Effect of demineralization on pyrolysis semi-coke physical and chemical characteristics and oxy-fuel combustion characteristics

With global green and low-carbon development, carbon emission reduction is imminent. Oxy-fuel combustion technology is considered to be one of the most promising carbon capture and carbon sequestration technologies. In this work, the physical and chemical characteristics and oxy-fuel combustion characteristics of semi-coke (SC) and demineralized semi-coke (De-SC) were studied. The result shows that, compared with 20% O2/80% CO2, under 30% O2/70% CO2 atmosphere, the ignition temperature and burnout temperature of De-SC are lower, the maximum combustion rate is higher, and the main combustion process can be clearly divided into homogeneous and heterogeneous combustion stages. Compared with SC, De-SC has a less developed pore structure and lower alkali metal and volatile content, which lead to higher ignition temperatures for De-SC. The demineralization process makes the microcrystalline structure of carbon looser and increases the relative content of oxygen -containing functional groups, which are all beneficial to increasing the reactivity of De-SC. The combustion method of De-SC is mainly the particle surface reaction. Only in the atmosphere of 30% O2/70% CO2 and the heating rate of 30 degrees C/min the combustion mode of De-SC is on the surface and inside the particles. Under different atmospheres, compared with SC, De-SC has lower activation energy and higher pre-exponential factor. The activation and pre-exponential of De-SC have a kinetic compensation effect. The results of this paper provide a theoretical basis for an in-depth understanding of the application of De-SC under oxy-fuel conditions.

Automated summary

This study investigated the physical, chemical, and combustion characteristics of semi-coke (SC) and demineralized semi-coke (De-SC) under oxy-fuel conditions. The results showed that compared to SC, De-SC exhibited lower ignition and burnout temperatures, higher combustion rates, and distinct homogeneous and heterogeneous combustion stages. Demineralization resulted in a less developed pore structure, lower alkali metal and volatile content, and increased reactivity of De-SC. The combustion of De-SC primarily occurred on the particle surface, with a combination of surface and internal combustion at specific conditions. De-SC had lower activation energy and higher pre-exponential factor compared to SC under different atmospheres. These findings provide a theoretical basis for the application of De-SC in oxy-fuel combustion.