Modeling of Rotary Cement Kilns:  Applications to Reduction in Energy Consumption

Abstract

Rotary cement kilns are used for converting calcineous raw meal into cement clinkers. In this paper, we discuss and evaluate possible ways of reducing energy consumption in rotary cement kilns. A comprehensive one-dimensional model was developed to simulate complex processes occurring in rotary cement kilns. A modeling strategy comprising three submodels, viz. a model for simulating the variation of bed height in the kiln, a model for simulating reactions and heat transfer in the bed region, and a model for simulating coal combustion and heat transfer in the freeboard region, was developed. Melting and formation of coating within the kiln were accounted for. Combustion of coal in the freeboard region was modeled by accounting for devolatilization, finite-rate gas-phase combustion, and char reaction. The simulated results were validated with the available data from three industrial kilns. The model was then used to understand the influence of various design and operating parameters on kiln performance. Several ways of reducing energy consumption in kilns were then computationally investigated. The model was also used to propose and to evaluate a practical solution of using a secondary shell to reduce energy consumption in rotary cement kilns. Simulation results indicate that varying kiln operating variables, viz. solid flow rate or RPM, can result only in small changes in kiln energetics. Use of a secondary shell over the kiln and energy recovery by passing air through the annular gap between the two appears to be a promising way to achieve significant energy savings. The developed model and the presented results will be useful for enhancing the performance of rotary cement kilns.

Method for processing coal-enrichment waste with solid and volatile fuel inclusions

“…It reduces underburning of solid-fuel inclusions. Furhermore, the metod increases heat of combustion of gaseous products [13,14]. The distribution of the process is limited to the waste of brown coal enrichment having a significant content of volatile substances in fuel inclusions and a high content of SiO 2 with a fine crystalline structure in the rock.…”

Numerical Simulation of Cement Kiln Combined with Thermal Plasma for SF6 Pyrolysis

“…The parameters G k and G b in Eqs. (9) and (10) are the kinetic energies generated due to the mean velocity gradients and buoyancy, respectively.…”

Modelling the cement process and cement clinker quality

“…Many of the works in the literature describe physical models that focus on flame characteristics, bed motion and heat transfer mechanisms. Some have used computational fluid dynamics (CFD) as the modelling tool (Mastorakos et al, 1999;Yuan et al, 2007) while mathematical equations of energy and mass conservation have been described and applied by others (Locher, 2002;Mujumdar et al, 2006). A chemical model has also been developed that focuses on the intrusion of alkali compounds in the ceramics in the kiln lining using non-equilibrium calculations (Emler, 2008).…”