Cement and Energy

serve as a model. The successful demonstration of the technology in a participating planr will pave the way for its replication in large capacity plants of 3000 tpd and above, numbering about 40 at present. The funds for such demon– stration project may be available from Internatio nal Agencies like GEF, etc. A meeting of representatives of NCB, CMA Courtesy : National Councilfor Cement and Building Materials (NCB) and various cement companies was held at UNDP, New Delhi on 17th November 1997 wi th officials ofGEF wherein it was agreed that a project pro posal on "cogeneration of power utilising waste heat" may be prepared and submitted to GEF for its consideration. COMBUSTIBLE WASTES AS SOURCE OF ENERGY F uel energy cost alone accounts for more than 25% of the total cement manufacturing cost. Further, due to increase in the prices of coal and its movement over long distances to cement plants in some parts o f the country, the landed cost of coal becomes high resulting in high cost of energy input in cement manufacture. These have necessitated a search for locall y available combustible wastes to be used as partial substitu te of coal. In India, agro-based industries generate nearly 250 million tonnes of combustible wastes . The wastes are widely spread over the country and depending upon logistics, these are considered to be potential cost-effective energy source. Com,bustible wastes may broadly be classified as agricultural wastes, industrial wastes and synthetic wastes. Factors like availabiu ty, cost, charactetistics, ignition and combustion aspects, storage, handling, feeding and firing system, impact on kiln ope ration and clinker quality, environmental and social considerations need to be considered for the suitability of combustible wastes in cement manufacture. A few cement plants in Japan have substituted 25% of their the rmal ene rgy requirements by scrap moto r tyres. In Germany, combustible wastes like rice husk, bamboo/saw dust, waste o il, etc. have been used in the precalci nator replacing coal up to 30%. Organic materials including waste oi Is, solvents from paint industries, aromatic so lvents, etc., were used as energy source in Norway which showed good results of incineration with high destruction efficiency. ln France, the combustible wastes are reported to have replaced the main fuel by 25%. Out of the various combustible wastes, rice husk. bamboo dust, bagasse, carbon slurry, etc., seem to have good potential in India. Though some of the combustible wastes have calorific value even less than 4000 kcaVkg. , they can be effectively utilised along with coal. Various o ptio ns have been cons ide red for feeding of combustible wastes . These are : Intergrioding of wastes in predetermined proporiion along wi th lump coal and then feeding the mixed fue l to kiln and/or precalcinator. Mix ing the wastes along with pulverised coal and then feeding the mixed fuel to precalcinator and/or kiln. Separately feeding the wastes and fine coal in the desired proportion to kiln or precalcinator or both. 4