CN102052821A - 一种空气分离方法 - Google Patents
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 478
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- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000567 combustion gas Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
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- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
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- 239000004575 stone Substances 0.000 description 1
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Abstract
本发明涉及一种空气分离方法,不仅使用了液化天然气的冷量,还增设了增压透平膨胀机提供部分冷量。采用这种方法后,不仅降低了液化空气产品的电耗,还可在相同的液化天然气气化量的情况下增加液体空分产品的产量,实现循环经济和节能减排。
Description
技术领域
本发明涉及一种空气分离方法,具体地说,涉及一种利用液化天然气冷量的空气分离方法。
背景技术
在本发明提出之前,由于空气的液化温度很低(临界温度为-140.7℃),在低温下通过精馏来分离空气的方法要求外界提供大量的能量来获取相当的冷量。液化天然气(简称LNG)作为清洁燃料正在推广使用。液化天然气的主要成份是甲烷,常压下的蒸发温度为-160℃左右。将液化天然气作为燃料来使用时,必须将液化天然气气化并加热到常温。如果将液化天然气的冷量应用到空气分离装置中去,无论对空气分离还是对液化天然气的使用都是一举两得的好事。
从安全出发,常采用氮气与液化天然气进行冷量交换,因此利用液化天然气冷量的空气分离方法常采用氮气循环的方式。一般说来,经过压缩和净化后的干净原料空气由冷量交换而达到饱和温度或部分带液后进入精馏塔。精馏塔由下塔,上塔及主冷凝蒸发器组成。原料空气在精馏塔的下塔进行初步分离,在其底部得到富氧液空。该富氧液空被引出后经过过冷和节流膨胀作为回流液进入上塔。在下塔的顶部得到气氮,部分气氮在冷凝蒸发器内被液氧所冷凝,冷凝后的一部分液氮成为下塔的回流液,另一部分液氮从冷凝蒸发器中引出后去与另一部分液氮汇合。一部分气氮从下塔的顶部引出后经过热交换器被加热后部分可作为产品引出,其余部分则与另一股氮气汇合后进入氮气增压机,提高了压力的氮气经过水冷却器冷却后进入液化天然气热交换器。在该热交换器中氮气被冷却和冷凝成液氮,而液化天然气在该换热器中得到气化和被加热成为天然气后离开以作它用。离开热交换器的液氮经过节流膨胀后进入气液分离器,分离出来的液氮与从主冷凝蒸发器引出的液氮合并,经过过冷后少部分可作为产品引出,大部分则经过节流后送入上塔作为上塔的回流液。分离出来的气氮则返回液化天然气热交换器被加热后与从下塔引出的经热交换器被加热的气氮汇合进入氮气增压机,完成了氮气循环。在精馏塔的上塔底部可得到液氧和气氧,在顶部可得到返流污氮(和返流氮)。应用液化天然气的冷量来分离空气的方法和装置,单位产品的电耗已有较大下降,但对于生产液氧和液氮的装置来说电耗仍比较高,还有降低的余地。
发明内容
本发明的目的是提供一种低电耗、高安全性的空气分离方法。
为达到上述目的,本发明采用的技术方案是:
一种空气分离方法,包括
经过压缩机压缩并在预冷系统中冷却、在净化系统中除去有害杂质的空气由冷量交换而达到饱和温度或部分带液后,进入精馏塔参与精馏,
精馏塔包括上塔、下塔、主冷凝蒸发器,
在所述的上塔的底部获得的液氧经液空过冷器后作为产品引出,在所述的上塔的上部得到的纯气氮、污气氮经液氮过冷器、液空过冷器及主换热器复热后推出,
由所述的下塔的底部得到的富氧液空经液空过冷器被纯气氮、污气氮过冷后,经过节流膨胀进入所述的上塔成为回流液,
由所述的下塔的顶部获得的一部分氮气冷凝成液氮后参与精馏或作为产品外供,
由所述的下塔的顶部获得的另一部分氮气参与氮气循环后回到所述的下塔将冷量传递至所述的精馏塔中,
所述的氮气循环包括冷量源、将冷量源的冷量传递给由所述的下塔的顶部获得的另一部分氮气的封闭氮气循环,所述的冷量源为液化天然气,所述的封闭氮气循环中的氮气在液化天然气换热器中与液化天然气进行热量交换后经过氮液化过冷器冷却后成为液氮,经节流后得到的液氮再经过氮冷凝蒸发器与由所述的下塔的顶部获得的另一部分氮气进行热量交换,然后在主换热器中被气化为氮气后再转化为封闭氮气循环中的氮气,完成所述的封闭氮气循环;
所述的空气分为两路,一路空气在主换热器中冷却降温后,进入精馏塔参与精馏,另一路空气进入膨胀机的增压端增压后通过水冷却器冷却,再进入主换热器中冷却到一定温度,然后进入膨胀机的膨胀端膨胀,最后进入所述的上塔的适当位置参与精馏。
优选的,由所述的下塔的顶部获得的一部分氮气在主冷凝蒸发器或在所述的氮冷凝蒸发器中冷凝成液氮。
优选的,经过氮液化过冷器冷却为的液氮的一部分节流得到的液氮经氮液化过冷器复热后,再经液化天然气换热器加热到规定温度后与在液化天然气换热器中冷却到规定温度的氮气汇合为进气氮气后进入低温氮压机的一段压缩,得到气氮,气氮经液化天然气换热器冷却后成为低温氮压机的二段的进气氮气进入低温氮压机的二段压缩。
优选的,经过氮液化过冷器冷却为的液氮的一部分节流得到的液氮经氮液化过冷器复热后,再经液化天然气换热器加热到规定温度后与氮气汇合成进气氮气后进入低温氮压机的二段压缩,得到封闭氮气循环中的氮气。
优选的,所述的低温氮压机为无油润滑活塞式压缩机或透平压缩机,所述的低温氮压机为一台或两台。
优选的,所述的进入低温氮压机的一段的进气氮气的温度低于-70℃。
优选的,所述的进入低温氮压机的二段的进气氮气的温度低于-70℃。
优选的,封闭氮气循环中的氮气的压力大于3.4MPa。
优选的,在所述的低温氮压机的一段、低温氮压机的二段的进出口管的合适位置设置有碳氢化合物在线控制仪。
由于上述技术方案运用,本发明与现有技术相比具有下列优点:由于本发明的空气分离方法采用独立的封闭氮气循环将液化天然气的冷量传递至精馏设备中,避免了天然气混入空分设备而带来的危险,提高了安全性,同时,采用液化天然气的冷量来为空气分离提供冷量,使单位产品的电耗降低,符合节能环保的要求。
附图说明
附图1为本发明的空气分离方法的实施例一的示意图。
以上附图中:1、主换热器;2、下塔;3、主冷凝蒸发器;4、上塔;5、液氮过冷器;6、液空过冷器;7、氮冷凝蒸发器;8、膨胀机的膨胀端;9、膨胀机的增压端;10、水冷却器;11、液化天然气换热器;12、氮液化过冷器;13、低温氮压机的一段;14、低温氮压机的二段;
101、经冷却、净化后的空气;102、空气;103、空气;104是经增压、冷却后的空气;105、膨胀后的空气;106、富氧液空;107、氮气;108、氮气;109、氮气;110、参与精馏的液氮;111、液氮;112、参与精馏的液氮;113、产品液氮;114、纯气氮;115、污气氮;116、液氧;117、氩馏分;118、液氮;
201、冷却到规定温度的氮气;202、进气氮气;203、气氮;204、进气氮气;205、封闭氮气循环中的氮气;206、液氮;207、节流得到的液氮;208、节流得到的液氮;209、节流得到的液氮;
301、液化天然气。
具体实施方式
下面结合附图所示的实施例对本发明作进一步描述。
实施例一:参见附图1所示。
一种空气分离方法,将空气通入包括上塔4、下塔2、主冷凝蒸发器3的精馏塔中精馏,来获得液氧、液氮、液氩等产品。
经过压缩机压缩并在预冷系统中冷却、在净化系统中除去水蒸汽、二氧化碳等有害杂质的空气101分为两路,一路空气102在主换热器1中由冷量交换而达到饱和温度或部分带液后,进入下塔2的底部成为下塔2的上升气流而参与精馏,另一路空气103进入膨胀机的增压端9增压后通过水冷却器10冷却,再进入主换热器1中冷却到一定温度,然后进入膨胀机的膨胀端8膨胀,最后进入上塔4的适当位置参与精馏。由于另一路空气103的增设,可将膨胀后的低压低温空气直接送入上塔4参与精馏,可以在使用相同的液化天然气气化量的情况下,生产出更多的空分产品。
在上塔4的底部获得的液氧116经液空过冷器6后作为产品引出,在上塔4的上部得到的纯气氮114、污气氮115经液氮过冷器5、液空过冷器6及主换热器1复热后推出。
由下塔2的底部得到的富氧液空106在液空过冷器6中被纯气氮114、污气氮115过冷后,经过节流膨胀进入上塔4成为上塔4的回流液之一。
由下塔的顶部获得的氮气107分为两部分,一部分氮气108进入主冷凝蒸发器3中冷凝成液氮118,另一部分氮气109在氮冷凝蒸发器7中冷凝而参与氮气循环后回到下塔2将冷量传递至精馏塔中。
液氮118分为两路,一路液氮110成为下塔2的回流液,另一路液氮111经过液氮过冷器5被由上塔4顶部获得的纯气氮114和由上塔上部引出的污气氮115过冷,少部分作为产品液氮113外供,大部分经过节流膨胀进入上塔4的顶部成为112成为参与精馏的液氮,作为上塔4的另一股回流液。另一路液氮111也可由氮冷凝蒸发器7引出。
氮气循环包括冷量源、将冷量源的冷量传递给由下塔2的顶部获得的另一部分氮气109的封闭氮气循环。冷量源为液化天然气301。
封闭氮气循环中的氮气205在液化天然气换热器11中与液化天然气301进行热量交换并经过氮液化过冷器12冷却后成为液氮206,液化天然气301在液化天然气换热器11中被气化加热到0℃以上后送出作燃气。液氮206经节流后得到的液氮209经过氮冷凝蒸发器7与由下塔2的顶部获得的另一部分氮气109进行热量交换,热量交换后在主换热器1中被气化为氮气201。液氮206的一部分节流得到的液氮208经氮液化过冷器12复热后,经液化天然气换热器11加热到规定温度,然后与经液化天然气换热器11冷却到规定温度的氮气201汇合为进气氮气202,进气氮气202进入低温氮压机的一段13压缩,得到气氮203。液氮206的另一部分节流得到的液氮207经氮液化过冷器12复热后,与经液化天然气换热器11加热到规定温度的气氮203汇合为进气氮气204,进气氮气204进入低温氮压机的二段14压缩到所需的压力,得到封闭氮气循环中的氮气205,完成封闭氮气循环,即完成冷量从液化天然气301到空分设备的传输和转换。通过该封闭氮气循环可为精馏设备提供所需的大部或全部冷量。经低温氮压机的二段14压缩得到的封闭氮气循环中的氮气205的压力大于3.4MPa,即应超过氮气的临界压力。
该封闭氮气循环在封闭系统中工作,低温氮压机的一段13、低温氮压机的二段14的进出口管的合适位置可设置有碳氢化合物在线控制仪,可监测液化天然气301是否泄漏到该封闭氮气循环中。由于该封闭氮气循环与精馏装置也相对封闭,可以避免液化天然气301泄漏到精馏装置中而带来的危险,提高了安全性。
在上塔4的适当位置可抽出含氩较高的氩馏份117去制氩系统制得氩产品。
上述技术方案中所采用的低温氮压机为一台或两台无油润滑活塞式压缩机或透平压缩机。进入低温氮压机的一段13的进气氮气202、进入低温氮压机的二段14的进气氮气204的温度低于-70℃。
上述实施例只为说明本发明的技术构思及特点,其目的在于让熟悉此项技术的人士能够了解本发明的内容并据以实施,并不能以此限制本发明的保护范围。凡根据本发明精神实质所作的等效变化或修饰,都应涵盖在本发明的保护范围之内。
Claims (9)
1.一种空气分离方法,包括
经过压缩机压缩并在预冷系统中冷却、在净化系统中除去有害杂质的空气(101)由冷量交换而达到饱和温度或部分带液后,进入精馏塔参与精馏,
精馏塔包括上塔(4)、下塔(2)、主冷凝蒸发器(3),
在所述的上塔(4)的底部获得的液氧(116)经液空过冷器(6)后作为产品引出,在所述的上塔(4)的上部得到的纯气氮(114)、污气氮(115)经液氮过冷器(5)、液空过冷器(6)及主换热器(1)复热后推出,
由所述的下塔(2)的底部得到的富氧液空(106)经液空过冷器(6)被纯气氮(114)、污气氮(115)过冷后,经过节流膨胀进入所述的上塔(4)成为回流液,
由所述的下塔的顶部获得的一部分氮气(108)冷凝成液氮(118)后参与精馏或作为产品外供,
其特征在于:由所述的下塔(2)的顶部获得的另一部分氮气(109)参与氮气循环后回到所述的下塔(2)将冷量传递至所述的精馏塔中,
所述的氮气循环包括冷量源、将冷量源的冷量传递给由所述的下塔(2)的顶部获得的另一部分氮气(109)的封闭氮气循环,所述的冷量源为液化天然气(301),所述的封闭氮气循环中的氮气(205)在液化天然气换热器(11)中与液化天然气(301)进行热量交换后经过氮液化过冷器(12)冷却后成为液氮(206),经节流后得到的液氮(209)再经过氮冷凝蒸发器(7)与由所述的下塔(2)的顶部获得的另一部分氮气(109)进行热量交换,然后在主换热器(1)中被气化为氮气(201)后再转化为封闭氮气循环中的氮气(205),完成所述的封闭氮气循环;
所述的空气(101)分为两路,一路空气(102)在主换热器(1)中冷却降温后,进入精馏塔参与精馏,另一路空气(103)进入膨胀机的增压端(9)增压后通过水冷却器(10)冷却,再进入主换热器(1)中冷却到一定温度,然后进入膨胀机的膨胀端(8)膨胀,最后进入所述的上塔(4)的适当位置参与精馏。
2.根据权利要求1所述的一种空气分离方法,其特征在于:由所述的下塔(2)的顶部获得的一部分氮气(108)在主冷凝蒸发器(3)或在所述的氮冷凝蒸发器(7)中冷凝成液氮(108)。
3.根据权利要求1所述的一种空气分离方法,其特征在于:经过氮液化过冷器(12)冷却为的液氮(206)的一部分节流得到的液氮(208)经氮液化过冷器(12)复热后,再经液化天然气换热器(11)加热到规定温度后与在液化天然气换热器(11)中冷却到规定温度的氮气(201)汇合为进气氮气(202)后进入低温氮压机的一段(13)压缩,得到气氮(203),气氮(203)经液化天然气换热器(11)冷却后成为低温氮压机的二段的进气氮气(204)进入低温氮压机的二段(14)压缩。
4.根据权利要求3所述的一种空气分离方法,其特征在于:经过氮液化过冷器(12)冷却为的液氮(206)的一部分节流得到的液氮(207)经氮液化过冷器(12)复热后,再经液化天然气换热器(11)加热到规定温度后与氮气(203)汇合成进气氮气(204)后进入低温氮压机的二段(14)压缩,得到封闭氮气循环中的氮气(205)。
5.根据权利要求3所述的一种空气分离方法,其特征在于:所述的低温氮压机为无油润滑活塞式压缩机或透平压缩机,所述的低温氮压机为一台或两台。
6.根据权利要求3所述的一种空气分离方法,其特征在于:所述的进入低温氮压机的一段(13)的进气氮气(202)的温度低于-70℃。
7.根据权利要求3所述的一种空气分离方法,其特征在于:所述的进入低温氮压机的二段(14)的进气氮气(204)的温度低于-70℃。
8.根据权利要求1所述的一种空气分离方法,其特征在于:封闭氮气循环中的氮气(205)的压力大于3.4MPa。
9.根据权利要求3所述的一种空气分离方法,其特征在于:在所述的低温氮压机的一段(13)、低温氮压机的二段(14)的进出口管的合适位置设置有碳氢化合物在线控制仪。
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EP4343247A1 (de) * | 2022-09-23 | 2024-03-27 | Messer SE & Co. KGaA | Verfahren und vorrichtung zur herstellung von luftgasen |
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