Iron Nuggets Preparing From High Silicon Dioxide Fe-Containing Nickel Slag By Direct Reduction

Nickel slag is one of by-products produced in the process of extracting nickel by the flash furnace.The stock of the accumulated nickel slag is up to 40 million tons and 2million tons slag will be produced each year in China.Nickel slag contains about 40%iron and trace nickel,copper and other valuable metals,therefore,it is a great potential secondary resource.The characteristics of ITmk3 process are low environmental pollution,low cost and shorter production period.It can make use of low grade and refractory ore resources,and the products are iron nuggets with similar properties to blast furnace hot metal,which can replace some scrap steels.To recover iron from nickel slag efficiently,nickel slag and are used as raw material and reducing agent in this paper,respectively.Besides,proper amount of calcium oxide?analytical pure?is addded in sample to press into nickel slag carbon-containing pellets to prepare iron nuggets by direct reduction.The main components of nickel slag are FeO?50.66%?,SiO2?32.5%?,MgO?9.7%?and CaO?1.2%?,respectively.The mass ratio of CaO in CaO-SiO2-MgO ternary slag system at lower temperature can be obtained by using FactSage thermodynamic software.When the mass R is 0.6,0.7,0.8,0.9 and 1.0.The liquid phase temperature range of reducted product slag is from 1350?to 1450?.According to ITmk3 process characters,the effects of different parameters,such as different sample equipments,temperature,basicity and reduction time,on the reduction process of nickel slag carbon-containing pellets were studied by using high temperature box furnace to simulate ITmk3 process.The results show that the iron and reduced slag of nickel slag carbon-bearing pellets of is separating well after reduction under the condition of that the reduction time is 12 min,the temperature is 1400?,the basicity is 0.8 and the reduction time is 12 min.The total iron content,carbon existing in the form of cementite,Ni,Cu and S of iron nuggets were93.89%,2.31%,1.04%,0.68%and 1.2%,respectively.The slag of reduction products is mainly composed of akermanite with stable chemical properties.The formation process of nickel slag carbon-containing pellets to iron nuggets are reduction reaction,carburizing reaction and slag iron aggregation separation,the second is the key step.A large amount of iron is produced by reduction of nickel slag carbon-containing pellets.With the carburizing reaction fully carried out,metal iron and reduction product slag gather separately.Due to the difference of interfacial tension,the separation of metal iron and reduction product is realized.The reduction kinetics of nickel slag carbon-containing pellets was studied by successive model.The reduction process of nickel slag carbon-containing pellets was controlled by gasification reaction and the activation energy of the reduction reaction is 199.64kJ·mol^-1.