Particulate Matter Formation During Co-Combustion of Agricultural Residues With Turkish Lignite Using a Drop Tube Furnace

Abstract

This study investigates the particulate matter formation during combustion of olive residue, almond shell, and Tunçbilek lignite. Selected fuels (olive residue and Tunçbilek lignite) were also co-fired to evaluate the influence on particulate matter emission. Olive residue was ground to different size ranges (< 125 µm and 212-300 µm) to investigate the influence of the particle size and blended in different ratios of biomass / coal to analyse the interactions between fuels. Tests were performed in a drop tube furnace at high temperature (1000 ºC), with a high heating rate (~10 4 ºC/s), and short residence time (~3 s). Fuel was fed into the furnace at a low mass rate of 10 g/h using a syringe pump. Particulate matter was collected using a 3-stage stack impactor and categorized according to the aerodynamic diameters, PM2.5, PM2.5-10, and PM10. The results obtained included particle burnout, and particulate matter concentration. Particle burnout was above 95% for all studied fuels. Particulate matter emission depended greatly on the fuel and the blend. Olive residue presented the lowest values of PM2.5 (176 mg/g ash in fuel fed) compared with both almond shell (214 mg/g ash in fuel fed) and Tunçbilek lignite (286 mg/g ash in fuel fed). PM10 emission was particularly low for olive residue (~200 mg/g ash in fuel fed), whereas almond shell and Tunçbilek lignite showed similar values (~400 mg/g ash in fuel fed). Larger biomass particles resulted in unchanged particulate matter emissions. Co-firing of the olive residue with the Tunçbilek lignite resulted in lower PM2.5 (as compared to neat olive); higher PM2.5-10 (as compared to neat lignite); and lower PM10 (as compared to lignite). Blends of OR-TL in 25-75 ratio showed lower values of both PM2.5 and PM10 as compared with the 50-50 blends of the same fuels.