Gasification of agricultural residues in a demonstrative plant: Vine pruning and rice husks

Abstract

Tests with vine pruning and rice husks were carried out in a demonstrative downdraft gasifier (350kW), to prove the reactor operability, quantify the plant efficiency, and thus extend the range of potential energy feedstocks. Pressure drops, syngas flow rate and composition were monitored to study the material and energy balances, and performance indexes. Interesting results were obtained for vine pruning (syngas heating value 5.7MJ/m(3), equivalent ratio 0.26, cold gas efficiency 65%, power efficiency 21%), while poorer values were obtained for rice husks (syngas heating value 2.5-3.8MJ/m(3), equivalent ratio 0.4, cold gas efficiency 31-42%, power efficiency 10-13%). The work contains also a comparison with previous results (wood pellets, corn cobs, Miscanthus) for defining an operating diagram, based on material density and particle size and shape, and the critical zones (reactor obstruction, bridging, no bed buildup, combustion regime)