Journal
FUEL
Volume 140, Issue -, Pages 136-142Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.fuel.2014.09.094
Keywords
Mercury; Hg-0 re-emission; Distribution; WFGD; Additives
Categories
Funding
- National Natural Science Foundation of China [21277119]
- Science and Technology Project of Zhejiang Province, China [2012C23061]
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Wet flue gas desulfurization (WFGD) system has been increasingly recognized to be effective in Hg removal. But the generated secondary pollution due to Hg re-emission from desulfurization solutions or solid byproducts has received researchers' attention. In this paper, the distribution of captured Hg-(L)(2+) in the simulated WFGD slurry was studied as a function of various environmental factors. Experimental results indicated that the pH value had a strong effect on Hg2+ reduction but had negligible influence on the Hg2+ retention by the grained fraction of gypsum. Increasing in pH value resulted in higher Hg2+ reduction and over 46% of Hg2+ was found to be reduced into Hg-0 at pH 5.0. Besides, increased slurry temperature also promoted the Hg2+ reduction and Hg-0 re-emission as well as the Hg2+ retention efficiency by gypsum. Other factors including S (IV), Cl and NO3 concentration was found to inhibit Hg2+ transformation into Hg-0 but slightly promoted the Hg2+ retained in gypsum. Moreover, the addition of sodium sulfide (Na2S), 2,4,6trimercaptotiazine, trisodium salt nonahydrate (TMT), and sodium dithiocarbamate (DTCR) prevented the Hg2+ reduction and precipitated out as insoluble HgS, Hg-3(TMT)(2) and Hg(DTCR)(2) on gypsum. The findings presented in this study could provide theoretical basis for Hg removal in coal- fired power plants. (C) 2014 Elsevier Ltd. All rights reserved.
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