Mathematical modelling and the influence of process para-meters on the temperature profile in a submerged arc furnace producing ferro-chromium

Control of the temperature profile is a crucial factor for optimising the energy consumption and regulating the quality of the hot metal produced in submerged arc furn-ace. Factors such as the heat generated at the electrodes, the heat loss, the heat consumed by chemical reactions, the packing density of the charge materials etc. deter-mine the profile. This in turn decides the production rate and the chemistry of the hot metal. Controlling the level of impurities in the hot metal such as the level of silicon in ferro-chromium can be achieved through the mapping of the temperature profile and regulating the process accordingly. The communication describes the mathematical modelling of the temperature profile in the submerged arc furnace and analyses the influence of several process parameters on the same

Modern Approaches to Exact Diagonalization and Selected Configuration Interaction with the Adaptive Sampling CI Method.

Recent advances in selected configuration interaction methods have made them competitive with the most accurate techniques available and, hence, creating an increasingly powerful tool for solving quantum Hamiltonians. In this work, we build on recent advances from the adaptive sampling configuration interaction (ASCI) algorithm. We show that a useful paradigm for generating efficient selected CI/exact diagonalization algorithms is driven by fast sorting algorithms, much in the same way iterative diagonalization is based on the paradigm of matrix vector multiplication. We present several new algorithms for all parts of performing a selected CI, which includes new ASCI search, dynamic bit masking, fast orbital rotations, fast diagonal matrix elements, and residue arrays. The ASCI search algorithm can be used in several different modes, which includes an integral driven search and a coefficient driven search. The algorithms presented here are fast and scalable, and we find that because they are built on fast sorting algorithms they are more efficient than all other approaches we considered. After introducing these techniques, we present ASCI results applied to a large range of systems and basis sets to demonstrate the types of simulations that can be practically treated at the full-CI level with modern methods and hardware, presenting double- and triple-ζ benchmark data for the G1 data set. The largest of these calculations is Si2H6 which is a simulation of 34 electrons in 152 orbitals. We also present some preliminary results for fast deterministic perturbation theory simulations that use hash functions to maintain high efficiency for treating large basis sets

Documentation of Apollo 15 samples

A catalog is presented of the documentation of Apollo 15 samples using photographs and verbal descriptions returned from the lunar surface. Almost all of the Apollo 15 samples were correlated with lunar surface photographs, descriptions, and traverse locations. Where possible, the lunar orientations of rock samples were reconstructed in the lunar receiving laboratory, using a collimated light source to reproduce illumination and shadow characteristics of the same samples shown in lunar photographs. In several cases, samples were not recognized in lunar surface photographs, and their approximate locations are known only by association with numbered sample bags used during their collection. Tables, photographs, and maps included in this report are designed to aid in the understanding of the lunar setting of the Apollo 15 samples

Hydrometallurgical processing of anode slime for recovery of valuable metals

The anode slime obtained from Indian Copper Complex, Ghatsila was used for the recovery studies with the aim of developing a hydrometallurgical processing route. The chemical analysis of the slime showed that it contained valuable metals like copper, nickel, selenium, tellurium, gold, silver and platinum group metals. Characterisation study by XRD analy¬sis revealed the presence of various phases like NiO, CuSO4.5H20, NiSe, a-CuSe, Cu4SeTe. Cu2Te, (Cu02Ni08)O, Cu7Tey AgCu7 Te1,y Si02 etc. in the slime. Presence of free moisture, combined moisture, selenium and tellu¬rium were detected by TG/DTA studies. Preliminary leaching experiments of the anode slime in sulphuric and hydrochloric acid media at different conditions were carried out to recover copper, nickel and tellurium. Maxi¬mum copper recovery in sulphuric acid and hydrochloric acid leaching experiments at normal pressure was found to be about 55% and 77% respectively. In both the cases nickel and tellurium recoveries were poor. In the autoclave leaching copper and tellurium recoveries improved with increasing time and pressure. Maximum copper and tellurium recoveries to the tune of 85% and 71% respectively were achieved using 1 % sulphuric acid as leachant. On increasing the sulphuric acid concentration to 20% in the pressure leaching, the recoveries of copper and nickel improved to 95% and 46% respectively

Anodic dissolution behaviour of tungsten carbide scraps in ammoniacal media

In the present paper, potentiodynamic studies of WC scrap have been carried out as these studies give better idea about the anodic dissolution behaviour of the scrap material for their recycling to recover metal values. However, it has been seen that anodic passivation retards the dissolution of the scrap and adversely affects the recovery of metals. To minimise the passivity and to increase the anodic dissolution, some chemicals are often used as additives. Two different electrolytes namely hydrochloric acid and aqueous ammonia at varying concentrations had been employed for the above studies. The additives citric acid and oxalic acid were added to the acidic electrolyte whereas ammonium chloride, ammonium carbonate, ammonium sulphate were added in different concentration to the ammoniacal electrolyte. The studies revealed that 2% citric acid in 1N HCl was the optimum to achieve maximum anodic dissolution (current) of WC scrap. On the other hand, 2% NH4Cl was found suitable to obtain maximum anodic dissolution (current) in the ammoniacal (1N) medium. The potentiodynamic studies were followed by the actual electrodissolution experiments in an electrolytic cell with the help of a rectifier. The W and Co were recovered as tungsten oxide and metallic chips, respectively

An overview on different processes for recovery of valuable metals from tungsten carbide scrap.

Cemented tungsten carbide material has been widely used in the hard metal industry for the manufacture of cutting tools, drilling tools, mining and machining tools and high wear resistant parts. When these tool bits and components are scrapped, they are collected and processed for recycling following appropriate methods. Tungsten and cobalt both are strategic rare metals and the cost of these metals entrapped in these scraps is estimated to be very high. Therefore, WC scraps have been considered as an important secondary resource of cobalt and tungsten metals. Recycling of hard materials like tungsten carbide scrap require specialised techniques. This paper presents a review of the different processes reported so far to recover valuable metals (W, Co) from cemented tungsten carbide scrap materials. Recycling techniques following either hydro or pyrometallurgical or a combination of them to recover the valuable metals (W, Co) are discussed. Thermal oxidation in presence of air/oxygen generates friable oxides of metals contained in tungsten carbide hard material, which is either leached in acid/alkali to produce tungsten oxide or subjected to reduction by hydrogen to produce tungsten powder. Direct leaching of tungsten scrap in concentrated acid/alkali solutions has also been investigated and different value added materials like ammonium para tungstate, tungstic acid etc are produced in the subsequent processing of leach liquor. The electrochemical route has emerged as an attractive method as it is a single step dissolution process consuming very low energy. However, passivation has been reported to slow down the dissolution rate and hence, some additives have also been tried for continuous dissolution. The environmental and economical aspects of some of the important processes have also been highlighted in this paper

What Levels of Coupled Cluster Theory Are Appropriate for Transition Metal Systems? A Study Using Near-Exact Quantum Chemical Values for 3d Transition Metal Binary Compounds.

Transition metal compounds are traditionally considered to be challenging for standard quantum chemistry approximations like coupled cluster (CC) theory, which are usually employed to validate lower level methods like density functional theory (DFT). To explore this issue, we present a database of bond dissociation energies (BDEs) for 74 spin states of 69 diatomic species containing a 3d transition metal atom and a main group element, in the moderately sized def2-SVP basis. The presented BDEs appear to have an (estimated) 3σ error less than 1 kJ/mol relative to the exact solutions to the nonrelativistic Born-Oppenheimer Hamiltonian. These benchmark values were used to assess the performance of a wide range of standard single reference CC models, as the results should be beneficial for understanding the limitations of these models for transition metal systems. We find that interactions between metals and monovalent ligands like hydride and fluoride are well described by CCSDT. Similarly, CCSDTQ appears to be adequate for bonds between metals and nominally divalent ligands like oxide and sulfide. However, interactions with polyvalent ligands like nitride and carbide are more challenging, with even CCSDTQ(P)Λ yielding errors on the scale of a few kJ/mol. We also find that many perturbative and iterative approximations to higher order terms either yield disappointing results or actually worsen the performance relative to the baseline low level CC method, indicating that complexity does not always guarantee accuracy

Leaching of Korean monazite for the recovery of rare earth metals

The technological innovations resulted in various applications using rare earth metals (REM), which lead to a steep increase in their demand. Monazite is the second most essential naturally occurring phosphate mineral containing REM. The present work reports the recovery of REM from Korean monazite which contained mainly 50.12% rare earth oxide and 29.4% phosphate. For the recovery of REM from monazite, the hydrometallurgical process consisting of alkaline leaching of phosphate followed by acid dissolution of REM has been reported. As the presence of phosphate decreases the leaching efficiency of REM from monazite, the studies were carried out initially for hot digestion of phosphate present in the monazite in an autoclave using sodium hydroxide, which resulted in the formation of RE oxide and soluble sodium phosphate. To get the optimum condition for phosphate decomposition by alkaline leaching, the various process parameters such as concentration of sodium hydroxide, temperature, mixing time and pulp density were studied. The obtained slurry was washed with hot water and filtered to get sodium phosphate in the solution. A maximum of 99% phosphate was removed from monazite concentrate using 50% sodium hydroxide solutions (wt./vol.) at 170oC in 4 h mixing time maintaining the pulp density of 100 g/L. From the phosphate free monazite sample, REM was leached out using hydrochloric acid. More than 95% of REM was found to be leached out using 6M HCl at constant pulp density 100 g/L, temperature 90oC and mixing time 2 h. Further studies are in progress to obtain pure solution and salts of REM from chloride leach liquor using recipitation/ solvent extraction/ ion-exchange techniques

Povećanje letalnog učinka bleomicina na stanice HeLa i V79 s pomoću pčelinjeg otrova

This study investigated possible growth-inhibiting effects of bee venom applied alone or in combination with a cytotoxic drug bleomycin on HeLa and V79 cells in vitro based on clone formation, cell counting, and apoptosis. Melittin, the key component of bee venom, is a potent inhibitor of calmodulin activity, and also a potent inhibitor cell growth and clonogenicity. Intracellular accumulation of melittin correlates with the cytotoxicity of antitumour agents. Previous studies indicated that some calcium antagonists and calmodulin inhibitors enhanced intracellular levels of antitumor agents by inhibiting their outward transport. In this study, treatment of exponentially growing HeLa and V79 cells with bleomycin caused a dose-dependent decrease in cell survival due to DNA damage. This lethal effect was potentiated by adding a non-lethal dose of the bee venom. By preventing repair of damaged DNA, bee venom inhibited recovery from potentially lethal damage induced by bleomycin in V79 and HeLa cells. Apoptosis, necrosis, and lysis were presumed as possible mechanisms by which bee venom inhibited growth and clonogenicity of V79 cells. HeLa cells, on the other hand, showed greater resistance to bee venom. Our findings suggest that bee venom might find a therapeutic use in enhancing cytotoxicity of antitumour agent bleomycin.U uvjetima in vitro istražen je inhibitorni učinak pčelinjeg otrova, samog ili združenog s citostatikom bleomicinom, na rast stanica HeLa i V79. Rabljene su sljedeće metode: brojenje stanica, metoda klonskog rasta i apoptoza. Poznato je da neki antagonisti kalcija i kalmodulinski inhibitori povisuju unutarstaničnu razinu protutumorskih lijekova inhibirajući njihov prijenos iz stanice. Unutarstanična akumulacija melitina izravno povećava citotoksični učinak protutumorskog lijeka. Obrada stanica HeLa i V79 u eksponencijalnoj fazi rasta bleomicinom uzrokuje oštećenje DNA ovisno o dozi te smanjenje broja živih stanica. Uočeno je da se letalni učinak bleomicina može pojačati dodatkom neletalne doze pčelinjeg otrova. Pčelinji otrov pritom inhibira popravak nastalih oštećenja u stanicama HeLa i V79 te sprječava oporavak stanica tretiranih bleomicinom. Apoptoza, nekroza i liza mogući su mehanizmi kojima pčelinji otrov inhibira rast i stvaranje kolonija stanica V79, dok HeLa-stanice pokazuju pojačanu otpornost na pčelinji otrov. Istraživanje također potvrđuje mogućnost uporabe pčelinjeg otrova u povećanju citotoksičnosti bleomicina