Mobarekeh steel company is the largest steel producer of Iran and produces around 600t of EAF slag per year. The slag produced in this plant normally cools in the air, but the mineralogical composition can be adjusted by appropriate cooling methods in order to fulfill the mineralogical requirements of cement production. In this work various types of cooling methods were adopted in order to achieve a slag product possessing very uniform and spherical glass granules suitable for use in Portland cement.

Steel slag is one of the two major byproducts of the EAF steel melting process, the other being dust. During melting, oxidation of phosphorus, silicon, manganese, carbon, and other materials occurs and a slag containing some of these oxidation products forms on top of the molten metal. Once cooled the molten slag solidifies to form glassy and/or crystalline minerals depending on the specific rate and method of cooling. Molten slag is collected in iron slag pots during the melting of raw materials in the electric arc furnace. The slag is then cooled by pouring it into the designated area.

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During recent years the cement industry has suffered significant increases in operating costs driven in particular by spiralling energy prices plus pressure from environmental lobbies to reduce dependence on fossil fuels and reduce CO₂ emissions overall. Considering the production of a ton of conventional Portland cement generates almost a ton of CO₂ and in terms of total greenhouse gas emissions for all industries worldwide places cement second only to power in the scale of global polluters.

These factors have generated an increased awareness of alternative fuel possibilities for kiln firing and substitute raw material options for cement production, reflecting also an increased demand for blended cements particularly including ground granulated blast furnace slag (GGBFS); for every ton of GGBFS included in the final blended cement the total CO₂ production is reduced by around 1t...

Sterlite Industries (India) Ltd., Tuticorin, India produces 400,000t/year of copper. During the process, around 800,000t of copper slag is generated within a year. The joint study between Sterlite Industries (I) Ltd. and NCCBM, New Delhi, India aims to utilise copper slag as raw mix component in Ordinary Portland Cement (OPC) and as a blending material for Portland Slag Cement (PSC).

Introduction

Sterlite Industries (India) Ltd., Tuticorin, Tamil Nadu produces 400,000t/year of copper and during the process, around 800,000t of copper slag is generated in a year. The copper is being produced from a copper concentrate containing around 30 - 35% of copper, iron and sulphur each along with around 12% of silica and 5% of calcium. While producing copper the anode, a slag with rich iron and moderate silica content is also generated.

The chemical analysis of the slag indicated that its matrix is compatible with the cement system and can be used in the manufacture of OPC. The copper slag has been found to contain high iron oxide and may be used as a source of iron in the manufacture of OPC. However, the presence of high iron in the slag hinders its bulk utilisation. The effect of copper present in the copper slag is invisible in the formation of clinker as the quantity of copper slag used in the raw mix for OPC may not be enough to percolate the effect of copper on the formation of OPC clinker.

Slags are by- or co-products of the iron and steel making process. BF (blast furnace) slag is generated in iron production and EAF (Electric Arc Furnace) slag is generated by steel production. The same is with Basic Oxygen Furnace (BOF) slag. Processing of EAF using traditional methods involves crushing and grinding. However, the new technology of atomising molten slag is an innovative process that produces high-specification products with multiple uses.

Slag Atomising Technology (SAT) is invented, patented and commercialised by Ecomaister Co., Ltd of Korea. Many plants are successfully in operation and many are under construction, 5-6 projects under negotiation. SAT is a strategic approach to overcome the environmental problems of electric arc furnace slag. A modern technology and operating system, the unique JIT technological management operation of hazardous materials. JIT means 'Just In Time' operation, since the molten waste slag is immediately converted to environmental-friendly PS balls as soon as it is dumped into the SAT system.

A growing Japanese steel production and a corresponding increase in slag output has forced Japan to develop new alternative ways of using slag Global Slag Magazine gives an overview of several environmentally friendly slag applications.

The growth of steel production in Japan over the last half century has been accompanied by a corresponding increase in slag output from the nation's blast furnaces and electric arc furnaces. Disposing of the growing volume of slag has become a major task for the steel industry which has been forced to develop inventive uses for slag to try and solve the problem.

New uses for Japanese slag

Leading Japanese steel makers continue to invest significant resources in developing new uses for slag that are both beneficial as well as environmentally friendly. The steel industry's difficulties disposing of slag are recognised by the government which requires regional governments to buy processed slag and other recycled waste products to support Japan's growing recycling programme.

In 2004 Japan produced 34.7Mt of slag as a bi-product of steel production. Blast furnace slag accounted for 91% of the total tonnage while the remaining 9% was electric arc furnace slag. Five Japanese steel makers operate blast furnaces. Nippon Steel produced 12.6Mt of blast furnace slag, accounting for 36% of total domestic slag production, followed by JFE Steel which produced 11.9Mt of blast furnace slag, accounting for 34% of Japan's total slag output. Three other steel producers operating blast furnaces – Sumitomo Metal Industry, Kobe Steel and Nisshin Steel produced a further 26% of slag output combined, while more than 20 steel companies operating electric arc furnaces account for the other 9% share of Japan's slag production.