Today production industry has increasing incentives to be resource efficient and sustainable. Many residual material streams from production processes are therefore recycled internally; however, some streams might be of better use in another industry. In this study, factors seen as encouraging and/or barriers in the work towards an industrial symbiosis with residual materials, between two or more industries, were identified. The factors were divided into five categories: physical/technical, regulatory, business, motivation and society, on three organisational levels. Based on the key factors, the time aspect for establishing an industrial symbiosis was studied and criteria that need to be met in order to carry on with a business idea for a residual material were divided into three work phases. The study shows that an industrial symbiosis based on residual materials on many levels differs from a business with main products, for example when it comes to laws and policies. With residual materials it is also extra important to have good understanding of the material properties and the customer’s material requirements. It was concluded that the establishment of industrial symbioses would be facilitated if all materials had the same conditions regardless of origin provided that the final product gets the same properties.

At the steel plant of Höganäs Sweden AB, different steel grades were produced using an Electric Arc Furnaces (EAF). The slag tapped by the EAF often disintegrated during cooling. Slag fines from the disintegration are difficult to handle and to use as materials in construction. The plant tests of EAF slag treatments using stabilizer MCP-F of high P2O5 content were thus conducted, with 1st and 2nd campaign adding 10 and 20 kg MCP-F/ton slag, respectively. The MCP-F addition in slag pots and other test operations were carried out smoothly, without impacting the EAF steel production. Rates P2O5 recovery in the EAF slag were lower in some test heats. Studies may thus be carried out in future to increase the P2O5 recovery from MCP-F, hence, achieving a higher efficiency of stabilization treatments for the slag from the EAF plant.

Steel production is a material and energy intensive industry which, in addition to steel products, generates residual materials such as metallurgical slag, dust and sludge. These residual materials are recycled and used to a great extent as well in-house as for external purposes. Even so, some materials are currently landfilled due to difficulties in finding use or recycling possibilities. This applies, for example, to zinc-containing sludge and dust from ore-based steel production and certain iron-rich, lime and carbon-containing materials from scrap-based steel production. A case study has been performed with the aim to develop a methodology for evaluating industrial symbiosis possibilities in regard to increased material efficiency in steel production systems. The methodology is based on system analysis of steel production routes in combination with economical assessment of hypothetical business concepts by using residual materials from one industry as secondary raw materials in another. The paper presents case study results and indicates how this methodology could be applied to maximise the residual materials utilisation. By the methodology discussed and with a circular-economic perspective, it is shown that high economic potential for one material could be used to increase the utilisation of other materials with lower economic potential.

Laboratory treatments of a plant EAF slag sample 71686 were conducted using stabilizers containing P2O5and air granulation. The results show that it is necessary to add the stabilizers to increase contents of P2O5from 0.39% to 0.7% for the slag stabilization. By a fast air cooling, most of the granules from the granulation are spherical, with a low internal porosity and dense structure. Content of Fe2O3in the granules increased from 7.92% to 18.4% and FeO decreased from 14.3% to 7.8%, due to an oxidation during the slag granulation. Contents of metal elements, As, Cd, Cr, Mo, Pb, Ni and Zn, in the leachates from the treated slag samples were lower than the limit values for leaching from inert wastes pursuant to Directive 1999/31/EC. The slag samples after the treatments may then be regarded as environmentally friendly to use in construction.