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Particle suspension in bioreactor 

In this work, we modeled the impact of injection location on mixing time to uniformly distribute and suspend the particles in a mechanically agitated reactor. Mixing time is the minimum time required for the mixers to disperse the particles injected into the reactor. For the purpose of mixing time study, the particles were injected for the infinitesimal period and the distribution of particles at different locations of the reactor was measured. Uniform suspension of particles is critical in avoiding particle sedimentation due to inadequate mixing of the reactor, which is the cause of dead volumes or short circuit flow. 

Particles inject at the top, front view

Particles inject at the bottom, front view

Particles inject at the bottom, isometric view

Effect of fluid rheology on bioreactors mixing time

Bioreactor mixing time for Newtonian fluid (water) and non-Newtonian fluid (sludge) were simulated and validated experimentally by pulsing the tracer at ah1 and sampling the tracer concentration at the indicated points in the figure below.

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Newtonian fluid mixing time

Newtonian fluid (water) viscosity at 35 degrees 

95% homogeneity achieved in less than 60 minutes at 14 rpm mixing speed 

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Tracer mass fraction distribution with time at different sampling locations: Newtonian fluid 

Non-Newtonian fluid mixing time

  • Non-Newtonian fluid viscosity defined according to the Herschel-Bulkley viscosity model 

  • 95% homogeneity achieved after 120 minutes at 14 rpm mixing speed

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Tracer mass fraction distribution with time at different sampling locations: non-Newtonian fluid 

Newtonian fluid mixing time animation in a real-time

Non-Newtonian fluid mixing time animation in a real-time

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