Reduced energy consumption and emissions by advanced process simulation

Eero Immonen

Process Flow


Rotary kilns are large pyroprocessing devices that are actively used in various branches of heavy industry. Typical applications include manufacturing of pigment and cement, lime calciner in the recovery cycle of chemicals in the pulping process, roasting of sulfide ores prior to metal extraction, to name but a few. These industrial processes are major consumers of energy and producers of carbon dioxide (CO2) emissions. Given the prevailing global focus on green technologies, reduction of emissions and on overall saving of energy, there is today a compelling need to optimize the use of rotary kilns.

Relevant and critical questions that need to be addressed in this context include:

  • How to optimally design the burner in order to maximize the efficiency and heat transfer to the bed within a rotary kiln?
  • How can one switch from using coal to, say, biofuels without compromising output product quality?
  • How to control the secondary air and fuel inlets to realize ideal combustion conditions?

Answering these questions requires a deep understanding of the operating characteristics of rotary kilns. Unfortunately, due to extreme environmental conditions, high temperatures, vibration and corrosion, it is very difficult to carry out direct measurements within a rotary kiln during its operation. Indeed, critical process information, such as combustion gas temperature, can often only be inferred through indirect measurements!
This issue renders the problem of optimizing a rotary kiln a very difficult problem.
This presentation outlines a simulation approach - a two-way connection of a kiln process model with full-scale 3D computational fluid dynamics - which has been successfully applied in the optimization of rotary kilns.