Model study of the direct causticization reaction between sodium trititanate and sodium carbonate

The solid state reaction between sodium tri-titanate and sodium carbonate, forming mainly sodium pentatitanate, was investigated. Experiments were car ried out in a micro-differential reactor made of quartz glass at various te mperatures between 800 degrees C and 880 degrees C and in a pilot fluidized bed reactor operated in a semi-batch mode, in the former reactor, basic ki netic data was obtained by measuring the release of carbon dioxide. Differe nt kinetic models were considered to describe the conversion, such as the V alensi-Carter model for diffusion controlled reaction rates and the phase-b oundary model for first-order reaction kinetics. Furthermore, a model that included both diffusion in the solid material and the chemical kinetics was derived. This model described the experimental data obtained in the micro- differential reactor very well. However, for the fluidized bed experiments, these different kinetic models did not accurately describe the experimenta l data. Therefore, an improved model was developed, which also took into ac count the time taken for the reactants to achieve physical contact. This mo del gave good agreement with the experimental data.