Estimation of calorific values of Turkish lignites

New formulae have been developed for estimating the calorific values of Turkish lignites from their proximate analyses data. In order to obtain these formulae, 24 Turkish lignites from different areas were analysed to obtain calorific values and proximate analyses. The data of another 26 Turkish lignites obtained from the literature were used to check the developed correlations. All the correlations were obtained using least squares regression analysis. The mean differences between observed and calculated calorific values using the formulae developed range from 3.78 to 7.56%.