Tailoring the FeO/SiO2 ratio in electric arc furnace slags to minimize the leaching of vanadium and chromium

Based on recently published research on leaching control mechanisms in electric arc furnace (EAF) slags, it is assumed that a FeO/SiO2 ratio of around one leads to low leached V and Cr concentrations. This ratio influences the mineral phase composition of the slag toward higher amounts of spinel and a lower solubility of calcium silicate phases by suppressing the formation of magnesiowuestite and highly soluble calcium silicate phases. To evaluate this hypothesis, laboratory and scaled up tests in an EAF pilot plant were performed on slag samples characterized by elevated V and Cr leaching and a high FeO/SiO2 ratio. Prior to the melting experiments, the optimum FeO/SiO2 ratio was calculated via FactSageTM. In the melting experiments, the ratio was adjusted by adding quartz sand, which also decreased the basicity (CaO/SiO2) of the slag. As a reference, remelting experiments without quartz sand addition were conducted and additionally, the influence of the cooling rate of the slag was examined. The remelted (without quartz sand) and the remelted modified slags (with quartz sand) were analyzed chemically and mineralogically and the leaching behavior was investigated. The modification of the slags yielded a minimized release of V and Cr, supporting the hypothesis that the FeO/SiO2 ratio influences the mineralogy and the leaching behavior

Investigation of possible leaching control mechanisms for chromium and vanadium in electric arc furnace (EAF) slags using combined experimental and modeling approaches

In this study, possible leaching control mechanisms for Cr and V in electric arc furnace slags were investigated by using a multi-methodological approach. Aside from chemical and mineralogical bulk analyses, special emphasis was given to surface investigations of the slags prior to and after leaching. In addition, pH dependence leaching tests were performed and the obtained data were evaluated with hydrogeochemical models. Investigations revealed that Cr and V are mainly bound in spinel and wuestite as well as minor amounts of olivine. Spinel and wuestite do not dissolve during water leaching for 48 h, whereas, depending on the composition of olivine, this phase either dissolves and releases V and Cr congruently, or does not dissolve but may hydrate. Melilite may also hydrate, but neither V nor Cr were detected in this phase. It appears that leached V is subsequently adsorbed onto these newly hydrated phases. The combination of the applied methods further showed that the abundance of calcium silicates, spinel, and wuestite is influenced by the FeO/SiO2 and CaO/SiO2 ratio in the slag. Therefore, it is assumed that the leaching of V and Cr can be minimized by changing these ratios to favor the formation of Fe bearing calcium silicate and spinel instead of wuestite

Phagocytic ability of neutrophils and monocytes in neonates

<p>Abstract</p> <p>Background</p> <p>Infections by a variety of pathogens are a significant cause of morbidity and mortality during perinatal period. The susceptibility of neonates to bacterial infections has been attributed to immaturity of innate immunity. It is considered that one of the impaired mechanisms is the phagocytic function of neutrophils and monocytes. The purpose of the present study was to investigate the phagocytic ability of neonates at birth.</p> <p>Methods</p> <p>The phagocytic ability of neutrophils and monocytes of 42 neonates was determined using the Phagotest flow cytometry method, that assesses the intake of <it>E. Coli </it>by phagocytes, in cord blood and in peripheral blood 3 days after birth. Fifteen healthy adults were included in the study as controls.</p> <p>Results</p> <p>The phagocytic ability of neutrophils in the cord blood of neonates was significantly reduced compared to adults. The 3^rdpostnatal day the reduction of phagocytic ability of neutrophils was no longer significant compared to adults. The phagocytic ability of monocytes did not show any difference from that of adults either at birth or the 3^rdpostnatal day.</p> <p>Conclusions</p> <p>Our findings indicate that the intake of <it>E. Coli </it>by phagocytes is impaired at birth in both preterm and full term neonates compared to adults. This defect is transient, with the phagocytic ability in neonates reaching that of the adults 3 days after birth.</p

Object-Oriented Versus Conventional Software Development: A Comparative Case Study

Although object-oriented programming techniques have evolved into an accepted technology with recognized benefits for software development, profound qualitative and quantitative comparisons of conventional (module-oriented) and objectoriented systems are missing. We derive statements about qualitative and quantitative differences between conventional module-oriented and object-oriented software systems from the construction of a prototyping tool which was implemented in Modula-2 as well as in C++ (based on an object-oriented application framework). We also discuss the most striking reusability problems of object-oriented software building blocks

Where is Software Headed?

Before we outline future trends regarding software, let&apos;s briefly look back. Due to the enormous difficulties encountered with the development of software, many expected a single panancea to overcome the problems of the state of the art in software development. Computer aided software engineering, prototyping, automated programming, object-orientation and visual programming are just a few examples of technologies that staked the claim to cope with the known deficiencies of software development. The past taught us the following: No single technology or concept comprises a breakthrough. Furthermore, promising technologies are not applied immediately in industrial software development environments. On the contrary, it often takes decades until new technolgies exercise an impact outside of research laboratories. There are manyfold reasons for this dilemma, especially that many companies are stuck with legacy software and often believe that they cannot afford to overcome thi

Methodology

to emphasize that the production of software should not be an art, as it was then (and sometimes still is today), but an engineering discipline with a defined production process. As a consequence, approach models for the production of software were created, most noticeable the classic software life-cycle model (SLC) as described, e.g., in [Pomberger 93] and [Sommerville 85]. However, the classic SLC, although theoretically appealing, has some disadvantages, most of all that it cannot be used as is in practice. This led to several extensions and modifications of the model, whereas a very promising one is the use of prototyping, which leads to a prototypingoriented SLC. This paper first describes the problems with the classic approach model and how some of these problems can be solved by using a prototyping SLC. Then we describe TOPOS, a TOolset for Prototyping-Oriented Software development. Finally, we investigate how object-oriented programming, especially application frameworks, support a prototypingoriented approach