Cement and Energy

) ENERGY CONSERVATION AT DURGAPUR CEMENT WORKS K.C. Jha, Durgapur Cement Works T he urge for energy conservation has been dominant in cement industry this decade owing to a severely competitive market among others. Accordingly all cement plants in the country took initiatives to reduce energy consumption and thereby the cost of cement I manufacture. Energy saving can be achieved broadly through : i) ii) Modernisation and upgradation of machinery and equipment, which requires substantial investment; and Using in-house expertise and constant efforts at : a. eliminating idle running of equipment, b. reducing frequent stoppages of equipment by strictly adhering to a Preventive Maintenance Schedule, c. identifying the scope of modification and implementation of the relative measures using internal resources, and d. operating equipment efficiently and optimally. Durgapur Cement Works (DCW) adopted such measures as above to achieve the goal of energy conservation. As a result, the slag dryer output increased from 80 tph to 125 tph, cement mill output from 25 tph to 32 tph and energy consumption came down from 82-84 kWh/t of cement to 66-68 kWh/t of cement. This article highlights the modifications made and the measures adopted, with their respective saving in energy consumption. Modernisation Slag Granulation Adoption of open drain for flow of recirculating water to reduce unproductive running hours of high pressure (HP) pumps and running of one HP pump instead of two, besides many other measures, cut down power consumption for slag granulation from 8.0 kWh/t to 5.5 kWh/t of slag. Slag Dryer The measures included in situ grinding of both the tyres and all four rollers, hot kiln alignment including roller slope adjustment, elimination of 3 belt conveyors, upgradation and centralisation of instrumentation and control system. Together, these brought down the energy consumption from 5.5 kWh/t to 4.0 kWh/t of dry slag. Ceme11t Mill Through installation of high efficiency separator and optimisation of 0- sepa separator, cement mills' output increased by 5-6 tph, cutting down power consumption by 10.0 kWh/t of cement. Previously cement mills were fed from table feeders owing to which feed regulation was not accurate and convenient. By replacing them with weigh feeders, monitoring of feed to mill became easy and effective. Earlier Fluxo pumps were being used for conveying cement to silo. Since their capacity did not match with that of the mills, i.e. 1 l/2 mills run per Fluxo, running 1 or 2 mills entailed wastage of energy. Therefore Fluxo pumps were replaced with dense phase (PD) pumps and dedicated to each mill. This resulted in a saving of about 2.0 kWh/t of cement. Conventional partition diaphragms were replaced with flow control diaphragms to increase grinding efficiency of mills. For better control and monitoring of cement mills, all drive switches were brought under central control room. Also cement mill control was changed to PLC with colour VDU which resulted in efficient cement mill operation. Removal of dampers and installation of variable speed drive for high efficiency separator's recirculating fan resulted in saving in fan power. Start/stop of silo top bag dust collector (BDC) fan was shifted from packing plant to cement mill PD pump station. Idle running of silo top BDC fan, when mills are not running, was eliminated. 5