Oxidation behavior and caking property of coal under the atmosphere at low oxygen concentration

Abstract

Eight coals ranging from bituminous coal to brown coal were oxidized in a thermo-balance or a fixed bed reactor using 5 vol% of oxygen at 100-380°C for 10-400 min. The effects of coal particle size, coal rank, oxidation temperature and oxygen concentration on the oxidation behavior of coal were investigated. The caking property, FT-IR spectrum and pyrolysis behavior of sample oxidized were measured. The oxidation behavior strongly depended on the coal rank. The oxidation reaction of highly caking coal was controlled by the rate of internal gaseous diffusion. The caking property of bituminous coal decreases by the oxidation in the oxidative atmosphere of low oxygen concentration of 5 vol %, which corresponds to that in a flue gas. The aliphatic C-H groups in highly caking coals are easily oxidized during oxidation and remained in coal structure as relatively stable forms. The differences in chemical structure and caking property between the exterior part and the central part of oxidized coal particle was investigated. In the case of highly caking coal, the chemical structure and some properties of oxidized coal depends on the position of the coal particle because the mild oxidation reaction of coal proceeds from the exterior part of coal particle.