| Vanadium-titanium magnetite is a symbiotic compound mineral including Fe, V, Ti, Cr and other elements with high comprehensive utilization value. Panzhihua in Sichuan province and Chengde in Hebei province are two important origins of vanadium-titanium magnetite in China. Some domestic iron and steel enterprise has been smelting vanadium-titanium magnetite in blast furnace for many years taking the advantage of its geographical advantage. With the increasing of vanadium-titanium magnetite ratio, the enterprise is faced with a lot of problems on vanadium-titanium magnetite production in blast furnace, including poor BF comprehensive burden softening-dripping behaviorss, low recovery rate of V, Cr et al. As people known more and more about the relationship between BF burden structure, furnace charge composition and charging system with the smelting, seeking reasonable burden structure, furnace charge composition and charging system as effective means to improve production and save coke have been gradually accepted.Therefore, a experimental scheme was put forward to optimizing vanadium-titanium magnetite comprehensive burden softening-dripping behaviorss in blast furnace based on the domestic iron and steel enterprise production practice. Under laboratory conditions, we studied the effects of sinter basicity, content of MgO in sinter, ore-coke mixed charging rate on vanadium-titanium magnetite comprehensive burden softening-dripping behaviorss used vanadium-titanium sinter, vanadium-titanium pellet and coke as the basic raw material. Then we analyzed V, Cr content of initial dropped iron and V, Cr recovery ratio in different experiment series. Finally mechanism analysis was conducted. Several conclusions were obtained as follows:(1) A appropriate increase of sinter basicity was helpful to improve the softening-dripping behaviorss of vanadium-titanium magnetite comprehensive burden in blast furnace. With the increasing of sinter basicity, the softening range (T40-T4) tended to widening from 149.3 ℃ to 181.7℃, both the melting start temperature Ts and the dripping temperature TD tended to increasing then decreasing., the melting range tended to be obviously narrowed from 178.0 ℃ to 136.7℃, the softening-dripping behaviors was improved, gas permeability became better and the dripping ratio tended to increasing then decreasing, the maximum was 74.5% when sinter basicity was 2.13, both V, Cr in the initial iron and the recovery rate of V, Cr increased. From the perspective of softening-dripping behaviors, sinter basicity should not be less than 2.13, the corresponding ratio of oxidized pellets was not less than 38%;(2) The increase of MgO in sinter had a great influence on the softening-dripping behaviors of vanadium-titanium magnetite comprehensive burden in blast furnace. With the increasing of MgO in sinter, the softening range (T40-T4) tended to be a little wider from 142.5℃ to 153.5℃, the melting start temperature Ts gradually increased, the dripping temperature To also gradually increased, the melting range (TD-Ts) tended to be wider from 190.1℃ to 216.4℃, the gas permeability tended to be better then bad and the dripping rate tended to be declining, both V, Cr in the initial iron and the recovery rate of V, Cr decreased. In conclusion, increasing of MgO in sinter was not conducive to strengthening blast furnace smelting. It was better to control a reasonable content of MgO in sinter under the promise of meeting BF slag requirements; From the perspective of softening-dripping behaviors, the advisable content of MgO in the sinter was around 2.98%-3.40%, then the content of MgO in BF slag was about 11.46% -12.72%;(3) A certain ratio of ore-coke mixed charging was helpful to improve the softening-dripping behaviors of vanadium-titanium magnetite comprehensive burden in blast furnace. With the increase of ore-coke mixed charging ratio from 0% to 40%, the softening range (T40-T4) tended to be wider from 147℃ to 201℃. When the ratio increased from 40% to 50%, (T40-T4) was narrowed to 160℃, then remained unchanged. When the ratio increased from 0% to 25%, the melting range (TD-Ts) was greatly narrowed from 230.4℃ to 167.0℃. The ratio further increased, (TD-TS) remained unchanged; With the increase of ore-coke mixed charging ratio, gas permeability became better and the dripping ratio tended to increasing then decreasing, the maximum was 63.3% when the optimal ore-coke mixed charging ratio was 35%, the recovery ratio of V, Cr in initial iron tended to increasing then decreasing and they respectively reached maximum 27.624% and 47.628% when the optimal ore-coke mixed charging ratio was 35%. From the perspective of softening-dripping behaviors, the optimal ore-coke mixed charging ratio was 35%-50%, but 35% was the best.(4) In 1350m3 BF practial production the sinter basicity was 2.1, content of MgO in sinter was 2.94%, ore-coke mixed charging ratio was 20%. Compared with that before optimization, both slag fluidity and desulfurization ability was enhanced. Net coke rate was reduced from 428.09 to 364.46 kg/tHM, coal rate rised from 112 to 133.75 kg/tHM, moreover, comprehensive coke rate reduced from 537.51 to 485.52 kg/tHM. Gas utilization rised from 43.64% to 49.76%, content of [V] increased from 0.27% to 0.31%, BF utilization coefficient improved and it reached 2.65 t/(m3 · d) from July to September. |
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