A Mechanism Model for Raceway Formation and Variation in a Blast Furnace
- PDF / 631,260 Bytes
- 8 Pages / 593.972 x 792 pts Page_size
- 80 Downloads / 167 Views
a blast furnace (BF), high-temperature blast is introduced laterally at a high velocity through a tuyere into the packed bed. This forms a cavity in front of the tuyere called a raceway. The size and shape of a raceway have a great influence on the aerodynamics in the furnace and, thus, have great significance for stable BF operation. For this reason, the raceway has been one of the main fields of focus for BF study. Previous research[1,2] found that two different raceway sizes could be obtained at the same gas velocity in cold model experiments mainly depending on increasing or decreasing blast velocity and called the phenomena ‘‘raceway hysteresis.’’ Sarkar et al.[2] studied raceway hysteresis in detail and proposed a force balance equation on the basis of their experimental results as follows:
JING GUO and ZHAOJIE TENG, Ph.D. Students, SHUSEN CHENG, Professor, and HONGBO ZHAO, Lecturer, are with the State Key Laboratory of Advanced Metallurgy & School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing (USTB), Beijing 100083, P.R. China. Contact e-mail: [email protected] HONGWEI PAN, Engineer, is with Shougang Research Institute of Technology, Beijing 100041, P.R. China. PENGYU DU, Engineer, is with CERI Engineering Technology Co., Ltd., Beijing 100176, P.R. China. Manuscript submitted September 13, 2012. Article published online March 26, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
Fp Fw Ff ¼ 0
½1
where Fp , Fw , and Ff represent the blast pressure force, bed weight force, and frictional force exerting on the packed bed over the raceway roof, respectively; the positive sign before Ff is used when gas velocity decreases, and the negative sign is employed when the velocity increases. Gupta et al.[3] deduced all the forces of Eq. [1] and established a one-dimensional mathematical model to predict raceway penetration. They tried to explore raceway formation mechanisms in the manner of mechanical analysis based on their cold-model experiments. However, the conditions of cold model experiments are quite different from that of an actual blast furnace because temperature, pressure, and chemical reactions, especially combustion reactions, should be taken into account. To study raceway mechanisms under high-temperature conditions is much more complex; thus, there are only some empirical formulas[4–6] currently available. Guo et al.[7] corrected the miscalculation of frictional force in the radial region existing in Gupta’s model[3]; revised the factor contributing to the total area of a raceway, i.e., n; and obtained a modified mathematical model that could be applied to predict the raceway penetration for a BF directly. Based on the modified model, Guo et al.[8] proposed a dynamic model to illustrate how raceway penetration varies over time when gas velocity has changed according to Newton’s second law. In this article, the mechanical model is further improved and the effects of combustion reactions are taken into account to reveal the mechanisms for raceway formation and variat
Data Loading...
