Desulfurization of thar lignite by oxidative alkali leaching under pressure

Abstract

ABSTRACT In this research work, thar coal was treated with NaOH solution in dissolved oxygen with different reaction parameters in an isothermal reactor. All three types of sulfur were removed from coal through oxidative alkali leaching under pressure. About 90% pyretic sulfur, 78% organic sulfur and 50% sulfate sulfur were removed, and more than 82% of total sulfur removal was achieved. Effects of various reaction parameters were observed, it was investigated that reaction time, agitation speed and partial pressure of oxygen have positive effects on the rate of desulfurization. Whereas desulfurization was increased with increase in reaction temperature and alkali concentration till optimum value as 120°C for temperature and 2.5 Molarity of NaOH solution for alkali concentration . While desulfurization was decreased with further increase in values of temperature and alkali concentration. The rate of desulfurization was observed maximum with minimum particle size of 40 µm. An Optimized reaction was performed reaction time 120°C oxygen partial pressure 200 psi, particle size 40 µm, NaOH concetration was 0.25 Molarity, reaction time was 3 hours agitation speed was 2000 rpm, after getting the optimum values of all reaction parameters. Processed and raw thar coal was characterized with Thermogravimetric Analysis (TGA) and Testo smoke number to investigate the combustion behavior of processed coal. It was observed that the combustion properties of processed coal were improved than that of raw coal and black smoke in processed coal was reduced.