Energy Efficiency Improvement of Tea driers in Sri Lanka

Abstract

The tea industry is one of major agro-industrial sectors and it is the second largest black tea producer in the world. The thermal energy, produced by burning mainly firewood is used in processing of tea. The energy study done on combustion systems in Sri Lanka, mainly in tea drying, has found that moisture content (43 %) and large sizes of firewood used for combustion are directly related to the low combustion efficiency (60%) of the existing furnace. The National Engineering Research and Development Centre of Sri Lanka (NERDC) conducted studies at a tea factory to reduce thermal energy requirement for the tea dryer. Wood chips were introduced instead of wood logs, as a fuel for the drier. The pilot scale plant is in operation at the same factory, introducing wood chipper, new grate and controlled screw feeder to feed wood chips to the existing furnace, without modifying it. It maintained a constant temperature inside the dryer by sensing temperature inside the dryer and adjusting the motor speed accordingly of the screw feeder. Further, by introducing an agitator it prevented lumping up of wood chips on the grate at the end of the screw feeder. When producing of tea, the net saving of fuel wood is between 35- 45 %, which resulted due to, reduction of warming up period of the furnace with introduction of wood chips, screw feeder control in the system and less moisture content of wood. The other advantages are improvement of quality of tea produced due to constant temperature inside the dryer, reduction of utility of labour, less electricity consumption, reduction of environmental pollution, introduction of fast growing wood