Converting Waste Agricultural Biomass into a Resource - UNEP

are given in Table 7.1. The dimensions of the drying chamber are optimized
for convenient loading and unloading of the products. The drying chamber
was also partitioned to minimize heat losses during handling of the product
during the drying process.
Design Details
The hybrid dryer is a modified version of the solar cabinet dryer described in
Package 5. The design of the flat plate solar collector, drying chamber, and
supporting stand are similar to that already presented in Package 5. The
biomass stove-heat exchanger-chimney assembly is the only addition to the
solar cabinet dryer. Therefore, only the design details of biomass stove-heat
exchanger-chimney assembly is described here.
Biomass Stove
Honeycomb charcoal-briquettes are a popular and cheap cooking fuel in
certain parts of rural Nepal. The briquettes are made by mixing charcoal and
clay and moulding cylindrical briquettes with a honeycomb-like cross section.
A stove which can utilise the honeycomb briquettes to supply hot air for drying
was therefore thought to be an attractive option for solar-biomass hybrid
dryers. This stove was developed at AIT under the RETs in Asia programme
within a fellowship study by RECAST, Nepal. The honeycomb briquette stove
was found to provide hot air a steady temperature of 50-60°C inside the
drying chamber. Only minimum supervision was needed for the stove during
operation. The dried products were also of excellent quality due to indirect
contact drying.
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