含铀煤燃烧底灰中铀的形态分布及其影响因素研究

Uranium Speciation Distribution and Its Influencing Factors in the Bottom Ash of Uranium-bearing Coal Combustion

以云南临沧的含铀褐煤为研究对象,在实验室模拟燃烧试验,考察了不同温度、时间、原煤粒径和是否加入CaO4种燃烧控制条件下煤的燃烧过程,并采用逐级提取法分析了燃煤底灰中铀的赋存形态,讨论了不同燃烧条件下燃煤底灰中不同赋存形态铀的含量及其相互转化关系。结果表明:燃煤底灰中铁锰氧化物结合态铀和残渣态铀的含量随燃烧温度的升高而增加,碳酸盐结合态铀的含量随燃烧温度的升高而减小;在600℃、不同条件下的原煤燃烧过程中,燃煤底灰中碳酸盐结合态铀和铁锰氧化物结合态铀的质量随燃烧时间的增加逐渐增加,有机物结合态铀和残渣态铀的质量随燃烧时间的增加逐渐减少;原煤粒径较小时,在燃烧过程中易形成飞灰而降低各种赋存形态铀在燃煤底灰中的含量;在原煤燃烧过程中,加入适量CaO会提高燃煤底灰中除离子交换态铀外的各种赋存形态铀的含量,使燃煤底灰中的铀富集。

Taking the uranium-bearing lignite from Lincang,Yunnan Province as the research object,this paper investigates the combustion process of coal under different temperature,time,particle size of raw coal and the addition of CaO in the laboratory simulation combustion test.The paper adopts the sequential extraction procedures to analyze the species of uranium in the bottom ash and discusses the relationship between the mass of uranium in the bottom ash and combustion conditions.The results show that the mass of uranium bound to Fe-Mn oxides and residual in the bottom ash increases while that of uranium bound to carbonate decreases with temperature increasing.In the process of combustion at 600 ℃ with different conditions,the uranium mass of carbonate-bound state and iron-manganese oxide-bound state in coal-fired bottom ash increases with time,while the uranium mass of organic matter-bound state and residual state decreases with time.It is easier to form fly ash and reduce the content of uranium in bottom ash in the combustion process when particle size is smaller.Adding an appropriate amount of calcium oxide improves the content of all uranium species except exchangeable uranium,which resultes in the uranium enrichment in the bottom ash.