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.

振荡管式连续流反应器制备生物柴油

利用振荡管式连续流反应器,通过大豆油和甲醇的酯交换反应连续制备生物柴油,采用单因素实验研究了反应温度、振荡频率、油相体积空速、醇油比和催化剂用量等因素对生物柴油收率的影响。结果表明,在反应温度为60℃、振荡频率为280次·min^(-1)、油相体积空速为5.1 h^(-1)、醇油比为8∶1、催化剂用量为1.0%的最佳条件下,生物柴油收率达到98.1%。

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.

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。

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。

连续管式反应器中降黏型聚羧酸减水剂的合成及性能

以异戊烯醇聚氧乙烯聚氧丙烯醚(IPEPPG)、2-甲基-2-(丁基三硫代碳酸酯基)丙酸(BTMP)和马来酸酐为主要反应原料,在连续管式反应器中利用热引发可逆加成-断裂链转移(RAFT)聚合,合成了1种窄相对分子质量分布的降黏型聚羧酸减水剂VR-PCE-TR。采用1HNMR、FTIR和GPC对VR-PCE-TR进行了表征,考察VR-PCE-TR对混凝土的工作性能和流变性能的影响,并与釜式反应器中采用常规水相自由基聚合制备的降黏型聚羧酸减水剂进行了性能对比。结果表明,当减水剂溶液质量分数为10%时,VR-PCE-TR具有最低表面张力(30.65 mN/m);当减水剂质量分数为0.8%时,VR-PCE-TR对水泥颗粒具有更高的吸附量(2.803 mg/g);在减水剂掺量(以水泥质量计,下同)0.13%时,掺加VR-PCE-TR后的水泥浆体具有更好的分散性和分散保持性;当减水剂掺量为0.4%时,掺加VR-PCE-TR后的水泥净浆具有更小的屈服应力(1.3 Pa)和更低的塑性黏度(0.26 Pa·s)。连续管式反应器避免了物料除氧步骤,能够保持聚合控制性和聚合反应速率,因此,制备的VR-PCE-TR具有更窄的相对分子质量分布(多分散性指数为1.19),进而有更好的降黏效果和应用性能。

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。

连续式咸淡水混合搅拌反应器混合性能研究

为合理开发利用咸水资源,优化农田灌溉设施前端连续式咸淡水混合搅拌反应器结构和运行参数,探究了搅拌转速和桨叶宽度对不同类型搅拌器咸淡水混合性能的影响。以直径为290 mm的双层桨叶搅拌器为研究对象,采用Realizable k-ε模型和欧拉多相流模型进行数值模拟并利用试验结果对其进行验证。系统分析不同搅拌器结构在不同搅拌转速和桨叶宽度下的湍动能、速度流场、咸水体积分数分布、混合均匀所需时间及搅拌器功耗,发现随着搅拌转速和桨叶宽度增加,三叶开启式搅拌器与组合锚式搅拌器湍动能和液体流速均增加,反应釜内咸水体积分数也随之发生显著变化,到达混合均匀状态所需时间缩短,出口处咸水均匀度和搅拌器功率均呈上升趋势。整体来说,转速对上述指标的影响较桨叶宽度更为显著,另外,2种搅拌器类型中相关指标受转速和桨叶宽度变化的影响差异明显。与三叶开启式搅拌器相比,组合锚式搅拌器达到完全混合均匀状态所需时间最小值虽然低6.8%,但其搅拌功耗却高10%左右。综合考虑灌溉作物水量需求、混合效率和设备能耗等因素,推荐采用较低转速(90 r/min)、宽桨叶(50 mm)的三叶开启式搅拌器,该配置在咸淡水混合过程中能够有效保障混合效率,并在连续混合设备中有效控制能耗的同时满足实际应用需求。研究结果可为连续式咸淡水混合搅拌反应器设计优化提供参考。

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.

无挡板CSTR内部流场及颗粒分布的CFD模拟研究

为探究无挡板连续搅拌式反应釜(CSTR)内部流场分布及颗粒运动情况,采用计算流体力学(CFD),在欧拉-拉格朗日模型的基础上对三种搅拌釜工况进行了研究分析。同时,探讨了粒径为100,300和500μm的颗粒在各个工况下的混合情况。研究表明:在时间为0~100 s时,初始搅拌釜内颗粒的平均速度相较于初始时增加了39.22%,达到了1.4797 m/s,搅拌釜内的流场平均速度为1.7372 m/s,颗粒的平均速度与流场速度呈现相近的趋势;搅拌桨位于罐内中间位置时,颗粒分布最为均匀;采用双层搅拌桨时,颗粒速度得到了显著的提升,最大颗粒速度可达到4.2383 m/s。