Start
May 15, 2014 - 17:00
End
May 15, 2014 - 18:00
Venue
Creativity Hall (Room 118) Chemical Engineering
Event Type
Speaker
Ramesh Naidu Phd Student Chemical Engg.IIT Bombay.
Title
Kinetic Studies in Underground Coal Gasification
Abstract Underground coal gasification (UCG) is a well proven technology which permits access to coal which either lies too deep underground or is otherwise too costly to be exploited using conventional mining techniques. During the UCG process a cavity is formed in the coal seam when coal is converted to gaseous products. The rate of growth of this cavity and its shape at any given time depends on the reactant gas flow patterns kinetics. It leaves us with a scope to investigate the kinetics of the processes in UCG. Pyrolysis is an important step in the combustion and gasification of coal and its kinetics plays an important role in the design of pertinent reactors. In this work we have studied the kinetics of pyrolysis of three Indian lignite samples via experiments and mathematical modeling. Applicability of various kinetic models viz. the single global reaction model the consecutive reaction model and the distributed activation energy model is evaluated. The kinetic parameters of the models are estimated based on the experimental data. Kinetics of the evolution of the volatile matter is studied independently by using a specially designed fixed bed reactor and the relevant kinetic parameters are estimated. Gasification of four Indian coals is carried out in a CO2 atmosphere using a thermo gravimetric analyzer (TGA) to determine the intrinsic kinetics over a temperature range of 800-10500C with different partial pressures of CO2. The applicability of three models viz. the volumetric reaction model the shrinking core model and the random pore model is evaluated. Of these three models the random pore model is found to be the most suitable for all the coals considered in the current study. The dependence of the reaction rate on the gas-phase partial pressures is explained by the Langmuir - Hinshelwood model and the parameters for the inhibition due to CO and CO2 are determined by performing experiments at different partial pressures.. A one dimensional reaction diffusion model is therefore developed in order to determine the diffusional resistance in the coal particle and values of diffusivity are estimated. Steam gasification of Indian coals is carried out in a fixed bed reactor to determine the intrinsic kinetics over a temperature range of 740-8300C with different partial pressures of steam. The applicability of the random pore model is evaluated. The kinetic parameters are estimated.