CONDITIONS AND CHARACTERISTICS OF SHREDDED COAL IGNITION WITH LOCAL HEATING

Coals of several tens fields with different thermophysical and thermochemical characteristics are used in heat and power engineering of the Russian Federation. The powdered coal is used in the power engineering. Ignitions of the shredded coals in the conditions of their transport, storage, an overload or preparation for burning are possible generally at influence of local small-sized power sources (the particles heated till high temperatures, delays, an electric discharge, the surfaces heated to high temperatures). The main macroscopic regularities of ignition for condensed substances intended for combustion engines for special purposes are installed in the present time by the results of experimental and theoretical investigations of the basic laws. Processes of ignition are also enough of liquid fuels studied experimentally and theoretically. Results researches of conditions and characteristics for ignition of forest combustible materials and the dispersed wood are published. It isn't published yet any data on the ignition conditions and characteristics for dispersed coals. Therefore experimental investigations of the most typical representatives of groups the coals which are using in power system and other industries are expedient. The purpose of the real research — experimental investigation of ignition conditions and characteristics for shredded coals by local power sources — the single metal particles heated till high temperatures with small sizes. Experiments are made with shredded stone and brown coals. Deviations were supervised by the sizes of particles to 0,05–0,1 mm. The crushed coal was maintained in the dry room during 10–12 hours before experiences. Each experiment made in strictly controlled conditions. The possibility of repeatability the all executed experiments was provided. The initial temperature of a particle and ignition time delay were chosen as the main ignition characteristics. The given amount of the crushed coal of a certain field weight to 10 g placed in glass capacity when carrying out researches. Thickness of a layer for dispersed fuel was 2–3 of mm on the area no more than 10 cm2 . Steel particles in the form of a disk were used as heating sources. Value of ignition time delay was defined after video processing. It was the difference of times between contact of a steel particle with coal and emergence of a flame. The received results illustrate a community of ignition mechanisms for liquid fuels, forest combustible materials, dispersed wood, shredded coal which significantly differ according to the thermal characteristics. The received results allow to carry out an assessment of fire danger of solid fuels. This fact is a base for further improvement of the models which are use at creation techniques the forecast of fire danger processes, substances and materials.