High-purity hydrogen production with in situ CO2 capture based on biomass gasification

Tar formation and CO2 emission represent the strongest barrier for use of gasification technology for biomass conversion, whereas sufficing for both is only possible with expensive physical methods and further chemical processing. The use of CaO as a CO2 sorbent within an advanced high-temperature gasification system is able to achieve efficient cracking of the tars to the primary syngas with low emissions. The present work aims to propose a semi-kinetic model on the basis of an Aspen Plus model to describe specific catalytic behavior of calcium oxide on the gasification of rice husk. There has also been an attempt to validate the developed model by means of an experimental study and explore the influence of minerals within ash on gasification characteristics, since kinetic data are scarce in the literature. Effects of some critical parameters such as gasification temperature, equivalence ratio (ER), and steam/biomass ratio (S/B) on hydrogen yield and CO2 absorption ratio have been studied. Results showed that CO2 absorption ratio ascends as CaO loading ratio increases, then to continuously decrease due to a significant reduction in endothermic nature of the Boudouard reaction. When ER ascended from 0.15 to 0.25, syngas yield and hydrogen yield did the same thing, increasing from 2.1 to 2.45 Nm3/kg biomass and 37-41 g/kg biomass respectively. In the second stage, ER undertook a rise from 0.25 to 0.3 where gas caloric value and hydrogen yield were decreased.