Coats-Redfern integral method for K2CO3 regeneration

“Early in 2009, Zhao et al. investigated the decomposition kinetic behaviors of KHCO3 in TGA reactor. Provided that chemical reaction was the rate-limiting step, thermal decomposition process of KHCO3 could be described by simplified kinetic equations. The Coats-Redfern integral method was employed to correlate the solid decomposition conversion data (Eq. 22).”


“where, g(α) is the integral form of reaction mechanism function. The general form of mechanism functions of solid-state reactions can be found in Table 3. Herein, g(α)=−ln(1−α), assuming that the decomposition of KHCO3 follows the first-order kinetic mechanism. T is reaction temperature, α is solid decomposition conversion, β is heating rate, R is the ideal gas constantA and E are the pre-exponential factor and apparent activation energy.”


“The Coats-Redfern integral method was applied to correlate the solid decomposition conversion data to analyze the regeneration kinetics of the potassium-based sediment adsorbents. The regeneration kinetic behaviors were dependent on final temperature, KHCO3 loading and heating rate. The activation energy was in the range of 92.59-109.91 kJ/mol, and the optimum regeneration conditions were determined as the final temperature of 200°C, KHCO3 loading of 40 wt.% and heating rate of 10°C/min (Wang et al., 2013). A universal integral relation between the regeneration conversion and reaction temperature had been constructed to depict the regeneration kinetic behaviors of K2CO3/Al2O3 (Eq. 23). As had been noted, the formation of KAl(CO3)2(OH)2 in carbonation had made the full regeneration of K2CO3/Al2O3 rather difficult. The complicated regeneration process involved three steps as the decomposition of outer KHCO3(O), inner KHCO3(I) and KAl(CO3)2(OH)2 in sequence. The Avrami-Erofeev formula was then employed as the mechanism function to describe their decomposition kinetic behaviors. The activation energies for the three stages were 69.7, 73.8 and 84.5 kJ/mol, respectively. The formed KAl(CO3)2(OH)2 byproduct had increased the energy demand for full regeneration of the K2CO3/Al2O3 adsorbent (Zhang and Chen, 2020).”



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