【作者】 沈树华；

【导师】 马友光；

【作者基本信息】 天津大学 ， 化学工程， 2007， 硕士

【摘要】 提高气液两相传质效率是化工过程强化的一个重要内容，本文就分散相颗粒对气液传质的增强机理进行了研究。在恒温搅拌釜内，对CO2在分散相颗粒与水形成的浆料体系中的吸收进行了实验研究。在起始压力101325-162120pa，温度290.15K308.15K，转速14s¹下，考察了固体颗粒含率、转速、超声与未超声、实验温度及起始压力对吸收速率的影响。实验结果表明：活性炭颗粒对CO₂的吸收具有明显的增强作用并且呈现一定的规律性，即在其含量为01kg·m^-3下，增强因子随活性炭颗粒含量的增加由起始段的显著增加至趋于恒定；在颗粒含量一定的条件下，增强因子随转速的增大而减小；经过超声后的体系较未超声时增强；增强因子随温度的变化影响不大；增强因子随起始压力的增大显著增大；其它颗粒对CO2的吸收均表现为降低作用。考虑到发生在近界面连续相内的传质，根据经典传输机理和表面更新理论，通过对传质区进行区域划分，从一维角度建立了非稳态非均相传质的二区模型。借助Laplace domain变换（S = P），得到了增强因子的解析式，分析讨论了相关参数对增强因子的影响,可用于实际增强因子的预测。由于经典机理具有一定的局限性，本文从界面非平衡理论出发，提出了新的机理，在此基础上，根据基本传质方程导出了添加及未添加颗粒时气液界面的传质速率，得到了增强因子的理论预测模型。针对不同转速范围，采用不同的传质理论，得到了相应增强因子的具体表达式。针对添加分散颗粒引起的增强作用，提出了两种不同的控制机制：表面-吸附控制机制及表面-更新控制机制。上述两个独立模型中，一维非稳态非均相模型能很好的解释低颗粒含量、低转速下，颗粒含量及转速与增强因子的关系，而界面非平衡模型不仅能很好的解释低颗粒含量、低转速下的实验现象，而且能很好的解释高颗粒含量、高转速下的转速与增强因子的关系。两个模型均可得出增强因子的解析表达式，并且对低转速下的实验数据均能很好的吻合。更多还原

【Abstract】 The enhancement of gasliquid mass transfer is of central importance in theintensification of chemical engineering process. In this paper, the enhancementmechanism of gasliquid mass transfer with the dispersed particles was studied.The experimental investigations of carbon dioxide absorption in the slurriescontaining activated carbon and water had been carried out in the thermostaticreactor. The influence of particle concentration, stirrer speeds, ultrasonic dispersion,temperature and initial pressure on enhancement factor under the condition of theinitial pressure range from 101325pa to 162120pa, temperature varied between290.15K and 308.15K and stirrer speeds from 1 to 4 rounds per second had beeninvestigated experimentally. The results showed that the activated carbon had anobvious enhancement on carbon dioxide absorption in aqueous phase and its effectsdisplayed certain regulation that the enhancement factor notably increased duringbeginning period and consequently slowly raised to level off and gradually reached aconstant value with an increase of the solid loading within the range of zero to onekilogram per cubic meters. The enhancement factor reduced with increasing of thestirrer speeds. The system under ultrasonic dispersion appeared a remarkableenhancement comparing with the one without ultrasonic dispersion. Temperature hadlittle influence on enhancement factor while the initial pressure behaved a positiveact to the enhancement factor. All other kinds of particles used in this work had anegative effect on gas absorption rate.In view of the mass transfer happened near the interface, an one dimensionalnonsteadyheterogeneous mass transfer model was proposed according to thepartition of mass transfer region in which the shuttle effect mechanism and surfacerenewal theory were employed. An approach for enhancement factor had beenderived by means of Laplace domain transform and the influences of relativeparameters on enhancement factor were also discussed. The model presented couldbe applied to the prediction of enhancement factor in practical process.Due to the limitation of the classical theories in application range, a novelmodel based on interfacial nonequilibriummechanism had been proposed, and the absorption rate with and without the dispersed particles had been derived from thefundamental mass transfer equation, as well as the expression of enhancement factor.Considering the various ranges of stirrer speeds, different theories of mass transferled to different expressions of enhancement factor. Two different control regimes hadbeen put forward for the influence of the dispersed particles on enhancement factor:surfaceadsorption-control regime and surfacerenewal-control regime.In the two models mentioned above, one dimensional nonsteady heterogeneousmodel could well be applied to elucidate the relation between enhancement factorand solid loading as well as stirrer speeds under lower solid loading and stirrerspeeds, while the interfacial nonequilibrium model not only could be employed toexplain the relation above, but could also explain the relation between enhancementfactor and stirrer speeds under higher solid loading and higher stirrer speeds. Both ofthe two models could obtain the prediction equation of enhancement factorrespectively, and the predicted values agree well with the experimental data underthe condition of lower solid loading and stirrer speeds.更多还原