Effect of operating parameters for CO 2 capture from syngas of supercritical water gasification using K 2 CO 3 /γ-Al 2 O 3 composite adsorbent

To increase the value of syngas produced by supercritical water gasification (SCWG), K 2 CO 3 /γ-Al 2 O 3 composite adsorbents were used to remove CO 2 from crude syngas with high content of CO 2 . Two kinds of γ-Al 2 O 3 particles were evaluated and compared as K 2 CO 3 carriers. Characterization using SEM and N 2 adsorption/desorption found that K 2 CO 3 /nano-γ-Al 2 O 3 had better dispersibility, larger specific surface area, and pore volume than K 2 CO 3 /normal γ-Al 2 O 3 ; this increased the chance of mass transfer between K 2 CO 3 and CO 2 . The effects of K 2 CO 3 load ratio, adsorption temperature, gas flow rate, and regeneration temperature on CO 2 adsorption performance of K 2 CO 3 /nano-γ-Al 2 O 3 were also discussed. K 2 CO 3 /nano-γ-Al 2 O 3 had the optimum CO 2 adsorption capacity of 2.029 mmol/g at 60 °C. Low gas flow rate was found to produce better CO 2 adsorption performance. And the adsorbent could be fully regenerated by heating. Moreover, the adsorption of CO 2 by K 2 CO 3 /nano-γ-Al 2 O 3 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 CO 2 /H 2 (23.5) and (CO 2 + CO + CH 4 )/H 2 (17.6) from K 2 CO 3 /nano-γ-Al 2 O 3 revealed that it could be a suitable adsorbent for syngas upgrading. Graphical abstract