【作者】 潘时松；

【导师】 朱苗勇；

【作者基本信息】 东北大学 ， 钢铁冶金， 2008， 博士

【摘要】 向熔池中直接喷吹粉剂因具有良好的热力学和动力学条件,此技术在铁水预处理和钢包精炼中得到普遍应用。本文针对现有喷粉工艺存在喷枪价格高、二次氧化和吸氮严重及易引发重大生产事故等缺点,开发了适合于钢包精炼底喷粉的喷粉元件,并对底喷粉过程粉气流行为进行了理论和实验研究,为此新工艺应用奠定理论基础。本论文主要的研究内容及获得的主要结果如下：(1)对粉气流在狭缝内的运动机理进行了数值仿真研究,获得了颗粒和气流密度及速度、颗粒直径和黏度的定量关系,即(2ρp+ρg)dVp/dt=3aρg(Vp-Vg)2-k/(2dp)(dp/v)-k +2ρgg-2ρpg,(式中：a和k为系数；V为速度,m/s；t为时间,s；p为密度,kg/m3；d为直径,m；v为运动黏度,m2/s；下标p和g分别代表颗粒和气体)及不同雷诺数下的解析式。研究结果表明：小颗粒只需极短的时间和距离加速就可达到99%的运动终速Vp(T),在150m/s的氮气流中,直径为0.02mm石灰颗粒到达99%Vp(T)需要的时间和运动距离分别为0.01s和1.04m,而直径为2.00mm的石灰颗粒却需时间和距离分别为1.34s和167.21m；颗粒运动速度到达99%Vp(T)后,微小的速度增加量所需的加速距离却大量增加,0.02mm和2.00mm的石灰颗粒达到99.9%Vp(T)所需的距离分别为2.17m和328.65m；同类颗粒增大直径能缩短各自加速到穿透气／钢液界面的临界速度所需运动距离,0.200mm的石灰颗粒达到临界速度所需加速距离为0.46m,而2.00mm石灰的加速距离为0.21m；同直径的石灰、MgO、Fe2O3加速到99%Vp(T)的运动距离依次增加,而加速到各自得穿透临界速度的运动距离却依次减小。(2)对底喷粉钢液渗漏和粉剂堵塞的机理进行了理论研究和冷态和热态喷粉及5小时的磨蚀实验,提出了喷粉元件防止钢液渗漏的狭缝厚度即d＜-4σcosθ/(ρlgh);防止粉料堆积得流化室夹角即a＜180°—2φ；防止粉料在狭缝内堵塞的无导角狭缝。(3)对底喷粉熔池的均混特性进行了物理模拟,考察了底喷粉元件的喷嘴形状、狭缝厚度、狭缝之间的距离、位置及气体流量对熔池搅拌的影响规律,结果发现：气体流量在(0.209Nl/s～0.523Nl/s)范围内圆孔喷嘴的均混时间短于狭缝喷嘴；单条狭缝在一定范围内(0.15～0.30mm×15.00mm,0.50～0.80mm×15.00mm)其厚度对熔池的均混时间影响可以忽略,但狭缝厚度增加到一定值后均混时间明显增大,在本实验条件下,狭缝厚度从0.30mm增大到0.50mm,熔池的均混时间增加了7.42s；狭缝之间距离为5mm下,相同出口截面积的双狭缝喷嘴对熔池的均混时间略小于单狭缝喷嘴；无论是单条狭缝还是多狭缝,距中心1/2处喷吹熔池的均混时间是最小的,侧部喷吹均混时间最长,二者最大差值达17.60s。(4)对粉剂穿透特性进行了物理模拟研究,通过对狭缝厚度、喷吹位置、喷嘴形状及空塔速度对粉剂穿透行为的研究发现：狭缝喷吹中,窄缝的粉剂穿透比高于宽缝,在本实验中,窄缝的粉剂穿透比平均高出1.3%；空塔速度范围为(10m/s～60m/s)底部中心和距中心1/2处单条狭缝喷粉的穿透比高出圆孔喷粉分别为4.21%和1.38%；空塔速度范围为(10m/s～60m/s)距中心1/2处和侧部位置单狭缝喷吹粉剂的穿透比高出底部中心位置喷粉分别3.68%和2.56%；狭缝喷粉的穿透比随着空塔速度的增加先增加后减小,并存在一个最佳的空塔速度,在本实验条件下,底部中心和距中心1/2处的最佳空塔速度为50m/s,侧部喷吹的最佳空塔速度为40m/s。更多还原

【Abstract】 With good thermodynamics and kinetics conditions for injecting powder into molten bath, powder injection technology has been universally applied in hot-metal pretreatment and secondary refining ladle. A slot-bottom powder injection device, for bottom powder injection in refining ladle, was developed to overcome disadvantages of lance, such as high cost, reoxidation, absorbing nitrogen, introducing security accident, in existing powder injection technics. And the theoretical and experimental researches on gas/particle flow, in bottom powder injection, were carried out to study the new technology. The main contents and results achieved in this paper are as follows(1) The movement characteristics of gas/particle flow in slot were studied with numerical simulation, achieving the quantitative relationship of density, velocity, particle size and viscosity of air and particle, that is, (2ρp+ρg)dVp/dt=3aρg(Vp-Vg)2-k/(2dp)(dp/v)-k +2ρgg-2ρpg, (in which, a and k is coefficient; V is velocity, m/s; t is time, s;ρis density, kg/m3; d is diameter, m; v is viscosity, m2/s; subscript p and g represent particle and gas) and analytic formulas in different Reynolds number. The results show that small particles, only a very short time and distance, can be accelerated to 99 per cent of the movement terminal velocity(abbreviation Vp(T)), e.g. the time and distance required for movement, for diameter of 0.02 mm lime particle, are respectively 0.01 s and 1.04m, moreover, for diameter of 2.00 mm lime particle, are respectively 1.34 s and 167.21m; A slight increase in the speed required for the acceleration distance is a substantial increase after particle velocity reached 99% Vp(T), e.g. achieving 99.9% Vp(T) velocity, the distance required for 0.02mm and 2.00mm particles of lime are respectively 2.17m and 328.65m; Large-diameter particles achieve critical penetration velocity need less accelerating distance, e.g.0.20mm lime particle, accelerating 0.46 m, reaches the critical velocity, however,2.00mm lime particle, accelerating 0.21m, reaches the critical velocity; The movement distance is sequentially increasing for the same diameter of lime, MgO and Fe2O3 particle accelerating to 99% Vp(T), but the particles, accelerating to critical penetration velocity, are reversed.(2) Mechanism of liquid steel leakage and powder blocking in bottom powder injection ladle were investigated by theoretical research, cold test, hot test and 5 hours abrasion test. The results show that slot thickness of bottom powder injection device for anti-steel leakage follows the expression (d＜-4σcosθ/(ρlgh)). Conical angle of fluidized bed of bottom powder injection device for anti-powder blocking follows the expression (a＜180°—2φ). No leading angle of slot of bottom powder injection device can prevent powder blocking in slot.(3) The characteristics of homogeneous mixing of molten bath-in bottom powder injection ladle were investigated through physical simulation. Nozzle shape, slot thickness, the distance between the slots, positions and gas flow rates were also carried out to optimize the powder injection process. The results show that the mixing time of round nozzle is shorter than that of slot nozzle under gas flow rates (0.209Nl/s～0.523Nl/s). When single slot specifications in 0.15-0.30mm×15mm or 0.50-0.80mm×15mm, its thickness has no influence on mixing time of molten bath, when slot thickness increase to some degree, the mixing time increase significantly, e.g. The mixing time of molten bath increased 7.42s when slot thickness broadened from 0.30mm to 0.50mm in the experiments. The mixing time of the double-slot nozzle with the distance between the slots of 5 mm is slightly less than that of single-slot nozzle in the same cross-sectional area. Either single-slot or multi-slot nozzle, bath mixing time in 1/2L of centre is shortest and that in side injection is longest, the two largest margin of 17.60s.(4) The characteristics of penetration of powder in bottom powder injection ladle are investigated by physical simulation. Nozzle shape, slot thickness, the distance between the slots, positions and gas velocity were also carried out to study the powder injection process. The results show that powder penetration ratio of narrow slot nozzle is higher than that of wide slot nozzle, e.g. the narrow slot nozzles’powder penetration ratio is higher than the wide slot nozzle average 1.3% in the experiments. Powder penetration ratio of single-slot nozzle, at the bottom center and distance to the central 1/2 positions, are higher than that of round nozzle respectively 4.21% and 1.38% in gas velocity (10m/s-60m/s). Powder penetration ratio of single-slot nozzle, at side and distance to the central 1/2 positions, are higher than that of single-slot nozzle at the bottom center respectively 3.68% and 2.56% in gas velocity (10m/s-60m/s). In bottom powder injection through slot nozzle, powder penetration ratio increased firstly, and then decreased with the gas velocity increasing. And in which there was a gas velocity to be the best for powder penetration ratio, e.g. the best gas velocity for bottom powder injection and side powder injection were respectively 50m/s and 40m/s in the experiments.更多还原