Sintering Behaviour And Process Optimization Of Nickel Laterite Based Of Limonitic Style

Nickel is an essential element for the production of stainless steel. In recentdecade, the grade rapid increase of stainless steel in China has led to a great demandfor nickel with the rapid increase of economic of China. Nickel is usually extractedfrom two distinct ore types: nickel sulphide deposits and nickel laterite. With thecontinuouss depletion of sulfide nickel deposits, the development and utilization ofnickel laterite attacted more and more attention. Rotary kiln-electric furnace process(RKEF) is widely used in the production of ferronickel from nickel laterite. The cost ofthe RKEF process increases with using the low grade nickel laterite. In recent years,the sintering–blast furnace process used to deal with the nickel laterite based oflimonitic style put forward by some factories in China obtained spread and application.However, the lack of basic research and practical application of the sintering–blastfurnace process used to deal with nickel laterite ore is serious. So, it is important tostudy the sintering-blast furnace process used to deal with low nickel laterite based ofLimonitic Style.The high content of water of nickel laterite based of limonitic style lead to thepoor permeability of mixture, high cost and low yield during sintering process.Increasing carbon addition was the only way to improve the yield, but the high contentof FeO and poor reduction of sinter came with increasing carbon addition.Nickel laterite based of limonitic style was used as the raw material in this study.The basic properties of raw materials, granulation process and sintering process werestudied by theoretical and experimental in this study. Several conclusions were shownas follow:①The main mineral phase of limonitic nickel laterite was（FeO(OH)）,(Al(OH)3)and a little of NiFe2O4. The content of Fe and Ni was46.04%and1.2%respectively.The content of crystal water of nickel laterite after drying reaches10.87%, The contentof hydroxyl of nickel laterite after drying reaches3.71%。②The particle size of mixture decreased with decreasing the ratio of wateraddition between secondary mix and first mix. The permeability index increased whenthe ratio of water addition between secondary mix and first mix decreased to60%, andthen decreased when it continuously decreased. Contrary regularity was found for thefraction dimension (D). In the range of14%to20%water addition, the permeability of the green bed, the reasonable and uniformity of the particle size of granules improvedwith increasing the water addition. However, Excess wetness of sinter bed appearedwhen the water addition increased to20%. So, the optimal water addition was18%.The permeability of the green bed of granules and the reasonable and uniformity of theparticle size of granules improved with the time of the secondary mix increasing to6min, and decreased afterward.③The FeO content of sinter increased with increasing the carbon addition. Themain mineral phase of nickel laterite sintering was Fe3O4, MgFe2O4, NiFe2O4,NiFeAlO4and FeO. The main mineral phase of binder was (Fe2SiO4), MgCaSiO4whenthe basicity was1.0~1.3, and the main mineral phase of binder was (Fe2SiO4),MgCaSiO4and (SFCA) when the basicity was1.5~2.1.④The yield of sinter increased from63.29%to81.44with increasing the carbonaddition from6%to12%, and then, the yield decreased to78.80%when the carbonaddition increased to16%. The shatter strength of sinter increased from60.18%to85.40%with increasing carbon addition from6%to12%and decreased afterwards.Tumbler strength of the sinter obtained19.78%improvement with increasing thecarbon addition from6%to12%, and then decreased when the carbon additioncontinued to increase. Opposite regularities were found for the abrasion index of thesinter. The low temperature reduction disintegration of the sinter was good when thecarbon addition was6%~16%, and increased with the carbon addition increasing. Thebetter performance sinter was obtained when the carbon addition was9~12%.⑤The result of theoretical calculation showed that quantity of liquid phaseincreased gradually with increasing sinter temperature, the starting liquid temperatureincreased when the basicity increased to1.9. In addition, the quantity of the liquidphase increased with the temperature increasing after the temperature reached to1300℃. The FeO content of the sinter increased with increasing the basicity. When thebasicity was1.0~1.2, the mineral phase of the sinter was mainly secondary magnetiteand olivine, olivine phase distributed in the secondary magnetite phase. When thebasicity was1.3~1.5, the magnetite in the sinter approximately maintained theoriginal shape and edge, and olivine fills in the magnetite crystal. When the basicitywas1.7~2.1, the crystallin grain of magnetite phase, olivine and calcium ferrite phasein the sinter were irregular and embeded with each other. The macroporous structureappeared after the basicity increased to1.7, this structure could damage the strength ofthe sinter. ⑥As the basicity increased from1.0to1.3, the yield increased from73.8%to80.23%, and then, the yield hardly change afterwards. Similar regularity were foundfor the shatter strength of the sinter，and the highest value was84.63%, which wasobtained when the basicity was1.3. As the basicity increased from1.0to1.2, drumstrength rapidly grew from57.78%to69.73%, and decreased afterward. Abrasionindex increased with increasing the basicity to1.5and then decreased afterwards. Thereduction degree increased with increasing the basicity. Simalr regular was found forthe reduction rate index. The better performance sinter was obtained when the basicityis9~12%.