Analysis of dominant tars production kinetics at low reaction temperature using small scale downdraft gasifier with wood pellet and reaction kinetics simulation

• Small-scale gasifier operation results under realistic condition are shown. • Small-scale gasifier has low reaction temperature. • Kinetic models for tar production at low reaction temperature are suggested. Wood biomass with low abundance density is best utilized in small-capacity processing equipment. In small-capacity pyrolysis equipment, as the impact of heat loss is significant, the effect of low-temperature reactions is large. At low temperatures, the composition of tar, which causes mechanical damage, differs greatly. However, there are few cases in which the impact of these low-temperature reactions has been properly considered based on results obtained under realistic operating conditions. Therefore, in this paper, the main components of tar (acetic acid, benzene, phenol, and naphthalene) were measured experimentally and compared with the calculation results of a conventional kinetic model using CHEMKIN with the CRECK model applied. For the experiment, a self-made downdraft gasifier (self-heating type, without special insulation) using commercially available wood pellets (log cedar) was used. The results showed a significant difference between the experimental and calculated values for benzene density in the low reaction temperature range below 800 °C. This low-density phenomenon should be caused by 1) low reaction temperature, 2) short residence time, and 3) insufficient low-temperature reaction kinetics model.