13 OCT 2011
New low-cost permeate powder process
Traditional permeate powder production includes evaporation with flash cooling followed by a time consuming crystallization before the concentrate is finally spray dried, a process requiring a lot of energy, expensive processing equipment and building costs.
The new TIXOTHERM™ process developed by Niro duly considers all the drawbacks of the traditional process, as it is now possible to produce permeate powder without crystallization of the concentrate and furthermore eliminate the spray drying process.
Whey from cheese production still contains valuable nutrients like whey proteins which can be separated in a membrane filtration plant as WPC/I. The remaining permeate contains lactose, salts and a lot of water. When the permeate is processed into powder, the water needs to be removed.
Current practice is evaporation to around 60% total solids followed by flash cooling and a batch-wise crystallization process, which takes 16-20 hours prior to the final spray drying. As the value of the end product - the permeate powder - is low, and the investment costs and energy consumption for the processing are high, the production costs will be covered with only a small profit margin.
Many attempts have been made to develop a Low Cost process to convert the permeate into a powder. Niro has of course also done pioneering work within this field and takes pride in introducing the TIXOTHERM™ Process (patent pending). The new process is designed to operate at low temperatures to avoid discolouring of the product during the process.
The TIXOTHERM™ process (see flow sheet) is based on well-known unit operations within the Food & Dairy industry. In this new process those have been adapted to cope with the nature and physical behaviour of this product, which, when concentrated, exhibits tixotropic properties. In the TIXOTHERM™ process the permeate is evaporated in a conventional falling film evaporator with either thermal or mechanical vapour recompression to about 60% total solids. To ensure a trouble-free 20 hour operation of the evaporator, a decalcification process should be applied upstream to the membrane filtration.
The next processing step is a combined paddle evaporator/dryer, the ROSINAIRE™, where the solids content in the concentrate is further increased to 85% total solids. Together with an air current - to remove the vapour - and the evaporation itself, the temperature of the product is kept low to avoid discolouring. In the ROSINAIRE™ the lactose becomes supersaturated and a rapid crystallization starts. After the ROSINAIRE™ the paste-like concentrate is discharged into the next processing step - the cooling conveyor.
In the cooling conveyor the lactose crystallization continues and approaches 100%. Due to the tixotropic behaviour of the concentrate and the slow movement of the auger, the product changes nature, and at discharge it exhibits a texture suitable for fluid bed drying.
The final step in the TIXOTHERM™ process is carried out in Niro's combined back-mix/plug-flow fluid bed known from lactose production. Here the remaining free water is evaporated, and the powder is finally cooled to the desired temperature. The powder may finally be milled to the desired particle size.
This TIXOTHERM™ process as described above results in a direct saving of more than 30% energy and a reduction of up to 50% of building volume. The investment costs of the processing equipment are also attractive compared to the traditional process.