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.

Mathematical Simulation and Design of Three-Phase Bubble Column Reactor for Direct Synthesis of Dimethyl Ether from Syngas

A three-phase reactor mathematical model was set up to simulate and design a three-phase bubble column reactor for direct synthesis of dimethyl ether （DME） from syngas, considering both the influence of part inert carrier backmixing on transfer and the influence of catalyst grain sedimentation on reaction. On the basis of this model, the influences of the size and reaction conditions of a 100000 t/a DME reactor on capacity were investigated. The optimized size of the 10000 t/a DME synthesis reactor was proposed as follows： diameter 3.2 m, height 20 m, built-in 400 tube heat exchanger （Ф 38×2 mm）, and inert heat carrier paraffin oil 68 t and catalyst 34.46 t. Reaction temperature and pressure were important factors influencing the reaction conversion for different size reactors. Under the condition of uniform catalyst concentration distribution, higher pressure and temperature were proposed to achieve a higher production capacity of DME. The best ratio of fresh syngas for DME synthesis was 2.04.

Kaoline-based catalyst for a high stability desulfurization of sour heavy naphtha in a three-phase oscillatory baffled reactor

To meet the rapidly increasing demand for energy and the dramatic depletion of conventional crude oil,it is imperative to utilize sour naphtha.With no coke being produced,oxidative desulfurization(ODS)of naphtha lowers its sulfur content and average molecular weight.In this article,we outline a method for heavy naphtha non-extractive ODS using a very stable catalyst.The technique involves the use of a solid catalyst with oxygen gas as the oxidant.This necessitated relatively high mixing intensities;hence a three-phase Oscillatory Baffled Reactor(OBR)was used.The catalyst was based on the zeolite ZSM-5,prepared from natural kaolin by a series of delamination and activation steps and impregnated with Fe.A TiO2 nanolayer was applied,using the sol-gel method,to prevent rapid deactivation.The reactor performance was evaluated to minimize the sulfur content in the naphtha fuel.Due to the protective coating,the sulfur conversion stabilized at 90%.The results of this work establish the use of natural clay-based catalysts in a continuous,three-phase ODS,particularly with regard to proving long-term stability.It also showed that modest ODS can be achieved using an environmentally friendly oxidant,at mild operating conditions,whilst maintaining stability.

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.

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 Continuous Cross-flow Microfiltration Process in an Airlift External-loop Slurry Reactor

New modified combination mathematical models including the pores blocking models and the cake layer models were developed to describe the continuous cross-flow microfiltration in an airlift external loop slurry reactor. The pores blocking models were created based on the standard blocking law and the intermediate blocking law, and then the cake layer models were developed based on the hydrodynamic theory in which the calculation method of porosity of cake layer was newly corrected. The Air-Water-FCC equilibrium catalysts cold model experiment was used to verify the relevant models.Results showed that the calculated values fitted well with experimental data with a relative error of less than 10%.

Upgrading Siberian(Russia)crude oil by hydrodesulfurization in a slurry reactor:A kinetic study

Hydrodesulfurization(HDS)of sour crude oil is an effective way to address the corrosion problems in refineries,and is an economic way to process sour crude oil in an existing refinery built for sweet oil.In the current study,the HDS of Siberian crude oil was carried out in a slurry reactor.The Co-Mo,Ni-Mo,and Ni-W catalysts supported onγ-Al2O3 were compared at the temperature of 340℃ and the pressure of 4.5 MPa.The HDS activity follows the order of Co-Mo N Ni-Mo N Ni-Wat a high concentration of H2S,and the difference between Co-Mo and Ni-Mo becomes insignificant at a low concentration of H2S.The influence of reaction temperature 320-360℃ and reaction pressure 3-5.5 MPa was investigated,and both play a positive role in the HDS reaction.A kinetic model over Ni-Mo/Al2O3 in the slurry reactor was established.The activation energy is estimated as 60.34 kJ·mol−1;the orders of sulfur components and hydrogen partial pressure are 1.43 and 1.30,respectively.The kinetic parameters are compared with those in a trickle-bed reactor,implying that the mass transfer is greatly enhanced in the slurry reactor.The back mixing effect is present in the slurry reactor and can be reduced by a multi-stage design,which would lead to higher reactor efficiency in industrial application.

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.

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.

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%）.

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.

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.

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.

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.

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.

气升式浆态床外环流反应器流体力学性能研究

针对气含率和浆液循环流速两个关键流体力学参数,系统研究了气升式浆态床外环流反应器的流体力学特性,掌握了气含率与浆液循环流速的变化规律。验证了体积膨胀法、压差法和电导探针法测量气含率的方法准确性。研究了气体分布器结构对气升式浆态床外环流反应器流体力学特性的影响,结果表明开孔向下双环管分布器的综合性能最优。气含率与浆液循环液速之间存在线性关系,建立了预测浆液循环流速的计算式,计算误差基本小于20%。

催化剂加氢能力对减压渣油中沥青质组成与结构的影响

考察了氧化硅担载铁硫催化剂在浆态床反应器中对Merey减压渣油的转化性能。采用元素分析、GPC、XPS、1H-NMR、FT-IR和XRD等手段研究加氢催化剂对Merey减压渣油中沥青质组成与结构转变的影响,并分析加氢催化剂抑制沥青质生焦转化影响机制。结果表明,随着催化剂加氢能力增强,沥青质组成中w(N)和w(S)不断降低,最容易发生加氢脱硫反应,n(H)/n(C)、平均链长(n)与缩合度参数(HAU/CA)升高,芳香度(fA)、堆叠芳香片层的平均高度(Lc)、芳香片层直径(La)与堆叠芳香片层的平均数量(M)下降。这主要是由于加氢能力强的催化剂可以提供较多氢自由基,使沥青质结构中稠合芳环加氢,以产生较长侧链,长侧链阻碍沥青质形成较大尺寸的纳米聚集体,进而抑制沥青质从油相中析出转化为焦炭。

器内过滤对浆态床反应器操作特性的影响

浆态床反应器是低温费-托合成工艺普遍采用的反应器形式,常采用器内过滤系统连续分离反应生成的液体产品。通过实验方法从不同条件下过滤区域的漏气率与平均气含率的变化及气体反冲洗对床层操作稳定性的影响2个方面,研究了器内过滤对浆态床反应器操作特性的影响。结果表明:因为气体从过滤器处的泄漏,过滤区域平均气含率出现明显降低;过滤压差从8 kPa增至16 kPa,漏气率与气含率均随之增加,但平均气含率的平均增长值从0.0059降至0.0044;气-液体系的漏气率最大,平均气含率相对较低,范围为0.063~0.145;增加浆液颗粒质量分数到5%时,由于漏气率下降,平均气含率范围扩大至0.062~0.146。滤芯孔隙从80μm减小至30μm,气-液体系下漏气率降低幅度增大,平均气含率的平均增长值从0.0040增至0.0049;当加入质量分数为5%的颗粒后漏气率降低幅度开始下降,平均气含率的平均增长值也从0.0018降至0.0012。从过滤区域床层压差波动看,气体反冲洗对浆态床操作稳定性存在明显扰动,且滤芯孔隙越大,这种扰动效应越强烈。