Comparative assessment of different grades of coal for methanol production: Simulation, optimization, environmental and economic analysis

The present study reports the modeling and simulation of methanol production through the gasification of freshly mined three coal samples having different wt.% of ash, viz., low-ash coal (LAC), medium-ash coal (MAC), and high-ash coal (HAC), collected from three different locations in India. The effect of the input parameters such as steam-to-coal mass ratio and gasification temperature on process performance parameters such as stoichiometric number, syngas yield, green house gas emissions from the process stream or net stream carbon dioxide equivalent, and methanol yield was studied through process sensitivity analysis and input parameters are optimized for the maximum methanol yield and minimum green house gas emission. Primary economic investigation at optimized conditions revealed that an internal rate of return of 5.93% is achieved for HAC at minimum plant scale and setting the methanol selling price of 400 USD/ton whereas IRR obtained as 3.20% and 5.87% for LAC and MAC, respectively, at this condition. The coal sample, HAC, performed better due to a high internal rate of return (i.e., 7.53% at base case) and subsequently low production cost. The present study's findings can be decisive for the countries with substantial low-grade high-ash coal reserves concerning coal diversification for its sustainable consumption in methanol production.