@IJMTER-2015, All rights Reserved 89 EFFECT OF PARTICLE-SIZE AND AIR FLOW RATES ON THE IGNITION TEMPERATURE OF SUB-BITUMINOUS COAL Ms. Amruta Gokhale 1 , Dr. Sanjay Bokade 2 and Shashank Shetty 3 1,2,3 Mechanical Engineering, MCT’s Rajiv Gandhi Institute of Technology, Mumbai University, Andheri (W), India Abstract— Spontaneous ignition and combustion of coal are the major problems for its mining and usage. The temperature of ignition or combustion of the coal mainly depends upon its rank. Generally, coals having lower ranks are more prone to the spontaneous ignition or combustion than the coal having higher ranks. But many times, as an exception, as the rank increases, the coal becomes more susceptible to spontaneous ignition. To check the variables which affect the susceptibility of the ignition of the coal, practical experimentation can be carried with some proper combustion setup. Bituminous coal is generally used in many applications. But to reduce the use of it, sub-bituminous coal may be examined. Keywords— Bituminous Coal, Sub-bituminous Coal, Volatile Material, Particle Size, air flow rate, Ignition Temperature. I. INTRODUCTION 1.1 Combustion of coal in burner Combustion process can be done by different methods such as fluidised bed combustion(FBC), pulverised coal combustion, integrated coal gasification combined cycle (IGCC). In FBC, fuel particles are suspended in a hot, bubbling fluidity bed of ash and other particulate materials (sand, limestone etc.) through which jets of air are blown to provide the oxygen required for combustion or gasification. The resultant fast and intimate mixing of gas and solids promotes rapid heat transfer and chemical reactions within the bed. In pulverised combustion, the basic idea of a firing system using pulverised fuel is to use the whole volume of the furnace for the combustion of solid fuels. Coal is ground to the size of a fine grain, mixed with air and burned in the flue gas flow. Biomass and other materials can also be added to the mixture. Coal contains mineral matter which is converted to ash during combustion. The ash is removed as bottom ash and fly ash. The bottom ash is removed at the furnace bottom. 1.2 Coal Contents The classification of coal is generally based on the content of volatiles. Other deciding contents in the coal are Carbon, Hydrogen, Oxygen, Sulphur and its heat content. Other than these, maceral content in the coal is also a deciding parameter in the classification of coals. Maceral in the coal is analogues to the minerals in rocks. Examples of maceral are inertinite, vitrinite, and liptinite 1.2.1 Inertinite Inertinite is oxidized organic material or fossilized charcoal. It is found as tiny flakes within sedimentary rocks. The presence of inertinite is significant in the geological record, as it signifies that wildfires occurred at the time that the host sediment was deposited. It is also an indication of oxidation due to atomospheric exposure or fungal decomposition during deposition. Inertinite is a common maceral in most types of coal. The main inertinite submacerals are fusinite, semifusinite, micrinite, macrinite and funginite. Most common type of inertinitemaceral is semifusinite. 1.2.2 Vitrinite Vitrinite is one of the primary components of coals and most sedimentary kerogens. Vitrinite is a type of maceral, where "macerals" are organic components of coal analogous to the "minerals" of roks. Vitrinite has a shiny appearance resembling glass (vitreous). It is derived from the cell-wall