Advantages & disadvantages
There are four (4) modes of heat transfer: conduction, convection, radiation, and evaporative cooling. In the furnace design this operate singly or in combination.
Basically there are two furnace designs in terms of heat transfer: direct fired and indirectly fired. The inclined grate rice hull furnace is a direct fired furnace where the rice hull is burned on the step grates and the hot air together with the smoke, combustion gases, and fly ash are sucked and forced to pass through the layer of grains. While the indirectly fired furnace use a heat exchanger in contact with the burning biomass or fossil fuel and the clean heated air from the heat exchanger is sucked and forced through the grain. Furnace with heat exchanger is more expensive to construct, higher R&M, need more fuel, higher heat loss, and lower thermal efficiency.
Innovations of the direct fired rice hull furnace include the provision of rice hull agitator, small blower for secondary air supply, and a motor-driven auger to remove burnt rice hull resulting to more moving parts and higher R&M cost. In the latest rice hull furnace design these 3 functions are combined into one. Hence, less moving parts & less maintenance cost. The rice hull is burned on a grate, the flue gas is sucked down and completely burned before it is sucked into the dryer plenum. Here's a link to it's video in operation. https://www.youtube.com/watch?v=LzSIuyaP004 The latest commercial model of this furnace features a knckdown design for ease of handling. The various operational issues of the 2012 IRRI design have been addressed. For more information please contact Engr. Paterno C. Borlagdan. Email: email@example.com Mobile: +639363748716, +639284117709 (Whatsapp).