Impacts of oxygen concentration on products up-grading of lignite from low-temperature pyrolysis

Pyrolysis experiment of lignite with the oxygen concentration of 0-16% (with the interval of 2%) was carried out on a fixed bed reactor under 550 ℃ to study the influence of oxygen concentration on low-temperature pyrolysis products.It was found that the oxidation heating effect of oxygen could promote the generation of gas and liquid.When the oxygen concentration reached 12%, the yield of liquid reached the maximum, and when the concentration of oxygen was too high, the effect of secondary reaction with liquid was remarkable, and the yield of liquid was decreased; while, when the oxygen concentration was 10%, the samples started to appear local combustion, the consumption of oxygen increased, the quality of solid product reduced fastest, the quality of gas product increased fastest, and the reduction of fixed carbon made the ash content of up-grading coal increase and the heat value decrease.Therefore, the up-grading temperature and reaction time should be reduced in the oxygen atmosphere.Results showed that the increase of oxygen concentration was beneficial for the removal of heterocyclic nitrogen from macromolecule in lignite, the oxygen can effectively remove unsaturated aromatic compounds.