Thermal Plasma in a Rotary Kiln for Cement Production: An Investigation of the Heat Transfer Mechanisms

Abstract

Due to the urgent global climate challenges, goals have been set by governments and companies in order to reduce their greenhouse gas emissions and their impacts on the climate. This master thesis work examines how the emissions can be reduced for the cement industry, by replacing the heat source in the rotary kiln from fossil fuels with an electrically generated plasma. The possibility of switching the heat source is studied through simulations, in Matlab, using a model which has been previously developed at the division of Energy Technology at Chalmers University of Technology. The main focus of this thesis is to examine how the heat transfer is affected from using a thermal plasma in the rotary kiln, and to compare the results to a coal flame. The thesis will also focus on examining how the desired product temperatures for the bed material is reached within the rotary kiln. Moreover, how the heat transfer is affected by varying certain process parameters as well as a sensitivity analysis, to investigate the effects of uncertainties, will also be assessed in the thesis. The simulations indicate a good potential for the implementation of a thermal plasma in the rotary kiln. Increased temperatures in the plasma and the addition of particles to the kiln, showed the biggest impact on the bed temperature, while simultaneously keeping a smooth bed temperature profile. To improve the simulations and make them more trustworthy, measurements on pilot scaled or full scaled kilns would provide valuable insight. For example, if measurements were to be made on the temperature profile of the plasma, which have been estimated in the simulations in this thesis work, more accurate simulations could be obtained.