氧化钙对流化床燃煤飞灰中砷的淋滤特性影响

在实验室小型流化床实验装置上,利用添加氧化钙研究了原煤中钙硫比变化对燃煤过程中砷在飞灰中的富集规律和飞灰中砷的浸出特性的影响。实验结果表明,增加钙硫比能有效促进砷在飞灰中富集,降低砷的排放。砷与氧化钙的反应受制于钙的硫化反应控制。飞灰中砷的浸出与滤液pH值关系显著,碱性飞灰导致滤液pH值增大,能有效抑制飞灰中砷的浸出。碱性飞灰中砷的浸出历程为飞灰中砷在短时间内快速溶出;随着滤液pH值增大,溶出的砷与钙发生二次反应形成钙砷化合物沉淀,降低滤液中砷浓度。

Effect of CaO on leaching characteristics of arsenic in fly ash from fluidized bed coal combustion

The leaching characteristics of arsenic in fly ash from coal combustion in lab-scale fluidized bed were clarified. Calcium oxide was mixed with fed coal for matching different Ca/S molar ratio to investigate the role of calcium on the leaching behavior of arsenic. The results indicate that increase in Ca/S molar ratio promotes the retention of arsenic in fly ash and in turn reduces its emission. The reaction between CaO and arsenic is largely dependent on the sulfation of CaO. Leaching of arsenic from fly ash is greatly dependent on the pH value of leachate. Alkali fly ash generates a high pH value solution during leaching test, facilitating the prohibition of arsenic leaching. The mechanism of arsenic leaching in alkali fly ash can be described as that arsenic first releases from fly ash quickly and then subjects to the reaction with calcium to form precipitate under high pH value condition.