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GO与SDS复配促进CO2水合物生成技术研究

作者:完美论文网  来源:www.wmlunwen.com  发布时间:2019/10/8 9:08:00  

摘要:气体水合物是由客体分子和主体分子在低温、高压下,通过氢键作用形成的一种非化学计量的笼形包合物。其不仅可以作为高效清洁的新能源,还具有巨大的储气能力,基于水合物生成衍生出的技术受到人们的青睐。但是相关技术的大范围推广和实际应用却因生成条件苛刻、生成速率低、促进剂效果难以满足工业应用且并不经济环保、预测模型众多而不具备普遍适用性等问题所限制。为解决上述问题,首先亟待开发高效、经济、绿色的复合促进剂,其次建立精确和适用性高的气体水合物生成模型。根据前期研究发现,氧化石墨烯(GO)能够降低液面表面张力并强化传热传质,有利于优化水合物生成条件、加快生成速率、增大储气量和提高促进剂循环利用率。化学亲和力模型是根据宏观参数温度、压力,以水合反应过程中亲和力的衰减为基础,建立的水合物生成模型,具有普遍适用性且参数易测、准确度高。本课题在此基础上,从实验和模型两个方面对GO促进效果和机理进行了验证和分析。考虑到单一的促进剂促进效果的局限性,提出动力学促进剂中效果最好的SDS与GO进行复合,配制新型复合促进剂,同样从实验和模型两个方面,对复合体系下CO2水合物的生成进行系统的研究。最后,建立了适用于GO、GO与SDS复合体系下的水合物生成模型。首先,实验采用恒温定容方法,利用高压反应釜实验装置研究了在277.15K~281.15K和4~6MPa工况下,浓度分别为0.001%、0.005%、0.02%、0.03%、0.04%、0.05%的GO对CO2水合物过程的影响。从实验方面探讨了CO2水合物在GO溶液中的生成过程,详细分析了过程中温度、压力的变化趋势,以及GO浓度对水合反应过程中的压力、生成时间和气体消耗量的作用效果,并与纯水体系进行了对比,确定出最佳促进浓度并分析了促进机理。其次,研究了在相同工况下,0.005%GO与0%、0.005%、0.1%、0.2%、0.3%的SDS复合浓度及0.2%SDS与0.003%、0.005%、0.01%、0.02%的GO复合浓度对CO2水合物生成过程中温度、压力及耗气量的影响,并与纯水和GO浓度为0.005%的体系对比,分析复合添加剂的促进机理,得到最佳复合促进剂浓度。最后,推导并建立了GO、GO与SDS复合促进剂体系下CO2水合物生成化学亲和力模型,并从模型方面分析了添加剂浓度、温度、压力对水合反应到达平衡的时间、平衡压力、耗气速率和耗气量等的作用机理及影响规律。结果表明:①与纯水相比,各温度下不同浓度GO均能降低水合物相平衡压力、缩短生成时间和增大耗气量。随着GO浓度的增大,GO体系压降、耗气量和耗气速率均先增大后减小,平衡压力和生成时间反之。在279.15K、4MPa工况下,在0.005%GO体系中,压降最大,生成时间仅135min,近纯水体系的1/2;耗气量达最大值0.209mol,相比纯水提高了28.2%。②GO与SDS复合可以促进CO2水合物的生成,表面活性剂SDS与GO将彼此的促进作用相互加强,更为均匀、稳定地分散在溶液中,加强传热传质效率,形成更多的成核点,增大耗气量,缩短生成时间。③与纯水和0.005%GO体系相比,GO与SDS的复合体系下水合反应过程中的温度峰值、平衡压力均低,生成时间短,耗气量大。随着GO或SDS浓度的增大,温度峰值、压降耗气量均先增大后减小,平衡压力反之。其中0.005%GO+0.2%SDS体系下的温度峰值最快达到稳定且相较于纯水和0.005%GO体系,分别降低了0.23%和0.15%;到达最低平衡压力1.949MPa仅167min,平衡压力降低了11.3%和3.0%,生成时间缩短了69.7%和65.6%;产生最大耗气量0.5639mol,增大了11.24%和3.2%。④通过模型分析,低温、高压和添加促进剂均有效促进水合物的生成。温度越低、压力越高,水合反应达到平衡的时间越短。温度和添加剂的浓度对模型参数的影响较大,受压力影响较小,但压力越高,模型参数与实验参数的拟合度越高,模型预测CO2水合物生成越精确。在单一的GO和GO与SDS的复配浓度中,平衡时间最短、平衡压力最低的最佳促进浓度分别为0.005%GO和0.005%GO与0.2%SDS,其中,0.005%GO与0.2%SDS效果最好。

Gas hydrates are a class of non-stoichiometricclathrates, composed of guest molecules and hydrogen-bonded host molecules inlow temperature and high pressure, which not only can be used as high-effectiveclean energy but also owns a huge gas capacity. Thus, many technologies basedon hydrate formation are widely favored. Unfortunately, the widely promotionand practical application of hydrate utilization technologies have beenhindered by some problems including the harsh formation conditions, low hydrateformation rate, uneconomical and environmentally unfriendly promoters which hastoo low promotion affection to satisfy industrial production need, too manykinds of prediction models that are not universally applied and so on. To solvethese problems, one is to develop efficient economical and green hydrateformation promoters, the other is to build gas hydrate formation models thathave high forecast accuracy and good applicability.

According to the previous research,graphene oxide (GO) can not only lower the surface tension but also enhance theheat and mass transfer efficiency. GO has great advantages in improving thehydrate formation conditions, accelerating production rate, enlarging gasstorage and increasing the cyclic utilization of promoters. According to themacroscopic properties such as temperature and pressure, based on affinitydecay of the hydrate reaction, the hydrate formation kinetic model based onchemical affinity was built. Based on the previous researches, CO2 hydrateformation kinetics with GO were verified and analyzed through experiments andmodel. Considering of the limitation of a single promoter, GO combined withSDS, which is the best promotion effective kinetic accelerator, were proposedas a new compound promoter. CO2 hydrate formation kinetics with GO and SDS wereverified and analyzed through experiments and model. Finally, hydrate formationkinetic models with GO and GO compounded with SDS were built.

First of all, the effects on CO2 hydrateformation at the temperature of 277.15~281.15K, the pressure of 4~6MPa and in the GO solution of 0.001%, 0.005%, 0.02%, 0.03%, 0.04%,0.05% are experimentally investigated by constant volume and temperaturemethod. The change rules of temperature and pressure during CO2 hydrateformation were discussed through experimental parameters. The effects of GOconcentration on pressure, formation time and gas consumption are also detaileddiscussed. Compared to the pure water system, the optimum concentration of GOis determined. Secondly, at the same conditions, the effect on CO2 hydrateformation of compound solutions of 0.005% GO with 0%, 0.005%, 0.1%, 0.2%, 0.3%SDS and 0.2% SDS with 0.003%, 0.005%, 0.01%, 0.02% GO are experimentallystudied. The effects of GO and SDS compound solutions on temperature, pressureand gas consumption during CO2 hydrate formation are detailed reported.Compared with the systems with no additive and 0.005% GO, the kinetics of CO2hydrate formation are studied and the optimum concentration of GO compoundedwith SDS is determined. Finally, the models based on chemical affinity of CO2hydrate formation with GO and GO compounded with SDS are established. Theeffects and rules of additives’ concentration, temperature and pressure on theequilibrium time, equilibrium pressure, the rate of gas consumption and theamount of gas consumption are detailed analyzed through model parameters.

It is shown that different concentrationsof GO all can lower equilibrium pressure, shorten formation time and increasegas consumption. Along with the increase of GO concentration, the pressuredrop, the amount and the rate of gas consumption increase and then decrease,while equilibrium pressure and the formation time are on the contrary. At thetemperature of 279.15K, the pressure of 4MPa and in the 0.005% GO system, thepressure drops mostly greatly and the formation progress costs 135min, which isnearly half of the pure water system.

关键词:气体水合物;氧化石墨烯;SDS;水合物生成促进;化学亲和力模型

gas hydrate; graphene oxide; SDS; hydrateformation promotion; chemical affinity model

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