CN111765719A - 一种膨胀制冷生产乙烷的方法及装置 - Google Patents

一种膨胀制冷生产乙烷的方法及装置 Download PDF

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CN111765719A
CN111765719A CN201910259441.6A CN201910259441A CN111765719A CN 111765719 A CN111765719 A CN 111765719A CN 201910259441 A CN201910259441 A CN 201910259441A CN 111765719 A CN111765719 A CN 111765719A
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demethanizer
ethane
gas
cold box
expansion
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王铁军
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Tianjin Branch Company China Petroleum Pipeline Engineering Co ltd
Tianjin Zhongyou Keyuan Petroleum Engineering Co ltd
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Tianjin Branch Company China Petroleum Pipeline Engineering Co ltd
Tianjin Zhongyou Keyuan Petroleum Engineering Co ltd
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Abstract

本发明公开了一种膨胀制冷生产乙烷的方法及装置，该方法包括第一步，天然气经冷箱预冷到‑30℃至‑80℃后,进入低温分离器分为气、液两相：第二步，液相进入冷箱复热后回流进入脱甲烷塔中部；第三步，气相分为两部分，一部分气相进入冷箱过冷液化后作为脱甲烷塔顶的回流液；第四步，另一部分气相进入压缩膨胀机膨胀端膨胀后回流到脱甲烷塔；第五步，同时外输干气气相经过回流复热后进入脱甲烷塔塔顶，脱甲烷塔底泵，将脱甲烷塔底部抽出，并通过冷箱调温后注入脱乙烷塔，本发明采用膨胀制冷生产乙烷，可有效利用装置冷热量平衡，提高了脱甲烷塔运行压力和运行温度，有效解决二氧化碳低温冰堵问题，并使乙烷回收率可达到95％以上。

Description

一种膨胀制冷生产乙烷的方法及装置
技术领域
本发明涉及天然气领域，尤其是天然气冷凝分离领域，具体为一种膨胀制冷生产乙烷的方法以及装置。
背景技术
目前，鉴于多数天然气中丰富的烃资源,天然气在外输之前都有必要提取乙烷、液化石油气及轻烃资源，同时天然气中丰富的乙烷资源,作为裂解乙烯的最佳原料,市场需求量大,前景较好,能够有效节约原油消耗,间接实现以气代油，目前天然气乙烷回收工艺主要有低温油吸收法、液相过冷法等，低温油吸收法需要大量的循环溶剂油,且溶剂油有一定的损耗,乙烷收率较低,一般只有80％的乙烷收率，液相过冷法仅有液相回流，过冷能力低，乙烷回收率低，能耗大，已有技术的大部分天然气处理厂轻烃回收装置的乙烷回收率仅为80％,回收深度仅为满足外输气烃露点要求,因此还有大部分烃组分未回收利用。
发明内容
本发明所要解决的主要技术问题是，本发明提供一种膨胀制冷生产乙烷的方法及装置，采用“多元混合制冷加气气液过冷”方式，可合理匹配不同温位的制冷负荷，提高了脱甲烷塔运行压力和运行温度，有效解决二氧化碳低温冰堵问题，并使乙烷回收率可达到95％以上，C3+回收率可达到99％以上。
为解决上述技术问题，本发明所采用的技术方案是：
一种膨胀制冷生产乙烷的方法，该方法经过预处理后的干天然气，1.0至8.0MPa.g，进入做为液烃回收装置的冷箱，经过冷箱预冷至-30至-80℃后进入低温分离器分为气、液两相；液相进入冷箱冷却后回流进入脱甲烷塔中部；气相分为两部分，一部分气相进入冷箱过冷液化后作为脱甲烷塔顶的回流液；另一部分气相进入压缩膨胀机膨胀端膨胀至1.0至4.0MPa.g后进入脱甲烷塔中部。脱甲烷塔底液进入脱乙烷塔脱乙烷，脱乙烷塔塔顶气即为产品气。
针对原料天然气中二氧化碳含量较高的气质特点，采用了“多元混合冷剂加气气液过冷”组合制冷工艺，合理匹配不同温位的制冷负荷，提高了脱甲烷塔运行压力和运行温度，有效解决二氧化碳低温冰堵问题。
针对原料天然气中C2+含量较低的气质特点，采用了“多元混合冷剂加气气液过冷回流”的C2+回收工艺，使乙烷回收率可达到95％以上，C3+回收率可达到99％以上。
选用了多股流板翅式冷箱，最小夹点温度接近1至6℃，对数平均温差较低，技术成熟可靠，换热效率高，降低了制冷系统负荷。
采用了引进的带同轴增压的压缩膨胀机制冷技术，机械效率高，运行稳定可靠，降低了贫气增压功率。
采用了脱甲烷塔侧线引出技术，充分利用脱甲烷塔物料的低温冷量，降低了装置制冷负荷，能量利用效率高，节能效果明显。
本发明的多元混合制冷剂可采用甲烷、乙烷、丙烷、乙烯、氮气、正丁烷、正戊烷、异丁烷、异戊烷中任意四种或者任意五种组分的组合作为制冷剂配方。
本发明还提供一种膨胀制冷生产乙烷的装置，包括冷箱、压缩膨胀机、低温分离器、脱甲烷塔、脱乙烷塔,所述冷箱依次与低温分离器、压缩膨胀机相连,压缩膨胀机再与冷箱、脱甲烷塔相连,低温分离器的液相出口与冷箱相连。
上述脱甲烷塔可以优选为填料塔、板式塔或者组合塔(填料塔与板式塔组合)。
其中,低温分离器的液相出口优选通过节流阀与冷箱相连。上述冷箱优选通过节流阀与脱甲烷塔相连。
为了回收产品气的冷量和能量,将脱甲烷塔塔顶的产品气出口依次与冷箱和同轴压缩膨胀机相连。
上述冷箱为制冷剂及其他物流提供能量交换的场所，本发明的冷箱也可以拆分成两个冷箱。压缩膨胀机为主要制冷设备,为天然气深冷提供冷量，压缩膨胀机为部分膨胀气压缩机,将天然气增压,冷凝后节流过冷,作为脱甲烷塔塔顶回流液。脱甲烷塔作为提取乙烷的传质场所。
本发明的有益效果是:
本发明一种膨胀制冷生产乙烷的方法及装置，通过压缩膨胀机增压使膨胀气换热后冷凝,然后通过节流降压使该物流过冷,为深度脱乙烷提供冷量,其中压缩膨胀机成熟可靠,与其他采用膨胀制冷脱乙烷工艺相比,压缩膨胀机要求较低、投资较少、制造工期短、少一套制冷系统,同时操作维护更简洁,使得本发明的工程总投资大幅下降，乙烷提取效果好,在保证外输产品气热值的前提下,将天然气中的乙烷尽可能的脱除,为裂解乙烯提供优质原料,有利于减少原油消耗,保障乙烯工业的原料提供,同时有效避免外输气液烃析出,能优化国家能源结构,和有效利用产品天然气中提取乙烷，工艺流程简单,投资省,较传统提取天然气中乙烷工艺流程大大简化,通过天然气冷凝节流过冷回流在脱乙烷塔内深度提取乙烷,回收天然气中的烃资源,满足天然气烃露点的需要。
附图说明
下面结合附图和实施例对本发明进一步说明
图1为本发明一种膨胀制冷生产乙烷的装置的总体结构图
图2为本发明一种膨胀制冷生产乙烷的方法的流程示意图
图中：
1：冷箱 2：压缩膨胀机
3：低温分离器 4：第一节流阀
5：第二节流阀 6：第三节流阀
7：第四节流阀 8：第五节流阀
9：第六节流阀 10：脱甲烷塔底泵
11:脱甲烷塔 12：脱乙烷塔
13:脱乙烷塔顶冷凝器 14:脱乙烷塔顶回流罐
15:脱乙烷塔底重沸器 16:第一端口
17:第二端口 18:第三端口
19:第四端口 20:第五端口
21:第六端口 22:第七端口
23:脱乙烷塔顶回流泵
具体实施方式
下面结合附图和具体实施方式对本发明一种膨胀制冷生产乙烷的方法及装置作进一步详细说明：
如图2所示，一种膨胀制冷生产乙烷的方法，该方法包括，第一步S1，天然气经冷箱1预冷到-30℃至-80℃后,进入低温分离器3分为气、液两相：第二步S2，液相进入冷箱1复热后回流进入脱甲烷塔11中部；第三步S3，气相分为两部分，一部分气相进入冷箱1过冷液化后作为脱甲烷塔11顶的回流液；第四步S4，另一部分气相进入压缩膨胀机2膨胀端膨胀后回流到脱甲烷塔11；第五步S5，同时外输干气气相经过回流复热后进入脱甲烷塔11塔顶。
实施例1
如图1所示,一种膨胀制冷生产乙烷的方法,天然气经冷箱预冷至-30至-80℃后,进入低温分离器分为气液两相。低温分离器3分离出的气相分为两部分,其中小部分气相，例如20％，经冷箱1冷却液化后作为脱甲烷塔11的塔顶回流液，另一部分气相进入压缩膨胀机2膨胀端膨胀至1.0至4.0MPa.g后进入脱甲烷塔11中部。天然气在脱甲烷塔11内传质分馏,脱甲烷塔11塔底的液体进入脱乙烷塔12脱乙烷，脱乙烷塔12塔顶的气体即为含乙烷的产品气。
图中未示出贫气增压装置和冷剂制冷装置，本实施例的方法利用冷箱预冷天然气后，经过低温分离器3分离出的小部分气相经过冷箱1冷却液化、低温分离器3分离出的液相冷箱1复热以及贫气增压装置来外输干气经过过冷后分别进入脱甲烷塔11作为回流，从而脱除天然气中的绝大部分乙烷,有效地减少装置能耗。
实施例2
一种膨胀制冷生产乙烷的装置,包括冷箱1、压缩膨胀机2、低温分离器3、脱甲烷塔11、脱乙烷塔12,低温分离器3有两个气相出口,其中一个气相出口与压缩膨胀机2相连,再与脱甲烷塔11相连,低温分离器2的另一个气相出口直接与冷箱1相连，冷箱1再与脱甲烷塔11相连，低温分离器3的液相出口与冷箱1相连，冷箱1再与脱甲烷塔11相连，根据换热网络优化,冷箱也可拆分成2个冷箱。
在其他的实施例中,低温分离器3的液相出口还可以通过第三节流阀6与冷箱1相连,冷箱1还可以通过第五节流阀8与脱甲烷塔11相连。
实施例3
一种天然气提取乙烷的工艺装置,包括冷箱1、压缩膨胀机2、低温分离器3、第一节流阀4、第二节流阀5、第三节流阀6、第四节流阀7、第五节流阀8、第六节流阀9、脱甲烷塔底泵10、脱甲烷塔11、脱乙烷塔12、脱乙烷塔冷凝器13、脱乙烷塔回流罐14和脱乙烷塔底重沸器15、脱乙烷塔顶回流泵23。其中：
冷箱1与低温分离器3相连,低温分离器3有两个气相出口,其中一个气相出口与压缩膨胀机2相连,压缩膨胀机2再与脱甲烷塔11相连,低温分离器3的另一个气相出口直接与冷箱1相连，冷箱1再与脱甲烷塔11相连，低温分离器3的液相出口与冷箱1相连，冷箱1再与脱甲烷塔11相连，脱甲烷塔11的塔顶产品气出口依次与冷箱1和压缩膨胀机2连接。脱甲烷塔11塔底液依次与冷箱1和脱乙烷塔12相连。脱甲烷塔12塔底液经过冷箱1复热后进入脱乙烷塔12，脱乙烷塔顶冷凝器14依次与脱乙烷塔顶回流罐15、脱乙烷塔顶回流泵24相连，脱乙烷塔顶回流泵24再与脱乙烷塔13相连。脱乙烷塔12底液通过第六节流阀9控制与第七端口相连。
从第一端口16输出外输干气，送到贫气增压装置，在第二端口17，输出混合冷剂返回冷剂制冷装置，从第三端口18输入原料气，第四端口19输入来自冷剂制冷装置的高压冷剂，第五端口20输入来自贫气增压装置的外输干气，第六端口21输出最终成品乙烷，第七端口22输出脱乙烷塔的底液。
上述脱甲烷塔可以是填料塔、板式塔或者组合塔，组合塔为填料塔与板式塔组合。
以上所述，仅是本发明的较佳实施例而已，并非对本发明作任何形式上的限制，凡是依据本发明的技术实质对以上实施例所作的任何简单修改、等同变化与修饰，均仍属于本发明技术方案的范围内。
综上所述，本发明在结构设计、使用实用性及成本效益上，完全符合产业发展所需，且所揭示的结构亦是具有前所未有的创新构造，具有新颖性、创造性、实用性，符合有关新型专利要件的规定，故依法提起申请。

Claims (16)

1.一种膨胀制冷生产乙烷的方法，其特征在于：所述方法包括第一步(S1)，天然气经冷箱(1)预冷到-30℃至-80℃后,进入低温分离器(3)分为气、液两相：第二步(S2)，液相进入冷箱(1)复热后回流进入脱甲烷塔(11)中部；第三步(S3)，气相分为两部分，一部分气相进入冷箱(1)过冷液化后作为脱甲烷塔(11)顶的回流液；第四步(S4)，另一部分气相进入压缩膨胀机(2)膨胀端膨胀后回流到脱甲烷塔(11)；第五步(S5)，同时外输干气气相经过回流复热后进入脱甲烷塔(11)塔顶，脱甲烷塔底泵(10)将脱甲烷塔(11)底部抽出，并通过冷箱(1)调温后注入脱乙烷塔(12)。
2.如权利要求1所述膨胀制冷生产乙烷的方法,其特征在于：所述脱乙烷塔(12)顶的气相即为乙烷，采用全冷凝。
3.如权利要求1所述膨胀制冷生产乙烷的方法,其特征在于：所述脱乙烷塔(12)顶的气相即为乙烷，采用部分冷凝。
4.如权利要求1所述膨胀制冷生产乙烷的方法,其特征在于：所述压缩膨胀机(2)为同轴压缩膨胀机。
5.如权利要求1至3中任何一项所述膨胀制冷生产乙烷的方法,其特征在于：低温分离器(3)分离出的液相进入冷箱(1)复热后作为脱甲烷塔(11)进料。
6.如权利要求1至3中任何一项所述膨胀制冷生产乙烷的方法,其特征在于：所述低温分离器(3)分离出的液相直接进脱甲烷塔(11)作为进料。
7.如权利要求1至3中任何一项所述膨胀制冷生产乙烷的方法,其特征在于：自贫气增压装置来的一股贫天然气经过所述冷箱(1)过冷液化后作为脱甲烷塔(11)塔顶的回流。
8.如权利要求1至3中任何一项所述膨胀制冷生产乙烷的方法,其特征在于：外输干气经过冷箱(1)过冷液化后作为脱甲烷塔(11)塔顶的回流。
9.如权利要求1至3中任何一项所述膨胀制冷生产乙烷的方法,其特征在于：所述低温分离器(3)分离出来的一部分气相进入冷箱(1)过冷液化后作为脱甲烷塔(11)顶的回流液。
10.如权利要求9所述膨胀制冷生产乙烷的方法,其特征在于：所述低温分离器(3)分离出来的另一部分气相经过压缩膨胀机(2)膨胀端膨胀后作为脱甲烷塔(11)塔顶的回流。
11.如权利要求1至3中任何一项所述膨胀制冷生产乙烷的方法,其特征在于：择一采用气气液过冷、气气过冷、气液过冷、气过冷和液过冷的方式。
12.如权利要求1至3中任何一项所述膨胀制冷生产乙烷的方法,其特征在于：匹配不同温位的制冷负荷，提高脱甲烷塔(11)运行压力和运行温度，防止二氧化碳低温冰堵。
13.如权利要求1至3中任何一项所述膨胀制冷生产乙烷的方法,其特征在于：多元混合制冷剂采用甲烷、乙烷、丙烷、乙烯、氮气、正丁烷、正戊烷、异丁烷、异戊烷中若干种组分的组合作为制冷剂配方。
14.一种膨胀制冷生产乙烷的装置,其特征在于：所述装置包括冷箱(1)、压缩膨胀机(2)、低温分离器(3)、脱甲烷塔(11)、脱乙烷塔(12),冷箱(1)依次与低温分离器(3)、压缩膨胀机(2)、脱甲烷塔(11)相连,压缩膨胀机(2)再与冷箱(1)、脱甲烷塔(11)相连，脱甲烷塔底泵(10)将脱甲烷塔(11)底部抽出，并通过冷箱(1)调温后注入脱乙烷塔(12)。
15.如权利要求14所述膨胀制冷生产乙烷的装置,其特征在于：所述脱甲烷塔(11)择一为填料塔、板式塔和组合塔。
16.如权利要求14或15所述膨胀制冷生产乙烷的装置,其特征在于：根据换热网络优化，一个所述冷箱(1)拆分成两个冷箱。
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