粉煤灰综合利用过程中汞的二次释放规律研究

Study on Mercury Re-emissions During Fly Ash Utilization

我国粉煤灰年产生量4亿t左右,近年来利用率稳定在65%～68%,主要利用方式包括建材生产、道路施工、建筑工程和农业利用.建材生产包括高温工序,可能存在粉煤灰中汞的二次释放.本研究设计实验模拟了水泥生产、蒸养砖生产的主要环境因素,利用程序升温脱附的方法研究粉煤灰利用过程中的汞迁移转化规律,并对全国范围内粉煤灰利用过程汞的二次释放量做出估算.研究发现,粉煤灰中的汞以HgCl2(Hg2Cl2)、HgS和HgO的形式存在;水泥生产过程中,粉煤灰中98%以上的汞会释放;蒸养砖生产过程中,粉煤灰中汞的平均释放率为28%,释放率主要受到粉煤灰中的HgCl2(Hg2Cl2)比例的影响.我国粉煤灰利用过程中的汞二次排放量由2002年的4.07 t.a-1增至2008年的9.18 t.a-1,其中水泥行业的贡献率占到96.6%.

The amount of fly ash produced during coal combustion is around 400 million tons per year in China.About 65%-68% of fly ash is used in building material production,road construction,architecture and agriculture.Some of these utilization processes include high temperature procedures,which may lead to mercury re-emissions.In this study,experiments were designed to simulate the key process in cement production and steam-cured brick production.A temperature programmed desorption（TPD） method was used to study the mercury transformation in the major utilization processes.Mercury re-emission during the fly ash utilization in China was estimated based on the experimental results.It was found that mercury existed as HgCl2（Hg2Cl2）,HgS and HgO in the fly ash.During the cement production process,more than 98% of the mercury in fly ash was re-emitted.In the steam-curing brick manufacturing process,the average mercury re-emission percentage was about 28%,which was dominated by the percentage of HgCl2（Hg2Cl2）.It is estimated that the mercury re-emission during the fly ash utilization have increased from 4.07 t in 2002 to 9.18 t in 2008,of which cement industry contributes about 96.6%.