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A Process Model for Underground Coal Gasification- Part-I: Cavity Growth

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Title A Process Model for Underground Coal Gasification- Part-I: Cavity Growth
 
Creator Samdani, Ganesh
Aghalayam, Preeti
Ganesh, Anuradda
Sapru, R.K.
Lohar, B.L.
Mahajani, Sanjay
 
Subject Underground coal gasification
compartment model
spalling
syn-gas
lignite
 
Description In underground coal gasification (UCG), a cavity is formed in the coal seam due to consumption of coal. The irregular-shaped cavity consists of three distinct zones: a spalled-rubble zone on the cavity floor, a cavity roof at the top and a void zone between the two. During UCG, the coal seam between the injection and production wells undergoes two distinct growth phases. In phase-I, coal/char near injection well gets consumed and cavity grows in a vertical (radial) direction and hits the overburden. Phase-II starts thereafter, in which the cavity grows in the horizontal direction towards the production well. The geometry and flow patterns are distinctly different in these two phases and should be considered as two separate events while modeling UCG process. This part of the paper presents an unsteady-state model for gas production during the initial vertical growth of the cavity in phase-I. A computationally less expensive compartment modeling approach, based on computational flow dynamics (CFD), is used to establish non-ideal flow patterns in the cavity. Furthermore, the model also incorporates reaction kinetics, heat transfer, mass transfer, intra-particle diffusional limitations and thermo-mechanical failure (spalling) of coal by using required parameters for coal of interest. The simulations are performed for a typical Indian lignite and the results are interpreted to demonstrate potential of the developed model. Simulations results such as dynamics in rubble, void and roof zone are explained using different parameters including reaction fronts, gas composition and exit gas calorific value. The average calorific value of exit gas was observed to be relatively steady in spite of changes occurring in each zone. Finally the simulation results are analyzed by comparing with the results of the reported laboratory-scale experiments performed on the same coal under UCG-like conditions.
Oil and Natural Gas Corporation Limited
 
Date 2015-03-20T17:39:03Z
2015-03-20T17:39:03Z
2015-03-20
 
Type Article
Preprint
 
Identifier http://dspace.library.iitb.ac.in/jspui/handle/100/17350
 
Language en