Reactor Model for the Underground Coal Gasification (UCG) Channel

Abstract

Underground Coal Gasification (UCG) is the process of in-situ conversion of coal into combustible products (syngas) which can be used either as fuel or as a chemical feedstock. In this study, the gasification channel is viewed as a one-dimensional packed bed reactor. The packed bed reactor model is solved incorporating chemical reactions and mass transfer effects. A pseudo-transient model is simulated for temperature and composition profiles of the gas and solid phases. The movements of the pyrolysis and the reaction front are obtained. The model results are in qualitative agreement with literature. The effects of various operating parameters are studied in detail. Steam/O2 ratio, inlet O2 and total pressure determine the solid temperature profile and hence the outlet gas composition. The simulations are performed for two sets of kinetics parameters. The solid temperature profile and outlet gas compositions change significantly with a change in kinetics parameters. The main motivation behind this study is to provide a theoretical base for understanding the critical aspects of UCG and to provide a tool which coupled with experiments will help in determining the commercial feasibility of the UCG process.

Recent development on underground coal gasification and subsequent CO 2 storage

“…Yang (2006) also presented a 3D unstable nonlinear numerical model of UCG to study the temperature field, concentration field as well as pressure field in the gasification panel. Khadse et al (2006) developed a 1D transient model for UCG by viewing the UCG channel as a packed bed and the coal particles are filled in the reactor and go through the processes of oxidation and gasification in a porous space. Because there are large differences in the characteristic times of the different variables in this model, the system of equations was divided in into two parts, one consisting of steady state gas phase and energy balance in only the length domain and the other set of solid balance equations in time domain only.…”

A process model for underground coal gasification – Part-I: Cavity growth

“…The model is a set of spatial-temporal stiff partial differential equations and is computationally intensive. To simplify the model, a pseudo steady-state assumption is made for the gas species because of the large differences in the characteristic times of the solid and gas variables 10 . This assumption allows dividing the system of equations into two sets: 1) steady-state gas-phase mass and energy balances in the radial direction and 2) a set of solid-balance equations in the time domain.…”

“…Chemical formula of tar formed in pyrolysis is based on the similar studies on coal 9,10 . Tar undergoes fastreforming (Reaction 11) in presence of its char 26 .…”

“…The model should provide useful inputs at the design stage for determining capacity of a pair of wells and should be able to predict the effects of unforeseen events such as water intrusion or sudden spalling. Several modeling efforts are reported in the literature and reviews are found elsewhere 2,7 .Available models can be classified into packed bed models [8][9][10] , channel models [11][12][13][14] , coal block models [15][16][17][18] and process models [19][20][21] . However, first three classifications have idealized flow patterns, and hence cannot adequately include effect of actual flow patterns on product gas composition.…”

Underground coal gasification: A new clean coal utilization technique for India

“…DTI of the UK have supported the European trials and followed it up with a series of desk studies (1999-2005) [10]. A fully operational UCG trial at a [7,21]. Up to 1979, three commercial scale plants were operated at Shatsky, Angren and Yushno-Abinsk [29].…”