Characterization of the Properties of Non–Coking Coals and their CHARS

Abstract

India has fifth largest coal reserve in the world but has a very limited reserve of coking coal which is the key material for the production of steel. Coking coal accounts for only 15% of the total reserve of India while non-coking coal accounts for 85%. Since India has an abundance of non-coking coal and scarcity of coking coal, there is a need to maximize the utilization of non-coking coal in various sectors such as power generation, steel industry, and cement industry. The current project has been taken up to contribute towards the potential growth of non-coking coal and their utilization in the steel sector in sponge iron making process. Non-coking coal is exploited in sponge iron making through direct reduction of iron ore commonly known as DRI method. In the present project work different non-coking coal samples obtained from various coal mines of India namely South East Coalfields Limited (Chhattisgarh), Jindal coalfield (Chhattisgarh), Mahanadi Coalfields Limited Basundhara (Orissa), Gopalpur (Chattisgarh) and Asansol and Lingaraj coal mines. The project was undertaken with the following objectives: (i) Characterization of the selected coals for their chemical and physical properties, (ii) preparation of coal chars, and (iii) characterization of the chemical and physical properties of these coal chars. The coal and char samples were characterized for chemical properties (proximate analysis and ultimate analysis, calorific value) and physical properties (apparent porosity and density, caking index). The result was found that Basundhara (MCL) coals have highest fixed carbon content and calorific value. The reactivity of char produced at carbonization temperature 950°C towards carbon dioxide was measured, and value was found greater than 2gm/cc/sec which is desired in sponge iron plant. Effect of carbonization at different temperature (400°C, 600°C, 800°C and 950°C) on properties of coal char was investigated, and it was found that energy value and fixed carbon content and apparent density increases, whereas porosity decreases with the increase in carbonization temperature. Ash fusion temperature of some of the coal ashes was determined and found that these coal ashes have sufficient high ash fusion temperature to avoid ring formation. Results obtained from all the experiments conclude that most of the selected coals are suitable for sponge iron making.