Microwave pyrolysis of herb residue for syngas production with in-situ tar elimination and nitrous oxides controlling

Abstract

As a typical industrial biomass waste which has high moisture and nitrogen content, herb residue (HR) causes raising attention. Microwave pyrolysis for integrated with in-situ reforming was proposed for clean syngas production from HR. Effects of microwave heating, reaction temperature and types of catalysts were investigated, and the tar elimination and nitrous oxides controlling performance were evaluated. Comparatively, microwave showed more enhancement on tar elimination than conventional heating due to the hot spots and microwave plasma effects. With the combined effects of microwave and nickel-based catalyst, the highest tar reduction as 74% was obtained, and the gas production was also improved by 143%. Moreover, the nitrous oxides emission could be reduced by 37%. Microwave heating tests of HR with different moisture contents were also conducted. Microwave was appeared more suitable for treating moist HR because the interactions between microwave and water could not only facilitate the heating process, but also attribute to clean syngas production. Moreover, the mechanisms of permanent gas releases and nitrous oxides reduction by catalysts were revealed by Thermogravimetry-Mass Spectrum-Fourier Transform Infrared Spectroscopy (TG-MS-FTIR). This work provided a fundamental insight into microwave processing of HR, and presented a comprehensive evaluation on the pollutant elimination.