火焰原子吸收法测定钛合金中铬的方法比较

钢铁中的铬可以在贫燃与富燃空气—乙炔火焰和笑气乙炔火焰中测定,其测定受火焰条件、溶液介质及其价态的影响很大,在富燃空气—乙炔火焰中,共存元素的干扰尤其严重。 本文采用上述三种火焰条件,对钛合金中测定铬的共存元素干扰、酸介质影响、测定范围及方法的准确度、精密度进行了研究与比较。     

火焰原子化条件的优化在实际工作中的应用

原子化器是原子吸收光谱仪最关键、最重要的部件,而火焰原子化器是史上使用时间最长、技术上最成熟、应用范围最广的原子化方法,火焰原子化条件的选择与调节会对测定结果的准确度、灵敏度产生很大的影响,作者在长期操作原子吸收光谱仪器过程中,积累了丰富的经验。文章从火焰原子化器的组成结构及性能、影响火焰原子化效率的因素、火焰原子化条件的优化三个方面进行了阐述,总结了火焰原子化器条件优化的方法,仅供读者参考。     

火焰清理机能源介质对清理质量的影响

火焰清理机利用高温火焰去除板坯表面缺陷，生产出高品质钢材，其已为越来越多的钢铁企业所认可。使用不同能源介质的烧嘴火焰存在差异，对板坯清理效果和品质影响巨大。根据国内几个钢厂的火焰清理介质参数，基于计算流体力学方法建立烧嘴火焰数值模型，并模拟出相对应的温度场、速度场，研究分析各类能源介质烧嘴火焰性状的差异，进而推测其对板坯质量的影响，同时结合生产实际研究火焰清理的最佳模型。     

立体结构障碍物不同阻塞比对火焰传播的影响

通过运用自行设计的火焰加速系统,文章研究了立体结构障碍物对预混甲烷火焰传播过程中火焰传播速度和超压的影响。选用五种立体结构障碍物,平板、长方体、三棱柱、四棱柱和圆柱,其阻塞比分别有20%、40%和60%。结果表明在相同阻塞比下,平板、三棱柱对增加火焰传播速度和超压相对较大,长方体居中,圆柱、四棱柱影响相对有限。研究有助于对矿井瓦斯爆炸预防控制以及为工业安全设计提供参考。     

横向声波扰动下的乙醇燃烧火焰结构和振荡特性

为研究声波灭火的机理,分析声波对非封闭火焰的具体控制行为,对3、4和5 cm直径油池火焰在30 ~ 90 Hz声波作用下的火焰形态及燃烧特征进行了分析。对火焰图像的分析发现,横向声波加剧了涡旋的不稳定运动,声强迫下的火焰形态可归结为间歇截断、偏转和稳定燃烧三种状态。火焰几何尺寸的数值分析表明:间歇截断和偏转状态下的火焰表面高度扭曲皱褶,具有更高的分形维数。对火焰面积、高度和宽度的频域信号分析表明:在间歇截断状态下火焰信号极不稳定,频域峰值集中在0 ~ 10 Hz之间,声频率在火焰宽度信号的频域分布中始终突出。基于火焰倾角和Richardson数的关系提出了Ri数在声波作用下的形式,Richardson数分析表明:在50 ~70 Hz之间,火焰对声波频率的响应尤为显著,声频高于或低于该段频率时对火焰的影响存在边际效应,间歇截断和偏转状态的临界Ri_a?1数（声波作用下的火焰Richardson数的倒数）分别为10.32和2.92。      

炉壁黑度对火焰炉能耗的影响

通过对火焰炉炉内热交换过程及炉墙散热过程的理论分析，探明了炉壁黑度对火焰炉能耗影响的关系，为红外辐射涂料在火焰中的合理应用提供了理论参考。     

宽火焰燃烧器对加热炉的影响

对比分析传统烧嘴及宽火焰烧嘴的特点,对宽火焰烧嘴进行了仿真分析及工程应用,分析了宽火焰燃烧技术对加热炉的影响,结果表明:该技术有利于钢坯温度均匀性、降低氧化烧损及氮氧化物的排放.     

燃气轮机进气喷雾冷却下层流火焰的特性

建立了燃气轮机进气喷雾冷却条件下燃烧室的一维层流预混燃烧模型,研究了在不同化学当量比、温度和压力下H2O体积分数对火焰传播速度、火焰温度、燃烧产物分布的影响.研究结果表明:火焰传播速度随H2O体积分数升高而近似线性减小,采用进气雾化冷却技术时,可适当提高燃烧室中扩散燃烧所占比例,以此来稳定燃烧工况;火焰温度随混合气中H...     

原子吸收光度法测定铝合金中锶

对铝锶中间合金中锶的测定条件进行探讨，较系统研究了火焰状态、火焰位置、测定体系及干扰元素等对测定结果的影响。     

直接火焰冲击加热技术的研究与开发

为研发直接火焰冲击加热技术，设计了一种三重同心管逆扩散燃烧直接火焰冲击加热烧嘴，燃气采用丙烷，氧化剂中氧的体积分数为40%～70%，实现富氧燃烧。系统研究了燃气流量、氧化剂氧含量、空气过剩系数、烧嘴内外层通道氧化剂分配比例等燃烧工艺参数对烧嘴火焰形态和燃烧特性的影响，并在此基础上设计出窄间距多火焰烧嘴，提出了高温火焰温度间接测量方法。研究结果表明，三重同心管烧嘴外层通道微小氧化剂流量起到稳定高速火焰的作用。内外层氧化剂流量分配比例为20∶1时，火焰温度最高。各种燃烧工艺条件下，火焰温度都随着氧化剂中氧含量的增加而增加，火焰温度最高点距烧嘴出口的距离在70～120mm范围内。     

高超音速火焰喷涂粒子飞行行为研究

以高超音速火焰喷枪为研究对象,采用计算流体力学软件Fluent对高超音速火焰喷涂(HVOF)过程中的焰流流场以及粒子飞行过程进行数值模拟。HVOF系统以氧气为助燃气体,煤油为燃料。研究了加入粒子前喷枪内火焰焰流温度、速度和压力分布规律,采用离散相模型计算喷涂粒子的动力学飞行行为,探究了粒子大小、注入速度、球形度对粒子飞行行为的影响。发现最佳粒子粒径范围应为30～50 μm,在此范围内粒子均匀的分布在焰流中心,且为熔融状态,更易形成结合强度较高的涂层;小粒径粒子最佳注入速度为10～15 m·s?1,中等粒径粒子最佳注入速度为5～10 m·s?1,大粒径粒子最佳注入速度为1～5 m·s?1;与球形颗粒相比,非球形颗粒具有较高的阻力系数,在飞行过程中获得更大的动能和更少的热量。      

高温低氧空气燃烧火焰观察实验研究

介绍了一台用于研究火争特性的热态实验装置。观察了丙烷在不同预热空气温度及不同含氧浓度气氛中的火焰特征,实验中,采用电加热助燃剂,预热温度变化范围为３８０～１０００℃;采用掺氮气的方法调节助燃剂中气的体积浓度,其变化范围为２１％～２％,实验表明助燃剂温度及其含氧量对火焰特性有非常显著的影响;高温低氧条件下的火焰特性与传统燃烧火焰特性迥然不同,最后对工业炉窑采用高温低氧空气燃烧方式将产生的效益进行了计     

优级细锌粉的生产实践

以 2 #～ 3 #或 1#电解锌锭为原料 ,利用半煤气隔焰炉生产优级细锌粉 ,并对影响产品细度的因素进行探讨。     

提高铜精矿中金测定的精密度和准确度

研究了铜精矿的粒度分布及各粒级中金含量的赋存规律，发现由于铜精矿的特殊生产工艺，铜精矿的粒度85％集中在－200目，金量的90％也集中在－200目；并从磨样时间和磨样量两个方面试验了铜精矿的加工条件，得出铜精矿中分析测试金的较佳加工条件和加工粒度，加工制成的样品具有均匀性和代表性；从而建立了铜精矿中金的火焰原子吸收快速分析法。该方法操作简便、快速，分析结果稳定、准确，RSD≤4％。     

Synthesis of YVO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> Nanophosphors Through the Use of Urea and Aniline Fuels and Study of Their Microstructures and Optical Properties

In this paper, YVO₄:Eu³⁺ nanophosphors were synthesized via the simple combustion method by urea and aniline, individually. The particle size of produced powders and the combustion flame temperature were explained in thermodynamic terms. These phosphors were characterized by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, field emission scanning electron microscope and photoluminescence (PL) analyses. It was concluded that the amounts of released gas, adiabatic flame temperature, remaining compounds after combustion reaction, size of powders and optical properties depended strongly on the used combustion fuel. Also, the PL intensity of the phosphors synthesized by aniline was remarkably higher than that of phosphors synthesized by urea.     

Near-nanostructured WC-18 pct Co coatings with low amounts of non-WC carbide phase: Part I. Synthesis and characterization

Near-nanostructured WC-18 pct Co coatings, with low amounts of non-WC carbide phases, have been synthesized using high velocity oxygen fuel (HVOF) thermal spraying under spraying conditions of varying fuel chemistry, fuel-oxygen ratio, and powder particle size. The results show that the temperature the particles experience during spraying depends on the preceding parameters. Compared to available published results on WC-Co system coatings, nanostructured WC-18 pct Co coatings, synthesized in these experiments, contain very low amounts of non-WC carbide phase (less than 10 pct vol). This is comparable to that of the conventional WC-12 pct Co coating, prepared in the present study for comparison purposes. Regardless of whether the binder phase in the agglomerated feedstock powder particles melt or not, the WC particles do not appear to experience significant growth as a result of the spraying. The size of WC particles remains in the 200 to 500 nm range, consistent with that present in the feedstock powder. The as-received near-nanostructured WC-18 pct Co feedstock powder exhibits morphological characteristics that lead to low amounts of non-WC carbide phases in the coatings. The microstructure and phase constitution of the coatings depend on particle size of the feedstock powder and flame characteristics of the fuels during spraying. A higher particle temperature causes more decomposition of the WC phase but reduces porosity in the coatings, this occurs with higher flame temperature and smaller particle sizes. Propylene fuel produces less decomposition of the WC phase despite the higher flame temperature and, thus, provides the best combination of dense coating with low amount of non-WC phase.     

Flame formation and post-combustion at blowing of oxygen into a carbon monoxide containing slag foam

A combined post-combustion model (CPM) for smelting reduction was developed in a multi-national research project supported by the European Coal and Steel Community. The project partners were CSM, Rome, Hoogovens, Ijmuiden, MPI, Düsseldorf, and TUB, Berlin. This paper is a report about a flame model developed by TUB, Berlin. An oxygen jet is blown into a carbon monoxide containing slag foam. The jet entrains carbon monoxide and slag droplets. Carbon monoxide is combusted by oxygen to carbon dioxide and the developed heat is transferred by radiation from the gas to the surrounding slag and by radiation and convection to the entrained droplets. The droplets are mixed with the slag at the flame end so that also their heat content is finally transferred to the bulk slag. The model consists of a detailed treatment of the entrainment processes, the combustion reaction taking into account the carbon dioxide dissociation equilibrium, the enthalpy changes, and the heat transfer processes. One obtains two ordinary differential equations describing the temperature and composition of the flame gas as functions of the flame pass-way. They are solved numerically by the Runge-Kutta method. As the results, the main flame properties, namely the flame velocity, the diameter and the upwards angle of the flame, the amount of gas and slag entrained from the surroundings to the flame, the oxygen utilisation, from which the post-combustion degree is calculated, the flame temperature along the flame pass-way, and the total heat transfer from the flame gas to the slag, are described as functions of various internal and external parameters. The presented flame model is part of a general post-combustion and heat transfer model of a smelting reduction process with post-combustion in the slag.     

新型双旋流平焰烧嘴的研制与应用

介绍了一种新型双族流平焰烧嘴的设计思路、结构参数及工业试验结果。其结构特点是每个部件都易装易卸，其煤气旋流器的位置可根据煤气压力变化进行调节，无需稳焰器就可保证煤气压力在较大范围波动时，都可形成稳定的平展火焰。     

Plasma densification of agglomerated Cr2O3 powder for thermal spray coating

Abstract

Double plasma flame treatments were carried out on spray dried Cr₂O₃ agglomerated powders to increase their apparent density. The powders that were subjected to the first densification treatment didn't show the entirely melted state, and were fully melted only after the second plasma treatment. Plasma densification resulted in powder size decreasing as well as apparent density of particles and also resulted in the fluidity increasing due to the powder melting and surface smoothing effects. However, some parts of the particles after the second treatment showed a hollowed structure, especially for a particle size above 30 µm. The influence of the thermal conductivity of powder and the gas pressure within aggregates exposed to the plasma flame in the particle densification process was discussed in detail. The powder density strongly influenced the structure of plasma sprayed coatings. The dense coatings with high hardness and high bond strength was achieved in the coatings produced from Cr₂O₃ powders after plasma densification.