Using Reverse Osmosis to Preconcentrate Whey

Reverse osmosis (RO) is recognized as a cost effective means to concentrate whey and can be used to pre-concentrate whey before final concentration in an evaporator. At a cheese and whey processing facility, RO was retrofitted to a 5-effect TVR evaporator in the mid 1990’s to increase capacity. However, at the time the RO discharge was set to only 8-percent, far less than is typically possible. Management was interested in optimizing the current RO system or upgrading to reduce overall cost of whey concentration.

To answer questions concerning economic and technical feasibility, a detailed engineering evaluation of the RO system and multi-effect TVR evaporator was performed. The evaluation included computer simulation, power metering and field data collection to build confidence in the results. The major findings were:

  • The capacity of the existing RO unit was limited by the booster pump power and staging, but the final concentration was increased 3/4-percent, resulting in reduced evaporator steam use.
  • Energy requirements for concentration were found to be 24-Btu/lb (heat equivalent) for the RO unit and 131-Btu/lb for the 5-effect TVR evaporator. This provided the basis for further consideration of upgrading the RO system based on the facility capital plan.
  • The multi-nozzle TVR was operating at less than design efficiency, most likely because evaporator requirements had changed over the years due to increased production and use of RO