APPLICATION OF THE SHRINKING CORE MODEL TO THE KINETICS OF ZINC OXIDE DESULFURIZATION

The kinetics of H2S removal by zinc oxide desulfurizer was studied through thermogravimetricanalysis.The experimental results show that desulfurization rate was controlled,at high temperatureand low conversion,by the chemical reaction rate,and at low temperature and high conversion by thegrain diffusion rate.The reaction is first order with respect to H2S concentration in the differentcontrolled stages.The kinetic behavior can be modeled through the employment of the shrinking coremodel.The values of the model parameters were determined.The variation tendencies with temperatureand concentration of H2S at the controlled stages were discussed.

Shell and shrinking core kinetics model of Mg-based hydrogen storage alloys

The kinetics equation of the Mg-based hydrogen storage alloys (Mg-Ni-MO) was established by the shell and shrinking core model. The total coefficients of the kinetics equation of the hydrogen absorption and desorption process with shell diffusion as the controlling step were determined by semi-empirical and semi-theoretical methods, and the apparent activation energy of the hydrogen absorption process was obtained. The calculation results can well accord with the experimental data, and can well forecast the hydrogen storage capacity and absorption rate at different times. By using the kinetics equation, the effects of temperature and pressure on the hydrogen storage process can also be well understood. The kinetics equation is helpful for the design of the hydrogen storage container.

Improved Differential Evolution with Shrinking Space Technique for Constrained Optimization

Most of the current evolutionary algorithms for constrained optimization algorithm are low computational efficiency. In order to improve efficiency, an improved differential evolution with shrinking space technique and adaptive trade-off model, named ATMDE, is proposed to solve constrained optimization problems. The proposed ATMDE algorithm employs an improved differential evolution as the search optimizer to generate new offspring individuals into evolutionary population. For the con- straints, the adaptive trade-off model as one of the most important constraint-handling techniques is employed to select better individuals to retain into the next population, which could effectively handle multiple constraints. Then the shrinking space technique is designed to shrink the search region according to feedback information in order to improve computational efficiency without losing accuracy. The improved DE algorithm introduces three different mutant strategies to generate different offspring into evo- lutionary population. Moreover, a new mutant strategy called ＂DE/rand/best/l＂ is constructed to generate new individuals according to the feasibility proportion ofcurrent population. Finally, the effectiveness of the pro- posed method is verified by a suite of benchmark functions and practical engineering problems. This research presents a constrained evolutionary algorithm with high efficiency and accuracy for constrained optimization problems.

Huadong sintering model about expansion and shrinkage

The whole sintering course from the beginning of heating to the end of heat preservation stage was studied by taking into account the influence of pressing. It was found that there exist expanding mechanism and shrinking mechanism in the sintering process, and the expanding mechanism is always acting before the shrinking mechanism. Whether the sintering body shrinks or expands depends on the interaction between the two mechanisms. And according to this, the Huadong sintering model in account of expansion and shrinkage mechanism was given. [

Kinetic model for calcium sulfate decomposition at high temperature

A modified shrinking unreacted-core model,based on thermogravimetric analysis,was developed to investigate CaSO4 decomposition in oxy-fuel combustion,especially under isothermal condition which is difficult to achieve in actual experiments due to high-temperature corrosion.A method was proposed to calculate the reaction rate constant for CaSO4 decomposition.Meanwhile,the diffusion of SO2 and O2,and the sintering of CaO were fully considered during the development of model.The results indicate that the model can precisely predict the decomposition of CaSO4 under high SO2 concentration（1100×10-6）.Concentrations of SO2 and O2 on the unreacted-core surface were found to increase first and then decrease with increasing temperature,and the average specific surface area and porosity of each CaO sintering layer decreased with increasing time.The increase of SO2 and/or O2 concentration inhibited CaSO4 decomposition.Moreover,the kinetics of CaSO4 decomposition had obvious dependence on temperature and the decomposition rate can be dramatically accelerated with increasing temperature.

乙二胺盐酸盐与氢氧化钙反应动力学

在双氨基硅烷偶联剂的工业生产过程中会产生大量的乙二胺盐酸盐副产物,该副产物通过与氢氧化钙进行中和反应得到无水乙二胺,可实现乙二胺的循环利用。利用电导率法建立乙二胺盐酸盐转化率和电导率的关系,考察了液固比、盐浓度、温度等因素对乙二胺盐酸盐转化率的影响,并确定了最优工艺条件。实验结果表明,乙二胺盐酸盐的转化率随着液固比及乙二胺盐酸盐浓度的增大而降低。基于缩芯模型,建立乙二胺盐酸盐和氢氧化钙的动力学方程。根据实验数据求出反应过程的活化能,发现乙二胺盐酸盐和氢氧化钙的中和反应主要受内部扩散控制。动力学模型为Kt=1-3(1-x)^(2/3)+2(1-x),活化能为30.89 kJ/mol。该研究为从乙二胺盐酸盐副产物提取无水乙二胺提供了实验依据。

基于收缩移动块的固定翼与飞行平台交会轨迹滚动时域规划

针对一类固定翼与飞行平台组合系统的交会轨迹规划问题,提出一种基于收缩移动块的滚动时域规划算法。首先,建立固定翼无人机与飞行平台的交会动态模型,再将交会轨迹规划问题转化为一类以累加型能耗性能指标、固定终端时域、终端状态的收缩时域滚动优化问题。其次,引入收缩移动块策略压缩轨迹规划问题的决策变量数,从而保证算法的实时性。在此基础上,建立算法的递推可行性和可转移性结果。最后,仿真比较结果验证了本文算法在交会过程节能、准时和实时计算等方面的优势。

Mass transfer process of peanut protein extracted by bis(2-ethylhexyl)sodium sulfosuccinate reverse micelles

The liquid-liquid extraction method using reverse micelles can simultaneously extract lipid and protein of oilseeds,which have become increasingly popular in recent years.However,there are few studies on mass transfer processes and models,which are helpful to better control the extraction process of oils and proteins.In this paper,mass transfer process of peanut protein extracted by bis(2-ethylhexyl)sodium sulfosuccinate(AOT)/isooctane reverse micelles was investigated.The effects of stirring speed(0,70,140,and 210 r/min),temperature of extraction(30,35,40,45,and 50℃),peanut flour particle size(0.355,0.450,0.600,and 0.900 mm)and solidliquid ratio(0.010,0.0125,0.015,0.0175,and 0.020 g/mL)on extraction rate were examined.The results showed that extraction rate increased with temperature rising,particle size reduction as well as solid-liquid ratio increase respectively,while little effect of stirring speed(P>0.05)was observed.The apparent activation energy of extraction process was calculated as 10.02 kJ/mol and Arrhenius constant(A)was 1.91 by Arrhenius equation.There was a linear relationship between reaction rate constant and the square of the inverse of initial particle radius(1/r_(0)^(2))(P<0.05).This phenomenon and this shrinking core model were anastomosed.In brief,the extraction process was controlled by the diffusion of protein from the virgin zone interface of particle through the reacted zone and it was in line with the first order reaction.Mass transfer kinetics of peanut protein extracted by reverse micelles was established and it was verified by experimental results.The results provide an important theoretical guidance for industrial production of peanut protein separation and purification.

Kinetics of zinc sulfide concentrate direct leaching in pilot plant scale and development of semi-empirical model

The direct leaching kinetics of an iron-poor zinc sulfide concentrate in the tubular reactor was examined.All tests werecarried out in the pilot plant.To allow the execution of hydrostatic pressure condition,the slurry with ferrous sulfate and sulfuric acidsolution was filled into a vertical tube(9m in height)and air was blown from the bottom of the reactor.The effects of initial acidconcentration,temperature,particle size,initial zinc sulfate concentration,pulp density and the concentration of Fe on the leachingkinetics were investigated.Results of the kinetic analysis indicate that direct leaching of zinc sulfide concentrate follows shrinkingcore model(SCM).This process was controlled by a chemical reaction with the apparent activation energy of49.7kJ/mol.Furthermore,a semi-empirical equation is obtained,showing that the order of the iron,sulfuric acid and zinc sulfate concentrationsand particle radius are0.982,0.189,-0.097and-0.992,respectively.Analysis of the unreacted and reacted sulfide particles bySEM-EDS shows that insensitive agitation in the reactor causes detachment of the sulfur layer from the particles surface in lowerthan60%Zn conversion and lixiviant in the face with sphalerite particles.

Optimization of process parameters and kinetic modelling for leaching of copper from oxidized copper ore in nitric acid solutions

The leaching behavior of Tunceli malachite mineral was investigated in nitric acid solutions by two steps to evaluate the effect of various experimental parameters.In the first step,the optimal conditions for the leaching process were determined,while in the second step,a kinetic evaluation for the process was performed.In the optimization experiments,the concentration of nitric acid,temperature,stirring speed,and solid-to-liquid ratio were selected as the independent variables,and the central composite design method(CCD)was applied to the experimental data.At the end of the experiments,the optimal values for the concentration of nitric acid,temperature,solid-to-liquid ratio and stirring speed were determined to be 0.5 mol/L,50℃,0.004 g/m L and 500 r/min,respectively.Under the optimal conditions,the leaching rate was found to be 99%for 120 min of reaction time.In the kinetic evaluation tests,the effects of the concentration of nitric acid,temperature,stirring speed,solid-to-liquid ratio and particle size on the leaching rate of copper from malachite were investigated.In these tests,it was determined that the leaching rate increased with the increase in the temperature,acid concentration and stirring speed,and with the decrease in the particle size and solid-to-liquid ratio.In consequence of the kinetic analysis,it was observed that the leaching kinetics followed the mixed kinetic model,and a mathematical model for the leaching process was introduced.The activation energy for this process was calculated to be 36.23 k J/mol.

Model for Reduction of Iron Oxide Pellet with a C-O-H-N Gas Mixture Considering Water Gas Shift Equilibrium in the Gas While It Diffuses through the Product Layer

In metallurgical processes, more and more usage of hydrocarbons is encouraged to bring down the carbon emissions. In this regard, numerous investigations on reduction of oxides by C-O-H-N gas mixture have been reported. Attempts to simulate these reduction processes using shrinking core model, one of the common models used for such studies, have under predicted the reduction rates. This may be owing to the fact that the homogeneous reaction in the gas phase is not being considered. If the reaction temperatures are above 1,000 K, generally so for many reduction processes, the homogeneous gas reaction rates are expected to be high enough that local equilibrium in the gas phase can be assumed. In the present study, reduction of wustite in a C-O-H-N gas mixture has been modeled using shrinking core model considering the water gas shift equilibrium in the gas while it diffuses through the product layer.

大流动性高强轻集料混凝土早期收缩特性研究

【目的】探索大流动性高强轻集料混凝土(high workability and high strength lightweight aggregate concrete,HHLC)的收缩特性,以期为HHLC推广应用提供参考依据。【方法】采用高强页岩陶粒制备HHLC,通过室内试验测量其自生收缩应变及总收缩应变。【结果】HHLC的28 d自生收缩应变仅为57×10^(-6),总收缩应变为203×10^(-6),与相同强度等级的自密实混凝土(self-compacting concrete,SCC)及普通混凝土(normal concrete,NC)相比,HHLC的早期自生收缩应变及总收缩应变最小;HHLC收缩变形的发展规律与SCC、NC收缩变形的基本一致,但HHLC在前3 d出现微膨胀现象,膨胀值约为10×10^(-6);在HHLC的总收缩应变中,自生收缩应变占比较小,收缩应变主要表现为外干燥引起的干燥收缩应变,且水胶比越小,干燥收缩应变越大;粉煤灰对降低HHLC的早期收缩效果明显,但粉煤灰的掺量不宜超过25%;用混凝土收缩计算模型MC90计算NC的变形,适用性较好,但用来计算SCC、HHLC的变形,误差较大。考虑掺合料及骨料对HHLC收缩特性的影响,对现行规范中的MC90模型进行修正。【结论】采用低吸水率的高强页岩陶粒制备的HHLC具有良好的工作性能及体积稳定性,在结构工程中应用前景广阔;修正后的MC90模型对HHLC具有较好的适用性。

气固相非催化反应——粒径不变缩芯模型的实例解析

以钙基吸收剂吸收CO_(2)为例,讲解了化学反应工程中缩芯模型的相关理论知识,包括反应过程、浓度分布和速率方程等内容。通过查阅文献、梳理理论知识点、实验等方式,进行结果验证和知识的扩展。

利用电石渣进行赤泥脱碱研究

赤泥是制铝工业提取氧化铝时排出的工业固体废弃物,高碱含量限制了其利用。利用电石渣替代天然钙基材料进行赤泥脱碱,分析脱碱温度、电石渣掺量、液固比、反应时间四个因素对脱碱效果的影响,探究电石渣进行赤泥脱碱的反应机理。结果表明,随着温度升高、电石渣掺量增加、反应时间增加,赤泥脱碱效率升高;在温度为90℃、液固比为4∶1、反应时间为360 min、赤泥与电石渣的质量比为1∶1的反应条件下,脱碱效率达到81%,脱碱后赤泥中的Na2O含量不大于1%(质量分数),满足水泥原料的要求。电石渣进行赤泥脱碱反应符合内扩散未反应收缩核模型,提高反应温度与反应物的质量均可提高脱碱率。

氯化铁对磷酸铁锂中锂浸出性能研究

随着新能源电动汽车的发展,磷酸铁锂(LiFePO_(4),LFP)电池的报废量逐年剧增,由于其有价金属锂含量低,回收经济性差,近年来废旧LFP的低成本回收成为研究热点。基于同构诱导置换浸出,以FeCl_(3)为浸出剂,在固-液反应体系中探究了FeCl_(3)对LFP中的锂浸出的影响因素,利用未反应核收缩模型探究了两个浸出阶段的宏观动力学。结果表明,增大FeCl_(3)/LFP摩尔比、减小固液比和升高反应温度可以显著促进锂的浸出;在浸出前4 min内,锂浸出速率主要受固态产物层内扩散过程控制,表观活化能为6.68 kJ/mol;4 min后锂浸出速率受流体膜外扩散、产物层内扩散和化学反应混合机制的控制。

高速永磁电机转子过盈方式对转子应力的影响

该文对高速永磁电机(HSPMM)转子过盈方式对转子应力的影响进行研究。首先,在二维极坐标下建立了转子各部位统一几何模型的应力场数学模型,可求解不同边界条件下转轴、永磁体和护套的径向应力和周向应力。然后,基于建立的应力场数学模型得到不同过盈方式下转子应力的解析计算方法,分析了不同过盈方式对转子应力的影响。在此基础上,提出“虚拟过盈”概念及虚拟过盈下的应力计算表达式,分析了其准确度并解释了其物理意义。最后,通过有限元(FEM)分析方法对一台额定功率为50 kW、额定转速为40000 r/min的高速永磁电机进行分析,说明了不同的过盈方式导致转子应力的差异,验证了理论分析的合理性。

新疆地区不同岩性煤矸石重金属元素释放规律研究

为了解新疆地区不同岩性煤矸石重金属元素释放规律和防范重金属元素产生的环境风险,采用皮里青矿区和五彩湾矿区未风化煤矸石,通过X射线衍射、X射线荧光光谱、电感耦合等离子体质谱仪测试手段研究煤矸石淋滤过程中V、Cr、Ni、Cu、Zn、Ba、Pb、Th、U重金属元素的释放规律。结果表明:(1)煤矸石的矿物组成以高岭石和石英为主,黏土岩矸石矿物组成较为复杂,黏土矿物含量高;(2)新疆砂岩和黏土岩矸石重金属元素Ni、Cu、Zn、Ba含量较高,砂岩矸石Ba元素含量为291.00μg/g,黏土岩矸石中Ba含量最高为416.05μg/g,煤矸石样品中元素含量高淋滤后元素释放量大;(3)煤矸石重金属元素均在淋滤前期、中期释放较多,黏土矿物吸附作用是淋滤后期黏土岩矸石元素释放浓度降低的重要原因;(4)“缩核模型”显示不同岩性煤矸石重金属元素释放是多因素耦合作用的结果。元素淋滤结果环境效应评价表明,黏土岩矸石相比砂岩矸石潜在危害性更大,长时间、多期次的淋滤造成重金属元素累积效应值得关注。

典型碱性吸附剂炉内脱除燃煤烟气SO_(3)特性试验

由于会引起蓝烟、酸沉积以及建筑腐蚀等问题,SO_(3)减排已成为当前燃煤污染物控制的热点问题。基于U型石英管在260~380℃对常见碱性吸附剂的SO_(3)脱除规律进行试验研究。试验结果表明,Mg(OH)_(2)比表面积与孔容均最大,在试验温度范围内SO_(3)脱除性能优于NaHCO_(3)、Ca(OH)_(2)和Na_(2)CO_(3)。SO_(3)脱除前期,温度升高会提高所用吸附剂的SO_(3)动态脱除效率,且Mg(OH)_(2)在380℃下第10 min时的脱除率高达84%;当SO_(3)脱除趋于饱和时,温度提高对所用吸附剂的SO_(3)动态脱除效率无明显影响。吸附动力学分析表明,Na_(2)CO_(3)对SO_(3)的吸附反应前期(0~40 min)基本符合反应控制的缩核模型,此时Na_(2)CO_(3)表面的化学反应主导SO_(3)的脱除反应,而内扩散控制的缩核模型仅在260℃时可较好的描述前40 min的脱除反应。而在吸附后期(50~100 min),表面反应控制和内扩散控制均可较好的描述该阶段的吸附过程,此时SO_(3)在产物层的内扩散与其在Na_(2)CO_(3)表面的化学反应共同主导SO_(3)的脱除反应。

鼓泡流化床内高钛渣氯化过程模拟

本研究建立了高钛渣氯化反应的未反应缩核动力学模型(SCM),并在小型鼓泡流化床中获得了动力学参数。将SCM与双流体模型(TFM)耦合建立了TFM-SCM模型,模拟研究了鼓泡流化床中的高钛渣氯化反应过程,模型预测与实验结果吻合较好。模拟结果显示:反应器出口的TiO_(2)转化率随氯气浓度和反应温度的升高而增加;反应温度是影响氯化反应的关键因素,当反应温度为1223K时,TiO_(2)的转化率可达98%;当氯化反应速率较小时,气泡是影响氯化反应的另一个重要因素。提高反应温度能明显提高流化床中乳相的反应速率,但对气泡相的氯化反应速率影响较小。氯化反应速率在床层中心区域较低,在近壁区域较大。