효율적인 고로 조업을 위한 석탄과 코크스의 연구

Abstract

The properties of carbonaceous materials were investigated for effective blast furnace operation. First of all, the change in aromatic CH (3030 - 2950cm-1) and aliphatic CH (2920 - 2850cm-1) of raw and heated coals in the thermoplastic region was investigated by Fourier transform infrared spectroscopy (FT-IR). It was confirmed that the aliphatic CH abundant in coals of high volatiles is closely related to the maximum fluidity of raw coals. The peak area ratio of aromatic CH to aliphatic CH (A_aroCH?A_aliCH ) has close relationship with mean reflectance and aromaticity of raw coals. Aliphatic CH and aromatic CH decreased while A_aroCH?A_aliCH increased with increasing temperature in the thermoplastic range. However, the decomposition trend of each coal clearly showed different features. The coal of low fluidity consumed aliphatic hydrogen to release volatile even before entering thermoplastic region while the coal of high fluidity gradually consumed aliphatic hydrogen all through the thermoplastic region even though they have similar volatiles. The difference in decomposition trend of hydrocarbon resulted in different condensation pattern. In addition, according to the application of 2D correlation spectroscopy for analyzing the spectral change of each coal in thermoplastic region, the relations between R3CH and RCH3 (2910 cm-1, 2958 cm-1) and between R2CH2 and RCH3 (2923 cm-1, 2958 cm-1) were different. It was suggested that the coal properties was correlated with the different decomposition trend and fluidity. The gasification of metallurgical cokes with CO2 and H2O on their porosity and macrostrength were studied. Cokes was reacted with CO2 or H2O in the temperature range of 1100 to 1500oC. During the reaction, the compositional change of product gases were measured by Quadruple Mass Spectrometry (QMS) for evaluating the gasification rate. Image analysis was carried out to measure the porosity according to the distance from coke surface. The porosity at the surface of coke gasified with CO2 indicated low values due to its low reactivity, which resulted in the intraparticle reaction to diffuse into the pores at low temperatures while the coke gasified with H2O showed the tendency to react the coke at the surface. This difference in the reaction behavior can be explained by Thiele modulus. Furthermore, fine powder formation and tensile strength were measured to evaluate macro strength of cokes. According to the results, the different reaction mode caused obvious difference in the tendency of macro strength of the cokes of the same reaction degree. Tensile strength of cokes was strongly affected by their porosity distribution. The effect of graphitization of cokes on the pore structure and gasification with H2O at 1500 oC were studied. All cokes showed the development of pores with annealing to 1500oC caused by mineral reaction, but the porosity of some cokes was decreased with graphitization as the annealing time was longer. Mean area of pores was decreased and pore density was increased with increase of annealing time while annealing gave marginal effect to the pore shape. In addition, gasification rate with H2O at 1500oC is more closely related with the porosity than graphitization degree.