好氧发酵过程微界面传质耦合模拟分析

微生物好氧发酵过程是一个多相生化反应体系,空气中的氧在气液两相间的传质速率对生化发酵过程有重要影响。而气泡中氧的传递特性是气泡的形态、运动及体系温度、压力和物性综合影响的结果。通过建立两组分空气气泡上升及其氧传质耦合模型,进而采用数值模拟描述好氧发酵体系中微界面体系的强化效果。利用能量耗散理论评价制造微气泡体系的能耗,以获得高性价比的气泡形态和较高的氧利用率。计算结果表明,在预设的工况下,液面高度一定的反应器内,初始半径大于500μm的气泡会在短时间内逸出体系,造成物料浪费;而气泡初始半径小于100μm时,其停留时间、传质效率和氧利用率会显著提升。小气泡的生成需要较大的能耗,需要综合生产成本考虑。在不考虑其他因素影响的情况下,体系中的DO值如果维持在20%～30%,可以获得最大的氧气传质速率。     

自然循环窄矩形通道内过冷沸腾两相摩擦阻力特性

采用去离子水作为实验工质,在低压低流速自然循环工况下开展了单面加热可视化窄矩形通道内的过冷沸腾摩擦阻力特性实验研究。实验中测量了实验段内的压降数据,并通过高速摄影仪拍摄了窄矩形通道内的气液两相图像,提出了过冷沸腾条件下的两相摩擦压降的剥离计算方法。基于本实验中获得摩擦压降数据,对分别基于均相流模型和分液相模型的经典两相摩擦压降计算关系式进行了评估,实验结果表明:采用不同等效黏度计算方法的均相流模型计算结果比实验值明显偏小;而分相流模型中,Sun and Mishiba关系式和Tran关系式均能够较好地预测摩擦阻力,计算值与实验值的平均相对偏差在±15%以内。结合实验数据,以分相流模型方法为基础,考虑全液相Reynolds数、Martinelli参数和Laplace数的影响,获得了计算分液相折算系数的经验关系式,与实验数据符合较好,平均相对误差在10%范围内。     

立体并流板的流体力学和传质性能

新型立体连续传质液体并流塔板是将LLC-Tray与两种并流流型相结合开发而成的新型塔板。通过实验测定了新型塔板的干、湿板压降,雾沫夹带,漏液等流体力学性能和传质性能,并进行关联得到了相应公式。结果表明,新型塔板板压降较低,雾沫夹带较低,液体处理量相对LLCT提高30%。     

用光镜和电镜对气孔的分析研究

本文根据用光学显微镜和电子扫描显微镜对球铁件中的气孔缺陷进行的观察和研究,阐述了气孔的形貌特征,并附了典型的光镜和扫描电镜照片.文章认为:借助先进的仪器设备,对于判断气孔缺陷的性质和产生的原因,研究探讨其形成机理,提出防止缺陷产生的措施具有重要的意义.     

C_2液相加氢用固定床鼓泡反应器的适宜操作区

本文以氢气为气相介质、甲苯为液相介质。研究了:气液通过φ39固定床鼓泡反应器时。反应器内流体的流动状态,确定了适宜的操作区,以便应用于碳二液相催化选择性加氢脱炔工艺研究。     

Double-sensor conductivity probe applied in a flotation system

This study proposed a new approach for measuring bubble size distribution, bubble mean diameter, Sauter mean bubble diameter, and gas holdup using a double-sensor conductivity probe in an air/water two-phase system bubble column. The results for the two-phase system were compared and calibrated using analyses from bubble images taken by a digital camera from the side of the column wall. Good agreement was observed between the two techniques. The same double-sensor conductivity was used in an air/water/solids three-phase system. The conductivity probe captured the change in bubble dynamic behaviour inside the pulp phase; however, the presence of the solids made it more challenging to measure. As a result, the VisioFroth commercial package, using images taken from the top of the froth layer, could be used in conjunction with the double-sensor conductivity probe to show the dynamic evolution of mineralized bubbles from the pulp zone to the froth zone in a flotation process.     

A simple correlation for gas bubbles rising in power‐law fluids

Recently, the author (Rodrigue, 2001 a, b) proposed a generalized correlation for the steady rise of gas bubbles in uncontaminated viscous Newtonian fluids of infinite extent. It is the purpose of this note to show that this model can be modified for inelastic non‐Newtonian power‐law fluids. Using data taken from six different studies, it is shown that the modified model can predict quite nicely the bubble velocity for these non‐Newtonian inelastic fluids.     

Prediction of dispersed phase holdup in a modified multi‐stage bubble column scrubber

This paper reports on the experimental investigation carried out to evaluate fractional dispersed phase holdup for a gas‐liquid mixture in a modified multi‐stage bubble column (with contraction and expansion disks), which has been conceived, designed and fabricated as a wet scrubber for control of air pollution; in addition it has versatile use as a gas‐liquid contactor in chemical process industries. A correlation developed for predicting fractional dispersed phase holdup has been found to be encouraging and highly significant from statistical analysis.     

Extraction of halide quaternary salts in an organic solvent/water system: Hydrodynamics and mass transfer

The hydrodynamic characteristics and mass transfers of halide quaternary salts between two immiscible phases in a stirred membrane permeation cell were investigated. The concentration of quaternary salt, temperature, solvent and the four kinds of halide quaternary salts were evaluated to achieve the extractive optimum condition. The diffusivity, overall mass‐transfer coefficients and individual mass‐transfer coefficients were determined and correlated in terms of the conventional Sh‐Re‐Sc relationship. The transfer time of quaternary salts across the membrane and the thickness of the hydrodynamic diffusion boundary layer were determined as well, so as to characterize the extractive phenomenon of quaternary salts between the two phases that is useful in phase‐transfer catalysis.     

Study on Jet Coflow Packing Tray

Experimental study on hydrodynamics and mass transfer efficiency of jet coflow packing tray (JCPT) was conducted in a φ285 mm column and a φ200 mm column, respectively. Compared with new vertical sieve tray which has been applied in the petrochemical industry since 1968, the JCPT has lower pressure drop, higher capacity and higher mass transfer efficiency, and seems promising in commercial application.