The Iso-Mix External Drive system (IMXD) is a special version of our highly successful Iso-Mix bottom entry dry hopping system that reduces hop retention time from days to hours. It is particularly suitable for use in the process of dry hopping beer in medium to large fermenter tanks.   

The IMXD mixer is rotated by an external motor connected to an internal shaft. As such, there is no contact between the circulating fluid and the mixer gears, which allows the system to handle high concentrations of solid matter, such as hop particles, in the circulating fluid. 

The IMXD mixer is located relatively low in the tank, typically within the cone section. This allows the mixer to be operated while the tank is being filled and emptied. For dry hopping, this configuration enables the mixer to maintain the hops in homogeneous suspension during transfer from the tank to downstream centrifugation. This helps maintain a constant load to the centrifuge resulting in optimal separation efficiency and performance.  

Because of its high tolerance to circulating particulates, including whole pellets, the IMXD dry hopping system provides flexibility in the choice of hops introduction to the fermenter. For example, hop pellets can be pre-slurried in a small tank at high solids concentrations and dosed into the circulation loop using a positive displacement pump, or whole hop pellets can be gas-blown directly into the fermenter with carbon dioxide.  

The IMXD dry hopping system can also be used to optimize the fermentation and cooling processes, as it maintains the yeast in suspension during the fermentation process. This provides optimal contact between yeast and fermentable sugars, and prevents yeast settling in the cone during fermentation. The typical benefits are reduced process time, less variation in process time and better and more consistent extract utilization. (The degree of improvement will depend on the yeast strains and the process conditions employed for each individual beer or brand formulation.) 

The Iso-Mix/IMXD system also helps maintain (or even improve) yeast health and viability. Any additional shear stress is more than compensated for by the reduction in yeast stress as the yeast remains in suspension during the entire fermentation. This avoids yeast stress associated with settling in the cone, which otherwise can starve the yeast of nutrients. The reduction in yeast stress can be seen in the decreased production of SO₂ and acetaldehyde (both of which are known by-products associated with yeast stress).