Synergy mechanism of biochar and petcoke co-combustion based on potassium migration and transformation

Abstract

Co-combustion of biochar and pet-coke can reduce environmental pollution, provide fuel energy supply and improve fuel reaction characteristics. In this study, the co-combustion characteristics and synergistic behavior of rice straw char (BC) and petcoke (PC) were analyzed based on thermogravimetric analysis and kinetic analysis. The combustion corroborative experiments were conducted based on a fixed bed reactor, and the contents of different forms of potassium (K) during combustion of semi-char were characterized. Raman spectroscopy and X-ray photoelectron spectroscopy were used to characterize the carbon structure order and surface elements distribution characteristics of the semi-char after the combustion. The results showed that the co-combustion reactivity improved with the temperature and the BC blended ratio increase. Moreover, the synergistic effect increased with the temperature decrease and the BC blended ratio increase. The synergistic effect was confirmed to be related to the K migration and transformation, and its behavior was varied with active K content adsorbed by PC. The H2O-soluble K would be transformed into -COOK during PC combustion. -COOK would reduce the order of PC and increase the content of amorphous carbon during combustion.