Effect of Calcium Oxide Addition on Tar Formation During the Pyrolysis of Key Municipal Solid Waste (MSW) Components

Abstract

MSW pyrolysis/gasification is regarded as a promising technology allowing for energy and chemical recovery. The condensed tar in the syngas will cause problems in the downstream operations and lower its conversion efficiency. In this study, effects of calcium oxide (CaO) addition on tar formation during the pyrolysis of three key MSW components including bamboo, paper pulp and polyethylene (PE) were investigated using analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and a batch-type fixed bed reactor. The results from Py-GC/MS study agreed well with those from the pyrolysis in the fixed bed reactor, indicating that adding CaO reduced the tar yield and changed its chemical composition. However, the changes of the compounds in the tar were different among the pyrolysis of three MSW components. Taking the naphthalenes as an example, its content increased from paper pulp pyrolysis while it declined from bamboo and PE pyrolysis. Due to the rupture of ringed structures and tar cracking by CaO catalysis, the increase in H2 was observed. Compared with the pyrolysis of bamboo and paper pulp, higher yields of hydrocarbons C2 and C3 were achieved during the PE pyrolysis. The information about the tar formation derived from key MSW components can provide profound understanding of its generation from real MSW and favor the tar reduction or removal.