Hydrodynamic and Heat Transfer Studies in Riser System for Waste Heat Recovery using Chalcopyrite

Energy, a critical input, is to be efficiently managed via waste heat recovery and energy reuse for the economic viability of a process industry. In particular, cement manufacture demands a huge quantum of energy, for the necessary reactions. Huge amounts of hot effluent gases are generated. Energy recovery from these waste gases is an area that is of contemporary research interest. Now, about 75% of total heat recovery takes place in the riser of the suspension pre-heater system. This article deals with the hydrodynamic and heat transfer aspects of riser typically used in the cement industry. An experimental apparatus was designed and fabricated with provision for the measurement of gas pressure and solid temperatures at different heights of the riser. The system studied was air - chalcopyrite taken in different particle sizes. Acceleration length (L-A) determined at different parametric levels was fitted to an empirical correlation: L-A/d(t) = 4.91902(d(p)/d(t))(0.10058)(w(s)/w(g))(-0.11691)(u(g)mu(g)/d(t)(2)g rho(g))(0.28574)(rho(p)/rho(g))(0.42484). An empirical model was developed for Nusselt number as a function of Reynolds and Prandtl numbers using regression analysis: Nu = 0.40969 (Re-p)(0.99953 )(pr)(0.03569).