Preparation of high-modulus sodium silicate solution and high Al/Si alumina-bearing concentrate from activated roasting clinker of coal fly ash

Abstract

Simultaneously preparing sodium silicate solution with high modulus and obtaining aluminum concentrate with high Al/Si ratio from activated roasting clinker is the key to a new method for clean utilization of coal fly ash. This study systematically investigates the leaching mechanism of SiO₂ from activated roasting clinker in sodium silicate solution and proposes an optimized leaching process. The colloidal particles formed by the condensation of siloxane groups increase the diffusion resistance of the leaching agent in the capillary pores, and the SiO₂ deep inside the pores is difficult to contact with the leaching agent, which is an important reason for the insufficient leaching of SiO₂ in high-modulus sodium silicate solution. A two-stage countercurrent leaching process proposed can simultaneously prepare sodium silicate solution with modulus greater than 2.5 and aluminum concentrate with high Al/Si ratio exceeding 11. This work provides a potential application solution for the development of clean and economically feasible technologies for the utilization of fly ash.

Keywords

coal fly ash / activated roasting / cristobalite / sodium silicate solution / leaching mechanism

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Central South University