Influence Of Blast Furnace Slag On The Behavior Of Fluoride In The Incineration Of Spent Potlining

Spent potlining（SPL）is a hazardous waste with high inorganic fluorine content produced in the aluminum electrolysis industry.In order to solve the problem of disposal of waste cathode carbon,this topic proposes a high-temperature solidification of spent potlining with blast furnace slag（BFS）.This study utilizes the abundant calcium-silicon-aluminum oxides in blast furnace slag to solidify the fluoride in the SPL incineration process to realize the detoxification of leachable fluoride.And exploring the thermal disposal characteristics of SPL and the migration and transformation law of fluoride during the incineration process.The harmless and resourceful treatment of SPL and BFS is realized by treating waste with waste.The main work contents are as follows:（1）Study on the migration and transformation of fluoride when SPL is incinerated alone.Different incineration temperatures were selected to incinerate SPL separately,and the effects of incineration temperature on the distribution of fluoride,the morphology of bottom slag and the distribution of surface elements were investigated.The results showed that with the increase of temperature,the fluorine leaching rate increased from 41.37%to 47.19%,the proportion of fly ash and gaseous fluorine increased,the agglomeration of bottom slag became larger and the surface became smooth.The results of fluorine leaching experiments show that the fixed fluorine is more stable when the temperature is 25～85℃and the p H is 3～9.（2）Study on the effect of blast furnace slag on fluoride solidification in SPL incineration process.The results of thermodynamic simulations show that fluoride tends to convert to stable Ca F₂ and Ca₄Si₂O₇F₂ at high temperature.The optimal results of the experiment are that the incineration temperature is 850℃,the mass ratio of SPL/BFS is 4:6,the residence time is1h,the fluorine leaching rate is 1.59%,and the stability rate is 97.62%.XRD and FTIR results show that the incineration bottom slag is mostly thermally stable calcium-silicon-aluminum minerals.SEM results show that,compared with the single incineration of SPL,the 4/6 mixed sample bottom slag has a loose and rough surface.（3）In order to explore the fixation effect of different calcium-based compounds on SPL,the Gibbs free energy of the reaction between different calcium-based compounds and different fluorides was simulated and calculated in this study.And the effect of different calcium-based compounds on the fixation of fluoride in SPL was studied under the same conditions.The experimental results show that calcium oxide alone is difficult to spontaneously react with Na F to generate insoluble fluoride,and the addition of Si O₂ and Al₂O₃ can significantly promote the formation of insoluble fluoride.The experimentally determined fixation effects from high to low were:BFS,Ca Si O₃,Ca O,Ca CO₃ and Ca（OH）₂,and the conversion efficiency of fluorine was 26.55%,6.43%,4.39%,3.19%and 1.84%respectively.The exploration of the detoxification route of SPL incineration process with blast furnace slag as additive not only realizes the harmlessness of harmful components in the treatment process,but also realizes the reuse of resources,which provides certain theoretical guidance for the disposal of SPL.