Modeling of mass transfer characteristics of bubble column reactor with surfactant present

Danckwert’s method was used to determine the specific interfacial area, a, and the individual mass transfer coefficient, kL, during absorption of CO2 in a bubble column with an anionic surfactant in the carbonate-bicarbonate buffer solution and NaAsO2 as catalyst, the presence of which decreases the specific interfacial area and the individual mass transfer coefficient. The specific interfacial area and the individual mass transfer coefficient increase with increasing su- perficial gas velocity. The specific interfacial area decreases whereas the individual mass transfer coefficient increases with increasing temperature. The results of experiments were used to determine the dependence of a, kL, and kLa on the surface tension, the temperature of the absorption phase, and the superficial velocity of the gas. The calculated results from the correlation were found to be within 10% deviation from the actual experimental results.

Modeling and optimization of industrial Fischer–Tropsch synthesis with the slurry bubble column reactor and iron-based catalyst

To optimize industrial Fischer-Tropsch （IT） synthesis with the slurry bubble column reactor （SBCR） and iron- based catalyst, a comprehensive process model for IT synthesis that includes a detailed SBCR model, gas liquid separation model, simplified CO2 removal model and tail gas cycle model was developed. An effective iteration algorithm was proposed to solve this process model, and the model was validated by industrial demonstration experiments data （SBCR with 5.8 m diameter and 30 m height）, with a maximum relative error 〈 10% for predicting the SBCR performances. Subsequently, the proposed model was adopted to optimize the industrial SBCR performances simultaneously considering process and reactor parameters variations. The results show that C5＋yield increases as catalyst loading increases within 10-70 ton and syngas H2/CO value decreases within 1.3-1.6, but it doesn＇t increase obviously when the catalyst loading exceeds 45 ton （about 15 wt% concentration）. Higher catalyst loading will result in higher difficulty for wax/catalyst separation and higher catalyst cost. There- fore, the catalyst loading （45 ton） is recommended for the industrial demonstration SBCR operation at syngas H2/ CO = 1.3, and the C5 ＋ yield is about 402 ton＂ per day, which has an about 16% increase than the industrial dem- onstration run result.

An Axial Dispersion Model for Evaporating Bubble Column Reactor

Evaporating bubble column reactor (EBCR) is a kind of aerated reactor in which the reaction heat is removed by the evaporation of volatile reaction mixture. In this paper, a mathematical model that accounts for the gas-liquid exothermic reaction and axial dispersions of both gas and liquid phase is employed to study the performance of EBCR for the process of p-xylene(PX) oxidation. The computational results show that there are remarkable concentration and temperature gradients in EBCR for high ratio of height to diameter (H/DT). The temperature is lower at the bottom of column and higher at the top, due to rapid evaporation induced by the feed gas near the bottom. The concentration profiles in the gas phase are more nonuniform than those (except PX) in the liquid phase, which causes more solvent burning consumption at high H/DT ratio. For p-xylene oxidation, theo ptimal H/DT is around 5.

An optimization method for enhancement of gas–liquid mass transfer in a bubble column reactor based on the entropy generation extremum principle

In this study,an optimization method is proposed to enhance the gas–liquid mass transfer in bubble column reactor based on the entropy generation extremum principle.The mass transfer–induced entropy generation can be maximized with the increase of mass transfer rate,based on which the velocity field can be optimized.The oxygen gas–liquid mass transfer is the major rate–limiting step of the toluene emissions biodegradation process in bubble column reactor,so the entropy generation due to oxygen mass transfer is used as the objective function,and the conservation equations of the gas–liquid flow and species concentration are taken as constraints.This optimization problem is solved by the calculus of variations,the optimal liquid flow pattern is obtained and the relationship of the maximum mass transfer enhancement on viscous dissipation is revealed,which can be used to improve the design of internal structure of the bubble column reactor.

Different efficiency toward the biomimetic aerobic oxidation of benzyl alcohol in microchannel and bubble column reactors: Hydrodynamic characteristics and gas–liquid mass transfer

The selective aerobic oxidation of benzyl alcohol to benzaldehyde has attracted considerable attention because benzaldehyde is a high value-added product. The rate of this typical gas–liquid reaction is significantly affected by mass transfer. In this study, CoTPP-mediated(CoTPP: cobalt(II) mesotetraphenylporphyrin) selective benzyl alcohol oxidation with oxygen was conducted in a membrane microchannel(MMC) reactor and a bubble column(BC) reactor, respectively. We observed that 83% benzyl alcohol was converted within 6.5 min in the MMC reactor, but only less than 10% benzyl alcohol was converted in the BC reactor. Hydrodynamic characteristics and gas–liquid mass transfer performances were compared for the MMC and BC reactors. The MMC reactor was assumed to be a plug flow reactor,and the dimensionless variance was 0.29. Compared to the BC reactor, the gas–liquid mass transfer was intensified significantly in MMC reactor. It could be ascribed to the high gas holdup(2.9 times higher than that of BC reactor), liquid film mass transfer coefficient(8.2 times higher than that of BC reactor), and mass transfer coefficient per unit interfacial area(3.8 times higher than that of BC reactor). Moreover,the Hatta number for the MMC reactor reached up to 0.61, which was about 15 times higher than that of the BC reactor. The computational fluid dynamics calculations for mass fractions in both liquid and gas phases were consistent with the experimental data.

Modeling of a slurry bubble column reactor for Fischer-Tropsch syn- thesis

On the basis of the global CO consumption rate model, the lumped product distribution model and the sedimenta- tion-dispersion model of a catalyst, a steady-state, one-dimensional mathematical model of the slurry bubble column reactor for Fischer-Tropsch synthesis were established. The mathematical simulation of the slurry bubble column reactor for Fischer-Tropsch synthesis was carried out under the following typical industrial operating conditions： temperature 230 ℃, pressure 3.0 MPa, gas flow 5x 105 m3/h, catalyst content in slurry phase 30%, reactor diameter 5.0 m and the composition of feed gas： y（H2）=0.60, y（CO）=0.30, y（N2）=0.10. The influences of operating pressure, temperature and re（HE）Ira（CO） in feed gas on the reactor＇s reaction performance were simulated.

Numerical Simulation of Unsteady-State Flowsin Bubble Column Reactors

Unsteady-state operation has been widely applied in chemical engineering, such as optimizing a process, increasing yield and saving energy, etc. But the knowledge of the flow characteristics in bubble column reactors(BCRs) under unsteady state control is far from enough. In order to study the flow structures in this operation, the volume of fluid (VOF) model and the standard k-ε model to simulate the evolution of gas-liquid flow in BCRs under the start-up state are combined. For both the symmetry and asymmetry flow, the layout of the gas-inlets, the gas-in velocity, the liquid viscosity and the aspect ratio of the BCR all have effects on the liquid velocity distribution. The simulation results could provide some information for the design and scale-up of the BCRs.

Mass Transfer Characteristics of H_2 and CO in Mimicked F-T Slurry Bubble Column Reactor

The equilibrium solubilities,volumetric gas-liquid mass transfer coefficients kLa of H_2 and CO were measured as functions of temperature(298―513 K),pressure(1―3 MPa),superficial gas velocity(0.5―3 cm/s) and solid volume fraction(5%―25%) in liquid paraffin/iron-based catalyst slurry bubble column reactor.The volumetric mass transfer coefficients kLa were obtained by measuring the dissolution rate of H_2 and CO.The influences of the operation conditions,such as pressure,temperature,superficial gas velocity and catalyst concentration on kLa,were investigated.Two empirical correlations were proposed to predict kLa values of H_2 and CO in liquid paraffin/solid particles slurry bubble column reactor.The results showed that the equilibrium solubilities of H-2 and CO increased with an increasing temperature and pressure,and the solubility of CO was greater than that for H_2.It was found that the equilibrium solubility can be expressed by Henry's law.The volumetric mass transfer coefficients of H_2 and CO were of the same order of magnitude,and increased with the increase of pressure,temperature and superficial gas velocity.The presence of solid particles decreased kLa values of both H_2 and CO.

Compressibility induced bubble size variation in bubble column reactors:Simulations by the CFD–PBE

Bubble column reactors can be simulated by the two fluid model(TFM) coupled with the population balance equation(PBE). For the large industrial bubble columns, the compressibility due to the pressure difference may introduce notable bubble size variation. In order to address the compressibility effect, the PBE should be reformulated and coupled with the compressible TFM. In this work, the PBE with a compressibility term was formulated from single bubble dynamics, the mean Sauter diameters predicted by the compressible TFM coupled with the PBE were compared with the analytical solutions obtained by the ideal gas law. It was proven that the mesoscale formulations presented in this work were physically consistent with the macroscale modeling. It can be used to simulate large industrial plants when the compressibility induced bubble size variation is important.

Bubble Column Reactor Fluid-dynamic Evaluation at Pilot-plant for Residue and Extra-heavy Crude Oil Upgrading Technology

Bubble column reactors are multiphase contacting devices used in a wide variety of industrial application. Inrtevep S. A. is working on developing technologies to convert heavy and extra-heavy crude oil using this type of reactors. Volumetric gas hold up, flow pattern, average gas bubble size, average interfacial area, RTD （residence time distribution）, dispersion coefficient, Peclet number are important design parameters for a proper scale up of them. Several cold model experiments have been proposed to determine the previously mentioned parameters at atmospheric conditions, using a plexiglas bubble column reactor at pilot plant scale unit （12 cm diameter）. It was also evaluated our own design of internal trays （plates） in the reactor. Air-tap water and air-light oil systems have been used. A wide operating condition range was applied, superficial gas velocity between 0.5-10 cm/s, liquid flowrate between 15-65 I/h. Generally speaking, working without internal trays was found that gas hold up increase along the reactor and it was possible to identify heterogeneous bubble, transition and turbulent flow pattern areas for the air-light oil system. Average gas bubble size increase along the reactor at bubble regime from 2-5 mm but at turbulent regime, stay oscillating between 1-3 mm. Average interfacial area increases exponentially with superficial gas velocity at any reactor height, till 1,412 m2/m3 for the air-light oil system but, at bubble flow regime, the average interfacial area is lower than 100 m2/m3, which negatively impact the reactor performance. Internal trays in the reactor always increase gas hold up at any condition or system used. Residence time distributions curves, Peclet numbers and dispersion coefficients founded, show that this reactor with this kind of design internal trays still tends to be a complete mixing reactor under the operating conditions used.

Bioleaching of low grade nickel sulfide mineral in column reactor

Jinchuan 低等级镍(0.4%0.6% Ni，集体部分) 硫化物矿物质矿石包含氧化镁的一个显著地高的内容(30%35% MgO，集体部分) 在主要脉石矿物质在场。Bioleaching 被执行调查可行性由于它花去要求的相对简洁， eco 友好的操作和低资本处理矿物质。混合 mesophiles 从在中国从几个酸矿收集的酸矿排水样品被充实。认为氧化镁被酸答案和过多的 Mg2+ 容易提取将超过混合 mesophiles 的忍耐，三个有效工具被用来在 bioleaching 操作期间减少氧化镁的劣势。他们是混合 mesophiles 的改编改进忍耐；预先沥滤移开很可滤取的氧化镁并且周期怀孕沥滤答案的部分流血基于混合 mesophiles 的忍耐控制 Mg2+ 的水平。镍(90.3%) 和钴(88.6%) 的抽取成功地在沥滤的 300 d 以内被完成从用在周围的温度的一个列反应堆的 Jinchuan 低等级镍硫化物矿物质矿石的过程。

Modeling bubble column reactor with the volume of fluid approach:Comparison of surface tension models

This work aims at comparing surface tension models in VOF(Volume of Fluid) modeling and investigating the effects of gas distributor and gas velocity. Hydrodynamics of a continuous chain of bubbles inside a bubble column reactor was simulated. The grid independence study was first conducted and a grid size of 1.0 mm was adopted in order to minimize the computing time without compromising the accuracy of the results. The predictions were validated by comparing the experimental studies reported in the literature. It was found that all surface tension models can describe the bubble rise and bubble plume in a column with slight deviations.

Production of iturin A through glass column reactor (GCR) from soybean curd residue (okara) by <i>Bacillus subtilis</i>RB14-CS under solid state fermentation (SSF)

The present study was conducted with an aim to scale up the production of iturin A using soybean curd residue (okara). Iturin A was produced by indigenous bacterial strain Bacillus subtilis RB14-CS through glass column reactor (GCR) under solid state fermentation (SSF) was characterized. The enhanced iturin A production was observed with respect to enhanced substrate bed height when SSF was conducted in Erlenmeyer flask. To check the effect of substrate bed height on iturin A production under SSF of okara, GCR was introduced. Substrate bed height of 15 cm was suitable for iturin A production which was about 2700 mg/kg wet substrate. The observed iturin A production by the aerobic bacteria Bacillus subtilis in nearly anaerobic condition in such high substrate bed for SSF is a wonderful finding for development of SSF system in future.

The Operating Performance of Stirred Column Reactor

A theoretical analysis of the effects of flow and mixing on the operating features of astirred column reactor(SCR)with multistage mixers and cooling partition plates was conducted.Amethod for calculating the concentration reduction for a second order chemical reaction in a SCRwas proposed.The reactants concerned were pre-mixed before feeding into the SCR.The SCR wascomposed of a number of stages with interstage backmixing.Experimental investigation with variousreaction media were carried out in order to study the effect of mixing on the operational performanceof the SCR.The experimental data were compared with the theoretical results.

Hydrolysis of Olive Oil with Immobilized Lipase in a Tapered Column Reactor

Lipase was immobilized in ion exchange resin and then used in the hydrolysis of olive oil to produce fatty acids and glycerol. The time course of hydrolysis of olive oil was investigated in a stirred tank reactor using both of the free and immobilized lipases to find the yield of activity of immobilized enzyme. Continuous hydrolysis of olive oil was also carried out in a tapered column reactor and a cylindrical column reactor with a bottom ID of 10 mm at different upward flow rates. It can be known from experimental results that the degree of hydrolysis of olive oil in the tapered column reactor is moderately better than that in the cylindrical column reactor, the pressure drop in the tapered column reactor is much smaller than that in the cylindrical column reactor.

Particle effects on the hydrodynamics in slurry bubble column reactors:A review from multiscale mechanisms Author links open overlay panel

Particles can appear as catalyst,reactant or product in various gas-liquid-solid three-phase production processes.Slurry bubble column reactors(SBCRs),as a kind of three-phase reactors,are preferred for phase contacting and mixing.However,literature studies concerning the effects of particles on the hydrodynamics of SBCRs are manifold and inconsistent in conclusions.Essentially,the multiscale interactions between particles,turbulent eddies and bubbles determine the reactor performance.This review focuses on revealing the particle effects in SBCRs from the perspective of multiscale mechanisms.Macroscopic hydrodynamic changes due to particle effects in literature are summarized.Dimensionless parameters,including the Stokes number,the solid-to-liquid density ratio,the ratio of particle and liquid characteristic lengths,the contact angle and the particle volume fraction are adopted to evaluate the characteristics of gas-liquid-solid flows.The relationships between particle influencing mechanisms and these parameters are analyzed and determined.Inconsistent experimental results are explained by different ranges of these dimensionless parameters.Moreover,particle effects at the mesoscale and microscale,such as the influence on the bubble dynamics and the pivoting effect on the turbulence energy spectrum,are elaborated.Finally,progress in modeling the SBCRs with consideration of particles effects using the Euler method are introduced.This review aims to improve the overall understanding of the complex hydrodynamics in the SBCRs.

Removal of SO2 using ammonium bicarbonate aqueous solution as absorbent in a bubble column reactor

In this work, the removal of SO2 from gas mixture with air and SO2 by ammonium bicarbonate aqueous solution as absorbent was investigated experi- mentally in a bubble column reactor. The effects of the concentration of ammonium bicarbonate, the SO2 inlet concentration of gas phase and the gas flow rate on the removal rate of SO2 were studied. The results showed that the higher the SO2 inlet concentration and the gas flow rate, the shorter the lasting time of SO2 completely removed in gas outlet, and then the faster the decrease in the removal rate of SO2. The lasting time of SO2 completely removed in gas outlet increased with increasing ammonium bicarbonate concentration. During the process of SO2 absorption, there was a critical pH of solution. When the solution pH was less than the critical pH, it would sharply fall, resulting in a rapid decrease of the SO2 removal rate. A theoretical model for predicting the SO2 removal rate has been developed by taking the chemical enhancement and the sulfite concentration in the liquid phase into account simultaneously.

The Design and Control of Distillation Column with Side Reactors for Chlorobenzene Production

The distillation column with side reactors (SRC) can overcome the temperature/pressure mismatch in the traditional reactive distillation, the column operates at temperature/pressure favorable for vapor-liquid separation, while the reactors operate at temperatures/pressures favorable for reaction kinetics. According to the smooth operation and automatic control problem of the distillation column with side reactors (SRC), the design, simulation calculation and dynamic control of the SCR process for chlorobenzene production are discussed in the paper. Firstly, the mechanism models, the integrated structure optimal design and process simulation systems are established, respectively. And then multivariable control schemes are designed, the controllability of SRC process based on the optimal steady-state integrated structure is explored. The dynamic response performances of closed-loop system against several disturbances are discussed to verify the effectiveness of control schemes for the SRC process. The simulating results show that the control structure using conventional control strategies can effectively overcome feeding disturbances in a specific range.

Multi-scale and multi-fractal analysis of pressure fluctuation in slurry bubble column bed reactor

The Daubechies second order wavelet was applied to decompose pressure fluctuation signals with the gas flux varying from 0.18 to 0.90 m3/h and the solid mass fraction from 0 to 20% and scales 1?9 detail signals and the 9th scale approximation signals. The pressure signals were studied by multi-scale and R/S analysis method. Hurst analysis method was applied to analyze multi-fractal characteristics of different scale signals. The results show that the characteristics of mono-fractal under scale 1 and scale 2, and bi-fractal under scale 3?9 are effective in deducing the hydrodynamics in slurry bubbling flow system. The measured pressure signals are decomposed to micro-scale signals, meso-scale signals and macro-scale signals. Micro-scale and macro-scale signals are of mono-fractal characteristics, and meso-scale signals are of bi-fractal characteristics. By analyzing energy distribution of different scale signals,it is shown that pressure fluctuations mainly reflects meso-scale interaction between the particles and the bubble.

MPC of distillation column with side reactors for methyl acetate

This paper focuses on the dynamic control of distillation column with side reactors(SRC) for methyl acetate production. To obtain the optimum integrated structure and steady state simulation, the systematic design approach based on the concept of independent reaction amount is applied to the process of SRC for methyl acetate production. In addition to the basic control loops, multi-variable model predictive control modular with methyl acetate concentration and temperature of sensitive plate is designed. Then, based on process simulation software Aspen Plus, dynamic simulation of SRC for methyl acetate production is used to verify the effectiveness of the control scheme.