Preserving Aroma Substances in a Better Way
The combination of the “sluice-vessel-sluice” is placed threefold side by side. In the event of one combination failing or for maintenance purposes the quasi-continuous process control can be continued without any interruption. The transition-sluice then fulfills the most demanding requirement. This procedure is to ensure the smooth transition of the frozen material of –50 °C (–58 °F) to the vacuum. The ground and frozen coffee is collected onto the upper product-valve until it reaches a specified quantity, then this product-tight valve opens, the frozen coffee drops in the connecting pipe on the vacuum-valve which is placed under vacuum until it reaches the vacuum of the disc-dryer of 0.3 mbar. The lower vacuum-tight valve is opened and the coffee leaves the freezing chamber and is collected in a silo.
This absolutely reliable tightness and robustness of the Kammerer-sluice avoids any additional backing-up of the coffee into the freezing chamber. The plant is set up in a way that a backing-up directly leads to an automatic switching-off of the plant. In the following step the ice in the coffee granules has got to be sublimated under vacuum.
Drying of the coffee in the vacuum disc dryer: The silo is on top of the vacuum disc dryer and serves as a portion-divider. It ensures a continuous amount of the product falling onto the individual disc in the vacuum dryer. These discs, approx. 30 in number, are heated to 45 °C (113 °F) in the upper section, increasing to a temperature of 125 °C (257 °F) as it reaches to lower section.
The coffee granules are dispersed from disc to disc. Simultaneously the coffee is mixed, while the moisture is extracted. Filters are attached directly to the disc dryers which separate impurities and dust from the coffee. At the back condensers collect the moisture at this point. At the bottom of the discs silos are built in making it possible to have a final quality control procedure before the packing of the coffee granules. Kammerer-sluices are attached directly underneath for a final discharge. This enables the discharge of the purified instant coffee granules ready for use after leaving the silos.