A new and original microwave continuous reactor under high pressure for future chemistry

A new and original high pressure reactor has been designed and developed for continuous flow chemistry under microwaves at industrial scale. The reactor originality is that the microwave applicator is the reactor itself. It allows then the use of metallic and thick walls for the reactor adapted to a use at high pressures and high temperatures. Wave propagation coupled to heat transfer was simulated using COMSOL Multiphysics® and the design was optimized to minimize wave reflections and maximize energy transfers in the reacting medium. This leads to extremely good energy yields. Experiments confirm that the microwave energy is fully absorbed by the reacting medium. The reactor allows continuous chemical reactions at a kg/h scale, under microwave heating, up to 7 MPa and 200°C. The double dehydration of hexylene glycol has been performed under various operating conditions demonstrating then the operability of this new reactor. © 2016 American Institute of Chemical Engineers AIChE J, 63: 192–199, 2017     

Taylor-vortex membrane reactor for continuous gas-liquid reactions

A unique Taylor-vortex membrane reactor (TVMR) design for continuous gas-liquid reactions is presented in this work. The reactor consists of a cylindrical rotor inside a stationary concentric cylindrical vessel, and a flexible system of equispaced baffle rings surrounding the rotor. This restricts the annular cross section to a small gap between the baffles and the rotor, and divides the annulus into 18 mixing zones. The baffles support a 6 m long PFA tubular membrane that is woven around the rotor. At 4 mL/min inlet flow rate, the TVMR showed a plug-flow behavior and outperformed the unbaffled reactor, having 5–12 times lower axial dispersion. The continuous aerobic oxidation of benzyl alcohol was performed for 7 h using the Pd(OAc)₂/pyridine catalyst in toluene at 100 °C and 1.1 MPa oxygen pressure. A stable conversion of 30% was achieved with 85% benzaldehyde selectivity, and no pervaporation of organics into the gas phase.     

Electro-membrane reactor: A powerful tool for green chemical engineering

Electro-membrane reactors use electro-membranes for preferentially diffusive/electrophoretic migration or electroosmotic separation of in-situ reactive products, thereby maximizing the reaction rate and transport efficiencies of the products. These reactors are widely employed in the chemical engineering sectors such as green chemical synthesis, biorefining, electrocatalytic reduction/oxidation, and water treatment. In this review article, we provide an overview of the recent advances in three categories of electro-membrane reactors in chemical engineering sectors from three categories: (1) Electro-membrane reactors based on stacked ion-exchange membranes for resources recovery; (2) Electro-membrane reactors via Faraday reactions on functional anodes/cathodes for substance transformation; and (3) Closed-loop chemical reactions and substance separation via coupling of Faraday reactions and stacked membranes. The increasing demand for low-carbon economy has accelerated the advancement of environmentally friendly chemical engineering and sustainable processes and necessitates the use of electro-membrane processes. The macro perspective provides a timely reference for researchers and engineers.     

Novel operability‐based approach for process design and intensification: Application to a membrane reactor for direct methane aromatization

This article introduces a novel operability‐based approach for process design and intensification of energy systems described by nonlinear models. This approach is applied to a membrane reactor (MR) for the direct methane aromatization (DMA) conversion to benzene and hydrogen. The proposed method broadens the scope of the traditional path of the operability approaches for design and control, mainly oriented to obtain the achievable output set (AOS) from the available input set, and compare the computed AOS to a desired output set. In particular, an optimization algorithm based on nonlinear programming tools is formulated for the calculation of the desired input set that is feasible considering process constraints and intensification targets. Results on the application of the operability method as a tool for process intensification show reduction of the DMA‐MR footprint (≈77% reactor volume and 80% membrane area reduction) for an equivalent level of performance, when compared to the base case. This case study indicates that the novel approach can be a powerful tool for process intensification of membrane reactors and other complex chemical processes. © 2016 American Institute of Chemical Engineers AIChE J, 63: 975–983, 2017     

全混流反应器内流动规律模拟研究

研究了一种接近全混流的小型气固相反应器,可以用于在实验室研究时需要实现全混流接触状态的气固相反应的研究.采用计算流体力学软件(CFD)进行模拟得到最优结构,其结构包括1个圆锥形反应器主体,4个连接在反应器主体底部的进料口,1个连接在反应器主体上部的出料口.气体从4个进料口进入,催化剂在流动过程中从中部掉落,形成气体水平...     

Preliminary design and simulation of a microstructured reactor for production of synthesis gas by steam methane reforming

The present study considers the potentials of the well-known production of syngas by steam methane reforming (SMR), by operation within microstructured reactors. The model of a microchannel reactor is developed, including very fast kinetic reaction rates on the coated catalytic walls of the reactor module. By varying the characteristic dimensions of the channels, and considering technical constraints on the design and operating conditions, the results demonstrate that the SMR reactor can be drastically miniaturized while maintaining its productivity without any additional pressure drop. Furthermore, by reducing the channel characteristic dimensions, it is possible to suppress heat and mass-transfer limitations enabling SMR reactor operation at thermodynamic equilibrium. A fast method for preliminary design of microstructured heat-exchanger reactors is developed, that enables to identify the optimal channels number and heat power needed to reach process specifications.     

A continuous reactor system for production of lactulose

A continuous reactor process was developed to produce lactulose from lactose. A system of two CSTRs in series with a tubular finishing reactor gave conversion to lactulose of about 76%. The reactors ran at 71–75°C with a volumetric hold-up in the CSTRs of 22·7 dm³ and in the tubular reactor of 2·6 dm³. Each CSTR had a nominal residence time of 44 min. The flow rate was 0·53 dm³ min^?1.     

Numerical simulation of liquid-solid two-phase flow in a tubular loop polymerization reactor

Understanding hydrodynamics of tubular loop reactors is crucial in proper scale-up and design of these reactors. Computational fluid dynamics (CFD) models have shown promise in gaining this understanding. In this paper, a three-dimensional (3D) CFD model, using a Eulerian-Eulerian two-fluid model incorporating the kinetic theory of granular flow, was developed to describe the steady-state liquid-solid two-phase flow in a tubular loop propylene polymerization reactor composing of loop and axial flow pump. Corresponding simulations were carried out in the commercial CFD code Fluent. The entire flow field in the loop reactor was calculated by the model. The predicted pressure gradient data were found to agree well with the classical calculated data. Furthermore, the model was used to investigate the influences of the circulation flow velocity and the sold particle size on the solid hold-up. The simulation results showed that the solid hold-up has a relatively uniform distribution in the loop reactor at small particles in volume and high-circulation flow velocities.     

Cyclic mass transport phenomena in a novel reactor for gas–liquid–solid contacting

This study introduces a novel reactor concept, referred to as the Siphon Reactor, for intensified phase contacting of gas–liquid reactants on heterogeneous catalysts. The reactor comprises a fixed catalyst bed in a siphoned reservoir, which is periodically filled and emptied. This serves to alternate liquid–solid and then gas–liquid mass transfer processes. As the duration of each phase can be manipulated, mass transfer can be deliberately harmonized with the reaction. Residence time experiments demonstrate that, in contrast to periodically operated trickle‐bed reactors, the static liquid hold‐up is exchanged frequently and uniformly due to the complete homogeneous liquid wetting. A mathematical model describing the siphon hydrodynamics was developed and experimentally validated. The model was extended to account for a heterogeneously catalyzed gas–liquid reaction and capture the influence of siphon operation on conversion and selectivity of a consecutive reaction. © 2016 American Institute of Chemical Engineers AIChE J, 63: 208–215, 2017     

生物柴油连续化生产设备及工艺进展

“碳中和”目标提出后,各行各业都在寻求减少碳排放的方法,生物质能源的使用是实现碳中和目标的重要手段之一。生物柴油以其优良的燃烧性能及环保性能成为一种较为理想的生物质燃料,其生产工艺是近年研究热点。连续化生产工艺对生物柴油的规模化制备与推广有着重要意义。目前连续化制备生物柴油的反应装置主要有微反应器、固定床反应器、管式反应器、膜反应器。本文综述了近年来国内外采用连续化工艺制备生物柴油的研究进展。这些研究表明,通过优化反应器结构、使用助溶剂、提高催化剂活性等均可提高生物柴油的收率。最后本文还分析了各反应器存在的不足,并提出了相应的建议,对生物柴油连续化生产进行了展望,以期为低成本、低能耗的生物柴油生产提供参考。     

Intensified hydroformylation as an example for flexible intermediates production

One of the future challenges for chemical engineering is the design of flexible plants allowing an adaptation of production output to market development. Consequently, the target for the design of new processes must be the identification of equipment allowing such an expansion close to market development. To leverage the full benefit of this approach flexibility analysis has to be integrated into process design workflow. In this article the conventional technology for hydroformylation is compared to an intensified process design. This new design consists of a jet loop reactor followed by a membrane section to separate and recycle the homogenous catalyst. In the first part of the article it will be shown that process intensification leads to a net present value improvement of 30% compared to state of the art hydroformylation at a capacity of 100 kt/a. In the second part suitability of the intensified process for a stepwise plant expansion will be demonstrated. In an expansion scenario with two steps equivalent annual annuity is increased by 5% compared to a one step investment.     

NGD反应器气相流场及能耗特性研究

高倍率灰钙循环脱硫(NGD)技术具有投资和运行成本低、占地面积小、节水和可避免有色烟羽等优点,在燃煤工业锅炉领域具有较好的发展前景,而已有研究主要关注脱硫反应过程及其影响因素,尚缺乏对NGD反应器内流场和能耗的认识。笔者基于熵产分析方法建立了NGD反应器能耗的定量分析模型,NGD反应器能耗包含因烟气散热引起的能耗和黏性流体流动引起的能耗,其中,黏性流体流动引起的能耗包含湍流耗散和壁面摩擦,此外,由于NGD反应器高度达20 m以上,其进、出口压降还应考虑位置势能变化,因此,NGD进、出口压降包含位置势能变化、湍流耗散和壁面摩擦引起的压降。以某30 t/h煤粉工业锅炉配套的NGD反应器为研究对象,采用CFD方法模拟脱硫反应器内的流场分布,并在此基础上通过能耗分析模型研究脱硫反应器内的能耗组成和分布。结果表明,CFD方法和能耗分析模型计算的NGD进、出口压降与测量值的偏差分别为0.4%和9.6%,因此,CFD方法和能耗分析模型能较为准确地预测脱硫反应器内黏性流体流动引起的能耗,NGD反应器内黏性流体流动和烟气散热引起的能耗分别占NGD总能耗的96.2%和3.8%,可见黏性流体流动对NGD能耗起主导作用,位置势能变化、湍流耗散和壁面摩擦引起的压降分别为237.6、347.4和57.5 Pa,可见湍流耗散对NGD反应器能耗起主导作用。将NGD反应器划分为上部主体反应区、中部加速区和下部烟气入口区,由于黏性流体流动过程中的能量耗散来自不同流层速度差引起的摩擦耗散,因此能耗大小主要取决于不同流层间的速度梯度,而中部加速区平均速度较大且流场分布极不均匀,导致单位体积湍流熵产远高于其他区域,因此其体积虽仅占3.6%,但其熵产占NGD反应器总熵产的53.8%;上部主体反应区速度分布较为均匀且平均速度较小,但其体积占NGD反应器体积的83.3%,因此中部的熵产仍然较大,占总熵产的40.1%;下部烟气入口区流场分布极为不均匀但平均流速较小,单位体积熵产率从下往上逐渐增大,其体积比为13.1%,熵产占总熵产的比值为6.1%。可见,上部和中部是能耗的主要区域,尤其是中部加速区是降低NGD反应器能耗的主要目标区域。     

Ignition behaviour of different rank coals in an entrained flow reactor

An experimental study to determine the temperature and mechanism of coal ignition was carried out by using an entrained flow reactor (EFR) at relatively high coal feed rates (0.5 g min⁻¹). Seven coals ranging in rank from subbituminous to semianthracite, were tested and the evolved gases (O₂, CO, CO₂, NO) were measured continuously. The ignition temperature was evaluated from the gas evolution profiles, and it was found to be inversely correlated to the reactivity of the coal, as reflected by the increasing values of the ignition temperature in the sequence: subbituminous, high volatile bituminous, low volatile bituminous and semianthracite coals. The mechanism of ignition varied from a heterogeneous mechanism for subbituminous, low volatile bituminous and semianthracite coals, to a homogeneous mechanism for high volatile bituminous coals. A thermogravimetric analyser (TGA) was also used to evaluate coal ignition behaviour. Both methods, TGA and EFR, were in agreement as regards the mechanism of coal ignition. From the SEM micrographs of the coal particles retrieved from the cyclone, it was possible to observe the external appearance of the particles before, during and after ignition. The micrographs confirmed the mechanism deduced from the gas profiles.     

用于分布式制氢的甲烷蒸汽重整膜反应器的数值模拟

采用反应-分离集成的膜反应器进行分布式制氢,对简化工艺、降低能耗、提升技术经济性至关重要。本文采用数学模型对甲烷蒸汽重整制氢过程膜反应器进行模拟,系统分析了渗透侧操作策略、反应压力、反应温度、钯基膜性能、催化剂性能对反应器行为的影响;并以1m³/h甲烷最大程度转化为目标进行分布式制氢案例分析,详细比较膜反应器技术与“常规反应器+膜分离”工艺技术。结果表明,膜反应器在反应压力30atm（1atm=101325Pa）、反应温度500℃下操作可实现紧凑设计,比“常规反应器+膜分离”工艺技术具有明显优势,但是亟需研发更佳活性（10倍）的钯基膜和催化剂以实现显著的过程强化。模拟结果可为不同规模分布式制氢膜反应器的操作与设计及进一步的性能强化提供指导。     

A dynamic analysis of chalcopyrite bioleaching in continuous flow reactor systems

A dynamic analysis of chalcopyrite bioleaching was performed in continuous flow systems. In contrast to a previous batch analysis¹ in which the influence of particle surface area on reaction rate was not accounted for, the unsteady‐state change in particle surface area was integrated into the dynamic analysis by application of the modified PBM.² The current study extends the analysis to include the influence of convective flow on the system. It is demonstrated that the analysis can be used to determine feasible control strategies for operating near the steady‐state maximum rate that is stable. Two strategies were evaluated for the purpose of increasing the leaching rates, showing that an increased rate of 56% is feasible. Analysis on experimental data showed that increased rates can be achieved by controlling the biomass concentration and ferric:ferrous ion ratio at an optimum by increasing the solids loading [m/v] in the reactor. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2428–2440, 2012     

超重力多相催化反应器的研究进展

针对本征反应速率为快速反应的多相催化过程,其宏观反应速率一般受限于相间传质速率。基于超重力技术良好的传质强化特征,以及超重力装备关键机械部件在高温高压条件下稳定运行的突破,超重力反应器应用于多相催化反应,逐步展现了反应过程强化的潜力。本文主要对近年来本中心研制的超重力多相催化反应器在气液、气固以及气液固体系的研究进行综述,并对超重力多相催化反应器的发展前景进行了展望。     

Hydrodeoxygenation of HMF over Pt/C in a continuous flow reactor

The three‐phase hydrodeoxygenation reaction of 5‐hydroxymethylfurfural (HMF) with H₂ was studied over a 10 wt % Pt/C catalyst using both batch and flow reactors, with ethanol, 1‐propanol, and toluene solvents. The reaction is shown to be sequential, with HMF reacting first to furfuryl ethers and other partially hydrogenated products. These intermediate products then form dimethyl furan (DMF), which in turn reacts further to undesired products. Furfuryl ethers were found to react to DMF much faster than HMF, explaining the higher reactivity of HMF when alcohol solvents were used. With the optimal residence time, it was possible to achieve yields approaching 70% in the flow reactor with the Pt/C catalyst. Much higher selectivities and yields were obtained in the flow reactor than in the batch reactor because side products are formed sequentially, rather than in parallel, demonstrating the importance of choosing the correct type of reactor in catalyst screening. © 2014 American Institute of Chemical Engineers AIChE J, 61: 590–597, 2015