Simulation of Frozen Slag Inside Brickless Reaction Shaft of Flash Smelting Furnace
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SINCE its appearance in 1949, Outokumpu flash smelting technology has been widely accepted as a competitive smelting technology.[1–5] Flash smelting technology has been adopted to establish or reconstruct most copper or nickel smelters throughout the world.[6] The reaction shaft is the most important part of a flash smelting furnace. In the copper flash smelting process, the reaction shaft must endure harsh conditions, such as (1) high temperatures varying from 1573 K to 1773 K (1300 °C to 1500 °C); (2) strong oxidizing atmospheres containing 50 pct to 80 pct O2 and 40 pct to 70 pct SO2; and (3) solid particles and melts with speeds of over 100 m/s. With the use of Four High Technology (high feed, high matte grade, high oxygen enrichment, high heat capacity), the reaction shaft is more likely to corrode[7,8]; thus, protecting the shaft is crucial. Refractory bricks and water jackets are often used to protect the shaft wall in a traditional reaction shaft. JINLIANG WANG, Associate Professor, HOUQING WANG, Postgraduate, and CHANGREN TONG, Professor, are with the School of Metallurgical and Chemical Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, P.R. China. Contact e-mail: [email protected] WENHAI ZHANG, Academician, is with the China Nerin Engineering Co. Ltd., Nanchang 330002, P.R. China. CHUANFU ZHANG, Professor, is with the School of Metallurgy and Environment, Central South University, Changsha 410083, P.R. China. Manuscript submitted December 3, 2012. Article published online September 10, 2013. 1572—VOLUME 44B, DECEMBER 2013
However, the refractory bricks will corrode until a layer of frozen slag forms on the brick surfaces.[9–12] A brickless reaction shaft is a new type of shaft used in a flash smelting furnace. Unlike a traditional reaction shaft, there are no refractory bricks; steel nails are welded to the steel shell to prevent frozen slag from falling down. In addition, there are no water jackets buried in the shaft wall; cooling water is sprayed around the outer side of the steel shell. The inner structure of a new brickless reaction shaft is shown in Figure 1. A brickless reaction shaft has been in operation for many years in a smelter at the Broken Hill Proprietary Company (BHP). Prolonged use has created a layer of frozen slag in the brickless reaction shaft, which is efficient for prolonging furnace life and promoting production safety. The inner condition of a brickless reaction shaft after operation is shown in Figure 2. Significant research has been carried out on frozen slag. Chen[13] analyzed in-shaft frozen slag with a scanning electron microscope (SEM) and created a two-dimensional model of the moving boundary of a traditional reaction shaft;[14] a three-dimensional model was pursued by our research team.[15] Wang et al.[16] performed an experimental study of the melting point, the surface tension[17] and the viscosity[18] of frozen slag in a flash smelting reaction shaft. Guevara and Irons[19] experimentally studied the formation, heat transfer, and the similar Grasho
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