Numerical simulation of ironmaking blast furnace shaft
Abstract
The blast furnace (BF) that converts iron ore into molten iron is an important component in iron-steel making. An improvement of the blast furnace fuel efficiency contributes to the reduction of energy consumption in the steel industry because this process represents about 70% of the total energy input to this industry. The goal of the research is to improve the competitive edge of steel mills by developing the advanced Computational Fluid Dynamics (CFD) model to optimize the gas and burden distributions inside a blast furnace for achieving the best gas utilization. A state-of-the-art 3-D CFD model has been developed for simulating the gas distribution inside a blast furnace at given burden conditions, burden distribution and blast parameters. The comprehensive 3-D CFD model has been validated by plant measurement data from an actual blast furnace. Validations of the sub-models are also achieved. The burden distribution is direct related to efficiency and stable blast furnace operation. In this research, a mathematical model for estimating the burden distribution was developed with the combination of the falling curve sub-model, stock-line profile formation sub-model and burden descending sub-model. In a blast furnace, the burden descending velocity may be non-uniform along the radial direction due to the shaft angle and non-uniform consumption. The modifications on two existing burden descending models, i.e., geometric profile (GP) model and potential flow (PF) model are proposed to consider the non-uniform descending speed. The proposed non-uniform descending models are validated with published scaled blast furnace model results. Comparing to the original uniform descending model, the accuracy increases notably for the modified models with the non-uniform descending velocity. The blast furnace burden consists of alternative layers of iron ore and coke. A novel methodology is proposed to efficiently model the effects of alternative burden layer structure on gas flow, heat transfer, mass transfer and chemical reactions. Different reactions and heat transfer characteristics are applied for difference types of layer. In addition, the layered CFD model accurately predicts the Cohesive Zone (CZ) shape where the melting of solid burden taking place. The shape and location of the CZ are determined by an iterative method based on the ore temperature distribution. A new methodology has been developed to determine the location and shape of the CZ, based on the burden temperature distribution and composition. In addition, an under-relaxation scheme has been developed to obtain layered CZ shape which explicitly considered the layer structure inside the CZ. The user friendly software package named Blast Furnace Shaft Simulator (BFSS) has been developed to simulate the blast furnace shaft process. The BFSS software package has been used for the optimization of burden and gas distributions to maximize gas utilization with proper furnace permeability for given burden materials, productivities, and blast furnaces; and also to optimize the burden and gas distributions for high fuel injection rate and low coke rate. The research has significant benefits to the steel industry with high productivity, low energy consumption, and improved environment. Using the BFSS, it is possible to design, optimize, and trouble shoot the blast furnace operation.
Degree
Ph.D.
Advisors
FLEETER, Purdue University.
Subject Area
Mechanical engineering
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