Enhanced lithium leaching from lepidolite in continuous tubular reactor using H_(2)SO_(4)+H_(2)SiF_(6) as lixiviant

An acidic mixture of sulfuric and fluosilicic acid(H_(2)SO_(4)+H_(2)SiF_(6))was employed as lixiviant to enhance leaching of lithium from lepidolite.The H_(2)SiF_(6) was obtained as a byproduct of anhydrous hydrofluoric acid production,aiming to provide HF molecules.It was found that the HF molecules were the main reaction component and played a key role in strengthening the dissolution of lepidolite.Different factors,including mass ratio of ore/H_(2)SO_(4)/H_(2)SiF_(6),concentrations of H_(2)SO_(4) and H_(2)SiF_(6),leaching temperatures(40−80℃)and time(15−75 min),were investigated.Moreover,an efficient tubular reactor was employed to improve this acid leaching system.Under the optimal conditions(ore/H_(2)SO_(4)/H_(2)SiF_(6) mass ratio of 1:0.8:1.6,80 wt.% H_(2)SO_(4),15 wt.% H_(2)SiF_(6),80℃,15 min),97.9% of Li,96.4% of K,97.6% of Rb,96.7% of Cs and 81.4% of Al(mass fraction)were leached.Additionally,a two-step thermal process was proposed to remove fluorine of leaching slurry.This acid treatment using an acidic mixture of H_(2)SO_(4) and H_(2)SiF_(6) in a continuous tubular reactor shows potential as an alternative process to extract lithium from lepidolite.

Modeling and Control of a Continuous Stirred Tank Reactor Based on a Mixed Logical Dynamical Model

A novel control strategy for a continuous stirred tank reactor(CSTR)system,which has the typical characteristic of strongly pronounced nonlinearity,multiple operating points,and a wide operating range,is initiated from the point of hybrid systems.The proposed scheme makes full use of the modeling power of mixed logical dy- namical(MLD)systems to describe the highly nonlinear dynamics and multiple operating points in a unified framework as a hybrid system,and takes advantage of the good control quality of model predictive control(MPC) to design a controller.Thus,this approach avoids oscillation during switching between sub-systems,helps to relieve shaking in transition,and augments the stability robustness of the whole system,and finally achieves optimal(i.e. fast and smooth)transition between operating points.The simulation results demonstrate that the presented ap- proach has a satisfactory performance.

Development of Linearizing Feedback Control with a Variable Structure Observer for Continuous Stirred Tank Reactors

This paper deals with the design of an observer-based nonlinear control for continuous stirred tank reactors(CSTR).A variable structure observer is constructed to estimate the whole process state variables.This observer is basically the conventional Luenberger observer with an additional switching term used to guarantee the robustness against modeling errors.The observer is coupled with a nonlinear controller,designed based on input-output linearization for controlling the reactor temperature.The asymptotical stability of the closed-loop system is shown by the Lyapunov stability theorem.Finally,computer simulations are developed for showing the performance of the proposed approach.

Continuous Flow Reactor for Hydroxylation of Benzene to Phenol by Hydrogen Peroxide

The direct hydroxylation of benzene to phenol catalyzed by activated carbon-supported Fe （Fe/AC） in acetonitrile using H2O2 as the oxidant was studied in a continuous flow reactor. Results showed that the continuous operation could obtain high phenol yield of 28.1%, coupled with the turnover frequency of 3 h^-1, and high selectivity of 98% under mild condition. The catalyst was characterized by N2 adsorption/desorption, Boehm titration, X-ray photoelectron spectra, and Fourier transform infrared spectroscopy. It was observed that iron may interact with the carboxyl group forming iron-carboxylate like species, which act as the active phase. The apparent activation energy obtained by fitting an Arrhenius model to the experimental data was 13.4 kJ/mol. The reaction order was calculated to be about i, 0.2 for benzene and 0.7 for H202.

Characterization of a 5 Litre Continuous Stirred Tank Reactor

Continuous Stirred Tank Reactors (CSTR) are used ubiquitously in chemical process industry for mixing, reactions and crystallizations. The purpose of this research is to study the effect of solute concentration (sodium chloride) on the stirrer speed in a CSTR. The experimental method used in this research is the stop watch and beaker method. The behavior pattern of the fluid in a CSTR can be experimentally verified as an alternative to the mathematical model. The tracer experiments were carried out. The effect of different parameters such as stirring speed, concentration at a steady time interval was analyzed. Experimental data obtained at 0.6 M and 160 rpm gave a curve that is in close agreement to that of theoretical or mathematical model. In other words, the results obtained at a concentration of 0.6 M and 160 rpm are in close agreement with that of early researchers. The paper is divided into five main sections: the first section immediately after the abstract is the introductory section that is basically a review of literature;the second section takes care of the materials and methods;the third section is the experimental procedure and this section takes the shut-down procedure and data processing into consideration;the fourth section is the discussion of experimental results and the last section is the conclusion of the paper.

Model identification of continuous stirred tank reactor based on QKLMS algorithm

The continuous stirred tank reactor(CSTR)is one of the typical chemical processes.Aiming at its strong nonlinear characteristics,a quantized kernel least mean square(QKLMS)algorithm is proposed.The QKLMS algorithm is based on a simple online vector quantization technology instead of sparsification,which can compress the input or feature space and suppress the growth of the radial basis function(RBF)structure in the kernel learning algorithm.To verify the effectiveness of the algorithm,it is applied to the model identification of CSTR process to construct a nonlinear mapping relationship between coolant flow rate and product concentration.In additiion,the proposed algorithm is further compared with least squares support vector machine(LS-SVM),echo state network(ESN),extreme learning machine with kernels(KELM),etc.The experimental results show that the proposed algorithm has higher identification accuracy and better online learning ability under the same conditions.

Comparison of Fe^(2+) oxidation by Acidithiobacillus ferrooxidans in rotating-drum and stirred-tank reactors

Fe2＋ oxidation by Acidithiobacillus ferrooxidans（At.ferrooxidans） under different solid contents by adding inert Al2O3 powder was examined in rotating-drum and stirred-tank reactors.The results show that the bioactivity of At.ferrooxidans in the stirred-tank is higher than that in the rotating-drum in the absence of Al2O3 powder,but the biooxidation rate of Fe2＋ decreases markedly from 0.23 g/（L·h） to 0.025 g/（L·h） with increasing the content of Al2O3 powder from 0 to 50%（mass fraction） in the stirred-tank probably due to the deactivation of At.ferrooxidans resulting from the collision and friction of solid particles.The increase in Al2O3 content has a little adverse effect on the bioactivity of At.ferrooxidans in the rotating-drum due to different mixing mechanisms of the two reactors.The biooxidation rate of Fe2＋ in the rotating-drum is higher than that in the stirred-tank at the same content of Al2O3 powder,especially at high solid content.The higher bioactivity of At.ferrooxidans can be maintained for allowing high solid content in the rotating-drum reactor,but its application potential still needs to be verified further by the sulfide bioleaching for the property differences of Al2O3 powder and sulfide minerals.

A safe and efficient process for the preparation of difluoromethane in continuous flow

Difluoromethane is typically produced vialiquid-phase fluorination as performed in a batch reactor.However,this process suffers from some problems,e.g.,severe corrosion of the reactor,high safety risk,and the regeneration of the catalyst.In this paper,a flow process as performed in the tubular reactor was designed.The optimum conditions for continuous synthesis of difluoromethane were obtained as follows:the reaction temperature was 100℃,the molar ratio of dichloromethane to hydrogen fluoride was 1.6:1 and the reaction time was 300 s.The operation of the cyclic process was stable for 24 h with the conversion per pass of hydrogen fluoride up to 16.2%.The unreacted raw materials were easily reused.The deactivation of the common catalyst,antimony pentachloride,was investigated by catalyst concentration curve and XPS analysis.The approach proposed in this work is proven to be safe,efficient and low amount of catalyst.

Reactive Flash Simulation of the Continuous Melt Transesterification Process of Polycarbonate

A model of the continuous melt transesterification process of bisphenol-A and diphenyl carbonate in a continuous stirred tank reactor to produce polycarbonate is presented. The model is developed by using the molecular species model of polycarbonate melt polycondensation and the modeling method of reactive flash. Liquid phase is treated as perfect mixed flow and the vapor phase is assumed following the ideal gas law. With this model, the continuous melt transesterification process of bisphenol-A and diphenyl carbonate is examined with respect to different orocess parameters.

Measurement,Modelling and Analysis of Residence Time Distribution Characteristics in a Continuous Hydrothermal Reactor

Understanding the residence time distribution(RTD)of a continuous hydrothermal reactor is of great significance to improve product quality and reaction efficiency.In this work,an on-line measurement system is attached to a continuous reactor to investigate the characteristics of RTD.An approach that can accurately fit and describe the experimental measured RTD curve by finding characteristic values is proposed for analysis and comparison.The RTD curves of three experiment groups are measured and the characteristic values are calculated.Results show that increasing total flow rate and extending effective reactor length have inverse effect on average residence time,but they both cause the reactor to approach a plug flow reactor and improve the materials leading.The branch flow rate fraction has no significant effect on RTD characteristics in the scope of the present work except the weak negative correlation with the average residence time.Besides,the natural convection stirring effect can also increase the average residence time,especially when the forced flow is weak.The analysis reveals that it is necessary to consider the matching of natural convection,forced flow and reactor size to control RTD when designing the hydrothermal reactor and working conditions.

Modeling of organic pollutant destruction in a stirred tank reactor by ozonation

Destruction of organic contaminants in water by ozonation is a gas-liquid process which involves ozone mass transfer and fast irreversible chemical reactions. Ozonation reactor design and process optimizing require the modeling of the gas-liquid interactions within the reactor. In this paper a theoretical model combining the fluid dynamic and reaction kinetic parameters is proposed for predicting the destruction rates of organic pollutants in a semi-batch stirred-tank reactor by ozonation. A simple expression for the enhancement factor as our previous work has been applied to evaluate the chemical mass transfer coefficient in ozone absorption. 2,4-dichlorophenol (2,4-DCP) and 2,6-DCP or their mixture are chosen as the model compounds for simulating, and the predicted DCP concentrations are compared with some measured data.

基于格子玻尔兹曼法的连续式搅拌反应釜流场数值模拟

为探究高含固厨余垃圾条件下连续式搅拌反应釜(continuousstirred-tankreactor,CSTR)的流场特性,课题组采用一种新颖的计算流体动力学方法格子玻尔兹曼法(latticeBoltzmannmethod,LBM)进行研究。模拟了3种桨型的流场特性,并通过对比不同转速下的扭矩实验值与模拟值,评估了该方法的可靠性,结果表明在低转速时实验值与模拟值的相对偏差均小于5%;随后考察了不同搅拌桨的速度分布、扭矩以及死区占比的变化情况。模拟结果显示:在处理含固体积分数为20%的厨余垃圾时,螺带式搅拌桨几乎带动整个反应釜内物料运动,并且其死区占比相对较小;使用螺带式搅拌桨时,随着转速的增加,反应釜中死区占比会有所下降。因此,综合考虑反应釜内的速度分布、扭矩及死区占比,用于搅拌高含固的厨余垃圾的连续式搅拌反应釜的最佳搅拌条件是转速为40r/min的螺带式搅拌桨。课题组所提出的格子玻尔兹曼法方法可用于模拟低转速条件下高含固厨余垃圾的流动特性。

Multistep continuous flow synthesis of Erlotinib

Erlotinib is an orally administered, highly effective, specific epidermal growth factor receptor tyrosine kinase inhibitor, used to treat non-small cell lung cancer and pancreatic cancer. The traditional synthetic methods for Erlotinib exhibit long reaction time and safety concern. Herein, we describe a novel five-step route for the synthesis of Erlotinib in flow. These five steps comprise etherification, nitration, reduction,addition and cyclization reactions. All steps were optimized and converted to continuous flow process,which drastically reduces the reaction time and considerably improves the process safety as well as the total yield. Enabled by five continuous flow units, Erlotinib is efficiently afforded with an E-factor of 38,an overall yield of 83%, and a total residence time of 25.1 min. Majority steps in this process have been optimized for quantitative conversion, which offers the possibility of telescoping the entire process.

萘硝化合成一硝基萘安全工艺研究

针对萘硝化间歇式反应存在反应时间长、收率低和风险高等问题,以萘为原料、浓硝酸为硝化剂、二氯乙烷为溶剂,提出了微通道反应器内合成一硝基萘的连续流工艺。考察了硝酸与萘摩尔比、反应温度、硝酸质量分数、反应停留时间4个因素对微通道连续反应的影响,验证了最佳工艺条件下微通道连续反应转化率和收率的稳定性,并对比分析了间歇式反应与微通道连续流反应的反应严重度。结果表明,硝酸与萘摩尔比为2∶1、反应温度为40℃、硝酸质量分数为85%、停留时间为96 s时微通道连续流反应效果最佳;最佳工艺条件下,微通道连续反应稳定,萘的转化率达到99.1%,一硝基萘的收率达到96.3%;间歇反应、微通道连续反应绝热温升分别为103.25℃和1.5℃,表明微通道连续流的萘一段硝化反应风险更低。

微通道反应器中炔烃的选择性催化半加氢反应研究进展

炔烃选择性催化半加氢反应与石油化工和精细化工生产密切相关,传统上多采用间歇工艺进行,存在自动化程度不高、反应效率低下以及安全隐患等问题。微通道反应器技术的进步使得以连续工艺进行炔烃选择性催化半加氢反应成为可能,有望从根本上解决间歇工艺所存在的问题。鉴于此,总结微通道反应器的类型以及相同反应器类型下催化剂的类别,对近年来微通道反应器中炔烃选择性催化半加氢反应的研究进展进行综述。微通道反应器包括催化毛细管反应器、填充床反应器、蜂窝反应器、独体反应器等,在炔烃选择性催化半加氢反应中的应用促进了石化领域生产技术与工艺的进步。总之,设备的微型化、过程的集成化是顺应可持续发展与高技术发展的需要,微通道反应器技术作为化工过程强化的一种新技术,在化学、化工、能源、环境等领域将会得到广泛的应用。

基于SMPT-1000的放热反应器控制系统

反应器是具有多扰动、强耦合、非线性的流程行业生产装置,反应温度、反应速度、进料流量、进料配比等对反应产物含量均有较大影响。针对化工过程常见的连续搅拌反应器放热反应过程,遵循安全、稳定、经济的原则,根据所给工程文件进行理论分析和控制系统设计开发。仿真结果表明:该控制方案具有良好的控制性能。

好氧颗粒污泥快速成粒的影响因素及在连续流反应器研究进展

从水力选择压、交替的盛宴-饥荒期间、接种污泥种类、微生物生长基质组成4个方面综述了影响好氧颗粒污泥的快速成粒因素。并结合以上因素综述了基于连续流反应器的好氧颗粒污泥培养的研究进展。介绍了现有AGS研究的局限性并对未来发展方向提出建议。

全混流反应器异常操作工况下反应温度预测方法及危害分析

采用数学拟合方法,根据不同温度下反应物含量变化的实验数据获取釜式反应器中主反应的动力学参数,根据加速量热仪法测定二次反应温度随时间的关系确定二次反应的动力学参数,并基于热量衡算和反应动力学研究建立全混流反应器(CSTR)的温度预测模型,研究了CSTR异常操作工况下反应温度的预测方法,并进行了危害分析。模拟结果显示,对常规n级放热反应,该模型可简单准确模拟不同操作条件下CSTR内操作参数随时间的变化关系,在换热失效条件下,反应温度最高可达130℃;所建立的模型可定量模拟异常工况下反应温度、组分含量及热负荷的变化,可为反应器异常操作工况下的反应危害分析提供数据支持,对反应工艺和反应器设计及本质安全的实现具有指导意义。

基于多智能体深度强化学习的解耦控制方法

[目的]在现代工业生产过程中,实现复杂非线性多输入多输出系统的解耦控制对于生产过程的操作和优化都具有至关重要的意义.[方法]本文基于多智能体深度确定性策略梯度(MADDPG)算法,提出了一种解决复杂非线性多输入多输出系统解耦控制问题的设计方案,并通过连续搅拌反应过程的解耦控制仿真计算,验证了设计方案的有效性.[结果]验证结果表明:本文所提出的方案能够同时对连续搅拌反应过程中反应温度、产物摩尔流量两个被控量的设定控制目标进行跟踪调节,且在同样的控制目标下,该设计方案比单智能体方案和PID(proportional-integral-derivative control)控制方案都具有更好的稳定性与更小的稳态控制误差.[结论]仿真结果表明:针对复杂非线性多输入多输出系统的解耦控制问题,多智能体强化学习算法能够在不依赖于过程模型的基础上,实现复杂非线性多输入多输出系统的解耦控制,并保证较好的控制性能.

Aerobic granules cultivated and operated in continuous-flow bioreactor under particle-size selective pressure

A novel method based on the selective pressure of particle size （particle-size cultivation method, PSCM） was developed for the cultivation and operation of aerobic granular sludge in a continuous-flow reactor, and compared with the conventional method based on the selective pressure of settling velocity （settling-velocity cultivation method, SVCM）. Results indicated that aerobic granules could be cultivated in continuous operation mode by this developed method within 14 days. Although in the granulation process, under particle-size selective pressure, mixed liquor suspended solids （MLSS） in the reactor fluctuated greatly and filamentous bacteria dominated the sludge system during the initial operation days, no obvious difference in profile was found between the aerobic granules cultivated by PSCM and SVCM. Moreover, aerobic granules cultivated by PSCM presented larger diameter, lower water content and higher specific rates of nitrification, denitrifieation and phosphorus removal, but lower settling velocity. Under long term operation of more than 30 days, aerobic granules in the continuous-flow reactor could remain stable and obtain good chemical oxygen demand （COD）, NH4^＋-N, total nitrogen （TN） and total phosphorus （TP） removal. The results indicate that PSCM was dependent on the cultivation and maintenance of the stability of aerobic granules in continuous-flow bioreactors.