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Iron ore sintering

Characterization by calorimetry and thermal analysis

Journal of Thermal Analysis and Calorimetry
Authors:
Riham Morcos
and
Alexandra Navrotsky

Abstract  

Differential scanning and high temperature reaction calorimetry have been used to characterize a series of natural iron ore and flux samples commonly used during iron ore sintering. Most iron ore samples were shown to contain measurable quantities of goethite, with a characteristic dehydration peak in DSC and TG between 200 and 400°C. At higher temperatures, all samples decomposed to produce magnetite with an accompanying mass loss in the TG profile due to the evolution of oxygen. High temperature reaction calorimetry has been used to measure the heat of solution of the ore in the melt formed during iron ore sintering. The dehydration and calcination of iron ore and flux samples was also examined using high-temperature reaction calorimetry. The results support the DSC/TG findings.

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Abstract

The severe heating of soil during wildfires and prescribed burns may result in adverse effects on soil fertility due to organic matter loss. No rapid and reliable procedure exists to evaluate soil organic matter (SOM) losses due to heating. Enthalpy of SOM combustion correlates with organic matter content. Quartz is a ubiquitous mineral in soils and has a remarkably constant composition and reversible α–β phase transition at 575 °C. We suggest that SOM content in heated and unheated soils can be compared using the ratio of SOM combustion enthalpy on heating to the β–α quartz transition enthalpy measured on cooling of the same sample. This eliminates the need to dry and weigh the samples, making possible field applications of the proposed method. The feasibility of using the (ΔH comb SOM)/(ΔH β–α Qz) ratio was established with experiments on soil samples heated in the laboratory and the method was then used for evaluation of SOM loss on two pile burn sites at UC Berkeley's Blodgett Forest Research Station in Georgetown, California.

Open access
Journal of Thermal Analysis and Calorimetry
Authors:
M. Donaldson
,
Rebecca Stevens
,
B. E. Lang
,
Juliana Boerio-Goates
,
B. F. Woodfielda
,
R. L. Putnam
, and
Alexandra Navrotsky

Summary As part of a larger study of the physical properties of potential ceramic hosts for nuclear wastes, we report the molar heat capacity of brannerite (UTi2O6) and its cerium analog (CeTi2O6) from 10 to 400 K using an adiabatic calorimeter. At 298.15 K the standard molar heat capacities are (179.46±0.18) J K-1 mol-1 for UTi2O6  and (172.78±0.17) J K-1 mol-1 for CeTi2O6. Entropies were calculated from smooth fits of the experimental data and were found to be (175.56±0.35) J K-1 mol-1 and (171.63±0.34) J K-1 mol-1 for UTi2O6 and CeTi2O6, respectively. Using these entropies and enthalpy of formation data reported in the literature, Gibb’s free energies of formation from the elements and constituent oxides were calculated. Standard free energies of formation from the elements are (-2814.7±5.6) kJ mol-1 for UTi2O6 and (-2786.3±5.6) kJ mol-1 for CeTi2O6. The free energy of formation from the oxides at T=298.15 K are (-5.31±0.01) kJ mol-1 and (15.88±0.03) kJ mol-1 for UTi2O6 and CeTi2O6, respectively.

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