Calcination Of Minerals Research Articles

DEM/CFD Simulation in Process Engineering

Thermal and chemical treatment of bulk solids and particle systems is a basic unit operation in many industrial sectors. The purpose of the treatment can be either to achieve well-defined product properties or to use solids in gasification processes to produce syngas, synthetic fuels, or to recycle waste products. Typical examples are the calcination of minerals as dolomite or magnesite in the basic materials industry, the direct iron ore reduction with hydrogen in steel industry, coffee bean roasting in the food processing industry, or catalytic reactors and fluidized bed spray coating of tablets in the chemical and medical industries, respectively. Many of these processes are operated at high temperatures and are, therefore, energy-intensive and often associated with high CO2 emissions; a careful layout of the systems is needed. Furthermore, target properties of the solids must be achieved concerning reactivity, specific surface area, calcination or roasting degree, etc. To meet all these challenges and requirements, a detailed knowledge of the underlying physical and chemical processes is needed for predictive design. Fundamental studies are first necessary to understand the properties of particulate flows, e.g., regarding turbulence modulation, collisions between particles and/or with surfaces, and particle dispersion, before going toward practical applications. Typical systems are highly loaded with particles, often passed by a reactive gas flow, and are operated at high temperatures. Therefore, measurements are very challenging in such systems. Hence, appropriate simulation methods are needed to support system and reactor layout. Such a method combines the discrete element method (DEM) with computational fluid dynamics (CFD). DEM/CFD allows to track individual particles and their interactions with other particles, surrounding walls, and the gas phase in-between the particles. Conversion of the particles including intra-particle processes can be described as well as size change or development of adhesive forces associated with the thermal treatment. The current focus issue of Chemical Engineering & Technology entitled “DEM/CFD Simulation in Process Engineering” gives a status on the description of particulate flows with a focus on reactive particle-gas systems using DEM/CFD and presents illustrative examples of its application. A review article on DEM/CFD for reacting systems sets the frame for the further contributions that concentrate on fundamental aspects, specific examples, and important methodological developments. Examples presented are shaft kilns (production of quicklime/production of spinel), waste incineration, combustion of wood pellets, and carbonate looping processes. Novel trends as the usage of machine learning in combination with DEM/CFD, the combination of resolved and unresolved DEM/CFD in one simulation domain, and new approaches regarding the immersed boundary method to describe particle-gas systems are presented. The contributions do not claim to cover all relevant aspects needed for DEM/CFD simulations of reactive particle-gas systems but can be seen as a first overview and starting point for interested readers. This focus issue and the corresponding workshop at the Conference on Modelling Fluid Flow in Budapest 2022 have been organized by the Collaborative Research Centre BULK-REACTION financed by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Project-ID 422037413 – TRR 287. Prof. Dr.-Ing. Viktor Scherer Ruhr-Universität Bochum, Faculty of Mechanical Engineering, Department of Energy Plant Technology Prof. Dr.-Ing. Dominique Thévenin Otto von Guericke University Magdeburg, The Laboratory of Fluid Dynamics and Technical Flows Viktor Scherer Dominique Thévenin

Identity of certain species of plants of unknown source from Rasendramangala

Combination of plant and mineral products were derived in the process of exploring safe and effective remedies which can cure severe and deadly diseases. Some plants are used for processing, purification and calcination of minerals, metals and gems. Mainly the purpose of plants in Rasa shastra is to obtain absorbable metallic molecules in the maximum possible minute form. But some plants mentioned in textbook of Rasa-shastra are not identified properly, because Rasa siddhas like Nagarjuna and Rasa Vagbhata have used some rare synonyms of plants, to conceal them from the knowledge of unknown and mischievous personalities, to avoid misuse. But at present, it is necessary to identify them properly, to use the plants for exact calcination and purification for the benefit of mankind. In the present study, nearly ten plants out of 47 unidentified plants are selected from Rasendra Mangala written by Acharya Nagarjuna in the period of 7th and 8th Century A.D. and a trial has been made to work out on such unidentified plants depending upon their synonyms, utility and combination with other drugs. To quote some, Kanchuki, Chandali, Choraka, Chandravalli and Sarpakshi.

Factors Influencing CO2 and Energy Penalties of CO2 Mineralization Processes.

Carbon mineralization is one of the carbon capture utilization, and storage (CCUS) technologies that can be used to capture large quantities of CO2 and convert it into stable carbonate products that can be stored easily. Several CO2 mineralization processes have been proposed; however, there are no commercial-scale projects because there are still significant issues that need to be improved before commercialization can take place. In this work, we evaluate the CO2 and energy penalties related to the most well-known types of mineralization processes developed to date, in which the mineralization reaction takes place directly under aqueous conditions, high pressures and temperatures, and compared these with newer T-P swing processes and ball-mill reactor processes, which are under development. The data used in the evaluation are taken from published literature. By comparing the three processes, we identify important variables that contribute to high CO2 and energy penalties so that future research can focus on optimization of these variables. It is observed that slurry concentration (heating) and particle size (grinding) are critical factors, with mineral calcination and operating pressure constituting other important factors.

Adsorption of 99TcO4 − onto hydrotalcite and calcined hydrotalcite under basic conditions: influence of humic acids and anions

The remediation of technetium-99 (99Tc) at contaminated sites remains a major challenge, as Tc high solubility and anionic nature under oxic conditions lead to high contaminant mobility. Hydrotalcite, a form of anionic clay, can strongly retain anions, especially upon mineral calcination. However, naturally occurring humic acids can also sorb onto hydrotalcite, therefore competing with TcO4− for sorption sites. This work explores the ability of hydrotalcite to retain TcO4− in presence of humic substances to evaluate the efficacy of hydrotalcite for Tc remediation in natural environment. Results show that calcined hydrotalcite can immobilize TcO4−, while the presence of 23 ppm humic acids has little influence on TcO4− uptake. However, additional monatomic and polyatomic anions in solution can compete with TcO4− for sorption sites on hydrotalcite.

Preparação de mulita a partir do mineral topázio

Mulita é o único composto termodinamicamente estável no sistema binário Al2O3 - SiO2, na faixa 70,5 a 74,0% em peso de Al2O3. Mulita metaestável na faixa de 74 a 83,6% de Al2O3, entretanto, pode ser obtida. Devido às suas excelentes propriedades físicas e mecânicas a altas temperaturas, como alto ponto de fusão, baixa expansão térmica, boa resistência à fratura e ao choque térmico, alta resistência à fluência, estabilidade térmica, baixa densidade e baixa constante dielétrica, tem tido um uso cada vez maior em corpos cerâmicos. O mineral mulita, porém, é raro e quase inexistente na natureza. Para atender a um mercado crescente, mulitas sintéticas são produzidas, por meio de misturas de pós de Al2O3 e SiO2 em escala molecular, usando técnica sol-gel, ou por meio da calcinação de minerais que contenham sílica e alumina em suas estruturas, os chamados alumino-silicatos. Normalmente estes minerais contêm impurezas e, muitas vezes, produzem uma mulita acompanhada de uma fase vítrea. Neste trabalho é feito o estudo alternativo para se obter uma mulita pura e de baixo custo por meio da calcinação do topázio Al2SiO4[Fx (OH)1-x]2. Topázio incolor e imperial foram utilizados para a produção de mulita. O topázio incolor não tem valor gemológico nem comercial e é abundante na natureza. Para o topázio imperial foram usados refugos provenientes de sua extração. O rendimento da calcinação foi alto, cerca de 80%, obtido a uma temperatura não muito alta, em torno de 1300 ºC, produzindo uma mulita muito pura e sem fase vítrea. A microestrutura da mulita obtida foi do tipo agulhas (whiskers de mulita) e apresentou alta porosidade. Essa microestrutura e porosidade são duas propriedades intrínsecas que estão associadas à decomposição do topázio. Este estudo mostrou que o topázio é uma fonte alternativa para a produção de mulita de baixo custo e de alta qualidade.

Venezuelan natural alumosilicates as a feedstock in the synthesis of zeolite A

Zeolite A has been synthesized from low-cost natural aluminosilicates. The samples were characterized by X-ray powder diffraction, chemical analysis, electron microscopy, FTi.r. spectroscopy, and nitrogen adsorption. Studies of calcination temperature effects and Na 2O SiO 2 and H 2O Na 2O ratios were performed. It was observed that mineral calcination at temperatures in the range of 500–850°C led to zeolite A formation, but when the calcination step was omitted, hydroxysodalite was formed. In samples calcined for 5 h at temperatures higher than 850°C, no zeolite was observed. A maximum in crystallinity was obtained for samples calcined in the range 700–750°C. The zeolite crystal mean size increased as the alkalinity increased. I.r. spectroscopy was used to characterize the products. An area band ratio at 570 and 470 cm −1 showed a linear correlation with % crystallinity determined by XRD.