Numerical Simulation of Fluid Dynamics and Thermal Flow in the Blast Furnace Hearth

• Main Authors: Chi-En Huang, 黃啟恩
• Other Authors: W.-T. Cheng
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/45228326070926086549

博士 === 國立中興大學 === 化學工程學系所 === 96 === In order to reduce the cost for iron making, prolonging the campaign life of a blast furnace has been pursued all the time. It is well known that the preventing the erosion of the hearth is crucial. The behavior of hot metal flow in the hearth has been considered as one of the key factors for determining hearth erosion in a blast furnace. To provide a useful insight into the hearth of a blast furnace, in this thesis a numerical model has been developed to analyze the flow and heat transfer under various porosity distribution within the deadman as well as cooling efficiency. Based on BF 5 of BHP, Australian, and BF 2 of Chinese Steel Co., Taiwan, respectively, three-dimensional turbulent Navier-Stokes equations with conjugate heat transfer and Ergun equation was solved by computational fluid dynamics (CFD) for hot metal flow through the dead man with porous coke below the tuyere level in a blast furnace hearth during tapping process. The computational domain includes the refractories, hearth, deadman, and hot metal liquid in the blast furnace. According to the theoretical model and numerical method mentioned above, this dissertation investigated three topics of the sensitivity of turbulence and natural convection in the hearth, the effect of the non-uniform porosity distribution on the hot liquid metal flow and heat transfer, and the efficiency of the different cooling stave as well as the influence on heat flux of the hearth wall under different temperature of cooling water for BF 2 of CSC. As shown in the results, the key conclusions of this study are found as follows: (1) Comparing laminar flow and turbulent flow models, the temperature deviation is about 3% in the hearth, but as the natural convection is applied in the mathematical model, the heat flux through the hearth bottom were decreased by 28%, 27% and 24%, for laminar flow, stand k-ε turbulent flow, and RNG k-ε turbulent flow, respectively, so it is suggested that the effect of natural convection is more sensitive than fluid flow behavior to simulate momentum and heat transfer in the blast furnace hearth. (2) While the increment of the refractory temperature has been detected, it implies the hot metal flow getting stronger increasing the erosion of the hearth potentially. (3) If the dead zone area was enlarged, the peripheral flow will be intensified in the hearth corner, and the heat flux at the central of hearth bottom will decease, which is a remarkable threat of hearth erosion. (4) The circulatory flow of hot liquid metal is enhanced as the dead man becomes sitting with gutter coke-free space, increasing the temperature at the hearth corner, which suggests the existence of gutter coke-free space may cause elephant foot type erosion. (5) In drainage of hot liquid metal, the heat flux of taphole significantly increase, therefore, it is needed to individually monitor the temperature of cooling water flowing through the copper staves, as well as to install thermocouples around the tapholes. (6)The heat flux of the hearth is insensitive to the temperature of cooling water before the refractories are eroded, which implies that the performance of the water chiller may be limited in the beginning of the blast furnace campaign.