CSIR – National Institute for Interdisciplinary Science and Technology (NIIST)

Council of Scientific & Industrial Research (CSIR), Govt.Of India Thiruvananthapuram.

Development of reverse flow natural convection driers and cottage level processing for rural development

Subsequent to the successful and wide spread use of RRL-T NC Driers for the drying of various rural agricultural products such as coconuts (for making copra), rubber sheets, spices, various fruits etc., a RSWNET project was sanctioned by CSIR for expanding and popularising the use of such driers for more materials such as ground nuts, cardamom, reisins, mango bar, pappad etc. Accordingly, during this period, efforts were initiated to develop a drier and a process for drying field fresh ground nut to a marketable material having reduced moisture content.

Based on the successful cylindrical design, same was scaled up to make a commercial drier having a volume of 3600 litres. This drier can dry 500 Kilograms of ground nut in a single batch. Two tests were conducted with this drier which showed very good reproducibility. Mixing of the ground nut during drying was achieved by regular timed rotation of the trommel using a hand-operated wheel. Two detachable furnace units are used to generate hot air. A fuel mix consisting of firewood, coconut husk and coconut shells was used for generating hot air for the reverse flow heating and drying. Efforts are being made to shift the drier to the field location for farmers’ trials. During 2009-10, a laboratory pappad drier for cottage level industries was also designed and fabricated in the Laboratory. A few number of pappd drying experiments were also conducted taking help from the traditional Pappad makers. Tests showed that keeping a temperature of 40-45°C in the drying chamber, pappad can be dried within 6 minutes against the conventional sun drying which takes 10-12 minutes. Based on this data, effort is being made to re-design a more efficient drier with more effective hot air distribution.