Release and transformation behavior of Cl during pyrolysis of torrefied rice straw

Pyrolysis experiments in a fixed-bed reactor at 800-1200 °C were carried out to compare the release and transformation behavior of Cl between raw and torrefied rice straw. The impact of torrefaction pretreatment on total release of Cl during rice straw high temperature pyrolysis has also been assessed. The influence factors, including volatile matter, particle structure, surface elements enrichment and occurrence forms of Cl, which are different between raw and torrefied rice straw, have been studied. The results show that Cl release ratios of torrefied rice straw at 250 and 300 °C are lower than that of raw rice straw during pyrolysis at 800-1200 °C. At 900-1200 °C, release ratio of Cl of torrefied rice straw decreases with the torrefaction severity. Torrefaction pretreatment at 250 and 300 °C inhibits the total release of Cl during rice straw pyrolysis at 1000-1200 °C. Enrichment of Cl on surface for torrefied rice straw accelerates the release of Cl. The removed volatiles during torrefaction would reduce the release of Cl during pyrolysis, and generated organochlorine (or CCl) during torrefaction has the same inhibiting effect on the release of Cl. Surface morphology and specific surface area of pyrolysis char are different between raw and torrefied rice straw. Less specific surface area for pyrolysis char of torrefied rice straw at 250 and 300 °C would restrict the release of Cl.