Fundamental Study On Synergistic Reduction Of Vanadium Extraction Tailings With High Content Chromium And Chromite To Smelt High Carbon Ferrochromium

Hongge ore is the largest vanadium-titanium magnetite resource in Panxi area of China.The proven reserves in south hongge mining area are up to 1.9 billion tons,and the contents of iron,vanadium,titanium and other elements in the raw ore of south hongge mining area are similar to that of other mining areas in Panxi,but the content of Cr₂O₃ is 5 to 10 times that of other mining areas in Panxi,and the chromium resource reserves are up to 9 million tons.Chromium resources are extremely poor in China,and over 97%of them depend on imports.The amount of chromium resources in south hongge mining area is equivalent to the proven chromium reserves in China,which is of great utilization value.Focusing on the high efficiency,clean,large-scale and low-cost utilization of Hongge mine,many domestic scientific research institutions had carried out technical research to tackle the key problems and initially formed the smelting process of"ironmaking by blast furnace-extraction vanadium and chromium by converter".Based on this process,the vanadium in the vanadium chromium slag can be extracted by the existing hydrometallurgical extraction process.However,the content of Cr₂O₃ in vanadium extraction tailings with high content chromium is as high as 5.00%to 13.00%,which is much higher than that in the common vanadium extraction tailings.At present,there is no mature and economic extraction process.The vanadium extraction tailings with high content chromium are toxic solid wastes.If they are discarded,which will cause serious environmental pollution.Therefore,synergistic reduction of vanadium extraction tailings with high content chromium and chromite to smelt high carbon ferrochromium is proposed in this study.Through theoretical calculation and experiments,the element migration law,phase evolution and the influencing factors in the smelting process are systematically studied.The toxicity test of slag before and after reduction is carried out,which provides a reference for the comprehensive utilization of vanadium extraction tailings with high content chromium.The theoretical calculation results show that compared with the reduction process of chromite,the disappearance temperature of chromium containing phases and the formation temperature of liquid slag in the synergistic reduction process of vanadium extraction tailings with high content chromium and chromite are 40?and 20?ahead of time,respectively.Compared with the reduction process of vanadium extraction tailings with high content chromium,the disappearance temperature of iron containing phases is 100?ahead of time.The reduction experiments show that iron oxides are reduced almost entriely at 1100?.The(Cr,Fe)₇C₃ phase formes at 1200?.The metal particles forme at 1400?,and the reduction rate reaches 96.24%at 1500?.Compared with the reduction process of chromite,the complete reduction temperature of iron cotaining phases and the formation temperature of(Cr,Fe)₇C₃ phase are all 100?ahead of time.When the smelting conditions are as follows:the mass ratio of chromite and vanadium extraction tailings with high content chromium is 5:1;the additive amount of Si O₂ is 5.08%;the additive amount of graphite is 20.54%,the reductant is graphite;the reduction and melting time is 35 minutes.The composition of high carbon ferrochrome gained at above conditions is Cr 50.74%,Fe 37.50%,C 8.77%,Si 1.35%,P 0.005%,S0.014%;recoveries of chromium,iron and metal are 95.18%,93.49%and 96.17%,respectively.During the process of synergistic reduction of vanadiunm extraction tailings with high content chromium without desulfurization and chromite to smelt high carbon ferrochrimium,when the additive amount of Ca O is 10.45%,the sulfur content in high carbon ferrochromium can be reduced from 0.11%to 0.04%,and the desulfurization rate is 61.90%.The leaching amount of Cr(VI)in vanadium extraction tailings with high content chromium is 2.41 mg/L,and the total vanadium leaching amount is 4.28 mg/L.The leaching amount of Cr(VI)in the reduced slag is only 0.04mg/L,and no vanadium is detected in reduced slag.The reduction and smelting process realizes the detoxification treatment of the vanadium extraction tailings with high content chromium.