海上天然气净化脱CO2过程吸附/脱附特性研究

It is imperative to develop the offshore natural gas in order to meet the growing consumption of natural gas. The marine environment is harsh and the floating production, storage and offloading device for LNG is often operated in the state of the irregular waggle caused by the waves, typhoons and other factors. Furthermore, the space on the deck is very small. Therefore, the adsorbent and its adsorption/desorption characteristics are studied for offering the theory guidance on removing CO2 from the offshore natural gas. An efficient adsorbent for CO2 removal from natural gas is obtained during the studies of adsorbent microstructures and adsorption/desorption. The influences of some factors on the adsorption/desorption characteristics of the adsorbent are discussed. These factors include the physical parameters of the adsorbent, heat and mass transfer, and the irregular waggle of the adsorbent bed. On the basis of some assumptions, the governing equation model of the adsorption purification process is established combination of heat and mass transfer theory. The model is resolved by numerical simulations method. Then the comparison between the model and the experimental data has been completed. Furthermore, the effect of heat and mass transfer on adsorption/desorption process has been considered. Especially, the bulk density and porosity of adsorbent and the void space of adsorbent bed are variable under the irregular waggle of the adsorbent bed. The model of the adsorption purification is constructed in these situations. The synthetic methods including experimental measurements, theoretical analyses and numerical simulations are used for the deeply systematic investigation. This study will help to improve the development efficiency of the offshore natural gas, and have a very great significance for the rapid development of natural gas.

为满足日益增长的天然气消费量，开发海上天然气资源势在必行。海上环境恶劣，浮式液化天然气生产储卸装置常在不规则摇摆状态下作业，而且甲板上空间狭小，因此对吸附剂及其吸脱附特性进行研究，能够为海上天然气净化脱CO2的优化设计提供理论指导。首先对吸附剂进行微观结构表征，并进行吸脱附研究，进而筛选出一种高效吸附剂。然后，研究吸附剂的物性参数、传热传质及吸附床不规则摇摆对吸脱附特性的影响。在一些假设条件的基础上，结合传热传质理论，建立吸附净化模型。采用数值方法，模拟吸附床吸附过程，再与实验结果对比分析，讨论传热传质对吸脱附过程的影响。特别是在吸附床不规则摇摆条件下，吸附剂的堆密度、孔隙率和床层空隙率均是变量，建立吸附床不规则摇摆条件下的吸附净化模型，通过理论分析、实验研究和数值模拟相结合的方法对其进行系统深入的研究。本项目的研究结果将会提高海上天然气的开发效率，对天然气的快速发展具有十分重要的意义。

为满足日益增长的天然气消费量，开发海上天然气资源势在必行。海上环境恶劣，浮式液化天然气生产储卸装置常在不规则摇摆状态下作业，而且甲板上空间狭小，因此对吸附剂及其吸脱附特性进行研究，能够为海上天然气净化脱CO2的优化设计提供理论指导。研究内容包括：在对吸附剂微观结构表征的基础上，利用搭建的吸脱附实验台，结合蒙特卡罗模拟和气体混合物选择性吸附理论，筛选出一种高效的天然气净化脱CO2的吸附剂；在考虑吸附热效应的条件下，建立吸附净化模型，研究吸附剂的颗粒直径，传热传质和吸附床不规则摇摆对吸脱附特性的影响。研究表明：通过蒙特卡罗模拟，LiPdAgX分子筛表现出了很好的CO2/CH4吸附分离效果；XRD、SEM和物理分析仪等微观结构测试手段表明改性后的分子筛相对结晶度提高，与气体的接触面积增大，有利于吸附反应的进行；在298K和1.37MPa下，13X分子筛对混合气体中CO2的选择性系数为71，LiX和LiPdAgX分别为103和128，表明改性后的分子筛对混合气体的分离效果增强；通过对动态穿透曲线的研究，发现改性后分子筛的穿透时间延长，分离因子由13X的3.96提高到了LiPdAgX的7.17；改性后分子筛再生时所需热量较少，能耗更低，LiPdAgX分子筛在循环使用后仍能保持较高的气体分离因子；随着吸附剂颗粒直径的增加，吸附罐内压降急剧降低，当吸附剂颗粒直径为2mm时，吸附罐出口处甲烷摩尔浓度最高，吸附净化效果最佳；增大CH4或CO2吸附相传质系数会降低吸附罐中该物质的摩尔浓度，而对另一种物质的摩尔浓度没有影响；通过摇摆实验和模拟研究，在吸附剂粒径为1.6mm的情况下，空隙率为0.35时动态吸附的效果最佳。本项目的研究结果将会提高海上天然气的开发效率，对天然气的快速发展具有十分重要的意义。