Advanced Thermochemical Simulation of Rotary Kilns

Pertti Koukkari and Karri Penttilä



The technology of rotating drums for heating, drying and calcining has been available for over 100 years. In various industries rotary kilns are used for purposes ranging from drying to combustible incineration and mineral and metallurgical processing. In some traditional applications the conventional kiln operation has been replaced by e.g. fluidized beds or shaft furnaces, yet there remain a great number of processes, where the rotary kiln is further regarded as the best available technology (BAT). To maintain such position, both raw material and energy efficiency of the kilns are being constantly improved. As it remains tedious to obtain measured data from inside the rotating steel cylinders, improved simulation models has been developed for better understanding of the kiln operations. KilnSimu software uses a constrained free energy algorithm combining multiphase chemical changes with mass and heat transfer phenomena to simulate the complex thermochemical processes in both co-current and countercurrent rotary kilns.

KilnSimu calculation results are given as 1-dimensional (steady state) axial profiles in the longitudinal direction of the kiln. When combined with 3-D aerosol model the fluid dynamics of the flame and gas phase are included by use of KilnSimu results as boundary conditions.

Supported by KilnSimu calculations, remarkable improvements can be achieved in kiln fuel efficiency, in introducing alternative fuels and in eliminating harmful emissions or recursion reactions of non-process elements in the kiln. For over a decade, KilnSimu software has been used to simulate a large number of kilns with varying chemistry, the applications ranging from titania pigment calcination and zinc recycling to waste incineration and cement-making.