Effects of bed material size distribution, operating conditions and agglomeration phenomenon on heavy metal emission in fluidized bed combustion process

This study investigates the effects of the bed material size distribution, the operating conditions and the agglomeration/defluidization phenomenon on the heavy metal pollutant emissions in the combustion process. After defluidization, the emission concentration of heavy metals increased, because Na may form a low melting eutectic material that enhances bed material adherence. The emission of Cd increased when the feed simulated urban residues contained sodium; however, the presence of Na had no significant effect on the emission of Cr. Furthermore, the Cd emission concentration was low when the material had a Gaussian distribution; however, the decreases in the Cd emission when the bed material had narrow, binary or flat distributions were not significant. The heavy metal Cr showed the same trend. In addition to the operating parameters, the bed material size distribution may influence the heavy metal emissions during combustion processes.

When the feed urban residues contained Na, which might be formed low melting eutectic material to enhance bed material adherence to increase emission of Cd. However, the existence of Na had no significant effect on the emission of Cr. The Cd emission concentration was low when the material had a Gaussian distribution; however, the decreases in the Cd emission when the bed material had narrow, binary and flat distributions were not significant. Heavy metal Cr showed the same trend.Figure optionsDownload as PowerPoint slideHighlights
► Na may be formed low melting eutectic material to increase emission of Cd.
► Na has no significant effect on the emission of Cr.
► Added Ca can prolong defluidization and reduce heavy metal emission concentration.
► At three distributions, Cd emission concentration is lowest in Gaussian distribution.