燃煤飞灰细颗粒物中痕量元素的分布与富集特性  

Characteristic of distribution and enrichment of trace elements in fine particulates of coal-fired fly ashes

作　　者：刘平 申奥 吴鑫玉 童姜毅 朱纯 段钰锋 LIU Ping;SHEN Ao;WU Xinyu;TONG Jiangyi;ZHU Chun;DUAN Yufeng(Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education,School of Energy and Environment,Southeast University,Nanjing 210096,China)

机构地区：[1]东南大学能源与环境学院能源热转换及其过程测控教育部重点实验室,江苏南京210096

出　　处：《中南大学学报(自然科学版)》2025年第1期322-333,共12页Journal of Central South University:Science and Technology

基　　金：国家重点研发计划项目(2018YFB0605102)。

摘　　要：为探究燃煤飞灰细颗粒物中痕量元素的分布与富集特性,采集了循环流化床锅炉的飞灰并筛分成4种粒径范围:>50μm、(43,50]μm、(38,43]μm和<38μm。利用XRF和XRD检测各粒径范围飞灰的主要矿物成分,确定煤中痕量元素的富集载体。采用改良的逐级化学提取法探究痕量元素的化学形态,探索粒径与痕量元素富集的关联性。研究结果表明:痕量元素在飞灰和底渣中都明显富集,在飞灰中的富集程度高于底渣的富集程度。痕量元素质量分数与飞灰粒径呈负相关,粒径小于38μm的细灰颗粒对痕量元素有很强的亲和力,Sr、Ce、Li和La的质量分数均大于100μg/g。在痕量元素的五种化学形态中,残余态(F5)在飞灰中质量分数最大,为62.6%~77.5%;其次是有机/硫化物态(F4),在飞灰中质量分数为9.3%~17.8%;再次是碳酸盐结合态(F2),在飞灰中质量分数为9.2%~14.2%;其余为离子可交换态(F1)和铁锰氧化物结合态(F3)。残余态源于煤中大多以铝硅化合物形式存在的痕量元素,燃烧后凝聚成铝硅酸盐玻璃赋存于飞灰中;有机/硫化物态主要来自煤中的有机物和硫酸盐;碳酸盐结合态主要来源于煤矸石的不完全燃烧;离子可交换态和铁锰氧化物结合态的质量分数极低,可能是煤中离子吸附矿物稀少,飞灰中铁、锰、钛的氧化物质量分数较低所致。For the purpose of delving the characteristic of distribution and enrichment of trace elements(TEs)in micrometers of coal-fired fly ashes,the fly ashes collected from a circulating fluidized bed boiler were sieved into four size scopes of bigger than 50μm,(43,50]μm,(38,43]μm,and less than 38μm.The major mineral components in the particle scopes were detected by XRF and XRD to determine the loading body for TEs.A modified sequential chemical extraction method was used to differentiate the chemical speciation of TEs to explore the correlation of enrichment to particle sizes.The results indicate that TEs favor to adhere to both fly ash and bottom ash and the tendency is bigger in fly ash than in bottom ash.The enrichment of TEs is inversely proportional to the sizes.The fly ash particles whose sizes are below 38μm have very strong affinity to the TEs,in which the mass fraction of Sr,Ce,Li and La are bigger than 100µg/g.Of the five chemical speciation of TEs,the residual(F5)occupies the biggest mass fraction of 62.6%to 77.5%.Next is the organic/sulfide(F4)sharing 9.3%to 17.8%,then the carbonate-bound(F2)with 9.2%to 14.2%.The remained are ion-exchange(F4)and the iron-manganese oxide-bound(F3).F5 originates from aluminum silicon compounds in coal that condenses to aluminosilicate glass after combustion.F4 stems from organics and sulfates,F2 comes from gangue owing to incomplete burn,and F1 and F3 are extremely low because of little ion-adsorption minerals in coal and little Fe,Mn and Ti compounds in fly ashes.

关 键 词：痕量元素 分布 富集 飞灰 细颗粒物 

分 类 号：X773[环境科学与工程—环境工程]