Based on this information,  viscosity and mixing intensity should be sufficient to suspend particles being  dissolved.  Assuming particles are in suspension, increased mixing  intensity is not likely to reduce dissolving time.  Mixing intensity has  little effect on dissolving time, once all particles are suspended.   Reduced dissolving time will probably require increased temperature or reduced  particle sizes.
 
If you doubt these  recommendations, test the effect of increased mixing intensity by reducing  batch size to 35,000 liters. 

Same Mixer & Reduced  Volume  =  Increased Mixing Intensity
 

If operating at a reduced batch size (increased  mixing intensity) reduces dissolving time, then consider mixer  modifications.  Otherwise consider other process changes.