In reviewing gasification-related l

In reviewing gasification-related literature a problem common to all gasification technologies is the formation of tars. The problems related to tars in conventional synthesis gas applications are predominantly a result of their tendency to condense at the most inopportune points within the processes such as in fuel injectors, nozzles, gasifier air blowers, and producer gas cooling systems. Hassler and Nussbaumer in 1999 looked at various means of removing tars from synthesis gas so it could be used in an internal combustion engine (ICE). They found that no current technologies could consistently clean synthesis gas sufficiently for ICE applications. However the report indicates that more research needs to be conducted on other end use applications for synthesis gas such as gas turbines 7. Due in part to the diversity of gasification systems, research on various aspects of tars is somewhat unique to each system. Nearly every type of gasification system has been investigated to various degrees for tars. Milne et al. in a book published in 1998, reviewed some of the tar-related investigations of several gasification systems and compiled a helpful bibliography. They also reported that the nature and formation of tars is characteristic of the type of gasification technology used 8. Baker et al. in 1988 studied the characterization and treatment of tars in a variety of gasifier systems, and described tar yield as a function of temperature exposure. They found that at lower temperatures (400 to 500 °C) tar yield was generally within the range of 10% wt and higher for dry wood, and the yield reduced as temperatures increased up to 1000 °C 9.
Building upon the experiences of others in the biomass gasification field, this study aimed to determine the optimal conditions for gasification of wood pellets using fixed bed, cross draft gasification technology. The goal was to use gasification conditions to maximize the fuel value of the synthesis gas obtained, while minimizing the amounts of tars produced. The results obtained were used to indicate possible trends within the limits imposed for establishing statistical significance. The number of tests conducted was sufficient for observing possible trends and patterns in synthesis gas production and composition as gasification parameters were varied.