Discussion on chemical energy utilisation of reducing gas in reduction shaft furnace. (1st September 2014)

• Record Type: Journal Article
• Authors: Liu, B. N.; Li, Q.; Zou, Z. S.; Yu, A. B.
• Is Part Of: Ironmaking & steelmaking. Volume 41:Number 8(2014)
• Page Start: 568
• Page End: 574
• Publication Date: 2014-09-01
• Subjects: Reduction shaft furnace -- Reducing gas -- Chemical energy -- Oxygen injection; Iron industry and trade -- Periodicals; Steel industry and trade -- Periodicals; 669.1
• DOI: 10.1179/1743281213Y.0000000168
• Languages: English
• ISSNs: 0301-9233

Abstract

Abstract: The reduction shaft furnace is a countercurrent moving bed cylindrical reactor in which hematite pellets are reduced by a gas mixture of H2 and CO. Most of the reduction shaft furnaces use hydrogen rich gas as reducing gas. The materials and heat balances show that the heat balance determines the gas consumption. Compared with the gas requirement by reduction reaction, a much greater quantity of gas has to be blown into the furnace to satisfy the heat balance, leading to a high energy consumption and high excess of reduction potential of top gas. To solve this problem, a new approach is proposed where some oxygen is blown into the upper zone of the shaft furnace. As the feasibility study of such an approach, a static model was developed first to calculate input gas flowrate and oxygen rate. Then, based on conservations of mass and heat, a kinetic model for a typical MIDREX shaft furnace was developed to investigate the proper position for oxygen blowing. The model predictions were validated by comparison with production data. Finally, a kinetic model was developed to investigate the process of shaft furnace with oxygen blowing. The results show that the gas consumption can be reduced from 1897 to 1405 N m 3 tDRI −1 with oxygen blowing of 20·3 N m 3 tDRI −1 . After oxygen blowing, the temperature increases sharply, the concentration of CO and H2 decreases, and reduction potential of top gas decreases from 1·48 to 0·69, showing that the gas utilisation is greatly improved. These models can be used for process optimisation development.