Improvement of mechanical strength of iron ore pellets using raw and activated bentonites as binders

In this study, sodium, calcium, and mixed bentonite samples were used as binders in the pelletizing fine iron ore concentrate obtained from the Divrigi Iron Ore Concentration Plant in Turkey. In the pelletizing tests, sodium bentonite sample was used as received and after upgrading process. Additionally, the calcium bentonite sample required activation by sodium bicarbonate while the mixed bentonites sample was used untreated and as well as activated. The pellets produced were tested for compressive strengths, drop number, and porosity in order to characterize the pellets. The results showed that untreated and upgraded sodium bentonite samples provided relatively stronger pellets compared to calcium and the mixed type bentonite samples needed activation with sodium bicarbonate to increase the strength of the pellets. Based on the results of the drop number, compressive strengths, and porosity, it is possible to make pellets which meet the standards by adequate addition of type and amount of bentonite

Simultaneous purification and modification process for organobentonite production

Bentonites are commonly subjected to a water and energy intensive purification process in order to obtain high-grade montmorillonite, prior to modification to suit technological needs. In this study, the purification and modification processes were combined in order to minimize costs. A method for the production of organobentonite from roughly purified Na-bentonite from Resadiye, Turkey, was proposed with a quaternary alkylammonium salt hexadecyl trimethyl ammonium bromide. Further purification and ion exchange reactions were simultaneous within a centrifugal separation process, followed by the removal of excess modifier agent using the flotation method. The parameters of centrifugal force, feed solid content for Falcon concentrator and modification time, and the amount of alcohol for ion exchange reactions were optimized. Ammonium intercalated organoclays were characterized by X-ray diffraction analysis, thermogravimetric analysis, and swelling tests in organic liquids. An optimum flow sheet for the simultaneous purification and modification process yielding a 97% pure organobentonite with a 2.02 nm basal spacing was developed. (C) 2014 Elsevier B.V. All rights reserved

Rheological, Electrokinetic, and Morphological Characterization of Alginate-Bentonite Biocomposites

We prepared biocomposite gel dispersions involving sodium alginate (Na-Alg) and calcium bentonite (Ca-B) with various solid concentrations and characterized their rheological, electrokinetic, and morphological properties. The flow properties, such as the apparent and plastic viscosities, shear stress, and yield value point, changed with increasing clay dosage. The viscosities of the homogeneous dispersions were represented by the Herschel-Bulkley model. The zeta-potential results were examined in the light of different characterization methods (X-ray diffraction, Fourier transform infrared spectroscopy, and atomic force microscopy) to understand the interactions between the Na and Ca ions of the alginate biopolymer and bentonite clay. A plausible structural model for the alginate-bentonite composite gel, known as the egg-box model, is proposed. The presence of Ca ions in the Ca-B partially crosslinked Na-Alg may be regarded as an excellent example of a self-assembling process. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: 19-28, 201

Analysis of cyclic combustion of the coal-water suspension

Combustion technology of the coal-water suspension creates a number of new possibilities to organize the combustion process fulfilling contemporary requirements, e.g. in the environment protection. Therefore the in-depth analysis is necessary to examine the technical application of coal as a fuel in the form of suspension. The research undertakes the complex investigations of the continuous coal-water suspension as well as cyclic combustion. The cyclic nature of fuel combustion results from the movement of the loose material in the flow contour of the circulating fluidized bed (CFB): combustion chamber, cyclone and downcomer. The experimental results proved that the cyclic change of oxygen concentration around fuel, led to the vital change of both combustion mechanisms and combustion kinetics. The mathematical model of the process of fuel combustion has been presented. Its original concept is based on the allowance for cyclic changes of concentrations of oxygen around the fuel. It enables the prognosis for change of the surface and the centre temperatures as well as mass loss of the fuel during combustion in air, in the fluidized bed and during the cyclic combustion