Structural Characterization of Carbon in Blast Furnace Flue Dust and Its Reactivity in Combustion

As an environmentally hazardous waste, blast furnace (BF) flue dust had a potential to reduce CO2 emission if recycled as fuels or reducing agents due to the high carbon content. The structure of carbon was a principal factor to the reactivity of carbon conversion and therefore was highly relevant to efficient utilization. In this work, the characteristics and chemical structures of carbonaceous materials in BF flue dust were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, and Raman analysis. The results showed that the aromatic structure of crystalline carbon was dominant in carbonaceous materials. Polymeric aromatic carbon and oxygen-containing groups (epoxide and esters carbon) existed on the surface. The stacking height (Lc), the in-plane crystallite sizes (La), and the interlayer spacing (d002) of the aromatic structure layer were 2.45, 3.31, and 0.347 nm, respectively. The mass ratios of chars and cokes to carbonaceous matter were estimated to be 90.56% and 9.44%, respectively, by Raman spectroscopy. Then, the combustion reactivity was studied by thermogravimetric analysis using the Kissinger–Akahira–Sunose kinetics method. The activation energy as a function of conversion degree was determined. The results thus provided fundamental information for the utilization of BF flue dust for thermochemical conversion.