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<p>Deposit formation in cement kiln systems constitutes a major operational challenge and has traditionally been interpreted as two independent phenomena: preheater concretions (build-ups) within the cyclone system and ring formation in the rotary kiln. The present study proposes a novel integrated accretion mechanism, demonstrating that preheater build-ups and kiln rings can evolve concurrently within a single operating cycle, thereby challenging the conventional conceptual separation of these processes. Comprehensive chemical and kinetic analyses, combined with mineralogical characterization using X-ray diffraction (XRD) with Rietveld refinement-including quantitative phase analysis, belite polymorphism assessment, and alkali–sulfate mapping—reveal that preheater concretions consist of partially calcined, chemically reactive material enriched in alkalis and sulfur. These deposits contain belite, free lime, and sulfate-bearing phases capable of generating low-melting liquid fractions. Upon transfer to the kiln transition zone (1200–1300&#xa0;°C), this material promotes the formation of sulfate- and aluminate–ferrite-rich melts, enhancing particle adhesion and initiating ring nucleation. Simultaneously, continued upstream build-up confirms the existence of a dynamic chemical coupling between preheater and kiln systems. The resulting kiln ring exhibits pronounced radial stratification reflecting local thermochemical gradients: ferrite-rich outer layers provide mechanical anchoring, a liquid-rich intermediate zone ensures cohesion, and termination toward the flame side is governed by limited sulfate retention. Kinetic analysis indicates that the observed ring develops over several weeks, driven by sustained alkali–sulfate-induced stickiness rather than short-term thermal fluctuations. Overall, these findings unify preheater and kiln deposit formation within a single systematic construction. This integrated perspective provides a new and robust basis for improved prediction, diagnosis, and mitigation of accretion issues in industrial cement kilns.</p>

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Emergent mineralogical processes leading to build-up and ring formation in cement kiln: insights from Rietveld quantitative phase analysis

  • 期刊论文

  • 发表日期：

    2026年6月22日

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  • Islem Labidi,
  • Sahar Belgacem,
  • Fatma Moncer,
  • Adel Megriche

摘要

Deposit formation in cement kiln systems constitutes a major operational challenge and has traditionally been interpreted as two independent phenomena: preheater concretions (build-ups) within the cyclone system and ring formation in the rotary kiln. The present study proposes a novel integrated accretion mechanism, demonstrating that preheater build-ups and kiln rings can evolve concurrently within a single operating cycle, thereby challenging the conventional conceptual separation of these processes. Comprehensive chemical and kinetic analyses, combined with mineralogical characterization using X-ray diffraction (XRD) with Rietveld refinement-including quantitative phase analysis, belite polymorphism assessment, and alkali–sulfate mapping—reveal that preheater concretions consist of partially calcined, chemically reactive material enriched in alkalis and sulfur. These deposits contain belite, free lime, and sulfate-bearing phases capable of generating low-melting liquid fractions. Upon transfer to the kiln transition zone (1200–1300 °C), this material promotes the formation of sulfate- and aluminate–ferrite-rich melts, enhancing particle adhesion and initiating ring nucleation. Simultaneously, continued upstream build-up confirms the existence of a dynamic chemical coupling between preheater and kiln systems. The resulting kiln ring exhibits pronounced radial stratification reflecting local thermochemical gradients: ferrite-rich outer layers provide mechanical anchoring, a liquid-rich intermediate zone ensures cohesion, and termination toward the flame side is governed by limited sulfate retention. Kinetic analysis indicates that the observed ring develops over several weeks, driven by sustained alkali–sulfate-induced stickiness rather than short-term thermal fluctuations. Overall, these findings unify preheater and kiln deposit formation within a single systematic construction. This integrated perspective provides a new and robust basis for improved prediction, diagnosis, and mitigation of accretion issues in industrial cement kilns.