Usage of lime sludge waste from paper industry for production of Portland cement Clinker: Sustainable expansion of Indian cement industry

Abstract

The incorporation of lime sludge from the paper and pulp industry for the manufacturing of clinker in the cement industry is considered a more environmentally friendly option which is not acceptable due to stricter environmental norms. The cement clinkerization in the raw mix designs by utilizing different dosages of lime sludge, ranging from 0 to 50 (per cent by weight), together with other raw materials like limestone, clay, bauxite, and laterite with Lime saturation factor-LSF in between 92.87 and 93.26, Silica Modulus-SM in between 2.19 and 2.37 and Alumina Modulus-AM in between 1.12 and 1.14. The estimated free lime (CaOf) and mineral phase analyses on all lab-fired clinkers at 1350 °C, 1400 °C, and 1450 °C were done by X-ray diffraction and the phases conform with optical microscopy. The clinker fired at 1450 °C has more alite (C3S) phase in the range of (37–59% by weight) and less free lime in the desirable limit. The cement prepared using this lab-fired clinker imparts desirable mechanical strength. Here, lime sludge was incorporated as a raw material in the design of the raw mix for Portland cement clinker production, and it was discovered that the quality of the produced cement was within OPC's acceptable range in the limiting of cement quality. This has diminished lime sludge in the environment although it is still possible to consider it an acceptable alternative to limestone.