Oxidation Behavior Of Metallurgical Silicon Slag And Preparation And Properties Of Porous Materials

Metallurgical silicon slag consisting of a certain amount of Si and SiO2 is the solid residue of silicon metallurgy, which is used as paving and building materials. In this paper, oxidation kinetics of metallurgical silicon slag and preparation of porous materials were investigated. The oxidation behavior of metallurgical silicon slag and structure and property of porous materials were investigated by XRD、TG-DTA-MS、SEM. These researches not only provide a new way to solve the recycling problem of metallurgical silicon slag, but also help reduce the production cost of porous material,leading to significant economic and ecological benefits.The oxidation process of metallurgical silicon slag was very complicated. The content of C, Si and SiC decreased with increasing oxidation temperature and extending of holding time. C disappeared after 1000 ℃, cristobalite and crystallinity decreased with increasing oxidation temperature. The content of cristobalite and tridymite increased gradually when temperature holded in 1100 ℃, crystallinity is gradually decreased before 10 h, and increased more than 10 h. Using the Coats-Redfern integral method to deduce reaction activation energy E of metallurgical silicon slag in different oxidation phase: the value of E of Si and SiC at 820-1200 ℃ in the mass gain phase was biggest; then was at 420-820 ℃ in the mixed weight lose phase; the value of E of C at100-420 ℃ in the mass loss phase was lowest.The diameter of porous materials prepared from metallurgical silicon slag by direct sintering increased with the increasing of waste glass and sintering temperature, and it decreased with extension of holding time and increment of heating rate. The apparent density of porous materials decreased with the increasing of waste glass and increment of heating rate, increased with the increasing of holding time, and it initially decreased and then increased with the increasing of sintering temperature. The change trend of porosity was opposite to it. The compressive strength of porous materials initially increased and then decreased quickly with the increasing of sintering temperature. The apparent density of porous materials prepared by direct sintering was 0.37-0.47 g/cm3 and compressive strength was 0.67-1.60 MPa.The diameter of porous materials prepared by sintering after water quenching increased with the increasing of sintering temperature and holding time, and initially increased and then decreased with increment of the heating rate. The apparent densityincreased with extending of the holding time, and initially decreased and then increased with the increase of the sintering temperature and heating rate. However, the change trend of porosity was opposite to the apparent density. The compressive strength of porous materials increased slowly and then decreased sharply with increasing sintering temperature. The apparent density of porous material was 0.65-1.12 g/cm3, and the compressive strength was 1.96-4.55 MPa.Porous materials prepared by metallurgical silicon slag have excellent strength,appropriate compressive strength, easy operating technology. The utilization ratio of metallurgical silicon slag is over 60%, and it can be used without adding foaming agent.Thus, the metallurgical silicon slag is expected to achieve low-cost, large-scale production of porous materials, which can be applied in heat preservation and heat insulation, filter media, catalyst carrier and other fields.