(NH_(4))_(2)SO_(4)对烧结烟气脱硫活性炭的中毒机理

Poisoning effect of(NH_(4))_(2)SO_(4) on activated carbon from sintering flue gas on desulfurization

近年来,国家环保政策对烧结烟气污染物减排提出更高的要求,烟气脱硫脱硝成为钢铁工业烟气污染物治理的重点。活性炭具备良好的吸附性能和表面活性,在烟气净化领域得到广泛应用。部分钢铁企业利用烧结过程可以处理固废、废液等能力,将烧结烟气脱硫活性炭解析过程产生的制酸废液返回烧结处理,这造成制酸废液中成分会反应形成(NH_(4))_(2)SO_(4)进入烧结烟气,最终会与烟气中粉尘结合并被活性炭捕集。采集工业现场烧结烟气脱硫使用的新鲜活性炭和解析活性炭,在实验室模拟中毒条件,采用浸渍法对新鲜和解析活性炭进行(NH_(4))_(2)SO_(4)浸渍负载试验,研究了活性炭表面负载(NH_(4))_(2)SO_(4)对其脱除SO2性能的影响,并通过微观结构分析和表面官能团检测,揭示了(NH_(4))_(2)SO_(4)对活性炭的中毒机理。结果表明,新鲜活性炭和解析活性炭表面浸渍(NH_(4))_(2)SO_(4)后,2种活性炭的脱硫活性均出现显著降低,脱硫值分别由29.7 mg/g和53.5 mg/g降低到10.3 mg/g和19.6 mg/g。(NH_(4))_(2)SO_(4)对活性炭的中毒机理主要包括2个方面,一方面(NH_(4))_(2)SO_(4)会破坏活性炭表面官能,增加表面酸性,减少表面碱性官能团数量,从而影响活性炭脱硫性能;另一方面解析活性炭表面吸附了烧结烟气中粉尘,(NH_(4))_(2)SO_(4)会结合粉尘进入活性炭孔结构中,造成比表面积降低,微孔和介孔数量减少,进而降低其脱硫性能。在烧结烟气使用活性炭法脱硫的工业现场,不建议将含有铵根离子的固废或者废液返回烧结使用。

In recent years,new environmental protection policies have raised higher requirements for reducing emissions of pollutants from sintering flue gas,and desulfurization and denitrification of flue gas have become the focus of pollution control in the steel industry.Activated carbon has excellent adsorption performance and surface activity,and has been widely used in flue gas purification.Some steel companies took the advantage of the ability of sintering process to deal with solid waste and waste liquid,and returned the acid waste liquid generated by the desorption of desulfurization activated carbon in the sintering flue gas to the sintering process,where it reacts to form(NH_(4))_(2)SO_(4),which enters the sintering flue gas and eventually combines with dust and activated carbon for capture.Freshly used and desorbed activated carbon samples used for desulfurization of industrial sintering flue gas were collected from the site and subjected to(NH_(4))_(2)SO_(4) impregnation loading experiments under simulated poisoning conditions in the laboratory.The effects of(NH_(4))_(2)SO_(4) surface loading on the desulfurization performance of activated carbon were studied,and the mechanism of(NH_(4))_(2)SO_(4) poisoning on activated carbon was revealed by microscopic structure analysis and surface functional group detection.The results showed that after(NH_(4))_(2)SO_(4) impregnation loading on the surface of fresh and desorbed activated carbon,the desulfurization activities of both types of activated carbon were significantly reduced,and the desulfurization values decreased from 29.7 mg/g and 53.5 mg/g to 10.3 mg/g and 19.6 mg/g,respectively.The mechanism of(NH_(4))_(2)SO_(4) poisoning on activated carbon mainly includes two aspects.On the one hand,(NH_(4))_(2)SO_(4) will destroy the surface functional groups of activated carbon,increase surface acidity,and reduce the number of surface alkaline functional groups,thereby affecting the desulfurization performance of activated carbon.On the other hand,the desorbed activated carbon surface adsorbs dust from the sintering flue gas,and(NH_(4))_(2)SO_(4) will combine with dust to enter the pore structure of activated carbon,resulting in a decrease in specific surface area,and a reduction in the number of micropores and mesopores,thus reducing its desulfurization performance.It is not recommended to return solid waste or waste liquid containing ammonium ions to the sintering process in the industrial field of desulfurization of sintering flue gas using activated carbon method.