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
- 1 Wroclaw University of Technology, Faculty of Chemistry, Wroclaw, Poland
- 2 Wroclaw University of Technology, Faculty of Chemistry, Wroclaw, Poland
- 3 Silesian University of Technology, Department of Chemical & Process Engineering, Gliwice, Poland
- 4 Wroclaw University of Technology, Faculty of Chemistry, Wroclaw, Poland
Abstract
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 L m 5.2-23.0 μm were produced depending on pH (9-11) and mean residence time of suspension in a crystallizer τ (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, τ900 s) to 1.65×10 -9 m/s (pH 11, τ3600 s). Nucleation rate varied within the 7.9×10 8 -1.8×10 10 1/(sm 3 ) limits. Struvite product of maximal linear size exceeded 100 μm with 10 vol. % of < 3 μm fraction corresponded to pH 9 and τ3600 s.
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