Study On The Reduction Characteristics Of Laterite Nickel Ore In Methane Atmosphere With Sulfur-containing Additive

Nickel is an important strategic metal resource,widely used in steel,military,aerospace,chemical and other fields,plays a vital role in the development and growth of a country.Currently,the world’s exploitable nickel ore is mainly divided into nickel sulfide ore and nickel oxide ore（laterite nickel ore）.With the increasing scarcity of high-quality nickel sulfide ore,the resource rich laterite nickel ore has become an important raw material for nickel extraction.In the current context of"dual carbon",gas based smelting processes using clean energy as a reducing agent receive great attention.This article selects a laterite nickel mine from a certain place in Yunnan Province as the research object.The Ni content and Fe content of the sample is 0.82%and 9.67%,respectively.Firstly,chemical analysis,XRD,SEM,and TG-DSC were used to analyze the properties of the raw ore.An experimental study on the reduction of laterite nickel by methane was conducted in a tubular furnace with good air tightness.The effects of different process parameters on the metallization rates of nickel and iron were investigated.The migration and aggregation rules of ferronickel under the action of different additives were analyzed by SEM-EDS.The obtained research results are as follows:（1）According to the analysis of raw materials of laterite nickel ore,the laterite nickel ore belongs to a typical low grade silicon magnesium type laterite nickel ore.The main phase is serpentine phase,and nickel mainly exists in serpentine phase in the form of isomorphism replacing magnesium,with a relatively dispersed distribution.（2）When using elemental sulfur as an additive,the optimal process conditions obtained through experiments are:reduction temperature 800℃,methane concentration20%,reduction time 60 min,and elemental sulfur addition amount 4%.Under the optimal process conditions,the metallization rates of nickel and iron in the reduction products can reach 98.01%and 8.44%,respectively.When sodium sulfide is used as an additive,the metallization rates of nickel and iron in the reduction products obtained under the conditions of reduction temperature of 900℃,methane concentration of 20%,reduction time of 60 minutes,and sodium sulfide addition of 10%can reach 89.05%and5.10%,respectively.After methane reduction of laterite nickel ore,nickel oxide is almost completely reduced to metal nickel,while iron oxide is partially reduced to metal iron,most of which exists in the form of low-price oxide of iron（ferrous oxide）.Under the action of additive elemental sulfur,part of metallic iron is sulfurized to form FeS.（3）Sodium sulfide has both the dual functions of alkali metal salts and sulfur containing agents.The addition of sodium sulfide destroys the structure of the silicate in the mineral.The displacement reaction between Na⁺and Ni²⁺releases the nickel element present in the gangue.Making the reduction of nickel easier.Under the action of acidic oxides,sodium sulfide reacts with ferrous oxide to form a low melting point FeS phase,which reduces the melting point of the reduction system,enhances mass transfer conditions,and promotes further aggregation of metal particles.（4）After the reduction product is melted and separated at high temperature,the nickel iron particles further aggregate and grow up,and the impurities become less.The phase density of Mg₂Si O₄ and Mg₂Si O₃ in laterite nickel ore at high temperature is greater than that of nickel and iron.The density of Ni and Fe is similar.During the migration process in the melt,due to their similar properties,they aggregate with each other,and finally complete the migration and aggregation process of Ni and Fe particles.