Highest Possible Lamina Expansion

Garbuio Dickinson have been associated with the DIET process since the 1980’s, and have worked together with Toromont Energy Systems and their predecessors to implement many successful DIET projects worldwide.

The DIET process comprises two main areas of equipment and expertise: the ‘cold end’ or CO2 handling systems which is Toromont’s expertise, and the ‘Hot end’ or tobacco expansion and drying which is Garbuio Dickinson’s.

Cut tobacco from a conventional primary process is fed to the CO2 impregnation system in precisely weighed sub-batches, and impregnated with liquid CO2 at pressures of 30 - 35 Bar. The impregnators are filled with liquid CO2 before being drained, depressurised and the residual gaseous CO2 removed and recovered by re-compression.

The frozen tobacco is now discharged from the impregnators, and passes through special opening doffers to a buffer silo. It is then fed at a controlled mass flow by means of a special low-temperature Weycon to the infeed of a specially designed air dryer in which the frozen tobacco is subject to a process gas stream consisting mainly of superheated steam. This causes the ‘dry ice’ or solid CO2 contained within the tobacco cellular matrix to change state from the solid to the gaseous phase (sublimation). Due to the fact that the volume of gaseous CO2 is vastly greater than the volume of dry ice, the tobacco is expanded, in some cases to double its original volume depending on the nature of the tobacco.

Following expansion, the product moisture is corrected to the desired final value if necessary, and unwanted heavy items (e.g. stems and other contaminants) removed by classification in an Elutriator (see other web page for more details of this product).

The DIET material may then be filled into bins or boxes for onward storage and transportation, or may be conveyed to silos ready for Addback in the Primary process.