Abstract:
Production of syngas by gasification of locally available coal in the moving bed
gasifier is one of the most economical and promising options to produce high
calorific value gaseous fuel. Syngas contains significant amounts of C1—C4
hydrocarbons. Regarding the current situation of energy crisis and increase in the cost
of conventional fuels (i.e. furnace oil) biomass and coal seems to be a cheap and
accessible fuel in this part of the world. In these prevailing circumstances, syngas
from surface mined coal gasification could be suitable alternate for limited natural
gas. A moving bed gasifier designed by Aspentech in 2010 has been used to get some
important results using local lignite coal samples, which are helpful in analyzing the
potential of this conventional fuel. For this study, Aspen-Plus V8.0 has been utilized
to simulate the performance of gasifier. The gasifier can withstand the temperature of
950°C and a pressure of 3.5MPa. Several numbers of RCSTRs are used to specify
gasifier in the model, which utilizes 5 kg/s of coal after drying and pyrolysis. In this
study steam is used as a gasifying medium. The R-yield reactor is used for pyrolysis
in the modeling. Particle size distribution (PSD) is not considered in the model and
coal feed is assumed to be pretreated to remove excessive moisture to 5 % in the
proximate analysis for the simulation in gasifier. Fortran Subroutine codes built in the
model were used for obtaining the mass and energy balances for the different process
steps within the syngas production process. Sensitivity analysis and process
optimization is done by considering pyrolysis temperature and S/C ratio as input
variables. Based on this investigation, critical process steps for process heat
integration and syngas yield are identified.
