Effect of operating parameters for CO₂ capture from syngas of supercritical water gasification using K₂CO₃/-Al₂O₃ composite adsorbent

To increase the value of syngas produced by supercritical water gasification (SCWG), K2CO3/gamma-Al2O3 composite adsorbents were used to remove CO2 from crude syngas with high content of CO2. Two kinds of gamma-Al2O3 particles were evaluated and compared as K2CO3 carriers. Characterization using SEM and N-2 adsorption/desorption found that K2CO3/nano-gamma-Al2O3 had better dispersibility, larger specific surface area, and pore volume than K2CO3/normal gamma-Al2O3; this increased the chance of mass transfer between K2CO3 and CO2. The effects of K2CO3 load ratio, adsorption temperature, gas flow rate, and regeneration temperature on CO2 adsorption performance of K2CO3/nano-gamma-Al2O3 were also discussed. K2CO3/nano-gamma-Al2O3 had the optimum CO2 adsorption capacity of 2.029 mmol/g at 60 degrees C. Low gas flow rate was found to produce better CO2 adsorption performance. And the adsorbent could be fully regenerated by heating. Moreover, the adsorption of CO2 by K2CO3/nano-gamma-Al2O3 increased the heating value of the syngas from 8.56 MJ/Nm(3) to 13.51 MJ/Nm(3) and H-2 concentration from 41.6% to 75.65%. High selectivity of CO2/H-2 (23.5) and (CO2 +CO+CH4)/H-2 (17.6) from K2CO3/nano-gamma-Al2O3 revealed that it could be a suitable adsorbent for syngas upgrading.