转子-径隙式水力空化反应器空化性能优化研究

旋转型水力空化反应器因其空化强度大,空化率高,已被广泛应用于杀菌消毒,污水处理等工业领域。文章提出一种弧形转子,通过数值计算分析弧形转子与原转子在不同转速下反应器内部空化性能,分析定子与转子之间的相互作用,研究改变弧形转子叶片入口安装角对反应器内部空化性能的影响。结果表明,在不同转速下,弧形转子均极大提高反应器内部空化强度,提高空化率。转子区域,空化发生于转子叶片吸力面,与低压区相对应;定子区域,转子叶片转过定子盲孔时,对流体进行强剪切,盲孔内部与进出口分离区压力降低涡量增大,发生剪切空化以及涡空化。增大叶片入口安装角度可以极大增加空化强度,提高反应器性能。

转子-径隙式水力空化反应器的空化诱导噪声脉动特性研究

旋转式水力空化反应器作为一种高效产生空化气泡的设备被广泛应用于工业领域,其空化诱导噪声是其性能评估和目标优化的重中之重。研究了一种转子-径隙水力空化反应器的空化及其诱导噪声特性,对不同转子转速下的非定常空化流场进行了数值模拟;研究了空化与其诱导噪声脉动特性的相互作用机制,分析了空化诱导噪声的时频分布特性。结果表明,转速3300~3900 r/min,转子吸力面涡度由5960 s-1上升至7155 s-1,转子入口圆周涡度由6142 s-1上升至7597 s-1,这种提升表现为高涡度区沿压力面方向和入口圆周方向扩张;转速为3300 r/min下反应器噪声沿反应器内部环形流动方向,其噪声叶频脉动幅值经历了增长—稳定—降低3个阶段,其中,在蜗舌和流体出口位置,P8至P1的噪声叶频及其多阶谐频幅值均有不同程度降低;剧烈的空化致使出口位置空化诱导噪声的幅值不增反降,最终表现为出口位置噪声叶频及其多阶谐频幅值的降低,这是由于强空化状态下超空泡周期性溃灭量小于弱空化状态,空化气泡长期存在而非周期性溃灭。

自激离心式空化反应器空化及噪声特性研究

水力空化被广泛应用于杀菌消毒、乳液制备等工业领域,而高效的水力空化反应器是实现水力空化应用的基础。以一种自激离心式水力空化反应器为研究对象,基于Rrealizableκ-ε湍流模型和Zwart-Gerber-Belamri空化模型,对设计工况下反应器三维瞬态非定常流动的空化流场和声场特性进行数值模拟,分析不同液面高度下空化发展状态,研究反应器不同位置空化噪声脉动和发展情况。结果表明:不同液面高度的转子空化特性具有明显差别。随着液面高度的上升,空化区域持续增加,但是液面上升后期空泡发展空间过大,整体空化强度无法匹配发展空间,强空化区面积呈现先上升后下降的趋势,在液面高度为3~4 mm之间时达到最大值,弱空化区面积持续增长。空化是影响反应器叶频及其多阶谐频噪声的重要因素。顺着流动方向,反应器内部声压的叶频幅值随着空化的发展而增加,呈现升高-稳定-降低的周期性变化。

文丘里管空化反应器的空化特性研究

文丘里管空化反应器广泛应用于水处理领域,深入研究其空化特性,对进一步提升其应用水平具有重要意义。文章建立了15个不同喉部直径和入口锥角的文丘里管空化反应器的数值模型,利用数值模拟结果计算了空化出生位置的空化数,分析了空化数变化情况及其与气含率、入口锥角、喉部直径的变化关系。结果表明:喉部直径为3 cm和入口锥角18°的文丘里管时空化数最低、气含率最大,为空化程度最好的模型;喉部直径对空化数和气含率的影响比入口角度的影响大;选择最优喉部直径或者喉部直径固定后调整入口锥角,可以促进空化现象的发生、降低空化发生所需要的能耗。

自激离心式水力空化反应器的空化特性研究

水力空化技术已广泛应用于污水处理、杀菌消毒等工业领域。文章提出了一种自激离心式水力空化反应器,并数值模拟不同转速下的反应器空化特性,研究其内部空化反应机理,分析不同转速对各结构空化效果的影响及原因。结果表明:在转子区域,空化初生于叶片进口,稳定时在入口圆周方向、出口角方向和压力面方向呈现周期性发展;在定子盲孔区域,空泡由转子诱导至盲孔区域,因其特殊位置和结构激发发展,漩涡位置是影响其空化效果的重要因素,适当提高转速可以通过提高漩涡深度有效提高定子的空化效果;对所提出的自激离心式水力空化反应器整体而言,高转速情况下可以增加空化强度和空化范围,其空泡体积更大而空化效果更好,在3600~4320 r/min的范围内提高转速能取得更好的效果。

水力空化强化碳化反应制备碱式碳酸镁的实验研究

为了强化微观混合和传质,提高Mg(OH)_(2)碳化率,采用水力空化技术强化Mg(OH)_(2)与CO_(2)碳化反应生成中间产物Mg(HCO_(3))_(2),再经过热解制备碱式碳酸镁[4Mg CO_(3)·Mg(OH)_(2)·4H_(2)O],设计正交试验考察Mg(OH)_(2)碳化率的影响因素。通过扫描电子显微镜、X射线衍射仪和多参数测试仪等对产物进行表征。研究结果表明,Mg(OH)_(2)碳化率影响因素由大到小顺序依次为入射角α、CO_(2)流量q、Mg(OH)_(2)固含量s、入口压力p、喉径d_(0)、碳化时间t。在α=60°、d_(0)=4 mm、p=0.35 MPa、t=60 min、s=1.6%、q=17 L/min的工艺条件下碳化率为92.1%,比鼓泡搅拌反应器的碳化率(60.53%)高31.57%。产物4Mg CO_(3)·Mg(OH)_(2)·4H_(2)O中杂质(如Ca O、Fe)含量降低;制备的4Mg CO_(3)·Mg(OH)_(2)·4H_(2)O呈均匀片状结构,晶体厚度小于50 nm;产品结晶良好,组成相对稳定单一,所得产物的各个衍射峰峰位都与标准六方晶型的碱式碳酸镁衍射峰峰位完全一致。

水力空化降解亚甲基蓝反应动力学分析

为探究水力空化对有机物的降解反应速率,在不同入口压力下,采用不同结构的孔板空化反应器进行了亚甲基蓝降解动力学研究。结果表明,较高的入口压力会增大水力空化对亚甲基蓝的降解反应速率;多孔孔板空化器降解亚甲基蓝的效果优于单孔孔板空化器,并且孔数越多空化效果越强。孔板空化器作用下的亚甲基蓝降解过程均符合一级反应动力学,反应速率由大到小为49孔>25孔>单孔,半衰期由小到大为49孔<25孔<单孔。

基于水力空化的化工过程强化研究进展

水力空化(HC)是一种利用声化学效应(即空泡溃灭时释放出的巨大能量)的高效、绿色化工过程强化技术,是国内外的研究热点。该技术具有设备造价低、可放大性强、可与其他物理及化学方法高效耦合等优点,工业应用前景广泛。本文介绍了HC现象及其特性;归纳了近年来HC技术在有机废水处理、水消毒与生物燃料制备等代表性应用的研究、应用进展以及作用机理,展示了其工业应用的潜力;总结了用于诱发HC现象的水力空化反应器的发展过程与研究现状;最后,结合发展趋势与作者的研究经历,归纳了国内外在HC研究方面存在的问题,指出了其未来发展方向,为HC技术的发展与工业应用探索提供建设性意见。

孔板水力空化对双酚A去除研究

为了探究孔板空化反应器对双酚A（BPA）的降解效果，在相同的条件下，采用不同的孔板空化器对BPA的去除进行动力学研究。结果表明，入口压力对BPA的去除具有双重影响，最佳的入口压力为0．3MPa。对于B相同而孔径不同的孔板空化器，孔径越小，空化效果越好。a值相同，孔径相同时，孔数越多或孔周长越大，BPA去除率越大。相同的条件下，交叉布孔的孔板空化器的空化效果更好。孔板空化器作用下的BPA去除过程均符合一级反应动力学，反应速率大小为2号〉1号〉3号〉4号〉5号，2号孔板的空化效果更好，其反应速率常数为0．12879h^-1。

Effect of preparation routes on activity of Ag-MnO_x/C as electrocatalysts for oxygen reduction reaction in alkaline media

The effect of preparation routes on the physical characteristics and activity of the Ag-MnOx/C composites toward the oxygen reduction reaction （ORR） in alkaline media were studied by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, transmission electron microscopy （TEM）, energy-dispersion spectroscopy （EDS） as well as scanning electron microscopy （SEM） and electrochemical techniques. The results show that more Ag and Mn species present on the surface of the Ag-MnOx/C composite prepared by two-step route （Ag-MnOx/C-2） compared to the one prepared by one-step route （Ag-MnOx/C-1）, which contributes to its superior activity toward the ORR. The higher electron transfer number involved in the ORR can be observed on the Ag-MnOx/C-2 composite and its specific mass kinetic current at -0.6 V （vs Hg/HgO） is 46 mA/μg, which is 23 times that on the Ag/C. The peak power density of zinc-air battery with the Ag-MnOx/C-2 air electrode reaches up to 117 mW/cm^2.

The pivotal effects of oxygen vacancy on Bi_2MoO_6:Promoted visible light photocatalytic activity and reaction mechanism

Bi2MoO6,a typical Bi-based photocatalyst,has received increasing interests and been widely applied in various fields.However,the visible light photocatalytic activity of Bi2MoO6 is still restricted by some obstacles,such as limited photo-response and low charge separation efficiency.In this work,we developed a facile method to introduce artificial oxygen vacancy into Bi2MoO6 microspheres,which could effectively address these problems and realize highly efficient visible light photocatalysis.The experimental and theoretical methods were combined to explore the effects of oxygen vacancy on the electronic structure,photocatalytic activity and the reaction mechanism toward NO removal.The results showed that the addition of NaBH4 during catalyst preparation induced the formation of oxygen vacancy in Bi2MoO6,which plays a significant role in extending the visible light absorption of Bi2MoO6.The visible light photocatalytic activity of Bi2MoO6 with oxygen vacancy was obviously enhanced with a NO removal ratio of 43.5%,in contrast to that of 25.0%with the pristine Bi2MoO6.This can be attributed to the oxygen vacancy that creates a defect energy level in the band gap of Bi2MoO6,thus facilitating the charge separation and transfer processes.Hence,more reactive radicals were generated and participated in the photocatalytic NO oxidation reaction.The in situ FT-IR was used to dynamically monitor the photocatalytic NO oxidation process.The reaction intermediates were observed and the adsorption-reaction mechanism was proposed.It was found that the reaction mechanism was unchanged by introducing the oxygen vacancy in Bi2MoO6.This work could provide new insights into the understanding of the oxygen vacancy in photocatalysis and gas-phase photocatalytic reaction mechanism.

Tailoring Oxygen Vacancy on Co3O4 Nanosheets with High Surface Area for Oxygen Evolution Reaction

Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here, we designed an efficient Co304 electrocatalyst using a pyrolysis strategy for oxygen evolution reaction （OER）. Morphological characterization confirmed the ultra-thin structure of nanosheet. Further, the existence of oxygen vacancies was obviously evidenced by the X-ray photoelectron spectroscopy and elec- tron spin resonance spectroscopy. The increased surface area of Co3O4 ensures more exposed sites, whereas generated oxygen vacancies on Co3O4 surface create more active defects. The two scenarios were beneficial for accelerating the OER across the interface between the anode and electrolyte. As expected, the optimized Co3O4 nanosheets can catalyze the OER eftciently with a low overpotential of 310 mV at current density of 10 mA/cm2 and remarkable long-term stability in 1.0 mol/L KOH.

A novel process integrating vacuum distillation with atmospheric chlorination reaction for flexible production of tetrachloroethane and pentachloroethane

In this paper, we developed a novel process integrating vacuum distillation with atmospheric chlorination reaction(VD-ACR) to realize the flexible production of tetrachloroethane(TeCA) and pentachloroethane(PCA)from 1,2-dichloroethane(DCA). During the simulation, the distillation column and reactors were operated for separation and chlorination respectively under variable pressures and temperatures. It is interesting to note that VD-ACR processes producing pure TeCA or PCA can exhibit the similar configuration parameters after optimization, which enables the flexible production of TeCA and PCA with different molar ratios via changing operating parameters. The molar ratio of TeC A/PCA can be fine-tuned within the range of 0.9:0.1-0.1:0.9 through adjusting the amount of chlorine pumped into side reactors, giving rise to the increase of the heat duty of reboiler by five times. A pilot-scale experiment was then operated based-upon this VD-ACR process and the result matched well with the simulation. Therefore, the VD-ACR model presented in this study will be beneficial for the industrial-scale flexible production of TeCA and PCA from DCA.

Deactivation Behavior of Hollow Titanium Silicalite Zeolite in Aqueous Ammonia Solution under Simulated Industrial Cyclohexanone Ammoximation Conditions

For simulating the real deactivation of hollow titanium silicalite(HTS) zeolite in commercial ammoximation process, HTS was treated by 10% NH_3·H_2O solution at 120 ℃ in stirred autoclave. It is found that a part of HTS zeolite crystals dissolved in the hot NH_3·H_2O solution, and the specific surface area and pore volume continuously decreased with the increase in NH_3 hydrothermal treatment time. Meanwhile, the transformation of framework Ti species into extraframework Ti species was detected by the spectroscopic methods. However, the extraframework Ti species were still in a highly dispersed state after the hydrothermal and thermal treatments as shown by TEM images, while the formation of new acid sites was not detected. Upon combining the results of characterization with catalytic performance of HTS, the main deactivation reason for this material had been determined, which might be attributed to the reduction of specific surface area and active centers after basic treatment and calcination of HTS samples. And then the possible mechanism of simulated deactivation of HTS zeolite was proposed, which could describe the elemental reaction steps much more visually and directly.

Modeling of a SrCe_(0.95)Yb_(0.05)O_3-αHollow Fibre Membrane Reactor for Methane Coupling

Proton-hole mixed conductor, SrCeo.95Yb0.05O3-α(SCYb), has the potential to be used as a membrane for dehydrogenation reactions such as methane coupling due to its high C2-selectivity and its simplicity for fabricating reactor systems. In addition, the mixed conducting membrane in the hollow fibre geometry is capable of providing high surface area per unit volume. In this study, mechanism of methane coupling reaction on the SCYb membrane was proposed and the kinetic parameters were obtained by regression of experimental data. A mathematical model describing the methane coupling in the SCYb hollow fibre membrane reactor was also developed. With this mathematical model, various operating conditions such as the operation mode, operation pressure and feed concentrations affecting performance of the reactor were investigated. The simulation results show that the cocurrent flow in the reactor exhibits higher conversion of methane and higher yield of ethylene compared to the countercurrent flow. In order to achieve the highest C2 yield, especially of ethylene, pure methane should be used as feed and the operating pressure be 300 kPa. Air can be used as the source of oxygen for the reaction and its optimum feed velocity is twice of the methane feed velocity. The air pressure in the lumen side should be kept the same as or slightly lower than the pressure of shell side.

Synthesis,characterization and application of BiVO_4 photoanode for photoelectrochemical oxidation of chlorate

A high‐quality polycrystalline bismuth vanadate(BiVO4)film was prepared on a fluorine‐doped tinoxide substrate via a facile two‐step strategy involving electrodeposition and annealing processes.The morphology and structural characterization of the resulting film were investigated by differentmethods including scanning electron microscopy,transmission electron microscopy,X‐ray diffraction(XRD),and Fourier transform infrared,ultraviolet‐visible(UV‐vis)absorption,and Ramanspectroscopies.XRD patterns as well as optical measurements revealed that BiVO4film crystallizedwith a pure monoclinic scheelite structure.The prepared BiVO4film was used for heterogeneousoxidation of chlorate ions in aqueous solution via electrochemical(EC),photochemical(PC),andphotoelectrochemical(PEC)processes.The decrease in concentration of chlorate was monitoredusing UV‐vis absorption spectroscopy.The results revealed that BiVO4could effectively performchlorate oxidation under light irradiation through a PEC method.The kinetics of chlorate oxidationwas consistent with a first‐order reaction,and the rate constant for the PEC process was found to bemuch higher than those of EC and PC.Furthermore,a possible photocatalytic oxidation mechanismfor chlorate mainly based on the formation of perchlorate ions is proposed.

Bifunctional electrocatalysts for rechargeable Zn-air batteries

Zn-air batteries have attracted extensive attention for their unique features including high energy density,safety,low cost and environmental friendliness.However,due to their poor chargeability and low efficiency,the practical application remains a challenge.The main obstacles are the intrinsic slow reaction kinetics on air cathodes,including oxygen reduction reaction during the discharging process and oxygen evolution reaction during the recharging process.Searching for efficient bifunctional oxygen electrocatalysts is key to solve these problems.In this review,the configuration and fundamental oxygen electrochemical reactions on air cathodes are briefly introduced for Zn-air batteries first.Then,the latest bifunctional oxygen electrocatalysts are summarized in detail.Finally,the perspectives are provided for the future investigations on bifunctional oxygen electrocatalysts.

Study on the catalyst in the decomposition reaction for BI organic waste water to adipic acid

The influences of kinds and level of catalyst, time of decomposition reaction on the distribution of dibasic acid and apparent yield of adipic acid were researched; the acidic washing waste water （BI waste water） producing from the equipment of cyclohexane oxidation by air was as stuff, the component of products by decomposed and oxidated in different conditions were analysed. It indicated that in the presence of cobalt salt the apparent yield of adipic acid was upto 10%-12% for the total BI waste water after the concentrated BI waste water refluxed for two hours, and then oxidated by nitric acid.

Preparation and properties of transition metal nitrides caged in N-doped hollow porous carbon sphere for oxygen reduction reaction

A series of transition metal nitrides(MxNy,M=Fe,Co,Ni)nanoparticle(NP)composites caged in N-doped hollow porous carbon sphere(NHPCS)were prepared by impregnation and heat treatment methods.These composites combine the high catalytic activity of nitrides and the high-efficiency mass transfer characteristics of NHPCS.The oxygen reduction reaction results indicate that Fe2N/NHPCS has the synergistic catalytic performance of higher onset potential(0.96 V),higher electron transfer number(~4)and higher limited current density(1.4 times as high as that of commercial Pt/C).In addition,this material is implemented as the air catalyst for zinc−air battery that exhibits considerable specific capacity(795.1 mA·h/g)comparable to that of Pt/C,higher durability and maximum power density(173.1 mW/cm2).

Carbothermic reduction of alumina with carbon in vacuum

Carbothermic reduction alumina in vacuum was conducted, and the products were analysed by means of XRD and gas chromatography. Thermodynamic analysis shows that in vacuum the initial carbothermic reduction reaction temperature reduces compared with that under normal pressure, and the preferential order of products is Al404C, Al4C3, Al2OC, Al20 and A1. Experiment results show that the carbothermic reduction products of alumina are A1404C and A14C3, and neither A12OC, Al20 or Al was found. During the carbothermic reduction process, the reaction rate of Al203 and carbon decreases gradually with increasing time. Meanwhile, lower system pressure or higher temperature is beneficial to the carbothermic reduction of alumina process. A1404C is firstly formed in the carbothermic reaction, and then A14C3 is formed in lower system pressure or at higher temperature.