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单乙醇胺水溶液化学吸收CO_2的研究 总被引:2,自引:1,他引:2
有机胺水溶液化学吸收CO2在工业上广泛应用,对其传质过程的微观机理进行研究十分必要。文中以对流扩散方程为基础,考虑了界面阻力对传质的影响,建立了带有化学反应的气液吸收过程液相侧非稳态传质模型,得到了传质系数表达式。利用激光全息干涉仪对不同液相主体流速下单乙醇胺(MEA)水溶液化学吸收CO2过程进行了实验研究,测定了传质达到稳态时的液相侧近界面浓度、浓度边界层厚度和传质系数。结果表明:随着液相主体流速的增加,近界面浓度和浓度边界层厚度减小,而传质系数增大;MEA在水溶液中的质量分数由0.1%增大到0.2%时,CO2吸收过程达到稳态时的近界面浓度、浓度边界层厚度及传质系数均增大。传质系数模型计算值与实验值吻合良好。 相似文献
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以分子热力学为基础 ,对气体吸收过程进行了理论分析 ,导出了传质通量的数学表达式。根据该文分析 ,气液界面传质的源动力来自界面处气液两相的不平衡 ,即只要有传质发生 ,液相界面处的浓度就不会达到与气相呈平衡的浓度。对于气相阻力可以忽略的吸收过程 ,两相传质速率的大小主要取决于液相的溶质界面浓度和液膜厚度 ,影响溶质界面浓度和液膜厚度的主要因素是近界面液相侧的流场分布。利用近界面浓度与液膜厚度的激光测定结果 ,计算了甲醇、乙醇及正丙醇吸收CO2 气泡的传质通量 ,计算结果与实验值吻合良好 相似文献
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针对气体吸收过程,以分子热力学为基础,结合普遍化的化学势推动力通量方程,导出了传质存在时两相界面处的浓度关系,并针对不同情况进行了求解.提出了一个反映液相侧动力学状况的无因次数群Biot数Yo,Yo数越大界面处两相越偏离平衡.界面浓度是与Yo和液相主体浓度密切相关的.对于气相阻力可以忽略的吸收过程,两相传质速率的大小主要取决于液相的溶质界面浓度和液膜厚度.采用激光显微全息干涉技术对甲醇,乙醇,正丙醇静止吸收CO2时的界面浓度进行了测定,试验结果表明了本研究模型的正确性. 相似文献
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O. Sitnai 《Chemical engineering science》1982,37(7):1059-1066
Simulated pressure gradient records, based on the theoretical pressure field around a bubble in fluidized bed derived by Davidson, are analysed by statistical methods to determine significant bubble parameters. It is shown that from two records measured by two pairs of pressure differential probes located on common vertical axis the following can be computed: bubble velocity, bubble depth (diameter), vertical spacing of bubbles, bubbling frequency, distributions of bubble sizes and spacings, and local bubble phase fraction. Simulated and actual records of the passage of non-interacting single bubbles over four pairs of probes located in a fluidized bed with internals show good agreement. 相似文献
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The local hydrodynamic properties of the gas phase in an internal-loop airlift reactor were investigated in this study. The hydrodynamic properties including gas holdup, bubble velocity and bubble chord length were measured by dual electrical resistivity probes. The chord length distribution was then transformed to the bubble size distribution by modeling the bubbles as ellipsoids. It was found that the gas holdup increased with decreasing bubble velocity. In addition, most bubbles tended to rise along the riser central axis. Thus, the gas holdup in the axis was higher. The bubble size, bubble velocity and gas holdup were relatively constant in the axial direction of the riser except in the zones near the gas sparger and the gas–liquid separator. The bubble velocity became slower when the bubbles approached the gas–liquid separator. Moreover, the bubble size and bubble velocity for the three-phase system were relatively insensitive to the radial direction compared to those for the two-phase system. It was also found in this study that the bubble rise velocity and bubble size for the three-phase system were lower than that for the two-phase system. However, the gas holdup for the three-phase system were higher than that for the two-phase system due to bubble breakage caused by the solid particles. 相似文献
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利用高速摄像机拍摄顶部浸没竖直向下管口气泡膨胀及脱离演变过程,对比分析管径、平均气速对气泡尺寸、形成时间的影响规律。引入泡龄k表征管口气泡位置特性,用椭球形气泡长短轴比L表征气泡形状特征。研究发现,气泡生成机理有间歇生成气泡、含抽吸间歇生成气泡和连续生成气泡3种;气泡脱离直径随平均气速变化过程明显存在气泡脱离形态转变点;气泡膨胀脱离模式随平均气速变化分为单个气泡形成、气泡聚并形成两种。平均气速为3.1 m·s-1时管口处存在抽吸现象,此时最大泡龄kmax最小;脱离阶段气泡长短轴比L随脱离时间变化过程明显存在时间分界点。在分界点前,L值在2.0附近波动,气泡主要以椭球形存在。分界点后,L值明显增加,气泡形状向扁椭球体发展。 相似文献
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Approximate solutions of the shape function and the electrophoretic movement of a bubble in an aqueous medium with ionized detergent and a small number of electrolytes under the influence of uniform electric field are derived. Specifically, a bubble that has the interface saturated and densely packed with detergent molecules is considered, and the charges were deemed to be fixed provided the position change among the detergent molecules is hindered relative to the free molecule. The surface tension at the interface is weakened with the addition of the detergent, and the deformation can be significant. The variation of the shape of the bubble was represented by the Legendre polynomial and the perturbed velocity profile was used to derive the drag force for the deformed bubble. The speed and size of the bubble was assumed to be very small so that the flow around it is in the creeping flow regime. The shape of the bubble with fixed surface charge undergoes a prolate deformation with axial symmetry around the axis parallel to the direction of the electric field and exhibits asymmetry with respect to the plane that goes through the center of the bubble and is perpendicular to the axis. But this asymmetry is not significant unless the surface charge density and the electric field are very large. Only symmetric deformation governs the movement, and, consequently, the drag force is not dependent on the sign of surface charge. As the bubble becomes more slender with deformation, the movement is enhanced. 相似文献
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Approximate solutions of the shape function and the electrophoretic movement of a bubble in an aqueous medium with ionized detergent and a small number of electrolytes under the influence of uniform electric field are derived. Specifically, a bubble that has the interface saturated and densely packed with detergent molecules is considered, and the charges were deemed to be fixed provided the position change among the detergent molecules is hindered relative to the free molecule. The surface tension at the interface is weakened with the addition of the detergent, and the deformation can be significant. The variation of the shape of the bubble was represented by the Legendre polynomial and the perturbed velocity profile was used to derive the drag force for the deformed bubble. The speed and size of the bubble was assumed to be very small so that the flow around it is in the creeping flow regime. The shape of the bubble with fixed surface charge undergoes a prolate deformation with axial symmetry around the axis parallel to the direction of the electric field and exhibits asymmetry with respect to the plane that goes through the center of the bubble and is perpendicular to the axis. But this asymmetry is not significant unless the surface charge density and the electric field are very large. Only symmetric deformation governs the movement, and, consequently, the drag force is not dependent on the sign of surface charge. As the bubble becomes more slender with deformation, the movement is enhanced. 相似文献
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The flow fields surrounding two parallel moving bubbles rising from two identical orifices submerged in non-Newtonian fluid of carboxymethylcellulose (CMC) solution of three different mass concentration were measured experimentally by the use of particle image velocimetry (PIV). The influences of gas flowrate, solution mass concentration, orifice interval and the angle between two bubble centers line and vertical direction on the flow field surrounding bubbles were discussed respectively by analyzing the velocity vector, velocity contours as well as individual velocity components. The results show that the liquid velocity both in front of two bubbles and behind increases with gas flowrate duo to shear-thinning effect of previous bubbles, whereas decreases with the increase of CMC concentration due to the increase of drag force acting on bubbles. The effect of the orifice interval on the flow field around two moving bubbles becomes gradually obvious as the interval becomes closer. Moreover, two adjacent side-by-side bubbles repulse each other during rising, leading to the practical interval between them increased somewhat above the orifice interval. When the distance between bubbles is less than the orifice interval l0 mm, the interaction between two neighboring bubbles changed from mutual repellence to attraction with the decrease of the angle of the line of linking two bubble centers to the vertical direction. 相似文献
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The charge density distribution around a rising bubble in a two-dimensional fluidized bed was measured using eight induction probes flush with the outside wall of the column and connected to charge amplifiers for recording induced charge signals as bubbles passed by. The charge distribution surrounding the bubble was reconstructed using an iterative linear back projection (LBP) algorithm by assuming that the bubble is symmetrical and the charge around the bubble remains constant as the bubble rises. The results showed that the emulsion phase far from the bubble in a two-dimensional fluidized bed of glass beads was charged negatively, and the charge density decreased gradually toward the bubble-dense phase interface, with a nearly zero charge density inside the bubble. The effects of the number of probes are also investigated. The reconstructed results using both simulated charge distribution and experimental data for different numbers of probes of the same probe diameter of 3 mm showed that increasing the number of probes can improve the reconstruction resolution. The addition of one or two more probes outside the bubble path also increased the reconstruction resolution in the region outside the bubble. 相似文献
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Analytical investigation of liquid Reynolds stress in shear bubbly flow with intermediate Reynolds numbers is absent. In this paper, the velocity field around a sphere bubble in linear shear liquid is assumed to be the linear superposition of the velocity field of uniform liquid passing a sphere bubble and the linear shear velocity field. The formula of shear liquid Reynolds stress was derived by averaging the velocity field in the cell-ensemble averaging method, and the formula was corrected under conditions of intermediate Reynolds number. The formula was compared with that of Sato, and the predicted results of local liquid velocity of the fully developed upward bubbly flow in pipes were compared with the experimental data. The results show that the formula is valid and accurate in prediction. 相似文献
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This paper deals with the study of the vigorous particle mixing around an artificial bubble injected in a fluidized bed using a hot film anemometric technique.The fluctuations of the heat transfer coefficient have been studied as a function of the bubble characteristics and position with respect to the probe.In the bubble injection axis the heat transer coefficient depends very much on the bubbling frequency but only slightly on the bubble diameter. On the other hand, the distance x between the transfer surface and the bubble track was found very important. In this study we also determined the critical values of the bubble diameter and frequency which characterize the beginning of interaction between two successive bubbles.We propose a velocity potential model so as to take into account the form of the agitation zone of particles around the bubbles. 相似文献