快速加热条件下煤和碳酸钙的混合反应动力学研究

建立了能够实时监测样品质量的高温垂直管式炉试验系统。试验过程中,煤粉的燃烧反应和CaCO 3的分解反应可以同时进行,其混合反应特性可以反映分解炉的真实情况。在900~1000℃工作温度区间内,温度变化对煤粉的燃烧反应影响很小,但温度是较低温度下CaCO 3分解的重要影响因素。随着混合物中CaCO 3质量的增加,反应速率对温度更敏感。当煤与CaCO 3质量比约为1∶9时,分解产物的BET(Brunauer,Emmett和Teller)比表面积最大。试验数据的动力学分析表明,在不同质量比下混合物的反应动力学模型不同,活化能随着煤与CaCO 3质量比的增加而降低。为了保证水泥分解炉中CaCO 3的分解率和煤的燃烧效率均较高,有必要将煤与CaCO 3质量比控制在1∶9以上。获得的活化能数据可以为预分解炉的后续模拟计算提供支持。

A simple physical mixing method for MnO2/MnO nanocomposites with superior Zn^2+storage performance

MnO2/MnO cathode material with superior Zn^2+storage performance is prepared through a simple physical mixing method.The MnO2/MnO nanocomposite with a mixed mass ratio of 12:1 exhibits the highest specific capacity(364.2 mA·h/g at 0.2C),good cycle performance(170.4 mA·h/g after 100 cycles)and excellent rate performance(205.7 mA·h/g at 2C).Analysis of cyclic voltammetry(CV)data at various scan rates shows that both diffusioncontrolled insertion behavior and surface capacitive behavior contribute to the Zn2+storage performance of MnO2/MnO cathodes.And the capacitive behavior contributes more at high discharge rates,due to the short paths of ion diffusion and the rapid transfer of electrons.

Kinetics of Copolymerization of Acrylonitrile with N-Vinylpyrrolidone in H_2O/Dimethyl Sulphoxide Mixture

Kinetics of copolymerization of acrylonitrile(AN) with N-vinylpyrrolidone(NVP) initiated by azodi-isobutyronitrile(AIBN) was investigated in H2O/dimethyl sulphoxide(DMSO) mixture between 50℃ and 70℃ under N2 atmosphere. The rate of copolymerization and particle size were measured respectively. The kinetic equation of copolymerization system is obtained as Rpat 60℃. The overall activation energy for copolymerization system was computed as 87.3kJ.mol-1. Effect of additives of hydroquinone and dioxane on copolymerization was discussed. The polymerization is retarded by hydroquinone and accelerated by dioxane, which confirms the free radical copolymerization of AN with NVP.

Mathematical Modeling of the Hydrodynamics of an EGSB Reactor

Generally, in the literature, the hydrodynamic behavior of an EGSB （expanded granular sludge bed） reactor is considered as a complete mix reactor. Few works study in detail the flow of such reactors. The aim of this work was to study, in detail, the hydrodynamics of an EGSB reactor and to propose a mathematical model to describe its flow. A 3.04 L reactor was used with HRT （hydraulic retention time） of 12 h, affluent flowrate of 4 mL·min^-1, and the recirculation flow rate was changed to study three different upflow velocities in the tube （6, 8 and 10 m·h^-1. The pulse input method was used, with the use of blue dextran as tracer. In order to consider the dimensional differences between the tube and the separator, the reactor was divided into two regions （tube and separator）. Initially, a model with two tubular reactors with dispersion in series was proposed and the Peclet number was adjusted for the two regions. It was observed that the region of the tube shows the behavior of a tubular reactor with high dispersion, whereas the region of the separator shows the behavior of a complete mix reactor. In order to simplify the equation, and by knowing that the concentration profile along the reactor was almost constant, a model of two CSTRs （continuous stirred tank reactors） was proposed in series and the number of reactors （N） was set. The best combination was five CSTRs, three in the tube region and two in the separator region. The presented models were equivalent and can be used to describe the hydrodynamic behavior of the EGSB reactor.

Thermal Analysis of Composite Cements

The hydration of cement compounds gives hydrated compounds, which allow linking together, the different particles and aggregate of cement, and gives the concrete the required qualities. The dynamics of hydration reactions will depend on many factors, such as the fineness of cement, the ratio w/c during hydration, temperature, mixing technique, and the presence of additives in blended cement, as pozzolan, tuff and slag from blast furnaces. We studied the thermal and kinetic reactions of Portland cement hydration, and its variants with different additions using a differential scanning calorimetric analysis. The parameters from these models of curves allow us to evaluate the enthalpies, and the degree of progression of this blended cement, and finally determine their activation energies. We can say that the hydration of Portland cement is due to a series of reactions as （ C3S,C2S,C3A and C4AF reactions with water） and each of them, has its own kinetic, the experimental measurement of the heat of hydration, allows us to represent the overall kinetics of these reactions values of activation energy, they are therefore apparent and global energy. In our experiments, significant differences in these physicochemical parameters were observed, depending on the additive used.

Study on the kinetic model of Cr/H/Air/Cl mixture

Constructing a reasonable reaction kinetic model for Cr-containing waste incineration is of high significance to study the effect of various factors,such as temperature,Cl,on its hexavalent chromium compounds.In this paper,a primary Cr/H/Air/Cl reaction kinetic model is built and studied by Gaussian 03 code with quantum chemistry theory.Numerical results show that there are two overall reactions in the model,each of the two overall reactions consists of their respective two elementary reactions.So the two overall reactions should be omitted from the model.Instead,the four elementary reactions should be added in the Cr/H/Air/Cl reaction kinetic model.The activation energies of the four elementary reactions are also calculated.