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Effective Design of a Vacuum Pressure Swing Adsorption Process To Recover Dilute Helium from a Natural Gas Source in a Methane-Rich Mixture with Nitrogen
Industrial & Engineering Chemistry Research ( IF 3.8 ) Pub Date : 2018-09-17 , DOI: 10.1021/acs.iecr.8b00798
Parisa Eghbal Jahromi 1 , Shohreh Fatemi 1 , Ali Vatani 1
Affiliation  

The conventional method of helium production is a cryogenic process, which is installed downstream of a liquefied natural gas (LNG) plant, where a helium extraction unit (HeXU) would be usually developed as the byproduct unit, due to the high cost of the process. In this study, pressure swing adsorption method accompanied by a relative vacuum condition for the bed regeneration (PVSA) was investigated as an alternative method for recovery of helium from natural gas source. The PVSA design was studied for a continuous product, utilizing zeolite 13X as the adsorbent, through a formerly validated model, for a dilute feed of 1.5 vol % He, mainly comprised of methane in 82.5 vol % accompanied by nitrogen. The impacts of repressurizing medium and equalization steps of the design conditions on the He purity and recovery were investigated. It was revealed that, generally, the bed repressurizing step should be performed by the feed as compared to the product. However, at high space velocities, a combination of the feed and product would be preferable to achieve higher He purity. Adding an equalization step is not advantageous to the process design at medium to high space velocities, but can be exploited only for recovery improvement when the purity is in an acceptable high range at low space velocities. Feasibility of the adsorption method and its performance was then analyzed in a basic 4bed-4step PVSA cycle design for different effective parameters including dimensionless space velocity (), bed pressure in adsorption step, and vacuum pressure in regeneration step and their interactions. However, due to the complex trends of the effective parameters and their interactions, response surface methodology (RSM) was implemented for optimization of the cycle performance. At the optimal design point with a feed pressure of 5.75 (bara), regeneration pressure of 0.05 (bara), and () of 2.25, a helium purity of 99.9% and a recovery of 70% with productivity of 0.335 (mol/kg-adsorbent·h) would be achieved.

中文翻译:

在富氮甲烷混合气中从天然气源中回收稀氦的真空变压吸附工艺的有效设计

常规的氦气生产方法是低温工艺,该工艺安装在液化天然气(LNG)厂的下游,由于该工艺成本高,通常将氦气提取装置(HeXU)用作副产品。 。在这项研究中,研究了变压吸附法和相对真空条件下的床层再生(PVSA),作为从天然气源中回收氦气的替代方法。通过以前验证的模型,使用13X沸石作为吸附剂,对PVSA设计的连续产品进行了研究,得到了1.5 vol%He的稀进料,主要由82.5 vol%的甲烷和氮气组成。研究了加压介质和设计条件的均衡步骤对He纯度和回收率的影响。已经发现,与产品相比,床加压步骤通常应由进料进行。然而,在高空速下,进料和产物的组合将是优选的,以实现更高的He纯度。添加均衡步骤不利于中高空速下的工艺设计,但是当纯度在低空速下处于可接受的高范围内时,只能用于提高回收率。然后在基本的4bed-4step PVSA循环设计中针对不同的有效参数(包括无量纲空速(为了获得更高的He纯度,最好将饲料和产品结合使用。添加均衡步骤不利于中高空速下的工艺设计,但是当纯度在低空速下处于可接受的高范围内时,只能用于提高回收率。然后在基本的4bed-4step PVSA循环设计中针对不同的有效参数(包括无量纲空速(为了获得更高的He纯度,最好将饲料和产品结合使用。添加均衡步骤不利于中高空速下的工艺设计,但是当纯度在低空速下处于可接受的高范围内时,只能用于提高回收率。然后在基本的4bed-4step PVSA循环设计中针对不同有效参数(包括无量纲空速(),吸附步骤中的床压,再生步骤中的真空压及其相互作用。但是,由于有效参数及其相互作用的复杂趋势,因此采用了响应面方法(RSM)来优化循环性能。在最佳设计点上,进料压力为5.75(bara),再生压力为0.05(bara),()为2.25,氦气纯度为99.9%,回收率为70%,生产率为0.335(mol / kg-吸附剂·h)。
更新日期:2018-09-17
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