Coprocessamento do resíduo catalítico (SFCC) na produção de clínqueres para cimentos especiais: cimento classe g e cimentos contendo ye’elimita

Abstract

The fluidized bed catalytic cracking process is the most used in the world for oil refining, and the catalyst (SFCC) is the main residue of this process. This waste is potentially dangerous, as it contains highly reactive metals and is not inert in its composition. Given the growth projection of this sector, it is necessary to search for an efficient environmental solution for the destination of this waste. In this sense, the co-processing of residues in cement kilns can be an alternative since the clinkerization conditions favor the immobilization and solidification of metals. Therefore, this study aimed to evaluate the co-processing of catalytic residue (SFCC) as a source of Al2O3 and SiO2 in clinker flour to produce special 8 Type G Portland cements, and 6 cements containing Ye'elimita (YCC). For this, the dosage of these types of cement was carried out in the laboratory. Clinkers were evaluated by physical, Chemical, and mineralogical analyses. The hydration was evaluated using isothermal calorimetry, X-ray diffraction (XRD) in situ, XRD and thermogravimetry (TG) at 3 and 28 days. The results of class G cements showed that the adopted production method was adequate since the clinkers and cements produced meet the normative requirements. Comparing the content of the phases potentially formed by Bogue and the quantification by Rietveld of the G clinkers, it was noted that the content of C3S was the closest to what was expected. In contrast, the content of C3A+ C4AF was lower than expected in all formulations. The class G clinkers produced showed noncrystalline or unidentified crystalline phases (ACn) ranging from 11 to 19%. In three of the evaluated formulations, it was shown that the SFCC clinkers stabilized proportionally more C3S-M1 than the reference clinkers. Concerning hydration kinetics, it should be noted that the clinkers with SFCC showed a reduction in setting time and anticipation of the sulfate depletion point. When analyzing the hydration products, it was observed that up to 7.3% of SFCC can be incorporated in the synthesis of type G clinker obtaining comparable results with the reference clinkers. YCC clinkers' production method was suitable for its synthesis, as the main crystalline phases were formed. The quantitative analysis of the clinkers by the Rietveld method showed that the SFCC clinkers stabilized more C4AF than the reference clinkers. In general, in the studied systems, it was possible to incorporate up to 20.81% of the residue, resulting in cements with greater reactivity in the first ages. Possible variations in the hydration products between class G and YCC clinkers with and without SFCC can be attributed to the ACn content, the presence of minor elements, the oxidation state and low crystallinity of the alumina derived from the SFCC. It is, therefore, noteworthy that co-processing SFCC in synthesizing special cements can be a viable alternative for reducing the environmental impact of the cement chain, promoting the minimization of the extraction of natural raw materials to produce these cements.