Solar, Biomass and Hybrid Dryers - BioEnergy Discussion Lists

Figure 7.5. First, the base plate, part 'A' is placed on a levelled surface. The outer part'B' is placed on it. Finally, the plate with 19 holes, 'C' is placed over the bottom plate'A', in such a way that it rests on pins supports as shown in the figure.Figure 7.7: Drying of molded honeycomb briquettesThe mould set is filled with the mixture and after filling up to the brim, the top layeris levelled with a flat wooden piece. Now, holding the handles of both part A andpart B, the mould is turned upside down on to a firm ground. The mould is removedand the briquette is allowed to dry in the sun for 2-3 days. These beehive orhoneycomb briquettes are superior to other briquette shapes as the honeycombstructure allows better contact between the fuel and air during combustion.Heat ExchangerA heat exchanger transfers heat from the hot flue gas from the biomass stove to thedrying air entering the drying chamber through the solar collector. The heatexchanger, made of 24 SGW aluminum sheet, is fitted above the level of the solarcollector’s air outlet. It is of fin and tube design, with a rectangular tube, on whichaluminum fins are attached to enhance the heat transfer surface area. Hot flue gasesfrom the biomass stove enter the heat exchanger at one side, and leave through achimney at the other side. Process air which gets heated up by the heat exchangersurface, flows up through the trays which hold the products to be dried.The dryer will be useful for commercial scale users for processing products such asfruits, vegetables and fish. The dryer has been tested for drying products such asradish, carrot, ginger and mushroom. As uninterrupted continuous drying ispossible with this type of dryer, the quality of the dried product is better than thatdried in the open sun or in the solar dryer.43