Abstract
Tar formation hinders the development of biomass gasification technologies. The use of pyrolytic char as a catalyst for removing tar has been widely investigated; its large specific surface area and pores distribution make it a good candidate for the cracking of heavy hydrocarbons. The present work assesses the catalytic activity of char from a commercial gasifier. Thermal degradation tests in N2 and in CO2 proved that the char is suitable for high-temperature applications (catalytic cracking) and showed release of CO and H2, which might affect the catalytic performance of the char when used for tar removal applications. For inspecting the potential of the char for tar removal, toluene was chosen as model tar. Through GC-FID, toluene removal efficiency and the amount of benzene produced from its decomposition were evaluated. Tests up to 1273 K resulted in tar removal efficiencies as high as 99.0%, and empty reactor tests allowed for discerning the effects of thermal and catalytic cracking. The catalytic activity of the char was more pronounced at 1173 K, as char increased the toluene removal efficiency from 39.9% (empty reactor) to 60.3%. The results confirmed that gasification char, like pyrolytic char, has a high potential for catalytic tar removal applications.
Highlights
The formation of tar during gasification of biomass is still a major hindrance for the development and application of gasification technologies on a wide scale
Char with large surface area and large pore volume, was collected from a commercial gasification system installed in South-Tyrol (Italy) and used for thermal degradation and tar catalytic cracking tests
The continuous analysis of gases exiting a lab-scale fixed-bed gasification reactor during char thermal degradation tests up to 1173 K in N2 and in CO2 was used to evaluate the production of gases in pyrolytic conditions and in gas mixtures mainly composed of
Summary
The formation of tar during gasification of biomass is still a major hindrance for the development and application of gasification technologies on a wide scale. At temperatures above 673 K, the tar can cause severe problems since it can undergo reactions that lead to formation and deposition of coke, which further causes fouling and plugging of the equipment components [1]. For this reason, the tar level requirements can be very strict, but they depend on the end-use application of the producer gas obtained from the gasification of biomass. With regards to the use of producer gas for the production of methanol or synthetic diesel through Fischer-Tropsch (FT) synthesis, Tijmensen et al [8] recommend the complete removal of tar
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