Adsorption And Separation Of CO₂/CH₄on Modified Activated Carbon Fibers

With the development of the industry and the world energy crisis intensified, the research and development of new energy has become the one of the main tasks, such as hydrogen, methane, etc. CH4is the main components of natural gas, methane, landfill gas and coal bed methane, but it often coexist with CO2. Therefore many scientific workers are working on clean energy, such as biogas and natural gas. At the same time, the atmosphere "greenhouse effect" and global warming are the biggest environmental problems which humanity is facing in the21st century. At present, emission of CO2during the process of energy consumed by human is the one od main reasons for this phenomenon. In addition, CH4emissions also has a great influence on the greenhouse effect. In the coexist system of CO2and CH4. CO2affect the burning effect of CH4and cause shipping line corrosion at the same time. So. from the perspective of protecting environment and saving energy, to recycle and separate CO2/CH4is very necessary.In this paper, the CO2, and CH4adsorption and separation capacity had been discussed on the organic solvent method. It paid more attention to the adsorption and separation activity of CO2. and CH4on ACF and K2CO3/ACF in static volumetric adsorption and dynamic adsorption. The preparation condition, operation condition and regeneration methods were investigated, then the mechanisms of adsorption and separation CO2and CH4were discussed based on the thermodynamics, kinetics, experimental study and literatures. To provide theoretical basis of efficient purification for natural and biogas. In this study, the main results are as follows:(1) In order to study the adsorption performance of modified ACF, a series of activated carbon fibers loaded on different alkaline earth metal and metal ions were prepared by impregnation method. The effects of conditions including the Precursors, types and concentrations of nitrates, calcining temperature and adsorption reaction temperatures were investigated. The adsorption and separation properties of CO2/CH4on the prepared samples were examined. Among the adsorbents, ACF-K exhibited the best result to remove CO2from CH4mixture all together. The results showed that ACF prepared by impregnating0.3mol/L K2CO3was the best adsorbent for CO2/CH4adsorption and separation, under condition of298K and calcining temperature is500-600℃, the adsorption effect of CO2and CH4were best. Adsorption amount of CO2is4.33mmol/L and the separation factor is3.78.(2) Secondly, the experimental condition and the regeneration performance were studied. First of all, experimental condition included two aspects of experimental temperature and water content. The results showed that the more adsorption temperature was lower, the gas adsorption performance was higher. At the same time, when the water content of activated carbon fiber was4.58%, which is promote to the separation of CO2and CH4.Choosing three kinds of ways of renewable to research the effect of adsorption capacity of CO2and CH4. They are water recycling, alkali cooking and heating, respectively. The research results showed that the regeneration performance of heating regeneration was better than that of water and alkali boiling regeneration. Heating regeneration is easy to operate and the adsorbent separation factor is high. All in all, the way of heating regeneration mostly made the adsorbent keep its original adsorption performance.(3) The adsorption characteristics of pure component on activated carbon fiber (ACF) and K2CO3/ACF at temperatures ranging from298K to323K had been experimentally measured by a volumetric apparatus. The equilibrium data were analyzed by the Langmuir and Freundlich model, which revealed that Freundlich model was more suitable to describe the adsorption of the three gases than Langmuir model. The Henry’s Constant was investigated based on the adsorption isotherms. The results showed that adsorption affinity follows the order:CO2> CH4on ACF and K2CO3/ACF. CO2was more easy adsorbed on surface of adsorbents than CH4. Isosteric heat of adsorption was calculated to characterize adsorption behaviors. From the result of analysis of Isosteric heat of adsorption, the surface of ACF was mainly made up of heterogeneous adsorption. In addition, adsorption behavior of CH4on ACF and K2CO3/ACF is physical adsorption; However, the adsorption of CO2on K2CO3/ACF not only existed physical adsorption but also existed chemical adsorption. Combined with XRD and Thermogravimetric(TG), further adsorption mechanism of CO2and CH4on K.2CO3/ACF was analyzed. Reaction of CO2n、K2CO3and H2O, and generated KHCO3; potassium oxide reacted with CO2to generate K2CO3.