/or methane drops in the gaseous phase thereof. - The fourth flow φ4, in outlet from the
exchanger 250, is sent on to one of the inlets of the second compression stage B to constitute a recycling flow. - The
pipeline 21, crossed by the third flow φ3, supplies twopipelines means 70, the function of which is to regulate the fifth and sixth flow rates φ5, φ6, which cross the pipelines. - The fifth flow φ5 is destined to be liquefied; for this purpose it is necessary to cool it further, at least down to -156°C, as well as reducing the pressure thereof (about 1.8 bar).
- The above-mentioned cooling is actuated first by a second cryogenic heat exchanger 350 (located in the second cryogenic section 300) and lastly by a third Joule-Thompson valve 30 (see
figure 2 ). - The second
cryogenic exchanger 350 involves two circuits F1,F2, being a fifth and sixth circuit, with the fifth circuit F1, crossed by the fifth flow φ5. - The second circuit F2 is crossed by a seventh flow φ7 which is the sum of the sixth flow φ6 and a flow of methane vapours φVM of which more in the following.
- The flow φ6 is destined, in the
exchanger 350, to provide the frigories for cooling the fifth flow φ5; for this purpose (seefigure 2 ) a fourth Joule-Thompsonvalve 50 is included in thepipeline 23, which cools the sixth flow φ6. - The flow φ7 enters the relative circuit F2 at about -142°C, crosses it and heats up; it follows that the steam φVM threshold passes to the gaseous phase of the methane.
- The seventh flow φ7 is directed, by means of a
pipeline 24, into the fourth circuit C4 of the firstcryogenic exchanger 250 where it renders further frigories; at the outlet of the fourth circuit C4, the flow φ7 is sent to one of the inlets of the third compression stage C to constitute a recycling flow. - The fifth flow φ5 at the outlet of the second
cryogenic exchanger 350 has a temperature and pressure that are respectively about -138°C and 15 bar. - The third Joule-Thompson
valve 30 causes a further lowering of the temperature (up to - 156°C) and the pressure (about 1.8 bar) which causes liquefaction of the methane; flow φL. - The flow of liquid methane φL is conveyed into the
storage station 400, precisely into a cryogenic tank 450 (figure 2 ). - The methane vapours, flow φVM, which are generated by the methane contained in the tank, are conveyed by means of a
pipeline 34 into the sixth circuit F2 of the secondcryogenic exchanger 350 to constitute the seventh flow φ7 which has already been mentioned in the foregoing. - By way of example, taking as reference the main flow φ, the first flow φ1 is about 39% of φ; obviously the recycling flow φ2 (the one sent to one of the inlets of the first stage A of the compressor 5) is 61 % of φ.
- The third flow φ3 is about 29.5% of the main flow φ, while the recycling flow φ4 (sent to one of the inlets of the second compression stage B) is 9.5% thereof.
- The flow φL of methane liquid is about 25.8% of the main flow, while the recycling flow φ7 (sent to one of the inlets of the third compression stage C) is about 3.7% thereof.
- Definitively, only about a quarter of the main flow φ is liquefied; it follows that only this amount must be returned to the plant, so that the flow φP in outlet from the
filter 2 is equal to the amount of liquefied methane gas. - A flow of methane is collected from the
supply network 1 thereof that is such as to reintegrate the liquefied methane and so as to enable supply to the gas motor 10. - From the above description and illustration, it is clear that the motor 10-
compressor 5 group supplies the methane with the power required for circulating in the plant with the aim of cooling and liquefying an amount thereof. - The lowering of the methane to cryogenic levels is entrusted to the main flow φ, first flow φ1 and fifth flow φ5 which are cooled following the crossing of the corresponding first 10, second 20 and third 30 Joule-Thompson valve.
- The main flow φ is also cooled by the first
cryogenic exchanger 250 due to the frigories yielded thereto, more precisely the first circuit C1, from flows φ2, φ4, φ7 passing in circuits C2,C3,C4 of theheat exchanger 250. - The fifth flow φ5 is cooled, upstream of the third Joule-Thompson valve, by the second
cryogenic exchanger 250; the cooling is made possible by the accentuated cooling of the sixth flow φ6 by means of the fourth Joule-Thompsonvalve 50. - This enables the sixth flow to yield frigories, crossing the sixth circuit F2 of the
exchanger 350, to the fifth flow φ5 which involves the fifth circuit F1 of the exchanger. - The steps listed below are actuated by the above-described plant:
- compression of the methane by means of a four-stage (A,B,C,D) reciprocating
compressor 5 so as to reach high pressures (for example up to 250 bar); the recycling of the methane, actuated by flows φ2, φ4, φ7 conveyed to the inlets respectively of the compression stages A, B, C, combines to cool the compressor; - pre-cooling of the main flow φ of the methane to a predetermined temperatures (e.g - 5°C);
- liquefaction of the methane, more precisely by an amount of the main flow φ of about 25%: the sources generating frigories are the four Joule-Thompson valves which exploit the significant range of pressure available (from 250 bar to about 2 bar);
- storage of the liquid methane in the
cryogenic tank 450. - The plant of the invention comprises the above-mentioned
power section 100, the first and secondcryogenic section storage section 400. - The power section comprises the gas motor 10 supplied by the low-pressure
methane gas network 1 and the comburent part φS separated from thefilter 2 by the purified methane. - The first cryogenic section 200 is supplied by the
power section 100 via the main flow and, in turn, supplies the main flow via the recycling flows φ2, φ4, φ7. - The second
cryogenic section 300 is supplied by the first cryogenic section via the main flow φ1 and, in turn, supplies the main flow via the recycling flows φ4, φ7. - The storage section is supplied by the liquid flow φL coming from the
second section 300, and in turn thesecond section 300 is supplied by the methane vapour flow φVM. - Definitively, for its functioning the plant of the invention only uses the methane gas flow φN collected from the
supply network 1. - In fact, the motor 10, of the gas motor type, which provides the power to the plate, is supplied by an amount of flow φF collected by the network that is mixed with the comburent substances φS separated by the methane gas by means of the
filter 2. - At working regime only 25% of the flow circulating in the plant is liquefied and stored; the remaining part is used both for supplying the sources which "generate the cooling" (the four Joule-
Thompson valves - It follows that the plant is made operative only with the methane gas collected from the
network 1. - The above-described and illustrated plant is advantageously provided for obtaining medium liquefied methane gas flows, for example comprised between 5 and 20 tonnes of methane per day.
- It is understood that the above has been described by way of example; any variations of a technical and/or functional nature fall within the protective scope of the invention that is described and illustrated and claimed in the following.
Claims (8)
- A plant for liquefying methane gas, characterised in that it comprises:- - a power section (100) comprising: a molecular filter (2) supplied by a low-pressure methane supply network (1), a compression unit (5) of the methane, connected to the outlet of the filter, destined to supply in outlet a methane main flow (Φ) having a predetermined temperature and pressure, and heat exchangers (11, 12, 13, 14) for cooling the methane crossing the compression unit (5);- - a first cryogenic section (200) connected to the outlet of the power section (100) by which it is supplied from the main flow (Φ) and, in turn, supplying the power section (100) with at least a methane recycling flow (Φ2, Φ4, Φ7), which supplies the compression unit and which cooperates with the heat exchangers for cooling the compression unit;- - a second cryogenic section (300) connected to the first cryogenic section (200) in inlet and in outlet by means of channels (19, 22, 24) crossed by the relative methane flows (Φ1, Φ4, Φ7), the second cryogenic section (300) being destined to liquefy a predetermined amount of the main flow (Φ);- - a storage cryogenic section (400) connected to the second cryogenic section (300) so as to receive therefrom the liquefied methane.
- The plant for liquefying methane gas of the preceding claim, characterised in that the first cryogenic section comprises: a first cryogenic exchanger (250) comprising four circuits (C1, C2, C3, C4), with the first circuit (C1) supplied by the main flow (Φ) which is cooled by the flows (Φ2, Φ4, Φ7) crossing correspondingly the remaining circuits (C2, C3, C4), respectively second, third and fourth, the third and fourth circuits being crossed by respectively the fourth and the seventh relative recycling flows (Φ4, Φ7), coming, via relative pipelines (22, 24), from the second cryogenic section (300) and conveyed, downstream of the relative third and fourth circuits (C3, C4) of said first cryogenic exchanger (250), towards the compression unit (5); a Joule-Thompson valve (10) inserted in the pipeline (17) supplied by the first circuit (C1), destined both to cool the main methane flow (Φ) and to reduce the pressure thereof; a first phase separator (15) supplied by the main flow (Φ) coming from the Joule-Thompson valve (10) and in turn supplying a pipeline (19) crossed by a first flow (Φ1), conveyed to the second cryogenic section (300), and a further pipeline (18) crossed by a second recycling flow (Φ2) directed to the second circuit (C2) of the cryogenic exchanger (250) and successively conveyed to the compression unit (5) of the power section (100).
- The plant for liquefying methane gas of the preceding claim, characterised in that the second cryogenic section (300) comprises: a second Joule-Thompson valve (20) inserted in the pipeline (19) crossed by the first flow (Φ1) coming from the first phase separator (15), and destined to lower the temperature and pressure of the first flow; a second phase separator (16) supplied by the first flow (Φ1) coming from said second valve (20) and supplying in turn two pipelines (21, 22) crossed by relative third and fourth flows (Φ3, Φ4), the fourth flow being conveyed to the third circuit (C3) of the first cryogenic exchanger (250) and successively directed to the compression unit (5) so as to define a corresponding recycling flow; a second cryogenic exchanger (350) comprising two circuits (F1, F2), being respectively a fifth and a sixth circuit, the fifth circuit being crossed by a fifth flow (Φ5) coming from a pipeline (22) supplied by the pipeline (21) crossed by the third flow (Φ3), the fifth flow (Φ5) being equal to a predetermined level of the third flow (Φ3); a fourth Joule-Thompson valve (50) arranged on a pipeline (23) supplied by the pipeline (21) crossed by the third flow (Φ3) and in turn supplying the sixth circuit (F2), the fourth valve being crossed by a sixth flow (Φ6) equal to the remaining level of the third flow (Φ3), the fourth valve (50) being destined to lower the temperature and pressure of the sixth flow (Φ6) for cooling the fifth flow (Φ5) crossing the fifth circuit (F1) of said second cryogenic exchanger (350); a third Joule-Thompson valve (30) located on a pipeline connected to the outlet of the fifth circuit (F1), destined to lower the temperature of the fifth methane flow (Φ5) up to liquefaction thereof, the outlet of the third valve (30) being connected to the storage section (400).
- The plant for liquefying methane gas of claim 2, characterised in that the compression unit comprises: an reciprocating compressor (5) having four compression stages (A, B, C, D) activated by a gas motor (10), the first compression stage (A) being supplied by the methane flow (ΦP) coming from the filter (2) and by the second recycling flow (Φ2) coming from the second circuit (C2) of the first cryogenic exchanger (250), the second compression stage (B) supplied by the methane flow (ΦA) coming from the first compression stage (A) and from the fourth recycling flow (Φ4) coming from the third circuit (C3) of the first cryogenic exchanger (250), the third compression stage (C) being supplied both by the methane flow (ΦB) coming from the second compression stage (B) and from the seventh recycling flow (Φ7) coming from the fourth circuit (C4) of the first cryogenic exchanger (250), and lastly the fourth compression stage (D) being supplied by the flow (ΦC) in outlet from the third compression stage (C) and destined to supply in outlet the main flow (Φ).
- The plant for liquefying methane gas of the preceding claim, characterised in that it further comprises: at least a first heat exchanger (11) for cooling the methane flow (ΦA) in outlet from the first compression stage; at least a second heat exchanger (12) for cooling the methane flow (ΦB) in outlet from the second compression stage (B); at least a third heat exchanger (13) for cooling the methane flow (ΦC) in outlet from the third compression stage (C); at least a fourth heat exchanger (14) for cooling the main methane flow (Φ) in outlet from the fourth compression stage (D).
- The plant for liquefying methane gas of claim 4, characterised in that the gas motor (10) is supplied by a flow (ΦF) branching from the methane supply network (1), upstream of the filter (2), to which is added the flow (ΦS) of the comburent part filtered by the filter (2).
- A plant for liquefying methane gas, characterised in that it comprises: The plant for liquefying methane gas of claim 3, characterised in that the storage section (400) comprises a cryogenic tank (450) for receiving the liquid methane flow (ΦL) coming from the outlet of the third Joule-Thompson valve (30).
- The plant for liquefying methane gas of claim 7, characterised in that it comprises a pipeline (34) connecting a top of the tank (450) with a pipeline, connected to the inlet of the sixth circuit (F2) of the second cryogenic exchanger (350), destined to convey the methane vapours flow (ΦVM) which are released by the liquid methane contained by the tank.
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ITBO20150008 | 2015-01-14 |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
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WO2018141950A1 (en) * | 2017-02-03 | 2018-08-09 | Engie | Biomethane production facility and method for controlling such a facility |
IT201700031616A1 (en) * | 2017-03-22 | 2018-09-22 | S Tra Te G I E Srl | METHANE LIQUEFATION PLANT WITH ITS PROCESS CONTROL SYSTEM |
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GB1054489A (en) * | 1964-07-15 | |||
US6564578B1 (en) * | 2002-01-18 | 2003-05-20 | Bp Corporation North America Inc. | Self-refrigerated LNG process |
WO2009057179A2 (en) * | 2007-10-30 | 2009-05-07 | G.P.T. S.R.L. | Small-scale plant for production of liquified natural gas |
-
2016
- 2016-01-13 EP EP16151024.3A patent/EP3045849A3/en not_active Withdrawn
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2018141950A1 (en) * | 2017-02-03 | 2018-08-09 | Engie | Biomethane production facility and method for controlling such a facility |
FR3062657A1 (en) * | 2017-02-03 | 2018-08-10 | Engie | BIO-METHANE PRODUCTION PLANT AND METHOD FOR CONTROLLING SUCH A PLANT |
IT201700031616A1 (en) * | 2017-03-22 | 2018-09-22 | S Tra Te G I E Srl | METHANE LIQUEFATION PLANT WITH ITS PROCESS CONTROL SYSTEM |
WO2018173082A1 (en) * | 2017-03-22 | 2018-09-27 | S.Tra.Te.G.I.E. S.R.L. | Plant for the liquefation of methane with relative process control system |
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