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.     

Synthesis gas production using oxygen storage materials as oxygen carrier over circulating fluidized bed

A novel process for synthesis gas production over Circulating Fluidized Bed （CFB） using oxygen storage materials as oxygen carder was reported. First, oxygen in the air was chemically fixed and converted to lattice oxygen of oxygen storage materials over regenerator, and then methane was selectively oxidized to synthesis gas with lattice oxygen of oxygen storage materials over riser reactor. The results from simulation reaction of CFB by sequential redox reaction on a fixed bed reactor using lanthanum-based perovskite LaFeO3 and La0.8Sr0.2Fe0.9CO0.1O3 oxides prepared by sol-gel, suggested that the depleted oxygen species could be regenerated, and methane could be oxidized to synthesis gas by lattice oxygen with high selectivity. The partial oxidation of methane to synthesis gas over CFB using lattice oxygen of the oxygen storage materials instead of gaseous oxygen should be possibly applicable.     

Simulation of turbulent fluxes in a ladle with gas injection

The mixing when gas is injected into liquid metal is theoretically studied. Physical modeling shows that the similarity of the model and sample (scaling and proportionality) must be taken into account in selecting the model. The influence of the injection rate on the batch hydrodynamics and the conditions of bubble motion is established.     

The breakup of bubbles into jets during submerged gas injection

There has never been any fundamental explanation presented for the transition from the bubbling regime to the jetting regime when gas is injected into liquid at high velocity through submerged tuyeres. This is an important issue in metallurgical processes, since the flow regime is known to influence refining rates, refractory erosion, and the penetration of the liquid into the tuyere. Based on the observation that many small droplets of liquid and gas bubbles are formed to create the jets, a combined Kelvin-Helmholtz and Rayleigh-Taylor instability analysis has been applied to bubbles forming at submerged tuyeres. For particular wavelengths of disturbances, the interface will be unstable and create bubbles and droplets. The critical injection velocity for instability depends on surface tension, tuyere diameter, and the gas-to-liquid density ratio, which can be summarized by We = 10.5(ρ*)^−1/2, where We is the Weber number based on the gas velocity and density and tuyere diameter, and ρ* is the gas-to-liquid density ratio. The importance of surface tension had not been appreciated previously for this regime of gas injection. There is considerable controversy in the literature concerning the measurement of the transition from bubbling to jetting. The 70 pct “linking” point, proposed by Ozawa and Mori, describes the situation where 70 pct of the bubbles link with the preceding bubbles and produce a reasonably steady jet. The theoretical correlation developed above predicts the velocity to reach this point ±20 pct (95 pct confidence level) in a variety of systems from six different groups of workers. The theoretical analysis demonstrates that the instabilities are primarily capillary in nature, not gravity waves, which explains the observation that orientation has little effect on the jetting transition.     

Prolonged intraperitoneal infusion of 5-fluorouracil using a novel carrier solution

A novel peritoneal carrier solution, Icodextrin 20 (7.5%), has allowed exploration of prolonged, intraperitoneal (i.p.) infusion of the cytotoxic drug 5-fluorouracil (5-FU). A phase I and pharmacokinetic study was performed to determine the toxicities and maximum tolerated dose of prolonged and continuous intraperitoneal 5-FU in patients with peritoneal carcinomatosis. Seventeen patients were entered into this study. Each patient had a Tenckhoff catheter placed into the peritoneal cavity under general anaesthetic. After initial flushing and gradual increase in exchange volumes with Icodextrin 20, 5-FU was administered daily from Monday to Friday, 50% as a bolus in the exchange bag and 50% in an elastomeric infusor device delivering continuous 5-FU to the peritoneal cavity at 2 ml h-1. Treatment was continued for 12 weeks or until intolerable toxicity developed. Abdominal pain and infective peritonitis proved to be the main dose-limiting toxicities. Initial problems with infective peritonitis were overcome by redesign of the delivery system, and it proved possible to deliver 300 mg m-2 5-FU daily (5 days per week) for 12 weeks. Pharmacokinetic studies showed i.p. steady-state 5-FU concentrations (mean 47 500 ng ml-1) that were > 1000-fold higher than systemic venous levels (mean 30 ng ml-1).     

Slopping resulting from gas injection in a peircesmith converter: The period of the standing wave

The periods of the transverse standing waves occurring in the Peirce-Smith converter geometry as a function of bath depth were solved using linear wave theory by formulating an integral equation of the second kind. The eigenvalues of the integral equation gave the wave periods which were calculated to four-figure accuracy. The eigenvalues were approximated using Chebyshev polynomials for the first four wave modes. They include the complete range of eigenvalues for the first two symmetric standing waves, which has not been reported in the literature. The asymptotic eigenvalues for the transverse standing waves are given. Experimental results from a water model agreed with the theoretical predictions over a wide range of bath depths. The first symmetric standing wave was enhanced by the presence of the longitudinal standing wave, which showed that the three-dimensional geometry of the model was important in the modeling of the Peirce-Smith converter. Data from a Peirce-Smith copper converter were in reasonable agreement with the theory. An analysis of the standing wave frequency showed that the presence of standing waves could be minimized by a change in the geometry.     

Flow regimes in submerged gas injection

The behavior of gas discharging into a liquid has been investigated in the labora-tory and in plant. The laboratory work has involved the injection of different gases from a submerged, horizontal tuyere into water, zinc-chloride solution, and a mercury bath. High speed cinematography and pressure measurements in the tuyere have been carried out to characterize the flow regimes. In the case of the mercury bath, a novel “half-tuyere” has been developed to permit visual observation of the gas. In this way, two regimes of flow, bubbling and steady jetting, have been delineated as a function of the modified Froude number and the ratio of gas to liquid densities. Pressure measurements at the tuyere tip have been correlated to the different stages of bubble growth in the bubbling regime, and can be used to distinguish one flow regime from the other. The measured bubble frequency and volume correspond reasonably well to predictions of a simple model of bubble growth under conditions of constant flow. The forward penetration of the jet centerline from the tuyere tip has been measured and found to depend both onN _Fr′ andρg/ρl. In the industrial tests, pressure taps have been installed in the tuyeres of a nickel converter to monitor the pressure wave of the jets under normal, low pressure blowing operations. The measurements show that the converter jets operate in the bubbling mode with a bubble frequency of 10 to 12 s⁻¹, similar to a gas jet in mercury. Tests involving higher pressure injection indicate that the steady jetting, or underexpanded, regime obtains at pressures of about 340 kPa (50 psi). Based on equivalent experiments in the laboratory, it is clear that low pressure blowing has the disadvantage of poor penetration of air into the bath so that the jets rise close to the back wall and locally accelerate refractory wear. Moreover between the formation of successive bubbles, the bath washes against the tuyere mouth and contributes to accretion formation. This necessitates periodic punching of the tuyeres which also contributes to refractory wear at the tuyere line. The use of high pressure injection to achieve steady jetting conditions, as currently practiced in the new bottom blown steelmaking processes, should be considered to solve these prob-lems, and possibly usher in a new generation of nonferrous converters.     

Blast-furnace smelting with the injection of natural gas and coke-oven gas

A multizone mathematical model developed at Nekrasov Institute of Ferrous Metallurgy reveals the internal relations between the processes in a blast furnace. Using this model, the smelting processes and parameters in two different blast furnaces are investigated with wide variation in the flow rates of natural gas and coke-oven gas and in the distribution of the materials over the furnace radius. New scientific and practical findings are reported.     

Reduction of iron-silicon-oxysulfide by CO gas injection

The reduction of liquid oxysulfide in the Fe-Si-S-O system by CO gas injection has been studied by monitoring the exit gas composition. The reduction rate of oxygen was calculated from the volume of evolved CO₂. Sulfur-bearing species such as COS were close to the detection limit of the mass spectrometer, which indicated that the reduction of sulfur was very limited. The volume of evolved CO₂ reached steady values 1 minute after CO injection. The reduction reaction was controlled by a chemical reaction. The observed maximum reduction rate of oxygen at 1250 °C was 8.3×10⁻⁶ g-O/cm² s, which was within the range of the reduction rates in other melts such as iron oxide and iron silicates.     

Application of high-temperature extraction in a carrier gas for a quantitative determination of TiN in rail steel

The possibility of application of high-temperature extraction in a carrier gas to determine the content of nitrogen from titanium nitride inclusions in rail steel specimens of industrial melts and model alloys is considered. The temperatures of the onset of the dissociation of basic nitrides in rail steel are calculated under the conditions of a carbon-saturated melt. The nitrogen content in titanium nitrides in rail steel is calculated under the equilibrium conditions in the system. The experimental and calculated data on the characteristic temperatures of TiN dissociation and the nitrogen content in TiN are compared. A satisfactory convergence of the calculated and experimental data is obtained. The possibility of application of high-temperature extraction in a graphite crucible in a carrier gas flow for fractional analysis of nitrides in steel is shown.     

旋转喷吹除气装置原理及两种除气装置在应用中的对比

为了降低铝合金熔体中氢含量,提高金属纯洁度,从而提高铝合金铸锭冶金质量,我单位购置了国内外两种除气净化装置,通过合理使用,达到了满意的除气效果,保证了铸锭的,台金质量。本文研究了在线除气装置的除气净化原理,从多个方面对比了两种装置的优缺点。     

The ultimate strength of solids

Abstract

There is an upper limit to the mechanical strength of any material under any particular test conditions. This limit is known as the ideal strength. The present paper attempts to define the ideal strength as closely as is presently possible. To this end, a brief account is first given of some of the highest strengths recorded experimentally. Then follows a short account of the published theoretical calculations of the ideal strength. Finally, the theoretical and experimental values are compared, and it is shown that in several instances these differ by less than a factor 2x.

Résumé

Il existe une limite supérieure de la résistance mécanique de tout rnatériau pour des conditions d'essai données. On donne a cette limite le nom dé résistance idéale. Dans l'article, on tente de définir la résistance idéale de la maniére la plus précise qu'il soit possible de la faire avec les connaissances actuelles. A cette fin, on présente d'abord un sommaire de quelqu'unes des plus hautes résistances déterminées expérimentalement. Suit une courte présentation des calculs théoriques pub liés pour la resistance idéale. Entin, on compare les valeurs théoriques et expérimentales, et on démontre que dans plusieurs cas elles différent par un facteur infériéur à 2.     

Intraperitoneal chemotherapy: a prolonged infusion of 5-fluorouracil using a novel carrier solution

A novel carrier solution, icodextrin 20 (7.5%) has allowed exploration of prolonged intraperitoneal (IP) infusion of the cytotoxic drug, 5-fluorouracil. Eighteen patients with intraperitoneal carcinomatosis were entered into a feasibility and pharmacokinetic study of prolonged regional (IP) chemotherapy.. Specialist nurses trained the patients to self-administer their own treatment via a permanent i.p. catheter. A twin bag delivery system was used to perform one exchange daily. It proved possible to deliver continuous (5 days per week) i.p. 5-fluorouracil at doses of 200 mg/m2 and 300 mg/m2 for up to 12 weeks. The toxicities seen were infective peritonitis, nausea and vomiting, lethargy and anorexia. This was a nurse-led study and the home-based therapy holds promise for patients with malignant peritoneal disease.     

氧气高炉炉身喷吹煤气在炉内的分布

通过二维冷态物理模型对氧气高炉炉身喷吹煤气在炉内分布进行了实验研究,分别研究了炉身煤气总量、辅助风口直径以及炉身喷吹煤气量与炉身煤气总量之比对炉身喷吹煤气在炉内分布的影响.结果表明,炉身喷吹煤气量与炉身煤气总量之比对炉身喷吹煤气在炉身分布起决定性作用,而炉身煤气总量和辅助风口直径的影响较小.同时,在炉身煤气上升过程中涡流扩散效应的影响也较小.通过对根据实验数据绘制的炉身等浓度分布图进行研究发现,炉身煤气分布主要分为两个不同的区域,一个是炉身喷吹煤气主流区,另一个是从高炉下部产生的上升煤气主流区.在炉身等浓度分布图的基础上通过回归分析的方法推导出炉身喷吹水平喷吹煤气的渗透公式.此外,辅助风口被安装在炉身下部有利于铁矿石在炉身的间接还原.     

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.     

Plume characteristics and liquid circulation in gas injection through a porous plug

Various forms of plumes have been identified following the injection of air at different rates through a porous plug into water contained in a ladle-shaped vessel. Discrete bubbles form at the plug and rise uniformly through the column of liquid at gas flow rates up to 14 cm³/s cm² of plug surface; at higher flow rates, groups of bubbles increasingly coalesce into larger gas pockets, and beyond about 40 cm³/s cm², the gas globes are large enough to cover the entire plug surface before detachment and gradual disintegration as they rise through the body of liquid. The gas fraction, as well as bubble frequency, bubble velocity, and bubble size, have been measured in the various dispersion regimes by means of an electroresistivity probe. The radial distributions of gas fraction and bubble frequency are approximately bell-shaped about the axis of flow, and the reduced values are close to Gaussian functions of the reduced radial distance from the axis. The gas fraction along the axis has been correlated to the reduced height of the plume; it increases with decreasing distance above the plug and with increasing gas flow rate. The axial bubble frequency shows a decrease in the vicinity of the plug with the onset of bubble coalescence, but the values of the frequencies at all gas injection rates converge to about 12 s⁻¹ toward the surface of the bath. The mean bubble velocity increases with increasing flow rate but drops once coalescence is fully established. Conversely, there is a sudden increase in the mean bubble diameter with the onset of coalescence. The axial and radial components of the velocity of the liquid surrounding the plume have been measured by means of a Laser-Doppler Velocimeter (LDV), and the results show that the circulation patterns are identical, irrespective of the dispersion regime. The axial flow which is upward in the vicinity of the plume decreases in magnitude with increasing radial distance, ultimately reversing to an in-creasing downward flow beyond a certain distance from the plug axis. Similarly, the radial flow which is outward from the plume near the liquid surface decreases steadily with depth and eventually reverses to an inward flow at a depth independent of the gas injection rate. The profiles of the axial velocities are almost sigmoidal, except in the coalescence regime, where the effect of turbulence is profound at the upper liquid layers. The radial liquid velocities are generally small relative to the axial components, only about one-fifth as large, considering the maximum average values.     

Establishment time of liquid flow in a bath agitated by bottom gas injection

The establishment time of gas-liquid two-phase flows in a cylindrical bath agitated by bottom gas injection through a central single-hole bottom nozzle was investigated. Because the turbulence intensity in the bath was comparable to or larger than the unity, the conventional definition of the flow establishment time based on the history of mean velocity was not suitable for the present case. In fact, it was difficult to determine the flow establishment time based on the well-known 90 or 99 pct criterion for the mean velocity. Accordingly, two methods of determining the flow establishment time by focusing on the turbulence components instead of the mean velocity components were proposed. Velocity measurements were made with a two-channel laser Doppler velocimeter. The flow establishment time was correlated as a function of gas flow rate. Close agreement was obtained by the two methods.     

Free convection in the bath of a bubbling-bed system during lateral gas injection

A mathematical model is proposed for the free convection in the bath of a bubbling-bed system. The bed is regarded as a pseudohomogeneous continuum with variable physical properties. The primary equations are written for the inelastic case, under the Boussinesq approximation.     

The influence of gas injection arc stabilization and electrode consumption in electric furnaces

Abstract

By means of relatively simple modifications a conventional arc furnace can be made to produce a long, stable plasma flame. This technique may be applied to scrap melting in the steel industry.

The results of laboratory experiments and plant trials, using à 3-ton production furnace, are discussed with respect to electrical characteristics, and potential refractory , electrode, and power savings

Résumé

Au moyen de modifications relativement simples, un four à arc conventionnel peut produire une flamme de plasma longue et stable.

Cette technique peut être appliquée à la fusion de la ferraille dans l'industrie de l'acier.

Les resultats d'expériences de laboratoire et d'essais en usine sur un four de production de 3 tonnes sont discutes par rapport aux caractéristiques électriques et du point de vue des réfractaires, des electrodes et de l'économie de puissance.