Study on removal process of total organic carbon from industrial waste salts by pyrolysis
Highly efficient and low-cost removal of total organic carbon(TOC)from waste salt is an important pretreatment method in achieving salt resource utilization.This study focused on the high-temperature pyrolysis process of two representa-tive industrial waste salts(sodium chloride and sodium sulfate).The results showed that under the condition of 350℃and a stacking thickness of 12.5 mm,sodium chloride underwent pyrolysis for 60 min,the TOC removal rate was 94%.Under the condition of 450℃and a stacking thickness of 18.5 mm,the pyrolysis time of high sodium sulfate was 40 min,the TOC re-moval rate was 94.2%.Before pyrolysis,7.5 mL/kg hydrogen peroxide was added to high sodium chloride.The TOC removal rate during 250℃pyrolysis was comparable to that at 350℃without hydrogen peroxide.After adding 10 mL/kg hydrogen peroxide to high sodium sulfate,the TOC removal rate during 350℃pyrolysis was comparable to that at 450℃without hy-drogen peroxide.The pyrolysis temperature of both waste salts was reduced by 100℃after using advanced oxidation syner-gistic pyrolysis,and the energy-saving effect was significant.A stepwise crystallization experiment was conducted and the re-covered salt was tested.The results showed that under the condition of a recovery rate of 90%,the TOC content of the recov-ered sodium chloride and sodium sulfate were 22.7 mg/kg and 26.5 mg/kg,respectively.The purity of sodium chloride was 93.2%,which met the secondary standard of sun industrial salt in the national industrial salt standard.Sodium sulfate had a purity of 93.0%and met the Class Ⅲ qualified products standard in the national industrial anhydrous sodium sulfate stan-dard.
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