Cement Energy and Environment

Advantages of Readive Belile Cement Adoption of this technology will provide manifold advantages:- 1. Energy saving on account of lower clinkering temperature. 11. Enlarging of the resource base of cement grade limestone in the country. 111. Extension oflife ofmines through use ofmarginal grade limestones. iv. Availability of a cement with lower heat ofhydration, whose use will ensure better durabilityofconstructions. v. vi. vii. ~cope for setting up cement rlanl! Da!ea on limestone resources ~iilierto considered lowgrade and unusable. Dispersal of cement industry away from the presently burgeoning 7clusters accounting for more than 56 per cent ofthe plants and 51 per cent ofthe total installed capacity. Which, in turn, will reduce the infrastructura~~ ·bottleneck caused by clustering of plants. Bringing cement manufacture nearer to the consuming centres in cement-deficit regions in the East, South and North. Jlignette USE OF WASTE DERIVED FUELS IN CEMENT MANUFACTURE · SOUTH ASIAN COUNTRIES' EXAMPLE 1 T he scope for use ofwaste derived fuels (WDF) in cement manufacture had been discussed in earlier issues. Such fuels, however, are generally used where availability of the conventional fuel is scarce. For instance, countries having no significant coal resources may fmd WDF an economic alternative. During the past few years, easy availability of cheaper imported coal from Australia, China, Indonesia and South Africa has completely changed the picture of fuel sourcing. In India, many plants located within an economic distance from ports are opting for imported coal of higher calorific value (6000 - 6500 kcaVkg) and low ash content (12-15%) in place of indigenous coal, because the cost of imported coal, as fired, works out much lower than indigenous coal. Some plants located much interior from ports resorted to blending of imported and indigenous coals in economic proportions. There are also many other direct and indirect advantages from use of high calorific value coal, e.g., better clinkerisation, smoother kiln running, increased lining life, lesser energy requirement in coal grinding, and scope of use of lower grade raw materials. Using WDF of high calorific value can offer the same advantage with environmental protection too. This is exemplified by the practice followed in some plants in Taiwan, 8 South Korea and Thailand, all ofwhich have no significant coal resource. These countries import coal from Australia, China and Indonesia at much lower cost i.e. US$ 30 - 35 per tonne CIF at plant in Taiwan than in India, yet, they opted for substitution of coal by WDF, such as pet coke or waste tyres. The calorific value ofpet coke is 7800 - 8000 kcaVkg and it is available at US$ 8 per tonne. Two plants of4.0 and 7.0 MTPA capacity in Korea use up to 10% pet coke. The last mentioned plant uses also 20% waste tyres of 6500 kcaVkg calorific value in the precalcinator. One 6.0 MTPA plant in Thailand uses up to 30% pet coke. The limitation in the use of pet coke is its high sulphur content ranging from 4 to 7% (SO 3 basis). Even with 30% substitution ofcoal by pet coke, the SO 3 content in clinker is kept within 0.4 to 0.5% by these plants while the specified limit is 0.6%. All the plants mentioned have developed ingenuous devices for collection, size reduction, handling and feeding ofthe wastes. It has also been ensured that use ofsuch wastesneither affects the quality ofclinker adversely, nor have they any pollutant effect in the stack effluents. Indian cement plants would do well to try such measures both for cost economy and also fo r contributing to environmental protection. t