CN103175381B - Low concentration coal-bed gas produces LNG technique containing oxygen cryogenic liquefying - Google Patents
Low concentration coal-bed gas produces LNG technique containing oxygen cryogenic liquefying Download PDFInfo
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Abstract
The invention discloses a kind of low concentration coal-bed gas and produce LNG technique containing oxygen cryogenic liquefying, comprising: 1) compress cleaning procedure; 2) liquefy separation circuit: comprising: a. main flow technique; B. refrigeration process: comprising: b
1. azeotrope technique; b
2. nitrogen cryogen technique: nitrogen cryogen is compressed, cooled by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler successively after cooling, nitrogen cryogen after throttling being entered overhead condenser and export cold, then the nitrogen cryogen of gaseous state being utilized by being back to nitrogen compressor cycle after subcooler, three grades of heat exchangers, secondary heat exchanger, first-class heat exchanger cascade raising temperature to normal temperature successively.By evaporation capacity at the bottom of azeotrope technology controlling and process tower, by nitrogen cryogen technology controlling and process overhead condensation amount, independently can adjust purity and the yield of gas product, and the cryogen of low-temperature space only has nitrogen component, there is not the heavy constituent such as iso-butane, isopentane, thus solution throttling is not freezed, or coolant channel blockage problem.
Description
Technical field
The invention belongs to and make gas or admixture of gas carry out the technical field liquefying, solidify or be separated by pressurization with cooling processing, concrete produces LNG technique for a kind of low concentration coal-bed gas contains oxygen cryogenic liquefying.
Background technology
Coalbed methane containing oxygen be colliery in recovery process for preventing gas explosion and outstanding, ensure Safety of Coal Mine Production and the elementary byproduct that pumps out, its main component is methane, and as can be seen from its component content, coal bed gas is the energy and the industrial chemicals of outbalance.But because its composition is comparatively complicated, particularly in coal bed gas, contain aerobic, it is breakneck combustion-supporting pro-knock agent, constrain the comprehensive utilization of coalbed methane containing oxygen, in practice, in order to cost-saving, coal bed gas generally enters air in coal mining process, cause resource profligacy and to environment.
Along with the development of technology, purify at low concentration coal-bed gas at present and produce in the field of natural gas, occurred the liquefaction technology of multiple coalbed methane containing oxygen.Publication number is that CN101922850A and CN101929788A individually discloses a kind of method of coalbed methane containing oxygen to prepare liquefied natural gas and utilize the device of coalbed methane containing oxygen to prepare liquefied natural gas of utilizing, the method and device adopt azeotrope self-cascade refrigeration system, unstripped gas after purification is liquefied and is separated, obtain LNG product, although the method and device can utilize coalbed methane containing oxygen to produce natural gas, also there is following problem:
(1) unstripped gas (i.e. low concentration coal-bed gas) comes from underground coal mine extraction, and methane content fluctuation is comparatively large, can affect the stable operation of liquefaction process unavoidably, need to adjust device; And the purity of gas product and yield are controlled by evaporation capacity at the bottom of tower and overhead condensation amount respectively in the method and device, but at the bottom of tower heating and for tower top cool refrigerant fluid be with one, therefore overhead condensation amount (yield) can be affected when adjusting product purity, equally, evaporation capacity at the bottom of tower (purity) can be had influence on again when adjusting product yield;
(2) if refrigerant compressor operating mode is unstable, the heavy constituent in a large amount of azeotrope (as iso-butane, isopentane) can be caused to enter the low-temperature space (temperature is lower than-165 DEG C) of liquefying plant, cause this section of refrigerant temperature lower than its lower conversion temperature, after making throttling, temperature raises (namely not freezing), also can cause time serious solidifying, coolant channel is blocked;
(3), after in coal bed gas, methane is suggested, the direct re-heat under the operating pressure (0.3MPa) of rectifying column of nitrogen oxygen tail gas is emptying, does not fully reclaim its energy (pressure energy), wastes energy.
In view of this, the present invention is intended to explore a kind of low concentration coal-bed gas and produces LNG technique containing oxygen cryogenic liquefying, this low concentration coal-bed gas produces containing oxygen cryogenic liquefying purity and the yield that LNG technique independently can not only adjust gas product, and can prevent coolant channel from blocking, and improve using energy source.
Summary of the invention
A kind of low concentration coal-bed gas is the object of the present invention is to provide to produce LNG technique containing oxygen cryogenic liquefying, this low concentration coal-bed gas produces containing oxygen cryogenic liquefying purity and the yield that LNG technique independently can not only adjust gas product, and can prevent coolant channel from blocking.
For realizing above-mentioned technical purpose, the invention provides following technical scheme:
A kind of low concentration coal-bed gas produces LNG technique containing oxygen cryogenic liquefying, comprising:
1) cleaning procedure is compressed: low concentration is purified coalbed methane containing oxygen containing after the compressed purification of oxygen coal seam unstripped gas;
2) liquefy separation circuit: comprise main flow technique and refrigeration process;
A. main flow technique: coalbed methane containing oxygen will be purified successively by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler heat exchange refrigeration, and enter rectifying column after throttling, be arranged on the reboiler at the bottom of rectifying tower outlet obtain liquefied natural gas, the tower top of rectifying column obtains nitrogen oxygen tail gas, and a small amount of methane component contained in nitrogen oxygen tail gas separated out by the overhead condenser utilizing rectifying column tower top to arrange;
B. refrigeration process: comprise azeotrope technique and nitrogen cryogen technique;
B
1. azeotrope technique: azeotrope is compressed, enter heavy hydrocarbon separator after cooling is separated into gas-liquid two-phase, wherein gas phase azeotrope is successively by after first-class heat exchanger and secondary heat exchanger cooling, enter liquid at the bottom of the reboiler heating tower be positioned at the bottom of rectifying tower, after throttling, gas phase azeotrope is exported colds by three grades of heat exchangers, secondary heat exchanger and first-class heat exchanger successively and circulating reflux utilizes to azeotrope compressor cycle; Liquid phase azeotrope is cooled by first-class heat exchanger and converges with the gas phase azeotrope of backflow after throttling and together with first-class heat exchanger, is back to azeotrope compressor cycle utilizes;
B
2. nitrogen cryogen technique: nitrogen cryogen is compressed, cooled by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler successively after cooling, nitrogen cryogen after throttling being entered overhead condenser and export cold, then the nitrogen cryogen of gaseous state being utilized by being back to nitrogen compressor cycle after subcooler, three grades of heat exchangers, secondary heat exchanger, first-class heat exchanger cascade raising temperature to normal temperature successively.
Further, the temperature of the purification coalbed methane containing oxygen obtained through described compression cleaning procedure is 40 DEG C, absolute pressure is 0.42MPa.
Further, described main flow technique comprises the steps:
A
1. coalbed methane containing oxygen will be purified successively by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler heat exchange refrigeration, and after throttling, form the mixture of condensate liquid and gas;
A
2. purification coalbed methane containing oxygen enters rectifying column from the middle part of rectifying column, condensate liquid flows to downwards at the bottom of tower, and a small amount of nitrogen oxygen tail gas carried that upwards volatilizees, flow out from condensate outlet after being heated by reboiler, and obtain that temperature is-143.5 DEG C, absolute pressure is 0.32 ~ 0.36MPa at condensate outlet, methane concentration be more than or equal to 99% liquefied natural gas, this liquefied natural gas is by three grades of heat exchanger heat exchange and to reach temperature be-155 DEG C ~-160 DEG C, pressure is storage with pressure after the supercooled state of 0.243MPa, obtains finished product natural gas;
A
3. the tower top of rectifying column obtains nitrogen oxygen tail gas and separates out after a small amount of methane component of carrying through overhead condenser, after subcooler re-heat, enter expander again, be expanded to the nitrogen oxygen tail gas after 0.15 ~ 0.18MPa successively by subcooler, after three grades of heat exchangers, secondary heat exchanger and first-class heat exchanger re-heats to normal temperature as the regeneration gas compressing cleaning procedure.
Further, step b
1in, the initial pressure of azeotrope is 0.26MPa, through azeotrope compressor compresses to 3.2-3.8Mpa, enters heavy hydrocarbon separator and be separated into gas-liquid two-phase after cooling;
After wherein gas phase azeotrope is cooled to-120 DEG C by first-class heat exchanger and secondary heat exchanger successively, enter liquefied natural gas at the bottom of the reboiler heating tower be positioned at the bottom of rectifying tower, self is cooled to-148 DEG C, is that the gas phase azeotrope of-160 DEG C exports colds by three grades of heat exchangers, secondary heat exchanger and first-class heat exchanger successively and circulating reflux utilizes to azeotrope compressor cycle after throttling by temperature;
Liquid phase azeotrope is cooled to-50 DEG C by first-class heat exchanger, and converges with the gas phase azeotrope of backflow after throttling and together with first-class heat exchanger, be back to azeotrope compressor cycle utilize.
Further, step b
2in, the initial pressure of nitrogen cryogen is 0.35MPa, through nitrogen compressor compresses to 3.2 ~ 3.5MPa,-172 DEG C are cooled to by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler successively after cooling, after throttling, the temperature of nitrogen cryogen is-182 DEG C, absolute pressure is 0.4MPa, entering overhead condenser and export cold, then the nitrogen cryogen of gaseous state being utilized by being back to nitrogen compressor cycle after subcooler, three grades of heat exchangers, secondary heat exchanger, first-class heat exchanger cascade raising temperature to normal temperature successively.
Further, described azeotrope is the mixture of nitrogen, methane, ethene, propane, isopentane.
Beneficial effect of the present invention is:
Low concentration coal-bed gas of the present invention produces LNG technique containing oxygen cryogenic liquefying, by refrigeration process being divided into relatively independent azeotrope technique and nitrogen cryogen technique, and by evaporation capacity at the bottom of the tower of azeotrope technology controlling and process rectifying column, by the overhead condensation amount of nitrogen cryogen technology controlling and process rectifying column, independently can adjust purity and the yield of gas product, and the cryogen of low-temperature space only has nitrogen component, there is not the heavy constituent such as iso-butane, isopentane, thus solution throttling is not freezed, or coolant channel blockage problem.
By the nitrogen oxygen tail gas that obtained by rectifying column tower top through expander, decompressor is emptying at normal temperatures and pressures, thus fully reclaims the energy of the nitrogen oxygen backflowed, and reaches the object of energy-saving and emission-reduction.
Accompanying drawing explanation
In order to make object of the present invention, technical scheme and beneficial effect clearly, the invention provides following accompanying drawing and being described:
Fig. 1 is that low concentration coal-bed gas of the present invention produces the schematic flow sheet of LNG process example containing oxygen cryogenic liquefying.
Detailed description of the invention
Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.
First be described being applicable to a kind of device producing natural gas that low concentration coal-bed gas of the present invention produces LNG technique containing oxygen cryogenic liquefying.
As shown in Figure 1, this low concentration coal-bed gas produces the device of natural gas containing oxygen cryogenic liquefying, comprises main flow system and refrigeration system.
Main flow system comprises first-class heat exchanger 1, secondary heat exchanger 2, three grades of heat exchangers 3, subcooler 4 and rectifying columns 5 successively along the coal bed gas flow direction after purification, rectifying column 5 tower top arranges overhead condenser 6, the reboiler 7 be positioned at the bottom of tower is set in rectifying column 5 tower, the nitrogen oxygen outlet that rectifying column 5 tower top is arranged is connected with the nitrogen oxygen outlet of overhead condenser 6, and at the bottom of the tower of rectifying column 5, condensate outlet is set, flow out for liquified natural gas.Choke valve V is provided with between the coal bed gas outlet of subcooler 4 and the coal bed gas entrance of rectifying column 5
f, throttling cooling can be carried out to coal bed gas.
Refrigeration system comprises the azeotrope circulatory system and nitrogen cycle system.The azeotrope circulatory system comprises azeotrope compressor 8, azeotrope cooler 9 and heavy hydrocarbon separator 10 successively along azeotrope flow direction.The gas phase azeotrope outlet of heavy hydrocarbon separator 10 is communicated in the gas phase azeotrope entrance of reboiler 7 successively by first-class heat exchanger 1 and secondary heat exchanger 2, the gas phase azeotrope outlet of reboiler 7 is successively by three grades of heat exchangers 3, secondary heat exchanger 2 and first-class heat exchanger 1 make gas phase azeotrope reflux and are communicated in the azeotrope entrance of azeotrope compressor 8, the liquid phase azeotrope outlet of heavy hydrocarbon separator 10 is by converging with the gas phase azeotrope of backflow after first-class heat exchanger 1, reflux together with first-class heat exchanger 1 after liquid phase azeotrope converges with gas phase azeotrope and enter azeotrope compressor 8, azeotrope is recycled.The azeotrope circulatory system also comprises choke valve V
1, the liquid phase azeotrope outlet of heavy hydrocarbon separator 10 is successively by first-class heat exchanger 1 and choke valve V
1converge, by arranging choke valve V with the gas phase azeotrope of backflow
1, expenditure and pressure can be carried out to liquid phase azeotrope.Choke valve V is provided with between the gas phase azeotrope outlet of reboiler 7 and three grades of heat exchangers 3
2, throttling cooling can be carried out to gas phase azeotrope.
Nitrogen cycle system comprises nitrogen compressor 11 and nitrogen cooler 12 successively along the flow direction of nitrogen cooling agent, the nitrogen outlet of nitrogen cooler 12 is communicated in the nitrogen entrance of overhead condenser 6 successively by first-class heat exchanger 1, secondary heat exchanger 2, three grades of heat exchangers 3 and subcooler 4, the nitrogen outlet of overhead condenser 6 is made nitrogen cooling agent reflux by subcooler 4, three grades of heat exchangers 3, secondary heat exchanger 2 and first-class heat exchanger 1 and is communicated in the nitrogen entrance of nitrogen compressor 11 successively, nitrogen is recycled, and provides cold to overhead condenser 6.Choke valve V is provided with between the nitrogen entrance of subcooler 4 and overhead condenser 6
3, can lower the temperature to nitrogen cooling agent.
This low concentration coal-bed gas produces the device of natural gas containing oxygen cryogenic liquefying, by refrigeration system being set to the azeotrope circulatory system and nitrogen cycle system, evaporation capacity at the bottom of the tower of rectifying column 5 and the overhead condensation amount by nitrogen cycle Systematical control rectifying column 5 is controlled by the azeotrope circulatory system, independently can adjust purity and the yield of gas product, and the cryogen of low-temperature space only has nitrogen component, there is not the heavy constituent such as iso-butane, isopentane, thus solution throttling is not freezed, or coolant channel blockage problem.
Further, main flow system also comprises decompressor 13, the nitrogen oxygen outlet of rectifying column 5 is communicated in the nitrogen oxygen intake of decompressor 13 by subcooler 4, enter cleaning procedure after the nitrogen oxygen outlet of decompressor 13 makes the re-heat of nitrogen oxygen by subcooler 4, three grades of heat exchangers 3, secondary heat exchanger 2 and first-class heat exchanger 1 successively.By arranging decompressor 13, make it emptying at normal temperatures and pressures, thus fully reclaim the energy of the nitrogen oxygen backflowed, reach the object of energy-saving and emission-reduction.
Further, the condensate outlet of rectifying column 5 is communicated in natural gas storage tank by three grades of heat exchangers 3, makes gas product reach supercooled state, is convenient to store.
Further, azeotrope cooler 9 and nitrogen cooler 12 are water cooler, can meet the cooling requirement of azeotrope and nitrogen cooling agent, and are cooled to design temperature.
The device producing natural gas containing oxygen cryogenic liquefying below in conjunction with above-mentioned low concentration coal-bed gas elaborates to the detailed description of the invention that low concentration coal-bed gas of the present invention produces LNG technique containing oxygen cryogenic liquefying.
As shown in Figure 1, the low concentration coal-bed gas of the present embodiment produces LNG technique containing oxygen cryogenic liquefying, comprising:
1) cleaning procedure is compressed: low concentration is purified coalbed methane containing oxygen containing after the compressed purification of oxygen coal seam unstripped gas, and the temperature of the purification coalbed methane containing oxygen that the compressed cleaning procedure of the present embodiment obtains is 40 DEG C, absolute pressure is 0.42MPa.
2) liquefy separation circuit: comprise main flow technique and refrigeration process.
A. main flow technique: coalbed methane containing oxygen will be purified successively by first-class heat exchanger 1, secondary heat exchanger 2, three grades of heat exchangers 3 and subcooler 4 heat exchange refrigeration, and by choke valve V
fenter rectifying column 5 after throttling, be arranged on the reboiler 7 at the bottom of rectifying column 5 tower outlet obtain liquefied natural gas, the tower top of rectifying column 5 obtains nitrogen oxygen tail gas, and utilize rectifying tower 5 push up arrange overhead condenser 6 separate out a small amount of methane component contained in nitrogen oxygen tail gas.
B. refrigeration process: comprise azeotrope technique and nitrogen cryogen technique.
B
1. azeotrope technique: azeotrope compresses through azeotrope compressor 8, enter heavy hydrocarbon separator 10 after azeotrope cooler 9 cools is separated into gas-liquid two-phase, after wherein gas phase azeotrope is lowered the temperature by first-class heat exchanger 1 and secondary heat exchanger 2 successively, enter liquid at the bottom of reboiler 7 heating tower be positioned at the bottom of rectifying column 5 tower, through choke valve V
2after throttling, gas phase azeotrope is exported cold by three grades of heat exchangers 3, secondary heat exchanger 2 and first-class heat exchanger 1 successively and circulating reflux recycles to azeotrope compressor 8; Liquid phase azeotrope is cooled by first-class heat exchanger 1 and by choke valve V
1converge with the gas phase azeotrope of backflow after throttling and together with first-class heat exchanger 1, be back to azeotrope compressor 8 recycle.
The technological parameter of the azeotrope technique of the present embodiment is as follows:
The initial pressure of the azeotrope of the present embodiment is 0.26MPa, is compressed to 3.2-3.8Mpa through azeotrope compressor 8, enters heavy hydrocarbon separator 10 and be separated into gas-liquid two-phase after cooling; After wherein gas phase azeotrope is cooled to-120 DEG C by first-class heat exchanger 1 and secondary heat exchanger 2 successively, enter liquefied natural gas at the bottom of reboiler 7 heating tower be positioned at the bottom of rectifying column 5 tower, self is cooled to-148 DEG C, is that the gas phase azeotrope of-160 DEG C exports cold by three grades of heat exchangers 3, secondary heat exchanger 2 and first-class heat exchanger 1 successively and circulating reflux recycles to azeotrope compressor 8 after throttling by temperature; Liquid phase azeotrope is cooled to-50 DEG C by first-class heat exchanger 1, and converge with the gas phase azeotrope of backflow after throttling and together with first-class heat exchanger 1, be back to azeotrope compressor 8 recycle, what can meet liquefied natural gas produces requirement, and controls evaporation capacity at the bottom of the tower of rectifying column 5.
B
2. nitrogen cryogen technique: nitrogen cryogen compresses through nitrogen compressor 11, through nitrogen cooler 12 cool after cooled by first-class heat exchanger 1, secondary heat exchanger 2, three grades of heat exchangers 3 and subcooler 4 successively, will through choke valve V
3nitrogen cryogen after throttling enters overhead condenser 6 and exports cold, is then recycled by being back to nitrogen compressor 11 after subcooler 4, three grades of heat exchangers 3, secondary heat exchanger 2, first-class heat exchanger 1 cascade raising temperature to normal temperature successively by the nitrogen cryogen of gaseous state.
The technological parameter of the nitrogen cryogen technique of the present embodiment is as follows:
The initial pressure of the nitrogen cryogen of the present embodiment is 0.35MPa, 3.2 ~ 3.5MPa is compressed to through nitrogen compressor 11, successively by first-class heat exchanger 1 after cooling, secondary heat exchanger 2, three grades of heat exchangers 3 and subcooler 4 are cooled to-172 DEG C, after throttling, the temperature of nitrogen cryogen is-182 DEG C, absolute pressure is 0.4MPa, enter overhead condenser 6 and export cold, then the nitrogen cryogen of gaseous state is passed through subcooler 4 successively, three grades of heat exchangers 3, secondary heat exchanger 2, be back to nitrogen compressor 11 after first-class heat exchanger 1 cascade raising temperature to normal temperature to recycle, what can meet liquefied natural gas produces requirement, and control the overhead condensation amount of rectifying column 5.
The low concentration coal-bed gas of the present embodiment produces LNG technique containing oxygen cryogenic liquefying, by refrigeration process being divided into relatively independent azeotrope technique and nitrogen cryogen technique, and by evaporation capacity at the bottom of the tower of azeotrope technology controlling and process rectifying column, by the overhead condensation amount of nitrogen cryogen technology controlling and process rectifying column, independently can adjust purity and the yield of gas product, and the cryogen of low-temperature space only has nitrogen component, there is not the heavy constituent such as iso-butane, isopentane, thus solution throttling is not freezed, or coolant channel blockage problem.
Further, the main flow technique of the present embodiment specifically comprises the steps:
A
1. coalbed methane containing oxygen will be purified successively by first-class heat exchanger 1, secondary heat exchanger 2, three grades of heat exchangers 3 and subcooler 4 heat exchange refrigeration, and through choke valve V
fthe mixture of condensate liquid and gas is formed after throttling;
A
2. purification coalbed methane containing oxygen enters rectifying column 5 from the middle part of rectifying column 5, condensate liquid flows to downwards at the bottom of tower, and a small amount of nitrogen oxygen tail gas carried that upwards volatilizees, flow out from condensate outlet after being heated by reboiler 7, and obtain that temperature is-143.5 DEG C, absolute pressure is 0.32 ~ 0.36MPa at condensate outlet, methane concentration be more than or equal to 99% liquefied natural gas, this liquefied natural gas is by the heat exchange of three grades of heat exchangers 3 and to reach temperature be-155 DEG C ~-160 DEG C, pressure is storage with pressure after the supercooled state of 0.243MPa, obtains finished product natural gas;
A
3. the tower top of rectifying column 5 obtains nitrogen oxygen tail gas and separates out after a small amount of methane component of carrying through overhead condenser 6, after subcooler 4 re-heat, enter decompressor 13 again to expand, be expanded to the nitrogen oxygen tail gas after 0.15 ~ 0.18MPa successively by after subcooler 4, three grades of heat exchangers 3, secondary heat exchanger 2 and first-class heat exchanger 1 re-heat to normal temperature as the regeneration gas compressing cleaning procedure.
Expanded through decompressor 13 by the nitrogen oxygen tail gas obtained by rectifying column 5 tower top, decompressor 13 is emptying at normal temperatures and pressures, thus fully reclaims the energy of the nitrogen oxygen backflowed, and reaches the object of energy-saving and emission-reduction.
Further, the azeotrope of the present embodiment is the mixture of nitrogen, methane, ethene, propane, isopentane, the temperature control requirement in the links produced at liquefied natural gas can be met, in azeotrope, the proportioning of each component sets according to the demand of actual refrigerating capacity, certainly, azeotrope also can adopt the azeotrope of other components existing, is not repeated.
What finally illustrate is, above preferred embodiment is only in order to illustrate technical scheme of the present invention and unrestricted, although by above preferred embodiment to invention has been detailed description, but those skilled in the art are to be understood that, various change can be made to it in the form and details, and not depart from claims of the present invention limited range.
Claims (4)
1. low concentration coal-bed gas produces a LNG technique containing oxygen cryogenic liquefying, it is characterized in that: comprising:
1) cleaning procedure is compressed: low concentration is purified coalbed methane containing oxygen containing after the compressed purification of oxygen coal seam unstripped gas;
2) liquefy separation circuit: comprise main flow technique and refrigeration process;
A. main flow technique: coalbed methane containing oxygen will be purified successively by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler heat exchange refrigeration, and enter rectifying column after throttling, be arranged on the reboiler at the bottom of rectifying tower outlet obtain liquefied natural gas LNG, the tower top of rectifying column obtains nitrogen oxygen tail gas, and a small amount of methane component contained in nitrogen oxygen tail gas separated out by the overhead condenser utilizing rectifying column tower top to arrange;
B. refrigeration process: comprise azeotrope technique and nitrogen cryogen technique;
B
1. azeotrope technique: azeotrope is compressed, enter heavy hydrocarbon separator after cooling is separated into gas-liquid two-phase; Wherein gas phase azeotrope is successively by after first-class heat exchanger and secondary heat exchanger cooling, enter liquid at the bottom of the reboiler heating tower be positioned at the bottom of rectifying tower, after throttling, gas phase azeotrope is exported colds by three grades of heat exchangers, secondary heat exchanger and first-class heat exchanger successively and circulating reflux utilizes to azeotrope compressor cycle; Liquid phase azeotrope is cooled by first-class heat exchanger and converges with the gas phase azeotrope of backflow after throttling and together with first-class heat exchanger, is back to azeotrope compressor cycle utilizes;
B
2. nitrogen cryogen technique: nitrogen cryogen is compressed, cooled by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler successively after cooling, nitrogen cryogen after throttling being entered overhead condenser and export cold, then the nitrogen cryogen of gaseous state being utilized by being back to nitrogen compressor cycle after subcooler, three grades of heat exchangers, secondary heat exchanger, first-class heat exchanger cascade raising temperature to normal temperature successively;
The temperature of the purification coalbed methane containing oxygen obtained through described compression cleaning procedure is 40 DEG C, absolute pressure is 0.52MPa;
Described main flow technique comprises the steps:
A
1. coalbed methane containing oxygen will be purified successively by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler heat exchange refrigeration, and after throttling, form the mixture of condensate liquid and gas;
A
2. purification coalbed methane containing oxygen enters rectifying column from the middle part of rectifying column, condensate liquid flows to downwards at the bottom of tower, and a small amount of nitrogen oxygen tail gas carried that upwards volatilizees, flow out from condensate outlet after being heated by reboiler, and obtain that temperature is-143.5 DEG C, absolute pressure is 0.32 ~ 0.36MPa at condensate outlet, methane concentration be more than or equal to 99% liquefied natural gas, this liquefied natural gas is by three grades of heat exchanger heat exchange and to reach temperature be-155 DEG C ~-160 DEG C, pressure is storage with pressure after the supercooled state of 0.243MPa, obtains finished product LNG;
A
3. the tower top of rectifying column obtains nitrogen oxygen tail gas and separates out after a small amount of methane component of carrying through overhead condenser, after subcooler re-heat, enter expander again, be expanded to the nitrogen oxygen tail gas after 0.15 ~ 0.18MPa successively by subcooler, after three grades of heat exchangers, secondary heat exchanger and first-class heat exchanger re-heats to normal temperature as the regeneration gas compressing cleaning procedure.
2. low concentration coal-bed gas according to claim 1 produces LNG technique containing oxygen cryogenic liquefying, it is characterized in that: step b
1in, the initial pressure of azeotrope is 0.26MPa, through azeotrope compressor compresses to 3.2-3.8Mpa, enters heavy hydrocarbon separator and be separated into gas-liquid two-phase after cooling;
After wherein gas phase azeotrope is cooled to-120 DEG C by first-class heat exchanger and secondary heat exchanger successively, enter liquefied natural gas at the bottom of the reboiler heating tower be positioned at the bottom of rectifying tower, self is cooled to-148 DEG C, is that the gas phase azeotrope of-160 DEG C exports colds by three grades of heat exchangers, secondary heat exchanger and first-class heat exchanger successively and circulating reflux utilizes to azeotrope compressor cycle after throttling by temperature;
Liquid phase azeotrope is cooled to-50 DEG C by first-class heat exchanger, and converges with the gas phase azeotrope of backflow after throttling and together with first-class heat exchanger, be back to azeotrope compressor cycle utilize.
3. low concentration coal-bed gas according to claim 2 produces LNG technique containing oxygen cryogenic liquefying, it is characterized in that: step b
2in, the initial pressure of nitrogen cryogen is 0.35MPa, through nitrogen compressor compresses to 3.2 ~ 3.5MPa,-172 DEG C are cooled to by first-class heat exchanger, secondary heat exchanger, three grades of heat exchangers and subcooler successively after cooling, after throttling, the temperature of nitrogen cryogen is-182 DEG C, absolute pressure is 0.4MPa, entering overhead condenser and export cold, then the nitrogen cryogen of gaseous state being utilized by being back to nitrogen compressor cycle after subcooler, three grades of heat exchangers, secondary heat exchanger, first-class heat exchanger cascade raising temperature to normal temperature successively.
4. the low concentration coal-bed gas according to any one of claim 1-3 produces LNG technique containing oxygen cryogenic liquefying, it is characterized in that: described azeotrope is the mixture of nitrogen, methane, ethene, propane, isopentane.
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| CN103484184B (en) * | 2013-09-05 | 2015-04-29 | 中国海洋石油总公司 | Deoxidation and denitrification system for oxygen-containing coal bed gas |
| CN105349195B (en) * | 2014-08-19 | 2017-10-03 | 中国海洋石油总公司 | A kind of oxygen-containing coal bed gas deoxidation, the liquefaction process of denitrogenation |
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| CN105605883A (en) * | 2016-03-25 | 2016-05-25 | 北京中科瑞奥能源科技股份有限公司 | Oxygen-bearing coalbed methane liquefaction separation system and technique |
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