The effect of coating layer formation on heat transfer conditions in a thermal plasma heated rotary kiln

Other conference contribution, 2025

Electrification of fossil-fuelled industries like the cement industry are essential for mitigating global warming. The most energy intensive steps of the cement process is the heat treatment of raw material, the calcination and formation of clinker, where the product bed reaches temperatures of up to 1450°C in a rotary kiln, traditionally through fossil fuel combustion. One promising option is to replace the fossil fuel using an electrically generated thermal plasma as the heat source in the kiln, utilising the carbon dioxide inherently formed from calcination as the working gas. In cement rotary kilns, a well-known phenomenon is the formation of insulating coating layers on the inner kiln wall, affecting the inner wall temperatures and heat transfer. Such layer formation have been extensively studied for combustion fired rotary kilns, while the formation using thermal plasma, is yet unexplored. To examine the effect from the coating layer on the heat transfer conditions within the kiln, detailed modelling work is required. 

Within this work, experimental data on a pilot-scale rotary kiln fired with either propane or operated using a thermal plasma is used to evaluate the insulating effect from the formation of a coating layer, using a 3D heat transfer model. Based on the modelling results, the impact of the coating in a plasma heated rotary kiln is estimated. The coating’s insulating effect is evaluated by matching modelled shell temperature with measurements while varying the thickness of the coating layer Further, experimental work on the plasma heated kiln is to be used for validation of the modelled results.