Slopping resulting from gas injection in a peirce-smith converter: Water modeling

The formation of standing waves in a water model of a Peirce-Smith converter was studied experimentally. The occurrence of a standing wave was found to be determined by the bath depth and tuyere submergence. The results showed that it is possible to obtain regions in the bath depth and tuyere angle/tuyere submergence plots where no standing waves were found and spitting was minimal. It is considered that the wave steepness is responsible for the changes in standing wave mode found in the water model and can contribute to the splashing of liquid from the first asymmetric standing wave if the amplitude of the standing wave is large. The results showed that the lower gas flow limit of the first asymmetric standing wave can be calculated from the power per unit mass required to sustain the standing wave. An experimental value of 0.7 to 1.0 watt/kg was obtained for the power per unit mass from the potential power supplied. It was shown that the contribution of the kinetic energy of the gas flow to the power per unit mass to form a first asymmetric standing wave can be obtained as a function of the tuyere angle.     

Combined injection of oxygen and neutral gas in the converter bath

Comparison reveals defects in existing methods for the combined injection of oxygen and neutral gas in the converter bath. A new technology is proposed, in which oxygen and neutral-gas jets are introduced in the working space through a two-level upper lance, while neutral gas is introduced through bottom units.     

声波耦合旋流对转炉一次烟气细颗粒物的去除

针对钢铁厂转炉一次烟气含尘浓度高、颗粒物细的特点,提出一种声波耦合旋流除尘新技术,用于降低转炉一次烟气细颗粒物浓度。采用单因素试验和响应面法研究了声压级、声频率、停留时间及烟气进气方式对颗粒物浓度降低率的影响。单因素试验结果表明,转炉一次烟气颗粒物团聚效率随声压级升高而增大,但存在最佳团聚频率。相比单一声波团聚,声波耦合旋流除尘技术对细颗粒物有很好的团聚效果。响应面法优化试验得出,当声压级为140 dB、声频率为1 400 Hz、停留时间为8 s时,采用旋流进气方式颗粒物浓度降低率最高,达33%。研究结果为提高转炉一次烟气中细颗粒物的去除效率及工艺开发提供参考。     

声波耦合旋流对转炉一次烟气细颗粒物的去除

针对钢铁厂转炉一次烟气含尘浓度高、颗粒物细的特点,提出一种声波耦合旋流除尘新技术,用于降低转炉一次烟气细颗粒物浓度。采用单因素试验和响应面法研究了声压级、声频率、停留时间及烟气进气方式对颗粒物浓度降低率的影响。单因素试验结果表明,转炉一次烟气颗粒物团聚效率随声压级升高而增大,但存在最佳团聚频率。相比单一声波团聚,声波耦合旋流除尘技术对细颗粒物有很好的团聚效果。响应面法优化试验得出,当声压级为140 dB、声频率为1 400 Hz、停留时间为8 s时,采用旋流进气方式颗粒物浓度降低率最高,达33%。研究结果为提高转炉一次烟气中细颗粒物的去除效率及工艺开发提供参考。     

High-pressure injection of air into a peirce-smith copper converter

Plant trials have been conducted at the Tacoma Smelter of ASARCO to assess the effect on tuyere blockage and refractory erosion at the tuyere line, of increasing the injection pressure of air into a Peirce-Smith converter. Four tuyeres each having an ID of 19.1 mm (0.75 inch) were installed toward one end of the tuyere line of the No. 4 converter. Air and oxygen-enriched air were injected at 414 kPag (60 psig) through these tuyeres and at the usual 83 kPag (12 psig) through the remainder of the tuyeres in an otherwise normal converter campaign. The test campaign consisted of 88 charges and lasted for 89 days. During this period, punching of the high-pressure tuyeres was found to be unnecessary; and when, as a precaution, the tuyeres were cleaned by hand at the end of a charge, they were always open. Also, it was observed that the flow of high-pressure air remained constant. Accretion formation around the tip of the high-pressure tuyeres varied from charge to charge and was influenced by the matte grade and the level of oxygen enrichment.     

The separation of the solids from the carrier gas during submerged powder injection

A fundamental aspect of submerged powder injection into melts which is not well understood is the extent to which the particles separate from the carrier gas upon injection, particularly under high solids loading conditions. In this study, the injection of nonwettable powders was investigated using a cold-model system at solids loadings from 1 to 25. Polyethylene powder was injected through a top-submerged lance into a cylindrical water bath under bubbling conditions. Air was used as the carrier gas. The apparatus was designed so that the particles remaining with the gas phase could be collected separately from those which escaped from the bubbles. The gas velocity (5.15 to 10.3 m/s), surface tension (0.03 to 0.072 N/m), lance diameter (4.7 to 7.4 mm), and particle size (< 500 μm) were independently varied. The separation of the powder from the primary gas bubbles was found to increase with increasing solids loading when the gas velocity, surface tension, and lance diameter were held constant. At constant solids loading, the separation increased with increasing gas velocity, increased with increasing lance diameter, and decreased with increasing surface tension. The separation was found to be independent of the particle size of the powder in the range of solids loadings tested. A theoretical relationship between the penetration efficiency and the particle jet Weber number successfully correlated with the experimental data.     

The injection of solids using a reactive carrier gas

The injection of nonwettable powders into melts in the bubbling regime was studied experimentally using a cold-model system. Polyethylene powder was injected into a cylindrical vessel containing water, through a vertical top-submerged lance, with insoluble (air) and soluble (ammonia) carrier gases. The concentration of particles in the liquid and the penetration length of the particle-liquid jet into the bath were measured, as the carrier gas composition, the gas and solids flow rates, and the particle size were varied. It was found that the concentration of particles retained in the liquid was up to 10 times higher, and the penetration length of the jet was up to three times higher when the soluble carrier gas was used instead of the insoluble carrier gas. For both carrier gases, the dispersed particle concentration increased with increasing gas flow rate and increasing particle size, whereas the penetration length of the jet increased with increasing gas and solids flow rates.     

Reduced interlitter variability in rats resulting from a restricted mating period, and reassessment of the "litter effect''

Rats were mated for two or 15 hours and variability of day-12-embryos in weight, protein content, and [3H]thymidine incorporation was compared in the long mating period (LMP) and short mating period (SMP) groups by a 2-level nested analysis of variance. Variability in day-20 fetal weight was similarly compared. In both groups day-12 embryonic weight was relatively more variable than day-20 fetal weight, and variability was less in SMP than LMP animals for each comparison made, although statistical significance was attained only for thymidine incorporation. "Litter effects' were noted but not of the magnitude reported by other investigators. It was concluded that inappropriate statistical methods have encouraged the belief that among-litter variability usually exceeds within-litter fetal weight variability. The teratological implications of reduced development variability and the "litter effect' are discussed.     

Solubility of MgO in slag during converter injection

The solubility of MgO in slags forming during injection in large converters is calculated on the basis of the model of associated ionic solutions and the polymer model of slags. A fundamental approach to suppressing the solubility of the periclase-carbon lining by means of magnesium-bearing fluxes is formulated. The quantity of magnesium oxide required to saturate the slag is determined, and the slag conditions that are optimal in terms of the mass of magnesium additive introduced are selected. To improve the technological expediency, the use of iron-bearing magnesia fluxes is recommended.