Development of a chemical kinetic model for a biosolids fluidized-bed gasifier and the effects of operating parameters on syngas quality

    Authors

    W. M. Champion; C. D. Cooper; K. R. Mackie;P. Cairney

    Comments

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    Abbreviated Journal Title

    J. Air Waste Manage. Assoc.

    Keywords

    BIOMASS GASIFICATION; SEWAGE-SLUDGE; MATHEMATICAL-MODEL; PYROLYSIS; GAS; AIR; COMBUSTION; MECHANISMS; REACTOR; FUELS; Engineering, Environmental; Environmental Sciences; Meteorology &; Atmospheric Sciences

    Abstract

    In an effort to decrease the land disposal of sewage sludge biosolids and to recover energy, gasification has become a viable option for the treatment of waste biosolids. The process of gasification involves the drying and devolatilization and partial oxidation of biosolids, followed closely by the reduction of the organic gases and char in a single vessel. The products of gasification include a gaseous fuel composed largely of N-2, H2O, CO2, CO, H-2, CH4, and tars, as well as ash and unburned solid carbon. A mathematical model was developed using published devolatilization, oxidation, and reduction reactions, and calibrated using data from three different experimental studies of laboratory-scale fluidized-bed sewage sludge gasifiers reported in the literature. The model predicts syngas production rate, composition, and temperature as functions of the biosolids composition and feed rate, the air input rate, and gasifier bottom temperature. Several data sets from the three independent literature sources were reserved for model validation, with a focus placed on five species of interest (CO, CO2, H-2, CH4, and C6H6). The syngas composition predictions from the model compared well with experimental results from the literature. A sensitivity analysis on the most important operating parameters of a gasifier (bed temperature and equivalence ratio) was performed as well, with the results of the analysis offering insight into the operations of a biosolids gasifier. Implications: As gasification becomes a more prominent waste disposal option, understanding the effects of feedstock composition and gasifier parameters on the production of syngas (rate and quality) becomes increasingly important. A model has been developed for the gasification of dried sewage sludge that will allow for prediction of changes in syngas quality (and energy recovery from the waste), and should be helpful in assessing the benefits of new gasification projects.

    Journal Title

    Journal of the Air & Waste Management Association

    Volume

    64

    Issue/Number

    2

    Publication Date

    1-1-2014

    Document Type

    Article

    Language

    English

    First Page

    160

    Last Page

    174

    WOS Identifier

    WOS:000329899300004

    ISSN

    1096-2247

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