转炉局域传质和混匀效果

采用冷态转炉对转炉熔池局域流动和传质效果进行了研究.选用不同氧枪喷头、枪位和熔池形状进行实验,通过测量熔池各区域的电导率值来研究熔池局域传质和混匀效果.根据实验结果,分析了各因素对熔池传质、死区分布、混匀时间及熔池速度均匀性等的影响.研究结果发现:标准熔池(径深比为3.1)中,熔池死区主要位于熔池底部侧壁和环流中心处;浅型熔池(径深比为5.2)中,熔池死区主要位于熔池侧壁.适当增加氧枪喷孔倾角和熔池径深比,有利于增大熔池环流半径,改善熔池内部流动,减小熔池内部死区.     

Cold model studies of mixing and mass transfer in steelmaking vessels

Abstract

Room temperature model studies using water to simulate 'metal' and paraffin oil (when required) as 'slag' were conducted to study the extent of mixing and the rate of mass transfer between metal and slag in the 130 t basic oxygen furnaces (BOFs) in operation in Tata Steel. Several systems of gas injection including top blowing, combined blowing and exclusive bottom purging were investigated. Similar work was undertaken in a room temperature model of an 80 t energy optimising furnace (EOF), in operation for a brief period earlier in Tata Steel. Details of the optimum blowing conditions, including the number/distribution of bottom tuyeres for the BOFs, are elaborated in the present paper. How mixing/mass transfer in an EOF compares with the BOF case(s) is also highlighted.     

Model study on mixing and mass transfer in ferroalloy refining processes

An experimental study has been performed to investigate the bath mixing intensity induced by a high-strength submerged gas injection in a bottom blown air-stirred one-seventh water model of Creusot-Loire Uddeholm (CLU) reactor using three different tuyere configurations. Experimental results have been discussed in terms of the mass transfer rate and mixing time. The air flow rates varied from 0.00599 to 0.01465 m³/s. The mixing time was determined at various gas flow rates, bath heights, and nozzle orientations, both in the presence and absence of a second phase. The mixing time was found to decrease with increasing gas flow rate and decreasing bath height. The influence of bath mixing intensity on mass transfer between metal (water) and slag (paraffin) was studied by measuring the transfer of benzoic acid from the gas-stirred water bath to paraffin as a function of the gas injection parameters. The bath mixing intensity was characterized by the value of the mass transfer rate constant. The rate constant of mass transfer between the metal and slag was found to increase with increasing gas injection rate and decreasing bath height.     

Model calculations for mass transfer with mixing in ladle metallurgy

It is well known that in secondary metallurgy during gas stirring, zones with differing degrees of homogeneity can occur in the liquid steel. By means of model calculations it will be demonstrated under which conditions mixing has to be considered for mass-transfer phenomena, as for example desulphurization. Under unfavourable conditions, i.e. large regions with low flow velocities – so-called dead zones – and low values for the exchange volume flow between these regions and the bulk volume, the equalization of concentration will become the rate-determining step for the total mass transfer. In order to avoid or minimize dead zones, the general flow pattern in the ladle has to be optimized.