Modeling of lead migration in MSWI fly ash during the co-processing with cement kiln

The fly ash of municipal solid waste incinerator (MSWI) was added to the cement raw meal to produce clinkers on a lab scale and a real scale. The monitoring data of Pb in the cement kiln, which co-processed waste materials, were statistically analyzed to clarify the effect of total Pb or chloride input on Pb migration. A simplified mass balance model of Pb in the cement kiln was built to investigate the effect of kiln dust circulation on the migration characteristics of Pb when the substitution ratios of MSWI fly ash to cement raw meal were 1%, 5%, 10% and 20%, respectively. The results of the calculation model show that the Pb concentration in kiln dust and clinker increased quickly from 114.9 mg/kg and 21.1 mg/kg to 1125.6 mg/kg and 206.7 mg/kg respectively at the substitution ratio of 10%. Furthermore, the kiln dust circulation had a significant effect on the Pb concentration in kiln dust and clinker, which increased quickly to 200 mg/kg and 39.3 mg/kg at the initial 3 h and subsequently decreased slowly at the substitution ratio of 1% and at a kiln dust circulation ratio of 0.4.The Pb concentration in clinker increased to a large degree during the final stabilization stage when the kiln dust circulation rate increased from 0.4 to 1. The calculated and tested Pb concentration in clinker was 90.22 mg/kg and 82 mg/kg, respectively, which shows the calculation model is accurate.