Abstract
Limonitic laterite contains low iron and nickel grades and much high smelting minerals and loss on ignition (LOI), identified as refractory iron ore for sintering. Thus, sinter pot tests of limonitic laterite via pressurized densification sintering and its intensification mechanism were conducted, and the industrial application prospect was explored. The results indicate that the sintering performance of the limonitic laterite of the new process is significantly improved with the tumble index and productivity increased by 19.2% and 18.6%, respectively, and solid fuel rate lowered by 10.3%. The external pressure field promotes the synchronization of heat front velocity and combustion front velocity for better sintering heat and mass transfer conditions, which also greatly improves the mineral compositions and microstructure of the product sinter. The microstructure is converted from large thin-wall pores into small thin-wall or large thick-wall pores with the sinter porosity decreased by 42.4%. Much close interlocking texture between hercynite and silico-ferrite of calcium and alumina (SFCA) is formed with hercynite grains aggregation and growth, and SFCA amount substantially increased. The better sintering performance will bring about a remarkable economic benefit of 282.78 million RMB/a if the industrial application is implemented. The pressurized densification sintering process is considered as one of the effective technologies for improving limonitic laterite sintering.
Highlights
As the worldwide demand for stainless steel products increasingly exceeds supply, nickel sulfide resources acting as the main source of extracting nickel for stainless steel are sharply depleted [1,2,3].the abundant nickel laterite resources with a share of as high as 70% of total nickel resources tend to be more and more concerning [4,5,6]
It is noteworthy that limonitic laterite characterized as high-iron and low-nickel laterite ore accounts for 60% of the total nickel laterite resources, which has been massively imported from Indonesia and Philippines to China in recent years because of the scarcity of nickel laterite resources in China and the export restriction of high-grade laterite to overseas countries [7,8,9,10]
As confirmed in previous studies [13,14,15,16], the former is preferably applicable to high-nickel and low-iron laterite ore to produce ferronickel containing 10–25% Ni with the vast majority of iron left in the slag, while limonitic laterite is suitable for the sintering-blast furnace process to produce low-grade ferronickel alloy at lower cost owing to its comparatively higher iron grade and lower price
Summary
As the worldwide demand for stainless steel products increasingly exceeds supply, nickel sulfide resources acting as the main source of extracting nickel for stainless steel are sharply depleted [1,2,3]. According to the studies of high-proportioned ordinary limonite ore sintering [32,33], many investigations have been conducted on improving the sinter microstructure of limonitic laterite through blending the laterite ore with ordinary iron ores such as magnetite concentrates for sintering This method is proved to be an alternative way to reduce sinter porosity and improve the relevant sintering performance, the nickel grade of pig iron is weakened while the proportion of limonitic laterite is always no more than 50%, which is unfavorable for the extensive utilization of limonitic laterite and the production of stainless steel at low cost [34,35].
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