生物膜滴滤床内温度及其分布特性对废气净化性能的影响

对不同温度下,陶瓷球填料生物膜滴滤塔净化低浓度有机废气的降解性能以及填料床内温度分布进行了实验研究,实验结果表明：填料床内微生物生长环境温度对微生物酶活性影响很大,从而造成温度对滴滤塔净化性能的显著影响.微生物酶活性最高时的温度为30℃,最高滴滤塔净化性能所对应的温度在30～40℃.在滴滤塔顺流操作条件下,滴滤床内温度沿气液流动方向升高;在进口碳源浓度一定时,滴滤床内沿气液流动方向的温升随着液体流量的减小和气体流量的增大而升高;废气进口浓度及系统操作方式对滴滤床温度分布也有显著影响.     

生物膜填料塔净化低浓度有机废气的动力学模型研究

为了开展生物化学法净化处理低浓度有机废气的理论及应用研究，针对生物膜填料塔建立了甲苯生化降解反应的动力学模型，对比验证的结果表明，模拟计算值与实验值之间有很好的相关性（相关系数Ｒ＞０．９６），故可利用这一模式由已知的操作参数对生物膜填料塔的净化效果进行预测。     

生物膜法净化低浓度硫化氢气体的试验研究

论述了采用生物膜填料塔净化低浓度Ｈ２Ｓ气体的可行性。研究表明：构成生物膜的脱硫杆菌对废气中低浓度Ｈ２Ｓ气体有很强的生化去除能力,生物膜填料对废气中的Ｈ２Ｓ的生化去除量可达９５．１ｇ／（ｍ３填料·ｈ）,而且当入口的Ｈ２Ｓ气体的浓度在２．３ｇ／ｍ３以下时,生物膜填料塔的净化效率在８８％以上。     

生物滴滤床净化挥发性有机物的研究进展

生物滴滤净化挥发性有机污染物技术是近年发展起来的一项新技术。文章介绍了生物滴滤技术的净化机理、净化效果的影响因素以及国内外研究现状。目前生物滴滤技术需要在以下几方面完善和发展:提高疏水性或难降解废气的处理能力,改进生物滴滤填料性能,提高对各运行参数的控制能力,加强实际废气的净化研究和完善生物滴滤模型。     

微生物烟气脱硫的生物膜系统动力学模型研究

为了研究生物滴滤塔净化废气中SO2的脱硫机制,文中应用Deep-Biofilm理论和微生物生长动力学方程Monod建立了生物膜脱硫系统的扩散-反应动力学模型,并结合平推流模型对整体塔器的脱硫过程进行了模拟。应用Matlab计算机编程语言对空塔停留时间、进口SO2质量浓度、填料比表面积、递增式进气和稳定式进气等因素对脱硫率的影响进行了数值模拟。与实验结果比较后发现模拟值和实验值吻合良好、日趋重合,证明了该模型的合理性,实现了微生物烟气脱硫技术实际脱除过程的模拟研究。     

低浓度苯乙烯废气生物净化过程的动力学模型验证

以生物膜填料塔净化处理低浓度苯乙烯废气的生物净化过程为基础,并依据“吸附—生物膜”理论建立的相关动力学模型,采用前期实验数据对苯乙烯的生物净化过程进行了对比验证,结果表明该模型的模拟计算值和实验值之间均有很好的拟合性,从而验证了该模型的正确性。     

生物滴滤塔净化处理硫化氢的实验研究

在常温条件下,以陶粒和悬浮改性填料WD-F10-4为填料的生物滴滤塔系统对硫化氢废气进行净化处理,考察了不同硫化氢负荷、营养液喷淋量和气体停留时间对生物滴滤塔性能的影响。实验结果表明,当进气质量浓度为400 mg/m3,硫化氢负荷为32 g/(m3·h),喷淋量为4 L/h,气体停留时间为46 s,系统的平均去除效率为97%。系统运行期间,填料未出现堵塞现象,证明悬浮改性填料可用作生物滴滤塔的填料。     

有机废气的生化处理实验研究

研究表明，采用国内现有微生物菌种挂膜接种的生物膜料塔净经低浓度有机废气是可行的，初步实验研究结果显示，增加人口气体甲苯浓度和气体流量，同时减小循环液喷淋量，可使甲苯的生化去除量增大，每升体积的生物膜填料对甲苯的生化去除量最大可达１５７．１３ｍｇ／ｈ。由实验结果推断，生物膜填料塔对废气中甲苯的净化去除过程属于传质控制过程，甲苯在生物膜内的降解为一级生化反应过程。     

错流式生物滴滤塔净化含硫化氢废气的研究

利用错流式水平生物滴滤塔对H2S进行脱臭实验,采用城市生活污水处理厂曝气池污泥进行接种挂膜。结果显示,H2S最大进气浓度可达1400 mg/m3,最大的体积去除负荷为144 g/(m3填料.h),对应的生物膜去除负荷为34.5 mg/(g生物膜干重.h),系统有较高的净化H2S废气能力。     

生物法净化低浓度甲苯废气装置及其操作特性

对生物法净化低浓度甲苯废气的适宜装置及其操作特性的研究表明,生物膜填料塔对低浓度甲苯废气的净化性能优于筛板塔及鼓泡塔;生物膜填料塔采用逆流并在液气比0.03～0.1、气速（30～60）m·h~(-1)的条件下操作时,低浓度甲苯废气净化效率可保持在90％以上．经实验验证,本生物膜填料塔对废气中甲苯的同系物同样具有净化作用．并且对再生胶厂、印刷厂、铸造厂、油漆厂等企业的实际生产废气也有良好的净化效果．     

Measurements and modeling of heat generation in a trickling biofilter for biodegradation of a low concentration volatile organic compound (VOC)

The experimental and theoretical heat generation behavior of a trickling biofilter treating toluene is discussed. The experimental results show that the temperature of the packed bed has a significant effect on the purification performance of the trickling biofilter and that an optimal operation temperature exists between 30 and 40 °C. During the gas–liquid co-current flow, the temperature in the packed bed gradually rises along the direction of the gas and liquid flow due to the exothermic biodegradation of toluene. The temperature rise between the inlet and outlet of the trickling biofilter increases with an increase in the gas flow rate and inlet toluene concentration. In addition, a larger liquid flow rate leads to a smaller temperature rise. The heat generation process occurring in the trickling biofilter is modeled by representing the packed bed as an equivalent set of parallel capillary tubes covered by the biofilm. The temperature profile in the packed bed during the liquid–gas co-current flow is analyzed by simultaneously solving the problem of gas–liquid two-phase flow and heat and mass transfer through the liquid film and biofilm. It is shown that the model agrees well with the experimental data, predicting the variations of the temperature rise between the inlet and outlet of trickling biofilter with the increasing gas and liquid flow rates.     

Onset of pulsing in gas-liquid trickle bed filtration

When liquid suspensions containing low concentration of fine solids are treated in catalytic packed bed gas-liquid-solid reactors, which are operated in trickle flow or near the transition between trickle and pulse flow, plugging develops and increases the resistance to two-phase flow. Also due to obstruction, such accumulation of fines in the catalyst bed shifts progressively the flow pattern from trickling to pulsing flow. The progressive onset of pulsing flow along the packed bed was estimated using a sequential approach based on combining a “large time-scale” unsteady-state filtration solution of two-phase flow with a “short time-scale” solution of a linear stability analysis of two-phase flow. Space-time evolution and two-phase flow of the deposition of fines in trickle bed reactors under trickle flow regime was described using a one-dimensional two-fluid model based on the volume-average mass and momentum balance equations and volume-average species balance equation for the fines. The model hypothesized that plugging occurred via deep-bed filtration and incorporated physical effects of porosity and effective specific surface area changes due to the capture of fines, inertial effects of phases, and coupling effects between the fines filter rate equation and the interfacial momentum exchange force terms. The transition between trickle flow and pulse flow regimes was described from a stability analysis of the solution of the transient two-fluid model around an equilibrium state of trickle flow under pseudo steady state conditions. The impact of liquid superficial velocity, viscosity and surface tension, gas superficial velocity and density, feed fines concentration, and fines diameter on the transition between trickle and pulse flows in the presence of fines deposition was analyzed.     

EFFECT OF NATURAL CONVECTION ON MASS TRANSFER BETWEEN SOLID PARTICLES AND FLOWING FLUIDS IN PACKED BEDS

Mass transfer between solid particles in a packed bed and a flowing fluid in laminar flow region, where both forced and natural convection are important, was analyzed theoretically. The diffusion equation based on the free surface model proposed by Happel was solved and an approximate solution relating the average Sherwood number to the Peclet number, the Rayleigh number and the void fraction of a packed bed was obtained. The published experimental mass transfer data in packed beds were found to agree well with the theoretical predictions.     

Turbulence modelling of multiphase flow in high-pressure trickle-bed reactors

Computational fluid dynamics (CFD) has been used as a successful tool for single-phase reactors. However, fixed-bed reactors design depends overly in empirical correlations for the prediction of heat and mass transfer phenomena. Therefore, the aim of this work is to present the application of CFD to the simulation of three-dimensional interstitial flow in a multiphase reactor. A case study comprising a high-pressure trickle-bed reactor (30 bar) was modelled by means of an Euler-Euler CFD model. The numerical simulations were evaluated quantitatively by experimental data from the literature. During grid optimization and validation, the effects of mesh size, time step and convergence criteria were evaluated plotting the hydrodynamic predictions as a function of liquid flow rate. Among the discretization methods for the momentum equation, a monotonic upwind scheme for conservation laws was found to give better computed results for either liquid holdup or two-phase pressure drop since it reduces effectively the numerical dispersion in convective terms of transport equation.After the parametric optimization of numerical solution parameters, four RANS multiphase turbulence models were investigated in the whole range of simulated gas and liquid flow rates. During RANS turbulence modelling, standard k-ε dispersed turbulence model gave the better compromise between computer expense and numerical accuracy in comparison with both realizable, renormalization group and Reynolds stress based models. Finally, several computational runs were performed at different temperatures for the evaluation of either axial averaged velocity and turbulent kinetic energy profiles for gas and liquid phases. Flow disequilibrium and strong heterogeneities detected along the packed bed demonstrated liquid distribution issues with slighter impact at high temperatures.     

旋转填料床气液两相流场的仿真分析

通过合理简化旋转填料床(RPB)结构,建立了三维物理模型,利用商用软件Fluent的计算平台,采用欧拉两相流模型和多孔介质模型对旋转填料床内的气液两相流场进行了仿真分析,深入分析了其压力场分布和速度场分布,并在此基础上对比了气相压降随旋转床转速变化的仿真结果与实验结果,两者变化趋势一致,表明所建立模型能近似地模拟旋转填料床的流场分布,并指导理论研究和实验研究进一步深入。     

Optimization and simulation of the Sabatier reaction process in a packed bed

The Sabatier reaction in a testing packed bed was investigated experimentally and theoretically, and was used to convert waste carbon dioxide and hydrogen to provide needed water for closing the life‐support loop on orbit in space. A three‐dimensional model including fluid flow, gas dispersion, heat and mass transfer, and chemical reaction was developed by coupling some semi‐empirical correlated equations in chemical engineering science into computational fluid dynamics theory. Good agreements between the simulating results and experimental data for the effect of some parameters on reaction verified this model, for example, heat exchange between reactor and atmosphere, the material property of reactor, the catalyst deactivated and gas mass flux and so on. By using this model as the designing tools, an optimized packed bed is proposed. Compared with the testing packed bed, the relevant reactor length can be reduced from 220 to 150 mm with the same hydrogen conversion and lower pressure drop. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2879–2892, 2016     

Pressure drop hysteresis in trickle bed reactors

An understanding of the hydrodynamics of trickle bed reactors (TBR) is essential for their design and prediction of their performance. Flow variables, packing characteristics, physical properties of fluids and operation modes influence the behavior of the TBR. The existence of multiple hydrodynamic states or hysteresis (pressure drop, liquid holdup, catalyst wetting, gas-liquid mass transfer) is due to the different flow structures in the packed bed and can be attained by a set of different operating procedures. Experiments were performed to study the effect of liquid and gas velocity, liquid surface tension, liquid viscosity and the particle diameter of the packing on two-phase pressure drop hysteresis. The parallel zone model for pressure drop hysteresis in the trickling flow was used for analysis of experimental data and flow structure. Theoretically predicted pressure drop hysteresis loop is in satisfactory agreement with experimental data.     

Application of Magnetic Resonance Imaging (MRI) for investigation of fluid dynamics in trickle bed reactors and of droplet separation kinetics in packed beds

Magnetic Resonance Imaging technique was used to investigate the fluid dynamics of multiphase flow in two different applications: (a) stationary two-phase flow in trickle beds, and (b) time-dependent droplet separation in granular bed filters. The experiments were carried out with different gas/liquid systems at either atmospheric conditions or at elevated pressure and temperature. Two-dimensional and three-dimensional image data were then evaluated to quantify the porosity profiles and gas/liquid distribution in packed beds. The results compare well with data from integral measurements.     

基于离散相模型的旋转填充床内的流场分析

利用CFD软件Fluent初步模拟了旋转填充床(Rotating Packed Bed,RPB)内的流体流动.计算中气相采用RNGk-ε湍流模型,液相采用拉格朗日离散相模型(DPM).通过一定简化后建立了旋转填充床二维模型,考察了液体颗粒在填充床内的速度分布,以及转速对液体颗粒速度的影响.结果显示液滴速度随转速的增加而增加,转速对液滴径向速度的影响不大.此外还针对转速、气体进口速度对干床压降的影响做了一定的研究,发现压降随转速的增加而增加,但其影响没有气体进口速度对压降的影响明显.填料的内缘处存在剧烈的端效应,模拟结果表明,端效应区的湍动强度明显大于其他区域.