Co-gasification of coal-biomass blended char with CO_2 at temperatures of 900-1100℃

摘要

Co-gasified biomass and coal can be considered a potential fuel base for gasification and offers the advantage of a reduction in CO_2 emissions. In addition, use of biomass could contribute to a reduction in fossil fuel dependency. In this study, a mixture of coal and biomass was placed in a lab-scale tube furnace and co-pyrolyzed to be transformed to a char under nitrogen atmosphere. Three mass ratios of coal and biomass, 4:1,1:1, and 1:4, were tested, and then each char was co-gasified with CO_2 after the furnace was isothermally maintained. Three isothermal conditions of 900,1000, and 1100 ℃ were tested. In every test the carbon conversion ratio was calculated from the CO concentration measured at the exit of the furnace. The reactivity of char was improved with an increasing amount of biomass owing to the catalytic effect of the alkaline minerals included in the biomass. In addition, reactive synergy was observed with the biomass blended char and increased with the amount of biomass utilized. The volume reaction model (VRM), shrinking core model (SCM), and random pore model (RPM) were used to interpret the carbon conversion data. The overall fitting extent of the RPM was slightly better than that of the VRM and SCM, thus the RPM was adopted to derive reaction rate constants. For each coal-biomass ratio in the mixture, the activation energy and pre-exponential factor were determined using the Arrhenius equation.