Research On The Composition Characteristics And Utilization Of Slag From Desulphurization And Slag Skimming

Composition characteristics and utilization of slag from desulphurization and slag skimming are studied in this paper. The sample was obtained from 1st steelmaking plant of ANSTEEL, processed by hot metal pretreatment. The desulfurizing agents used in the plant are passivation magnesium powder and pulverized lime. The output of this kind slag is 320 thousands tones each year in ANSTEEL, and many more time the slag is stored in slag dams because of the lack of effective means to deal with it. In order to achieve the goal of sustainable development, recycling these slag becomes necessary.Chemical analysis, optical microscope, XRD and SEM are adopted to research the composition characteristics of the slag. The tests demonstrate that the main useful element is iron, grade 54.18%, the main nocuous element is sulphur, grade 1.01%; The main iron phases in the slag are metal iron, magnetite, ferrosilite and wustite, and the recoverable iron phases account for 61.88%; The slag includes metallic iron, magnetite, ferrite, metasilicate, aluminate and so on, thereinto, the sulphur mostly occurs as calcium sulphide and sulphate; Size distribution results show that iron mostly distributes in coarse particles and sulphur mostly distributes in fine particles, but lots of sulphur is mingled with coarse particles, causing separation with difficulty. Based on the composition characteristics, tailing discarding experiment, grindability experiment, raising the iron and reducing the sulphur experiment were carried out. Tailing discarding experiment shows that, though iron grade is very low and sulphur grade is very high in fine particles, the fine particles still contain a spot of magnetite, so tailing discarding is not suitable to carry out; Lots of metal iron existing in the slag makes the grindability very bad, influencing separation index, so classification and separation was adopted to reclaim metal iron. +0.3mm part was reclaimed directly when the grinding fineness -0.074mm was 54.20%, -0.3mm part regarded as the core sample of the next experiment; Magnetic separation, gravity concentration, gravity-magnetic separation, magnetic -gravity concentration were adopted to reclaim the iron and remove the sulphur. The results indicate that the four flows all can get the eligible iron concentrate, but considering every separation index and the feasibility of production, gravity-magnetic separation was taken as the finally flow. When the grinding fineness -0.074mm of gravity concentrate is 50% and magnetic field strength is 108KA/m, the productive rate of concentrate is 41.46%, iron grade is 86.32%, recovery is 78.78%, sulphur grade is 0.21% and iron grade of tailing is16.76%.The XRD analysis result of tailing indicates that the tailing contains dicalcium silicate, magnesium ferrite, metal iron, tricalcium silicate and magnetite. The semiquantitative analysis shows that the content of dicalcium silicate and tricalcium silicate in the tailing is 82.00%, in order to realize the maximization uses of the slag, taking the tailing as cement clinker can be considered.