Impact of sulfur-ash reduction treatment on combustion performance, SOx emissions, and flue gas temperatures of lignite coals: experimental and computational study

Abstract

This study is focused on experimental and computational investigation into effects of sulfur-ash reduction treatment over environmental and simulated combustion behavior of lignite coals, specifically Lakhra and Balochistan coals. The simulative investigation was conducted using computational fluid dynamics (CFD). A 2D CFD model of a coal combustor was developed using Ansys FLUENT to analyze the impact of coal treatment, pressure, and coal feeding rate on sulfur oxide (SOx) generation, combustion efficiency, and temperature profiles. The research aims to provide insights into optimizing coal combustion processes for efficient energy production and reduced environmental impact. The results indicate that treating coal leads to an increase in CO₂ and H₂O production while reducing CO levels, particularly evident in Balochistan coal. Elevated pressure positively affects combustion efficiency, reflected in higher CO₂ and H₂O mole fractions. The study also reveals that while combustion efficiency slightly decreases with an increase in coal feeding rate, treated coal exhibits a lesser decrease compared to raw coal. SOx generation is significantly reduced up to 55 to 62% after treatment, reaching negligible levels, with both pressure and coal feeding rate influencing SOx generation. Despite similar sulfur content, Lakhra and Balochistan coals exhibit comparable SOx generation due to their similar sulfur ranges. Temperature profiles show that treated coals exhibit higher temperatures during combustion compared to raw coals, with pressure and coal feeding rate directly influencing temperature. Maximum temperature was found in the range of 2555 to 2564 K. While pressure has a minor positive effect on temperature for Lakhra coal, Balochistan coal shows high sensitivity to pressure. These findings highlight the importance of coal treatment and pressure optimization for reducing SOx emissions and improving combustion efficiency in coal-fired power plants.