Technological characterization of in nature, calcined and sulfated dolomitic limestone as means to dessulfuration

Limestones are widely used to capture sulfur gas emissions emitted during the burning of coal in power generation through its injection in boilers and furnaces. The technical characterization of this material becomes necessary to correct selection and use of a limestone rock. In this work, the technical and microstructural analysis of this raw material, including the characterization of the limestone in nature, calcined, and sulfated was performed. A limestone was evaluated in respect to physicochemical properties, particle size distribution, surface area, pore volume and SEM analysis. The metamorphic origin of the limestone explains its compact and little porous appearance, but after calcination the texture changes dramatically, with decreasing density, increased reactive surface and development of open porosity. These are key parameters for a good sulfur oxide sorbent. The fracture of particles is generated by the internal pressure during conversion of the carbonate into calcium oxide and release of CO2 during calcination. The calcium oxide reacts with sulfur oxide forming a compact layer of calcium sulphate, which reduces the specific area by blocking the pores, causing an increase in average and relative particle size during sulfation stage. The technological characterization performed revealed important aspects about the microstructure of calcined and sulfated limestone. The pressure generated by CO2 during sulfation, resulting from incomplete calcination of the limestone, is capable of breaking the thin layer of CaSO4 leaving rounded pores therein.

limestone; technological characterization; calcination; sulfation

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