Dheeraj Singh, Tarun Verma, J. V. Tirkey
This study presents an experimental and economic assessment of a 50-kW downdraft fixed-bed coal gasification system, bridging the gap between laboratory-scale investigations and industrially relevant producer gas applications. Unlike most prior studies focused on modelling or small-scale units, the present work provides experimentally validated performance and economic data for high-ash Indian coal under continuous operation. The gasifier was operated under air-blown conditions to evaluate syngas composition, thermal behaviour, gas yield, and CGE. The system produced a stable combustible producer gas with an average hydrogen concentration of approximately 14.02 ± 0.76 vol% and an LHV of 4.39 ± 0.14 MJ/Nm³. A cold gas efficiency of 61.5 ± 1.94% was achieved, demonstrating the effective conversion of coal's chemical energy despite the challenges associated with its high ash content. An economic evaluation based on the direct utilization and sale of producer gas was performed to assess long-term feasibility. The system generated an annual revenue of approximately USD 8112, resulting in a net present value (NPV) of about USD 19,889 over a 20-year project life at an 8% discount rate. The payback period was approximately 4 years, and the profitability index exceeded unity, indicating strong economic attractiveness. Sensitivity analysis further revealed that economic performance is more sensitive to syngas selling price than coal cost. Temperature measurements confirmed the establishment of stable gasification zones, and uncertainty analysis indicated that syngas composition and temperature measurements were reliable, with uncertainties within ±2% and ±2 °C, respectively.