Effect of Ca(OH)2 on the chemical precipitation of phosphates from solutions of a low concentration in fluidized bed reactor: hydrodynamic evaluation
In this present work, the phosphate is precipitated chemically at 22°C using synthetic water at different Ca/P molar ratios ranging from 0.5 to 12. Various parameters have been optimized to a range of realistic conditions relative to chemical precipitation of phosphates (superficial velocity of fluid Uf = 0.58 cm/s, [PO4] = 10 mgP/L). A hydrodynamic evaluation of the chemical precipitation of phosphates in a fluidized bed reactor, contains sand particles as a substrate for the precipitate layer, from an ascending water stream using Ca(OH)2 was made. As a function of Ca/P, the occurrences domains of the different hydrodynamics parameters are given. The effect of the Ca(OH)2 on the porosity and the velocity of the fluidized bed it also presented. For the inlet Ca/P molar ratio, was lower than 4, the phosphate removal efficiency is 35~74%. While, for the suitable conditions of Ca/P>4, the phosphate removal efficiency ranging from 75 to 92%. It is found that the [Ca] and [PO4] significantly affect the velocity of fluidization and the porosity of the fluidized bed. In this connection, the experimental data of several authors provide a useful starting point for our comparisons.
Keywords: Chemical precipitation - Fluidized bed - Phosphate - Porosity - Molar ratio