Preparation of Pre-Reduced Briquettes and Studies on the Kinetics of the Process Under Reduced Pressure

INVESTIGATIONS has been carried out to find the optimum conditions for the production of highly reduced iron ore briquettes suitable as a blast furnace feed from Indian ore fines and low grade coke/wool charcoal under reduced pressure 1 x 101 mm. (Hg.) The effects of time (1/4 hr. to 6 hr.) temperature (950°C to 1150°C and Fe20 1,C ratio (1/3 to 1/5) on the rate of reduction of iron ore brique-ttes have been studied. From the kinetic results, a mecha-nism for reduction of iron oxide in iron ore briquettes is proposed and optimum conditions for production of highly reduced iron ore briquettes are summarised

Dynamic model of basic oxygen steelmaking process based on multi-zone reaction kinetics : modelling of manganese removal

In the earlier work, a dynamic model for the BOF process based on the multi-zone reaction kinetics has been developed. In the preceding part, the mechanism of manganese transfer in three reactive zones of the converter has been analyzed. This study identifies that temperature at the slag-metal reaction interface plays a major role in the Mn reaction kinetics and thus a mathematical treatment to evaluate temperature at each reaction interface has been successfully employed in the rate calculation. The Mn removal rate obtained from different zones of the converter predicts that the first stage of the blow is dominated by the oxidation of Mn at the jet impact zone, albeit some additional Mn refining has been observed as a result of the oxidation of metal droplets in emulsion phase. The mathematical model predicts that the reversion of Mn from slag to metal primarily takes place at the metal droplet in the emulsion due to an excessive increase in slag-metal interface temperature during the middle stage of blowing. In the final stage of the blow, the competition between simultaneous reactions in jet impact and emulsion zone controls the direction of mass flow of manganese. Further, the model prediction shows that the Mn refining in the emulsion is a strong function of droplet diameter and the residence time. Smaller sized droplets approach equilibrium quickly and thus contribute to a significant Mn conversion between slag and metal compared to the larger sized ones. The overall model prediction for Mn in the hot metal has been found to be in good agreement with two sets of different size top blowing converter data reported in the literature

Dynamic model of basic oxygen steelmaking process based on multi-zone reaction kinetics : model derivation and validation

A multi-zone kinetic model coupled with a dynamic slag generation model was developed for the simulation of hot metal and slag composition during the BOF operation. The three reaction zones, (i) jet impact zone (ii) slag-bulk metal zone (iii) slag-metal-gas emulsion zone were considered for the calculation of overall refining kinetics. In the rate equations, the transient rate parameters were mathematically described as a function of process variables. A micro and macroscopic rate calculation methodology (micro-kinetics and macro-kinetics) were developed to estimate the total refining contributed by the recirculating metal droplets through the slag-metal emulsion zone. The micro-kinetics involves developing the rate equation for individual droplets in the emulsion. The mathematical models for the size distribution of initial droplets, kinetics of simultaneous refining of elements, the residence time in the emulsion, dynamic interfacial area change were established in the micro-kinetic model. In the macro-kinetics calculation, a droplet generation model was employed and the total amount of refining by emulsion was calculated by summing the refining from the entire population of returning droplets. A dynamic FetO generation model based on oxygen mass balance was developed and coupled with the multi-zone kinetic model. The effect of post combustion on the evolution of slag and metal composition was investigated. The model was applied to a 200-ton top blowing converter and the simulated value of metal and slag was found to be in good agreement with the measured data. The post-combustion ratio was found to be an important factor in controlling FetO content in the slag and the kinetics of Mn and P in a BOF process

Protein-coding and non-coding gene expression analysis in differentiating human keratinocytes using a three-dimensional epidermal equivalent

The epidermal compartment is complex and organized into several strata composed of keratinocytes (KCs), including basal, spinous, granular, and corniWed layers. The continuous process of self-renewal and barrier formation is dependent on a homeostatic balance achieved amongst KCs involving proliferation, diVerentiation, and cell death. To determine genes responsible for initiating and maintaining a corniWed epidermis, organotypic cultures comprised entirely of stratiWed KCs creating epidermal equivalents (EE) were raised from a submerged state to an air/liquid (A/L) interface. Compared to the array proWle of submerged cultures containing KCs predominantly in a proliferative (relatively undiVerentiated) state, EEs raised to an A/L interface displayed a remarkably consistent and distinct proWle of mRNAs. Cultures lifted to an A/L interface triggered the induction of gene groups that regulate proliferation, diVerentiation, and cell death. Next, diVerentially expressed microRNAs (miRNAs) and long noncoding (lncRNA) RNAs were identiWed in EEs. Several diVerentially expressed miRNAs were validated by qRT-PCR and Northern blots. miRNAs 203, 205 and Let-7b were up-regulated at early time points (6, 18 and 24 h) but downregulated by 120 h. To study the lncRNA regulation in EEs, we proWled lncRNA expression by microarray and validated the results by qRT-PCR. Although the diVerential expression of several lncRNAs is suggestive of a role in epidermal diVerentiation, their biological functions remain to be elucidated. The current studies lay the foundation for relevant model systems to address such fundamentally important biological aspects of epidermal structure and function in normal and diseased human skin

Modelling the human epidermis in vitro: tools for basic and applied research

Culture models of tissues and organs are valuable tools developed by basic research that help investigation of the body functions. Modelling is aimed at simplifying experimental procedures in order to better understand biological phenomena, and consequently, when sufficiently characterized, culture models can also be utilized with high potential in applied research. In skin biology and pathology, the development of cultures of keratinocytes as monolayers has allowed the elucidation of most functional and structural characteristics of the cell type. Beside the multiple great successes that have been obtained with this type of culture, this review draws attention on several neglected characteristics of monolayer cultures. The more sophisticated models created in order to reconstruct the fully differentiated epidermis have followed the monolayers. The epidermal reconstruction produces all typical layers found in vivo and thus makes the model much less simple, but only this kind of model allows the study of full differentiation in keratinocyte and production of the cornified barrier. In addition to its interest in basic research, the reconstructed epidermis is currently gaining a lot of interest for applied research, particularly as an alternative to laboratory animals in the chemical and cosmetic industry. Today several commercial providers propose reconstructed skin or epidermis, but in vitro assays on these materials are still under development. In order to be beneficial at long term, the validation of assays must be performed on a material whose availability will not be interrupted. We warn here providers and customers that the longevity of in vitro assays will be guaranteed only if these assays are done with well-described models, prepared according to published procedures, and must consider having a minimum of two independent simultaneous producers of similar material

Investigation into the cause of spontaneous emulsification of a free steel droplet : validation of the chemical exchange pathway

Small Fe-based droplets have been heated to a molten phase suspended within a slag medium to replicate a partial environment within the basic oxygen furnace (BOF). The confocal scanning laser microscope (CSLM) has been used as a heating platform to interrogate the effect of impurities and their transfer across the metal/slag interface, on the emulsification of the droplet into the slag medium. The samples were then examined through X-ray computer tomography (XCT) giving the mapping of emulsion dispersion in 3D space, calculating the changing of interfacial area between the two materials, and changes of material volume due to material transfer between metal and slag. Null experiments to rule out thermal gradients being the cause of emulsification have been conducted as well as replication of the previously reported study by Assis et al.[1] which has given insights into the mechanism of emulsification. Finally chemical analysis was conducted to discover the transfer of oxygen to be the cause of emulsification, leading to a new study of a system with undergoing oxygen equilibration

Friction and wear properties of steel backed Al–10Sn–4Si–1Cu metallic strips prepared via spray atomization–deposition-rolling route

In various load bearing structural applications related to automotive industries, steel backed aluminum alloy strips are considered. For such applications, it is desired to design appropriate alloy composition for metallic strip so that good tribological properties can be achieved. In our ongoing efforts to accomplish this aim,we have recently fabricated a steel backed Al–10Sn–4Si–1Cu bearing strip, which is prepared by spray depositing the molten bearing alloy on a steel substrate, followed bywarm rolling of the resulting laminated strip to different thickness reductions up to 80%. The tribological performance of the steel backed Al–10Sn–4Si–1Cu strips is evaluated against the bearing steel. While the recorded steady state coefficient of friction (COF) does not show any noticeable difference (varying in the range of 0.6–0.7) with respect to difference in warm rolling conditions, the fretting wear rate (10–26×10−5 mm3 N−1m−1) of the steel backed and warm rolled strips exhibits a systematic decrease in wear rate with increase in amount of warm rolling. SEM-EDS analyses reveal the oxidative wear and the extensive cracking of alumina rich tribolayer as the dominant material removal mechanisms. The tribological properties of the spray deposited and 80% rolled steel backed Al–10Sn–4Si–1Cu bearing strip is compared with those of a commercially available Al–Sn based sleeve bearing under identical fretting conditions

Direct measurement of the direction, size, and velocity of droplets generated by top‐blowing

Abstract Problems associated with top‐blowing are present in most steel plants. While it promotes high reaction rates, it can cause loss of yield, working hazards, and increased maintenance cost by spitting, skulling, or lid sticking. Although the basic physics of the splashing phenomenon have already been established, earlier studies have not addressed the velocities of splashing droplets. Furthermore, existing information on the size and impingement angle of the droplets is based on indirect measurements. Herein, a direct measurement method for splashing droplets is developed that obtains the number of droplets, splashing angle, droplet velocity, and diameter at the same time. It is found that existing correlations overestimate the droplet diameter, because they are biased by the indirect method and overfit the results obtained with raw iron. Grid measurements indicate that all droplet properties strongly depend upon the sampling position. Finally, the splashing angle is found to become steeper while the lance height decreases. However, the effect is less correlated with the cavity mode than assumed in the literature. Further measurements are proposed, using the methodology developed in this work, to derive more comprehensive droplet property correlations. By that, lance designs and blowing practices can be optimized