Process Intensification in Pneumatically Agitated Slurry Reactors

Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,especially in the biological fermentation and energy chemical industry,due to their low shear stress,good mixing,perfect mass-/heat-transfer properties,and relatively low costs.To further improve the performance of slurry reactors(i.e.,mixing and mass/heat transfer)and to satisfy industrial require-ments(e.g.,temperature control,reduction of back-mixing,and product separation),the process intensi-fication of slurry reactors is essential.This article starts by reviewing the latest advancements in the intensification of mixing and mass/heat transfer in these two types of reactors.It then summarizes process-intensification methods for mixing and separation that allow continuous production in these slurry reactors.Process-intensification technology that integrates directional flow in an ALR with simple solid-liquid separation in a hydrocyclone is recommended for its high efficiency and low costs.This arti-cle also systematically addresses vital considerations and challenges,including flow regime discrimina-tion,gas spargers,solid particle effects,and other concerns in slurry reactors.It introduces the progress of numerical simulation using computational fluid dynamics(CFD)for the rational design of slurry reactors and discusses difficulties in modeling.Finally,it presents conclusions and perspectives on the design of industrial slurry reactors.

Two-Bubble Class Model for Churn-Turbulent Regime in a Bubble Column Slurry Reactor of Fischer-Tropsch Synthesis

A model for a bubble column slurry reactor is developed based on the experiment of Rhenpreussen Koppers demonstration plant for slurry phase Fischer-Tropsch synthesis reported by Koelble et al. This model is applicable to the operation in the churn-turbulent regime and incorporates the information on the bubble size. The axial dispersion model is adopted to describe the flow characteristics of the Fischer-Tropsch slurry reactor. With the model developed, simulations are performed to identify the steady state behavior of a Fischer-Tropsch slurry reactor of commercial size. Predictions of the two-bubble class model is compared with that of the conventional single- bubble class model. The results show that under a variety of conditions, the two-bubble class model gives results different from those for the single-bubble class model.

Modeling of Fischer-Tropsch Synthesis in a Slurry Reactor with Water Permeable Membrane

Fischer-Tropsch synthesis is an important chemical process for the production of liquid fuels and olefins. In recent years, the abundant availability of natural gas and the increasing demand of olefins, diesel, and waxes have led to a high interest to further develop this process. A mathematical model of a slurry membrane reactor used for syngas polymerization was developed to simulate and compare the maximum yields and operating conditions in the reactor with that in a conventional slurry reactor. The carbon polymerization was studied from a modeling point of view in a slurry reactor with a water permeable membrane and a conventional slurry reactor. Simulation results show that different parameters affect syngas conversion and carbon product distribution, such as the hydrogen to carbon monoxide ratio, and the membrane parameters such as membrane permeance.

Overview of Fischer-Tropsch Synthesis in Slurry Reactors

A brief review of Fischer-Tropsch synthesis specially in slurry reactors is presented, covering reaction kinetics, activity and selectivity of catalysts, product distribution, effects of process parameters, mass transfer and solubility of gas. Some important aspects of further research are proposed for improving both theories and production.

Modeling of Bubble Column Slurry Reactor for Dimethyl Ether Synthesis from Syngas

A mathematical model for a bubble column slurry reactor is presented for dimethyl ether synthesis from syngas. Methanol synthesis from carbon monoxide and carbon dioxide by hydrogenation and the methanol dehydration are considered as independent reactions, in which methanol, dimethyl ether and carbon dioxide are the key components. In this model, the gas phase is considered to be in plug flow and the liquid phase to be in partly back mixing with axial distribution of solid catalyst. The simulation results show that the axial dispersion of solid catalysts, the operational height of the slurry phase in the bubble column slurry reactor, and the reaction results are influenced by the reaction temperature and pressure, which are the basic data for the scale-up of reactor.

Flow Characteristics in an External-Loop Airlift Slurry Reactor

The local flow characteristics in an external-loop airlift slurry reactor were investigated.The axial profiles of the local gas holdup,the Sauter mean diameter and the rise velocity were obtained.It was found that the bubble size and rise velocity were influenced by the solid holdup,and the bubble coalescence was enhanced by the increase of the solid holdup.A new correlation was used to predict the slip velocity between the gas phase and the slurry phase by taking into account the local gas holdup,the bubble size,and the physical properties of the experimental system.By using this correlation,the local drag coefficient can be calculated in the bubble swarm.

Review on the effect of heat exchanger tubes on flow behavior and heat/mass transfer of the bubble/slurry reactors

Bubble/Slurry bubble column reactors(BCR/SBCR)are intensively used as multiphase reactors for a wide range of application in the chemical,biochemical and petrochemical industries.Most of these applications involve complicate gas–liquid/gas–liquid–solid flow behavior and exothermic process,thus it is necessary to equip the BCR/SBCR with heat exchanger tubes to remove the heat and govern the performance of the reactor.Amounts of experimental and numerical studies have been carried out to describe the phenomena taking place in BCR/SBCRs with heat exchanger tubes.Unfortunately,little effort has been put on reviewing the experiments and simulations for examining the effect of internals on the performance and hydrodynamics of BCR/SBCR.The objective of this work is to give a state-of-the-art review of the literature on the effects of heat exchanger tubes with different types and configurations on flow behavior and heat/mass transfer,then provide adequate information and scientific basis for the design and the development of heat exchanger tubes in BCR/SBCR,ultimately provide reasonable suggestions for better comprehend the performance of different heat exchanger tubes on hydrodynamics.

Impacts of solid physical properties on the performances of a slurry external airlift loop reactor integrating mixing and separation

Solid physical properties are vital for the design, optimization, and scale-up of gas–liquid–solid multiphase reactors. The complex and interactional effects of the solid physical properties, including particle diameter, density, wettability, and sphericity, on the hydrodynamic behaviors in a new external airlift loop reactor(EALR) integrating mixing and separation are decoupled in this work. Two semi-empirical equations are proposed and validated to predict the overall gas holdup and liquid circulating velocity satisfactorily, and then the individual influence of such solid physical properties is further investigated. The results demonstrate that both the overall gas holdup in the riser and the liquid circulating velocity in the downcomer increase with the contact angle, but decrease with particle size, density, and sphericity.Additionally, the impact of the particle size on the liquid circulating velocity is also profoundly revealed on a micro-level considering the particle size distribution. Moreover, the axial solid concentration distribution is discussed, and the uniformity of the slurry is described by the mixing index of the solid particles. The results show that a more homogeneous mixture can be achieved by adding finer particles other than attaining violent turbulence. Therefore, this work lays a foundation for the design, scale-up, and industrialization of the EALRs.

Ruthenium promotion of Co/SBA-15 catalysts for Fischer-Tropsch synthesis in slurry-phase reactors

The aim of this work was to evaluate the catalytic properties of a Ru promoted Co/SBA-15 catalyst for Fischer-Tropsch synthesis （FTS）. The Ru promoted Co/SBA-15 catalyst was prepared by wet impregnation method and was characterized by X-ray diffraction, X-ray energy dispersion spectrophotometer, N2 adsorption-desorption, temperature-programmed reduction and transmission electron microscopy. The Fischer-Tropsch synthesis using the catalyst was carried out to evaluate the catalyst activity and its effect on FTS product distribution. The synthesis was carried out in a slurry reactor operating at 513 K, 20 atm, CO ： H2 molar ratio of 1 ： 1. X-ray diffraction showed that the calcined cobalt catalyst did not modify the structure of SBA-15, proving that Co was present in the form of Co3O4 in the catalyst. The addition of cobalt in SBA-15 decreased the specific superficial area of the molecular sieve. Fischer-Tropsch synthesis activity and C5＋ hydrocarbon selectivity increased with the addition of Ru. The increases in activity and selectivity were attributed to the increased number of active sites resulting from higher reducibility and the synergetic effect of Ru and Co. Ru/Co/SBA-15 catalysts showed moderate conversion （40%） and high selectivity towards the production of C5＋ （80 wt%）.

Study on direct alcohol/ether fuel synthesis process in bubble column slurry reactor

The recent studies of direct alcohol/ether synthesis process in slurry reactors were reviewed,and the research work in our laboratory was carried out in this paper.a global kinetics model for direct dimethyl ether(DME)synthesis from syngas over a novel Cu-Zn-Al-Zr slurry catalyst was established according to the total of 25 experimental data,and a steady-state one-dimensional mathematical model was further developed in bubble column slurry reactor(BCSR),which was assumed that the bubble phase was plug flow,and the liquid phase was fully mixed flow.The numerical simulations of reactor design of 100000 t/a dimethyl ether pilot plant indicate that higher pressure and lower temperature were favorable to the increase of CO conversion,selectivity of dimethyl ether,product yield and height of slurry bed.The optimal operating conditions for DME synthesis process were obtained:reaction temperature at 240℃,reactor pressure at 5 MPa and reactor diameter of 2.5 m.

Hydrodynamic Behavior of Three-Phase Airlift Loop Slurry Reactor

A novel fiber optic probe system and a set of commercial ultrasonic Doppler velocimeters have been used to study the hydrodynamic behavior of a three phase airlift loop (TPAL) slurry reactor. Experiments have been carried out in a loop reactor with 100 mm inner diameter and 2.5 m height, in which air, tap water and silica gel particles are used as the gas, liquid and solid phase, respectively. The radial profile of gas holdup, bubble size, bubble rising velocity, liquid circulating velocity, and the influence of the main operating conditions such as superficial gas velocity and solids concentration have been studied experimentally in the TPAL slurry reactor. The experimental results show that the bubble characteristics are different in various flow regimes and the radial profiles of some hydrodynamic parameters in the TPAL slurry reactor are more uniform than those in traditional three phase reactors. The distribution of the bubble size and bubble rising velocity can be described by a lognormal function. The influence of superficial gas velocity on the hydrodynamic parameters is more remarkable than that of the solids concentration.

Application of gamma-ray attenuation technology in density measurement of a slurry reactor

Axial density profile of the gas-liquid-solid mixture in a slurry bubble column was measured by gamma-ray attenuation technology.Several measures for improving measurement precision were presented based on the discussion on attenuation law.It was found that the response frequency and the ray intensity should be as high as possible to improve the measurement precision.The mass absorption coefficient depended on not the object’s thickness but the location where the object was placed between the ray source and the detector.The results showed that the density in the column decreases with the increase of column height,which indicates that the measurement by gamma-ray attenuation is reasonable.

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.

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.

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.

A Comprehensive Review of the Influence of Heat Exchange Tubes on Hydrodynamic,Heat,and Mass Transfer in Bubble and Slurry Bubble

Bubble and slurry bubble column reactors(BCRs/SBCRs)are used for various chemical,biochemical,and petro-chemical applications.They have several operational and maintenance advantages,including excellent heat and mass transfer rates,simplicity,and low operating and maintenance cost.Typically,a catalyst is present in addition to biochemical processes where microorganisms are used to produce industrially valuable bio-products.Since most applications involve complicated gas-liquid,gas-liquid-solid,and exothermic processes,the BCR/SBCR must be equipped with heat-exchanging tubes to dissipate heat and control the reactor’s overall performance.In this review,past and very recent experimental and numerical investigations on such systems are critically dis-cussed.Furthermore,gaps to befilled and critical aspects still requiring investigation are identified.

Activation pressure studies with an iron-based catalyst for slurry Fischer-Tropsch synthesis

Fischer-Tropsch synthesis （FTS） was carried out with an industrial iron-based catalyst （100Fe/5Cu/6K/16SiO2, by weight） under the baseline conditions in a stirred tank slurry reactor （STSR）. The effects of activation pressure on the catalyst activity and selectivity were investigated. It was found that iron phase compositions, textural properties, and FTS performances of the catalysts were strongly dependent on activation pressure. The high activation pressure retards the carburization. MФssbauer effect spectroscopy （MES） results indicated that the contents of the iron carbides clearly decrease with the increase of activation pressure, especially for the activation pressure increasing from 1.0 MPa to 1.5 MPa, and the reverse trend is observed for superparamagnetic Fe^3＋ （spm）. The higher content of Fe^3＋ （spm） results in the higher amount of CO2 in tail gas when the catalyst is reduced at higher pressure. The catalyst activity decreases with the increase of activation pressure. The high quantity of iron carbides is necessary to obtain high FTS activity. However, the activity of the catalyst activated in syngas can not be predicted solely from the fraction of the carbides. It is concluded that activation with syngas at the lower pressure would be the most desirable for the better activity and stability on the iron-based catalyst.

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.

Direct Dimethyl Ether Synthesis

Dimethyl ether (DME) is a clean and economical alternative fuel which can beproduced from natural gas through synthesis gas. The properties of DME are very similar to those ofLP gas. DME can be used for various fields as a fuel such as power generation, transportation, homeheating and cooking, etc. It contains no sulfur or nitrogen. It is not corrosive to any metal andnot harmful to human body. An innovative process of direct synthesis of DME from synthesis gas hasbeen developed. Newly developed catalyst in a slurry phase reactor gave a high conversion and highselectivity of DME production. One and half year pilot scale plant (5 tons per day) testing, whichwas supported by METI, had successfully finished with about 400 tons DME production.

Revalorization of CO2 for methanol production via ZnO promoted carbon nanofibers based Cu-ZrO2 catalytic hydrogenation

A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and characterized by ICP-OES,HRTEM,BET,N2O chemisorption,TPR,XPS and CO2-TPD techniques.The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst.Copper surface area(SCu)and dispersion(DCu)were slightly decreased by incorporation of ZnO promoter.Nevertheless,SCuand DCuwere remarkably decreased when ZnO content was exceeded beyond 3 wt%.The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180℃,respectively.The promotion of CuZrO2/CNFs catalyst with 3 wt%of ZnO enhanced methanol synthesis rate from 32 to 45 g kg^-1 h^-1.Notably,with the ZnO promotion the selectivity to methanol was enhanced to 92%compared to 78%of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion.In addition,the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.