Cement and Energy

separator with speciall y developed rotor internals. The mode of operation of a separator is characterised by the behaviour of the selectivity as a function of the particle size (separation curve). The selectivity is taken to mean ;he fraction of the separator feed material of a certain parti cle size which, as a result of the separation process, passes into the separator tailings and is returned to the mill. Th e more eiTective screening of the fines from the ground material leads to a higher throughput of the grinding plant, especially when producing finer cements. However, a rotor separator usually has a greater sharpness of separation than a circulating air separator; this is characterised by the ratio of the particle sizes with selecti vi ties of 25% and 75% on the so-called reduced separati on curve, and reduces the throughput again to some extent. Courtesy : lnrernational Cement Review, Jan. 1998. ' Although the mass-related energy consumption of the rotor separator by itself is significantly greater than that of the conventional circulating air separator, it is possible to save 2 to 30% of the total power demand by replacing mechanical air separators with modern cyclone circul ating air separators with rotor internals. This is in addition to optimising the ball mill to suit the type of cement and the current optimisation potential of the complete plant. However, these contributions to energy saving, which are sometimes quite high, can only be achieved if, in addition to replacing the separator, the operation of the ball mill is also adapted to suit the mode of operation of the new separator. However, the more selective mode of operation of the rotor separator can also have a detrimental effect on the particle size distribution and therefore on the properties of the cement. It is therefore only permissible to save energy where it does not impair cement quality. CENTRE FOR CLEANER TECHNOLOGIES T he Ministry of Environment and Forests is planning to set up an Indian Centre for Promotion of Cleaner Technologies. The centre would identify state-of-the-art technologies in different sectors of development available al l over the world and promote thei r adoption. Dr. S. Maudgal , senior adviser, Ministry of Environment and Forests told that energy and industry will be taken up as the two sectors by this Centre at the outset. In the energy sector. the major emphasis will be on thermal , hyde! and energy conservation. In industry, th e sectors which have been chosen are, textil es, fertilisers, cement, steel , automobolies and mining. To take help from the existing infrastructure a network of 24 insti tutions is being involved in the whole project. Centres would thus be spread out and functi on from these institutions. The network will play a catalytic role in demonstrating th at adoption of cleaner technologies is necessarily cost eflectivc and environmentally compatible, with the result that our enterprises can become competiti ve in the international market. The entrepreneurs arc conscious of hetter technologies but many do not have experience of technology scann ing, technology forecast and technology eva luation for making jud icious selection of technology for procurement. The proposed centre will help entrepreneurs to get information evaluated on available technologies based on which they can choose cleaner technologies within their means. The Director of National Environmental Engineering Research Institute (NEERI) Nagpur, will be· the Executive Director of the proposed centre and NEERI will act as co-ordinating agency for the cen tre. The energy sector will be headed by the Director of Tata Energy Research Institute, Delhi and the industry sector wi ll be headed by the adviser on Environment, Confederation of Indian Industry. Both Industry Sectoral Centre and Energy Sectoral Centre will have five sub-centres and five user centres attached. The National Thermal Power Corporation, Central Mine Planning and Design Institute, Gas Authority of India Limited, Calcutta Electricity Supply Undertaking and Indian Renewable Ener·gy Development Agency Ltd. will be the sub-centres attached to the Energy Sectoral Centre. Its user centres will be Central Fuel Research Institute, Central Pol lution Control Board, Ncyveli Lignite Corporat ion, Bharat Heavy Electricals Ltd ., and Orissa State Electricity Board. 14