Gasification of Graphite and Coke in Carbon–Carbon Dioxide–Sodium or Potassium Carbonate Systems

Abstract

The thermodynamics of possible reactions, including gasification and reduction reactions, in carbon–carbon dioxide–sodium or potassium carbonate systems was analyzed first. And then, the gasification reactions of graphite and coke with CO2 in this system were studied kinetically by temperature programmed thermogravimetry. The results showed that the carbon conversion curve shifted to a lower temperature zone after Na2CO3 or K2CO3 was added, and graphite was more susceptible than coke to be catalyzed by Na2CO3 or K2CO3. Ten kinetic equations were adopted to simulate the reaction process using the method of Coats–Redfern. The Avrami–Erofeev equation was found to be the most probable kinetic equation, with which the values of activation energy and frequency factor were calculated. The kinetic simulation indicated that the activation energy of coke carbon had been activated to the lowest level by its inner factors, thus it was difficult to be reduced by adding Na2CO3 or K2CO3. The kinetic compensation effect was confirmed to exist in both graphite gasification and coke gasification. X-ray diffraction and Raman spectra were used to characterize the inner difference between graphite and coke, which showed that coke carbon structure was greatly different from graphite structure because of its highly disordered and heterogeneous carbon structure.

Investigation on Gasification Reaction Behavior and Kinetic Analysis of Iron Coke Hot Briquette under Isothermal Conditions

“…It can be seen that the correlation coefficient is greatly different for each model at different temperatures. It is said that the higher the correlation coefficient is, the better the mechanism function is. In this study, the overall fitting extent of the R 2 model is better than those of other models.…”

“…The gasification of ICHB with CO 2 belongs to heterogeneous solid–gas reaction, and during the reaction, the pore structure and surface area of the solid particle are changed . These structural variations and other phenomena such as film mass transfer, pore diffusion, and chemical reaction should be considered.…”

“…The most probable mechanism function can be confirmed by analyzing the linear relationship between g ( x ) and t . The correlation coefficient of linear regression equation, r , is calculated by Equation where, x i and y i are experimental points, and and are the average value of x i and y i , respectively.…”

“…Major reactions relevant to metallurgical coke in BF include gasification, graphitization, combustion, and carburization. Among these reactions, the gasification reaction of coke with CO 2 is required more attention since it has great impact on the degradation of coke and the operational stability of BF . A reduction in coke consumption is considered to be an effective countermeasure to improve energy utilization efficiency and to mitigate CO 2 emission in BF .…”

Preparation of activated biomass carbon from pine sawdust for supercapacitor and CO 2 capture

“…The position, intensities, and widths of the G band and D band were commonly applied to investigate the structure of biochar samples. Because of the D and G peaks have large “overlap”, so if the D and G bands are simply considered, the quantitative relationship between Raman spectra and structural parameters cannot be achieved . Some structural features in disordered biomass carbon samples may cause structural defects.…”