Study On Optimization For Fluorine Removal From Technology Wastewater Of Nuclear Fuel Elements Plant

The wasterwater of the nuclear fuel element plant in China normally contains high concentrations of fluorine. In this study, the simulated wastewater with fluorine concentration of 10000mg/L was prepared based on the characterization of the real wastewater in the nuclear fuel element plant. The calcium ion was compensated by overdosing readily dissolved calcium chloride. Same-flow-path horizontal flow inclined board settling tank was utilized in order to improve the settling efficiency. Furthemore, bench- and pilot-scale experiments were conducted to optimize the operating parameters and performance of the integrated lime powder/calcium chloride technology for fluorine removal.It was found that the optimum dosage of lime powder is 110% higher than the theoretical dosage when lime powder was added into wasterwater alone. Around 85.35% of fluorine removal efficiency can be obtained after 30-min settling. Sequential addition of calcium chloride solution (0.25 mol/L) can further lower the concentration of residual fluorine to less than 10 mg/L, which successfully met the discharge standard.Changing temperature and pH can siginifantly affect the fluorine removal performance when using the lime precipitation method. With the addition of lime powder alone, relatively better fluorine removal efficiency (i.e., 95.28%) was reached at the temperature of 60 ?. As high as 96.31% of fluorine removal efficiency can be obtained at the pH value of 8.0.Under the optimum experimental condition, the concentration of residual fluorine in the treated wastewater can be lowered to 16.68 mg/L when the same amount of lime powder was used.Accordingly, the removal efficiency increased from 85.35% under uncontrolled reaction condition to as high as 99.83% under controlled reaction condition.In this study, the enhancing effect of same-flow-path horizontal flow inclined board settling tank on calcium fluoride was observed. The concentration of residual fluorine in supernatant successfully met the discharge standard (< 10 mg/L) Under 30-min batch-flow operation. Under continue-flow operation, the operation condition can get stable within 30 min. With 1 h of the hydraulic retention time, the concentration of residual fluorine was 14.85 mg/L.