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

Abstract

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 NO _x , 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°C to 800°C. The NH₃ content in product gas is much higher than NO _x , 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°C was concluded and further compared between CO₂ and H₂O atmosphere at last.