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Physical and chemical characteristics analysis of bottom ash and boiler tappings coming from the Burnaby Incinerator

University of British Columbia

The primary objective of this research was to update information collected some twenty years ago with a view to revisiting opportunities to enhance the utilization of the bottom ash, emanating from Metro Vancouver’s Burnaby Incinerator, from both as an aggregate and a source of recoverable metals. Bottom ash is made up of three stream; the material coming off the grates, grate siftings and boiler tappings. As review of the literature showed absence of information on boiler tappings characteristics, the opportunity was taken in this study to rectify that information gap to see if there was an opportunity for metal recovery. The work included the determination of grade size distribution, material composition and total metal concentration. In total 56 samples were analyzed; 32 bottom ash and 24 boiler tappings. Results from the grain size distribution samples showed that bottom ash is finer with about 5% fines retained on #200 sieve compared to about 2% some 20 years ago. Almost 50% of the bottom ash samples passed through No. 4 sieve compared to around 30% previously, making the bottom ash more amenable as an aggregate. Almost all (98%) of the boiler tappings passed through No. 4 sieve. Physical sorting of the coarser fractions showed ferrous and non-ferrous metals constitute about 22% of the bottom ash, glass and glass composites about 21% and ceramics about 25%, whereas 22 years ago it was 27%, 50% and 3% respectively. The secondary objective was to find out the dust characteristics. While processing dry bottom ash fractions, dust could come off it, which might contain heavy metals or silica, which may be hazardous when inhaled. To determine whether bottom ash fine fractions, if elevated to airborne concentrations, have substances in them of potential concern, total metals analysis was done on the size fractions less than 100 microns, which were considered to be in the inhalable sizes. Total metals analysis showed that bottom ash fines contain, as expected, a full suite of metals and about 1% silica. Comparing the total metal concentrations of the fines with bottom ash total metal results collected by Metro showed no apparent enrichment.

Text

2015-12-17

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/55871

Civil Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/