Modeling of mass transfer and thermal cracking during the coking of Athabasca residues

The kinetics of thermal cracking of films of vacuum residue from Athabasca bitumen in the temperature range of was modelled with liquid-phase mass transfer, reaction-dependent fluid properties, and coke formation by reaction of cracked products in the liquid phase. Previous investigations on the thermal cracking of vacuum residue in thin films showed that at low film thickness the coke yield was insensitive to the temperature and heating rate for thin films of bitumen. The coke yield increased with the thickness of the initial film, in the range from 20 to . At the same time, the viscosity of the reacting liquid increased rapidly with time, which would slow down the diffusion of products inside the film. This coupling of transport and reaction would enhance the formation of coke by increasing the rate of recombination reactions. The concept of intrinsic coke is used in a new kinetic model to account for the minimum observed coke formation in thin films. With increasing film thickness, the increasing yield of extrinsic coke is modelled through the change in fluid properties as a function of extent of reaction, which reduces the rate of diffusion in the reacting liquid phase. The model was able to properly account for the insensitivity of coke yield in thin films to reaction temperature and the dependence of coke yield on the thickness of the liquid film.     

Effect of Fused MgO-ZrO_2 Clinker Addition on Thermal Shock Resistance of MgO-ZrO_2 Unfired Bricks

MgO-ZrO2 unfired bricks with ZrO2 content up to 8% at the interval of 2% were prepared,using fused magnesia(MgO:97%)and fused MgO-ZrO2 clinker(ZrO2:14.33%)as starting materials and phenolic resin as binder.The effects of ZrO2 content on thermal shock resistance(TSR)and other properties such as cold and hot modulus of rupture have been investigated.Residual cold modulus of rupture ratio after heating at 1 000 ℃ and quenching by air blowing was adopted to characterize TSR.Addition of the MgO-ZrO2 clinker impr...     

Mullitization of Andalusite and Influence of Aggregates on Properties of Aluminosilicate Refractories Based on Andalusite Matrix

The mullitization of andalusite from Xinjiang,China and influence of aggregates on properties of aluminosilicate refractories were studied by XRD,SEM,EDS,DSC.It was found that mullitization was obvious at 1 400 ℃,but considerable at 1 500 ℃.The refractories with corundum aggregates had the highest RUL and the lowest creep rate,but refractories with bauxite aggregates had the lowest RUL and the highest creep rate.     

数控插齿机热误差模块化稳健性预测模型建立

针对数控插齿机固有的主轴进给系统结构带来的传动间隙引起波动性热变形建模预测精度不高的问题,提出一种基于均值平滑处理波动的模块化建模方法。利用模糊聚类结合灰色关联度方法和多元线性回归对该机床主轴x、y向分别建立热误差补偿模型,并计算预测残余值在不同分布范围的概率。结果表明：与传统热误差建模方法相比,模块化预测残余值在不同范围的分布较均匀,稳健性得到了有效提升,为热误差模块化建模方法提供了参考。     

炭材料热分析技术概述

论述了TG,DTA,DTG,DSC和DMTA等热分析技术在炭及其复合材料上的应用。TG-DTG技术可以追踪升温过程的质量变化,直接体现着材料的高温抗氧化性能、热稳定性,并可确定材料的燃点等;热效应曲线则反映出材料升温分解过程中的放热或吸热效应,是和材料组成及结构变化密切相关的,二者结合,从结构本质上探析了炭材料的物理化学反应机制。因此,TG-DTG,DTA,DSC技术被广泛应用于炭材料的反应机理、催化剂的催化机制、高温抗氧化性、耐热性、活性炭的表面性能、燃烧特性等的探究;DMTA技术是研究高聚物结构-分子运动-性能的一种有效手段,被用于测定炭材料界面性能。     

Yb2O3 and Gd2O3 doped strontium zirconate for thermal barrier coatings

Yb₂O₃ (10 mol%) and Gd₂O₃ (20 mol%) doped SrZrO₃ was investigated as a material for thermal barrier coating (TBC) applications. The thermal expansion coefficients (TECs) of sintered bulk Sr(Zr_0.9Yb_0.1)O_2.95 and Sr(Zr_0.8Gd_0.2)O_2.9 were recorded by a high-temperature dilatometer and revealed a positive influence on phase transformations of SrZrO₃ by doping Yb₂O₃ or Gd₂O₃. The results for the thermal conductivities of Sr(Zr_0.9Yb_0.1)O_2.95 and Sr(Zr_0.8Gd_0.2)O_2.9 indicated that both dopants can reduce the thermal conductivity of SrZrO₃. Mechanical properties (Young's modulus, hardness, and fracture toughness) of dense Sr(Zr_0.9Yb_0.1)O_2.95 and Sr(Zr_0.8Gd_0.2)O_2.9 showed lower Young's modulus, hardness and comparable fracture toughness with respect to YSZ. The cycling lifetimes of Sr(Zr_0.9Yb_0.1)O_2.95/YSZ and Sr(Zr_0.8Gd_0.2)O_2.9/YSZ double layer coatings (DLC), which were prepared by plasma spraying, were comparable to that of YSZ at operating temperatures <1300 °C. However, the cycling lifetime of Sr(Zr_0.9Yb_0.1)O_2.95/YSZ DLC was 25% longer, whereas Sr(Zr_0.8Gd_0.2)O_2.9/YSZ DLC had a shorter lifetime compared to the optimized YSZ coating at operating temperatures >1300 °C.     

超高浓度(VHG)乙醇发酵研究进展

简要介绍了超高浓度乙醇发酵的特点及面临的困难,对VHG乙醇发酵国内外研究进展进行了综述,同时对该领域发展的前景进行了分析和展望。     

管式环流反应器在乙酸/乙酐羰基合成中的应用

介绍了以乙酸甲酯和甲醇为原料合成年产20 kt乙酐和20 kt乙酸的过程,并且介绍了在以LiI为促进剂的铑-碘均相催化剂作用下、170~199℃的温度范围及5.0 MPa压力条件下,管式环流反应器在乙酸/乙酐合成中的应用。分析了反应器内流体的流动特点和羰基合成的反应过程,建立了数学模型。计算得到了反应器内反应物料转化率、各组分浓度、温度和冷却水温度等各种参数沿物料流动方向的分布,同时对反应器进行了热稳定性分析。计算结果表明,当系统在操作过程中转化率偏离定常态0.000 1,温度偏离定常态0.000 1℃时,转化率和温度能分别在4×10-6s和8×10-6s内回到定常态,整个反应体系是稳定的。     

超重力精馏的应用与发展

分离工程是化工过程工业的重要支柱,而精馏技术是最为重要的分离工程之一,超重力精馏技术作为一种新兴的相对传统精馏技术有巨大优势的新技术,越来越多地收到科研工作者的关注。本文较系统地总结了国内外自20世纪70年代以来在超重力精馏设备和技术上的研究进展,并对超重力精馏的研究和发展前景进行了展望。     

十八烷/PSt相变微胶囊的制备及其热性能研究

细乳液法制备了十八烷/聚苯乙烯(PSt)相变微胶囊,用TEM、DLS和DSC等对微胶囊进行了表征。研究了十二烷基硫酸钠(SDS)的加入量、亲水性单体丙烯酸的加入量、引发剂类型以及苯乙烯与十八烷的加料比对产物形态的影响。研究表明:低的SDS浓度有利于微胶囊结构的形成,产物粒子的平均粒径随SDS加入量的增大而减小;加入亲水性共聚单体丙烯酸可以改善微胶囊的形态,但产物中PSt均相微球增多;使用油溶性引发剂AIBN比使用KPS更加有利于微胶囊的形成;苯乙烯与十八烷的投料比为1∶1时,制备的微胶囊相变焓为111.6 J/g。