Modelling Simulation and Statistical Studies of Primary Fragmentation of Coal Particles Subjected to Detonation Wave

Abstract

Coal is likely to remain an important energy source for the next several hundred years and hence advances in coal combustion technologies have major practical impact. Detonation combustion of coal initiated by a plasma cartridge driven detonation wave holds promise for improving both system and combustion efficiencies. Both fragmentation and chemical kinetic pathways are qualitatively different in comparison to conventional coal combustion. The present work is a theoretical investigation of fragmentation due to detonation wave. The theoretical simulation starts with simple model and progressively incorporates more realistic analysis such as combined convective and radiative boundary condition. It studies the passing of detonation wave on coal particles suspended in air. Concepts of solid mechanics are used in analysing fragmentation of coal particles. A numerical model is developed which includes stress developed due to both thermal and volatilization effects. Weibull statistical analysis is used to predict the fracture time and fracture location resulting from principal stress induced. It is observed that coal particles fragment within microseconds. Radiation does not have much effect on developed stress. Volatilization does not have much effect on fragmentation for the particle size considered in this work and stress due to thermal effect dominated the fragmentation. Coal size distribution statistics is considered to obtain real regime. Coal is used as mixture of different sized particles in real combustors. Hence it is important to analyse the effect of detonation wave on mixture of coal particles. Results presented in this work from simulation run suggest that plasma assisted detonation initiated technology can fragment coal particles faster. Average fracture time of mixture of coal particles is far less than detonation travel time for the detonation tube considered here. Simulation results suggest that almost 90% of coal particles fragment early. Average fracture time reduces as Mach number increases. Same phenomena can be observed for volatile matter generated at fracture and ow of volatile matter at fracture. Hence it can be concluded that plasma assisted detonation combustion leads to different volatilization and fragmentation pathways.