Fluidization of Fine Calciner Raw Meal Particles by mixing with coarser Inert Particles – Experiments and CPFD Simulations

Abstract

The calciner has a significant role in the production of cement. It is the most energy-intensive process unit in the production process. Most modern calciners are entrainment-based, i.e., a hot gas pneumatically conveys the particles through the calciner. A fluidized bed is an alternative to the entrainment calciner, which may be of special interest if the calcination process is to be electrified, so that the raw meal is mainly calcined by heat transfer from a hot surface and not by direct contact with hot combustion gases. The fine particle size of the raw meal, however, makes it a challenge to fluidize. This study looks into an alternative solution in which the cement raw meal is mixed with coarse sand particles to enhance the fluidization behavior. Experiments are first conducted to fluidize pure cement raw meal (fine particles) and sand (coarse particles) separately. Then they are mixed at fine/coarse mass ratios of 25%/75% and 50%/50%. Simulations are then performed, using a commercial CPFD software (Barracuda ®, version 20.0.0), to replicate the results from the experiments. The experimental results indicate that it is technically feasible to fluidize cement raw meal by mixing it with coarse inert particles at the mentioned fine/coarse mass ratios. Stable fluidization was observed at a superficial gas velocity of 0.3 m/s. The pressure drop results from simulations and experiments matched quite well at both mixing ratios. Hence, the CPFD simulations may be used as an aid in the design of a potential full-scale calciner applying this concept.