Mercury speciation and emission from municipal solid waste incinerators in the Pearl River Delta, South China

Abstract

The potential for Hg release during municipal solid waste incineration (MSWI) is attracting increased attention due to high volume of municipal waste being treated by incineration in China. Emission amounts have been estimated using emission factors developed for other countries. To fine tune our emission estimate total mercury (THg) and mercury speciation were measured using isokinetic sampling in eight plants, of which six used grate furnace combustor (GFC) and two circulation fluidized bed combustors (CFBCs). Results showed that average THg concentration (19.5±13.6μg/Nm3) in flue gas at the facilities that used CFBC was significantly lower than that at those using GFC (51.4±28.3μg/Nm3, p=0.002). Gaseous oxidized mercury (GOM), gaseous elemental mercury (GEM, Hg0), and particulate mercury (Hgp) represented 95.5±3.8%, 4.1±3.9% and 0.4±0.3% in GFC, and 63.8±8.6%, 33.6±10.5% and 2.6±1.9% in CFBC, respectively. The measured average THg emission factor for the 8 MSWI plants was 208±130mg/t in the Pearl River Delta (PRD) region, with 217±158mg/t and 188±17.7mg/t were from GFC and CFBC, respectively. Using the average emission factor the estimated total mercury emissions from MSWI were 4.67±2.91t in China, and 770±65.5kg in the PRD region in 2010. Of these, 4240±210kg, 408±231kg and 14.8±14.1kg, and 688±37kg, 78.9±40.6kg and 3.2±3.0kg were GOM, Hg0, and Hgp, respectively. Mercury emissions will continue to increase as the amounts of MSW being incinerated increases.