Study on the mechanism of the effect of biomass ash on the erosion and adhesion behavior of Al2O3 ceramic particles

Abstract

Biomass coupled with photothermal gasification technology is a new type of technology using heat carriers to transfer the solar energy to supply heat, and directs the solar energy absorbed by the heat carrier to provide a continuous heat source for biomass gasification. To investigate the erosion and adhesion mechanism of cornstalk ash (CSA) on heat carriers (Al2O3 ceramic spheres) during heat transfer, ash fusion temperature analyzer (AFTA) and FactSage thermodynamics software were used to analyze the effect of alumina addition over CSA sintering from the perspective of melting point, high-temperature heating stage coupled with optical microscope system (HTSOM) was used to observe of the adhesion behavior of CSA on the surface of ceramic spheres, X-ray diffractometry (XRD) and Laser-induced breakdown spectroscopy (LIBS) as well as SEM-EDS (Scanning electron microscope - Energy dispersive spectrometer) were used to detect the mineral evolution from both matter and elements. The results showed that the sintering stage (FT-DT) of CSA extended by adding more than 5 wt% of Al2O3 to CSA. Furthermore, it was found that as the temperature increased, Al-containing minerals such as pyroxene and chalcocite were formed, which indicated the CSA began to erode the heat carrier by mineral evolution on the surface of ceramic spheres. At high temperatures (>1200 ℃), CSA completely melted to form a liquid phase that wrapped around the surface of the ceramic spheres, which played a role in insulation layer during the cooling process to reduce the cooling rate of the surface of the ceramic sphere, resulting in more evident slagging problem. At the same time, the K and Ca element in the CSA was captured by ceramic spheres. The mineral transformation between the ceramic spheres and CSA was simulated by FactSage thermodynamic software, and it was found that the addition of Al2O3 resulted in the increase of the ash melting temperature and the formation of Al-containing mineral matters such as nepheline and augite.