低温等离子体改性烟草焦脱除烟气中汞的实验研究

以废次烟草为原料，用盐酸溶液对800℃焦进行酸洗，然后采用低温等离子体对酸洗后的焦进行改性，研究低温等离子体改性时间对焦孔隙结构和表面化学特性的影响，以及对烟气中Hg⁰的脱除影响特性。利用氮气吸附/脱附、FTIR等方法对烟草焦改性前后的微观理化特性进行表征，在固定床上测试改性焦的脱汞率。结果表明：低温等离子体改性使烟草焦表面的孔隙结构减少，使有利于脱汞的酸性含氧官能团COOH和C=O的活性位含量随改性时间延长先增加后减小，改性作用使焦表面活性位的密度随改性时间逐渐增加。烟草焦改性后对汞的脱除率显著增加，且随改性时间的增加先增加后减小，改性5 min焦脱汞量最大，在2 h内为126.4μg/g。改性焦表面孔径偏大的微孔和中孔通道内的含氧官能团活性位对脱汞起到主要作用，而极微孔仅在吸附初期起作用，并被快速堵塞。

Low temperature plasma surface modification of tobacco char experimental study on the removal of mercury from flue gas

The effect of low temperature plasma modification time on the pore structure,surface chemical properties and the Hg⁰ removal characteristics of tobacco char was studied. Waste tobacco was pyrolyzed at 800℃,then washed with HCl solution and modified by low temperature plasma separately to prepare tobacco modified char. Microstructures of the prepared tobacco chars were characterized based on instrumentations of nitrogen adsorption,FTIR(fourier transform infrared),and mercury removal performance of modified char in a fixed bed. The results indicated that low temperature plasma modification decreases the pore structure of tobacco char and the number of active sites,acidic oxygen functional groups (COOH and C==O) that are beneficial for the removal of mercury,increase first and then decreases over time. The modification can lead to a gradual increase of the surface active sites density of the chars. After modification,the efficiency of mercury removal from tobacco char increases significantly,and with increases in modification time,the removal efficiency increase firstly and then decrease. After 2 hours of adsorption,modified 5min,tobacco char is best to remove mercury,and the maximum absorption of mercury capacity is 126.4 μg/g. The active sites in the micropores of larger pore size and mesopores have a significant effect on the behavior of Hg⁰ removal;while ultramicropores work at the early stage of adsorption,they are quickly blocked.