Composition analysis of minerals using non-invasive infrared thermography

Abstract

India is endowed with abundant resources of iron ore; however 60% of these are hematite. These hematitic ores are rich in iron but generally contain high alumina which reduces the productivity of blast furnace. The chemical analysis methods which are being used in bene-ficiation plants for determining the alumina content in these ores, are time consuming and cumbersome in nature. The present work describes an Infrared (IR) Thermography based fast and low cost technique for the compositional analysis of iron ores taking into account the change in average temperature due to the variation in thermal absorptivity of ore constituents. Iron ore samples from Noamundi mines of Tata Steel, with Fe contents ranging from 58 to 67 wt. %, were selected and crushed to around 10 mm particle size. A fixed quantity of these crushed iron ores were uniformly heated using a microwave oven, for a time period sufficient to create a difference between the ore particles in the extent of their respective infrared emis-sions. The thermal image of a fixed quantity of heated ore specimens is captured by IR Thermography and the average temperature of these ore specimens is evaluated from the thermal image. This experiment has been done with all variety of ores obtained from the be-neficiation circuit such as jig feed, jig concentrate, jig reject and classifier fines. A calibration curve between average temperature and the wt. % of alumina from chemical analysis of the ores is obtained. Finally, a software program has been developed in Labview for estimating the alumina content in a fixed quantity of iron ore specimens in order to determine the grade of the ores being sent from the mines to the steel plants. This technique of ore recognition can be useful in improving the feed quality of iron ore to the blast furnace, in iron and steel indus-tries by rejecting the alumina-rich ores. Indian coal industries mainly deals with bituminous and sub-bituminous coal in which the ash content varies from 25 to 75%. Quality of Coal (ash content in the coal) is one of the im-portant factors which directly affects the power generation in the thermal power plant and the efficiency of blast furnace in Steel Plants. High ash content reduces the thermal efficiency of the coal. The ash content interferes with the combustion of coal and reduces the temperature of the combustion zone. Therefore determination of ash content is of prime importance to find the suitability of specific coals for individual combustion systems. The ash content in coal is also being determined in this project using IR Thermography.