Development of a Rice Husk Fired Biomass Stove for Cooking, Water and Space Heating

Rice husk, a major by-product of the rice-milling industries, accounts for 20% by weight of rice paddy and is abundantly available in the rice processing industries. This potential energy source is usually burnt off in many rice industries to create space by farms that are in dire need of thermal energy for airand water heating as well asfor electricity generation. A simple energy efficient rice husk fired stove was developed for space and water heating as well as for cooking.The stove consisted of three closed concentric cast iron cylinders with the innermost being the combustion chamber that supplies heat directly onto a cooking cast iron plate. Waste heat from the innermost cylinder is extracted from the second cylinder using a forced convection 12 volt powered compressor and transferred to the heating space. A stainless steel heat exchanger brings in cold water into the combustion chamber and conveys warm water away from the stove to a storage tank. The outermost cylinder is heavily lagged to prevent heat losses. Rice husk is introduced into the innermost cylinder through a rectangular supply port that has a cover. The inner most cylinder has a grate under for ash exit and anexhaust pipe for smoke exit; Preliminary tests indicated that complete combustion of 1 kg of rice husk with calorific value of 12.6 MJ in the furnace of the stove took 30 minutes.The heat transfer through the cooking plate, the heat exchanger by water and air were 25513.33 J/s, 11486.45 J/s, and 10235.32 J/s respectively. Over 140g of the rice husk supplied 1.75 MJ of heat to the 3 sections. The maximum temperature reached in the furnace was 556.5 °C. The temperatures of the hot air and water from the stove rose up 116.5 °C and 105°C respectively. The burning rate of the husk in the furnace was 1.6 kg/hr. No premechanical treatment of rice husk is required for the stove to function properly. Keywords; Biomass stoves, rice husk, water heating, space heating, agricultural waste.