海水脱硫散堆填料塔的数值模拟及传质计算

采用体积平均法建立了描述散堆填料塔内气、液两相的流动模型;在双膜理论的基础上建立了平均体积传质模型。通过数值计算,获取了在不同液气比下塔内流体速度、孔隙率分布、压力分布及脱硫效率,并就压力损失和脱硫效率与实验值进行了对比,预测值与实验值吻合较好,趋势完全一致。分析填料塔内海水的速度分布矢量图和填料塔中间高度断面上的速度分布图发现,靠近壁面处存在着显著的壁流现象,并在沿流方向上液体有向壁区积聚的趋势,壁流现象变得更严重。由3种填料径向孔隙率分布图可看出,近壁面处的孔隙率明显高于中间区域,表明这是形成壁流的原因所在。     

大型填料塔内液相分布状态的研究

本文针对填料塔内液体运动的分散方程,提出了新的边界条件,并得到描述填料塔内液体运动规律的新模型.通过实验确定了模型中的各参数.实验结果与理论模型的比较,两者吻合较好.用激光- 光导纤维测试系统测定了液体在填料层内的平均停留时间分布,作出了塔内液体的等平均停留时间曲线,并进一步分析了液体在填料塔内的流动特性.     

海水脱硫散堆填料塔的流体力学计算

采用体积平均法建立了描述散堆填料塔内气、液两相的流动模型；通过数值计算，获取了在不同液气比下塔内流体速度、孔隙率分布及压力分布，并就压力损失与实验值进行了对比，预测值与实验值吻合较好，趋势完全一致。分析海水速度分布图发现，靠近壁面处存在显著的壁流现象，并在沿流方向上液体有向壁区积聚的趋势，壁流现象变得更严重。由3种填料径向孔隙率分布图可看出，近壁面处的孔隙率明显高于中间区域，这是形成壁流的原因所在。     

气液两相逆流状态下金属板波纹填料塔内液体流动分布

填料塔内液体流动分布状况直接关系到塔内气液两相的有效接触,影响塔的操作性能.由于液体分布不良,造成填料塔内局部区域的气液比与全塔宏观的气液比有显著差别,从而大大降低塔的总传质效率.因此,填料塔内的液体分布     

气液两相逆流状态下金属板波纹填料塔内液体流动分布

<正>填料塔内液体流动分布状况直接关系到塔内气液两相的有效接触,影响塔的操作性能.由于液体分布不良,造成填料塔内局部区域的气液比与全塔宏观的气液比有显著差别,从而大大降低塔的总传质效率.因此,填料塔内的液体分布     

连续泡沫分离塔回收水溶液中钼(Ⅵ)的研究

以十六烷基三甲基氯化铵为表面活性剂,在连续稳态操作条件下,研究了泡沫塔和填料泡沫塔回收水溶液中微量Mo(Ⅵ)的分离性能。结果表明:随鼓泡区高度的增加,泡沫塔的富集率逐渐增加,回收率逐渐减小;随填料层高度的增加,填料泡沫塔的回收率增加,富集率减小;随泡沫层高度的增加,两种塔的富集率均逐渐增加,回收率均逐渐减小。泡沫塔内的浓度分布基本一致,表明泡沫塔存在较大的液相返混,填料泡沫塔内浓度分布随填料层高度的增加而增大,表明填料泡沫塔的液相返混程度较泡沫塔小。填料的加入有效增大了气液传质面积,提高了气液传质速率。填料泡沫塔的回收率远高于泡沫塔,但富集比略有下降。在实验条件范围内,填料泡沫塔中Mo(Ⅵ)的回收率可达99.8%,富集率可达12.2。     

等几率并螺旋填料塔的研究

为解决了高效填料塔的放大效应问题,研制了等几率并螺旋填料塔,其具有传质效率高、压降低的特性,集成毛细管气液分配器使填料塔内液体初始分布均匀,克服了高效填料塔的壁流效应。2-甲基丁醇和3-甲基丁醇的工业化分离实验表明,该填料塔不存在放大效应,可用于难分离物系的精馏。     

工业规模板波纹填料床层的液体分布

采用φ480mm,高6 m的工业规模有机玻璃填料塔,以空气-水为实验物系,测试了250 Y型金属孔板波纹填料床层的液体分布.空塔气速和液体喷淋密度的测试范围分别为0.677～2.062m/s和27.37～109.2m3/(m2·h).结果表明,液速和气速的改变均不会对床层液流分布造成较大的影响,而壁流量受塔内气液流动的影响较大.     

规整填料塔的壁流研究

以新的观点分析了填料塔内壁流产生、发展且最终达到平衡的过程。通过数学推导，得到了一个三参数壁流模型，并在实验基础上，进行模型的参数估计，从而求得了八种规整填料的壁流曲线。研究认为，壁流量的大小是填料塔内诸多因素综合影响的最终结果，而填料自身的几何形状和加工精度，是其中最重要的影响因素。通过实验，测取了这些填料的平衡壁流量，其中某些大于４８％。     

鲍尔环在我厂脱碳装置上的应用

催化热钾碱法脱除氨合成气中CO_2,由于其净化度要求高,溶液较易发泡,目前国内外仍广泛采用性能比较稳定、操作可靠的填料塔作为气-液接触设备。 传统的拉西环填料,由于其填料空隙率较低,流体阻力较高,泛点速度较低,加之在拉西环填料塔内易使喷淋液在塔内形成沟流并流向塔壁,从而降低了塔的处理能力。因此,近     

微型流化床反应器液相冷态进样停留时间分布模拟与实验

为了得出气、液相流量变化对微型流化床反应器液相停留时间的影响规律,借助Fluent软件对反应器内部流场进行数值模拟,得到其速度、压力分布特性和反应器出口液相浓度的变化曲线。采用示踪剂侧面脉冲进样法,实验测定了反应器中液相的停留时间分布。结果表明,气相流量和液相流量均对液相停留时间有明显的影响,气、液相流量为4¹0L/h时,液相平均停留时间可以控制在1.1110L/h时,液相平均停留时间可以控制在1.11¹.89s;气、液相流量的增加均会导致液相停留时间的减少,但气相流量对停留时间的影响要大于液相流量对液相停留时间的影响。数值模拟与实验数据对比分析发现二者结果吻合良好,模型可用。     

Experimental study and CFD numerical simulation of an innovative vapor splitter in dividing wall column

The vapor split ratio (R_V) adjustment plays an important role on energy efficiency during dividing wall column (DWC) operation. In order to achieve active control of R_V, this aticle presents an innovative vapor splitter driven by hydraulics. The vapor flows into main tower from prefractionation section through the rectangle hole located at the end of the partition. Vapor splitting is implemented by the change of flow resistance at the rectangular hole caused by adjusting the liquid level on the bottom plate. This design makes full use of the hydraulic properties in DWC, employing simpler construction with single tunable parameter. Numerical simulations and laboratory tests were both carried out to validate its performance in the DWC with a diameter of 600 mm. The results demonstrate that the desired R_V can be handled effectively in the approximate range from 0.5 to 2, basically satisfying the industrial demand for the gas distribution.     

The flow pattern of solids in a gravity column

Flow pattern of solids in a gravity column (150 mm diam.) with peripheral discharge was studied by measuring the residence time distribution (RTD) of coloured solids tracer in the exit stream. The data were used to calculate dispersion numbers and flow volumes by applying a dispersion model and a multiparameter model respectively. The results show that the flow pattern of solids in the upper 75% of the column height was plug and that this flow pattern was virtually unaffected by the flow rate in the range investigated (35 – 75 g/s millet seed). The flow pattern of the solids in the bottom section of the column is shown to be markedly mixed and to depend on the flow rate. The paper also notes the usefulness of RTD analysis in providing flow models of bulk flow equipment which can give supplementary design and operating information not available by traditional methods.     

小型气-液-固流化床液相的停留时间分布

采用脉冲示踪技术,研究了3 mm床径的小型气-液-固流化床内液相停留时间分布。以KCl为示踪剂,液相为去离子水,气相为空气,固相为平均粒径0.123~0.222 mm的玻璃微珠和氧化铝颗粒,测量流化床出口液相的电导率,得到其停留时间分布曲线。结果表明,增大表观液速和表观气速,分布曲线变窄,平均停留时间缩短,Peclet数增大;固相的存在使液相的平均停留时间增长。表观液速1.96~15.70 mm×s^-1,表观气速1.18~1.96 mm×s^-1的条件下,流动接近层流;平均停留时间的范围为（19.6±0.34）s~（48.0±0.92）s,建立的Pe经验关联式对实验结果有较好的预测,偏差在±25%以内。研究结果对于小型三相流化床的设计放大具有指导意义。     

Cold flow studies of a slurry transport reactor-hydrocyclon system

The fluid dynamics of a new reaction system composed of a slurry transport reactor-hydrocyclon were studied using two column diameters at different gas and liquid linear velocities. The cold models used a gas collector in the top that allowed measurement of the gas disengaged by radial zones and a conductimetric probe that measured the frequency of the bubbles exiting from the top of the reactor. Gas and liquid hold-ups were determined. Liquid and solid tracers were also employed to determine the resident time distribution (RTD), global residence time, and the recycle of slurry near the wall. The results show the effect of sparger and disengaging design, as well as the effect of gas and liquid flow rate on the radial and axial gas hold-up profiles and on the recycle of slurry by the wall. This recycle is similar to those observed with a draft tube. No significant effect of column diameter was observed. A smooth circulation of slurry and solid was achieved through a mechanical optimization of the inlet and outlet of the reactor. It was demonstrated that the RTD of the system can be simulated using a set of continuous stirred tank reactors and plug flow reactor in a recycle (three parameters). Empirical equations are proposed for predicting the hold-up and the three parameters needed by the model. The similarity to a spouted bed reactor is discussed.     

Structured reactors for enzyme immobilization: advantages of tuning the wall morphology

A new high-porosity mullite advanced ceramic material (ACM) having an open pore structure on the micron length scale was evaluated as a monolithic support for enzyme catalyzed reactions. The hydrodynamic properties of ACM monoliths were investigated using residence time distribution (RTD) in gas–liquid Taylor flow and compared with classical cordierite monoliths. The hydrodynamic results show that the liquid phase accesses the entire open volume of the wall and exchanges rapidly with the bulk liquid in the channels. The ACM monoliths were functionalized with polyethylenimine (PEI) and with carbon prepared by different methods in order to provide adsorption sites for lactase from Aspergillus oryzae and lipase from Candida rugosa. These monolithic biocatalysts were tested for activity and stability and compared to similarly prepared biocatalysts employing classical cordierite ceramic monoliths. The use of high-porosity ACM monoliths leads to more stable and more active structured bioreactors. The highly open microstructure of ACM affords good access to catalysts deposited within the walls of a monolith and enables high enzyme loadings.     

Residence time and conversion in the extrusion of chemically reactive materials

Twin‐screw extruders offer improved control of the residence time distribution (RTD) and mixing in materials such as plastics, rubber and food. Based on the flow and the heat transfer characteristics obtained for a self‐wiping, co‐rotating twinscrew extruder, the residence time and chemical reaction are studied by tracking the particles. For normally starve‐fed twin‐screw extruders, the length of the completely filled section is calculated as function of the process variables using the coupling of the flow with the die. With a model of the solid conveying section, the RTD for the whole extruder is calculated for corn meal at different screw speeds and flow rates. The calculated variation of RTD with the screw speed and the flow rate yields good agreement with observations from many experiments. The variation of the fully filled section length, chemical conversion and mixing effectiveness are also obtained under different operation conditions. Most of the results are in qualitative agreement with experimental results and may be used as guidelines for extruder design and determination of optimal operating conditions.     

Liquid phase residence time distribution for two phase flow in coiled tubes

The residence time distribution (RTD) of the liquid phase in air-water flow through helical coils has been studied. Upward and downward cocurrent flows have been investigated in three coils with curvature ratios ranging from 11 to 60.7. The ranges of the Reynolds numbers for the gas and the liquid varied from 1500 to 3000 and 620 to 3200, respectively. A model has been proposed that describes the liquid phase RTD as combination of two different residence time distributions applicable for turbulent and laminar liquid flows.     

Estimation of liquid phase mixing due to solids in a turbulent bed contactor

The mixing in two-phase gas-liquid and three-phase gas-liquid-solid system (turbulent bed contactor) is evaluated through residence time distribution (RTD) studies in terms of Peclet number. RTD experiments are conducted for various gas and liquid velocities, and number of stages for two- and three-phase systems. Since the mean residence time is very short in both the systems, a mixed flow tank with exponential decay RTD is used in series. After deconvolution, the RTD of the system is obtained. The experimental RTD curves are satisfactorily compared with the axial dispersion model and Peclet numbers are evaluated for all the experiments. The axial dispersion coefficients are calculated from Peclet numbers. With this study, it is thought that liquid phase mixing may be controlled by changing the quantity of solid particles in the bed.     

Experimental study on pressure drops in a dividing wall distillation column

Previous studies in the fields of process design and process control [1] have shown the potential benefits that can be achieved through the implementation of thermally coupled distillation sequences, in particular, the dividing wall distillation column. The dividing wall distillation column meets important goals of process intensification, including energy savings, reduction in carbon dioxide emissions and miniaturization. In this paper, an experimental study on the hydrodynamic behavior of a dividing wall distillation column is presented. Several different values for gas and liquid velocities were tested in order to measure pressure drops and identify operational regions; the air/water system was used as the basis for the experimental setup. Results regarding pressure drops (fitted to the model of Stichlmair et al.) provide operational limits for the operation of the packed dividing wall distillation column. According to the results, the experimental dividing wall column can be operated at turbulent regime that is associated to proper mass transfer.