Modelled fate of sulphur and chlorine in rotary lime kilns | Part I: Chemical equilibria prevailing in the kilns

Investigations performed to predict the SO₂ and HCl emissions of rotary kilns have shown that Investigation performed to predict the SO₂ and HCI emissions of rotary kilns have shown that the chemical reactions needed to assess these emissions also enable quantification of the generation rate of build-ups in the preheating zone of these kilns. As anticipated by the theory and confirmed by industrial tests, sulphur and chlorine loops were found. The chlorine loop is closely interconnected to the sulphur loop that is itself influenced by the process conditions prevailing in the kilns. The quantification of the thus resulting emissions and generation of build-ups requires a precise assessment of all reactions involving sulphur and chlorine. However the first results of the modelling showed only a fair agreement between calculations and monitoring results. Further investigations were therefore carried out. Accordingly it was found that potassium plays a key role in the chemical reactions occurring in rotary lime kilns. The inclusion of this element in the modelling enabled a significant increase in the accuracy of the prediction. This paper presents the chemical reactions used in the model.