CO₂ utilization for combined gasification and sorption enhanced water-gas shift for syngas production of biochar

Abstract

Searching for alternative renewable energy to serve high demand of energy consumption has been of interest for decades. However, the production of energy comes with an emission of large amount of CO2, the main cause of global warming problem. As a consequence, improvement of energy production process in terms of increasing high efficiency and reducing CO2 emission are required [1]. This research verified the combined systems: biochar gasification and sorption-enhanced water gas shift reaction for the production of synthesis gas. The effect of calcium precursor on CaO-based sorbents, type of metal on multifunctional materials, and amount of co-feed CO2 as gasifying agent on process performances were focused on this work. Fixed-bed reactors were used for both gasification and sorption-enhanced water-gas shift experiments. Performances of the system were analyzed in terms of %biochar conversion, H2/CO ratio, and CO2 emission. The temperature used in the gasification process was fixed at 900°C and sorption-enhanced water-gas shift was 600°C at 1 atm. The results showed the sorbent CaO/Caj2Alj4O33 derived from calcium nitrate displayed the best performance for CO2 capture, whose CO2 capture capacity is 0.34 gCO2/g sorbent at 30%CO2v/v at 600°C. For the combined gasification and sorption-enhanced water-gas shift reaction, 98% biochar conversion can be obtained. Ni/CaO-Caj2Ali4O33 offered higher H2/CO ratio and CO2 emission when compared to Cu/CaO-Ca12Al14O33 at fixed feed molar ratio of H2O:CO2:O2:C = 0.5:0.5:0.125:1. The utilization of CO2 as gasifying agent at feed molar ratio of H2O:CO2:O2:C = 0.5:0.1:0.125:1 demonstrated the reduction of CO2 emission with the production of H2/CO ratio = 0.23.