Enhanced elemental mercury removal from coal-fired flue gas by sulfur-chlorine compounds.
Oxidation of Hg(0) with any oxidant or converting itto a particle-bound form can facilitate its removal. Two sulfur-chlorine compounds, sulfur dichloride (SCl2) and sulfur monochloride (S2Cl2), were investigated as oxidants for Hg(0) by gas-phase reaction and by surface-involved reactions in the presence of flyash or activated carbon. The gas-phase reaction between Hg(0) and SCl2 is shown to be more rapid than the gas-phase reaction with chlorine, and the second order rate constant was 9.1 (+/- 0.5) x 10(-18) mL-molecules(-1) x s(-1) at 373 K. The presence of flyash or powdered activated carbon in flue gas can substantially accelerate the reaction. The predicted Hg(0) removal is about 90% with 5 ppm SCl2 or S2Cl2 and 40 g/m3 of flyash in flue gas. The combination of activated carbon and sulfur-chlorine compounds is an effective alternative. We estimate that coinjection of 3-5 ppm of SCl2 (or S2Cl2) with 2-3 Lb/MMacf of untreated Darco-KB is comparable in efficiency to the injection of 2-3 Lb/MMacf Darco-Hg-LH. Extrapolation of kinetic results also indicates that 90% of Hg(0) can be removed if 3 Lb/MMacf of Darco-KB pretreated with 3% of SCl2 or S2Cl2 is used. Mercuric sulfide was identified as one of the principal products of the Hg(0)/SCl2 or Hg(0)/S2Cl2 reactions. Additionally, about 8% of SCl2 or S2Cl2 in aqueous solutions is converted to sulfide ions, which would precipitate mercuric ion from FGD solution.
Yan
Nai-Qiang
NQ
Environmental Energy Technology Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720, USA.
Qu
Zan
Z
Chi
Yao
Y
Qiao
Shao-Hua
SH
Dod
Ray L
RL
Chang
Shih-Ger
SG
Miller
Charles
C
D000393:Air Pollutants / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D017606:Chlorine Compounds / Q000737:chemistry*; D003031:Coal; D060729:Coal Ash; D004784:Environmental Monitoring / Q000379:methods; D008628:Mercury / Q000737:chemistry*; D010084:Oxidation-Reduction; D052638:Particulate Matter / Q000737:chemistry; D011210:Power Plants; D012037:Refuse Disposal / Q000379:methods*; D013455:Sulfur / Q000737:chemistry*
D000393:Air Pollutants; D017606:Chlorine Compounds; D003031:Coal; D060729:Coal Ash; D052638:Particulate Matter; D013455:Sulfur; D002244:Carbon; D008628:Mercury