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The article presents the results of experimental and theoretical studies of the ignition processes of coal- water fuel (CWF) drops made from coals of various degrees of metamorphism and coal semi-coke of these coals. It is shown that the preliminary torrefaction of coal leads to a significant improvement in environmental performance (50–60% reduction in flue gas concentrations of the main anthropogenic coal combustion products: nitrogen oxides NOx and sulfur SOx) of coal- water fuel combustion processes. This effect is most pronounced during the combustion of CWF based on lignite. Also, according to the results of the experiments, the ignition delay times of typical droplets (in the initial state), and then particles (after drying the near-surface fuel layer) of coal- water fuel s based on coals and coal semi-coke were established. It has been established that the ignition delay times of coal- water fuel particles based on pre-torrefied coals at relatively low ambient temperatures (Tg?873 K) are on average 20% higher than when igniting CWF droplets based on natural coal. Under conditions of high-temperature heating, the ignition delay times of CWF particles made from natural coal and semi-coke differ insignificantly (no more than 2%). Based on the results of the experimental studies, a mathematical model of the ignition process of a coal- water fuel drop based on semi-coke was developed, which differs from the known ones in a relatively simple description of the most significant processes of thermal preparation and ignition, but at the same time retains a fairly high predictive potential. Using the previously developed method of quasi-stationary "thermal approximation" with the selection of an asymptotic estimate, an analytical solution is derived for the essentially nonlinear problem of coal- water fuel droplet ignition.