Modified Iwate kiln for production of good quality charcoal and high volume of wood vinegar

The modified Iwate kiln size is 3 m in length and 1.7 m in height. Refractory brick, red clay brick, and cement were used to construct the kiln. The modified Iwate kiln is different from the general Iwate kiln in terms of an added part, i.e., a heat distribution pipe installed inside the kiln. The steel pipe plays an important role in heat flow in the kiln. The cylindrical-shaped pipe has slots at the top and the bottom part for heat to pass from the heat source to biomass. The heat distribution inside the kiln was monitored by thermometers at six positions in three different zones of the kiln, i.e., the front part, the middle part, and the back part. The result showed that all three parts provided the same temperatures, both on the top and bottom parts of the kiln. Bamboo and mango wood were used to test the kiln efficiency of charcoal production. Using 1684 kg of bamboo, the output was 292 kg of bamboo charcoal and 909 kg of crude bamboo vinegar; mango wood charcoal production used 2984 kg of mango wood, producing 550 kg of mango wood charcoal and 1212 kg of crude mango wood vinegar. Both types of charcoal have good quality, with a heat value of 31 MJ/kg. The energy conversion efficiency of the modified Iwate kiln was 41–45 %.