Separation and capture of carbon dioxide from CO2/H2 syngas mixture using semi-clathrate hydrates

The relation between anthropogenic emissions of CO₂ and its increased levels in the atmosphere with global warming and climate change has been well established and accepted. Major portion of carbon dioxide released to the atmosphere, originates from combustion of fossil fuels. Integrated gasification combined cycle (IGCC) offers a promising fossil fuel technology considered as a clean coal-based process for power generation particularly if accompanied by precombustion capture. The latter includes separation of carbon dioxide from a synthesis gas mixture containing 40 mol% CO₂ and 60 mol% H₂.A novel approach for capturing CO₂ from the above gas mixture is to use gas hydrate formation. This process is based on selective partition of CO₂ between hydrate phase and gas phase and has already been studied with promising results. However high-pressure requirement for hydrate formation is a major problem.We have used semiclathrate formation from tetrabutylammonium bromide (TBAB) to experimentally investigate CO₂ capture from a mixture containing 40.2 mol% of CO₂ and 59.8 mol% of H₂. The results shows that in one stage of gas hydrate formation and dissociation, CO₂ can be enriched from 40 mol% to 86 mol% while the concentration of CO₂ in equilibrium gas phase is reduced to 18%. While separation efficiency of processes based on hydrates and semi-clathrates are comparable, the presence of TBAB improves the operating conditions significantly. Furthermore, CO₂ concentration could be increased to 96 mol% by separating CO₂ in two stages.     

Adhesion and detachment characteristics of a TBAB hydrate solid on a heat transfer surface (Effect of concentration of TBAB solutions)

In air‐conditioning systems, it is desirable that the liquid–solid phase change temperature of a cool energy storage material be approximately 10^°C, with respect to improving the coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize a large heat capacity of the working fluids. A solid that adheres to the heat transfer surface forms a thermal resistance layer and significantly reduces the rate of cold storage; therefore, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removal of the solid phase from the heat transfer surface was investigated. Tetra‐n‐butylammonium bromide (TBAB) clathrate hydrate was used as a cold storage material and the effect of the TBAB solution concentration on the scraping force required to detach the adhered TBAB hydrate solid from the heat transfer surface was experimentally examined. The TBAB hydrate solids were broadly categorized into two types, and the scraping force required for removal of these two types of TBAB hydrate solid was different. The scraping force required for removal of the solid increased due to the effect of increasing the concentration of the TBAB solution. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20254     

超声波悬浮TBAB溶液液滴表面半笼型水合物生长过程研究

利用超声波悬浮技术将四丁基溴化铵(TBAB)溶液液滴悬浮，观测了不同TBAB质量分数(15%、20%、25%)时的水合物生长过程，并与悬挂液滴进行了对比。实验发现，超声波悬浮的液滴处于快速旋转状态，液滴呈扁球状，水合物生长速率较快，但当液滴中含有气泡时生成水合物的诱导时间延长。总结出超声波悬浮状态下TBAB水合物生长方式可以分为两大类：由内而外，由外而内。由外而内又可以分为单平顶式、双平顶式和包裹式。建立悬浮液滴和悬挂液滴的传热模型，通过对比发现，超声波可以加快悬浮液滴的传热效率，加速水合物的生成和生长。该实验为观测水合物生长提供了一种新的方法。     

TBAB改性粉煤灰处理印染废水的实验研究

用TBAB(四丁基溴化铵)对粉煤灰进行改性后对印染废水进行脱色处理。以印染废水中存在的活性艳红为处理目标,通过一系列试验,确定较优的改性条件和脱色处理条件。试验结果表明,在TBAB浓度为2.0 g/L,粉煤灰浓度为3.5 g/L,溶液pH为2,吸附时间为1 h时,脱色率可达到最高,为91.3%。     

An effect of scraper shapes on detachment of solid adhered to cooling surface for formation of clathrate hydrate slurry

In air‐conditioning systems, it is desirable that the liquid– solid phase change temperature of a cool energy storage material is approximately 10^°C from the perspective of improving the coefficient of performance (COP). Moreover, a thermal storage material that forms slurry can realize large heat capacity of working fluids. Since the solid that adheres to the heat transfer surface forms a thermal resistance layer and remarkably reduces the rate of cold storage, it is important to avoid the adhesion of a thick solid layer on the surface so as to realize efficient energy storage. Considering a harvest type cooling unit, the force required for removing the solid phase from the heat transfer surface was studied. Tetra‐n‐butylammonium bromide (TBAB) clathrate hydrate was used as a cold storage material. The effect of the scraper shapes on the scraping force for detachment of the adhered solid of TBAB hydrate to the heat transfer surface was examined experimentally. The TBAB hydrate solids were categorized broadly into two kinds of solids. The scraping force of the TBAB hydrate solid on the heat transfer surface was different for the two kinds of the TBAB hydrate solids. And the scraping force of the TBAB hydrate solid formed after scraping was improved by the modifying the scraper shape. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(8): 489– 500, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20179     

Nation膜对多硫化钠／溴电池性能的影响

在单电池中用充电一放电循环测试方法研究了不同厚度Nation膜对多硫化钠／溴单电池效率及电池负极液中的多硫（Sx＋1^2-）及硫氢根离子（HS^-）向正极溶液中扩散（即透硫率）的影响。结果表明：随着膜厚度的增加，电池的库仑效率升高，膜的透硫率及电压效率降低。用四丁基溴化胺（TBAB）对Nation112膜进行了初步改性处理，显著提高了电池的库仑效率，减少了膜的透硫率，但由于改性膜电阻的增加，致使电池电压效率下降。     

水合物法分离烟气(CO2/N2)中CO2的实验研究

利用四丁基溴化铵(TBAB)作为促进剂进行了水合物法分离烟气(CO2/N2)的实验研究.结果表明较高TBAB浓度下生成的水合物较多,其中包含更多的未填充气体的纯TBAB水合物;解析气中的CO2含量受到气体消耗率及实验初始压力的影响;TBAB浓度、实验温度在实验条件范围内对解析气中的CO2含量影响并不明显.CO2摩尔分数为17.4%的CO2/N2混合气通过_二级水合物/膜分离流程可回收到CO2摩尔分数为95.0%的解析气.     

Phase equilibrium modeling of semi-clathrate hydrates of the CO2+H2/CH4/N2+TBAB aqueous solution system

In this study, the semi-clathrate hydrate dissociation pressure for the CO₂+N₂, CO₂+H₂, CO₂+CH₄, and pure CO₂ systems in the presence of different concentrations of TBAB aqueous solutions is predicted using a strong machine learning technique of multi-layer perceptron neural network (MLP-NN). The developed model, with an overall correlation coefficient (R²) of 0.9961 and mean square error (MSE) of 5.96E?02, presented an excellent accuracy in prognosticating experimental data. A complete statistical evaluation performed to promise the strength and generality of the multi-layer perceptron artificial neural network (MLP-ANN). In addition, the applicability of the proposed network and quality of experimental data was assessed through the Leverage approach.     

四丁基溴化铵-四氢呋喃系蓄冷水合物

基于二元工质水合物相对单一工质水合物在蓄冷特性方面的优越性,在水合物客体组分总质量分数为31.4%的条件下,实验研究了四丁基溴化铵(TBAB)-四氢呋喃(THF)混合水合物蓄冷特性. 通过改变TBAB-THF组分配比,考察了水合物的诱导时间、近似相变温度、蓄冷面积及释冷面积的变化. 结果表明,TBAB-THF系中TBAB浓度减少使诱导时间增长、温度突变点降低、近似相变温度降低,从而减小了水合物在生长阶段的蓄冷面积,缩短了分解阶段的分解完成时间;TBAB浓度在25.7%~27.4%时,相变温度在6.3~8.0℃之间,与空调冷冻水相近,且释冷面积相对其他浓度较高,可作为蓄冷空调的良好介质.     

Modelling of gas to hydrate conversion for promoting CO2 capture processes in the oil and gas industry

In this contribution, equilibrium conditions of clathrate hydrates containing mixtures of carbon dioxide and tetra-n butylammonium bromide and tetra-n butylammonium chloride are modeled by a combination of particle swarm optimization algorithm with least square support vector machine intelligent approach. The evaluation of aforementioned model has been conducted by statistical analyses between experimental and predicted values. The obtained results show excellent performance of proposed model.