Arsenic Emissions and Speciations in High-temperature Treatment of a Typical High Arsenic Coal

Abstract

A series of experiments on release behaviors of arsenic in thermal treatment, e.g., pyrolysis, combustion, and gasification, of a typical high arsenic coal were conducted in a laboratory-scale drop tube furnace. Mineralogy of the coal and ashes was characterized by X-ray diffraction and field emission scanning electron microscope with energy dispersive X-ray spectrometer. Distributions and speciations of arsenic in the coal and ashes were determined by using the inductively coupled plasma mass spectrometry and time-of-flight secondary ion mass spectrometry. The results indicated that quartz and pyrite in coal would transformed into mullite and hematite. The decompositions of pyrite are followed by the unreacted coal modal and controlled by the surface sulfur vapor pressure, and pyrite would be transformed to Fe or Fe₂O₃ finally. Bleeding ration of arsenic in air combustion, CO₂ gasification, and N₂ pyrolysis is 85, 65, and 45 %, respectively, at 1300 °C. Arsenic is obviously enriched in the fine particles of size around 0.1–0.2 μm both in coal combustion and gasification. The arsenic species of arsenic in fine particles generated from coal gasification is As₂O₅, As, AsO, Ca₃(AsO₄)_2.