Release of Chlorine and Sulfur during Biomass Torrefaction and Pyrolysis

Suriyati Binti Saleh, Julie Pauline Flensborg, Tooran Khazraie Shoulaifar, Zsuzsa Sárossy, Brian Brun Hansen, Helge Egsgaard, Nikolai De Martini, Peter Arendt Jensen, Peter Glarborg, Kim Dam-Johansen

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    Abstract

    The release of chlorine (Cl) and sulfur (S) during biomass torrefaction and pyrolysis has been investigated via experiments in two laboratory-scale reactors: a rotating reactor and a fixed bed reactor. Six biomasses with different chemical compositions covering a wide range of ash content and ash-forming elements were torrefied/pyrolyzed in the temperature range of 150–500 °C. The relative release of chlorine and sulfur was calculated based on mass balance and analysis of the biomass before and after torrefaction. In selected cases, measurement of methyl chloride (CH3Cl) in the gas from straw torrefaction has furthermore been conducted. The release of chlorine from straw was first observed at 250 °C and peaked with about 60–70% at 350 °C. Analysis of the released gas showed that most of the chlorine was released as methyl chloride. Increasing the straw content in the reactor resulted in a lower fractional release of Cl, probably due to more reactive sites in contact with gas phase Cl species leading to secondary binding of Cl to the solid product. Almost complete release of chlorine was observed for woody biomass at 350 °C. This result is in agreement with previous studies reporting that biomasses with a lower chlorine content release a higher fraction of chlorine during the pyrolysis process. A significant sulfur release (about 60%) was observed from the six biomasses investigated at 350 °C. The initial sulfur content in the biomass did not influence the fraction of sulfur release during torrefaction.
    Original languageUndefined/Unknown
    Pages (from-to)3738–3746
    JournalEnergy and Fuels
    Volume28
    Issue number6
    DOIs
    Publication statusPublished - 2014
    MoE publication typeA1 Journal article-refereed

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