湿法脱硫系统中液相二价汞的还原抑制

湿法脱硫系统协同脱汞是当前燃煤烟气脱汞的重要方法,而进入脱硫系统的二价汞还原问题会降低汞的脱除效率,从而限制该方法的使用。在脱硫浆液中添加添加剂捕集和稳定二价汞能有效抑制二价汞的还原。在模拟浆液条件下考察多硫化钙、TMT、乙基黄原酸钠、EDTA和腐殖酸对液相二价汞的还原抑制效果。结果表明,多硫化钙和TMT能极大的抑制二价汞的还原,当其添加量分别为0.004%(体积分数)和0.002%(体积分数)时,汞还原量仅为未添加条件下的3.3%和0.8%,而乙基黄原酸钠、EDTA和腐殖酸在一定条件下不仅不会抑制二价汞的还原,反而会一定程度促进二价汞的还原。这表明乙基黄原酸钠、EDTA和腐殖酸并不适合于作为液相二价汞的还原抑制剂。

Oxidized mercury reduction inhibition by additives in wet desulfurization system

Co-removal oxidized mercury in wet desulfurization system is an important way to control mercury pollution of coal-fired flue gas. However, the reduction of absorbed mercury has negative effects on mercury capture efficiency,and consequently limit the usage of this method. Adding additives to capture and stable divalent mercury in wet desulfurization slurry could effectively suppress the reduction of oxidized mercury. The effects of five additives (includes calcium polysulfide, TMT, sodium ethyl xanthate, EDTA and humic acid) on mercury reduction were evaluated. Results indicated that calcium polysulfide and TMT can effectively inhibit the reduction of bivalent mercury. With 0.004%(volume fraction)and 0.002%(volume fraction)addition amount of calcium polysulfide and TMT respectively, the mercury emission amount only account for 3.3% and 0.8% of the base one. Instead, sodium ethyl xanthate, EDTA and humic acid could promote the reduction of bivalent mercury in certain conditions rather than inhibit it. The results suggested that sodium ethyl xanthate, EDTA and humic acid may not suitable as mercury reduction inhibit additives in wet desulfurization slurry.