|Schematic diagram of the biomass-gasification-reforming system. Credit: ACS, Wang et al. Click to enlarge.|
A team from the Key Laboratory of Renewable Energy and Gas Hydrate, Guangzhou Institute of Energy Conversion, Chinese Academy of Sciences reports on a pilot-scale biomass-gasification-reforming system with optimized catalyst to produce synthesis gas for liquid fuel synthesis in the ACS journal Energy & Fuels.
Gasification of biomass in a fluidized-bed gasifier produces a raw fuel gas (a mixture of H2, CO, CO2, CH4, C2+, N2, H2O, etc.), accompanied by the formation of tar and fly ash. To fulfill the stoichiometric requirement of synthesis gas for the production of methanol, dimethyl ether, or Fischer-Tropsch diesel, the raw gas—which usually has a low H2/CO ratio—requires reforming of CH4, tar, and other light hydrocarbons and adjustment of the H2/CO ratio.
While commercial nickel-based catalysts are very effective in the elimination of biomass tar and its conversion to H2 and CO, the quick deactivation of the nickel-based catalyst by carbon deposition and sintering of active Ni particles seriously impedes its application. A number of novel catalyst approaches are being tried to address this issue.
The nickel-based catalysts in the form of monoliths with a honeycomb structure can deal with fuel gas containing particles...Corella and his groups designed an advanced two-layer-based monolithic reactor for catalytic hot gas cleaning. However, the Brunauer-Emmett-Teller (BET) surface area of the crude cordierite monolith is lower than that of a conventional porous support (e.g., γ-Al2O3, MgO, etc.), which lowers its activity for tar abatement.
In the present work, the bare monolith support was modified by washing with oxalic acid and loading ultrafine γ-Al2O3 to increase its pore volume and BET surface area. The NiO-MgO/ γ-Al2O3/cordierite monolithic catalysts were prepared by wet impregnation of NiO-MgO on the modified support.—Wang et al.
The researchers found that the NiO-MgO/γ-Al2O3/cordierite monolithic catalyst exhibited excellent catalytic performance, operating stability, and low pressure drop.
The pilot-scale biomass-gasification-reforming system was tested to be feasible for the production of biomass-based synthesis gas, which was suitable for the downstream liquid fuel synthesis. Under the conditions of ERT [total equivalence ratio] of 0.27 (ERfirst of 0.23, ERsecond of 0.02, and ERthird of 0.02) and S/B [steam/biomass] ratio of 0.4, the ideal synthesis gas was produced by oxygen-rich/steam gasification and an autothermal reforming process. The total content of H2 and CO reached 60 vol % with a H2/CO ratio of 0.9-1.0. The LHV and yield of synthesis gas were above 10 MJ N-1m-3 and 1.22 N m3/kgdry biomass, respectively. The total cold gas efficiency was above 82%. No serious alkali compound deposition on the surface of the catalyst was detected after the 60 h time-on-stream test.—Wang et al.
Tiejun Wang, Yuping Li, Chenguang Wang, Xinghua Zhang, Longlong Ma, Chuangzhi Wu (2011) Synthesis Gas Production with NiO-MgO/γ-Al2O3/Cordierite Monolithic Catalysts in a Pilot-Scale Biomass-Gasification-Reforming System. Energy & Fuels. doi: /10.1021/ef1015268