Investigation of PO43- Removal in Aerated and Unaerated High Fe EAF-Slag Filter System

Phosphorus in wastewater is one the main culprit which accelerates eutrophication in waterbody if it is not being treated properly. Steel slag filter emerged as one alternative treatment for wastewater. However, the variousness of metal oxides including Fe in steel slag will affect the phosphorus removal efficiency. Thus, this study was conducted to investigate the ability of a series of lab-scale high Fe electric arc furnace (EAF- slag) column filters in removing PO43- from synthetic wastewater. The systems were operated under aerated and unaerated within acidic and alkaline conditions. Synthetic wastewater contained 25 mg/L was prepared as the feed and monitored weekly basis for the PO43- removal efficiency and the total metals (Ca, Fe, and Mg) concentrations in the effluents. The results show that both aerated and unaerated high Fe EAF-slag filter systems have high PO43- removal efficiency under acidic condition, which unaerated system performed slightly better. It can be observed that unaerated systems performed better in removing PO43- at acidic and neutral pH values but not at extremely high pH. As for the PO43- removal mechanism was achieved by adsorption and precipitation at acidic pH and the concentration of Ca, Mg and Fe in effluents was related to the PO43- removal efficiency at different pH values.

Study on Metal Transfer and Welding Spatter Characteristics of Basic Flux Cored Wire

The metal transfer behaviors of basic flux cored wire at different arc voltage and welding current and the resultant welding spatter were investigated by using a high speed camera. Two modes of metal transfer are found: globular repelled transfer (lower welding parameters) and small droplet transfer (higher welding parameters). The former is accompanied by large granular spatter, large droplet itself explosion spatter and electric explosive spatter of short-circuit, and spatter in the latter is reduced obviously. But if the slag column is found in the two models, spatter could be dropped evidently owing to its significant guiding role for metal transfer. Therefore the slag column is the key factor of reducing welding spatter.

Influence of Fe2O3 on Molten Slag Properties in Slag Splashing on Nickel Smelting Converter

To predict the effect of Fe2O3 on slag splashing properties in the nickel smelting converter, Factsage software was used to calculate the proportion of the liquid phase and the viscosity for MgO-FeO-Fe2O3-SiO2 melts, the melting temperature was measured using slag column deformation, and the microstructure was also observed. The results show that, when the content of Fe2O3 is increased from 13.79% to 24.14%, the liquid phase at 1250°C maintains a high proportion of 82.68% and the melting temperature is below 1200°C; The magnetite and hortonolite with high melting points are considerably increased, and the viscosity rises accordingly. The melting and viscous properties for the slag with high content of Fe2O3 were improved by adding MgO. Desired slag splashed layer was formed with the saturated Fe2O3 and MgO slag.

Slag columns for upgrading phosphorus removal from constructed wetland effluents

The current best option to upgrade constructed wetlands (CWs) for phosphorus (P) retention, in terms of efficiency, cost and simplicity, consists in using media having a strong P affinity. The media can be used either in the planted beds or in a filtration system downstream of the beds. The use of slag filters was shown to be efficient for removing P from wastewater as it represented a slow release source of calcium and hydroxide, favouring the formation of hydroxyapatite. Our study aimed at maximising the P retention capacity of slag filters located at the outlet of CWs since electric arc furnace slag has been shown to inhibit the growth of macrophytes when used in the filtration matrix. Bench-scale columns (Vtot = 6.2 L) filled with various combinations of filter media (slag, granite, limestone) of different sizes (2–5, 5–10, 10–20 mm) were fed on-site during four months with a CW effluent (in mg/L: 30 COD, 30 TSS, 10 Pt). Results showed that the best media combination enabling the maximum o-PO4 retention (more than 80% removal without clogging) consisted in a series of a ternary mix column (slag 5–10 mm, granite 2–5 mm, limestone 5–10 mm) followed by a slag column (slag 5–10 mm). Pilot scale columns (Vtot = 300 L), filled with the best media combination, were installed at the outlet of a 28 m2 CW. These columns showed more than 75% removal efficiency during one year and were designed to be easily replaced each year.