Examinations of the sulfur emission from pulverized lignite fuel, under pyrolysis and oxy-fuel combustion condition

Problem of gas emission as NOX, SOX, heavy metals from fossil fuel combustion process is still under study. Especially the oxy-condition effect on gas emissions from oxy-fuel requires more analysis and research. This paper focuses on SO2 and SO3 behaviour investigation during air and oxy-fuel combustion processes, and formation of H2S and SO2 from N-2 and CO2 atmosphere. The research focuses especially on Polish medium sulphur coals. In the paper selected brown coals were examined on the content of total sulphur. During the tests campaign one type of lignite, predried to M-raw = 15% was a subject of pyrolysis at 800 and 1000 degrees C under N-2 and CO2 atmosphere, and further combusted in three different atmospheres: air atmosphere, and two different oxy atmospheres with O-2/CO2 ratios, equal 25/75% and 30/70% (vol.). Tests were carried out on an isothermal flow reactors (IFR) in a large laboratory scale. The influence of the CO2 atmosphere in oxy-condition in comparison with to the air atmosphere on SO2, SO3 emission intensity was determined. The results showed that the change of atmosphere from the air atmosphere to oxy atmosphere and increase of oxygen concentration in O-2/CO2 combustion atmosphere results in the increase of the conversion ratio of sulphur from solid phase to a the gas phase for the lignite. During the pyrolysis process it is mainly the H2S that is released in the gaseous form.