Removing chlorine of CuCl residue from zinc hydrometallurgy by microwave roasting

Most Zn hydrometallurgy factories adopt Cu2SO4 as a dechlorination reagent from zinc solution nowadays, thus much CuCl residue is produced. The existing process of treating this residue is washing with water or sodium carbonate solution, which would cause a lot of troubles to water treatment and waste discharge. A method of microwave roasting was adopted for dechlorination of CuCl residue. A 1.5 kW microwave roasting equipment with dust collection and tail gas adsorption systems was set up and applied during the experiment. By investigating the effect of temperature, heat preservation time, moisture content of raw material and grain size of samples on the dechlorination, the optimal experimental condition is obtained. When the samples with 2% moisture and <150 μm grain size are microwave roasted at 400 °C for 2 h, the Cl content turns from 14.27% to 1.35% and the dechlorination rate is as high as 90%, while that with conventional heating is only 60%-80%. The phase change of the roasting process investigated with X-ray diffraction verifies that CuCl in CuCl residue is removed by being transformed into CuO.

Self-adaptive PID controller of microwave drying rotary device tuning on-line by genetic algorithms

The control design, based on self-adaptive PID with genetic algorithms(GA) tuning on-line was investigated, for the temperature control of industrial microwave drying rotary device with the multi-layer(IMDRDWM) and with multivariable nonlinear interaction of microwave and materials. The conventional PID control strategy incorporated with optimization GA was put forward to maintain the optimum drying temperature in order to keep the moisture content below 1%, whose adaptation ability included the cost function of optimization GA according to the output change. Simulations on five different industrial process models and practical temperature process control system for selenium-enriched slag drying intensively by using IMDRDWM were carried out systematically, indicating the reliability and effectiveness of control design. The parameters of proposed control design are all on-line implemented without iterative predictive calculations, and the closed-loop system stability is guaranteed, which makes the developed scheme simpler in its synthesis and application, providing the practical guidelines for the control implementation and the parameter design.

Optimization of processing parameters for microwave drying of selenium-rich slag using incremental improved back-propagation neural network and response surface methodology

In the non-linear microwave drying process,the incremental improved back-propagation (BP) neural network and response surface methodology (RSM) were used to build a predictive model of the combined effects of independent variables (the microwave power,the acting time and the rotational frequency) for microwave drying of selenium-rich slag.The optimum operating conditions obtained from the quadratic form of the RSM are:the microwave power of 14.97 kW,the acting time of 89.58 min,the rotational frequency of 10.94 Hz,and the temperature of 136.407 °C.The relative dehydration rate of 97.1895% is obtained.Under the optimum operating conditions,the incremental improved BP neural network prediction model can predict the drying process results and different effects on the results of the independent variables.The verification experiments demonstrate the prediction accuracy of the network,and the mean squared error is 0.16.The optimized results indicate that RSM can optimize the experimental conditions within much more broad range by considering the combination of factors and the neural network model can predict the results effectively and provide the theoretical guidance for the follow-up production process.

Numerical modeling dynamic process of multi-feed microwave heating of industrial solution media

The exothermic efficiency of microwave heating an electrolyte/water solution is remarkably high due to the dielectric heating by orientation polarization of water and resistance heating by the Joule process occurred simultaneously compared with pure water.A three-dimensional finite element numerical model of multi-feed microwave heating industrial liquids continuously flowing in a meter-scale circular tube is presented.The temperature field inside the applicator tube in the cavity is solved by COMSOL Multiphysics and professional programming to describe the momentum,energy and Maxwell's equations.The evaluations of the electromagnetic field,the temperature distribution and the velocity field are simulated for the fluids dynamically heated by singleand multi-feed microwave system,respectively.Both the pilot experimental investigations and numerical results of microwave with single-feed heating for fluids with different effective permittivity and flow rates show that the presented numerical modeling makes it possible to analyze dynamic process of multi-feed microwave heating the industrial liquid.The study aids in enhancing the understanding and optimizing of dynamic process in the use of multi-feed microwave heating industrial continuous flow for a variety of material properties and technical parameters.

Non-isothermal microwave leaching kinetics and absorption characteristics of primary titanium-rich materials

The non-isothermal leaching kinetics of primary titanium-rich material by microwave heating was investigated,and the temperature-pressure curves of leaching system and microwave absorption characteristics of mixture solutions before and after leaching were measured.The research of non-isothermal kinetics was evaluated by the leaching rate of Fe and the total apparent velocity equation of the non-isothermal kinetics of leaching for primary titanium-rich material by microwave heating was obtained.It is shown from the temperature-pressure curves that the high temperature and high pressure of closed leaching system are favorable to the enhancement of the leaching rate of Fe.Microwave absorption characteristics of mixture solutions before and after leaching show that there are abrupt changes of microwave absorption characteristics for 15%HCl solution and the mixture solution after leaching by 20%HCl.

Preparation of microsized hematite powder from ferrous sulfate via microwave calcination

The preparation of microsized hematite powder from ferrous sulfate using microwave calcination was investigated based on the TG/DTG curves. The decomposition of industrial ferrous sulfate under air atmosphere was divided into three stages, and a ferrous sulfate sample added with 15% Fe_2O_3 could strongly absorb microwave energy. Therefore, preparing hematite powder from ferrous sulfate using microwave calcination was feasible. Hematite was obtained under the following optimized conditions: calcination temperature, 850 °C; microwave power, 650 W; and sample amount, 40 g. The obtained hematite satisfied the first-grade quality requirements. The total ferrum value was more than 58%, and the total sulfur and phosphorus contents were less than 0.5% and 0.2%, respectively. X-ray powder diffraction and scanning electron microscopy were used to characterize the structure and morphology of microsized hematite powder. The particles were non-spherical in shape, and the average particle size distribution was 10.45 μm. This work provides new potential applications for waste ferrous sulfate.

Regeneration of waste activated carbon after extracting gold with steam under microwave heating:Optimization using response surface methodology

The technology that waste activated carbon after extracting gold is regenerated with steam under microwave heating was studied.The influence of the activation temperature,activation duration and steam flow rate on iodine adsorption value and regeneration yield of activated carbon was investigated.The response surface methodology(RSM) technique was utilized to optimize the process conditions.The optimum conditions for the preparation of activated carbon are identified to be activation temperature of 831 °C,activation duration of 40 min and steam flow rate of 2.67 mL/min.The optimum conditions result in an activated carbon with an iodine number of 1048 mg/g and a yield of 40%,and the BET surface area evaluated using nitrogen adsorption isotherm is 1493 m2/g,with total pore volume of 1.242 cm3/g.And the pore structure of activated carbon regenerated is mainly composed of micropores and a small amount of mesopores.

Dielectric Characterization and Microwave Roasting of Molybdenite Concentrates at 915 MHz Frequency

The magnetic hysteresis loop was measured to know the magnetic property of molybdenite concentrate.In order to evaluate its microwave absorption capacity, the dielectric properties of molybdenite concentrate was investigated using cavity perturbation method at 915 MHz dependent on densities and temperatures.The parameter data were fitted using regression fit and a model related to the same density and temperature ranges was developed.A nonlinear surface fitting was used to present visually the effect of dielectric parameters on the microwave penetrate depth of molybdnite concentrate.The crystal products of MoO 3 obtained from microwave roasting at different temperatures were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD).The results show both the dielectric constants and loss factors increase in the increase of apparent densities and temperatures with different growth rates in the experimental range.Due to the distinguished trend of dielectric performance dependent on temperatures, two parts in the heating scenario for the molybdenite concentrate samples were divided.The microwave penetration depth is inversely proportional to both apparent densities and temperatures.The nonlinear fitting surfaces indicate the increase of dielectric loss provides an enough decrease in microwave penetration depth.In contrast, the dielectric constant has a positive effect for it.Pure MoO 3 was produced at 800 ℃ by using microwave energy.This work can be helpful to design and simulate microwave system for efficient beneficiation of molybdenite concentrate and to prepare molybdenum products from this concentrate.

Process optimization for treatment of methyltin mercaptide effluents using modified semi-coke

The central composite process optimization was performed by response surface methodology technique using a design for the treatment of methyltin mercaptide with modified semi-coke. The semi-coke from the coal industry was suitably modified by treating it with phosphoric acid, with a thermal activation process. The objective of the process optimization is to reduce the chemical oxygen demand(COD) and 4NH—N in the methyltin mercaptide industrial effluent. The process variables considered for process optimization are the semi-coke dosage, adsorption time and effluent pH. The optimized process conditions are identified to be a semi-coke dosage of 80 g/L, adsorption time of 90 min and a pH value of 8.34. The ANOVA results indicate that the adsorbent dosage and pH are the significant parameters, while the adsorption time is insignificant, possibly owing to the large range of adsorption time chosen. The textural characteristics of modified semi-coke were analyzed using scanning electron microscopy and nitrogen adsorption isotherm. The average BET surface area of modified semi-coke is estimated to be 915 m2/g, with the average pore volume of 0.71 cm3/g and a average pore diameter of 3.09 nm, with micropore volume contributing to 52.36%.

Effects of microwave pretreatment on zinc extraction from spent catalyst saturated with zinc acetate

A new technology for microwave pretreatment of spent catalyst on Zn extraction by HCl leaching was proposed and the temperature-change curve of spent catalyst under microwave irradiation was measured.The influence of microwave pretreatment temperature and microwave irradiation time on zinc extraction was investigated and the mechanism of microwave pretreatment for spent catalyst was analyzed.The results show that microwave pretreatment can greatly enhance the leaching rate of Zn.The Zn extraction reaches 96.58%under the conditions of microwave pretreatment temperature of 950℃and the microwave irradiation time of 12 min.The blocked pores of spent catalyst can be opened through microwave pretreatment,increasing the contact area of leaching reagent and zinc.

Dielectric Properties and Microwave Heating of Molybdenite Concentrate at 2.45 GHz Frequency

Dielectric properties were measured using cavity perturbation method. The temperature rising behaviors of molybdenite concentrate were investigated in the field of microwave. This process was conducted to show the microwave absorption properties of molybdenite concentrate and the feasibility of microwave roasting molybdenite concentrate to prepare high purity MOO3. The dielectric constant,dielectric loss,and loss tangent increase from 3. 51 to 5. 04,0. 22 to 0. 51 and 0. 065 to 0. 102 respectively. They are proportional to the apparent density of molybdenite concentrate in the range of 0. 9-1. 4 g/cm3. The results show that the molybdenite concentrate has good microwave absorption capacity in the conventional density range. The temperature rising curves show that the apparent heating rate of the molybdenite concentrate increases with the increase in microwave power and decreases with the increase in the sample mass and thickness. The temperature of concentrate sample of 100 g reaches approximately 800 ℃ after 5 min of microwave treatment at 0. 5 kW of power. Our findings show that it is feasible to prepare high-purity MOO3from molybdenite concentrate by microwave roasting.

Dechlorination of zinc dross by microwave roasting

Traditional treatments of zinc dross have many disadvantages,such as complicated recovering process and serious environmental pollution.In this work,a new process of chlorine removal from zinc dross by microwave was proposed for solving problem of recycling the zinc dross.With better ability of absorbing the microwave than zinc oxide,the main material in zinc dross,chlorides,can be heated and evaporated rapidly during microwave roasting.Various parameters including roasting temperature,duration time and stirring speed were optimized.The microstructure of roasted materials was characterized by X-ray diffraction(XRD) and scanning electron microscope(SEM).The content of the chloride was analyzed by the method of chlorine ion selective electrode.The experiments indicate that the best duration time is 60 min with a stirring speed of 15 r/min during the microwave roasting process.The dechlorination rate reaches peak value of 88% at 700 ℃.The chlorine is removed as HCl gas when water vapor is used as activating agent,which means that it can be recovered into hydrochloride acid.

Microwave absorbing characteristics and temperature increasing behavior of basic cobalt carbonate in microwave field

The microwave absorbing characteristics of basic cobalt carbonate,cobalt oxide(Co3O4),and the mixture of basic cobalt carbonate and cobalt oxide were investigated by means of microwave cavity perturbation,their temperature increasing curves were measured,and their ability to absorb microwave energy was also assessed based on the temperature increasing behavior of the material exposed to microwave field.Analyses of spectrum attenuation and relative frequency shift show that basic cobalt carbonate has weak capability to absorb microwave energy,while cobalt oxide has very strong capability to absorb microwave energy.It is feasible to thermally decompose basic cobalt carbonate though addition of small amount of cobalt oxide in microwave fields.The capability to absorb microwave energy of sample increases with an increase in mixing ratio of Co3O4.

Arsenic removal from acidic industrial wastewater by ultrasonic activated phosphorus pentasulfide

Arsenic is one of the main harmful elements in industrial wastewater.How to remove arsenic has always been one of the research hotspots in academic circles.In the process of arsenic removal by traditional sulfuration,the use of traditional sulfurizing agent will introduce new metal cations,which will affect the recycling of acid.In this study,phosphorus pentasulfide (P_(2)S_(5)) was used as sulfurizing agent,which hydrolyzed to produce H_(3)PO_(4) and H_(2)S without introducing new metal cations.The effect of ultrasound on arsenic removal by P_(2)S_(5) was studied.Under the action of ultrasound,the utilization of P_(2)S_(5) was improved and the reaction time was shortened.The effects of S/As molar ratio and reaction time on arsenic removal rate were investigated under ultrasonic conditions.Ultrasonic enhanced heat and mass transfer so that the arsenic removal rate of 94.5%could be achieved under the conditions of S/As molar ratio of 2.1:1 and reaction time of 20 min.In the first 60 min,under the same S/As molar ratio and reaction time,the ultrasonic hydrolysis efficiency of P_(2)S_(5) was higher.This is because P_(2)S_(5) forms ([(P_(2)S_(4))])^(2+)under the ultrasonic action,and the structure is damaged,which is easier to be hydrolyzed.In addition,the precipitation after arsenic removal was characterized and analyzed by X-ray diffraction,scanning electron microscope-energy dispersive spectrometer,X-ray fluorescence spectrometer and X-ray photoelectron spectroscopy.Our research avoids the introduction of metal cations in the arsenic removal process,and shortens the reaction time.

Acid-pickling plates and strips speed control system by microwave heating based on self-adaptive fuzzy PID algorithm

Double self-adaptive fuzzy PID algorithm-based control strategy was proposed to construct quasi-cascade control system to control the speed of the acid-pickling process of titanium plates and strips. It is very useful in overcoming non-linear dynamic behavior, uncertain and time-varying parameters, un-modeled dynamics, and couples between the automatic turbulence control (ATC) and the automatic acid temperature control (AATC) with varying parameters during the operation process. The quasi-cascade control system of inner and outer loop self-adaptive fuzzy PID controller was built, which could effectively control the pickling speed of plates and strips. The simulated results and real application indicate that the plates and strips acid pickling speed control system has good performances of adaptively tracking the parameter variations and anti-disturbances, which ensures the match of acid pickling temperature and turbulence of flowing with acid pickling speed, improving the surface quality of plates and strips acid pickling, and energy efficiency.

Kinetic study on microwave-enhanced direct reduction of titanomagnetite concentrate with coal

Titanomagnetite concentrate is one of the important titanium resources.The apparent activation energy(Ea)of the direct reduction of titanomagnetite concentrate was composed of two parts(average activation energy:E_(a)=E_(a-L)+E_(a-Step1),where E_(a-L) is the lattice energy of titanomagnetite concentrate,and is the activation energy of step 1 for the reduction of titanomagnetite concentrate in the route of.Fe^(3+)→^(Step1)Fe^(2+)→^(Step2)Fe_(2)O^(2)→^(Step3)Fe^(0)).Ea(583.43 kJ/mol),(426.4 kJ/mol),and(157.0 kJ/mol)were calculated by the model-free methods based on thermogravimetry and Dmol3 module.Combined with the analysis of activation energy fluctuation and the shifting trend of related mechanism functions,the reduction kinetic system with three main characteristics,namely nucleation,diffusion and concentration fluctuation,was established.In addition,the scanning electron microscopy comparison analysis of the samples from microwave reduction and conventional reduction shows that microwave heating could realize the microstructure Ti-Fe separation and reduce the lattice energy of the titanomagnetite concentrate,thus enhancing the reduction process by 7.68%from the perspective of activation energy.

Facile Synthesis of Nanocrystal Tin Oxide Hollow Microspheres by Microwave-Assisted Spray Pyrolysis Method

Tin oxide（SnO2） hollow microspheres with narrow size distribution were prepared by a facile one-pot microwave-assisted spray pyrolysis method. The effect of temperature on microstructural and optical properties was investigated by X-ray diffraction（XRD）, scanning electron microscope（SEM）, high resolution transmission electron microscope（HRTEM）, and UV-Vis spectrophotometer（UV-Vis）, respectively.The SnO2 particles obtained at and above 700？C are tetragonal rutile structure with high purity and smooth surface morphology, which consist of well-interconnected SnO2 nanocrystallines and the shell thickness was about 26 nm. UV-Vis absorption values were quite low in visible light region and high in ultraviolet region, indicating the possible utilization for optical purpose of the as-prepared SnO2. The band gaps were 3.88 and 4.07 e V for SnO2 synthesized at 700 and 800？C, respectively. As compared to traditional electrical heating or flame modes, microwave heating introduced here demonstrates a highefficiency, environmentally benign, and time-and energy-saving technology to synthesize advanced powders.

Prediction model of microwave calcining of ammonium diuranate using incremental improved back-propagation neural network

The incremental improved Back-Propagation （BP） neural network prediction model using the Levenberg-Marquardt algorithm based on optimizing theory is put forward, which can solve the problems existing in the process of calcinations for ammonium diuranate （ADU） by microwave heating, such as long testing cycle, high testing quan- tity, difficulty of optimization for process parameters. Many training data probably were offered by the way of increment batch and the limitation of the system mem- ory could make the training data infeasible when the sample scale was large. The prediction model of the nonlinear system is built, which can effectively predict the experiment of microwave calcining of ADU, and the incremental improved BP neural network is very useful in overeoining the local minimum problem, finding the global optimal solution and accelerating the convergence speed.

Synthesis of indium tin oxide nano-polycrystalline powders by ultrasonic spray pyrolysis

Indium tin oxide(ITO) nano-polycrystalline powders were prepared by ultrasonic spray pyrolysis(USP) method using a precursor solution of indium and tin chlorides in a simple one-step process without any post-heat treatment,additives and other complex operations.The morphology and crystal structure of ITO powders were studied by thermogravimetric and differential thermal analysis(TG-DTA),X-ray diffraction(XRD),energy-dispersive spectrometer(EDS),scanning electron microscopy(SEM),laser particle size analyzer(LPSA),transmission electron microscope(TEM),high-resolution transmission electron microscopy(HRTEM) and selected area electron diffraction(SAED),respectively.The results indicate that pure cubic ITO solid solution could be obtained at and above the pyrolysis temperature of 600℃.Through adjusting the size of atomized precursor droplets,the particles with regular spherical shape and smooth surface are also obtained.The spherical particles have a narrow size distribution with a dominant diameter size in the range of 0.52-1.28 μm,and the average value is 1.01 μm.The clear lattice fringes in HRTEM image confirm a polycrystalline structure of ITO particles with the growth direction along(222) direction.

模块化局域元素供应技术批量制备12英寸过渡金属硫族化合物

二维过渡金属二硫族化合物(TMDs)因其原子级厚度、高载流子迁移率和超快电荷转移等优点而被认为是下一代半导体器件的核心材料.与传统半导体工业类似,晶圆级TMDs材料的批量生产是其集成电路发展的先决条件.然而,由于生长过程中需要严格满足多种前驱体的有效传输,TMDs晶圆的制备能力通常局限在每批次单片和小片(主要尺寸为2~4英寸).本研究开发了一种用于批量生产晶圆级TMDs的模块化生长策略,可以制造从2英寸(每批15片)到突破性的12英寸(每批3片)的TMDs晶圆.其中,每个模块包括供应TMDs晶圆生长的自充足的局域前驱体供应单元,通过将多个模块堆叠组装形成阵列可实现批量化制备.利用包括光谱学、电子显微镜和电学测量在内的多种表征技术,可以证明制得的单层薄膜具有高结晶度和大面积均匀性.此外,该模块化单元可以将制备的晶圆级MoS_(2)取代转换为多种结构,例如,Janus型MoSSe结构,MoS_(2(1-x))Se_(2x)合金以及MoS_(2)-MoSe_(2)平面异质结等,充分体现了本制备策略的可扩展性.本研究展现了高质量和高产量的晶圆批量生产能力,有望推动二维半导体从实验室规模到工业化规模的无缝过渡,实现与传统硅基技术的互补.