CN105371590A - Full-cooling-capacity-recovery natural gas liquefaction process with precooling and mixed refrigeration - Google Patents
Full-cooling-capacity-recovery natural gas liquefaction process with precooling and mixed refrigeration Download PDFInfo
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- CN105371590A CN105371590A CN201410440647.6A CN201410440647A CN105371590A CN 105371590 A CN105371590 A CN 105371590A CN 201410440647 A CN201410440647 A CN 201410440647A CN 105371590 A CN105371590 A CN 105371590A
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Abstract
The invention discloses a full-cooling-capacity-recovery natural gas liquefaction process with precooling and mixed refrigeration. By means of the process, cooling capacity provided by a precooling system and a mixed refrigeration system is fully recovered, the overall energy consumption of natural gas or methane-containing gas liquefaction is lowered, the inlet gas temperature of a precooling compressor and a refrigeration compressor is 0-40 DEG C and is consistent with the gas inlet condition of an ordinary compressor, and domestication of liquefaction devices is facilitated. The process has the beneficial effects of being simple in flow, convenient to implement, high in efficiency, low in running expense, high in adaptability, and the like.
Description
1, technical field
The present invention relates to natural gas or the liquefaction field containing methane gas, the full hybrid refrigeration liquefied natural gas process reclaiming the band chilldown system of cold.
2, background technology
After natural gas liquefaction, volume is original 1/625, very favourable to the storage of natural gas, transport and reasonable utilization.And the investment of gas liquefaction part accounts for the 25%-50% of gross investment, therefore, select rational natural gas liquefaction process, to saving gross investment, reduce energy consumption, the economical operation index improving liquefying plant has great importance.
Liquefaction process ripe in area of natural gas liquefaction mainly contains following three kinds: class's formula kind of refrigeration cycle technique, hybrid refrigeration cycle technique and expander refrigeration circulation technology.
(1) class's formula kind of refrigeration cycle class formula kind of refrigeration cycle by three independently refrigeration system form.The advantage of class's formula kind of refrigeration cycle have employed 3 kinds of cold-producing mediums, 9 cryogenic temperature gradients (propane, ethane or ethene, each 3 temperature grades of methane), make the cooling curve of cryogenic temperature at different levels and unstripped gas close, specific energy consumption is close to the upper limit of the thermodynamic efficiency of theory.And this technological operation is flexible, start-stop car is quick, and the initial stage that is easy to drives to go into operation.
But also there are some shortcomings in class's formula refrigeration, needs three recycle compressors, and a considerable amount of cold exchange device; Long flow path, equipment are many, control is complicated.
(2), azeotrope circulation because class formula refrigerating circulatory device complicated, invest high, develop hybrid refrigeration cycle (MixedRefrigerantCycle, MRC) for this reason.With a kind of cold-producing medium (being generally hydrocarbon mixture, as N2, C1 ~ C5 etc.), its Q-T curve and raw natural gas are close to consistent.Utilize the feature of mixture partial condensation to reach required different temperatures level, both remained the advantage of cascade refrigeration circulation, and only had again 1 compressor, make process simplification, cost also can reduce.Say in principle, the mixture be made up of N2, C1 ~ C5 etc., its proportion of composing should form according to raw natural gas, technological process, operation pressure and different.Once determine that rear composition not easily adjusts, namely enablely this point is accomplished, make whole liquefaction process (from normal temperature to-162 DEG C) also be all very difficult by cooling curve to provide required cold, local or a part can only accomplish the Q-T curve of raw natural gas at most.Therefore the flow process of MRC has been simply, but its efficiency is than low through cascade refrigeration circulation.
On the basis of azeotrope circulation, develop into the MRC technique of band propane pre-cooling, be called for short C3/MRC technique, its efficiency is close to class's formula circulation.
This ratio juris is points of two sections supply colds: high temperature section propane compression freezes, by 3 or 4 temperature levels precooling raw natural gas to ~-40 DEG C; The heat exchange of low-temperature zone adopts mixed refrigeration process.Fully demonstrate the characteristic on thermodynamics, thus efficiency is improved to greatest extent.
(3) circulation of expander refrigeration circulation expander refrigeration refers to and utilizes high-pressure refrigerant to realize the liquefaction of natural gas by the Claude cycle refrigeration of turbo-expander adiabatic expansion.Gas expands while cooling in decompressor, energy output work, can be used for driving the compressor in flow process.Circulate with cascade refrigeration and to compare with azeotrope kind of refrigeration cycle technique, nitrogen expansion circulation process is very simple, compact, and cost is lower slightly.Start fast, hot starting can obtain product at full capacity, flexible operation, strong adaptability in 2 ~ 4 hours, is easy to operate and control, and security is good, and emptying can not cause fire or explosion danger.Cold-producing medium adopts single-component gas, thus eliminates the trouble of separation as azeotrope kind of refrigeration cycle technique and storage cold-producing medium, it also avoid the safety problem brought thus, liquefaction process is more simplified with compact.But energy consumption is higher than azeotrope liquefaction flow path by about 40%.
With the MRC technique of propane pre-cooling, because its efficiency circulates close to stepwise, and flow process compared with simple, unit is few, energy consumption is low, small investment.But the circulation of this technique propane pre-cooling adopts first compression three grades or level Four circulating with choke, control complicated.Precooling compressor gas inlet temperature about-30 ~-40 DEG C, hybrid refrigeration compressor gas inlet temperature about-40 DEG C, and propane cold and mix refrigerant cold do not reclaim completely.
The cold that pre-cold-peace mixed refrigeration systems produces makes full use of by the present invention, and control simple, easy to operate, energy consumption is low, and pre-cold compressor and refrigeration compressor inlet temperature control at 0 ~ 40 DEG C.
3, summary of the invention
One of measure that the present invention takes is first system cold cold recovery exchanger cooling after natural gas via compression and circulating water. enter forecooler again, and then liquefy through heat exchanger, excessively cold.
Two of the measure that the present invention takes is that first the precooling agent after compressed and circulating water enters precooling cold recovery exchanger, then through reducing pressure by regulating flow at least one times to being applicable to pressure, precooling agent is as the low-temperature receiver of natural gas and cold-producing medium, then, precooling agent returns the low-temperature receiver of precooling cold recovery exchanger as precooling cold recovery exchanger again, go out the precooling agent temperature about 0 ~ 40 DEG C of precooling cold recovery exchanger, enter pre-cold compressor.
Three of the measure that the present invention takes is the compressed refrigeration cold recovery exchanger coolings laggard with circulating water of mix refrigerant, enter forecooler cooling again, mix refrigerant after cooling after throttling as mix refrigerant cooling itself, liquefaction and natural gas cooling, liquefaction, excessively cold low-temperature receiver, then, mix refrigerant returns refrigeration cold recovery exchanger and carries out cold recovery, and mix refrigerant temperature rises to 0 ~ 40 DEG C of system cold compressor
4, accompanying drawing explanation
Fig. 1 is precooling and the hybrid refrigeration liquefaction process schematic diagram of a natural band of gas throttling of entirely reclaiming cold.
Fig. 2 is precooling and the hybrid refrigeration liquefaction process schematic diagram of the natural band of gas second throttle entirely reclaiming cold.
In figure, each mark is as follows: 1 refrigeration compressor, 2 circulating cooling water coolers, 3 circulating cooling water coolers, 4 refrigeration cold recovery exchanger, 5 forecoolers, 6 heat exchangers, 7 heat exchangers, 8 choke valves, 9 choke valves, 10 gas-liquid separators, 11 pre-cold compressor, 12 circulating cooling water coolers, 13 precooling cold recovery exchanger, 14 blenders, 15 choke valves, 16 precooling gas-liquid separators, 17 secondary forecoolers, 18 secondary precooling cold recovery exchanger, 19 blenders, 20 choke valves, 21 secondary precooling gas-liquid separators.
5, detailed description of the invention
Below in conjunction with accompanying drawing, the present invention will be further described, but the present invention is not limited to following examples.
Embodiment 1
As shown in Figure 1, every day 120,000, standard cubic meter natural gas liquefaction device adopted the complete precooling and the hybrid refrigeration liquefaction process that reclaim a natural band of gas throttling of cold, natural gas via compressor boost is to 5.0MPa, then purify, enter after dry, essence filter precooling and the hybrid refrigeration liquefaction process of a natural band of gas throttling of the full recovery cold described in this patent through the decarburization of MDEA method, molecular sieve dehydration, demercuration etc., obtain liquefied natural gas product.
Raw natural gas component is 92.5% methane, 3.6% ethane, 2.2% propane, 0.5% butane, 0.7% iso-butane, 0.2% isopentane, 0.3% pentane..
Be described as follows:
Natural gas via compressor boost, to 5.0MPa, then purifies through the decarburization of MDEA method, molecular sieve dehydration, demercuration etc., enters refrigeration cold recovery exchanger 4 and lower the temperature from the mix refrigerant heat exchange of heat exchanger 6 after dry, essence filter.Natural gas after cooling is cooled to precooling agent heat exchange in forecooler 5 ~ and-35 DEG C.Then lower the temperature with mix refrigerant heat exchange in heat exchanger 6, liquefy, temperature about-95 DEG C.
Liquefied natural gas in the heat exchanger 7 cross be as cold as ~-159 DEG C after through reducing pressure by regulating flow to be applicable to pressure enter LNG tank.
The explanation of hybrid refrigeration cycle system, mix refrigerant is pressurized to about 2..8MPa through refrigeration compressor 1, after supercharging, mix refrigerant is first cooled to 35 DEG C through recirculated cooling water 2,3, to lower the temperature laggard forecooler 5 through refrigeration cold recovery exchanger 4 again, cool the temperature to ~-35 DEG C, the low-temperature receiver of forecooler 5 is provided by propane precooling system, mix refrigerant system cold air liquid/gas separator 10 after cooling, cools through heat exchanger 6 from the liquid of refrigeration gas-liquid separator 10 and is mixed as the low-temperature receiver of heat exchanger 6 with the mix refrigerant of heat exchanger 7 after choke valve 8.From refrigeration gas-liquid separator 10 gas through heat exchanger 6 and heat exchanger 7 lower the temperature and after choke valve 9 as the low-temperature receiver of heat exchanger 7.From the heat exchanger 6 cold cold recovery exchanger 4 of mix refrigerant system out as low-temperature receiver, mix refrigerant temperature rises to ~ 32 DEG C of system cold compressor 1.
The explanation of pre-cooling cycle system, precooling agent propane is pressurized to 1.4MPa through pre-cold compressor 11, precooling agent after supercharging is first cooled to 35 DEG C through recirculated cooling water 12, lower the temperature through precooling cold recovery exchanger 13 again, then be depressurized to about 0.12MPa through choke valve 15 and enter precooling gas-liquid separator 16, the liquid precooling agent after separation is entered forecooler 5 and is made low-temperature receiver.The gas precooling agent of the precooling agent and precooling gas-liquid separator 16 that go out forecooler 5 enters blender 14 together, mixed precooling agent is as the low-temperature receiver of precooling cold recovery exchanger 13, go out the precooling agent temperature about ~ 33 DEG C of precooling cold recovery exchanger 13, enter pre-cold compressor 11.
Embodiment 2
As shown in Figure 2, every day 300,000, standard cubic meter natural gas liquefaction device adopted the complete precooling and the hybrid refrigeration liquefaction process that reclaim the natural band of gas second throttle of cold, natural gas via compressor boost is to 4.6MPa, then purify, enter after dry, essence filter precooling and the hybrid refrigeration liquefaction process of the natural band of gas second throttle of the full recovery cold described in this patent through the decarburization of MDEA method, molecular sieve dehydration, demercuration etc., obtain liquefied natural gas product.
Raw natural gas component is 95.3% methane, 2% ethane, 1.5% propane, 0.6% butane, 0.3% iso-butane, 0.2% isopentane, 0.1% pentane..
Be described as follows:
Natural gas via compressor boost, to 4.6MPa, then purifies through the decarburization of MDEA method, molecular sieve dehydration, demercuration etc., enters refrigeration cold recovery exchanger 4 and lower the temperature from the mix refrigerant heat exchange of heat exchanger 6 after dry, essence filter.Natural gas after cooling is cooled to precooling agent heat exchange in forecooler 5 ~ and-12 DEG C, then be cooled to the precooling agent heat exchange in secondary forecooler 17 ~-40 DEG C.Then lower the temperature with mix refrigerant heat exchange in heat exchanger 6, liquefy, temperature about-95 DEG C.
Liquefied natural gas in the heat exchanger 7 cross be as cold as ~-159 DEG C after through reducing pressure by regulating flow to be applicable to pressure enter LNG tank.
The explanation of hybrid refrigeration cycle system, mix refrigerant is pressurized to about 3.0MPa through refrigeration compressor 1, after supercharging, mix refrigerant is first through recirculated cooling water 2, 3 are cooled to 35 DEG C, to lower the temperature laggard forecooler 5 and secondary forecooler 17 through refrigeration cold recovery exchanger 4 again, cool the temperature to ~-40 DEG C, forecooler 5, the low-temperature receiver of secondary forecooler 17 is provided by propylene chilldown system, mix refrigerant system cold air liquid/gas separator 10 after cooling, cool through heat exchanger 6 from the liquid of refrigeration gas-liquid separator 10 and be mixed as the low-temperature receiver of heat exchanger 6 with the mix refrigerant of heat exchanger 7 after choke valve 8.From refrigeration gas-liquid separator 10 gas through heat exchanger 6 and heat exchanger 7 lower the temperature and after choke valve 9 as the low-temperature receiver of heat exchanger 7.From the heat exchanger 6 cold cold recovery exchanger 4 of mix refrigerant system out as low-temperature receiver, mix refrigerant temperature rises to ~ 30 DEG C of system cold compressor 1.
The explanation of pre-cooling cycle system, precooling agent propylene is pressurized to about 1.8MPa through pre-cold compressor 11, precooling agent after supercharging is first cooled to 35 DEG C through recirculated cooling water 12, part precooling agent cools through precooling cold recovery exchanger 13, another part precooling agent is lowered the temperature through secondary precooling cold recovery exchanger 18, be depressurized to about 0.35MPa through choke valve 15 after above two parts precooling agent mixing and enter precooling gas-liquid separator 16, the liquid precooling agent part after separation is entered forecooler 5 and is made low-temperature receiver.The gas precooling agent of the precooling agent and precooling gas-liquid separator 16 that go out forecooler 5 enters blender 14 together, mixed precooling agent is as the low-temperature receiver of precooling cold recovery exchanger 13, go out the precooling agent temperature about ~ 31 DEG C of precooling cold recovery exchanger 13, enter pre-cold compressor 11 secondary inlet; Be depressurized to about 0.12MPa through choke valve 20 again from another part precooling agent of precooling gas-liquid separator 16 and enter secondary precooling vapour liquid separator 21, the liquid precooling agent after separation is entered secondary forecooler 17 and is made low-temperature receiver.The gas precooling agent of the precooling agent and secondary precooling vapour liquid separator 21 that go out secondary forecooler 17 enters blender 19 together, mixed precooling agent is as the low-temperature receiver of secondary precooling cold recovery exchanger 18, go out the precooling agent temperature about ~ 30 DEG C of secondary precooling cold recovery exchanger 18, enter pre-cold compressor 11 one-level entrance.
Claims (9)
1. complete natural band of gas precooling and the hybrid refrigeration liquefaction process reclaiming cold, is characterized in that comprising pre-cooling cycle, hybrid refrigeration cycle and NG Liquefaction cycle.
2. pre-cooling cycle according to claim 1, hybrid refrigeration cycle and NG Liquefaction cycle, it is characterized in that precooling agent is propylene, propane or other materials, mix refrigerant is the hydrocarbon mixture of nitrogen and C1 ~ C4.
3. pre-cooling cycle according to claim 1, it is characterized in that precooling agent through precooling compressor boost to being applicable to pressure, after supercharging, precooling agent is first cooled to through circulating cooling water cooling or air-cooled etc. and is less than 40 DEG C, now precooling agent all or part of liquefaction, lower the temperature through precooling cold recovery exchanger again, then through reducing pressure by regulating flow at least one times to being applicable to pressure, precooling agent is as the low-temperature receiver of natural gas and cold-producing medium, then, precooling agent returns the low-temperature receiver of precooling cold recovery exchanger as precooling cold recovery exchanger again, go out the precooling agent temperature about 0 ~ 40 DEG C of precooling cold recovery exchanger, enter pre-cold compressor.
4. pre-cooling cycle according to claim 1, it is characterized in that precooling agent after the cooling of precooling cold recovery exchanger again after different throttling number of times after step-down, precooling agent pressure is different, after the medium semen donors that need cool to natural gas and cold-producing medium etc., return the recovery cold of precooling cold recovery exchanger again, the precooling agent gas of different pressures enter pre-cold compressor with precooling agent pressure relative to entrance.
5. hybrid refrigeration cycle according to claim 1 is characterised in that mix refrigerant is pressurized to applicable pressure through refrigeration compressor, after supercharging, mix refrigerant is first cooled to through circulating cooling water cooling or air-cooled etc. and is less than 40 DEG C, to lower the temperature the cooling of laggard forecooler through refrigeration cold recovery exchanger again, the mix refrigerant after cooling after throttling as mix refrigerant cooling itself, liquefaction and natural gas cooling, liquefaction, excessively cold low-temperature receiver.
6. hybrid refrigeration cycle according to claim 1 is characterised in that mix refrigerant carries out cold recovery through refrigeration cold recovery exchanger, and mix refrigerant temperature rises to 0 ~ 40 DEG C of system cold compressor.
7. after NG Liquefaction cycle according to claim 1 is characterised in that purification, natural gas is first through refrigeration cold recovery exchanger and forecooler cooling, then through heat exchanger liquefaction, excessively cold.
8. pre-cooling cycle according to claim 1, hybrid refrigeration cycle and NG Liquefaction cycle, its cold recovery can adopt multiple combination form, its objective is and reclaims chilldown system and refrigeration system residue cold.
9. a full technique reclaiming cold extends to class's formula kind of refrigeration cycle technique.
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| CN201410440647.6A CN105371590A (en) | 2014-09-02 | 2014-09-02 | Full-cooling-capacity-recovery natural gas liquefaction process with precooling and mixed refrigeration |
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| CN201410440647.6A CN105371590A (en) | 2014-09-02 | 2014-09-02 | Full-cooling-capacity-recovery natural gas liquefaction process with precooling and mixed refrigeration |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105737516A (en) * | 2016-04-18 | 2016-07-06 | 中国寰球工程公司 | System and method for liquefying natural gas by mixed refrigerant precooling and nitrogen expansion |
| CN106895662A (en) * | 2017-03-10 | 2017-06-27 | 蚌埠市荣强压缩机制造有限公司 | A kind of small-scaled natural gas liquification device |
-
2014
- 2014-09-02 CN CN201410440647.6A patent/CN105371590A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105737516A (en) * | 2016-04-18 | 2016-07-06 | 中国寰球工程公司 | System and method for liquefying natural gas by mixed refrigerant precooling and nitrogen expansion |
| CN106895662A (en) * | 2017-03-10 | 2017-06-27 | 蚌埠市荣强压缩机制造有限公司 | A kind of small-scaled natural gas liquification device |
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Application publication date: 20160302 |