常用气力输送系统的优化设计(一)

随着气力输送在水泥厂和散装水泥等领域广泛应用，迫切需要改进气力输送设计方法，以降低其能耗和提高系统的可靠性。通过分析讨论各类常用气力输送系统的性能特点和适用范围，较系统地叙述了气力输送优化设计的七个步骤。同时还介绍了可靠性设计和气力输送计算机辅助设计软件两项新技术。     

两种三聚氰胺成品正压气力输送系统的比较

三聚氰胺成品输送系统有正压气力输送和负压气力输送两种不同的输送方法,着重对两种正压气力输送系统进行了分析和比较,以供广大同行参考。     

负压与低压压送气力输送系统的能耗分析

在相同的输送参数(管道结构、输送能力、压力降及料气比)下,计算出负压气力输送系统和低压压送气力输送系统的技术数据,并详细分析了负压气力输送系统能耗高的主要原因.认为采用低压压送气力输送系统比负压气力输送系统经济效果好,输送效率较高,输送起始速度远低于负压输送系统的起始速度,并可节约能源49%,因此,选用低压压送气力输送系统比负压气力输送系统更节约能耗及降低运行费用.     

塑料行业中的气力输送计算及应用

本文介绍了气力输送在塑料行业中的应用，给出了气力输送的理论分析，经验数据和应用实例，适用于气力输送设计和验证。     

PVDF密相气力输送和稀相气力输送比较

随着气力输送在石化、医药、锂电、环保等行业的广泛应用,对密相气力输送和稀相气力输送的研究尤为重要。通过对聚偏氟乙烯(PVDF)稀相气力输送和密相气力输送的介绍,以及对二者输送气源品质、输送设备旋转阀和发送罐、输送气速和管径、除尘面积、设备平稳运行时间、输送气量和能耗等方面的对比,指出了PVDF密相输送工艺的优势。     

水平管气力输送流型特性及其影响因素的研究进展

水平管气力输送是能源化工领域的核心技术之一,水平管气力输送流型特性的研究是设计气力输送装置的重要基础.首先对水平管粉体单颗粒运动特性及其影响因素的研究进展进行了述评,介绍了电容层析成像技术(ECT)在水平管气力输送流型特性研究方面的进展,分析了拾起速度、系统背压、粉体物性和发送罐形式等对水平管气力输送流型特性的影响,在此基础上对水平管气力输送装置设计与优化提出了建议.     

脉冲气力输送在锦纶6切片输送中的应用

本文介绍了浙江大学材料技术工程公司的脉冲气力输送系统的工作原理和主要设计参数.报道了国内首次将脉冲气力输送应用于氮气输送锦纶6切片和氮气回收系统的情况,并将浙江大学材料技术公司的脉冲气力输送系统与引进的锦纶6切片生产装置中的切片气力输送系统进行了对比.     

粉粒状物料性能与其气力输送特性(续完)

4 散料气力输送特性的分类和预测。虽然气力输送在工业中已广泛应用了数十年,尤其在应用密相气力输送技术后有了更长足的发展。但是,人们迄今不得不主要依靠对某种散料在全尺度实验台上进行气力输送试验,来判定该散料是否可以密相输送和何种流动模式。     

浅谈气力输送技术在有色冶炼中的应用

气力输送技术具有高效、节能、环保等优点,被广泛用于化工、饲料输送、钢铁、冶金等行业中的粉尘、颗粒物料的输送。本文阐述了气力输送技术的工作原理;输送方式的分类:即负压吸送式气力输送和正压压送式气力输送;输送方式的选择需要根据实际工艺要求、输送能力、物料性质、输送距离等参数来确定。重点对气力输送技术在冶金行业中的应用进行了评述,气力输送技术较早应用于锌精矿输送,通过技术改进后成功将气力输送技术应用于ISP烧结烟尘的输送,针对闪速炼铜工艺中物料的性质,提出了合适的输送方式,为铜冶炼厂粉料输送技术的设计和选择提供了参考。随着气力输送技术的研究与应用不断取得进步,在有色冶炼行业的应用也将越来越广泛,效果越来越显著。     

联碱装置轻灰和重灰气力输送的可行性研究

介绍了气力输送的特点与分类,通过对轻灰和重灰进行密相气力输送试验,分析对纯碱进行气力输送的可行性,为公司设备改造提供数据支持。     

Tensile Creep Behavior of a Gas-Pressure-Sintered Silicon Nitride Containing Silicon Carbide

The tensile creep behavior of a gas-pressure-sintered silicon nitride containing silicon carbide was characterized at temperatures between 1375° and 1450°C with applied stresses between 50 and 250 MPa. Individual specimens were tested at fixed temperatures and applied loads. Each specimen was pin-loaded within the hot zone of a split-tube furnace through silicon carbide rods connected outside the furnace to a pneumatic cylinder. The gauge length was measured by laser extensometry, using gauge markers attached to the specimen. Secondary creep rates ranged from 0.54 to 270 Gs⁻¹, and the creep tests lasted from 6.7 to 1005 h. Exponential functions of stress and temperature were fitted to represent the secondary creep rate and the creep lifetime. This material was found to be more creep resistant than two other silicon nitride ceramics that had been characterized earlier by the same method of measurement as viable candidates for high-temperature service.     

化妆品中用硅粉、硅悬浮液的最新技术(日)

硅是化妆品生产不可缺少的原料之一。介绍了硅粉、硅悬浮液用于化妆品生产的最新技术, 特别是毛发调理产品中的应用。硅粉作为固体原料有望成为化妆品中新产品的生产原料。     

磷矿伴生硅资源制备单质硅的探讨

综述了国内外以四氟化硅、氟硅酸钠（钾）、无定SiO2为硅源制备单质硅的主要方法,并对以无定SiO2为硅源制备单质硅的工艺条件进行了研究与探索。     

Some New Perspectives on Oxidation of Silicon Carbide and Silicon Nitride

This study provides new perspectives on why the oxidation rates of silicon carbide and silicon nitride are lower than those of silicon and on the conditions under which gas bubbles can form on them. The effects on oxidation of various rate-limiting steps are evaluated by considering the partial pressure gradients of various species, such as O₂, CO, and N₂. Also calculated are the parabolic rate constants for the situations when the rates are controlled by oxygen and/or carbon monoxide (or nitrogen) diffusion. These considerations indicate that the oxidation of silicon carbide and silicon nitride should be mixed controlled, influenced both by an interface reaction and diffusion.     

Oxidation of Chemically-Vapor-Deposited Silicon Nitride and Slnglem-Crystal Silicon

Oxidation of {111} single-crystal silicon and dense, chemically-vapor-deposited silicon nitride was done in clean silica tubes at temperatures of 1000° to woo°C. The oxidation rates of silicon nitride under various atmospheres (dry O₂, wet O₂, wet inert gas, and steam) were several orders of magnitude slower than those of silicon under the identical conditions. The activation energy for the oxidation of silicon nitride decreased from 330 to 259 kJ/mol in going from dry O₂ to steam while that for Si decreased from 120 to 94 kJ/mol. The parabolic rate constant for Si increased linearly as the water vapor pressure increased. However, the parabolic rate constant for silicon nitride showed nonlinear dependency on the water vapor pressure in the presence of oxygen. The oxidation kinetics of silicon nitride is explained by the formation of nitrogen compounds (NO and NH₃) at the reaction interface and the counterpermeation of these reaction products.     

硅粉技术的选优

介绍了目前有机硅单体合成领域用工业硅粉主要的3种制粉技术,基于生产实践经验对比了不同制粉方法的技术经济指标和产品性能.     

In Situ Synthesis of Silicon Carbide Whiskers from Silicon Nitride Powders

Silicon carbide whiskers were synthesized in situ by direct carbothermal reduction of silicon nitride with graphite in an argon atmosphere. Phase evolution study reveals that the formation of β-SiC was initiated at 1400° to 1450°C; above 1650°C silicon was formed when carbon was deficient. Nevertheless, Si₃N₄ could be completely converted to SiC with molar ratio Si₃N₄:C = 1:3 at 1650°C. The morphology of the SiC whiskers is needlelike, with lengths and diameters changing with temperature. SiC fibers were produced on the surface of the sample fired at 1550°C with an average diameter of 0.3 μm. No catalyst was used in the syntheses, which minimizes the amount of impurities in the final products. A reaction mechanism involving the decomposition of silicon nitride has been proposed.     

Silicon Nitride–Silicon Carbide Nancocomposites Fabricated by Electric-Field-Assisted Sintering

Starting with Si-C-N(-O) amorphous powders, and using the electric field assisted sintering (EFAS) technique, silicon nitride/silicon carbide nanocomposites were fabricated with yttria as an additive. It was found that the material could be sintered in a relatively short time (10 min at 1600°C) to satisfactory densities (2.96–3.09 g/cm³) using 1–8 wt% yttria. With decreasing yttria content, the ratio of SiC to Si₃N₄ increased, whereas the grain size decreased from ∼150 nm to as small as 38 nm. This offers an attractive way to make nano-nanocomposites of silicon nitride and silicon carbide.     

Effect of mechanical properties of powder on pneumatic conveying in inclined pipe

Pneumatic conveying of fine powder has merits, such as no dust pollution and wide flexibility of pipeline layout. Thus, pneumatic conveying is widely used in industry. However, there is no information about the relation between the pressure drop for pneumatic conveying of fine powder and the mechanical properties of powder.We explained that the pressure drop of pneumatic conveying of powder in a horizontal pipe could be estimated from the dynamic friction coefficient of the powder in the previous paper. However, the relation between the pressure drop of pneumatic conveying in an inclined pipe and the mechanical properties of the powder is not cleared yet.The effect of mechanical properties and the angle of an inclined pipe on the pressure drop for pneumatic conveying of fine powder was examined and compared with the calculated results by our model. Based on these results, it is cleared that the pressure drop for pneumatic conveying of fine powder can be estimated from the dynamic friction coefficient of the powder and the inclined angle of the pipe.     

多孔石英基体上CVD法沉积氮化硅涂层的工艺、结构与性能研究

以甲硅烷(20％甲硅烷+80％氢气)和氨气作为反应前驱体,选择孔隙率为20％左右的多孔石英陶瓷基体,采用CVD法在多孔石英基体表面制备了氮化硅涂层.研究了沉积反应温度、反应压力、反应气体配比以及沉积时间等工艺参数对附着力的影响,确定了CVD法制备氮化硅涂层的最佳工艺参数,通过对所得涂层及复合材料进行抗弯强度和介电性能的表征,探讨了氮化硅涂层对多孔石英基体力学性能和介电性能的影响.