Continuous Reaction Crystallization of Struvite in a DTM Type Crystallizer with Jet Pump of Ascending Suspension Flow in a Mixing Chamber—Kinetic Approach of the Process

Reaction crystallization of struvite in water solutions containing 0.20 mass % of phosphate(V) ions by magnesium and ammonium ions addition was investigated experimentally. Process was carried out in DTM type crystallizer with liquid jet pump device in 298 K assuming stoichiometric conditions. Struvite crystals of mean size Lm 5.2- 23.0 m were produced depending on pH (9- 11) and mean residence time of suspension in a crystallizer (900- 3600 s). Under these conditions linear growth rate of struvite crystals (SIG MSMPR kinetic model) decreased 2-time with the increase in pH and 3-time with the elongation of mean residence time of crystal suspension from 7.11×10–9 m/s (pH 9, 900 s) to 1.65 × 10–9 m/s (pH 11, 3600 s). Nucleation rate varied within the 7.9 × 108- 1.8 × 1010 1/(sm3) limits. Struvite product of maximal linear size exceeded 100 m with 10 vol % of <3 m fraction corresponded to pH 9 and 3600 s