A kinetic study on lignite char gasification with CO2 and H2O in a fluidized bed reactor

Abstract

Lignite char gasification experiments in CO2, H2O and their mixture were performed in a fluidized bed reactor over the temperature range of 1060K to 1210K. The active sites occupied by different gasifying agents in CO2/H2O mixture were separated and the kinetics was analyzed. Results show that the reactivity of gasification increases rapidly as the temperature rises. The average reaction rate in 50%CO2/50%H2O mixture is slower than the sum of the reaction rates separately, which indicates that CO2 and H2O compete for the same reaction active sites on the char surface. Furthermore, with an increase of temperature, the competition capacity of CO2 gasification over H2O gradually increases, as a result, CO2 gasification occupies more active sites than H2O when the temperature is higher than 1160K. Calculations of the activation energy in the kinetically controlled region based on the shrinking core model reveal that the activation energies follows the trend: N2/CO2>N2/H2O>CO2/H2O.

Gasification of biofuels blended from olive mill solid wastes and pine sawdust under different carbon dioxide/nitrogen atmospheres

“…The figure shows that the CO 2 gasification exhibits a notable increase of the required time for X = 0.9 by nearly two times. This behavior are consistent with the results reported by [35,39,47] who proved that at the same temperature, the gasification is enhanced by replacing CO 2 with H 2 O.…”

“…The results show an increase in the char conversion and, consequently, a decrease of the characteristic time of gasification. This conclusion is consistent with some results reported in the literature [39][40][41]. Indeed, Tong et al [39] realized lignite char gasification tests using CO 2 , H 2 O and their mixture in a fluidized bed reactor.…”

“…This conclusion is consistent with some results reported in the literature [39][40][41]. Indeed, Tong et al [39] realized lignite char gasification tests using CO 2 , H 2 O and their mixture in a fluidized bed reactor. They observed that the reactivity of gasification enhances rapidly when the temperature increases from 1333°C to 1483°C.…”

“…This gap is may be due to the difference in the intrinsic reactivity of C-H 2 O and C-CO 2 reactions [35]. Thus, Tong et al [39] have proved that at the same temperature, and with three different atmospheres, the gasification rate was higher with: 50%N 2…”

Experimental study of a single char particle combustion characteristics in a fluidized bed under O2/H2O condition

“…The char was prepared in a mini-bubbling fluidized bed combustor, because the reactor can be heated and cooled at a faster rate and is easy to operate. The detailed description of the reactor can be found elsewhere [28,29]. The bed material was quartz sand (size: 0.3-0.35 mm), and the fluidization number was set to 3.…”