Effects of Alkali Metals on the Formation of Particulate Matter and Adsorption of Floating Beads during Zhundong Coal Combustion

Zhundong coal plays an important role in China's energy utilization. However, due to its high content of alkali metals, it produces a large amount of particulate matter during combustion. In this paper, the coal was first washed with deionized water to remove the influence of alkali-metal salts. Then, different kinds of Na salts (1% NaCl, 1% Na2SO4, and 1% NaAc) were added to the de-alkali coals. The effect of Na salts on the formation of PM10 was studied in a high-temperature drop-tube furnace at 1300 degrees C. After the addition of the Na salts, the amount of particulate matter emission was significantly increased. When 1% NaCl was added to the de-alkali coal, the amount of PM produced was 3.1 times that of the raw coal, while the amount of PM2.5 produced was 3 times that of raw coal. After adding 1% Na2SO4, the amounts of PM1 and PM2.5 produced were twice those of the raw coal. In addition, floating beads exhibit a good adsorption effect on particulate matter for the combustion of the coal with different Na salts added. The yield of ultrafine and submicrometer particles was significantly reduced when 3% floating beads were added to the de-alkali coal with Na salts added. The reductions of PM1 were 47.0% for NaCl, 51.0% for Na2SO4, and 29.4% for NaAc. Additionally, the adsorption process of floating beads on ultrafine and submicrometer particles is mainly through the reaction between alkali-metal vapors and SiO2 and Al2O3 in the sorbents.