Catalytic Tar Conversion in Two Different Hot Syngas Cleaning Systems

Abstract

Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes and causes fouling of system components and pipework. Therefore, an efficient tar conversion in the product gas is a key step of effective and reliable syngas production. One of the most promising approaches is the catalytic decomposition of the tar species combined with hot syngas cleaning. The catalyst must be able to convert tar components in the synthesis gas at temperatures of around 700 °C downstream of the gasifier without preheating. A Ni-based doped catalyst with high activity in tar conversion was developed and characterized in detail. An appropriate composition of transition metals was applied to minimize catalyst coking. Precious metals (Pt, Pd, Rh, or a combination of two of them) were added to the catalyst in small quantities. Depending on the hot gas cleaning system used, both transition metals and precious metals were co-impregnated on pellets or on a ceramic filter material. In the case of a pelletized-type catalyst, the hot gas cleaning system revealed a conversion above 80% for 70 and 110 h. The catalyst composed of Ni, Fe, and Cr oxides, promoted with Pt and impregnated on a ceramic fiber filter composed of Al2O3(44%)/SiO2(56%), was the most active catalyst for a compact cleaning system. This catalyst was catalytically active with a naphthalene conversion of around 93% over 95 h without catalyst deactivation.

Syngas Fermentation: Cleaning of Syngas as a Critical Stage in Fermentation Performance

“…Therefore, a global optimization of the process is needed [238] to attain low levels of contaminants without the requirement of costly cleaning processes. Although efforts are being made with successful performance, as demonstrated by Hai et al [210], Frilund et al [208], and Straczewski et al [239]. Industrial application of the whole integrated approach still seems far away due to other alternatives having better performance or demonstrating to be much closer to a commercial scale, as it would be integrating gasification and energy production by the use of solid oxide fuel cells [240,241], gas turbines [242,243], CHP engines, and even its fermentation homologous for the production of methane, since this small molecule can be used as fuel, having greater energetic density than carbon monoxide and hydrogen and does not need a phase separation, as is the case of producing acids of alcohols.…”