Overview and Essentials of Biomass Gasification Technologies and Their Catalytic Cleaning Methods

Obtaining a tar-free biosyngas from biomass gasification processes has been the subject of many studies in the past 2 decades, and it still remains the major technologic and economic challenge. Unfortunately, the countless publications about gasification technologies and different techniques permitting reduction of the tar present at the outlet of gasifier reactors usually confuse inexperienced persons who attempt to further research this subject. More than presenting the basis of biomass gasification technologies and positioning them among other bioenergies, this work mainly aims at reviewing and comparing the different methods developed in order to produce a tar-free biosyngas. In this way, biosyngas quality improvement can be obtained through different operating processes such as reactor designs, gasifying ratios, feedstock, temperature, and space ratio. Since catalytic destruction has proved to be one of the most convenient and efficient ways to eliminate undesirable tars, an important part of this work also highlights the catalytic and deactivating phenomena involved. Furthermore, this work takes inventory of numerous studies conducted to understand the influence of different properties, especially supports and active site compositions, on the tar reforming activities and lifetime of catalyst materials. Thus, this review aims at summarizing basic and more recent improvements applied to biomass gasification processes and catalytic syngas purification.