Prediction of pyrolysis kinetic parameters from biomass constituents based on simplex-lattice mixture design

The aim of this study is to determine the effect of the main chemical components of biomass: cellulose, hemicellulose and lignin, on chemical kinetics of biomass pyrolysis. The experiments were designed based on a simplexlattice mixture design. The pyrolysis was observed by using a thermogravimetric analyzer. The curves obtained from the employed analytical method fit the experimental data(R2N 0.9). This indicated that this method has the potential to determine the kinetic parameters such as the activation energy(Ea), frequency factor(A) and reaction order(n) for each point of the experimental design. The results obtained from the simplex-lattice mixture design indicated that cellulose had a significant effect on Eaand A, and the interaction between cellulose and lignin had an important effect on the reaction order, n. The proposed models were then proved to be useful for predicting pyrolysis behavior in real biomass and so could be used as a simple approximation for predicting the overall trend of chemical reaction kinetics.

Carbon dioxide desorption behavior of potassium carbonate supported on gamma-alumina solid sorbent in wet fluidized bed under steam atmosphere

Since the carbon dioxide(CO_(2))capture using solid sorbent is a reversible reaction,the solid sorbent can be regenerated by the desorption process.Therefore,the desorption process is one of the key important processes for the CO_(2)capture system.Traditionally,most of the literature studies focus on the desorption of solid sorbent under an N_(2)atmosphere.However,the desorption process of the solid sorbent is inappropriate in the real system because the system will need another process to separate CO_(2)and nitrogen(N_(2))after the desorption process.This study focused on the CO_(2)desorption of potassium carbonate supported on gamma-alumina(K2CO3/γ-Al_(2)O_(3))in a wet fluidized bed under a steam atmosphere by using the multiphase computational fluid dynamics(CFD)simulation.The effects of water thickness and dry restitution coefficient on CO_(2)desorption rate were investigated to provide a realistic particle collision behavior and to explore their effects on CO_(2)desorption phenomena.Moreover,the effect of steam velocity on the hydrodynamic behaviors of fluidization which on CO_(2)desorption rate was studied.The simulated results demonstrated that all the parameters,water thickness,dry restitution coefficient,and steam velocity had significantly affected system hydrodynamics and CO_(2)desorption rate in the wet fluidization desorption process.Furthermore,the effect of desorption temperature on CO_(2)desorption rate was evaluated for finding the appropriate temperature for CO_(2)desorption process of K2CO3/γ-Al_(2)O_(3).The results showed that the appropriate desorption temperature for CO_(2)desorption under steam atmosphere was the temperature over 150℃.

Effect of a pulsating flow on hydrodynamics and fluid catalytic cracking chemical reaction in a circulating fluidized bed riser

The three-dimensional computational fuid dynamics(3D-CFD)of a pulsating flow applied to the fluid catalytic cracking(FCC)reaction was investigated in the riser of a circulating fluidized bed reactor.The kinetic parameters of the FCC and coke burning reactions for predicting the reactant conversion and product yield percentages were applied.To increase the reactant conversion level and product yield.the effect of the pulsating flow operating parameters was considered using a 2k statistical experimental design with four factors(amplitude,frequency,types of the waveform,and amplitude ratio).The 3DCFD simulation was successfully validated from the experimental literature data.The frequency and type of the waveform were found to be the significant operating parameters.The expression of the fitted regression model and response surface contour were derived and revealed that the pulsating flow provides a higher reactant conversion level and product yield percentages compared to a non-pulsating or steady flow.