| Carbon saving and emission reduction in blast furnace ironmaking is an important way of reducing energy consumption and CO2and other pollutants emission in iron and steel enterprise. The Carbon saving and emission reduction capacity of Top Gas Recycling Oxygen Blast Furnace ironmaking technology (namely oxygen blast furnace) has been demonstrated by theoretical calculation and BF test. The process is characterized by pure oxygen instead of the traditional hot blast and recycling the top gas after CO2removal. Thereinto, top gas recycling is one of key technologies of oxygen blast furnace process. Therefore, in this paper shaft cycle gas injection in oxygen blast furnace was investigated by cold physical simulation and simulated calculation. Based on the hot state experimental of iron ore reduction, a coupling mathematical model of heat transfer and chemical reactions between gas-solid in oxygen blast furnace shaft was established. Furthermore, the interfacial resistance during gas rising process in shaft and carbon deposition behaviors during heating gas were investigated. These researches provide fundamental basis for OBF’s design and development.The gas distribution behaviors at shaft gas injection in oxygen blast furnace were studied experimentally using a2D cold model. The experimental results show that the ratio of injected gas flow rate to the total gas flow rate in shaft plays a decisive role to the gas distribution behaviors at shaft gas injection, while the influence of total flow rate is little. Meanwhile, the gas distribution in shaft is divided to two dissimilar zones, a main flow region of injected gas and a main flow region of upward gas, at shaft gas injection. Futhermore, the gas flow inside furnace was simulated numerically by establishing2D mathematical model based on cold physical model geometry above. The results show that the gas flow miscibility is not strong between the injected gas and upward gas from the lower part. The influence of shaft gas injection on the vicinity of auxiliary tuyere inside furnace is larger.Using the programmed reduction and softening-melting experiment apparatuses, the reduction, softening and melting behaviors of mixture ore were examined by simulating the conditions in traditional BF (TBF) and typical OBF. On this basis, a coupling mathematical model of heat transfer and chemical reactions between gas-solid above cohesive zone (CZ) in TBF and OBF were established. The model reliability of TBF and OBF was verified by comparsing with TBF anatomy results and material balance model established previous in our lab. The simulation calculation results show that compared with TBF, the thermal reserving zone in OBF is significantly expanded. Temperature distribution in the other position inside OBF is similar with that in TBF."Too cold in shaft" problem in OBF is solved very well by shaft gas injection. Meanwhile, both CO and H2concentrations are higher in OBF. The differences between the solid temperature distributions are little for different shapes CZ. Additionally, the influence of the diameter and angular transformation of auxiliary tuyere on the temperature and gas concentration distributions is little.The influence of redcuing coke rate and resistance variation between alternate burdens at shaft in OBF on pressure drop inside furnace is large. Thus, the interfacial resistance between alternating layers of coke and metallic burden and the effect of it on the total pressure drop were investigated by using three-dimensional cold physical model. Meanwhile, a new pore-throat equation is imported to forecast blast furnace gas permeability. The results show that the total pressure drop and interfacial pressure drop are increasing with flow rate and interlace numbers. And the experiential relation between interface resistance and physical parameters, flow rate and interface numbers is deduced as which is combined with pore-throat equation to predict the total pressure drop. The pressure drop correction formula is proved to be more suitable comparing the experimental values and calculated value under various layers thickness. Additionally, the interfacial porosity shows a slight oscillating behavior with decreasing amplitude which isn’t strong.The carbon deposition behaviors in100%CO, the gas mixture of CO and H2and the cycle gas of OBF were investigated respectively at the ranges from300℃to700℃by using self-designed experimental facility. The results show that the carbon deposition behaviors of100%CO were not obvious under the laboratory condition. The carbon deposition reaction rates increases with the increase of temperature in heating the gas mixture of CO and H2. The carbon deposition is the most serious at500℃and600℃but reduces at700℃. The acceleration role of H2is more obvious with the increase of H2%in CO-H2gas mixture. The impact laws of temperatures on the carbon deposition in heating cycle gas of OBF are consistent with that mentioned above. The increase of temperature accelerates the carbon deposition reaction rates when the temperature is less than500℃. On the contrary, the result is just the opposite. Furthermore, CO decomposition reaction plays a leading role during carbon deposition process. Increasing CO2concentration (volume fraction) can retard effectively the carbon deposition behaviors.The carbon deposition reaction rates gradually reduces as CO2%(volume fraction) is increasing. |
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