Approach for Minimizing Operating Blast Furnace Carbon Rate Using Carbon-Direct Reduction (C-DRR) Diagram
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he blast furnace process is a major energy consumer in an integrated steel plant, with energy consumption ranging from 10 to 13 GJ/ton crude steel, including the hot stove. Other big consumers of energy are sintering (from 2 to 3 GJ/ton crude steel), coke-making (from 0.75 to 2 GJ/ton crude steel), and steel rolling (from 1.5 to 3 GJ/ton crude steel).[1] The complexities of the heat and mass transfer processes coupled with a large number of gas–solid, solid–solid, and solid–liquid reactions, combustion processes and interphase mass transfer make the modeling of blast furnaces extremely difficult for prediction of CO2 emissions. The models cited in the literature for purposes of CO2 emission prediction are predominantly two-zone models[2,3,4] and data-driven models which require use of plant data.[5] Based on these models, CO2 minimization approaches in integrated steel plants have been developed, which have been focused either on the blast furnace system or on combined blast furnace as well as steel-making units.[2,3] The use of two-zone models for existing supervisory control system in blast furnaces consisting of a charge calculation model for determining the burden and blast rates is well established; however, such models are not
SOUMAVO PAUL, Graduate Student, 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 July 6, 2012. Article published online December 7, 2012. 20—VOLUME 44B, FEBRUARY 2013
directly linked to emission predictions. The objective of the current study is to develop a two-zone model which can be integrated with an existing supervisory control system of a blast furnace for visualization of the emission pattern. Minimization of emissions implies reduction of input carbon rate. For any given input carbon rate, a top gas CO2 equivalent (total of CO and CO2 in the exit gas) can be readily computed after accounting for carbon in hot metal and carbon in outlet dust. As for a given operation the carbon in hot metal and dust losses are relatively constant, the exit gas CO2 equivalent is directly proportional to input carbon rate. Hence minimization of CO2 emissions are a direct consequence of input carbon rate. As an example, an input carbon rate of 500 kg/THM for the present plant operation corresponds to an emission value of 1.667 t CO2/THM. The model in the current study is based on the use of carbon-direct reduction (C-DRR) diagrams for purposes of carbon rate minimization for minimizing CO2 emissions. A review of the literature on the use of C-DRR diagrams to minimize carbon rate in blast furnace brings out that insufficient study has been performed on the specific use of such diagrams in an operating plant for minimizing CO2 emissions attributable to blast furnace. The use of C-DRR diagrams have been referred in earlier publications for prediction of carbon rates.[6,7,8] Ryman[9] has indicated the possible use of C-DRR diagrams d
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