Cement, Energy and Environment

TECHNOLOGY TREND PNEUMATIC CONVEYING: OUTSIDE THE BOX Jim Ketcham, Cyclona ire Cotporation, USA, Anyone who has been involved in the design or selection of material handling systems for cemen t or flyash has faced the same decisions: mechanical or air conveying; screws and buckets o r blowers and ai rlocks; med ium or hi gh– pressure blow pots or possibly screw pumps? When comparing equipment prices, one should not forget to include maintenance costs when evaluating any conveyin g system. Whatever cho ices are made a re no doubt based on experience w ith similar equipment, knowledge of the app li ca ti on an d vendor recommendations. Material characteristics play an important role in what typ e of conveyor system to choose. Dry powders, granules, pellets and similar products arc good candidates for either mechanical or pneumatic systems. Mechanica l conveyors work well for conveying high volumes of material over a short distance to a single des tination. Screws, buckets and belts mechanical system and can easily accommodate changes in d irection, long conveying distance and multiple ma terial destinations. Cement, a fine powder that fluidi ses easily and retains aeration, is our friend from a pneumatic conveying s tandpoint. This means that when air is introduced into the material, it behaves more like a liquid than a solid. When it is in this fluidised state, it can be pumped w ith air and w ill flow through the conveying piping. The concrete indus try as a wh ole has used one of two basic pneumatic conveying principles through the years, dilute phase or dense phase. The terms ' dilute' an d ' dense' refer to the amount of material in a cross-section of the conveyor line while being conveyed, and are based on different concepts of air velocity and pressure. Both applied in various applications for cement and flyash and bringwith them their set of advantages and disadvantages. Courtesy: World Cement, Ma r. 2002, Pp. 68-74, Enquiry n o. 8. Email: mail@worldcement. com Web: www. worldcement. com arenotnecessarilydesigned tobe leak free,and ACC BUILDS THE BIGGEST KILN IN material may migrate out onto the ground and INDIA surrounding equipment. A pneumabc sys tem may afford the best solution for unloading cement or flyash from hopper-bottom railcars or trucks and conveying the material over a long distance to multiple storage sil os. For this type of application, the mechanical conveying system would be quite complex, as well as expensive to purchase, install and maintain. The pneumatic system is cleaner, requ ires less ma inten ance than In April las t year, when the Associated Cement Companies Limited (ACC) lit the fl ame at their new Green-field plant in Wadi, they n ot only became India's largest cement producer, but also started up what is eventually to become the world's largest kiln systemw ith a daily capacity of 12,000 tonnes. Back in 1996, ACC contacted FL. Smith and its long standing partner Larsen & Toubro (L&T) r .r- 1