The behaviour of ashes and heavy metals during the co-combustion of sewage sludges in a fluidised bed

M. Helena Lopes, Pedro M.R. Abelha, Nuno Carlos Lapa dos Santos Nunes, José Santos Oliveira, Isabel Cabrita, Ibrahim K. Gulyurtlu

Research output: Contribution to journalArticle

81 Citations (Scopus)

Abstract

Co-combustion tests of dry sewage sludges with coal were performed in a pilot bubbling FBC aiming at the characterization of ashes and determining the behaviour of heavy metals in the process. The tests showed compliance with the regulatory levels as far as heavy metal emissions were concerned. The bottom ashes, which accounted for about 70% of the total ash production, were obtained in a granular form, with diameters ranging from 0.5 to 4 mm. The heavy metals were distributed in ashes obtained from different locations of the installation and their concentrations were found to vary depending on the location of capture. The increase in heavy metals content in bottom ashes was not found to lead to higher leachability and ecotoxicity compared to sewage sludges. suggesting that there could be opportunities for their further use. Mercury suffered vaporisation inside the reactor, thus leaving bottom ashes free of contamination by it. However, there was observed a strong retention of mercury in cyclone ashes due to the presence of unburned carbon which probably acted as an adsorbent. The effluent mercury was also found to be mostly associated with the particulate fraction, being less than 20% emitted in gaseous forms. The results suggested that the combustion of the sewage sludge could successfully be carried out and the amount of unburned carbon leaving the combustor but captured in cyclone was large enough to ensure substantial retention of mercury at low temperatures, hence could contribute to an improvement of the mercury release which still remains an issue of great concern to resolve during combustion of waste materials.
Original languageEnglish
Pages (from-to)859-870
Number of pages12
JournalWaste Management
Volume23
Issue number9
DOIs
Publication statusPublished - 1 Jan 2003

Keywords

  • heavy metals
  • Vaporization
  • Coal ash
  • Combustion
  • Storms

Fingerprint Dive into the research topics of 'The behaviour of ashes and heavy metals during the co-combustion of sewage sludges in a fluidised bed'. Together they form a unique fingerprint.

Cite this