Study On A New Process For Direct Reduction Iron And Cementitious Materials By Laterite Nickel Ores

In recent years, the rapid development of Chinese stainless steel industry lead to the shortage of nickel. The world nickel raw materials which is used for niekcl sulfide is about 60%, but the account of nickel sulfide for only about 28% of the total nickel resources. With the depletion of nickel sulfide ores, laterite nickel ores have become increasingly important as a source of nickel. And it is becoming very necessary to research laterites due to the shortage of domestic laterite nickel resource. Therefore, in the long term it is necessary to develop new and more economical processing technologies, so as to achieve the optimum resource utilization.In this paper, a novel process route for extracting ferronickel and cementitious material from laterite ore as raw material was suggested. The coupling of the metal oxide reduction and the formation of the cementitious material in cement is the main targetby reasonable composition and temperature control. After grinding and magnetic separation, metal with nickel and cementitious materialcan be obtained in the same time. It is possible an effective way of multi-purpose utilization of the laterite nickel ore.In this work, the impacts from reduction temperature, reduction time, additive ratio to the index, reductants ratio, reaction atmosphere are mainlyinvestigated by thermodynamic analysis(Factsage software), phasedetection(XRD, SEM, EDS) and laboratory test. The main conclusions were obtained as follows:(1)Thermodynamic analysis showed that the reduction of metal oxide in the raw material from easily to difficult is in the sequence of Fe2O3, Fe2O3, NiO, CoO, Fe3O4, FeO and Cr2O3. 2CaO·Fe2O3 can be reduced by C when temperature is over 910.6?, and the reduction of 2CaO·Fe2O3 in the raw material from easily to difficult is in the sequence of 2CaO·Fe2O3?CaO,Fe3O4?CaO,FeO?Fe. At temperatures below 1300?, the formation of C2 S is prior to C3 S. With the increase of temperature from 1300?, C2 S was partly transformed into C3 S with CaO. The temperature of reaction is range 1300? to 1800?, and the reaction is the fastest at 1450?.(2)The experimental results showed that the highest content of C2 S was 75.21% when the quantity of coal was tenty percent of laterite nickel ores, the basicity was 2.9 and reducting was 1450? for 60 min. But the reaction products haven't iron due to excessive calcium oxide, the bad reaction dynamics condition and reaction atmosphere. In the two step method of heating experiment, there is C3 S in the products(its content is about 30% ~ 50%). With the increase of carbon content, the content of C3 S was first increased and then decreased. And the the content of C3 S is the opposite. The reduction time has great effects on the formation of C3 S, the reduction timechanged from 1h to2 h, the content of C3 S increased from 33% to 52% in the 14% carbon content, reduction temperature of 1450?.(3)To improve thedynamic conditionsof reduction reaction and ensure the reducing atmosphere, such as the reaction products have 8% nickel iron, 34%C3S and 38% C2 S by 30% coal, 1000?for 15 min, 1450? for 60 min in strong reducing atmosphere. The reduction rate of metallic iron is 72.7%. The reduction rate of metallic nickel is 80%.