Material composition and characteristics of bentonite clays used as a binder in the production of iron ore pellets

In the production of iron ore pellets, binding additives are used, in particular, bentonite clays. At present, instead of alkaline bentonite clays used before, the alkaline-earth bentonite clays modified by soda ash are used, supplied from abroad. There is a whole number of bentonite clays deposits in Russia and Ukraine having reserves of the raw material accounting hundreds of million tons, which are not used in the industry because of absence of planned and proper studies of their applicability for pellets production. The analysis of chemical composition carried out and requirements to rheological characteristics of bentonite clays used in the iron ore pellets production at steel-works of Russia and Ukraine determined. Indicators of swelling and water absorption of mono-ionic forms of bentonite of some deposits in water of various hardness presented. Quality of pellets with bentonites, having different exchange complex when using technical water of various hardness considered. Analysis of mineralogical and chemical compositions, as well as value and content of exchange complex of alkaline-earth bentonite clays of Cherkassk deposition, Ukraine, accomplished. The deposition has the largest reserves of such clays in CIS. It was shown, that clays suitable for pellets production, are located near the earth surface. Comparative analysis of strength indicators of pellets, produced with bentonite application with alkaline and alkaline-earth complexes, carried out. It was shown, that despite the low swelling of alkaline-earth bentonites, the quality of pellets, produced with those bentonites is sometimes a little lower, but under definite conditions does not yield to the quality of pellets with alkaline bentonites at the same their consumption.

The potential of using of alkaline earth bentonite clays of Ukraine in the production of iron ore pellets

Objective: to analyze and determine the potential of alkaline earth bentonite clays of Ukraine for use as a binder in the production of iron ore pellets. Methods: performing rheological studies of bentonite clay samples and their chemical analysis, electron microscopic studies of samples. Results: the analysis of the chemical composition and requirements for the rheological characteristics of bentonite clays used in the production of iron ore pellets at metallurgical enterprises of Russia and Ukraine is carried out. The swelling indicators and water absorption of monoionic forms of bentonites of some deposits in water of different hardness are given. The quality of pellets with bentonites, that have a different exchange complex, during an industrial water of various hardness usage is examined. The analysis of the mineralogical and chemical composition, as well as the size and composition of the exchange complex of alkaline-earth bentonite clays of the Cherkassk deposit (Ukraine), which has the largest reserves of such clays in the CIS is carried out. It is shown that clays suitable for the production of pellets are located near the surface of the earth. A comparative analysis of the strength characteristics of pellets using bentonites with an alkaline and alkaline-earth exchange complex is presented. Scientific novelty: it was shown that despite the low swelling of alkaline-earth bentonites, the quality of pellets with these bentonites, in some cases, is slightly lower, and in certain conditions is not inferior to the quality of pellets with alkaline bentonites at the same flow rate. Practical significance: for real industrial conditions it is shown that the increase in water hardness leads to partial or complete (depending on the value of hardness) replacement of alkaline exchange complex with alkaline earth and conversion of alkaline bentonite clay into alkaline earth with corresponding rheological characteristics, deterioration of lumps and the need to increase the content of bentonite in the charge. In the case of increased hardness of water in the concentrate, it is economically feasible to use in the production of alkaline earth pellets bentonite clay, if it is cheaper than alkaline.

Characterization of Some Vertisols of Different Agro-ecological Regions of India

Vertisols have the capacity to shrink and swell, inducing cracks and distinctive soil structure throughout the soil profile. In India they occur in various agro-ecological regions such as humid tropical (HT), sub-humid moist (SHM), sub-humid dry (SHD), semi-arid moist (SAM), semi-arid dry (SAD) and arid dry (AD) climatic environments and thus indicate an array of soils in a climosequence. In this study benchmark Vertisols, series Panjari is from sub-humid (dry), Kheriis from sub-humid (moist) region, Teligi and Akola series are from semi-arid (dry) and Nimone is from arid agro-ecological region. All the Vertisols in general are characterized by dark colour, angular to sub-angular blocky structure and clay in texture and calcareous. These soils have high bulk density and high water retention capacity. These soils have deep, wide-opened desiccation cracks at the surface which extend deep into the profiles and the depth of cracks increases with aridity. Soils of all climates are dominated by Ca2+ ion in their exchange complex throughout the depth. However, in the sub-humid climate Mg2+ ions tends to dominate in the lower horizon. Whereas the semi-arid dry (Akola) soils have high Na+ ions in their exchange complex. The soils are slightly alkaline to strongly alkaline in nature and poor in organic matter. The CEC varied from 59.3 to 68.2cmol (p+) kg-1 in soil of Panjari series which is highest followed by Teligi series profile. The calcium carbonate (CaCO3) shows gradual increase with depth in all the soil profiles, though it is preferentially accumulated in the sub-surface horizons of lower rainfall region soils.In climosequence the soils of the sub-humid region are generally Typic Haplusterts, soils of semi-arid region are Typic/Sodic/Calcic Haplusterts and soils of arid region are Sodic/ Calcic/ Aridic Haplusterts. The present study demonstrates how the soil properties of Vertisols in a different climate may help in inferring the change in climate in a geologic period.