CN203177588U - 低浓度煤层气含氧深冷液化制取天然气的装置 - Google Patents

低浓度煤层气含氧深冷液化制取天然气的装置 Download PDF

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CN203177588U
CN203177588U CN2013201678376U CN201320167837U CN203177588U CN 203177588 U CN203177588 U CN 203177588U CN 2013201678376 U CN2013201678376 U CN 2013201678376U CN 201320167837 U CN201320167837 U CN 201320167837U CN 203177588 U CN203177588 U CN 203177588U
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nitrogen
heat exchanger
azeotrope
outlet
gas
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姚成林
肖露
甘海龙
令狐磊
付耀国
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CCTEG Chongqing Research Institute Co Ltd
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CHINA COAL SCIENCE AND INDUSTRY GROUP CHONGQING RESEARCH INSTITUTE
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    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
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    • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
    • F25J2290/34—Details about subcooling of liquids

Abstract

本实用新型公开了一种低浓度煤层气含氧深冷液化制取天然气的装置，包括主流程系统和制冷系统；主流程系统包括一级换热器、二级换热器、三级换热器、过冷器和精馏塔，精馏塔塔内设置塔顶冷凝器和再沸器，精馏塔塔顶设置的氮氧气出口与塔顶冷凝器相连，精馏塔塔底设置冷凝液出口；制冷系统包括混合冷剂循环系统和氮循环系统；混合冷剂循环系统包括混合冷剂压缩机、混合冷剂冷却器和重烃分离器；重烃分离器的气相混合冷剂通过一级换热器和二级换热器连通于再沸器后再回流；重烃分离器的液相混合冷剂气相混合冷剂汇合后回流；氮循环系统包括氮压缩机和氮冷却器，氮冷却器依次通过一级换热器、二级换热器、三级换热器和过冷器连通于塔顶冷凝器后回流。

Description

低浓度煤层气含氧深冷液化制取天然气的装置
技术领域
本实用新型属于通过加压和冷却处理使气体或气体混合物进行液化、固化或分离的技术领域，具体的为一种低浓度煤层气含氧深冷液化制取天然气的装置。
背景技术
含氧煤层气是煤矿在开采过程中为防止瓦斯爆炸和突出，保证煤矿安全生产而抽排出的初级副产品，其主要成分为甲烷，从其成分含量上可以看出，煤层气是较为重要的能源和化工原料。但是由于其成分较为复杂，特别是在煤层气中含有氧，是非常危险的助燃助爆剂，制约了含氧煤层气的综合利用，实践中，为了节约成本，煤层气普遍在采煤过程中排入大气，造成资源的极度浪费和对环境造成污染。
随着技术的发展，目前在低浓度煤层气提纯制取天然气的领域中，出现了多种含氧煤层气的液化技术。公开号为CN101922850A和CN101929788A分别公开了一种利用含氧煤层气制取液化天然气的方法和利用含氧煤层气制取液化天然气的装置，该方法和装置采用混合冷剂自复叠制冷循环，将净化后的原料气液化并分离，得到LNG产品，该方法和装置虽然能够利用含氧煤层气制取天然气，但是还存在以下问题：
（1）原料气（即低浓度煤层气）来自于煤矿井下抽采，甲烷含量波动较大，难免会影响液化工艺的稳定运行，需要对装置进行调整；而该方法和装置中天然气产品的纯度和收率分别由塔底蒸发量和塔顶冷凝量控制，但为塔底加热和为塔顶冷却的制冷剂流体为同一股，因此在调整产品纯度时会影响塔顶冷凝量（收率），同样，调整产品收率时又会影响到塔底蒸发量（纯度）；
（2）如果冷剂压缩机工况不稳定，会导致大量混合冷剂中的重组分（如异丁烷、异戊烷）进入液化装置的低温区（温度低于－165℃），造成该段冷剂温度低于其下转化温度，使节流后温度升高（即不制冷），严重时亦会导致凝固，使冷剂通道堵塞；
（3）煤层气中甲烷被提出后，氮氧尾气在精馏塔的操作压力（0.3MPa）下直接复热排空，未充分回收其能量（压力能），浪费能源。
有鉴于此，本实用新型旨在探索一种低浓度煤层气含氧深冷液化制取天然气的装置，该低浓度煤层气含氧深冷液化制取天然气的装置不仅能够独立调整天然气产品的纯度和收率，而且能够防止冷剂通道堵塞，并提高提高能源利用。
发明内容
本实用新型的目的在于提供一种低浓度煤层气含氧深冷液化制取天然气的装置，该低浓度煤层气含氧深冷液化制取天然气的装置不仅能够独立调整天然气产品的纯度和收率，而且能够防止冷剂通道堵塞。
为实现上述技术目的，本实用新型提供如下技术方案：
一种低浓度煤层气含氧深冷液化制取天然气的装置，包括主流程系统和制冷系统；
所述主流程系统沿净化后的煤层气流动方向依次包括一级换热器、二级换热器、三级换热器、过冷器和精馏塔，所述精馏塔塔顶设置塔顶冷凝器，精馏塔塔内设置位于塔底的再沸器，所述精馏塔塔顶设置的氮氧气出口与所述塔顶冷凝器的氮氧气出口相连，且所述精馏塔的塔底设置冷凝液出口；
所述制冷系统包括混合冷剂循环系统和氮循环系统；
所述混合冷剂循环系统沿混合冷剂流动方向依次包括混合冷剂压缩机、混合冷剂冷却器和重烃分离器；所述重烃分离器的气相混合冷剂出口依次通过一级换热器和二级换热器连通于所述再沸器的气相混合冷剂入口，所述再沸器的气相混合冷剂出口依次通过三级换热器、二级换热器和一级换热器使气相混合冷剂回流并连通于所述混合冷剂压缩机的混合冷剂入口；所述重烃分离器的液相混合冷剂出口通过一级换热器后与回流的气相混合冷剂汇合；
所述氮循环系统沿氮冷却剂的流动方向依次包括氮压缩机和氮冷却器，所述氮冷却器的氮出口依次通过所述一级换热器、二级换热器、三级换热器和过冷器连通于所述塔顶冷凝器的氮入口，所述塔顶冷凝器的氮出口依次通过三级换热器、二级换热器和一级换热器使氮冷却剂回流并连通于所述氮压缩机的氮入口。
进一步，所述主流程系统还包括膨胀机，所述精馏塔的氮氧气出口通过所述过冷器连通于所述膨胀机的氮氧气入口，所述膨胀机的氮氧气出口依次通过过冷器、三级换热器、二级换热器和一级换热器使氮氧气复热后进入净化工序。
进一步，所述精馏塔的冷凝液出口通过所述三级换热器连通于天然气储罐。
进一步，所述混合冷剂冷却器和氮冷却器均为水冷却器。
进一步，所述混合冷剂循环系统还包括节流阀V1，所述重烃分离器的液相混合冷剂出口依次通过一级换热器和节流阀V1与回流的气相混合冷剂汇合。
进一步，所述再沸器的气相混合冷剂出口与所述三级换热器之间设有节流阀V2。
进一步，所述过冷器与塔顶冷凝器的氮入口之间设有节流阀V3。
进一步，所述过冷器的煤层气出口与精馏塔的煤层气入口之间设有节流阀Vf。
本实用新型的有益效果在于：
本实用新型的低浓度煤层气含氧深冷液化制取天然气的装置，通过将制冷系统设置为混合冷剂循环系统和氮循环系统，通过混合冷剂循环系统控制精馏塔的塔底蒸发量和通过氮循环系统控制精馏塔的塔顶冷凝量，能够独立调整天然气产品的纯度和收率，而且低温区的冷剂仅有氮组分，不存在异丁烷、异戊烷等重组分，从而解决节流不制冷，或冷剂通道堵塞问题。
通过膨胀机，使其在常温常压下排空，从而充分回收返流的氮氧气的能量，达到节能减排的目的。
附图说明
为了使本实用新型的目的、技术方案和有益效果更加清楚，本实用新型提供如下附图进行说明：
图1为本实用新型低浓度煤层气含氧深冷液化制取天然气的装置实施例的结构示意图。
具体实施方式
下面将结合附图，对本实用新型的优选实施例进行详细的描述。
如图1所示，为本实用新型低浓度煤层气含氧深冷液化制取天然气的装置实施例的结构示意图。本实施例的低浓度煤层气含氧深冷液化制取天然气的装置，包括主流程系统和制冷系统。
主流程系统沿净化后的煤层气流动方向依次包括一级换热器1、二级换热器2、三级换热器3、过冷器4和精馏塔5，精馏塔5塔顶设置塔顶冷凝器6，精馏塔5塔内设置位于塔底的再沸器7，精馏塔5塔顶设置的氮氧气出口与塔顶冷凝器6的氮氧气出口相连，且精馏塔5的塔底设置冷凝液出口，用于液态天然气流出。本实施例的过冷器4的煤层气出口与精馏塔5的煤层气入口之间设有节流阀Vf，能够对煤层气进行节流降温。
制冷系统包括混合冷剂循环系统和氮循环系统。混合冷剂循环系统沿混合冷剂流动方向依次包括混合冷剂压缩机8、混合冷剂冷却器9和重烃分离器10。重烃分离器10的气相混合冷剂出口依次通过一级换热器1和二级换热器2连通于再沸器7的气相混合冷剂入口，再沸器7的气相混合冷剂出口依次通过三级换热器3、二级换热器2和一级换热器1使气相混合冷剂回流并连通于混合冷剂压缩机8的混合冷剂入口，重烃分离器10的液相混合冷剂出口通过一级换热器1后与回流的气相混合冷剂汇合，液相混合冷剂与气相混合冷剂汇合后一起回流进入混合冷剂压缩机8，使混合冷剂能够循环利用。本实施例的混合冷剂循环系统还包括节流阀V1，重烃分离器10的液相混合冷剂出口依次通过一级换热器1和节流阀V1与回流的气相混合冷剂汇合，通过设置节流阀V1，能够对液相混合冷剂进行节流减压。本实施例的再沸器7的气相混合冷剂出口与三级换热器3之间设有节流阀V2，能够对气相混合冷剂进行节流降温。
氮循环系统沿氮冷却剂的流动方向依次包括氮压缩机11和氮冷却器12，氮冷却器12的氮出口依次通过一级换热器1、二级换热器2、三级换热器3和过冷器4连通于塔顶冷凝器6的氮入口，塔顶冷凝器6的氮出口依次通过三级换热器3、二级换热器2和一级换热器1使氮冷却剂回流并连通于氮压缩机11的氮入口，使氮能够循环利用，并对塔顶冷凝器6提供冷量。本实施例的过冷器4与塔顶冷凝器6的氮入口之间设有节流阀V3，能够对氮冷却剂进行降温。
本实施例的低浓度煤层气含氧深冷液化制取天然气的装置，通过将制冷系统设置为混合冷剂循环系统和氮循环系统，通过混合冷剂循环系统控制精馏塔5的塔底蒸发量和通过氮循环系统控制精馏塔5的塔顶冷凝量，能够独立调整天然气产品的纯度和收率，而且低温区的冷剂仅有氮组分，不存在异丁烷、异戊烷等重组分，从而解决节流不制冷，或冷剂通道堵塞问题。
进一步，主流程系统还包括膨胀机13，精馏塔5的氮氧气出口通过过冷器4连通于膨胀机13的氮氧气入口，膨胀机13的氮氧气出口依次通过过冷器4、三级换热器3、二级换热器2和一级换热器1使氮氧气复热后进入净化工序。通过设置膨胀机13，使其在常温常压下排空，从而充分回收返流的氮氧气的能量，达到节能减排的目的。
进一步，本实施例的精馏塔5的冷凝液出口通过三级换热器3连通于天然气储罐，使天然气产品达到过冷状态，便于储存。
进一步，本实施例的混合冷剂冷却器9和氮冷却器12均为水冷却器，能够满足混合冷剂和氮冷却剂的冷却需求，并将其冷却至设定温度。
采用本实施例低浓度煤层气含氧深冷液化制取天然气的装置生产天然气的工艺流程如下：
采用本实施例低浓度煤层气含氧深冷液化制取天然气的装置生产天然气的工艺方法如下：
1）压缩净化工序：将低浓度含氧煤层原料气经压缩净化后得到净化含氧煤层气，本实施例经压缩净化工序得到的净化含氧煤层气的温度为40℃、绝对压强为0.42MPa。
2）液化分离工序：包括主流程工艺和制冷工艺。
a．主流程工艺：
a1．将净化含氧煤层气依次通过一级换热器1、二级换热器2、三级换热器3和过冷器4换热制冷，并经过节流阀Vf节流后形成冷凝液和气体的混合物；
a2．净化含氧煤层气从精馏塔5的中部进入精馏塔5，冷凝液向下流向塔底，并向上挥发携带的少量氮氧尾气，通过再沸器7加热后从冷凝液出口流出，且在冷凝液出口得到温度为-143.5℃、绝对压力为0.32~0.36MPa、甲烷浓度大于等于99%的液化天然气，该液化天然气通过三级换热器3换热并达到温度为-155~160℃，压力为0.243MPa的过冷状态后带压存储，得到成品天然气；
a3．精馏塔5的塔顶得到氮氧尾气经塔顶冷凝器6析出携带的少量甲烷组分后，再经过冷器4复热后进入膨胀机13膨胀，膨胀至0.15~0.18MPa后的氮氧尾气依次通过过冷器4、三级换热器3、二级换热器2和一级换热器1复热至常温后作为压缩净化工序的再生气。
b．制冷工艺：包括混合冷剂工艺和氮冷剂工艺。
b1．混合冷剂工艺：混合冷剂的初始压强为0.26MPa，经混合冷剂压缩机8压缩至3.2-3.8Mpa，冷却后进入重烃分离器10分离为气液两相；其中气相混合冷剂依次通过一级换热器1和二级换热器2降温至-120℃后，进入位于精馏塔5塔底的再沸器7加热塔底液化天然气，自身被冷却至-148℃，节流后将温度为-160℃的气相混合冷剂依次通过三级换热器3、二级换热器2和一级换热器1输出冷量并循环回流至混合冷剂压缩机8循环利用；液相混合冷剂通过一级换热器1冷却至-50℃，并节流后与回流的气相混合冷剂汇合经一级换热器1一起回流至混合冷剂压缩机8循环利用，能够满足液化天然气的制取要求，并控制精馏塔5的塔底蒸发量。
b2．氮冷剂工艺：氮冷剂的初始压强为0.35MPa，经氮压缩机11压缩至3.2~3.5MPa，冷却后依次通过一级换热器1、二级换热器2、三级换热器3和过冷器4冷却至-172℃，经节流后氮冷剂的温度为-182℃、绝对压强为0.4MPa，进入塔顶冷凝器6输出冷量，然后将气态的氮冷剂依次通过过冷器4、三级换热器3、二级换热器2、一级换热器1逐级升温至常温后回流至氮压缩机11循环利用，能够满足液化天然气的制取要求，并控制精馏塔5的塔顶冷凝量。
进一步，本实施例的混合冷剂为氮气、甲烷、乙烯、丙烷、异戊烷的混合物，能够满足在液化天然气制取的各个环节中的温度控制要求，当然，混合冷剂还可采用其他组分的混合物，不再累述。
最后说明的是，以上优选实施例仅用以说明本实用新型的技术方案而非限制，尽管通过上述优选实施例已经对本实用新型进行了详细的描述，但本领域技术人员应当理解，可以在形式上和细节上对其作出各种各样的改变，而不偏离本实用新型权利要求书所限定的范围。

Claims (8)

1.一种低浓度煤层气含氧深冷液化制取天然气的装置，其特征在于：包括主流程系统和制冷系统；
所述主流程系统沿净化后的煤层气流动方向依次包括一级换热器、二级换热器、三级换热器、过冷器和精馏塔，所述精馏塔塔顶设置塔顶冷凝器，精馏塔塔内设置位于塔底的再沸器，所述精馏塔塔顶设置的氮氧气出口与所述塔顶冷凝器的氮氧气出口相连，且所述精馏塔的塔底设置冷凝液出口；
所述制冷系统包括混合冷剂循环系统和氮循环系统；
所述混合冷剂循环系统沿混合冷剂流动方向依次包括混合冷剂压缩机、混合冷剂冷却器和重烃分离器；所述重烃分离器的气相混合冷剂出口依次通过一级换热器和二级换热器连通于所述再沸器的气相混合冷剂入口，所述再沸器的气相混合冷剂出口依次通过三级换热器、二级换热器和一级换热器使气相混合冷剂回流并连通于所述混合冷剂压缩机的混合冷剂入口；所述重烃分离器的液相混合冷剂出口通过一级换热器后与回流的气相混合冷剂汇合；
所述氮循环系统沿氮冷却剂的流动方向依次包括氮压缩机和氮冷却器，所述氮冷却器的氮出口依次通过所述一级换热器、二级换热器、三级换热器和过冷器连通于所述塔顶冷凝器的氮入口，所述塔顶冷凝器的氮出口依次通过三级换热器、二级换热器和一级换热器使氮冷却剂回流并连通于所述氮压缩机的氮入口。
2.根据权利要求1所述的低浓度煤层气含氧深冷液化制取天然气的装置，其特征在于：所述主流程系统还包括膨胀机，所述精馏塔的氮氧气出口通过所述过冷器连通于所述膨胀机的氮氧气入口，所述膨胀机的氮氧气出口依次通过过冷器、三级换热器、二级换热器和一级换热器使氮氧气复热后进入净化工序。
3.根据权利要求1或2所述的低浓度煤层气含氧深冷液化制取天然气的装置，其特征在于：所述精馏塔的冷凝液出口通过所述三级换热器连通于天然气储罐。
4.根据权利要求3所述的低浓度煤层气含氧深冷液化制取天然气的装置，其特征在于：所述混合冷剂冷却器和氮冷却器均为水冷却器。
5.根据权利要求1所述的低浓度煤层气含氧深冷液化制取天然气的装置，其特征在于：所述混合冷剂循环系统还包括节流阀V1，所述重烃分离器的液相混合冷剂出口依次通过一级换热器和节流阀V1与回流的气相混合冷剂汇合。
6.根据权利要求5所述的低浓度煤层气含氧深冷液化制取天然气的装置，其特征在于：所述再沸器的气相混合冷剂出口与所述三级换热器之间设有节流阀V2。
7.根据权利要求6所述的低浓度煤层气含氧深冷液化制取天然气的装置，其特征在于：所述过冷器与塔顶冷凝器的氮入口之间设有节流阀V3。
8.根据权利要求7所述的低浓度煤层气含氧深冷液化制取天然气的装置，其特征在于：所述过冷器的煤层气出口与精馏塔的煤层气入口之间设有节流阀Vf。
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104610032A (zh) * 2014-12-26 2015-05-13 浙江大学 一种丁辛醇尾气回收装置及其方法
CN104610032B (zh) * 2014-12-26 2016-09-14 浙江大学 一种丁辛醇尾气回收装置及其方法

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