Devolatilization Characteristics and Kinetic Analysis of Lump Coal from China COREX3000 Under High Temperature
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INTRODUCTION
THE COREX process is the first commercially operating smelting reduction process, which has been successfully applied in South Africa, South Korea, India, and China.[1,2] The biggest advantage of this process has realized the lump coal instead of coke to extract high quality hot metal, so the dependence on coking coal resources is reduced. The required quantities of lump coals are continuously charged into the gasifier at room temperature, as shown in Figure 1.[3,4] The gasifier is a dome-shaped countercurrent reactor, which can be divided into five zones from top to bottom: freebroad, fluidized bed, moving bed, raceway, and hearth.[4] The fast pyrolysis of lump coal is occurred at the freebroad under around 1373 K (1100 C), which ensure the complete cracking of volatile matters released from coal. After the gasification reaction and RUNSHENG XU, YANXIANG LIU, and KEJIANG LI, Ph.D. Candidates, JIANLIANG ZHANG, Professor, and GUANGWEI WANG, ZHENGJIAN LIU, and KEXIN JIAO, Lecturers, are with the School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mail: [email protected] HAIBIN ZUO, Associate Professor, is with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing. Manuscript submitted October 14, 2015. Article published online May 31, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
mechanical extrusion at fluidized bed and moving bed, majority of the lump coal falls into the raceway to complete combustion reaction. A small number of lump coal stay in the hearth to form dead stock column and participate in the slag/iron–carbon reaction. The industry practice indicated that the properties of lump coal had a strong impact on the COREX performance.[5–8] The output of gas was determined by the pyrolysis properties of lump coal, and the permeability of burden was determined by the properties of lump char. Thus, it is important to understand the behaviors of lump coal at high temperature for improving the production efficiency of COREX process. Degradation behavior of lump coal in COREX gasifier has been extensively investigated in the past. Kim[9] investigated devolatilization and cracking characteristics of five Australian coals. The study demonstrated that the cracking and swelling behaviors of coal were influenced by physical as well as chemical properties. Minkina[10] investigated devolatilization and the resulting char structure of six bituminous coals, from 20 to 40 mm in size, at 573 K to 1073 K (300 C to 800 C). The results noted that lump chars obtained from caking coal exhibited better resistance to breakage than their parent coals, while noncaking coals showed the opposite behavior. Sahoo[11,12] investigated degradation characteristics of weathered South Blackwater coal. It was found that the generation rate of coal fines increased with the increasing weathering period. Campbell[13] VOLUME 47B, AUGUST 2016—2535
this study will be useful in understanding of devolatilization proc
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