Investigation of the Behavior of Alkali Chlorides during Sulfur Recirculation in a Waste-to-Energy Facility

High temperature corrosion related issues are known problems for Waste-to-Energy facilities where the formation of alkali chlorides is among the most problematic species formed during the combustion. Sulfur Recirculation is a novel technology developed to reduce the chlorine content in the ash and in that way also the corrosivity of the ash. This concept has been installed at the Maabjerg Energy Center (MEC) in Denmark. This work aims to take a first step towards a reaction kinetics based model that can describe systems like the MEC boiler and to evaluate the impact of Sulfur Recirculation. This is done by implementing a plug flow reactor model in the software Chemkin. Previously obtained data from on-site experiments and CFD simulations is used as input to the model. The model is focused on describing the sulfation of alkali chlorides and the result from the model is compared to experiments. The model is able to predict the degree of sulfation with less than 10% deviation from the experimental results. Both the experiment and the model show a clear benefit from implementing sulfur recirculation which lowers the chlorine content in the up to as much as 70%. It is, however, also shown that the results are sensitive towards several of the assumptions made. Even though there is a relatively good agreement in final sulfation between model and experiments the model is not able to represent the detailed chemistry in a realistic way in its current state; further development is required