光散射法和筛分法测量煤粉粒度对比与转化研究

煤粉粒度对电厂锅炉运行排放有重要的影响。筛分法和激光粒度仪是工业生产实践中广泛使用的两种粒度测试技术,但由于测量原理的不同,两者测量结果也有差异。对取自电厂一次风管的24个煤粉样品进行了对比测试,结果表明,激光粒度仪结果相比于筛分法明显偏小,平均绝对偏差在5%以上,粒度分布曲线表明,激光粒度仪对20μm以下的煤粉颗粒占比会出现明显高估;对两种方法测量的粒度分布的相关性进行了分析,结果表明在25至96μm粒径范围内两者具有较强的线性相关性;基于相关性特征,建立了基于经验公式的粒度结果转化矩阵,激光粒度仪结果转化校正后,R_(75)、R_(90)和R_(200)参数平均绝对偏差分别由5.72%、3.50%、0.39%减小至3.19%,2.25%和0.30%,且校正后粒度分布曲线与筛分法吻合度增加。

支持飞机设计过程的制造质量知识模型研究

为了避免飞机设计与制造相脱节,提高飞机设计的质量,论文探讨了制造质量知识对飞机设计过程的支持。研究了制造质量知识产生的过程,及其对设计阶段支持的原理,在此基础上,提出了制造质量知识粒度转化模型。根据飞机设计各个阶段的任务,分析了对制造质量知识的需求,建立了支持飞机设计过程的制造质量知识IDEF0模型。

Parameters affecting reaction rate and conversion of TiO_2 chlorination in a fluidized bed reactor: Experimental and modeling approach

Pilot scale chlorination of TiO2 was carried out with CO as reducing agent.The experimental analysis and modeling of chlorination process of TiO2 in the presence of CO and Cl2 in a semi-continuous fluidized bed reactor were aimed.Chlorination process was continuously monitored by measuring the amount of produced TiCl4 with time.The effects of different operating parameters including chlorination temperature,feedstock particle size and size distribution,amount of feedstock and Cl2 and CO flow rates on the conversion were systematically investigated.A gradual increase in chlorination temperature led to monotonous increase of conversion rate.Conversion decreased with increased particle size of feedstock.An increase in loaded feedstock led to a decrease in reaction conversion.A model was proposed to predict conversion,particle size distribution and mole fraction of components in gas phase as reaction proceeds.A good agreement between conversions predicted by the model and experimental data under various operating conditions was observed.

Shape memory TiNi powders produced by plasma rotating electrode process for additive manufacturing

This study aimed to produce spherical TiNi powders suitable for additive manufacturing by plasma rotating electrode process(PREP).Scanning electron microscopy,X-ray diffractometry and differential scanning calorimetry were used to investigate the surface and inner micro-morphology,phase constituent and martensitic transformation temperature of the surface and inner of the atomized TiNi powders with different particle sizes.The results show that the powder surface becomes smoother and the grain becomes finer gradually with decreasing particle size.All the powders exhibit a main B2-TiNi phase,while large powders with the particle size≥178μm contain additional minor Ti2Ni and Ni3Ti secondary phases.These secondary phases are a result of the eutectoid decomposition during cooling.Particles with different particle sizes have experienced different cooling rates during atomization.Various cooling rates cause different martensitic transformation temperatures and routes of the TiNi powders;in particular,the transformation temperature decreases with decreasing particle size.

Residue Upgrading in Slurry Phase over Ultra-fine NiMo/γ-Al_2O_3 Catalyst

In this article, residual oil hydroconversion was studied in slurry phase in the presence of fine solid Ni Mo/γ-Al2O3 catalyst and the effects of operating conditions were carefully studied. The results showed that residue conversion was only affected by the reaction temperature and reaction time. The coke yield increased with a higher reaction temperature, a bigger catalyst particle size, a longer reaction time, a lower initial hydrogen pressure and a lower catalyst concentration. Heteroatoms removal rate increased with a higher reaction temperature, a longer reaction time, a higher initial hydrogen pressure, a higher catalyst concentration, and a smaller catalyst particle size. The role of catalyst in the slurry bed technology was discussed and its function could be stated as follows: the metal was applied to activate the hydrogen atoms for removing heteroatoms and saturating aromatics, while the support of the catalyst was used to prevent the mesophase coalescence for reducing coke formation.

Glass Formation of n-Butanol： Coarse-grained Molecular Dynamics Simulations Using Gay-Berne Potential Model

Using coarse-grained molecular dynamics simulations based on Gay-Berne potential model, we have simulated the cooling process of liquid n-butanol. A new set of GB parameters are obtained by fitting the results of density functional theory calculations. The simulations are carried out in the range of 290-50 K with temperature decrements of 10 K. The cooling characteristics are determined on the basis of the variations of the density, the potential energy and orientational order parameter with temperature, whose slopes all show discontinuity. Both the radial distribution function curves and the second-rank orientational correlation function curves exhibit splitting in the second peak. Using the discontinuous change of these thermodynamic and structure properties, we obtain the glass transition at an estimate of temperature Tg=1204.10 K, which is in good agreement with experimental results 1104-1 K.

Probing particle removal in brush scrubber cleaning with fluorescence technique

Brush scrubber cleaning is widely used for post chemical mechanical polishing(CMP)cleaning in semiconductor manufacturing.In this study,an experimental system based on fluorescence technique and particle-tracking velocimetry(PTV)technique was employed to characterize the particle removal displacement and velocity in the interface between a transparent copper film and a porous polyvinyl alcohol(PVA)brush during the cleaning process.Several different cleaning conditions including rotation speeds,loading pressure and cleaning agent were examined and the particle removal rate was compared.Elastic and friction removal,hydrodynamic removal and mixed-type removal are the three types of particle removal.Particles with an arc trace and uniform velocity curves were removed by friction and elastic force which were related to the brush load.Particles with a random trace and fluctuant velocity curves were removed by hydrodynamic force which was determined by the brush rotation speed.The increase of particle removal rate(PRR)with brush rotation speed is a logistic function.It is easier to improve PRR by increasing the brush load or by adding surfactant than by increasing the brush rotation speed.