【作者】 张亮亮；

【导师】 陈建峰；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2012， 博士

【摘要】 近年来,由于经济的高速发展,化石燃料大量消耗,进入地球大气层的CO2量随之增多,这是导致温室效应加剧和全球气候异常的主要原因；另一方面NOx的过量排放(尤其在中国),造成了酸雨、雾霾天气等众多环境问题。工业尾气中CO2捕集及NOx脱除已经刻不容缓。众多研究表明,化学吸收方法是目前CO2大规模捕集领域中最适宜的技术之一。近年来,采用离子液体作为吸收剂进行CO2捕集成为了该领域的研究热点。离子液体具有挥发性低、性质稳定、结构可调等众多适宜作为化学吸收剂进行CO2捕集的优点,然而由于离子液体的粘度很大,导致了CO2在离子液体中的气液传质过程缓慢,吸收速率低,吸收时间长等问题成为困扰采用离子液体CO2捕集实用化的瓶颈；前人针对络合溶液脱除NO的研究表明,NO和络合溶液的络合速率一般都很快,络合吸收反应是一个受气液传质控制的过程。由此可见,上述两个化学吸收过程亟待解决的关键问题是相同的。强化气液传质,促进化学吸收是发展CO2和NOx化学吸收方法的核心所在。超重力旋转填充床(RPB,也称为旋转填充床)作为新型的多相流混合装置和反应器,可以极大的强化液液、气液传质,该技术已被成功应用于化工分离过程和纳米材料制备。本论文研究工作旨在将超重力旋转填充床作为气液反应器,应用于CO2捕集及NOx脱除过程中。论文对超重力旋转填充床内的CO2与离子液体物理吸收和反应吸收的过程进行了研究,测定了CO2与离子液体在超重力旋转填充床中的传质系数,提出了有应用前景的C02捕集过程新工艺和NO脱除的过程新工艺。基于实验研究和前人研究结果,本文建立了超重力环境下CO2与离子液体吸收过程的数学模型,对超重力环境下强化气液传质的机理进行了研究。根据模型,对操作参数及设备尺寸进行了优化模拟。为产业化应用提供了理论依据和支持。本论文主要创新工作如下：1、以常规离子液体[Bmim][PF6]物理吸收CO2过程为研究体系,测量了超重力旋转填充床中该过程的液相体积传质系数,并对比研究了填料塔中该过程的液相体积传质系数。比较结果发现：在相近的操作条件下,超重力旋转填充床的液相体积传质系数KL为0.95-3.9x10-2s-1,而填料塔的液相体积传质系数KL仅为0.63-1.9×10-3s-1。相对于填料塔,超重力旋转填充床中液相体积传质系数提高了一个数量级以上,超重力旋转填充床强化CO2吸收效果明显。2、以CO2在功能化离子液体[Choline][Pro]中的化学吸收过程为研究对象,考察了不同操作条件下,CO2在离子液体中的脱除率和负载量。结果表明,超重力旋转填充床适宜用做CO2在离子液体中的化学吸收过程的反应器。在较优操作条件下,CO2在离子液体中的化学吸收可以在极短时间内(约0.2s)达到0.2mol CO2/mol IL。使用10%(vO1)的混合气时,吸收剂的负载量可以达到25Kg CO2/m3IL以上,脱除率保持在90%,使用20%(vO1)的混合气时,吸收剂的负载量可以达到40Kg CO2/m3IL以上,表明该方法具有很好的实用化应用前景。3、以功能化离子液体[Choline][Pro]反应吸收C02的过程作为气液传质的研究体系,基于Higbie渗透理论建立了超重力环境下伴有可逆反应的气液传质模型,获得了液膜中C02随时间和渗透深度的浓度解析表达式,并进一步推导出了超重力环境下的相应传质系数。利用该模型,可以预测不同操作条件下C02在超重力旋转填充床中的脱除率,预测结果与实验结果吻合良好。揭示了超重力旋转填充床强化气液传质的作用机理是使液膜中可溶性气体具有很高的浓度梯度而实现的。基于数学模型,预测了填料半径对C02脱除率的影响关系,可对不同操作条件下填料半径的尺寸进行优化设计,以提高吸收液中C02的负载量。4、以FeSO4和Na2EDTA结晶水合物为原料制备了FeⅡEDTA络合吸收剂,采用该络合吸收剂在超重力旋转填充床中进行NO脱除的实验研究,以NO的脱除率作为考察目标,考察了超重力旋转填充床内超重力水平、气液流量比、气液流速、络合吸收液pH值,温度及进口气体总压、NO浓度等对实验脱除率的影响。实验结果发现,当络合吸收液的pH值为7,超重力旋转填充床内超重力水平为200g时,NO的脱除效率最优。吸收体系温度升高,气液比增大会导致NO脱除率下降；而提高吸收液浓度、提高进口气体压力则导致NO的脱除率提高。当使用0.04mol/L络合吸收液,气液流量比为125：1,超重力水平为200g,温度为298K,进口NO浓度为1000ppm时,压力为0.35MPa时,NO的脱除率最高,可达95%。更多还原

【Abstract】 Recently, with the rapid development of economy and consumption of fossil fuels, the amount of CO2explored into the earth’s atmosphere is increasing, which leads to greenhouse effect intensify and global climate anomaly; meanwhile, excessive emission of NOx (especially in China) causes a lot of environmental problems, such as acid rain and haze weather. CO2emission reduction and NOx removal are desperately needed.Many studies show that the chemical absorption method is one of the most suitable technologies for large-scale CO2capture. In recent years, CO2capture using ionic liquids as absorbent has become a hot research field. Ionic liquids have a lot of advantages, which are suitable for CO2capture by chemical absorption, such as low volatility, stable property and adjustable structure. However, due to the high viscosity of ionic liquids, gas-liquid mass transfer process and absorption rate of CO2in ionic liquids is really slow and the absorption time is quite long, which are the practical application bottlenecks for CO2capture using ionic liquids. Previous research on complex solution for NO removal shows that the complexation rate between NO and complex solution is generally very fast and the complexation reaction is a process controlled by gas-liquid mass transfer. In summary, the key problem to be solved in the two chemical absorption processes is the same:intensification of the gas-liquid mass transfer in order to promote the chemical absorption is the key point of the development of chemical absorption method for decarbonization and denitration.Rotating packed bed (RPB) is a new type of multiphase flow mixing contactor and reactor, which could greatly strengthen the liquid-liquid, gas-liquid mass transfer. The technique has been successfully applied to the chemical separation process and the preparation of nanometer materials. In this paper, RPB, as a gas-liquid reactor, has been successfully applied to CO2capture and NO removal process. The CO2physical absorption and chemical absorption processes in ionic liquids in RPB have been studied and the mass transfer coefficient in RPB has been measured. New promising processes for CO2capture and for NO removal have been proposed. Based on the experimental research and the results of previous studies, a mathematical model for the process of CO2chemical absorption in ionic liquid under high gravity environment has been proposed. The gas-liquid mass transfer intensification mechanism under the high gravity environment has been researched and the operating parameters and equipment size have been optimized based on the model, which could provide support for the pratical application process. The main innovative works of this dissertation are as follows:1. CO2physical absorption process in traditional ionic liquid [Bmim][PF6] was used as a research system and the mass transfer coefficient of this system in RPB was measured. Mass transfer coefficient of this system in a packed column was also measured as a comparison study. The result of this comparison showed that under similar operating conditions, liquid volumetric mass transfer coefficient kL was0.95-3.9×l0-2s-1in RPB, while0.63-1.9×10-3s-1in the packed tower. Compared to traditional packed tower, liquid volumetric mass transfer coefficient in RPB could be increased by more than an order of magnitude and the absoption process has been effectively strengthened by RPB.2. The chemical absorption process of CO2in functional ionic liquid [Choline][Pro] was used as a research system. The CO2removal efficiency and absorbent capacity were investigated under different operating conditions. The results showed that in RPB, it took only0.2second to reach0.2mol CO2/mol IL at293K, indicating that RPB was kinetically favorable to the absorption of CO2in ionic liquid. The absorbent capacity could achieve25Kg CO2/m3IL (using10%mixed gas) and the removal efficiency could maintain over90%. The absorbent capacity could achieve40Kg CO2/m3IL using20%mixed gas. The method shows good prospect for practical application.3. The chemical absorption process of CO2in functional ionic liquid [Choline][Pro] was used as a gas-liquid mass transfer system. A model describing the gas-liquid mass transfer accompanying reversible reaction under high gravity environment was built based on the Higbie’s penetration theory. The analytical expression of CO2concentration in the liquid film with time and depth of penetration was obtained and the mass transfer coefficient in RPB could be further derived. The CO2removal efficiency under different operating conditions in RPB could be predicted and the predicted results were in good agreement with the experimental results. The model revealed that the gas-liquid mass transfer intensification in RPB was achieved by heightening concentration gradient of soluble gas in the liquid film. The effect of the packing radius size on CO2removal efficiency was predicted by this model. Then the absorbent capacity under different operating conditions could be improved by optimizing the packing radius size.4. FeII(EDTA) complexation absorbent was prepared using FeSO4and Na2EDTA crystalline hydrates and the NO removal experiments by complexation reaction in RPB were studied. The effect of high gravity level, gas-liquid flow rate ratio, gas-liquid flow rate, pH value of the complexation absorbent, temperature of the complexation absorbent, inlet gas pressure and NO concentration of the inlet gas on NO removal efficiency were investigated. The experimental results indicated that it was optimal for NO removal when the pH value of the complexation absorbent was7and the high gravity level in RPB was200g. The NO removal efficiency decreased with the increase of the temperature of the absorbent and the gas-liquid volume flow rate, while increased with the increase of the concentration of the absorbent and pressure of the inlet gas. When the concentration of the absorbent was0.04mol/L, the gas-liquid volume flow rate was125:1, the high gravity level in RPB was200g, the NO concentration of the inlet mix gas was1000ppm, the pressure of the inlet gas was0.35MPa and the temperature of the experiment system was298K, the NO removal efficiency reached the highest level95%.更多还原