Energy recovery and secondary pollutant emission from the combustion of co-pelletized fuel from municipal sewage sludge and wood sawdust

There are concerns about the boiler efficiency and the secondary pollutants emissions during MSS (municipal sewage sludge) combustion. In the present work, the pellets made from the mixture of MSS and wood sawdust were combusted in a regular boiler. The boiler efficiencies of 10% and 30% (MSS content %) MSS pellet fuels were 76.6% and 75.9%, respectively. The emission, mass balance and distribution characteristics of PCDD/Fs (polychlorinated dibenzo-p-dioxins and dibenzofurans) and heavy metals during the combustion of 10% and 30% MSS pellet fuels were also carried out in a traveling grate boiler. The international toxic equivalency quantities (I-TEQ) of the PCDD/Fs in the stack flue gas from the combustion of 10% and 30% pellet fuels were 0.191 and 0.157 ng I-TEQ Nm(-3), respectively. MSS exhibited a remarkable difference in ratios of PCDFs to PCDDs and congener profiles compared with stack flue gas, fly ash and slag. Ratio of PCDFs to PCDDs and congener profiles for slag also differed significantly from those of stack flue gas and fly ash. The emitted pollutants in the traveling grate boiler met the requirement of standards in China (GB 18485 -2001). (C) 2015 Elsevier Ltd. All rights reserved.