An Approach for Simulation of Corex Process Smelter Gasifier for Prediction of Coal Rate and Silicon in Hot Metal
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scarcity of quality coking coal for blast furnace (BF) and environmental pressures led to the development of alternative iron making processes that require little or no coke. The Corex process has emerged as one of the most acceptable alternatives of BF iron making. The stable and highly successful operation of various Corex units across the world (POSCO in South Korea; JSW and Essar Steel in India; and Saldanha Steel in South Africa) has confirmed that the Corex process is a commercially proven technology. Lee et al.[1] developed a computational model to simulate the transport phenomenon in a Corex smelter gasifier. They focused mainly on coal pyrolysis by dividing it into various zones: free board zone, drying and devolatization zone, gasification zone, and combustion zone. The model calculated the temperature and the compositions of exit gas, which was in close agreement with the operational data. Later, the model was used to study the effect of operational parameters like the steam injection, bed height, etc. on the process performances. However, the model does not consider the reduction of directly reduced iron (DRI) and subsequent smelting of reduced charge to hot metal and slag. Pal et al.[2] developed a steady-state mathematical model of a smelter gasifier by dividing it into three zones: free board zone, fluidized bed zone, and moving
BRIJENDRA SRIVASTAVA, Graduate Student, and S.K. ROY and P.K. SEN, Professors, are with the Department of Metallurgical and Materials Engineering, Indian Institute of Technology, Kharagpur 721302, India. Contact e-mail: [email protected] Manuscript submitted May 30, 2010. Article published online July 17, 2010. METALLURGICAL AND MATERIALS TRANSACTIONS B
bed zone. It is based on the multiphase conservation of mass, momentum, and heat. The temperatures of hot metal and top gas and the composition of the top gas calculated through model showed a good agreement with the reported plant data. This model differed from the model proposed by Lee et al.[1] mainly with respect to the combustion zone. Pal et al.[2] assumed a twodimensional (2D) model for the combustion zone, whereas a zero-dimensional model for the combustion zone was assumed by the Lee et al.[1] Also, Pal et al.[2] have assumed the kinetically controlled reduction of hematite and wustite in the smelter gasifier. However, the model does not attempt to predict the compositions of hot metal and slag produced. No model of the smelter gasifier in the Corex process has been proposed until now, which focuses on both the coal pyrolysis as well as the wustite reduction in the smelter gasifier and calculates the compositions of hot metal and slag produced. In the current article, a thermodynamic model for the smelter gasifier in the Corex process has been proposed focusing principally on the reduction of wustite leading to the prediction of slag, metal, and smelter exit gas composition. It was necessary to consider a simplified model of coal pyrolysis to arrive at smelter exit gas composition. The smelter gasifier of the Corex proc
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