N-甲基二乙醇胺溶液中CO_(2)气体吸收与水合物生成特性实验研究

Experimental study on CO_(2) gas absorption and hydrate formation of N-methyldiethanolamine solution

目的酸性气田开发气流中往往含有二氧化碳(CO_(2))和硫化氢(H 2S)等酸性组分,易形成天然气水合物(简称水合物),引起管道堵塞。解决酸性组分吸收剂对水合物作用机制不明确问题,为脱除酸性气体组分并防治水合物生成提供理论依据。方法采用恒温恒容法研究了N-甲基二乙醇胺(MDEA)溶液质量分数、搅拌状态及初始压力对CO_(2)气体吸收规律的影响、MDEA溶液对CO_(2)水合物生长速率和宏观晶体形态的影响,并与传统热力学抑制剂乙二醇(EG)效果进行对比。结果CO_(2)气体吸收量随MDEA溶液质量分数的增加表现为先增后减的趋势。开启搅拌和降低压力可加快CO_(2)气体的吸收速率,增加气体吸收量。在气液界面,水合物晶体以二维模式生长,并且MDEA可改变CO_(2)水合物的宏观形貌,增加其质量分数可显著增加CO_(2)水合物覆盖溶液表面的时间、降低CO_(2)水合物的生长速率。与EG相比,MDEA水合物的动力学抑制效果较差,但水合物膜覆盖时间较长,生长速率较慢。结论MDEA可与溶液中水分子形成氢键,与水合物竞争水分子,减少水的活性,同时,MDEA分子可与CO_(2)分子结合,与水合物竞争CO_(2),显著降低水合物生长速率。研究结果对酸性气体的分离捕获和天然气流动的安全保障具有理论指导意义。

Objective The gas flow during the exploitation of sour gas fields often contains sour components such as carbon dioxide(CO_(2))and hydrogen sulfide(H 2S),which are easy to form natural gas hydrates(hydrate for short)and cause pipeline blockages.The aim is to solve the problem of unclear mechanisms of sour component absorbers on hydrates,which could provide a theoretical for removing sour gas components and preventing hydrate formation.Methods In this paper,the isothermal and isochoric methods investigated the effects of the mass fraction,stirring state,and initial pressure of N-methyldiethanolamine(MDEA)solution on the absorption law of CO_(2).The effects of MDEA solution on the growth rate and macroscopic morphology of CO_(2) hydrate were also studied and compared to the conventional thermodynamic inhibitor ethylene glycol(EG).Results The study indicated that the absorption rate of CO_(2) showed a trend of increasing and then decreasing with the increase of the mass fraction of the MDEA solution.The stirring state and lower initial pressure could accelerate the absorption rate of CO_(2) and increase the amount of gas absorption.At the gas-liquid interface,hydrate crystals grew in a two-dimensional mode,and MDEA could change the macroscopic morphology of CO_(2) hydrates.Increasing the mass fraction of MDEA solution could significantly increase the time for CO_(2) hydrates to cover the surface of the solution and reduce the growth rate of CO_(2) hydrates.In contrast to the EG,the kinetic inhibition of MDEA hydrates was poorer,but the cover time of the hydrates film was longer,and the growth rate was slower.Conclusions It is analyzed that MDEA could form hydrogen bonds with water molecules in the solution and compete with hydrates for water molecules,reducing water activity.It could also combine with CO_(2),and compete with hydrates,significantly decreasing the growth rate of hydrate.The research results have theoretical significance for the guidance of the separation and capture of sour gases and natural gas transportation.