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PARTICULATE MATTER FORMATION DURING CO-COMBUSTION OF AGRICULTURAL RESIDUES WITH TURKISH LIGNITE USING A DROP TUBE FURNACE

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 (~104 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.