In a quest for a cheaper alternative to coal, the National Council for Cement and Building Materials and Cement Manufacturers’ Association has decided to promote the use of petcoke in the cement industry after evaluating several international and domestic experiences. Petcoke is a by-product obtained during refining of heavy crude oil.
Petcoke is characterised as a high grade fuel with high calorific value of more than 8,000 Kcal per kg, having low ash content and low volatile matter but high sulphur content, up to 7 per cent.
Petcoke provides scope for manufacturing higher grade of cement with the same raw material or same grade of cement using marginal and low grade limestone contributing to resource conservation. Due to higher calorific value compared to coal, less quantity of petcoke needs to be moved from source to plant site, which reduces the cost of transport. However, as the sulphur content in petcoke is high, its larger use increases the sulphur cycle and aggravates build-up formation in the kiln system. The total sulphur content in the clinker needs to be maintained below 2 per cent from product quality point of view. For promoting use of petcoke in the cement industry, there is, therefore, a need for changes in raw mix design and finess of fuel and modifications in burner, calciner and cooler so that a trouble-free and cost effective operation is achieved.
A study conducted by SK Walia and GS Rajawat in Lakshmi Cements have shown that fuel costs can be reduced by promoting the use of petcoke. Fuel alone accounts for about 40 per cent of the cost incurred by the cement industry.
Alternate fuels like petcoke can reduce fuel costs to a great extent. They have identified that ‘green delayed petcoke’ is suitable for use in calciner, fluid petcoke is suitable for use in burning zone and calciner.
They suggested that petcoke should be used when the plant is equipped with multi-chanel burner, when alkali deposits are high, when there is a margin in coal milling capacity and primary air fan quantity and when riser duct is fitted with coating repellent refactory.