Predicting Chlorine Fate during Municipal Solid Waste Co-processing in Cement Kilns: Transformation, Clinker Retention, and Kiln Cycling

Authors:
  • XLXingwu Li
    Xingwu Li
  • SLSha Liang
    Sha Liang
  • ZYZhe Yang
    Zhe Yang
  • JQJunda Quan
    Junda Quan
  • LGLianzheng Gui
    Lianzheng Gui
  • XZXinpeng Zhang
    Xinpeng Zhang
  • YKYan Ke
    Yan Ke
  • YZYing Zheng
    Ying Zheng
  • HDHuabo Duan
    Huabo Duan
  • LPLu Peng
    Lu Peng
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Abstract
Co-processing municipal solid waste (MSW) in cement kilns can recover waste as an alternative fuel and raw material, but MSW-derived organic chlorine (O-Cl) may circulate within the kiln system and deteriorate clinker quality and cement performance, thereby limiting MSW dosage. Here, polyvinyl chloride was used as a representative O-Cl source and co-processed with cement raw meal (CRM) to quantify Cl transformation, clinker retention, and cement compressive strength. Released Cl was captured by CRM and transformed into C12A7Cl2 and Alinite. C12A7Cl2 first remained in clinker when the initial Cl content in CRM (CI) reached 0.50%, corresponding to a residual clinker Cl content of 0.18%, whereas Alinite first remained in clinker when CI reached 1.00%, corresponding to a residual clinker Cl content of 0.74%. A residual clinker Cl content of 0.46% produced the greatest compressive-strength enhancement. A dynamic steady-state Cl circulation model was developed using experimental Cl volatilization data. The simulation results showed that, under continuous Cl cycling, the cycled Cl mass reaches 14 times the initial Cl mass when CI<0.016%. Additionally, residual clinker Cl contents of 0.18%, 0.46%, and 0.74% corresponded to CI values of 0.13%, 0.32%, and 0.50%, respectively, which were significantly lower than identified CI in the isolated experiments without Cl circulation. This study provides a predictive framework for tracking MSW-derived Cl flow and regulating Cl input during cement kiln co-processing.

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