【作者】 薛全民；

【导师】 周亚平；

【作者基本信息】 天津大学 ， 物理化学， 2009， 博士

【摘要】 二氧化碳排放所产生的温室效应是一个令人担忧的全球性环境问题;而绝大多数排放的二氧化碳是由化石燃烧所产生的,因此从烟道气中分离和捕集二氧化碳对降低温室气体排放具有重要的意义。此外,许多开采出的天然气中含有大量二氧化碳,严重影响天然气的使用,因此从天然气中分离二氧化碳对提高天然气的热值和使用也具有重要实际意义。在本文中,以CH₄/CO₂和N₂/CO₂为模型混合气,研究了醇胺改性吸附剂的吸附分离性能。首先选择了高沸点的三乙醇胺（TEA）、N-甲基二乙醇胺（MDEA）和混合胺N-甲基二乙醇胺+哌嗪（MDEA+PZ）,用不同浓度的醇胺液对硅胶和活性炭进行了改性,分别进行了CH₄/CO₂混合气的穿透和脱附再生实验研究,得到了它们的穿透曲线以及分离因子等数据;另外,选择了13X型沸石分子筛吸附剂,对其进行了穿透和脱附再生实验研究,也得到了它们在不同条件下的穿透曲线、分离因子、再生成本以及再生度等参数。对不同吸附剂的吸附分离性能进行了比较与分析:硅胶在TEA负载率为0.8,MDEA负载率为0.6,PZ/MDEA摩尔比为R=0.167时,分离因子最佳,分别为10.09、11.05和18.98;而活性炭和用MDEA改型的活性炭对混合气的分离因子均非常小。13X型吸附剂的分离因子为6.24。吸附剂可以用吹扫的方法在较短时间内实现再生,而其吸附容量仍保持稳定,经过多次吸附再生循环液膜也保持不变,表明本文研究的吸附剂适合变压吸附过程。在不同的工艺条件下,进行了变压吸附工艺的连续变压操作实验。考察了操作压力、吸附时间、均压时间、吹扫时间、吹扫气速等指标,确定了适宜的变压吸附操作条件。连续操作说明了吸附剂性质是稳定的。二氧化碳在出口气浓度经过9个循环后可以低于0.05%,并且200循环后仍保持稳定。表明胺改性硅胶吸附剂吸附适合分离CO₂/N₂和CO₂/CH₄。更多还原

【Abstract】 Greenhouse effect is one of the global environmnental problems. The main greenhouse gas is carbon dioxide, while the exhaust gas from power stations is the main sources of CO₂ emissions, so separation/capature of carbon dioxide has significant effect to the decreasing of greenhouse gases emission.In this paper, the first aim was to find an excellent adsorbent to separate CO₂ from its mixture. Firstly, triethanolamine （TEA）, N-Methyldiethanolamine （MDEA） and mixed amine with high boiling point and different concentration were selected to modify the surface of silica gel and activated carbon, which were researched by adsorption and desorption experiments for the mixtures of CO₂ and CH₄ respectively. The breakthrough curves、desorption curves, and the parameters of separation factors and purging ratios were obtained. In addition, 13X molecular sieve was researched by adsorption and desorption experiments for the mixtures of CO₂ and CH₄ respectively, whose breakthrough curves, desorption curves, and the parameters of separation factors and purging ratios were obtained.The compare and analysis for adsorption and desorption performances of different sorbents showed: when silica gel coating ratio 0.8 TEA, silica gel coating ratio 0.6 MDEA, silica gel coating Piperazine（PZ）/MDEA mole ratio（R=0.167）, their separation factors were optimal and were 10.09, 11.05 and 18.98 respectively. For activated carbon and it coating MDEA, their separation factors were very small. For the 13X molecular sieve, the separation factor was 6.24. The sorbent regeneration could be achieved by pressure reduction and back-purge at ambient temperature in short time and it’s capacity remains stable after many cycles of breakthrough and regeneration just as the liquid film, which proved the feasibility of the PSS process using this new sorbent. therefore, the silica gel coating PZ/MDEA with mole ratio（R=0.167）for separation of CO₂ and CH₄ was best.PSS process was tested for different process conditions. Cycle sequence including adsorptive pressure, the times for sorption, pressure equalization and the propriate purge gas velocity were determined. Continuous operation test demonstrated that the sorption property was stable, and the content of CO₂ in the column-top stream decreased to below 0.05% in 9 cycles and kept the level till the end of 200 pressure swing sorption （PSS） cycles. A 2-column process was used to verify the applicability of the pressure swing sorption technology using the amine-modified sorbent for the separation of CO₂/N₂ and CO₂/CH₄ and remained stable in long-time, which proves the industrial applicability of the new technology.更多还原