Thermochemical Simulation, Thermogravimetry and Roasting Studies for Selective Sulfation of Copper in Flash Smelter Dust.

The thermal studies are a useful tool to understand the conversion of chalcopyrite to copper sulfate. We carried out thermochemical simulation in combination with thermogravimetric studies to understand the sulfation behavior of copper and iron in a copper smelter dust sample and to predict suitable roasting condition. Different oxide and sulfate phases of Cu and Fe forms as function of temperature. A temperature range of 150-1000°C was applied; however, a 550-650°C was found suitable for selective sulfation of copper. Further tests in a tube furnace at 600°C for three hours ensured 96% Cu sulfation and only 2.1% Fe sulfation

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

A hybrid memory kernel approach for condensed phase non-adiabatic dynamics

The spin-boson model is a simplified Hamiltonian often used to study non-adiabatic dynamics in large condensed phase systems, even though it has not been solved in a fully analytic fashion. Herein, we present an exact analytic expression for the dynamics of the spin-boson model in the infinitely slow bath limit and generalize it to approximate dynamics for faster baths. We achieve the latter by developing a hybrid approach that combines the exact slow-bath result with the popular NIBA method to generate a memory kernel that is formally exact to second order in the diabatic coupling but also contains higher-order contributions approximated from the second order term alone. This kernel has the same computational complexity as NIBA, but is found to yield dramatically superior dynamics in regimes where NIBA breaks down---such as systems with large diabatic coupling or energy bias. This indicates that this hybrid approach could be used to cheaply incorporate higher order effects into second order methods, and could potentially be generalized to develop alternate kernel resummation schemes

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

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

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