Mechanism of the effect of chicken manure on slagging during the combustion of wheat straw

Abstract

Under the carbon neutral and carbon peak background, biomass can be used as an alternative clean energy source for coal resources, its efficient utilization has become a hot issue in current research. Biomass usually has a high content of alkali metals and alkaline earth metals, which can easily cause slagging and slag blocking during the combustion process. Therefore, in this study, the ash fusion temperature (AFT) and its slagging mechanism during biomass combustion were investigated, using experimental characterization methods such as X-ray diffraction (XRD), confocal Raman spectroscopy (Raman), scanning electron microscopy (SEM), and thermodynamic software FactSage, the migration and transformation behavior of minerals during the melting process of XM ash with the addition of chicken manure in an oxidizing atmosphere was modeled. The results showed that when more than 15% JF was added, the deformation temperature (DT) was more than 1 000 ℃, which met the requirements of fluidized bed operation. With the increase of JF content, the formation of high melting point (MP) feldspar-like minerals such as akermanite (Ca2MgSi2O7) and merwinite (Ca3MgSi2O8) was the main reason for the increase of four characteristic temperatures of XM. From the perspective of silicate, the addition of JF increases the bridging oxygen bonds and the degree of polymerization of silicate in the ash sample, increasing the AFT of the mixed ash sample. According to the slag composition and ash melting characteristics, and by observing the microscopic morphology of the ash surface with the aid of SEM, with the increase of JF content, the ash surface changed from compact and smooth to porous and rough at 950 ℃, greatly alleviating the problems of biomass slagging and sintering. Using the thermodynamic software FactSage to calculate the mineral composition and liquid content at different temperatures, it was found that adding JF increased the total liquid phase content. The phenomenon of low temperature co-melting occured in high MP minerals resulting in a smaller increase in FT than DT. To summarize, the experimental and thermodynamic calculations were conducted to study the AFT changes and slagging mechanisms during biomass combustion, to provide data support for the large-scale application of biomass energy.

Keywords

• biomass
• chicken manure
• combustion
• ash melting characteristics
• slagging mechanism