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The effects of H 2 /CO ratio in syngas from a biomass gasifier, the type of a Fischer-Tropsch (FT) catalyst, addition of a reformer in a recycle mode, efficiency of CO 2 removal, and co-feeding of biomass and natural gas on the overall thermal efficiency and costs for the production of FT liquid fuels from the biomass-derived syngas were analyzed using an Aspen Plus ®-based process model. The overall thermal efficiency for biomass-fed processes was in a range of 41.3-45.5%. A

13Silica and alumina were used as structural promoters to increase the catalytic activity of a co-14 precipitated Fe-Cu-K catalyst for the CO 2 and CO hydrogenation during Fischer-Tropsch (FT) 15 synthesis. The doubly-promoted Fe-Cu-K-Si-Al catalyst achieved higher CO and CO 2 16 conversions than the Fe-Cu-K catalyst and singly-promoted Fe-Cu-K-Al and Fe-Cu-K-Si 17 catalysts. The CO and CO 2 conversions of the syngas with 54%H 2 /10%CO/29%CO 2 /7%N 2 over 18 the doubly-promoted catalyst were 88.3% and 25.2%, respectively, compared to 81.8% and 19 18.5% for the Fe-Cu-K catalyst. In this case, the C 5+ selectivity of the doubly-promoted catalyst 20 was 71.9%, which was slightly lower than 75.5% for the Fe-Cu-K catalyst. The CO 2 was 21 converted to hydrocarbons using the doubly-promoted catalyst when the CO 2 /(CO+CO 2 ) ratio 22 © 2015. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ 2 was higher than 0.35 for H 2 -balanced syngas at H 2 /(2CO+3CO 2 )=1.0, and 0.5 for H 2 -deficient 23 syngas at H 2 /(2CO+3CO 2 )=0.5). The increase of hydrogen content in the syngas increased the 24 methane selectivity at the expense of decrease in the liquid hydrocarbon selectivity. 25 26

A sequential modular simulation (SMS) approach was used to simulate hydrodynamics and detailed kinetics of a fluidized-bed biomass gasifier in Aspen Plus. The kinetics of tar cracking reactions was taken into account in the simulation. The effects of operating conditions including temperature, equivalence ratio (ER), and steam-to-biomass ratio (SBR) on the composition and the lower heating value (LHV) of the effluent gas were studied and compared with experimental data. The model predictions well agreed with the experimental data. The increase of the bed temperature significantly decreased the tar content and increased the hydrogen content of the product gas. At ER = 0.3, the increase of the temperature from 973 K to 1123 K resulted in the increase of H 2 molar concentration in the product gas from 7.6% to 11.3% and CO molar concentration from 13.1% to 17.0%. At a temperature of 1073 K, the optimum ER value was 0.3 and the increase in ER from 0.2 to up to 0.3 increased the amount of fuel gases but further increases in ER shifted the system kinetics toward the combustion regime. At 1073 K and ER = 0.3, with an increase in SBR from 0 to 1.0, H 2 and CO 2 concentrations increased from 9.3% and 13.3% to 10.8% and 14.7%, respectively, and CO concentration decreased from 15.8% to 12.9%. The analysis showed the SMS model with four stages gives the most satisfactory predictions, via comparison with the experimental data.

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