New developments in sugar drying

摘要

1. The combination of rotary dryer and fluidized-bed cooler unites the advantages of the two processes and reduces and/or eliminates their respective disadvantages. 2. The overlay of convective cooling by contact cooling as practiced in the use of integrated cooling elements in the fluidized-bed unit allows for a considerable reduction of the air quantity as compared with conventional fluidized-bed units. 3. This leads to a drastic reduction of the consumption of electrical energy in such plants along with a reduction of the screen bottom surface of the fluidized-bed unit. This in turn has a positive effect on the space required. Moreover, ancillary equipment such as fans, filters, etc., can partially be dispensed with, or at least reduced in capacity. 4. Heating steam can be saved by complete reutilization of the heated cooling air as part of the drying air. A first industrial application of this new version is currently being realized at a German sugar factory. It goes without saying that the decision for or against a certain system also requires the evaluation of aspects other than energy efficiency, for example investment costs, maintenance requirements, space availability, etc. The assessment of the energy efficiency also depends on the respective location, as different costs for electrical energy and steam may naturally lead to a shift in one direction or other. Moreover, climatic conditions at the location will also have an influence on the decision, as the absolute temperature level and the ambient air humidity will vary the efficiency of plant components. Under certain favourable conditions, components (like chillers) may also be dispensed with. For the above reasons, a precise knowledge of the specific conditions and the specific requirements of the user is an absolute must for the correct choice of the optimum drying and cooling process or system. New developments in the sugar drying and cooling sector open interesting possibilities for planning of new plants and for replacement and/or expansion projects. For these, the energy efficiency as an essential decisive aspect is becoming ever more important.