燃煤电厂脱硫石膏中重金属汞的稳定性研究

Study on Mercury Stability in Desulfurized Gypsum at Coal-fired Power Plants

燃煤电厂脱硫石膏在雨水中和太阳光长时间照射下,或作为固体废弃物加工过程中,吸附的汞会再次进入环境中,带来汞的二次污染。通过对脱硫石膏在煅烧、淋洗和暴露大气环境中等3种条件下对脱硫石膏中汞的稳定性进行研究。脱硫石膏中汞以多种化合物的形式存在,其主要是以氯化汞的形式存在。脱硫石膏在150℃煅烧时汞开始挥发,但流失率不高;当温度达到500℃时,汞已经大部分挥发出去,均达到92%以上,汞的流失率随煅烧时间的增加而增加,随煅烧温度的增加而增加,这表明煅烧时间和煅烧温度是影响汞的流失率的重要因素;在淋洗实验中,汞的流失率随淋洗液p H值的增加先增加后降低,随淋洗时间和淋洗液体积的增加而增加,表明淋洗液的体积和淋洗液的p H均是影响汞流失率的重要因素;在自然堆放的环境下,脱硫石膏中的汞随着存放时间延长逐渐流失,最低流失率为7.31%,最高流失率为21.35%。

Desulfurization gypsum deposits in the rain and sunlight for a long time,or it is utilized as a solid waste,and mercury that presents in gypsum emits into the environment once again,which brings the secondary pollution of mercury.Effects of calcination,leaching and exposure to atmospheric environment on mercury stability in desulfurization gypsum were studied.Desulfurization gypsum exists in various forms of mercury compounds,which mainly exists in the form of mercuric chloride.When calcination of the desulfurization gypsum was heated to 150 ℃,the mercury began to evaporate,but the loss rate is not high;when the temperature reached 500 ℃,most of mercury has been volatilized out,the loss rate is more than92%.The loss rates of mercury in the sample increase with the increasing of calcination time and calcination temperature,and it is suggested that the calcination time and temperature are important factors influencing loss rate of mercury.In the leaching experiment,mercury loss rates increase first and then decrease with increasing of leaching solution p H value,and mercury loss rates also increase with increasing of leaching time and solution volume,which indicates that volume and p H of the leaching solution is an important factors affecting the mercury loss rate.Under the environment of gypsum natural pile up,the loss rates of mercury in gypsum increase with extending of deposit time,and minimum loss rate was 7.31%,then the largest loss rate is 21.35%.