Gasification Characteristics and Kinetics of Coke with Chlorine Addition
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essential fuel in the blast furnace (BF) smelting process, the coke plays very important roles in providing sufficient heat, reducing agent, carburization of hot metal and columnar skeleton, especially the skeleton role which is irreplaceable by other fuels. In recent years, with the injection of low-quality coals and waste plastics,[1,2] and the employment of imported ores after seawater beneficiation, sinter sprayed with CaCl2,[3] and coke coked by coals and waste plastics, the chlorine introduced into BF is gradually increasing. The metallurgical properties of coke may be affected by the increase of chlorine, and the certain extent of circulation and accumulation of chlorine in BF may make the effect more obvious.[4,5] Hu et al.[6] studied the influence of HCl on the coke, and it was found that with the increase of HCl content in BF gas, the coke reactivity index
CUI WANG, JIANLIANG ZHANG, KEXIN JIAO, ZHENGJIAN LIU, and KUOCHIH CHOU are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, No. 30 Xueyuan Rd, Haidian District, Beijing 100083, P.R. China, and also with State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, No. 30 Xueyuan Rd, Hadian District. Contact e-mail: zhang.jianliang@ hotmail.com Manuscript submitted March 26, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
(CRI) decreases and the coke strength after reaction (CSR) increases, which indicates that the hot strength of coke is improved. While the chlorine is charged into BF with the raw materials and fuels mainly as chlorides (such as NaCl, KCl, and CaCl2.),[7] the initial chlorine forms may bring different effects on coke, and thus the reagent-grade chemical CaCl2 was added into the coke to elucidate the influence of chlorine on the coke gasification, and to further analyze the resulting effects on the BF smooth running and production efficiency in this study. There have been a few studies that explain the catalytic effect of metal chlorides on the pyrolysis of coal or carbonaceous materials. Zou et al.[8] investigated the catalytic effects of five metal chlorides, including CaCl2, KCl, NiCl2, CoCl2, and ZnCl2, on the pyrolysis of lignite by thermogravimetry Fourier transform infrared (TG-FTIR) analysis. The results showed that CaCl2 and ZnCl2 inhibited the conversion of organic matters into light species during pyrolysis of lignite samples, while KCl, NiCl2, and CoCl2 promoted the conversion. Wang et al.[9] investigated the effect of KCl, CaCl2, and FeCl3 as additives on pyrolysis performance of alkali lignin using thermogravimetric analyzer/Fourier transform infrared spectrometer (TG-FTIR) and pyrolysis–gas chromatography/mass spectrometry (PGC/MS). The results indicated that the KCl played a positive role in gasification, the FeCl3 and CaCl2 had a
promoting influence on the thermal cracking of alkali lignin, and the capability of catalytic thermal cracking of alkali lignin by three metal additives was ranked as such: Fe3+ > Ca2+ > K+.
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