CN108007068A - 一种lng冷能利用的热集成精馏空分*** - Google Patents
一种lng冷能利用的热集成精馏空分*** Download PDFInfo
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- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims abstract description 21
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 190
- 229910052757 nitrogen Inorganic materials 0.000 claims description 91
- 239000007788 liquid Substances 0.000 claims description 54
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 29
- 238000003860 storage Methods 0.000 claims description 16
- 239000002808 molecular sieve Substances 0.000 claims description 15
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 15
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- 206010058490 Hyperoxia Diseases 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
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Abstract
本发明公开了一种LNG冷能利用的热集成精馏空分***,采用LNG冷能冷却原料低压空气,并利用热集成精馏塔进行空气分离,相较于传统空分***,本发明采用热集成精馏***可将原料空气的压力由0.6MPa降到0.4MPa,降低了总压比,减少了空压机耗功;采用LNG冷却原料空气,可使得空压机耗功进一步降低,液氧产量得到提高,从而降低了单位液体产品能耗;热集成精馏还可降低高压塔精馏和低压塔提馏过程的火用损失,提高氧氮的分离纯度;此外,采用LNG冷却原料空气,可以大幅度降低空分***启动时间。
Description
技术领域
本发明属于空气分离领域,涉及一种热集成精馏空分***,尤其涉及一种LNG冷能利用的热集成精馏空分***。
背景技术
空气分离***在钢铁、化工、半导体、食品加工以及医疗领域都具有很重要的作用。低温精馏空分***是实现大规模制取高纯度氮气、氧气以及氩气的主要方案。低温精馏空分***需要消耗大量能量,尤其是制取液氧与液氮的产品过程中。液化天然气(LNG)是采用深冷工艺将天然气液化得到的低温(约111K)混合液体,其主要成分为甲烷(CH4),具有燃烧热值高、排放物污染小、储运成本低等优点。LNG冷能不仅数量巨大,而且能量品阶高,常见的运用主要包括直接发电、空气液化分离、制取液化干冰、深冷粉碎以及低温冷库等。考虑到空分***的工艺温度约为78~100K,比LNG的温度更低,可避免“低温冷能高温用”的情况,符合“温度对口、梯级利用”能的高效利用原理,因此这种冷能利用方案也被认为是目前技术上最为合理的利用方式。
现有的LNG冷能利用空气分离***的节能效果主要可归为以下两种因素:(1)LNG冷能冷却空压机或氮压机进口工质温度,可使得空分***对电力能耗的需求降低;(2)LNG冷能可代替进入主换热器高纯度的液氧/液氮的释冷量实现原料空气温度的降低,减少额外的制取低温液体产品冷量所需的电力能耗。经过相关文献与专利计算,与常规空分***相比,采用LNG冷能的空分***制取单位液体产品的能耗可降低50%左右。
然而,现有LNG冷能利用的空分***方案其精馏塔运行压力都接近于0.6MPa,冷能的加入只是减少生产液体产品能耗而对空分***分离功无任何有益影响。产生这一现象的主要有2个原因:(1)传统空分***其精馏单元都采用双级精馏塔,通过低压液氧与高压氮气换热实现上塔与下塔回流气液,由于同一压力下氮气的沸点远低于氧气沸点,因此,下精馏塔需要在高压运行;(2)双级精馏塔的工作温度为78~100K,LNG的储存温度为112K,如若LNG冷能作用于精馏过程,仍需要对原料空气进行增压,通过膨胀或节流产生更低工作温度。调节上述两个原因的方法只有通过改变传统的双级精馏冷热耦合方式,降低精馏塔压力,将部分LNG冷能转为分离功,实现LNG冷能利用的空分***能耗进一步降低。
发明内容
针对现有技术的缺点和不足,本发明旨在提供一种LNG冷能利用的热集成精馏空分***,采用LNG冷能冷却原料低压空气,并利用热集成精馏塔进行空气分离,相较于传统空分***,本发明采用热集成精馏***可将原料空气的压力由0.6MPa降到0.4MPa,降低了总压比,减少了空压机耗功;采用LNG冷却原料空气,可使得空压机耗功进一步降低,液氧产量得到提高,从而降低了单位液体产品能耗;热集成精馏还可降低高压塔精馏和低压塔提馏过程的火用损失,提高氧氮的分离纯度;此外,采用LNG冷却原料空气,可以大幅度降低空分***启动时间。
本发明为解决其技术问题所采用的技术方案为:
一种LNG冷能利用的热集成精馏空分***,包括风扇、水冷塔、分子筛、预冷器、空压机、主换热器、过冷器Ⅰ、高压塔、热集成单元、低压塔、过冷器Ⅱ、LNG存储装置、低温泵,其特征在于,
所述预冷器包括空气通路和天然气通路;
所述主换热器包括空气通路、LNG通路、氮气通路和污氮通路;
所述过冷器Ⅰ包括空气通路、污氮通路和氮气通路;
所述高压塔在高度方向上交错布置有塔板,底部设有低温空气进口和液态空气出口,顶部设有液氮出口;
所述低压塔在高度方向上交错布置有塔板,底部设有液氧出口,上部设有液态空气进口、液氮进口、纯氮气出口和污氮出口;
所述过冷器Ⅱ包括液态空气通路、氮气通路、污氮通路和液氮通路,
其中,
所述LNG存储装置的出口通过管路依次经低温泵、主换热器的LNG通路与所述预冷器的天然气通路进口连通;
所述风扇机的进气口与外界空气连通,所述风扇的出气口通过管路依次经所述水冷塔、分子筛、预冷器的空气通路、主换热器的空气通路、过冷器Ⅰ的空气通路与所述高压塔底部的空气进口连通;
所述高压塔底部的液态空气出口通过管路经所述过冷器Ⅱ的液态空气通路与所述低压塔上部设置的液态空气进口连通,所述高压塔顶部的液氮出口通过管路经所述过冷器Ⅱ的液氮通路与低压塔上部设置的液氮进口连通;
所述高压塔的精馏段与低压塔的提馏段位于同一高度,二者之间直接接触换热或通过换热器换热;
所述低压塔上部的纯氮气出口通过管路依次经所述过冷器Ⅱ的氮气通路、过冷器Ⅰ的氮气通路Ⅰ、主换热器的氮气通路的入口连通,
所述低压塔上部的污氮出口通过管路依次经过冷器Ⅱ的污氮通路、过冷器Ⅰ的污氮通路、主换热器的污氮通路的入口连通。
优选地,所述预冷器的天然气通路出口通过管路与天然气存储或利用装置连通。
进一步地,所述高压塔的精馏段与低压塔的提馏段之间设置由多个并列布置的换热器组成的换热集成单元,所述高压塔精馏段的的热量通过换热集成单元向所述低压塔提馏段传递。
进一步地,所述低压塔的提馏段嵌套在所述高压塔的精馏段内,所述高压塔精馏段的的热量直接向所述低压塔提馏段传递。
优选地,所述低压塔底部的液氧出口通过管路与液氧存储或利用装置的入口连通。
优选地,所述主换热器的氮气通路的出口与氮气存储或利用装置的入口连通。
优选地,所述主换热器的污氮通路的出口与所述分子筛的空气冷却***连通。
优选地,所述低压塔上部的液态空气进口处、液氮进口处均设置有控制阀门。
优选地,所述空压机的出口压力为0.4MPa左右。
优选地,经所述预冷器、主换热器和过冷器Ⅰ依次冷却后的空气被冷却至接近泡点温度送入所述高压塔的底部。
本发明的LNG冷能利用的热集成精馏空分***,主要利用LNG冷能冷却原料高压空气,并采用热集成精馏塔进行空气分离,其具体工作过程为:
空气首先由风扇升压并经过水冷塔降温,所提升压力用于弥补分子筛除水分和二氧化碳等杂质时压力损失,经分子筛除杂后的空气进入预冷器与LNG换热吸收部分冷能,在空压机中继续增压到.MPa,此时空压机的出口空气温度接近环境温度;带压空气进入主换热器、过冷器Ⅰ被LNG与返流氮气与污氮冷却至接近泡点温度送入高压塔的底部,在高压塔内,上升的空气与回流液氮在塔板反复冷凝蒸发,使得含氧浓度较高的富氧液体空气在高压塔底部集中,高纯液氮在高压塔顶部集中;高压塔顶部与底部抽出的液氮与富氧液体空气经过冷器Ⅱ后,进入低压塔参与精馏过程;高压塔精馏段的热量向低压塔提馏段通过由多个并列布置的换热器组成的换热集成单元进行热量传递,促进高压塔各塔板产生更多的冷凝液体,低压塔各塔板产生更多的蒸发气体;低压塔底部的液氧直接作为产品输出(存储在液氧存储装置中),顶部的纯氮气经过冷器Ⅱ、过冷器Ⅰ、主换热器复温后作为氮气产品输出,污氮经过冷器Ⅱ、过冷器Ⅰ、主换热器复温后送至分子筛的空气冷却***。
相较于现有技术的传统空分***,本发明LNG冷能利用的热集成精馏空分***,采用热集成精馏***可将原料空气的压力由0.6MPa降到0.4MPa,降低了总压比,减少了空压机耗功;采用LNG冷却原料空气,可使得空压机耗功进一步降低,液氧产量得到提高,从而降低了单位液体产品能耗;热集成精馏可降低高压塔精馏和低压塔提馏过程的火用损失,提高氧氮的分离纯度。此外,本发明采用LNG冷却原料空气,还可以大幅度降低空分***启动时间。
附图说明
图1为本发明的LNG冷能利用的热集成精馏空分***示意图;
图2为实施例2中所采用的套管式精馏装置。
具体实施方式
为使本发明的目的、技术方案及优点更加清楚明白,以下参照附图并举实施例,对本发明进一步详细说明。需要说明的是,以下所述仅为本发明的较佳实施例,并不因此而限定本发明的保护范围。
实施例1
如图1所示,本发明的LNG冷能利用的热集成精馏空分***,包括风扇1、水冷塔2、分子筛3、预冷器4、空压机5、主换热器6、过冷器Ⅰ7、高压塔8、热集成单元9、低压塔10、过冷器Ⅱ11、液氧存储或利用装置12、LNG存储装置13、低温泵14。其中,预冷器4包括空气通路和天然气通路;主换热器6包括空气通路、LNG通路、氮气通路和污氮通路;过冷器Ⅰ7包括空气通路、污氮通路和氮气通路;高压塔8在高度方向上交错布置有塔板,底部设有低温空气进口和液态空气出口,顶部设有液氮出口;低压塔10在高度方向上交错布置有塔板,底部设有液氧出口,上部设有液态空气进口、液氮进口、纯氮气出口和污氮出口;过冷器Ⅱ11包括液态空气通路、氮气通路、污氮通路和液氮通路。
LNG存储装置13的出口通过管路依次经低温泵14、主换热器6的LNG通路与预冷器4的天然气通路进口连通,预冷器4的天然气通路出口通过管路与天然气存储或利用装置(图中未示出)连通。风扇机1的进气口与外界空气连通,风扇1的出气口通过管路依次经水冷塔2、分子筛3、预冷器4的空气通路、主换热器6的空气通路、过冷器Ⅰ7的空气通路与高压塔8底部的空气进口连通;高压塔8底部的液态空气出口通过管路经过冷器Ⅱ11的液态空气通路与低压塔10上部设置的液态空气进口连通,高压塔8顶部的液氮出口通过管路经过冷器Ⅱ11的液氮通路与低压塔10上部设置的液氮进口连通;高压塔8的精馏段与低压塔10的提馏段位于同一高度,二者之间设置由多个并列布置的换热器组成的换热集成单元9,高压塔8精馏段的的热量通过换热集成单元9向低压塔10提馏段传递;低压塔10底部的液氧出口通过管路与液氧存储装置12的入口连通;低压塔10上部的纯氮气出口通过管路依次经过冷器Ⅱ11的氮气通路、过冷器Ⅰ7的氮气通路Ⅰ、主换热器6的氮气通路与氮气存储或利用装置(图中未示出)的入口连通,低压塔10上部的污氮出口通过管路依次经过冷器Ⅱ11的污氮通路、过冷器Ⅰ7的污氮通路、主换热器6的污氮通路与分子筛3的空气冷却***连通。
本发明的LNG冷能利用的热集成精馏空分***,主要利用LNG冷能冷却原料高压空气,并采用热集成精馏塔进行空气分离,其具体工作过程为:
空气首先由风扇1升压并经过水冷塔3降温,所提升压力用于弥补分子筛3除水分和二氧化碳等杂质时压力损失,经分子筛3除杂后的空气进入预冷器4与LNG换热吸收部分冷能,在空压机5中继续增压到0.4MPa,此时空压机5的出口空气温度接近环境温度;带压空气进入主换热器6、过冷器Ⅰ7被LNG与返流氮气与污氮冷却至接近泡点温度送入高压塔8的底部,在高压塔8内,上升的空气与回流液氮在塔板反复冷凝蒸发,使得含氧浓度较高的富氧液体空气在高压塔8底部集中,高纯液氮在高压塔8顶部集中;高压塔8顶部与底部抽出的液氮与富氧液体空气经过冷器Ⅱ11后,进入低压塔10参与精馏过程;高压塔8精馏段的热量向低压塔10提馏段通过由多个并列布置的换热器组成的换热集成单元9进行热量传递,促进高压塔8各塔板产生更多的冷凝液体,低压塔10各塔板产生更多的蒸发气体;低压塔10底部的液氧直接作为产品输出(存储在液氧存储装置12中),顶部的纯氮气经过冷器Ⅱ11、过冷器Ⅰ7、主换热器6复温后作为氮气产品输出,污氮经过冷器Ⅱ11、过冷器Ⅰ7、主换热器6复温后送至分子筛3的空气冷却***。
实施例2
同实施例1的不同之处在于,如图2所示,实施例2中的高压塔8和低压塔10集成在一起形成为套管式精馏装置,低压塔10的提馏段嵌套在高压塔8的精馏段内,二者之间直接换热。除此之外,实施例2中其他各部件之间的连接关系同实施例1保持一致。
相较于现有技术的传统空分***,本发明LNG冷能利用的热集成精馏空分***,采用热集成精馏***可将原料空气的压力由0.6MPa降到0.4MPa,降低了总压比,减少了空压机耗功;采用LNG冷却原料空气,可使得空压机耗功进一步降低,液氧产量得到提高,从而降低了单位液体产品能耗;热集成精馏可降低高压塔精馏和低压塔提馏过程的火用损失,提高氧氮的分离纯度。此外,本发明采用LNG冷却原料空气,还可以大幅度降低空分***启动时间。
以上显示和描述了本发明的基本原理、主要特征和优点。本行业的技术人员应该了解,本发明不受上述实施例的限制,上述实施例和说明书中描述的只是说明本发明的原理,在不脱离本发明精神和范围的前提下,本发明还会有各种变化和改进,这些变化和改进都落入要求保护的本发明范围内。本发明要求保护范围由所附的权利要求书及其等效物界定。
Claims (10)
1.一种LNG冷能利用的热集成精馏空分***,包括风扇、水冷塔、分子筛、预冷器、空压机、主换热器、过冷器Ⅰ、高压塔、热集成单元、低压塔、过冷器Ⅱ、LNG存储装置、低温泵,其特征在于,
所述预冷器包括空气通路和天然气通路;
所述主换热器包括空气通路、LNG通路、氮气通路和污氮通路;
所述过冷器Ⅰ包括空气通路、污氮通路和氮气通路;
所述高压塔在高度方向上交错布置有塔板,底部设有低温空气进口和液态空气出口,顶部设有液氮出口;
所述低压塔在高度方向上交错布置有塔板,底部设有液氧出口,上部设有液态空气进口、液氮进口、纯氮气出口和污氮出口;
所述过冷器Ⅱ包括液态空气通路、氮气通路、污氮通路和液氮通路,
其中,
所述LNG存储装置的出口通过管路依次经低温泵、主换热器的LNG通路与所述预冷器的天然气通路进口连通;
所述风扇机的进气口与外界空气连通,所述风扇的出气口通过管路依次经所述水冷塔、分子筛、预冷器的空气通路、主换热器的空气通路、过冷器Ⅰ的空气通路与所述高压塔底部的空气进口连通;
所述高压塔底部的液态空气出口通过管路经所述过冷器Ⅱ的液态空气通路与所述低压塔上部设置的液态空气进口连通,所述高压塔顶部的液氮出口通过管路经所述过冷器Ⅱ的液氮通路与低压塔上部设置的液氮进口连通;
所述高压塔的精馏段与低压塔的提馏段位于同一高度,二者之间直接接触换热或通过换热器换热;
所述低压塔上部的纯氮气出口通过管路依次经所述过冷器Ⅱ的氮气通路、过冷器Ⅰ的氮气通路Ⅰ、主换热器的氮气通路的入口连通,
所述低压塔上部的污氮出口通过管路依次经过冷器Ⅱ的污氮通路、过冷器Ⅰ的污氮通路、主换热器的污氮通路的入口连通。
2.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,所述预冷器的天然气通路出口通过管路与天然气存储或利用装置连通。
3.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,所述高压塔的精馏段与低压塔的提馏段之间设置由多个并列布置的换热器组成的换热集成单元,所述高压塔精馏段的的热量通过换热集成单元向所述低压塔提馏段传递。
4.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,所述低压塔的提馏段嵌套在所述高压塔的精馏段内,所述高压塔精馏段的的热量直接向所述低压塔提馏段传递。
5.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,所述低压塔底部的液氧出口通过管路与液氧存储或利用装置的入口连通。
6.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,所述主换热器的氮气通路的出口与氮气存储或利用装置的入口连通。
7.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,所述主换热器的污氮通路的出口与所述分子筛的空气冷却***连通。
8.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,所述低压塔上部的液态空气进口处、液氮进口处均设置有控制阀门。
9.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,所述空压机的出口压力为0.4MPa左右。
10.根据上述权利要求所述的LNG冷能利用的热集成精馏空分***,其特征在于,经所述预冷器、主换热器和过冷器Ⅰ依次冷却后的空气被冷却至接近泡点温度送入所述高压塔的底部。
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