**3. Results and Discussion**

#### *3.1. FTIR Analysis*

In order to compare and analyze the combustion characteristics of anthracite and coke powder used in sintering site, this experiment adopts Fourier transform infrared spectroscopy to detect the functional group structure of the two fuels and compare the differences between the structures, thus providing a theoretical basis for studying their combustion characteristics and laws. In infrared spectrum detection, the absorption peak of each functional group has a specific spectral position. The corresponding functional group can be found according to the peak of the characteristic peak on the spectrum. According to relevant studies [26,27], the infrared spectral curves of coal samples can be divided into hydroxyl (3700~3000 cm<sup>−</sup>1), aliphatic hydrocarbon (3000~2800 cm−1), oxygen-containing functional group (1800~1000 cm<sup>−</sup>1) and aromatic hydrocarbon (900~700 cm−1) according to the spectral wave number, the structure and properties of functional groups. Therefore, in this paper, the infrared spectral curves of anthracite and coke powder were divided into nine points A~I in order to better distinguish the differences in the structure of their functional groups. It can be seen from the Figure 3 that there is a big gap between the two spectral curves.

**Figure 3.** Fourier infrared spectra of anthracite and coke.

It can be seen from Table 3 that there are significant differences between coke powder and anthracite at B and H, which represent the –CH group on aromatic ring and aliphatic hydrocarbon in coal respectively. As the content of –CH will increase with the increase of volatile substances, compared with coke powder, anthracite still contains a small amount of volatile substances, so the content of –CH group in anthracite is significantly higher than that of coke powder. At the same time, the comparison of the absorbance of the two at point A in the infrared spectrum shows that the content of hydroxyl in the pyrolysis process of coking coal is greatly reduced, that is, the number of active groups and the activity of coal are reduced, so the reactivity of coke powder is significantly lower than that of anthracite. This is also the reason why the mixed combustion process of anthracite and coke powder for sintering will present a multi-stage weightless reaction.


**Table 3.** Infrared spectrum absorption peak classification of anthracite and coke powder.
