Novel mercury control technology for solid waste incineration: sodium tetrasulfide (STS) as mercury capturing agent.
Traditional pollution control technologies are able to capture oxidized forms of mercury to some extent; however, they show low efficiency for the control of elemental mercury emissions. This study developed a novel mercury removal technology: injection of sodium tetrasulfide (Na2S4) dissolved in the sodium hydroxide (NaOH) solution in the spray-dryer system. The effects of flue gas temperature and Na2S4 level in flue gas on the mercury removal efficiency were investigated. Na2S4 was decomposed into Na2S (S2-) and elemental S (S0), which reacted with HgCl2 and elemental Hg (Hg0), and HgS was then formed. Under the optimized operation parameters, this technology can simultaneously remove over 88% of HgCl2 and more than 90% of Hg0 from a flue gas stream containing about 400 microg m(-3) Hg0 and 1200 microg m(-3) HgCl2. The increased flue gas temperature (>170 degrees C) and the decreased Na2S4-to-Hg mass ratio (S-Hg-R) (<2.0) had negative effects on the reactions of gaseous mercury (HgCl2 + Hg0) with ionic sulfur (S2-) and S0. All the experiments were conducted in a full scale hospital-waste incinerator with a capability of 20 tons per day (TPD).
Liu
Yangsheng
Y
College of Environmental Sciences, Peking University, Beijing 100871, China. yshliu@pku.edu.cn
Xie
Shaodong
S
Li
Yaqiong
Y
Liu
Yushan
Y
D006358:Hot Temperature; D017745:Incineration; D008628:Mercury / Q000737:chemistry / Q000302:isolation & purification*; D012037:Refuse Disposal; D017670:Sodium Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*
D017670:Sodium Compounds; D013440:Sulfides; C519323:sodium tetrasulfide; D008628:Mercury