高炉矿渣对铝电解废旧阴极炭焚烧中氟化物的迁移转化行为影响

Influence of blast furnace slag on the behavior of fluoride in the incineration of spent potlining

废旧阴极炭(Spent potlining)是铝电解行业产生的一种高无机氟含量危险废物.本研究以高炉矿渣(Blast furnace slag)为添加剂与废旧阴极炭混合焚烧,模拟计算有关反应的吉布斯自由能,研究焚烧过程中氟化物的转化和稳定化行为.结果表明,高炉矿渣中的钙基化合物可促进废旧阴极炭中的NaF和Na_(3)AlF_(6)转化为稳定的CaF_(2).在850℃、焚烧1 h的条件下,废旧阴极炭和高炉矿渣混合样(4/6,质量比)水溶性氟浸出率降低42.27%;同时,减少HF释放可使氟化物保留率提高3.85%.高炉矿渣的掺入将其中93.50%的氟化物固定于底渣中,显著降低了废旧阴极炭的浸出毒性.高炉矿渣中的SiO_(2)和Al_(2)O_(3)促进了NaF向CaF_(2)的热转化行为,高炉矿渣参与焚烧使得焚烧底渣颗粒更加疏松、分散,底渣的氟化物主要以Ca_(4)Si_(2)O_(7)F_(2)形态存在,表明高炉矿渣具有协同处置废旧阴极炭的良好性能.

Spent potlining(SPL)is a type of hazardous waste with high inorganic fluorine content produced in the aluminum electrolysis industry.In this study,blast furnace slag(BFS)was used as an additive to be mixed with SPL for incineration.This study mainly focused on the simulation and calculation of the Gibbs free energy during the reaction to reveal the conversion and stabilization behavior of fluoride during the incineration.The results showed that the calcium-based compounds in BFS could promote the conversion of NaF and Na_(3)AlF_(6)in SPL into stable CaF_(2).The water-soluble fluorine leaching rate of the mixed sample of SPL and BFS(4/6 mass ratio)decreased by 42.27%under the condition of incineration at 850℃for 1 h.At the same time,the release of HF reduced,and the fluoride retention rate increased by 3.85%.There was 93.50%fluoride was fixed in the bottom slag because of the incorporation of BFS.This technical improvement significantly reduced the leaching toxicity of SPL.The two materials of SiO_(2)and Al_(2)O_(3)in BFS promoted the thermal conversion behavior of NaF to CaF_(2).The participation of BFS in incineration made the particles in incineration bottom slag more loose and dispersed.The fluoride of the bottom slag mainly exists in the form of Ca_(4)Si_(2)O_(7)F_(2).The present study demonstrated that BFS has good performance in co-processing SPL.