To address the problem of variability in in situ Raman spectroscopy for determining the chemical structure of chars, the rationality of Raman’s original peak spectrum fitting method, the influence of objective lens magnification, particle size, and number of measurements on peak shape and characteristic parameters were investigated. The results show that the Raman original peak spectrum of char is fitted by five peaks and the goodness of fit is best when the D3 peak is fitted by a Gaussian curve. The intensity of the peak spectrum and stability of the characteristic parameters of the Raman spectroscopy are related to the objective lens magnification. For a relatively large objective lens magnification, the Raman peak spectrum intensity is increased and the coefficient of variation in the characteristic parameters is accordingly reduced. As particle size increases, the characteristic parameters A_G/A_All that characterize the perfect graphite structure decrease and the characteristic parameters A_D1/A_All, A_D3/A_All, and A_D1/A_G that characterize the defective graphite structure increase. The coefficient of variation for the characteristic parameters is found to be the smallest for the particle size range of 81–96 μm. Micro-Raman imaging reveals that the microscopic characteristic parameters of different micro zones are significantly different and the number of measurements required to achieve reliable Raman characteristic parameters is related to this anisotropy.

Various characterization methods are used to investigate the physical and chemical properties of steel plant flying dust and waste oil sludge, and the combustion characteristics of the mixtures with pulverized coal are studied via thermogravimetric analysis; the catalytic combustion mechanism is also explored. The results show that two types of metallurgical by-products with small particle sizes and developed pores are evenly dispersed in the pulverized coal and are stably combined with it. The additives reduce the ignition temperature and the temperature corresponding to the maximum combustion rate of pulverized coal; simultaneously, they increase the heat released during pulverized coal combustion. During the pyrolysis stage of pulverized coal, the heat generated via organic component combustion in waste oil sludge promotes a cracking reaction and improves the development of the char’s micropore. During the char combustion stage, no catalyst deactivation phenomenon occurs under the ratios of inorganic components in the two types of metallurgical dust and sludge. Two additives markedly reduce the activation energy of the combustion reaction.