CN110747026A - System and method for preparing LNG (liquefied Natural gas) from oxygen-containing coal bed gas based on thermoacoustic technology - Google Patents
System and method for preparing LNG (liquefied Natural gas) from oxygen-containing coal bed gas based on thermoacoustic technology Download PDFInfo
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- 239000007789 gas Substances 0.000 title claims abstract description 123
- 239000003245 coal Substances 0.000 title claims abstract description 109
- 239000003949 liquefied natural gas Substances 0.000 title claims abstract description 101
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 title claims abstract description 34
- 239000001301 oxygen Substances 0.000 title claims abstract description 34
- 229910052760 oxygen Inorganic materials 0.000 title claims abstract description 34
- 238000005516 engineering process Methods 0.000 title claims abstract description 27
- 238000000034 method Methods 0.000 title claims abstract description 24
- 238000001179 sorption measurement Methods 0.000 claims abstract description 57
- 238000003860 storage Methods 0.000 claims abstract description 37
- 238000000746 purification Methods 0.000 claims abstract description 26
- 230000000694 effects Effects 0.000 claims abstract description 7
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 98
- 239000003345 natural gas Substances 0.000 claims description 28
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 14
- 230000000087 stabilizing effect Effects 0.000 claims description 13
- 238000003795 desorption Methods 0.000 claims description 10
- 230000001965 increasing effect Effects 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 8
- 238000002485 combustion reaction Methods 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- 239000002253 acid Substances 0.000 claims description 6
- 230000002708 enhancing effect Effects 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 4
- 238000005265 energy consumption Methods 0.000 abstract description 6
- 239000003507 refrigerant Substances 0.000 abstract description 5
- 230000008929 regeneration Effects 0.000 abstract description 5
- 238000011069 regeneration method Methods 0.000 abstract description 5
- 238000011084 recovery Methods 0.000 abstract description 4
- 239000003344 environmental pollutant Substances 0.000 abstract description 2
- 231100000719 pollutant Toxicity 0.000 abstract description 2
- 238000005057 refrigeration Methods 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 5
- 230000018109 developmental process Effects 0.000 description 3
- 238000010248 power generation Methods 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000003595 mist Substances 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/101—Removal of contaminants
- C10L3/102—Removal of contaminants of acid contaminants
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/101—Removal of contaminants
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/101—Removal of contaminants
- C10L3/106—Removal of contaminants of water
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B23/00—Machines, plants or systems, with a single mode of operation not covered by groups F25B1/00 - F25B21/00, e.g. using selective radiation effect
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
- F25B9/14—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle
- F25B9/145—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the cycle used, e.g. Stirling cycle pulse-tube cycle
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Abstract
The invention discloses a system and a method for preparing liquefied natural gas from oxygen-containing coal bed gas based on a thermoacoustic technology. The system comprises a pressurization unit, a purification unit, a multi-stage pressure swing adsorption unit, a low-temperature liquefaction unit and an LNG storage and transportation unit which are connected in sequence; the system also comprises a thermoacoustic engine unit connected with the low-temperature liquefaction unit, and the thermoacoustic engine unit utilizes thermoacoustic technology to drive the pulse tube refrigerator to work by burning part of the coal bed gas so as to provide cold energy required by the low-temperature liquefaction unit. The liquefaction part does not need external power supply at all, improves the recovery efficiency of the coal bed gas, overcomes the factors of difficult proportioning of the mixed refrigerant, poor adaptability of variable load working conditions and the like in the traditional liquefaction process, and is particularly suitable for the working conditions of less or no power supply of dispersive coal mines or oil and gas wells. In addition, LNG can be optionally introduced into the multistage pressure swing adsorption unit to enhance the adsorption effect; the evaporated gas generated by the LNG storage and transportation unit is subjected to heat exchange and then is used for regeneration of the adsorption purifier, so that the energy consumption of the system is further reduced, and the pollutant emission is reduced.
Description
Technical Field
The invention relates to the technical field of LNG preparation from oxygen-containing coal bed gas, in particular to a system and a method for preparing LNG from oxygen-containing coal bed gas based on a thermoacoustic technology.
Background
The reasonable development and utilization of the coal bed gas not only can supplement natural gas resources to a certain extent and relieve the shortage of oil gas resources, but also can reduce the emission of greenhouse gases and improve the production safety of coal mines, and has important economic and social benefits.
The coal bed gas can be divided into medium-high concentration coal bed gas (the content of methane is more than 30%), low concentration coal bed gas (the content of methane is 10% -30%), very low concentration coal bed gas (the content of methane is 1% -10%) and wind exhaust gas (the content of methane is less than 1%), which respectively account for 6%, 11% (including low concentration and very low concentration) and 83% of the total amount of coal bed gas discharged in China. At present, aiming at the conditions that the utilization technology of medium-high concentration coal bed gas is mature, the content of methane in extremely-low concentration coal bed gas and wind-exhausted gas is low, the utilization technology is difficult and is basically emptied, most of low-concentration coal bed gas is used for on-site power generation or water mist transmission, and part of low-concentration coal bed gas is concentrated for civil use, but the power generation efficiency is only 30-40%, and serious waste exists when power generation is not needed, in addition, the water mist transmission technology is high in cost and high in risk, and the utilization efficiency of the coal bed gas in China is severely limited. Therefore, the characteristics of 'remote, dispersed and small single-well yield' of coal mines in China are combined, low-concentration coal bed gas is liquefied to prepare LNG after being purified, and then the LNG is transported and utilized, so that the recovery efficiency of the coal bed gas is improved.
In order to solve the problem of preparing LNG from oxygen-containing coal bed gas, CN101922850A and CN101929788A respectively disclose a method for preparing liquefied natural gas from oxygen-containing coal bed gas and a device for preparing liquefied natural gas from oxygen-containing coal bed gas, and the refrigeration processes of the two adopt mixed refrigerant refrigeration combined with throttling refrigeration. CN103146449A discloses a process for preparing LNG by pressure swing adsorption and cryogenic liquefaction, which comprises the steps of firstly increasing the methane content in oxygen-containing coal bed gas from 10-28% to 35-45% by the pressure swing adsorption process, then separating methane by the cryogenic liquefaction technology to prepare LNG, and providing the cold energy required by liquefaction by refrigeration cycle.
In the method for preparing LNG from oxygen-containing coal bed gas, the cold energy required by liquefaction is provided by an external refrigeration cycle, the main liquefaction processes comprise a mixed refrigerant liquefaction process and a liquefaction process with an expander, the heat exchanger has high manufacturing difficulty and difficult reasonable proportioning of the mixed refrigerant, and the expander has high equipment input and energy consumption, both of which need external power supply, and is inconvenient to use in remote areas without power supply. In addition, the traditional liquefaction process mainly treats medium-high concentration coal bed gas, and for low-concentration coal bed gas, if a cryogenic rectification mode is directly adopted, energy consumption is huge because of the existence of a large amount of nitrogen.
Disclosure of Invention
The invention aims to solve the problems of complex flow, huge energy consumption, difficult mixture ratio of mixed refrigerants, poor adaptability to variable-load working conditions, requirement of external power supply and the like in the conventional oxygen-containing coal bed gas liquefaction process, and provides a system and a method for preparing LNG from oxygen-containing coal bed gas based on a thermoacoustic technology. The coal bed gas is extracted from a mine and then enters an LNG storage tank after being subjected to pressurization, purification, multistage pressure swing adsorption and low-temperature liquefaction in sequence; a thermoacoustic engine unit is also adopted, and the thermoacoustic technology is utilized, and the combustion part of the coal bed gas drives the arterial tube refrigerator to work so as to provide the cold energy required by the low-temperature liquefaction unit; in addition, the evaporated gas generated in the LNG storage tank exchanges heat with various media in different temperature ranges, the low-temperature cold energy is fully recycled and used for regeneration of the adsorption purifier, and finally, the part which cannot be reused is sent to the thermoacoustic engine unit for combustion; and (3) optionally conveying part of LNG of the LNG storage and transportation unit to the multistage pressure swing adsorption unit, and enhancing the adsorption effect by using the low-temperature cold energy of the LNG storage and transportation unit (the introduction amount of the LNG can be determined according to actual conditions). Through the measures, the recovery efficiency of the coal bed gas is improved, the power consumption of a natural gas liquefaction part is saved, the energy consumption of a system is reduced, and the pollutant emission is reduced.
The invention provides the following technical scheme:
a system for preparing LNG from oxygen-containing coal bed gas based on thermoacoustic technology comprises a pressurization unit, a purification unit, a multi-stage pressure swing adsorption unit, a low-temperature liquefaction unit and an LNG storage and transportation unit which are sequentially connected; the thermoacoustic engine unit is connected with the low-temperature liquefaction unit;
the pressurizing unit is used for pressurizing coal bed gas and comprises a pressure stabilizing tank, a supercharger and a cooler which are sequentially connected, wherein the inlet of the pressure stabilizing tank is directly communicated with the outlet of a coal bed gas well field;
the purification unit is used for removing acid gas, moisture and impurities in the coal bed gas to obtain normal-temperature high-pressure purified coal bed gas only containing nitrogen, oxygen and methane, namely oxygen-containing coal bed gas;
the multistage pressure swing adsorption unit comprises a plurality of adsorption towers, is used for adsorption and desorption, and improves the concentration of methane in the oxygen-containing coal bed gas to obtain gaseous natural gas;
the low-temperature liquefaction unit comprises a high-efficiency heat exchanger and a pulse tube refrigerator which are sequentially connected and is used for liquefying the gaseous natural gas;
the LNG storage and transportation unit comprises an LNG storage tank and an LNG tank car;
the inlet of the thermoacoustic engine unit is directly communicated with the outlet of the coal bed gas well field, the outlet of the thermoacoustic engine unit is directly communicated with the pulse tube refrigerator in the low-temperature liquefaction unit, and the thermoacoustic technology is utilized to drive the arterial tube refrigerator to work through part of the coal bed gas to provide the cold energy required by the low-temperature liquefaction unit.
The pressurizing unit, the purifying unit, the multistage pressure swing adsorption unit, the low-temperature liquefaction unit, the thermoacoustic engine unit and the LNG storage and transportation unit are skid-mounted structures which are convenient to move.
The purification unit comprises at least one set of adsorption purifiers.
The multistage pressure swing adsorption unit can adopt an automatic control technology to realize automatic adsorption and desorption processes.
A method for producing LNG using the system according to the above, comprising the steps of:
1) the coal bed gas extracted from the mine firstly enters a pressure stabilizing tank of a pressurizing unit, then is pressurized by a supercharger through the pressure stabilizing tank, then enters a cooler for cooling, and enters a purifying unit for purification after being cooled, so that the acidic gas, water and other impurities in the coal bed gas are removed, and the coal bed gas becomes the normal-temperature high-pressure purified coal bed gas only containing nitrogen, oxygen and methane;
2) the purified oxygen-containing coal bed gas enters a multi-stage pressure swing adsorption unit, the methane content is increased to the natural gas concentration through continuous and alternate adsorption and desorption, and the concentrated coal bed gas is desorbed to obtain gaseous natural gas;
3) the method comprises the following steps that gaseous natural gas enters a low-temperature liquefaction unit, is cooled in the unit to become liquefied natural gas, then enters an LNG storage tank of an LNG storage and transportation unit, and then is transported out by an LNG tanker;
4) part of the coal bed gas extracted from a mine is directly introduced into a thermoacoustic engine unit, the entered coal bed gas is combusted, and a pulse tube refrigerator is driven to work by using thermoacoustic technology to provide cold energy required by liquefied gaseous natural gas in a low-temperature liquefaction unit;
5) BOG generated by the LNG storage and transportation unit is conveyed to the low-temperature liquefaction unit through a pipeline, and the BOG and the incoming gaseous natural gas exchange heat in the low-temperature liquefaction unit to recover cold energy; BOG with increased temperature after heat exchange enters a purification unit, the BOG in the purification unit is pressurized and then used as regeneration gas of an adsorption purifier, and then enters a thermoacoustic engine unit for combustion to drive a pulse tube refrigerator to work;
6) and optionally conveying part of LNG of the LNG storage and transportation unit to a multi-stage pressure swing adsorption unit through a pipeline, enhancing the adsorption effect by using the low-temperature cold energy of the LNG (the introduction amount of the LNG can be determined according to the actual condition), then, introducing the LNG into a high-efficiency heat exchanger of a low-temperature liquefaction unit to exchange heat with the concentrated coal bed gas, and finally, conveying the LNG to a cold end heat exchanger of a pulse tube refrigerator to be liquefied into finished LNG.
The invention has the beneficial effects that: by utilizing the thermoacoustic technology, the refrigeration machine of the arterial tube is driven by part of the coal bed gas to work, the cold quantity required by the liquefied gaseous natural gas in the low-temperature liquefaction unit is provided, and compared with the traditional liquefaction mode, the system not only improves the recovery efficiency of the coal bed gas, but also does not need external power supply, and is particularly suitable for working conditions of a dispersive coal mine or a gas well with less or no power supply. The energy and the substances of the boil-off gas generated by the LNG storage tank are recycled, so that the energy consumption of the system is reduced, and the exhaust emission is reduced; and introducing part of the finished LNG into a multi-stage pressure swing adsorption unit, and enhancing the adsorption effect by using the low-temperature cold energy of the finished LNG. In addition, each unit of the system adopts a movable skid-mounted structure, so that the development of 'small reserve, dispersed and remote' coal bed gas resources is facilitated, and the exploitation range of the coal bed gas is expanded.
Drawings
FIG. 1 is a block diagram of a system for preparing LNG from oxygen-containing coal bed gas based on thermoacoustic technology, which is disclosed by the invention:
FIG. 2 is a schematic structural diagram of an oxygen-containing coal bed methane LNG production system based on thermoacoustic technology according to the present invention;
the system comprises a pressure stabilizing tank 1, a supercharger 2, a cooler 3, a purification unit 4, a multistage pressure swing adsorption unit 5, a high-efficiency heat exchanger 6, a thermoacoustic engine unit 7, a pulse tube refrigerator 8, an LNG storage tank 9, an LNG tank wagon 10, a first pipeline 11, a second pipeline 12, a third pipeline 13, a fourth pipeline 14, a fifth pipeline 15, a sixth pipeline 16, a seventh pipeline 17, an eighth pipeline 18, a ninth pipeline 19, a tenth pipeline 20, an eleventh pipeline 21, a twelfth pipeline 22, a thirteenth pipeline 23, a fourteenth pipeline 24, a fifteenth pipeline 25 and a sixteenth pipeline 26.
Detailed Description
The invention is further elucidated with reference to the drawing.
As shown in fig. 1 and 2, the system for preparing LNG from oxygen-containing coal bed gas based on thermoacoustic technology provided by the invention comprises a pressurization unit, a purification unit 4, a multi-stage pressure swing adsorption unit 5, a low-temperature liquefaction unit, and an LNG storage and transportation unit, which are connected in sequence; the low-temperature liquefaction unit is connected with the heat-sound engine unit.
The pressurization unit is used for pressurizing coal bed gas and comprises a pressure stabilizing tank 1, a supercharger 2 and a cooler 3 which are sequentially connected, wherein the inlet of the pressure stabilizing tank 1 is directly communicated with the outlet of a coal bed gas well site;
the purification unit 4 is used for removing acid gas, water and impurities in the coal bed gas to obtain normal-temperature high-pressure purified coal bed gas only containing nitrogen, oxygen and methane, namely oxygen-containing coal bed gas;
the multistage pressure swing adsorption unit 5 comprises a plurality of adsorption towers for adsorption and desorption, and the concentration of methane in the oxygen-containing coal bed gas is increased to obtain gaseous natural gas;
the low-temperature liquefaction unit comprises a high-efficiency heat exchanger 6 and a pulse tube refrigerator 8 which are connected in sequence and used for liquefying the gaseous natural gas;
the LNG storage and transportation unit comprises an LNG storage tank 9 and an LNG tank wagon 10.
The inlet of the thermoacoustic engine unit is directly communicated with the outlet of the coal bed gas well field, the outlet of the thermoacoustic engine unit is directly communicated with the pulse tube refrigerator 8 in the low-temperature liquefaction unit, and the combustion part of the coal bed gas drives the arterial tube refrigerator 8 to work by utilizing thermoacoustic technology, so that the cold quantity required by the low-temperature liquefaction unit is provided.
The pressurizing unit, the purifying unit, the multistage pressure swing adsorption unit, the low-temperature liquefaction unit, the thermoacoustic engine unit and the LNG storage and transportation unit are skid-mounted structures which are convenient to move.
The purification unit 4 comprises at least one set of adsorption purifiers.
The multistage pressure swing adsorption unit 5 can adopt an automatic control technology to realize automatic adsorption and desorption processes.
The invention provides a method for preparing LNG from oxygen-containing coal bed gas based on a thermoacoustic technology, which comprises the following steps:
1) coal bed gas extracted from a mine firstly enters a pressure stabilizing tank 1 of a pressurizing unit, then is pressurized by a supercharger 2 through the pressure stabilizing tank 1, then enters a cooler 3 for cooling, and enters a purifying unit 4 for purification after being cooled, so that acid gas, water and other impurities in the coal bed gas are removed, and the coal bed gas becomes normal-temperature high-pressure purified coal bed gas only containing nitrogen, oxygen and methane, namely oxygen-containing coal bed gas;
2) the purified oxygen-containing coal bed gas enters a multi-stage pressure swing adsorption unit 5, the methane content is increased to the natural gas concentration through continuous and alternate adsorption and desorption, and the concentrated coal bed gas is desorbed to obtain gaseous natural gas;
3) the method comprises the following steps that gaseous natural gas enters a low-temperature liquefaction unit, is cooled in the low-temperature liquefaction unit to become liquefied natural gas, then enters an LNG storage tank 9 of an LNG storage and transportation unit, and then is transported out by an LNG tanker 10;
4) part of the coal bed gas extracted from a mine is directly introduced into a thermoacoustic engine unit 7, the entered coal bed gas is combusted, and a pulse tube refrigerator 8 is driven to work by using thermoacoustic technology to provide cold energy required by liquefied gaseous natural gas in a low-temperature liquefaction unit;
5) BOG generated by the LNG storage and transportation unit is conveyed to the low-temperature liquefaction unit through a pipeline, and the BOG and the incoming gaseous natural gas exchange heat in the low-temperature liquefaction unit to recover cold energy; BOG with increased temperature after heat exchange enters the purification unit 4 through a pipeline, the BOG in the purification unit 4 is pressurized and then used as regeneration gas of an adsorption purifier, and then enters the thermoacoustic engine unit 7 for combustion to drive the pulse tube refrigerator 8 to work;
6) and optionally conveying part of LNG of the LNG storage and transportation unit to a multistage pressure swing adsorption unit 5, enhancing the adsorption effect by using the low-temperature cold energy (the introduction amount of the LNG can be determined according to the actual condition), then entering a high-efficiency heat exchanger 6 of a low-temperature liquefaction unit to exchange heat with the concentrated coal bed gas, and finally conveying the LNG to a cold end heat exchanger of a pulse tube refrigerator 8 to be liquefied into finished LNG.
Example 1
As shown in fig. 2, after the coal bed gas comes out of the well site, the coal bed gas used for preparing the LNG portion enters a surge tank 1 of the pressurizing unit through a first pipeline 11, then sequentially flows through a supercharger 2 and a cooler 3 for pressurizing and cooling, and then enters a purification unit through a third pipeline 13 to remove acid gas, water and other impurities to reach a purification standard, so that the coal bed gas becomes high-pressure normal-temperature purified coal bed gas; the purified high-pressure normal-temperature coal bed gas enters the multistage pressure swing adsorption unit 5 through the fourth pipeline 14, the methane content is finally improved to the natural gas concentration through continuous alternate adsorption and desorption, the concentrated coal bed gas enters the high-efficiency heat exchanger 6 of the low-temperature liquefaction unit through the fifth pipeline 15 to exchange heat with the BOG from the ninth pipeline 19 and the gaseous natural gas from the fourteenth pipeline 24, then enters the cold end heat exchanger of the pulse tube refrigerator 8 through the sixth pipeline 16 to be liquefied into liquefied natural gas, the generated LNG enters the LNG storage tank 9 of the LNG storage and transportation unit through the seventh pipeline 17 to be temporarily stored, and finally is conveyed to the LNG tank wagon 10 through the eighth pipeline 18 to be transported.
And the other part of the coal bed gas from the well site directly enters the thermoacoustic engine unit 7 through the second pipeline 12 for combustion, and the pulse tube refrigerator 8 is driven to work through the twelfth pipeline 22 to provide the cold energy required by the liquefied gaseous natural gas in the low-temperature liquefaction unit.
BOG generated in an LNG storage tank 9 is conveyed into a high-efficiency heat exchanger 6 of a low-temperature liquefaction unit through a ninth pipeline 19, heat exchange is carried out between the BOG and the entering gaseous natural gas in the high-efficiency heat exchanger 6 to recover cold energy, the BOG with the increased temperature after heat exchange enters a purification unit 4 through a tenth pipeline 20, the BOG is pressurized in the purification unit 4 and then used as regeneration of an adsorption purifier, and finally the BOG is conveyed to a thermoacoustic engine unit 7 through an eleventh pipeline 21 to be combusted, and a pulse tube refrigerator 8 is driven to work through a twelfth pipeline 22 to provide cold energy required by the low-temperature liquefaction unit.
Part of LNG in the LNG storage tank 9 is conveyed to the multistage pressure swing adsorption unit 5 through a thirteenth pipeline 23, the low-temperature cold energy of the LNG is used for enhancing the adsorption effect (the introduction amount of the LNG can be determined according to actual conditions), then the LNG enters the high-efficiency heat exchanger 6 of the low-temperature liquefaction unit to exchange heat with the concentrated coal bed gas, then the LNG enters the cold end heat exchanger of the pulse tube refrigerator 8 through a fifteenth pipeline 25 to be liquefied into finished LNG, and finally the LNG enters the LNG storage tank through a sixteenth pipeline 26.
All components of each unit are skid-mounted structures convenient to move; by utilizing a thermoacoustic technology, the refrigerating machine of the arterial tube is driven by part of the coal bed gas to work, the cold quantity required by the low-temperature liquefaction unit is provided, and the liquefaction part does not need external power supply at all, so that the development of coal bed gas resources with small reserve, dispersion and remote is facilitated, and the exploitation range of the coal bed gas is expanded.
Claims (5)
1. A system for preparing LNG from oxygen-containing coal bed gas based on thermoacoustic technology is characterized by comprising a pressurization unit, a purification unit (4), a multi-stage pressure swing adsorption unit (5), a low-temperature liquefaction unit and an LNG storage and transportation unit which are sequentially connected; the thermoacoustic engine unit is connected with the low-temperature liquefaction unit;
the pressurizing unit is used for pressurizing coal bed gas and comprises a pressure stabilizing tank (1), a supercharger (2) and a cooler (3) which are sequentially connected, wherein the inlet of the pressure stabilizing tank (1) is directly communicated with the outlet of a coal bed gas well site;
the purification unit (4) is used for removing acid gas, water and impurities in the coal bed gas to obtain normal-temperature high-pressure purified coal bed gas only containing nitrogen, oxygen and methane, namely oxygen-containing coal bed gas;
the multistage pressure swing adsorption unit (5) comprises a plurality of adsorption towers, is used for adsorption and desorption, and is used for increasing the concentration of methane in the oxygen-containing coal bed gas to obtain gaseous natural gas;
the low-temperature liquefaction unit comprises a high-efficiency heat exchanger (6) and a pulse tube refrigerator (8) which are sequentially connected and is used for liquefying gaseous natural gas;
the LNG storage and transportation unit comprises an LNG storage tank (9) and an LNG tank car (10);
the inlet of the thermoacoustic engine unit is directly communicated with the outlet of the coal bed gas well field, the outlet of the thermoacoustic engine unit is directly communicated with the pulse tube refrigerator (8) in the low-temperature liquefaction unit, and the pulse tube refrigerator (8) is driven to work by burning part of the coal bed gas by using thermoacoustic technology, so that the cold energy required by the low-temperature liquefaction unit is provided.
2. The system of claim 1, wherein the pressurization unit, the purification unit (4), the multi-stage pressure swing adsorption unit (5), the cryogenic liquefaction unit, the thermoacoustic engine unit, and the LNG storage and transportation unit are skid-mounted structures that are easily moved.
3. The system according to claim 1, characterized in that the purification unit (4) comprises at least one set of adsorption purifiers.
4. The system of claim 1, wherein the multistage pressure swing adsorption unit (5) can employ automated control techniques to achieve automated adsorption and desorption processes.
5. A method of producing LNG using the system of claim 1, comprising the steps of:
1) coal bed gas extracted from a mine firstly enters a pressure stabilizing tank (1) of a pressurizing unit, then is pressurized by the pressure stabilizing tank (1) through a supercharger (2), then enters a cooler (3) for cooling, and enters a purifying unit (4) for purification after being cooled, so that acid gas, water and other impurities in the coal bed gas are removed, and the coal bed gas becomes normal-temperature high-pressure purified coal bed gas only containing nitrogen, oxygen and methane;
2) the purified oxygen-containing coal bed gas enters a multi-stage pressure swing adsorption unit (5), the methane content is increased to the natural gas concentration through continuous and alternate adsorption and desorption, and the concentrated coal bed gas is desorbed to obtain gaseous natural gas;
3) the method comprises the following steps that gaseous natural gas enters a low-temperature liquefaction unit, is cooled in the unit to become liquefied natural gas, then enters an LNG storage tank (9) of an LNG storage and transportation unit, and is transported out by an LNG tanker (10);
4) part of the coal bed gas extracted from a mine is directly introduced into a thermoacoustic engine unit (7), the entered coal bed gas is combusted, and a pulse tube refrigerator (8) is driven to work by using thermoacoustic technology, so that the cold energy required by the liquefied gaseous natural gas in the low-temperature liquefaction unit is provided;
5) boil Off Gas (BOG) generated by the LNG storage and transportation unit is conveyed to the low-temperature liquefaction unit through a pipeline, and the BOG and the entering gaseous natural Gas exchange heat in the low-temperature liquefaction unit to recover cold energy; BOG with increased temperature after heat exchange enters the purification unit (4) through a pipeline, the BOG is pressurized in the purification unit (4) and then used as regenerated gas of the adsorption purifier, and then enters the thermoacoustic engine unit (7) for combustion to drive the pulse tube refrigerator (8) to work;
6) and optionally conveying part of LNG of the LNG storage and transportation unit to a multi-stage pressure swing adsorption unit (5) through a pipeline, enhancing the adsorption effect by using the low-temperature cold energy of the LNG, then entering a high-efficiency heat exchanger (6) of a low-temperature liquefaction unit to exchange heat with the concentrated coal bed gas, and finally conveying the LNG to a cold end heat exchanger of a pulse tube refrigerator (8) to be liquefied into finished LNG.
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| CN103060036A (en) * | 2011-10-19 | 2013-04-24 | 中国科学院理化技术研究所 | Method and system for coalbed methane liquefaction |
| CN203474695U (en) * | 2013-09-03 | 2014-03-12 | 安徽淮化股份有限公司 | DMF (dimethyl formamide) purification device |
| CN210915967U (en) * | 2019-10-12 | 2020-07-03 | 浙江大学 | System for LNG is prepared to oxygen-bearing coal bed gas based on heat sound technique |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103060036A (en) * | 2011-10-19 | 2013-04-24 | 中国科学院理化技术研究所 | Method and system for coalbed methane liquefaction |
| CN203474695U (en) * | 2013-09-03 | 2014-03-12 | 安徽淮化股份有限公司 | DMF (dimethyl formamide) purification device |
| CN210915967U (en) * | 2019-10-12 | 2020-07-03 | 浙江大学 | System for LNG is prepared to oxygen-bearing coal bed gas based on heat sound technique |
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