Theoretical Exploration On Oxygen Blast Furnace Process

Conventional blast furnace process is still the main ironmaking process nowadays, for its high thermal efficiency and hot metal of high quality. However, it is also under the high pressure of cutting down the carbon dioxide emission. Oxygen blast furnace is a new ironmaking process with cold pure oxygen instead of hot balst injected at hearth tuyeres. Oxygen blast furnace with carbon caputre and storage (CCS) is just the process that can dramatically reduce the carbon dioxide emission by at least 50 percent of today’s best routes. Top gas recycling blast furnace (TGR-BF) is the most promising oxygen blast furnace process that can be realized under industrial production conditions. But most of the mathematical models that have been proposed are not appropriate, since direct reduction ratio (DDR) is assumed in these models without any experimental data to reference. That is to say, DDR chosen is blind. What’s more, DDR is always varying according to operational conditions, thus DDR chosen is difficult to meet the actual fact.Taking the characteristic of blast furnace into consideration, the blast furnace at steady state is divided into three parts, namely raceway zone, the higher temperature zone and the lower temperature zone. On the basis of mass balance and heat balance, a mathematical model is established and then programmed with visual basic. The model can be used to analys not only the conventional blast furnace, but also the oxygen blast process under different operating conditions. There are three main oxygen blast furnace processes, which differ with each other on gas injection temperature or the position of the injection points. The effect of pulverized coal injection (PCI) ratio and oxygen ratio of the blast on the above 3 blast furnace process is ayalyzed in the paper, and some conclusions have been made form the calculation results.(1) The conventional blast furnace is still able to operate smoothly when oxygen ratio of the blast is within 0.353. The conventional blast furnace process will fail when oxygen ratio of the blast is beyond 0.353.(2) In the TGR-BF process, the decarbonated product gas injected at the shaft tueyers is mainly to heat the raw materials, and has few effects on the reduction of iron ore.(3) The carbon saving of oxygen blast furnace process is analyzed compared to conventional blast furnace process. For the process with the product gas injected cold at the hearth and hot at the shaft tuyeres, the forssil carbon consumption is reduced by 12.9kg/thm, when PCI rate is 150kg/thm, volume of decarbonated prodect gas injected at the hearth tuyeres is 400.5Nm3/thm and 163.1Nm3/thm at the shaft tuyeres. For the process with prodect gas injected hot both at the hearth tuyeres and shaft tuyeres, the forssil carbon consumption is reduced by 90.5kg/thm, when PCI rate is 162kg/thm, volume of decarbonated product gas injected at the hearth tuyeres is 535.4Nm3/thm and 10.5Nm3/thm at the shaft tuyeres.(4) For the oxygen blast furnace process with product gas injected hot only at hearth tuyeres, the forssil carbon consumption can be reduced by 91.0kg/thm, when PCI rate is 200kg/thm, volume of decarbonated prodect gas injected at the hearth tuyeres is 535.4Nm3/thm. However, it requires operating the BF either at very low flame temperature to reach competitive carbon savings.(5) For oxygen blast furnace with coke oven gas injected at the hearth tuyeres, the forssil carbon consumption can be reduced by 15.8kg/thm, when PCI rate is 200kg/thm and volume of decarbonated top gas injected at the hearth tuyeres is 247.1Nm3/thm.