Development of a high yield and low cycle time biomass char production system

A prototype of biomass char production system with the potential of high charcoal/fixed carbon yield and low cycle time is developed in the current study. The prototype biomass char production system comprises of a solid biomass heat conversion unit, a carbonizer and a connecting pipe. The heat conversion unit is an updraft fixed bed gasifier with an embedded combustor fueled by solid biomass for generating high temperature flue gas. The carbonizer is a variation of Brazilian beehive charcoal kiln. The connecting pipe transports the hot and oxygen free flue gas from the gasifier to the carbonizer. The flue gas is radially distributed in the floor of the Brazilian beehive kiln through many small openings on the surface of a ring pipe.In the current study the syngas generated from the updraft fixed bed gasifier is fully burnt in the embedded combustor. This design results in very high temperature and virtually oxygen free flue gas from solid biomass. The hot and reductive flue gas is forced to circulate in the kiln to carbonize the biomass charge. Temperature distribution in the carbonizer is found to be much more uniform than any conventional charcoal kiln. Higher final carbonization temperature in the kiln is also realizable without the sacrifice of any charge in the current approach. All the solid biomass in the kiln is converted into high quality charcoal with very high fixed carbon percentage and solid biomass burnt to ash is barely discernable. The biomass char yield gradually increases by more than 15 percentage points. The carbonization time is effectively reduced to 4 h compared favorably with the conventional 160 h.