Fate of chlorine in rice straw under different pyrolysis temperatures

The fate of Cl in rice straw after pyrolysis in 200–1000 °C was investigated through heating of tubular furnace, sequential extraction, and determination using pyrohydrolysis combined with ion chromatography for total Cl, ion chromatography for inorganic Cl, and gas chromatography–mass spectrometry for CH3Cl. The rice straw and/or its chars after pyrolysis were characterized with thermogravimetric analysis, scanning electron microscopy, X-ray diffraction, and X-ray fluorescence. The results showed that, from 200 to 400 °C, water-soluble Cl in rice straw char decreased from 60.31 to 40.13% and released Cl was dominated by Cl-CH3Cl (Cl as CH3Cl) and Cl-HCl (Cl as HCl), with a release rate from 10.41 to 16.81% and from 28.76 to 35.34%, respectively. At 400 °C, 5.84% of Cl in tar (tar-Cl) was found. In the pyrolysis from 400 to 700 °C, in chars, water-soluble Cl changed a little and organic-bound Cl increased from 1.25 to 7.50%, released Cl-CH3Cl and Cl-HCl decreased from 13.41 to 2.42% and from 29.19 to 12.8...