Scale-up effect on the rate of contact nucleation caused by collisions of crystals with an impeller

Abstract

This paper proposes a rate equation of contact nucleation caused by crystal–impeller collision J c-i=k′ · p · n s · d N p · u N+1 · D -4 b, where k′ is the coefficient, p the impeller blade number, n s the crystal number, d p the crystal size, u the tip speed of an impeller, and D b the impeller blade size. Contact nucleation rates of potassium alum measured in three stirred tanks of different size (1.57×10 -3, 6.28×10 -3, 5.02×10 -2 m 3 of working volume, P=4, 6, n s=10–2000, d p=3.585×10 -4–1.545×10 -3 m, u=0.817–2.136 m/s, D b=9.45×10 -3, 1.5×10 -2, 3.0×10 -2 m) were successfully explained by this equation when the value of an unknown parameter ( N) was equal to 3. The meaning of N=3 is also discussed using the measured frequencies of particle–impeller contact (non-nucleation experiments).