Slag Droplets Research Articles

A model of post-combustion in iron-bath reactors, part 4: results for post-combustion with preheated air

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A model of post-combustion in iron-bath reactors, part 3: theoretical basis for post-combustion with pre-heated air

This paper describes the post-combustion of carbon monoxide with pre-heated air, heat transfer from gas to melt via a mixture of metal and slag droplets, the microkinetics of reoxidation of metal droplets in the gas consisting of CO2, CO and N2, and the total heat and mass balance in the gas space and in the iron-bath. The computer program presented here Is flexible and can simulate various process modes of iron-bath reactors. The production rate of the reactor and the carbon consumption can be calculated herewith. Der Bericht beschreibt die Nachverbrennung des Kohlenmonoxides mit vorgewärmter Luft, die Wärmeübertragung vom Gas an die Schmelze über ein Tropfengemisch aus Metall und Schlacke, die Mikrokinetik der Reoxidation von Metalltropfen im Gasgemisch von CO2, CO und N2 und die gesamte Wärme- und Stoffbilanz im Gasraum und im Eisenbad. Das hier beschriebene Computerprogramm ist flexibel und kann verschiedene Prozeßvarianten simulieren. Die Produktionsleistung des Reaktors und der Kohlenstoffverbrauch werden damit berechnet.

Mechanisms of dust generation in a stainless steelmaking converter

The four possible mechanisms of dust formation in converter steelmaking are evaporation of metal, ejection of slag, ejection of metal and entrainment of solids. In order to describe the relation between process operation and dust formation and take appropriate measures to minimize the quantity of dust, more detailed information is needed on the amounts contributed by the different dust generation mechanisms. For their determination, dust samples were taken from the off‐gas during refining of five austenitic heats in a modified 80‐t AOD converter. On the basis of dust, metal and slag analyses and process and product gas flow rates, the contributions of the different dust generation mechanisms were quantitatively determined for blowing step I (pure oxygen blowing) and reduction step R (pure argon blowing). The predominant mechanism is ejection of metal and slag droplets by bursting of bubbles at the bath surface. Dust formation via the vapour phase in AOD steelmaking is of less importance than previously expected, the relative amount is only about 3 %. During the addition of fluxes through the converter mouth, the entrainment of solids plays a role, too.

In-flight formation of slag in spinning solid propellant rocket motors

Ground tests of solid propellant rocket motors have shown that metal-containing propellants produce various amounts of slag (primarily aluminum oxide), which are trapped in the motor case, causing a reduction, albeit small, of total impulse. Although not yet definitely established, the presence of a liquid pool of slag also may contribute to nutational instabilities that have been observed with certain spin-stabilized, upper-stage vehicles. Because of the rocket's axial acceleration—absent in the ground tests—estimates of in-flight slag mass have been very uncertain. Yet such estimates are needed to determine the magnitude of the control authority of the systems required for eliminating the instability. This paper describes a physical model of the slag transport in the motor and uses it to predict the in-flight slag mass from ground tests. Based on reported ground tests, it is concluded that the distribution function for slag droplet masses in the dynamically significant range is proportional to the -1.50 power of the mass. For geometrically similar motors with a given ratio of radial to axial acceleration, the trapped slag mass is shown to be proportional to the fourth power of the motor diameter. a(t) d(t) C c dd K kd m m0 R(t) ug

A model of post-combustion in iron-bath reactors, part 2: results for combustion with oxygen

The paper describes calculated results of post-combustion of CO, of heat transfer and of reoxidation for the conditions of a 170-t bottom-blown oxygen converter obtained on the basis of a model published in a previous paper. Calculations were carried out for heat transfer from gas to melt alternately via slag and via metal droplets suspended in the gas phase and acting as the transfer medium. In the case of slag droplets, heat transfer efficiencies of 80% are attainable. In the case of metal droplets, reoxidation limits the heat transfer efficiencies below 50%. The real degrees of post-combustion remain below 20%. Radiative heat transfer amounts to about 20% of total heat transfer

A model of post-combustion in iron-bath reactors, part 1: theoretical basis

The paper describes heat and mass balances, thermodynamic equilibria, and kinetics of the post-combustion reaction in iron-bath reactors and of the subsequent transfer of heat from gas to melt via metal and slag droplets suspended by the melt into the gas space above the met. Heat and mass balances, equilibria, and kinetcs of the reoxidation reaction of droplets, which accompanies the transfer of heat, are also described. Finally, the dynamics of droplet behaviour are presented

Emulsification and mass transfer in ladle metallurgy

Measurements of slag emulsification in gas‐stirred ladles were carried out in cold‐model systems of different geometric sizes. Detaching of slag droplets – necessary for efficient emulsification – only takes place if the flow velocity at the slag/metal interface exceeds a certain level.The use of a centric nozzle leads at high gas flow rates to considerably larger degrees of emulsification than eccentric stirring. The reason of this phenomenon is that the recirculation flow during centric gas injection transports larger amounts of emulsified droplets into deeper regions of the melt while during eccentric stirring there is more time for reseparation of slag droplets into the top slag.Comparing emulsification results with mass‐transfer measurements, the dependence between rate constants as well as degrees of emulsification and Froude number shows similar behaviour.

Internal structure of solidified iron blast-furnace slag (BFS) droplets formed by self-impinging jets

Etude par microscopie electronique a balayage de la microstructure des gouttelettes de laitier

Continuous duty solar coal gasification system using molten slag and direct-contact heat exchange

A new, very high temperature solar energy conversion technique which offers the potential of increasing the throughput and decreasing the cost of solar thermal coal gasification is described. Feedgas (CO 2 or steam) is heated to very high temperatures in a direct-contact droplet heat exchanger using slag droplets melted in a solar central receiver. The heated feedgas is then reacted with coal in conventional reaction vessels. Thermal storage at the full thermodynamic potential of the solar receiver is an integral feature of this approach and permits operation of the gasifier at full capacity during periods of no sun.

Nucleation and evolution of slag droplets in coal combustion

AbstractKinetics governing the nucleation and size variation of the slag droplets are first analyzed. Governing conservation equations are then formulated for the droplets and the surrounding gas‐vapor mixture. These equations are solved numerically for the environments representing a typical flow through the channel and diffuser of a coal fired, MHD, power generation system. The average droplet size, total number density and the droplet size distribution are found to be rather strongly influenced by the total slag mass fraction and the supersaturation ratio.

溶融鉄合金とCaO-Al<SUB>2</SUB>O<SUB>3</SUB>スラグとの間の界面張力の測定について

An improved method for measurement of interfacial tension between liquid iron alloy and liquid slag has been developed. The method is based on simultaneous determination both surface tension of liquid iron alloy σmg, which is measured by use of large drop method, and contact angle of liquid slag droplet on the liquid iron alloy. The interfacial tension ‘σms°’ between CaO-Al2O3 slag and liquid iron alloy was determined at 1 570°C by the method within 0.5 second after contacting the two liquids. Results obtained are as follows:(1) Oxygen dissolved in liquid iron brings about drastic decrement of a σms°, while both carbon and chromium in liquid iron lowers slightly σms°.(2) Both decrement of am; and that of crag by addition of one of the elements mentioned above into liquid iron are nearly equal to one another, and also both decrement of σms° and that of surface tension of CaO-Al2O3-SiO2 slag asg by addition of SiO2 component into the slag are nearly equal to one another.(3) Main cause of the interfacial tension character will be induced by independent contributions both of σmg and σsg respectively, while interaction between the slag and the iron alloy may play a minor role in the interfacial tension character.(4) Work of adhesion Wa between the slag and the iron alloy within 0.5 second after contacting the two liquids keeps constant value even when only one of the two liquids makes change in composition.