Study On Settlement And Curing Basis Of Iron Tailings

Iron tailings, refered to the emissions of fine slag after magnetic separation based on their properties, which is made through grinding broken ores to a certain fineness in a ball mill with appropriate water. Because of the lower efficiency, large amounts of iron tailings are just piled up for damp building. However, due to the iron tailings’ high moisture content, the dam bodies are not stable, and easy to cause huge risk in damp building. Therefore, seeking a safe tailings storage technology is of great significance to mining enterprises.In this paper, we choose the iron tailings which are from Roots area as the object of study. We analyzed the physical and chemical properties of the iron tailings, then researched the factors affecting on its sedimentation and solidification, thus provided theoretical basis for its solidified pile up and cemented filling. The results are summaried as follows:(1) The iron tailings mainly consisted of SiO2、Al2O3、Na2O、CaO、Fe3O4, and the mineral phases were mainly quartz. The iron tailings were fine-grained tailings, whose particles were range from 7.85μm-77.1 μm in size, accounted for over 85% of total quantity. Iron tailings belonged to the range of high permeable soil, because of the 1.94×10-4 cm/s of average permeability coefficient. Since its average internal friction angle were 16° as well as the average cohesion were 0.16KPa, the storage stability of the iron tailings were obviously low.(2) The concentration of iron tailings slurry was about 30%, and this value can rise to 50% in 90 min after natural sedimentation, which could meet the requirements of concentration for the solidified pile up of iron tailings. However, in order to meet the requirement of concentration for cemented filling of iron tailings, the concentration reach 60% in 90 min after natural sedimentation, proper kinds of flocculants would be needed. In this paper, four kinds of flocculants like PAM, PAC, SDBS and CMC were researched. They have been proved to be effective to the enhancement of sedimentation of iron tailings, and we discussed the most proper dosage range of these flocculants.(3) By conducting orthogonal experiment based on four factors and three levels, the mixed effect among the four flocculants were investigated. Finally, PAM> PAC and CMC were chosen according to the results of orthogonal experiment, and also got the optimal ratio PAM:PAC:CMC=6:3:2. In addition, through testing on the optimal dosage of compound flocculant,3.0%o was determined to be the optimal value, which can help to increase the initial sedimentation layer concentration from 20.57% to 63.47% after being adding the iron tailings slurry (in contrast, by natural sedimentation for 90 min, the iron tailings slurry was just increased from 30% to 52.64%). This can meet the requirement of concentration for cemented filling of iron tailings.(4) In this paper, single factor experiments were conducted to investigate the influence of different dosages of curing agent to iron tailings solidified bodies, and concluded the optimal dosage range of the curing agent. The optimal ratio of them are: mineral activator:26%, desulfurization gypsum:5%, alkali activavator:6%, fly ash; 8%, slag:55%. In addition, proper admixture with optimal solution were determined through single factor experiments:NC:0.6%, NS:1.6%, NCO,0.2%, FC:0.8%, of which the dosage should be 3.2% of the total added curing agent.(5)In this paper, the effect of technique parameters was investigated (dosage of curing agent and concentration of iron tailing slurry) on the property of solidified bodies of iron tailings, the experiment results showed that:For the iron tailings slurry with 50% concentration, adding curing agent with dosage of 5%would make the tailing solidified body with 0.32MPa strength,122.3KPa cohesion,28.6°nternal friction angle in 7 days, and later 0.56MPa strength,154.7KPa cohesion,33.5°nternal friction angle in 28 days, which can fully meet the requirement for solidified pile up of iron tailings in practical production. While, for the iron tailings slurry with 60% concentration, adding curing agent with dosage over 10% would make the tailing solidified body with 0.51MPa strength,142.3KPa cohesion,32.1°nternal friction angle in 7 days, and later 0.78MPa strength,169.4KPa cohesion,36.7 internal friction angle in 28 days, which can fully meet the requirement for cemented filling of iron tailing in practical production. Through conducting experiment on the water stability of iron tailings solidified body, we could know that when the iron tailings slurry concentration was 50% and the dosage of the curing agent was over 5%, no mud phenomenon or distortion would happen to solidified body of iron tailings when soaked in water, which could meet the requirements for stable pile up of iron tailings.(6) Comparing the hydration products’XRD patterns of original iron tailings and solidified body of iron tailings, in the presence of the curing agent, the solidified body of iron tailings would produce the sialic acid salts and sulfur aluminum silicate minerals consist of Ca、Si、Al、Selements after hydration reaction, which was the main source of the strength of the solidified body of iron tailings. According to the analysis result of SEM, the initial pile-up of iron tailing particles, together with the folding sheets and needle bars of hydration products, would go on a process of intertwining, filling and wraping each other before becoming a compact structure, increasing the strength of solidified body in some degree.(7) In this paper, based on the production capacity of annual 200000 tons of iron tailings curing agent, the production cost of curing agents was calculated. Comparing with the conventional cement curing agent, the curing agent proposed in this paper possesses advantages including lower production cost and less limitation on funds. Based on processing capacity of annual 4 million tons of iron tailings curing agent, and through economic analysis of production equipment, raw materials and processing cost, we concluded that compared with the conventional piling up technique, the iron tailings curing technology was more simple in the aspect of technology, higher stability of piling up storage, and lower investment cost.