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 initiated with shock shows promise for improving both system and combustion efficiencies. Both fragmentation and chemical kinetic pathways are qualitatively different in comparision to conventional coal combustion. The present work is a theoretical investigation of the above. The theoretical simulation starts with simple model and progressively incorporates more realistic analysis as convective boundary condition. It studies the passing of detonation wave on coal particle suspended in air. Concepts of solid mechanics are used in analyzing fragmentation of coal particle. A numerical CFD model is developed which includes stress developed due to both thermal and volatilization. Weibul statistical Analysis used to predict the fracture time and fracture location resulting from principal stress induced which is obtained using failure theories. It is observed that coal particle fragments within microseconds. Radiation does not have much effect on developed stress. Volatilization has effect only when particle is of larger size. While stress due to thermal effect dominated the fragmentation when particle size was smaller. Coal size distribution statistics is considered to obtain real regime.
The extent of fragmentation increases with increasing coal particle size since larger coal particle contains more absolute amount of volatiles that provides a higher inner pressure in coal particles compared with smaller ones. Coal particles with lesser size have bigger specific surfaces and the evolution rate of volatile matter is higher. Therefore, the inner pressure is lower because volatile matter has more specific surface area to escape, and fragmentation occurs less intensely. In this case fragmentation initiated by differential thermal stress due to temperature differences. Also, size reduction ratio increases with increasing particle size. Experiments shows that coal rank influences fragmentation most intensely because different coal ranks cause variation in quantity of volatile matter, hardness and strength of coal particles.
Coal is used as mixture of different sized particles in real industrial problems. Hence it is important to analyse the effect of detonation shock on mixture of coal particles. Data presented in this work from simulation run suggest that plasma assisted detonation initiated technolgy can fragment coal particles quickly. Average fracture time of mixture of coal particles is far less than detonation travel time for the case of the detonation tube considered here. It is observed that almost 90\% of coal particles fragment much earlier within travel time of shock. Average fracture time reduces as Mach number increases. Same phenomena can be observed for volatile matter generated at fracture and flow of volatile matter at fracture. Hence it can be concluded that plasma assisted detonation combustion leads to different volatilization and fragmentation pathways.
- I started with developing Heat Transfer Model (HTM) of simple constant temperature boundary condition using analytical methods. I predicted particle fracture time and location due to thermal stress only using failure criteria suggested by various failure theories.
- Applied this model to solve more realistic boundary conditions; convective and radiative boundary conditions.
- After successfully developing HTM analytically I moved on to develop numerical model for solution of more complex problem.
- I developed Computational Fluid Dynamics (CFD) code to solve convective and radiative boundary condition and compared it with analytical solutions. It matched with minimum error.
- After developing HTM numerically I developed Volatilization Model (VM) of volatile matter.
- I linked HTM and VM with Solid Mechanics Model (SMM) and obtained principal stresses developed in coal particle. Here it ends the linking of all models and gives Developed Stress Model (DSM).
- After successfully developing DSM I developed Failure Criteria Model (FCM) using Weibull’s Weakest Link Theory (WLT). This model is capable of giving fragmentation time, fragmentation location, temperature at the time of fragmentation, volatilization matter present at fracture, flow of volatile at fracture, pressure at fracture.
- This ends complete Primary Fragmentation Model (PFM) which includes HTM, VM, SMM, DSM and FCM.
- After developing PFM for single coal particle I developed Statistical Model (SM) which is capable of giving me average, Standard Deviation, Probability Density Function (PDF), Cumulative Distribution Function (CDF) of the mixture of different size coal particles.
- Patadiya D. M., Jaisankar S., Sheshadri T. S.,“Numerical Studies of Primary Fragmentation of Coal Particle Mixture Subjected to Shock Wave”. Accepted in Combustion Science and Technology.
- Jaisankar S., Patadiya D. M., Sheshadri T. S. ”Shock Wave Induced Thermal Fragmentation of Coal Particles” Accepted in Combustion Explosions and Shock Waves.
- Patadiya D. M., Jaisankar S., Sheshadri T. S., ”Detonation Initiated Disintegration of Coal Particle Due to Maximum Strain Energy Theory”, Journal of Coal Science and Engineering. 19(4):435-440, 2013.
- Patadiya D. M., Jaisankar S., Sheshadri T. S.,”Computational Model for Thermal and Volatilization Induced Spontaneous Fragmentation of Coal Particle” International Journal of Advancements in Mechanical and Aeronautical Engineering, 2(1):161-165, 2015.
- Patadiya D. M., Jaisankar S., Sheshadri T. S., ”Application of Maximum Principal Strain Theory for Study of Coal Particle Disintegration when Subjected to Detonation Wave”,ICCS&T 2013, pp. 603-613, Oct. 2013.
- Patadiya D. M., Jaisankar S., Sheshadri T. S., ”Computational Model for Thermal and Volatilization Induced Spontaneous Fragmentation of Coal Particle” Proc. of the Second Intl. Conference on Advances in Mechanical and Robotics Engineering AMRE 2014, pp. 44-48, Oct. 2014.