18 September 2008. JND have just completed the design and build of a Rotary Louvre pilot cocoa nib dryer/roaster at their UK facility for a major US chocolate confectionary manufacturer. The unit complies with a stringent clean specification and is complete with a fully automatic computer controlled system enabling full product profiling to be monitored during the process which will allow the drying/roasting kinetics to be better understood when scaling up to production equipment.
JND’s Thermal Processing division have been providing solutions to the food processing industry for over a century processing a wide range of foodstuffs such as for sugar, cous-cous and bread crumbs. JND are specialists in the Continuous conditioning, drying and roasting of cocoa nibs and beans. Most of these installations have been the Rotary Louvre design or, as plant emission control becomes increasingly more important, the new Indirect Cocoa Dryer & Roaster has become an attractive alternative.
JND Rotary Louvre nib dryer/roaster which was built at the JND’s Worksop facility
About Rotary Louvre Drying and Roasting:
The Rotary Louvre unit is often described as a mechanically assisted semi-fluidised bed system. Although externally it looks very much like a conventional rotary dryer, internally its action is totally different. It comprises an outer cylindrical shell within which longitudinal air channels are formed by a series of radial louvres fitted along the inside of the shell. These channels are covered by overlapping tangential louvres to form an inner drum on which the bed of material is carried creating a cross-flow system where all the inlet gases have the same effect regardless of how far down the machine they enter the bed. The bed of material is continuously turned by the drum rotation.
Process air can be heated by a variety of methods (usually in-duct gas burners) and is channelled through a stationary head plate. This means that, as the air channels pass the ducts in the head plate, air is only admitted to those channels that are in position beneath the bed. It then passes through the louvres and up through the bed partially fluidizing it. The air flow through the Rotary Louvre Dryer and Roaster is cross-flow relative to the bed, the hot gas is moving up through the bed as the material moves along the drum. This means that at any point along the length of a zone the temperature, humidity and flow of the hot gas entering the bed is constant as shown in the diagram below.
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