Design of Self-Flow Chemically-Bonded Castables*
1 Federal University of São Carlos, Materials Engineering Department, Materials Microstructure Engineering Group (GEMM), São Carlos/Brazil
2 Petrobras, Rio de Janeiro/Brazil
Revision 24.10.2016, 01.11.2016
Volume 9, Issue 2, Pages 79 - 84
Abstract
The strength derived by using phosphate-based binders is related to the in situ generation of new phases, which takes place during the refractories’ initial processing steps. Considering the fast reaction rate of acid-base transformations, their exothermic feature and difficulties to optimise particle dispersion in acid medium, phosphate-bonded products are usually placed via gunning, hand packing or vibration. This work focused on developing high-alumina self-flow chemically-bonded castables for petrochemical/aluminium industries, based on adding sodium polyphosphates and phosphoric acid and monoaluminium phosphate solutions. Flowability, working and setting time, cold and hot mechanical strength, porosity and thermal shock measurements were carried out in order to evaluate the performance of the designed refractories. According to the results, the presence of sodium polyphosphates improved the castables’ flowability, resulting in maximum free-flow of 120–160 %. When compared to a vibratable phosphatebonded commercial product, the developed castables containing H3PO4 and MAP solutions presented higher mechanical strength and thermal shock resistance, in addition to their self-flow behaviour.
Keywords
petrochemical industry, aluminium industry, castable, flowability
References
[1] Luz, A.P.; Braulio, M.A.L.; Pandolfelli, V.C.: Refractory castable engineering. Installation techniques: focusing on shotcreting, 1st ed., Baden-Baden 2015, Chapter 5, 257–309 [2] Soudée, E.; Péra,J.: Influence of magnesia surface on the setting time of magnesia-phosphate cement. Cem. Concr. Res. 32 (2002) 153–157 [3] Rivenet, M.; et al.: A study of the Na2O–CaO–P2O5–SiO2 system with respect to the behavior of phosphate bonded basic refractories at high temperature. J. Europ. Ceram. Soc. 20 (2000) 1169–1178 [4] Luz, A.P.; et al.: Monoaluminum phosphatebonded refractory castables for petrochemical application. Ceram. Int. 42 (2016) 8331–8337 [5] Faison, J.; Haber, R.A.: Use of polyphosphates as deflocculants of alumina. Ceram. Engin. Sci. Proc. 12 (1991) 106–115 [6] Momeni, A.; Filiaggi, M.J.. Comprehensive study of the chelation and coacervation of alkaline. Langmuir 30 (2014) 5256−5266 [7] Strauss, U.P.; Treitler, T.L.: Degradation of polyphosphates in solution. I. Kinetics and mechanism of the hydrolysis at branching points in polyphosphate chains. J. Amer. Chem. Soc. 78 (1956) 3353–3357 [8] van Wazer, J.R.; Callis, C.: Metal complexing by phosphates. Chem. Rev. 58 (1958) 1011–1046
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