CN1019689B - 大量回收氩和提取中压氮的空气分离方法和设备 - Google Patents

大量回收氩和提取中压氮的空气分离方法和设备

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CN1019689B
CN1019689B CN89102811A CN89102811A CN1019689B CN 1019689 B CN1019689 B CN 1019689B CN 89102811 A CN89102811 A CN 89102811A CN 89102811 A CN89102811 A CN 89102811A CN 1019689 B CN1019689 B CN 1019689B
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tower
oxygen
argon
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fluid
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丛海理
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Union Carbide Corp
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    • Y10S62/924—Argon

Abstract

本发明公开了一种在高于常规压力下大量回收氩，同时又生产氮的方法和装置，该装置包括三个塔，其中第一塔底部馏份被送到第二塔，第二塔底部馏份使第三塔的顶部冷凝器运行，含氩液体从第二塔中部位置送入第三塔中以便分离，第一塔底部馏份经第二塔中部某位置进入第二塔，第二塔底部馏份经其中部另一位置流出第二塔。

Description

本发明涉及低温精馏空气，尤其涉及从空气中分离出它的三种主要组份。
低温分离空气是通用的工业方法。低温分离方法包括：将送入的空气进行过滤，以去掉杂质;将清洁空气进行压缩，以提供分离所需要的能量;再对压缩后的空气进行冷却，以去掉沸点高的杂质，如二氧化碳和水蒸汽;然后通过低温精馏，将空气的各组份分离出来。在低温分离塔中，为了通过精馏分离空气，其气体和液体应进行必要的接触，分离出的产品通过与冷却空气流逆向流动其温度回升到环境温度。
如果在将空气分离成氮和氧的过程中还要回收氩，通常所采用的系统包括三个分离塔，其中，空气在前两个塔中分离出氮和氧，此两个塔一个是高压塔，另一个为低压塔。通常，上述两个塔因主冷凝器而呈换热关系，含氩气流从低压塔流到第三塔，以生产粗氩。在R.E.Latimer著的“Distillation    of    Air”，chemical    Engineering    progress，Volume    63，page    35-59（1967）中对此类常规方法已作了讨论。
这种常规的、从空气中分离出三种组份的方法通常适用于很多场合，但如果需要在高压下回收氮气，则有一个明显的缺点。对于空气的这三种组份，氮最易挥发，氩次之，氧挥发性最小。为了能够大量回收各种组份，低压塔要在尽可能低的压力下运行，一般约比大气压高13.79仟帕。这样的低压能够尽可能地增大氩和氧及氮和 氩之间的相对挥发性，因而能从空气中最大地分离出这三种组份。
如果希望氮处在中压状态，低压塔应在高于常规低压的压力下运行。这将导致氩的回收量明显地减少，因为在分离过程中有大量氩和氮排出，而不进到粗氩塔中。中压氮气用作保护气、压送剂（stirring）及提高油回收量其需求量越来越大。此外，因为早期为炼钢工业所建造的氧-氩空气分离装置的利用有所减少，增加氩和中压氮的产量就更重要了。
因此，非常希望能有一种在高于常规压力下生产氮同时又能大量回收氩的空气分离方法。
据此，本发明的任务在于提供一种生产中压氮气同时又能大量回收氩的方法和设备。
对于本领域的普通技术人员而言，在阅读了本发明所公开的文本后将会很清楚地理解本发明的上述目的和其它目的。本发明的内容之一是：
一种空气分离方法，它包括：
（A）将加工空气送入工作压力范围在绝对压力为413.7-2068.5仟帕的第一塔中，在上述第一塔中，加工空气被分离为含氮较多的馏分及含氧较多的馏分;
（B）将含氧较多的馏份和含氮较多的馏份从第一塔送到压力低于第一塔、压力范围在绝对压力为137.9-620.6仟帕的第二塔中，以便分离成富氮馏分和富氧馏分;
（C）回收富氮馏分作为中压氮产品;
（D）将含氩流体从第二塔的中部送进第三塔中，在第三塔中将含氩流体分离为含氩较多的蒸汽和含氧较多的液体;
（E）回收含氩较多的蒸汽中的第一部分作为粗氩产品;以及
（F）通过与富氧馏份进行间接热交换，使含氩较多的蒸汽中的第二部分冷凝，并将冷凝出的液体作为回流液体向下流到第三塔中。
本发明的另一部分内容是：
（A）带有加工空气引入装置的第一塔;
（B）带有流体回收装置的第二塔;
（C）将流体由第一塔送到第二塔的装置;
（D）将流体从第二塔中部位置送到第三塔的装置，在第三塔中装有顶部冷凝器和流体回收装置;以及
（E）将流体由第二塔下部送到第三塔的顶部冷凝器的装置。
在此使用的术语“塔”（Column）是指蒸馏塔（或段）或精馏塔（或段），即，一种接触塔或段，在其中，液相与汽相逆向接触，以有效地分离液体混合物。例如，通过一系列在塔中垂直放置的塔盘或塔板，或者在塔中充填填充元件，使液相和汽相相接触。有关蒸馏塔的进一步讨论请参见Chemical    Engineers′    Handbook，Fifth    Edition，edited    by    R.H.Perry    and    C.H.Chilton，McGraw-Hill    Book    Company，New    York，Section    13，“Distillation”B.D.Smith，et.al.，Page    13-3The    Continuous    Distillation    Process。术语“双塔”是指一个高压塔，其上部与低压塔下部呈换热关系。有关双塔的进一步论述可参见Ruheman“The    Separation    of    Gases”Oxford    University    Press，1949，Chapter    VII， Commercial    Air    Separation.
术语“间接热交换”意指两种流体流在彼此不接触或不混合的情况下进行热交换。
术语“再蒸发器”是指从塔底部液体中产生向塔上部流动的蒸汽的热交换装置。
此处所用的术语“冷凝器”是指从塔上部蒸汽中产生向下流的液体的热交换装置。
图1表示本发明的一个实施例的示意图，其中含氩流体以蒸汽的形式从第二塔流入第三塔中。
图2是本发明的另一个实施例的示意图，其中含氩流体以液体的形式从第二塔流入第三塔中。
下面结合附图对本发明的方法和设备进行详细说明。
参见图1，经冷却、清洁的加工空气10被送到压力范围在绝对压力为413.7-2068.5仟帕的第一塔1中，其较好的压力范围是绝压力为551.6-1034.3仟帕。在第一塔1中，加工空气被分离成含氮量较多的馏分和含氧量较多的馏分。含氧量较多的馏份通过管道21和阀门50进到第二塔2中。第二塔的工作压力低于第一塔1，其压力范围在绝压为137.9-620.6仟帕，较好的压力范围是137.9-413.7仟帕，最好在137.9-310.3仟帕的范围内。在图1所表示的实施例中，第一塔和第二塔因主冷凝器120而呈换热关系，因而构成双塔。在这样的安排中，含氮量较多的馏分11以蒸汽形式进到主冷凝器120中通过换热而被冷凝，同时使第二塔或低压塔2底部馏分再蒸发。也可以从塔截面处抽出馏分流11的一部分，一般少于15%作为回收的高压氮产品。被冷凝下来的含氮较多的馏分12中的一部分作为回流13 向下流入下塔1中，另一部分通过管道22和阀51进入塔2中。如需要，例如可以把来自透平膨胀机的、另外的加工空气蒸汽23加到第二塔2中。
在塔2中，含氮较多的馏分、含氧较多的馏分以及不是必须加入的空气蒸汽23被分离为富氮馏分和富氧馏分。压力与塔2工作压力大体相同、纯度至少为99.5%的富氮馏分25从塔2上部被回收。除非特别说明，此处所使用的百分数是指摩尔百分数。为了控制氮的纯度，还可从塔2中排出少量污氮流24。
含氩流体以蒸汽形式从塔2中部经管道30被送到第三塔3中，塔3有一个顶部冷凝器230，塔3的工作压力与塔2相同。含氩流体中氩的浓度一般为8%-20%，其剩余组份基本上是氧以及含0.1%或更少的氮。在塔3中，含氩流体被分离成含氩较多的蒸汽以及含氧较多的液体。含氩较多的蒸汽31的第一部分作为粗氩被回收，其浓度范围通常为95%-99.5%。含氩较多的蒸汽的第二部分33被通入顶部冷凝器230中，并被冷凝。所产生的液体34作为回流向下流到塔3中。含氧较多的液体作为流35从塔3底部流入塔2并向下流。
顶部冷凝器230蒸发来自低压塔2下部的富氧馏份。如图1所示，富氧馏份40以液体形式从塔2中抽出，通过阀52膨胀，然后进入顶部冷凝器230，在该冷凝器中蒸发，由于其压力较低，因而温度低于塔2底部温度，同时，冷凝含氩较多的蒸汽33。根据塔2底部液体和冷凝器230蒸发侧之间的压力差和高度差，利用液体泵100可使塔2底部压力增加。最好，流40中至少包括由该过程所生产的产品氧的80%。
所得到的蒸汽41从该过程中排出，并作为产品氧42而被回收。流40在蒸发前的氧纯度至少为99%，最好至少为99.5%。流41可方便地与由塔2抽出的、并流过阀53的氧流26汇合后一起被回收。氧流26用来控制该过程，常规情况下，它占产品氧42中的3%-10%，最好为5%。作为并非必需的措施，蒸汽流41在与流26汇合以前还可用来过冷通过阀52作液体膨胀之前的液流40。
本发明能够以流32的形式从加工空气中至少回收70%的氩，最多约能回收97%的氩，同时，在高于常规压力下得到高纯氮。由于本发明不是象常规方法那样用高压塔底部馏份而是用低压塔底部馏份使粗氩顶部冷凝器运行，因此可以得到非常好的效果。由于高压塔底部馏份不必用来使冷凝器230工作，就可以有比常规量多的流21流进低压塔，这有利于促使氩向下流向中部，从中部可抽出含氩流30。实际上，由于在塔2下段加入了向下流的液体，因而对回收氩产生了好的效果。
因此，尽管实际上低压塔的工作压力高于常规情况下的工作压力，因而相对挥发性减小，使氩更难于被分离出来，但由于本发明所用的部件可使氩从低压塔流出并流入第三塔中，且可从中收回粗氩，因此氩的产量仍很高。
以流10和可加可不加的流23送入这些塔中的加工空气通常70%以上作为高纯氮以流25被回收。通常，送入低压塔的蒸汽与液体之比，即，流23与21、22和35之和的摩尔比率小于0.35，最好在0-0.15的范围内。这可促使氩从低压塔顶部随氮向下流到塔的中部，从中部氩被送到粗氩塔中。
如前所述，图1为本发明的一个好的实施例，此例中含氩流体以蒸汽形式从第二塔流进第三塔。如果含氩流体以液体形式从第二塔流进第三塔，则图2所示的实施例是较好的实施例。图2中与图1通用的元件用同一标号，因此，下面仅对与上面所描述的实施例不同的地方进行详细讨论。
在图2所示的实施例中，第三塔3可以是而且最好是在低于低压塔2的压力下运行。含氩流体以液体形式经管道30和阀54进入第三塔中，在该塔中被分离成含氩较多的蒸汽和含氧较多的液体。塔3附加了底部再蒸发器130，其目的在于使塔底部馏份再蒸发，以产生向上流的蒸汽。通过含氮较多的馏份11的一部分14在再蒸发器130中冷凝，使再蒸发器130实现再蒸发。冷凝部分15与流12汇合，流15或者作为流22的一部分流回塔2中，或者作为流13的一部分流到塔1中。富氧馏分在进到顶部冷凝器230之前经过阀36作第一次膨胀。最后，富氧液体35由塔3底部抽出后不进到塔2中，而是送到阀36下游及泵100上游的富氧馏份流40中。
正如所看到的那样，在图2所示的、以液体形式送入的实施例中，尽管塔2是在高于常规压力的条件下运行，该实施例仍保留了本发明中将氩从塔2中抽出并送入塔3中去的基本部件。
表1中列出了本发明按图1所示实施例运行的计算机模拟结果。表1中流的标号与图1所示的各流相对应，除作特殊说明外，其流量以在常温常压下立方米/小时计，压力以绝对压力（仟帕）计，温度以开式温度（K）计，组成用摩尔百分比计。例如，进入塔2的蒸汽和液体的比率，也就是流23与流21、22和35之和的摩尔比率为0.065，氧回收率为99.9%，氮回收率为94.6%， 氩回收率为92.7%。表1中空白处说明该数据没有得到。
表1    组份
流的标号    流量    压力    温度    氧    氩    氮
10    2.62    812.9    109.3
23    0.207    209.6    95.3
加工空气    2.83    21.0    0.9    78.1
21    1.50    812.9
22    1.124    794.9    2ppm    189ppm    99.88
30    0.572    216.5    97.6    84.50    15.45    0.05
35    0.547    216.5    97.6
25    2.093    191.0    83.2    1ppm    ＞99.98
32    0.025    188.2    93.6    1.9    97.3    0.8
42    0.595    125.5    92.6    99.75    0.25    0
运用本发明，可以同时生产中压高纯氮，并能大量回收粗氩。
虽然通过两个较好的实施例对本发明进行了详细讨论，但本领域的技术人员通过其构思及权利要求的保护范围还应想象到本发明的其它实施例。

Claims (20)

1、一种空气分离方法，包括：
(A)将加工空气送入工作压力范围在绝对压力为413.7-2068.5仟帕的第一塔中，在上述第一塔中，加工空气被分离成含氮较多的馏分和含氧较多的馏分；
(B)将含氧较多的馏分和含氮较多的馏分从第一塔送至工作压力低于第一塔、压力范围在绝对压力为137.9-620.6仟帕的第二塔中，以便将它们分离成富氮馏分和富氧馏分；
(C)回收富氮馏分作为中压氮产品；
(D)从第二塔的中部抽出含氩流体并送入第三塔中，在第三塔中将该流体分离成含氩较多的蒸汽和含氧较多的液体；
(E)回收含氩较多的蒸汽的第一部分作为粗氩产品；以及
(F)通过与富氧馏分进行间接热交换，使含氩较多的蒸汽中的第二部分冷凝，并将冷凝出的液体作为回流液体向下流到第三塔中。
2、如权利要求1所述的方法，其特征在于冷凝来自第一塔的含氮较多的馏分，以便使富氧液体蒸发，冷凝后的含氮较多的馏分的第一部分送到第一塔，其第二部分送至第二塔。
3、如权利要求1所述的方法，其特征在于还包括将空气蒸汽送进第二塔中。
4、如权利要求1所述的方法，其特征在于送入第二塔的空气蒸汽与含氮较多和含氧较多的液体的摩尔比小于0.35。
5、如权利要求1所述的方法，其特征在于含氩流体以蒸汽的形式从第二塔进到第三塔中。
6、如权利要求5所述的方法，其特征在于还包括将富氧液体从第三塔下部通过第二塔中部位置进入第二塔中。
7、如权利要求1所述的方法，其特征在于含氩流体以液体的形式从第二塔进到第三塔中。
8、如权利要求7所述的方法，其特征在于第三塔工作压力低于第二塔的工作压力。
9、如权利要求7所述的方法，其特征在于还包括来自第三塔下部的富氧液体跟含氩较多的蒸汽呈换热关系。
10、如权利要求7所述的方法，其特征在于还包括通过间接热交换，将来自第一塔的含氮较多的馏分冷凝，而使第三塔底部的富氧液体再蒸发。
11、如权利要求1所述的方法，其特征在于还包括回收作为产品的氧。
12、如权利要求11所述的方法，其特征在于从用来冷凝含氩较多的蒸汽的富氧馏分中抽出产品氧。
13、如权利要求11所述的方法，其特征在于从第二塔中抽出产品氧。
14、如权利要求11所述的方法，其特征在于既从用来冷凝含氩较多的蒸汽的富氧馏分中抽出产品氧，也从第二塔中抽出产品氧。
15、空气分离装置，包括：
（A）带有加工空气引入装置的第一塔;
（B）带有流体回收装置的第二塔;
（C）将流体由第一塔送到第二塔的装置;
（D）将流体从第二塔中部位置送到状有顶部冷凝器和具有流体回收装置的第三塔的装置;以及
（E）将流体从第二塔下部送到第三塔的顶部冷凝器的装置。
16、如权利要求15所述的装置，其特征在于还包括一个位于第二塔下部的主冷凝器;将蒸汽从第一塔上部送到主冷凝器的装置;以及将液体从主冷凝器送到第一塔上部的装置。
17、如权利要求15所述的装置，其特征在于还包括将流体从第三塔下部经过第二塔中部位置送入第二塔的装置。
18、如权利要求15所述的装置，其特征在于还包括将流体从第三塔下部送到顶部冷凝器的装置。
19、如权利要求18所述的装置，其特征在于还包括一个位于第三塔下部的再蒸发器;将蒸汽从第一塔上部送到再蒸发器的装置;以及将液体从再蒸发器送到第一塔上部的装置。
20、如权利要求15所述的装置，其特征在于还包括将空气蒸汽引进第二塔的装置。
CN89102811A 1988-06-02 1989-03-31 大量回收氩和提取中压氮的空气分离方法和设备 Expired CN1019689B (zh)

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