Experimental research of ignition and combustion processes of multi-component coal-water fuel droplets

A wide interest in coal-water suspensions in recent years is connected to the formation of significantly smaller volumes of sulfur, nitrogen and carbon oxides during their combustion in boiler furnaces in comparison with coal. One of the main problems hindering the widespread introduction of coal-water fuels in thermal power industry are large ignition delay times (up to 25-30 s). The aim of the work is experimental justification based on the results of studies of reduction possibility of ignition delay time of coal-water fuels due to addition of the second combustible component – isopropyl alcohol - in relatively small (from 3 to 5%) concentrations. Registration of heating, ignition and combustion processes was performed using a high-speed video camera (up to 3600 frames per second). The studies were performed in a medium heated to high temperatures (from 873 K to 1273 K) of oxidizer (still air). It was discovered that increase in the concentration of isopropyl alcohol to 5% by weight leads to reduction of the ignition delay time of droplets (with characteristic size of 2.5 mm) of the studied suspension by 26% in comparison with traditional coal-water fuel. Conclusions about the influence of mass concentration of isopropyl alcohol in the composition of coal-water fuel on the characteristics of the initiation of ignition and combustion processes are presented.