Experiment and regeneration kinetic model study on CO2 adsorbent prepared from fly ash

Abstract

• Loaded potassium-based CO 2 adsorbent was prepared from fly ash. • Temperature programmed desorption of adsorbent was performed. • Experiment and model fitting were combined to study desorption regeneration. • Avrami fractional kinetic model was used to simulate regeneration kinetics. • Diffusion models were used to analysis desorption mechanism. Using power plant fly ash to prepare CO 2 adsorbent can not only realize low-carbon power in power plants, but also effectively use solid waste to achieve the objective of treating the waste with waste. Regeneration characteristic is an important performance of adsorbent. Through the temperature programmed desorption experiment, the influence of different regeneration conditions on performance and regeneration kinetics can be studied, and the optimal calculation of regeneration conditions can be carried out, so as to realize the recycling of adsorbent with economic benefits. The optimal regeneration temperature and heating rate were 150 °C and 10 °C/min, respectively. Under these conditions, the desorption capacity was 1.7454 mmol/g, and the desorption efficiency was 86.38%. Avrami fraction kinetic model was used to simulate and calculate the regeneration kinetics of adsorbent. The results showed that the regeneration temperature affected the regeneration mechanism. High regeneration temperature and high heating rate could promote the desorption kinetic rate to increase. When the regeneration temperature was 90 °C and 190 °C, k a was 0.000885 min −1 and 0.001318 min −1 respectively. Three kinds of diffusion were used to study the regeneration mechanism. It was concluded that after the regeneration temperature was higher than the chemical desorption temperature, the desorption regeneration could be divided into early, middle and final stages, and the rate controlling steps were respectively: intraparticle diffusion control, joint control of surface chemical reaction and intraparticle diffusion, and membrane diffusion control. Physical desorption occured when the regeneration temperature was lower than 110 °C. The desorption time was longer and CO 2 concentration released was always low.