CN115808053A - Natural gas high pressure liquefaction system - Google Patents
Natural gas high pressure liquefaction system Download PDFInfo
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- CN115808053A CN115808053A CN202211653404.1A CN202211653404A CN115808053A CN 115808053 A CN115808053 A CN 115808053A CN 202211653404 A CN202211653404 A CN 202211653404A CN 115808053 A CN115808053 A CN 115808053A
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- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 title claims abstract description 294
- 239000003345 natural gas Substances 0.000 title claims abstract description 140
- 239000007788 liquid Substances 0.000 claims abstract description 62
- 239000002994 raw material Substances 0.000 claims abstract description 55
- 238000000926 separation method Methods 0.000 claims abstract description 49
- 239000003507 refrigerant Substances 0.000 claims abstract description 41
- 239000007789 gas Substances 0.000 claims abstract description 26
- 239000003949 liquefied natural gas Substances 0.000 claims abstract description 22
- 238000001816 cooling Methods 0.000 claims abstract description 13
- 239000012071 phase Substances 0.000 claims description 10
- 239000007791 liquid phase Substances 0.000 claims description 9
- 238000009833 condensation Methods 0.000 claims description 5
- 230000005494 condensation Effects 0.000 claims description 5
- 238000005265 energy consumption Methods 0.000 abstract description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 8
- NNPPMTNAJDCUHE-UHFFFAOYSA-N isobutane Chemical compound CC(C)C NNPPMTNAJDCUHE-UHFFFAOYSA-N 0.000 description 8
- QWTDNUCVQCZILF-UHFFFAOYSA-N isopentane Chemical compound CCC(C)C QWTDNUCVQCZILF-UHFFFAOYSA-N 0.000 description 8
- 238000000034 method Methods 0.000 description 8
- 238000005057 refrigeration Methods 0.000 description 7
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- OTMSDBZUPAUEDD-UHFFFAOYSA-N Ethane Chemical compound CC OTMSDBZUPAUEDD-UHFFFAOYSA-N 0.000 description 5
- AFABGHUZZDYHJO-UHFFFAOYSA-N dimethyl butane Natural products CCCC(C)C AFABGHUZZDYHJO-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000001282 iso-butane Substances 0.000 description 4
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 4
- 239000001294 propane Substances 0.000 description 4
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000009834 vaporization Methods 0.000 description 2
- 230000008016 vaporization Effects 0.000 description 2
- 238000009835 boiling Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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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
- F25J1/006—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures characterised by the refrigerant fluid used
- F25J1/0097—Others, e.g. F-, Cl-, HF-, HClF-, HCl-hydrocarbons etc. or mixtures thereof
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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
- F25J1/0203—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle
- F25J1/0205—Processes or apparatus for liquefying or solidifying gases or gaseous mixtures requiring the use of refrigeration, e.g. of helium or hydrogen ; Details and kind of the refrigeration system used; Integration with other units or processes; Controlling aspects of the process using a single-component refrigerant [SCR] fluid in a closed vapor compression cycle as a dual level SCR refrigeration cascade
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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
- F25J1/0257—Construction and layout of liquefaction equipments, e.g. valves, machines
- F25J1/0262—Details of the cold heat exchange 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
- F25J2205/00—Processes or apparatus using other separation and/or other processing means
- F25J2205/90—Mixing of components
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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
- F25J2210/04—Mixing or blending of fluids with the feed 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
- F25J2230/00—Processes or apparatus involving steps for increasing the pressure of gaseous process streams
- F25J2230/30—Compression of the feed 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
- F25J2245/00—Processes or apparatus involving steps for recycling of process streams
- F25J2245/02—Recycle of a stream in general, e.g. a by-pass stream
Abstract
The invention discloses a natural gas high-pressure liquefaction system, which comprises: the natural gas raw materials output by the plurality of stages of compressor units sequentially enter the first heat exchanger, the second heat exchanger, the third heat exchanger and the fourth heat exchanger for cooling; the output end of a raw material channel of the fourth heat exchanger is connected with a first conveying pipe with a first throttling valve, the first conveying pipe is communicated with a first gas-liquid separation tank, and a first liquid output pipe with a second throttling valve on the first gas-liquid separation tank is connected to a second gas-liquid separation tank; a second liquid output pipe on the second gas-liquid separation tank outputs a liquefied natural gas product; the natural gas output by the first gas output pipe on the first gas-liquid separation tank sequentially enters the fourth heat exchanger, the third heat exchanger and the first heat exchanger to provide cold energy; the R22 refrigerant output by the second condenser enters the R22 refrigerant channel of the second heat exchanger, and the R23 refrigerant output by the third heat exchanger enters the second condenser. The invention has the advantages that: effectively reduces energy consumption and greatly improves the purity of the liquefied natural gas.
Description
Technical Field
The invention relates to the technical field of natural gas liquefaction.
Background
Liquefied Natural Gas (LNG) is a low-temperature liquid-phase natural gas produced by pretreating gas-phase natural gas produced from a gas field and then cooling the gas through a liquefaction process, and the main component of the liquefied natural gas is methane. The LNG has the main characteristics that the volume of the LNG is only 1/625 of the volume of the gaseous natural gas in the same mass state, and the mass of the LNG is only 45 percent of the mass of water in the same volume state.
The natural gas liquefaction process is a low-temperature process, the cold energy required by the natural gas liquefaction is usually provided by an additional refrigeration cycle, and the provided refrigeration system needs to enable the heat exchanger to reach the minimum cold and heat flow temperature difference, so that higher refrigeration efficiency is obtained.
The traditional natural gas liquefaction can be divided into cascade liquefaction, liquefaction with an expander and mixed refrigerant liquefaction according to a refrigeration mode. Among the drawbacks of cascaded liquefaction are: the number of units is large, the initial investment is large, the connection between equipment and pipelines is complex, the maintenance is unchanged, and the like. Liquefaction with expanders has the disadvantages that: a large heat exchange area is required, which results in a large size of the heat exchanger equipment, low liquefaction rate and high energy consumption. The mixed refrigerant liquefaction has the advantages of simple process flow, small initial investment, capability of enabling components with different boiling points to exert respective refrigeration effects in different temperature regions to liquefy natural gas and the like, and is widely applied to a basic load type natural gas liquefaction device at present, however, the defects that the mixed refrigerant ratio has large influence on the process power consumption, the mixed refrigerant ratio needs to be reconfigured when the working environment is greatly changed and the like still exist in the mixed refrigerant liquefaction process.
Disclosure of Invention
The purpose of the invention is: the high-pressure natural gas liquefaction system can greatly improve the purity of liquefied natural gas products and effectively reduce energy consumption, thereby effectively reducing the cost of the liquefied natural gas products.
In order to achieve the purpose, the invention adopts the technical scheme that: a natural gas high pressure liquefaction system comprising: the system comprises a plurality of stages of compressor units which are sequentially connected in series, wherein each stage of compressor unit comprises a compressor and an air cooling machine, the input end and the output end of each stage of compressor unit which are sequentially connected in series are respectively connected with a natural gas raw material inlet pipe and a natural gas raw material outlet pipe, and the natural gas raw material in each stage of compressor unit firstly enters the stage of compressor and then enters the stage of air cooling machine;
the natural gas raw material output by the natural gas raw material output pipe sequentially enters a first heat exchanger, a second heat exchanger, a third heat exchanger and a fourth heat exchanger for cooling, a raw material channel is arranged in each heat exchanger, and the natural gas raw material flows through the raw material channel of each heat exchanger;
the output end of a raw material channel of the fourth heat exchanger is connected with a first conveying pipe, a first throttling valve is arranged on the first conveying pipe, and the first conveying pipe is communicated with a first gas-liquid separation tank;
a liquid phase outlet and a gas phase outlet on the first gas-liquid separation tank are respectively provided with a first liquid output pipe and a first gas output pipe, the first liquid output pipe is provided with a second throttling valve, and the first liquid output pipe is connected to a second gas-liquid separation tank;
a liquid phase outlet and a gas phase outlet on the second gas-liquid separation tank are respectively provided with a second liquid output pipe and a second gas output pipe, and the second liquid output pipe outputs a liquid natural gas product;
natural gas channels are respectively arranged in the fourth heat exchanger, the third heat exchanger and the first heat exchanger, a first gas output pipe is connected to a natural gas channel inlet of the fourth heat exchanger, a natural gas channel outlet of the fourth heat exchanger is connected to a natural gas channel inlet of the third heat exchanger, and a natural gas channel outlet of the third heat exchanger is connected to a natural gas channel inlet of the first heat exchanger;
the second heat exchanger and the second condenser are used as evaporator components of the R22 refrigerating unit, R22 refrigerant channels are arranged in the second condenser and the second heat exchanger, and R22 refrigerant output by the second condenser enters the R22 refrigerant channel of the second heat exchanger; the second condenser is also provided with an R23 refrigerant channel;
the third heat exchanger is used as an evaporator component of the R23 refrigerating unit, an R23 refrigerant channel is arranged in the third heat exchanger, an outlet of the R23 refrigerant channel is connected to an inlet of the R23 refrigerant channel of the second condenser, and the R23 refrigerant output by the third heat exchanger enters the second condenser to provide cooling capacity.
Further, in the natural gas high-pressure liquefaction system, the compressor unit is provided with four stages, namely a first-stage compressor unit, a second-stage compressor unit, a third-stage compressor unit and a fourth-stage compressor unit; the natural gas raw material inlet pipe is connected with the compressor input end of the first-stage compressor unit, and the air cooler output end of the fourth-stage compressor unit is connected with the natural gas raw material output pipe.
Further, in the above natural gas high pressure liquefaction system, the second gas output pipe is connected to a natural gas compressor, an output end of the natural gas compressor is connected to a natural gas input end of the first condenser, a natural gas output end of the first condenser is connected to a condenser natural gas output pipe, and the condenser natural gas output pipe is connected to the mixer; first conveyer pipe be connected to the blender earlier, first conveyer pipe passes through blender and first gas-liquid separation jar intercommunication, the natural gas that first conveyer pipe carried in the blender mixes with the natural gas of condenser natural gas output tube input, the blender output is connected to first gas-liquid separation jar.
Further, in the natural gas high-pressure liquefaction system, the first heat exchanger, the second heat exchanger, the third heat exchanger and the fourth heat exchanger all adopt printed circuit board heat exchangers.
Further, in the natural gas high-pressure liquefaction system, the temperature of the natural gas raw material output by the output ends of the compressor units connected in series in sequence is not higher than 50 ℃, and the pressure is 2.4 × 10 4 kPa。
Further, in the natural gas high-pressure liquefaction system, the temperature of the natural gas raw material output by the fourth heat exchanger is-75.95 ℃.
The invention has the advantages that: 1. the natural gas raw material is pressurized by adopting the multistage compressor group, and then the pressurized natural gas raw material sequentially enters the first heat exchanger, the second heat exchanger, the third heat exchanger and the fourth heat exchanger to be cooled step by step, wherein the second heat exchanger and the second condenser are used as evaporator components of the R22 refrigerating unit, and R23 refrigerant output by the third heat exchanger enters the second condenser to provide cold energy. 2. And the first gas-liquid separation tank and the second gas-liquid separation tank are adopted to carry out gas-liquid separation twice, so that the purity of the liquefied natural gas product is greatly improved. 3. The vaporized natural gas generated after the second gas-liquid separation is subjected to pressurization condensation and then mixed with the natural gas output by the fourth heat exchanger, and then enters the first vaporization separation tank, so that the gas-liquid separation effect is greatly improved, and the purity of the liquefied natural gas product is effectively improved. By adopting the high-pressure liquefying system, the purity of the liquefied natural gas can reach more than 95 percent.
Drawings
Fig. 1 is a schematic structural diagram of a natural gas high-pressure liquefaction system according to the invention.
Detailed Description
The invention is described in further detail below with reference to the figures and preferred embodiments.
A natural gas high pressure liquefaction system as shown in fig. 1 comprises: the compressor set of a plurality of grades of compressor unit of establishing ties in proper order, each grade compressor unit all include compressor and air cooling machine, and the input and the output of the compressor set of establishing ties in proper order are connected with natural gas raw materials intake pipe 20 and natural gas raw materials output tube 5 respectively. And the natural gas raw material in each stage of compressor unit firstly enters the stage of compressor and then enters the stage of air cooler. In this embodiment, in order to effectively boost the pressure, the compressor set is provided with four stages, which are a first-stage compressor set 1, a second-stage compressor set 2, a third-stage compressor set 3, and a fourth-stage compressor set 4. Wherein, the first compressor unit 1 comprises a first compressor 11 and a first air cooler 12, the second compressor unit 2 comprises a second compressor 21 and a second air cooler 22, the third compressor unit 3 comprises a third compressor 31 and a third air cooler 32, and the four-stage compression unitThe unit 4 includes a fourth compressor 41 and a fourth air cooler 42. The natural gas raw material inlet pipe 20 is connected with the input end of the first compressor 11 in the first-stage compressor unit 1, and the output end of the fourth air cooler 42 of the fourth-stage compressor unit 4 is connected with the natural gas raw material output pipe 5. The natural gas raw material output from the output ends of the compressor units connected in series in sequence has a temperature of not higher than 50 ℃ and a pressure of 2.4 multiplied by 10 4 kPa。
The natural gas raw material output by the natural gas raw material output pipe 5 sequentially enters a first heat exchanger 6, a second heat exchanger 7, a third heat exchanger 8 and a fourth heat exchanger 9 for cooling, a raw material channel is arranged in each heat exchanger, and the natural gas raw material flows through the raw material channel of each heat exchanger. Specifically, the first heat exchanger 6 is provided with a first raw material passage 62, the second heat exchanger 7 is provided with a second raw material passage 72, the third heat exchanger 8 is provided with a third raw material passage 82, and the fourth heat exchanger 9 is provided with a fourth raw material passage 92. In order to improve the heat exchange efficiency, the first heat exchanger 6, the second heat exchanger 7, the third heat exchanger 8 and the fourth heat exchanger 9 all adopt printed circuit board type heat exchangers in the embodiment.
The output end of the raw material channel of the fourth heat exchanger 9 is connected with the first conveying pipe 10, and the temperature of the natural gas raw material output by the fourth heat exchanger 9 is-75.95 ℃.
A first throttling valve 101 is arranged on the first conveying pipe 10, and the first conveying pipe 10 is communicated with a first gas-liquid separation tank 15; the liquid phase outlet and the gas phase outlet of the first gas-liquid separation tank 15 are respectively provided with a first liquid output pipe 16 and a first gas output pipe 151, the first liquid output pipe 16 is provided with a second throttle valve 161, and the first liquid output pipe 16 is connected to the second gas-liquid separation tank 17.
The liquid phase outlet and the gas phase outlet of the second gas-liquid separation tank 17 are respectively provided with a second liquid output pipe 171 and a second gas output pipe 172, and the second liquid output pipe 171 outputs the liquefied natural gas product.
The fourth heat exchanger 9, the third heat exchanger 8 and the first heat exchanger 6 are respectively provided with a natural gas channel. Specifically, a fourth natural gas passage 91 is arranged in the fourth heat exchanger 9, a third natural gas passage 81 is arranged in the third heat exchanger 8, and a first natural gas passage 61 is arranged in the first heat exchanger 6. The first gas output pipe 151 is connected to the inlet of the natural gas channel of the fourth heat exchanger 9, the outlet of the natural gas channel of the fourth heat exchanger 9 is connected to the inlet of the natural gas channel of the third heat exchanger 8, and the outlet of the natural gas channel of the third heat exchanger 8 is connected to the inlet of the natural gas channel of the first heat exchanger 6. The natural gas vaporized in the first gas-liquid separation tank 15 enters the natural gas channel in the fourth heat exchanger 9, the third heat exchanger 8 and the first heat exchanger 6, so as to provide cold for the fourth heat exchanger 9, the third heat exchanger 8 and the first heat exchanger 6, and the purpose of the cold is as follows: the energy consumption is reduced, and the cost is reduced.
The second heat exchanger 7 and the second condenser 30 are used as evaporator components of the R22 refrigeration unit, R22 refrigerant channels are arranged in both the second condenser 30 and the second heat exchanger 7, and R22 refrigerant output by the second condenser 30 enters the R22 refrigerant channels of the second heat exchanger 7. The second condenser 30 is also provided therein with an R23 refrigerant passage. Specifically, the second condenser R22 refrigerant passage 301, the second condenser R23 refrigerant passage 302, and the second heat exchanger R22 refrigerant passage 73 are provided in the second condenser 30, and the second heat exchanger 7, respectively.
The third heat exchanger 8 is used as an evaporator assembly of the R23 refrigeration unit, a third heat exchanger R23 refrigerant passage 83 is arranged in the third heat exchanger 8, an outlet of the third heat exchanger R23 refrigerant passage 83 is connected to an inlet of a second condenser R23 refrigerant passage 302 of the second condenser, and the R23 refrigerant output by the third heat exchanger 8 enters the second condenser 30 to provide cooling capacity.
In this embodiment, the second gas output pipe 172 is connected to the natural gas compressor 18, the output end of the natural gas compressor 18 is connected to the natural gas input end of the first condenser 14, the natural gas output end of the first condenser 14 is connected to the condenser natural gas output pipe 141, and the condenser natural gas output pipe 141 is connected to the mixer 13. The first delivery pipe 10 is connected to a mixer 13, and the first delivery pipe 10 is communicated with a first gas-liquid separation tank 15 through the mixer 13. The natural gas delivered by the first delivery pipe 10 in the mixer 13 is mixed with the natural gas input by the natural gas output pipe 141 of the condenser, and the output end of the mixer 13 is connected to the first gas-liquid separation tank 15. First choke valve 101, the liquefaction rate is lower after the throttling decompression of high-pressure low temperature natural gas, through with second gas output tube 172 slightly pressure boost precooling after, then through mixer 13 with the temperature, the low temperature natural gas that the pressure has a small amount of differences mixes, realize abundant heat and mass transfer homogeneous phase process in the mixer, it is the even low temperature natural gas of temperature, composition to have realized the export of mixer 13, and set up mixer 13 and can realize the flow that gets into first gas-liquid separation tank 15 and do not have the pulse fluctuation, play the effect of stabilizing flow.
The specific liquefaction process is given below: the molar composition of the natural gas feed was 87.37% methane +0.93% ethane +0.28% propane +0.28% isobutane +0.07% n-butane +0.07% isopentane +11% nitrogen at 31.16 ℃, pressure 530.0kPa, molar flow 105.7 kmol/h.
The natural gas raw material delivered by the natural gas raw material inlet pipe 20 sequentially enters a first compressor 11 and a first air cooler 12 in the first-stage compressor unit 1, a second compressor 21 and a second air cooler 22 in the second-stage compressor unit 2, a third compressor 31 and a third air cooler 32 in the third-stage compressor unit 3, and a fourth compressor 41 and a fourth air cooler 42 in the fourth-stage compressor unit 4. The natural gas feed is pressurized in each stage of the compressor and then cooled in each stage of the cooler. The natural gas raw material output by the natural gas raw material output pipe 5 has the temperature of 50 ℃ and the pressure of 2.4 multiplied by 10 4 kPa, molar flow rate 105.7 kmol/h, the composition of which was unchanged.
And the raw material natural gas in the natural gas raw material output pipe 5 sequentially enters a first heat exchanger 6, a second heat exchanger 7, a third heat exchanger 8 and a fourth heat exchanger 9 for cooling. The natural gas feed to the first transfer line 10 has a temperature of-75.95 deg.C and a pressure of 2.39X 10 4 kPa, molar flow rate 105.7 kmol/h, the composition of which was unchanged.
The condensation temperature of the R22 high-temperature stage refrigerating unit is 44.55 ℃, the evaporation temperature is-10.35 ℃, the flow of the high-pressure stage refrigerant is 2736 kg/h, and the flow of the low-pressure stage refrigerant is 2321.61 kg/h;
the condensation temperature of the R23 low-temperature stage refrigerating unit is-3.28 ℃, the evaporation temperature is-48.99 ℃, the flow rate of the high-pressure stage refrigerant is 1262.88 kg/h, and the flow rate of the low-pressure stage refrigerant is 1080.50 kg/h.
After passing through the first throttle valve 101, the temperature of the natural gas raw material output by the first delivery pipe 10 and entering the mixer 13 is-137.5 ℃, and the pressure is 600kPa. The natural gas delivered by the condenser natural gas output pipe 141 had a temperature of-136.5 ℃ and a pressure of 600kPa. The two streams of natural gas are mixed in a mixer 13 and then passed to a first gas-liquid separation tank 15. The natural gas output from mixer 13 was at-137.4 deg.C and a pressure of 600kPa, at which time the natural gas had a molar composition of 87.63% methane +0.87% ethane +0.26% propane +0.26% isobutane +0.07% n-butane +0.07% isopentane +10.85% nitrogen.
After the first gas-liquid separation tank 15 is separated, the natural gas output from the gas phase outlet of the first gas-liquid separation tank 15 flows into the fourth heat exchanger 9, the third heat exchanger 8 and the first heat exchanger 6 in sequence, and the gas molar composition of the natural gas discharged from the first heat exchanger 6 is 83.07% of methane +0.02% of ethane +16.91% of nitrogen.
The liquefied natural gas outputted from the liquid phase outlet of the first gas-liquid separation tank 15 flows into the second gas-liquid separation tank 17 through the second throttle valve 161. The temperature of the natural gas output after passing through the second throttle valve 161 is-160.1 ℃, the pressure is 120 kPa, the molar flow is 45.45 kmol/h, and the molar components are 94.46% of methane, 2.13% of ethane, 0.65% of propane, 0.65% of isobutane, 0.16% of n-butane, 0.16% of isopentane and 1.78% of nitrogen.
The natural gas volatile gas separated from the gas phase outlet of the second gas-liquid separation tank 17 is pressurized by the natural gas compressor 18 and condensed by the first condenser 14, and then enters the mixer 13 at a temperature of-136.5 ℃, a pressure of 600kPa, and molar components of 91.25% methane and 8.75% nitrogen.
The LNG temperature after separation through the liquid phase outlet of the second gas-liquid separation tank 17 was-160.1 ℃, the pressure was 120 kPa, and the molar components were 95.11% methane +2.57% ethane +0.78% propane +0.78% isobutane +0.2% n-butane +0.2% isopentane +0.36% nitrogen.
It can be seen that after twice separation in the first gas-liquid separation tank 15 and the second gas-liquid separation tank 17, the purity of the finished liquefied natural gas output from the second gas-liquid separation tank 17 is greatly improved.
The invention has the advantages that: 1. the natural gas raw material is pressurized by adopting the multistage compressor group, and then the pressurized natural gas raw material sequentially enters the first heat exchanger, the second heat exchanger, the third heat exchanger and the fourth heat exchanger to be cooled step by step, wherein the second heat exchanger and the second condenser are used as evaporator components of the R22 refrigerating unit, and R23 refrigerant output by the third heat exchanger enters the second condenser to provide cold energy. 2. And the first gas-liquid separation tank and the second gas-liquid separation tank are adopted to carry out gas-liquid separation twice, so that the purity of the liquefied natural gas product is greatly improved. 3. The vaporized natural gas generated after the second gas-liquid separation is subjected to pressurization condensation and then mixed with the natural gas output by the fourth heat exchanger in the mixer, and then enters the first vaporization separation tank, so that the gas-liquid separation effect is further greatly improved, and the purity of the liquefied natural gas product is effectively improved. By adopting the high-pressure liquefaction system, the purity of the liquefied natural gas can reach more than 95%.
Claims (6)
1. A natural gas high pressure liquefaction system comprising: the system comprises a plurality of stages of compressor units which are sequentially connected in series, wherein each stage of compressor unit comprises a compressor and an air cooling machine, the input end and the output end of each stage of compressor unit which are sequentially connected in series are respectively connected with a natural gas raw material inlet pipe and a natural gas raw material outlet pipe, and the natural gas raw material in each stage of compressor unit firstly enters the stage of compressor and then enters the stage of air cooling machine;
the natural gas raw material output by the natural gas raw material output pipe sequentially enters a first heat exchanger, a second heat exchanger, a third heat exchanger and a fourth heat exchanger for condensation, a raw material channel is arranged in each heat exchanger, and the natural gas raw material flows through the raw material channel of each heat exchanger;
the output end of a raw material channel of the fourth heat exchanger is connected with a first conveying pipe, a first throttle valve is arranged on the first conveying pipe, and the first conveying pipe is communicated with a first gas-liquid separation tank;
a liquid phase outlet and a gas phase outlet on the first gas-liquid separation tank are respectively provided with a first liquid output pipe and a first gas output pipe, the first liquid output pipe is provided with a second throttling valve, and the first liquid output pipe is connected to a second gas-liquid separation tank;
a liquid phase outlet and a gas phase outlet on the second gas-liquid separation tank are respectively provided with a second liquid output pipe and a second gas output pipe, and the second liquid output pipe outputs a liquefied natural gas product;
natural gas channels are respectively arranged in the fourth heat exchanger, the third heat exchanger and the first heat exchanger, a first gas output pipe is connected to a natural gas channel inlet of the fourth heat exchanger, a natural gas channel outlet of the fourth heat exchanger is connected to a natural gas channel inlet of the third heat exchanger, and a natural gas channel outlet of the third heat exchanger is connected to a natural gas channel inlet of the first heat exchanger;
the second heat exchanger and the second condenser are used as evaporator components of the R22 refrigerating unit, R22 refrigerant channels are arranged in the second condenser and the second heat exchanger, and R22 refrigerant output by the second condenser enters the R22 refrigerant channels of the second heat exchanger; the second condenser is also provided with an R23 refrigerant channel;
the third heat exchanger is used as an evaporator component of the R23 refrigerating unit, an R23 refrigerant channel is arranged in the third heat exchanger, an outlet of the R23 refrigerant channel is connected to an inlet of the R23 refrigerant channel of the second condenser, and the R23 refrigerant output by the third heat exchanger enters the second condenser to provide cooling capacity.
2. The high pressure natural gas liquefaction system of claim 1, wherein: the compressor group is provided with four stages, namely a first-stage compressor unit, a second-stage compressor unit, a third-stage compressor unit and a fourth-stage compressor unit; the natural gas raw material inlet pipe is connected with the compressor input end of the first-stage compressor unit, and the air cooler output end of the fourth-stage compressor unit is connected with the natural gas raw material output pipe.
3. The high pressure natural gas liquefaction system of claim 1, wherein: the second gas output pipe is connected to the natural gas compressor, the output end of the natural gas compressor is connected to the natural gas input end of the first condenser, the natural gas output end of the first condenser is connected with a natural gas output pipe of the condenser, and the natural gas output pipe of the condenser is connected to the mixer; first conveyer pipe be connected to the blender earlier, first conveyer pipe passes through blender and first gas-liquid separation jar intercommunication, the natural gas that first conveyer pipe carried in the blender mixes with the natural gas of condenser natural gas output tube input, the blender output is connected to first gas-liquid separation jar.
4. The high pressure natural gas liquefaction system of claim 1, wherein: the first heat exchanger, the second heat exchanger, the third heat exchanger and the fourth heat exchanger are all printed circuit board type heat exchangers.
5. The natural gas high pressure liquefaction system of claim 1, wherein: the natural gas raw material output from the output ends of the compressor units connected in series in sequence has a temperature of not higher than 50 ℃ and a pressure of 2.4 multiplied by 10 4 kPa。
6. The high pressure natural gas liquefaction system of claim 1, wherein: the temperature of the natural gas feed output by the fourth heat exchanger was-75.95 ℃.
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| CN202211653404.1A CN115808053A (en) | 2022-12-22 | 2022-12-22 | Natural gas high pressure liquefaction system |
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| CN202211653404.1A CN115808053A (en) | 2022-12-22 | 2022-12-22 | Natural gas high pressure liquefaction system |
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