Combustible Municipal Solid Waste Gasification: Sulfur and Nitrogen Release and Distribution

Gasification has become an effective thermal technology for combustible municipal solid waste (CMSW) treatment. The produced sulfur- and nitrogen-containing compounds during gasification are being paid attention to owing to derived corrosion and emission issues. In this study, the release behavior of nitrogen and sulfur species from gasification of CMSW was investigated in CO2 and H2O atmosphere in a fixed-bed reactor. The experiments were performed at different temperatures and the collected gas-liquid-solid samples were analyzed separately using various methods, of which the concentration of various gas species including NOx, NH3, SO2, and H2S were determined by flue gas tester or Nessler's reagent colorimetric approach, and the contained components in tar were analyzed through gas chromatography-mass spectrometer technique. It was found that the release of nitrogen and sulfur changes with temperature and higher temperature generally promotes the formation of their corresponding gas-phase species. Certain amount of nitrogen and sulfur remained in char after gasification when the temperature rises from 600 degrees C to 800 degrees C. The NH3 content in product gas is much higher than NOx, where the latter species are detected only in part per billion level. The mass balance calculation indicates a possible existence of hydrogen cyanide and carbonyl sulfide in product gas. The tar compounds over the detectable range mainly consisted of hydrocarbons as well as several types of nitrogen-containing molecules but without sulfur-containing organics. An immigration route and distribution scenario of gasification cases <800 degrees C was concluded and further compared between CO2 and H2O atmosphere at last.