Residual products and waste
The production of iron and steel products also gives rise to a range of residual material.
Each year about two million tonnes of this material is produced by Swedish steel and iron industry.
This consists of principally industry-specific materials (e.g. slag and mill scale), that is used as follows:
- one third is used externally, e.g. is sold as products
- one third is reused in the production process,
- one third is disposed of in landfill
In addition, the production process also results in steel or iron scrap. This scrap steel is reused as iron raw material in the production process.
The collective term we use for this is residual products or residual material. This term has no legal implications but is merely one way of summarising everything that is left over from the production of steel (more detailed definitions and examples below). Below there is a presentation of the industry’s position on by-products, materials for internal circulation, recycling and waste.
Landfill and waste
Certain materials can be put to productive purpose but for others there is no suitable use presently available. They are therefore waste and can only be disposed of in landfill. The wastes that are sent to landfill include steel slag, dust from gas purification and sludge (hydroxide sludge and mill scale sludge).
Landfill means the deposit of waste for disposal onto or into land. In many cases the steel industry has its own landfills. Landfills have long been regulated from an environmental viewpoint, in particular through the EU’s Landfill Directive. The directive imposes a number of technical requirements to protect soil and water from pollution including as to the liners to be used and the collection and management of leachate. The steel industry has been working intensively on this issue for several years and most companies have now had their after-care/conditioning plans approved so that their landfills comply.
Example of investment for recovery
Research and development are in progress to find an application for the residual material disposed of in landfills. In the autumn of 2009 Outokumpu took the decision to invest SEK 280 million in a treatment facility for cutting the level of nitrates in the effluent by two thirds. It will be possible to recover up to 95 % of the pickling acids used in the production process which dramatically reduces the amount of acid used in the production process. In addition, metals will be separated and returned to production which will reduce the quantity of metal hydroxide sludge and so the quantity of waste going to landfill.
Research into increased use of slag
The research now being carried out is aimed at enabling more slags to be used productively such as filling material or turned to account in some way. In the joint Nordic research carried out within Jernkontoret’s technical areas, more than SEK 80 million is being invested over a six-year period in steel industry slags. The research projects form part of the major research programmes Steel Eco-Cycle (Mistra), Steel Research Programme (VINNOVA) and PRISMA (Centre for Process Integration in Steelmaking). A series of different research institutes are involved in these projects as well as the majority of Jernkontoret’s member companies. In one research project, it has been found that a mix of electric arc furnace slag and ladle slag work effectively as final covering of landfills.
Example: Project for final covering of municipal landfill
Holkesmossen is a municipal landfill in Hagfors municipality for which final covering is planned. In 2003 a research project was started by Uddeholm Tooling together with Hagfors municipality and Luleå Technical University (LTU).
A 0.5 hectare [5,000 sq. m.] large area of the landfill (total 12 hectares) underwent final covering with slag in the drainage stratum with ladle furnace slag in the sealing stratum. A study of the project shows that slag compounds from Uddeholm Tooling can be utilised and in June 2009 an agreement was signed with Hagfors municipality which therewith does not need to utilise raw materials for the final covering.
A final covering comprises several layers (starting closest to the landfill):
- A levelling course of at least 0.5 m. For this purpose slag compounds of appropriate particle size may be used.
- A sealing stratum of at least 0.7 m. To this end a concrete-like material is created where finely ground ladle furnace slag compounds constitute the cement and crushed electric arc furnace slag constitutes the filler - a mixture that becomes as hard as concrete and whose permeability to water is practically zero and from which leaching does not occur in measurable amounts.
- A drainage layer of at least 0.3 m. For this purpose, coarse crushed (approx. 50 mm) slag compounds from the electric arc furnace are employed.
- Moraine/plant establishment in such quantity that the total sealing stratum is at least 4 m.
Utilisation of residual products
The Swedish steel industry wishes to enhance resource management through finding economically viable applications for the materials which arise in connection with steel manufacturing. There are many activities underway at companies and within the joint research projects to improve the exploitation of resources, product and process development .
There are many different types of slag which arise from each steelworks and from the different metallurgical process stages in steel production. Each slag has its own unique properties that depend inter alia on its mineralogical composition. A total of just over 1.3 million tonnes of slag per year is produced in Sweden. About half of this total is currently used in different applications either within the steelworks or outside the industry.
Examples of areas of application are road construction and the building industry, in agriculture, ferrites as well as raw materials in the metallurgical and chemical industries.
Blast furnace slag from SSAB in Oxelösund finds its way into KRAV-marked soil improvement agents, type approved cement additive, filter material for water purification, material for riding tracks as well as base courses in thin covered but solid roads.
Read more:www.merox.se
LD-slag from SSAB in Luleå and Oxelösund is reused as a slag-forming constituent in blast furnaces. The slag works effectively as a slag former and delivers good sulphur purification. The slag also contains iron and manganese that can be made use of in the blast furnace process. Moreover, about 150,000 tonnes of virgin limestone is thereby saved annually.
Mill scale is formed e.g. at the Erasteel plant in Söderfors which manufactures high-alloy special steel. The hard blue-black scales contain valuable alloy materials such as wolfram, vanadium and molybdenum. Formerly the mill scales were just piled on a heap. With a new method and increased metal prices on the world market recycling has now become profitable. In Söderfors and at the sister company in Långshyttan there is mill scale sufficient for a couple of years’ production. The recycled metal compound is cast into ingots that are then used in the production at Erasteel’s steel plants in France.
Gas purification dust from manufacturing of stainless steel includes chromium, nickel and iron that are recycled at Befesa Scandust AB in Landskrona. Dust with high zinc content is recycled at Boliden Mineral in Rönnskär.
Hydroxide sludge. Outokumpu’s Swedish facilities previously sent to landfill all hydroxide sludge generated by pickling acid neutralisation. Now the sludge is dried after which the product Hydrofluss® is manufactured.
From the viewpoint of process metallurgy, the most interesting component in the hydroxide sludge is Calcium Fluoride (CaF2), a so-called flux that is used as an additive to reduce the viscosity of the slag. Hydroflyss contains approx. 50% CaF2 and enables part of the steel plant’s consumption of the mineral fluorspar (virgin mineral, transported from China) to be replaced. Trials undertaken indicate that the ladles support a higher charge where Hydrofluss is used instead of fluorspar. Another advantage is that Hydrofluss contains lime and oxidised metals that can be fed back into the steel in the process.
Areas remaining for development
There are several reasons why a larger share of the produced slags is not utilised at present, of which the following can be mentioned:
- Certain slags have properties that mean that they are not suitable for construction purposes (e.g. they are unstable and disintegrate into powder in the air or leach certain metals).
- There is inadequate understanding of the composition of the slags and of the potential to modifying unstable slags to become stable material.
- The demands of the Swedish regulatory authorities in respect of slag for construction engineering focus more on the content of e.g. metals than what actually reaches the recipient and affects the environment.
Slag from steel production is used to a greater extent in other countries both within the EU and internationally.
Legislative position
By December 2010 Sweden will have implemented the Waste Framework Directive in Swedish legislation. This modernises and clarifies the rules on waste and as such is welcomed by the business sector. The former framework directive was made from 1975 (substantially revised in 1991). With a clear-cut demarcation between product and waste there is an increased possibility of exploiting the potential that lies in the steel industry’s residual products and enable them to be marketed as such in appropriate cases.
For those slags that the industry adjudges to be by-products, a full registration within the terms of REACH has been initiated. This will lead to a risk assessment being made of each material for different areas of application. The REACH legislation does not cover waste but what is defined as waste is determined at the national level. Since REACH is a Regulation it will in the longer term have a normative status in the interpretation of waste in the EU member states.
Read more: Chemicals (REACH)
Basic Standpoints
- It is especially important that materials that should properly be considered by-products are excluded from the waste regulation and, where that is not possible, that clear criteria should be laid down for when waste ceases being waste.
- Adoption of End of Waste (EOW) criteria under the Directive should ensure consistent interpretation across Europe and should be directly applied in Sweden.
- Work on developing criteria for when waste ceases being waste should focus on setting environmental and health criteria and not be more extensive than where the material remains a waste.
- Facilitate the use of residual materials for construction work. Where a material is REACH-registered it is a product and meets the REACH demands relating to environmental and health studies. It shall not therefore be covered by waste regulation. The Swedish Environmental Protection Agency’s draft ‘Handbook for recycling of waste in construction work’ [Handbok för återvinning av avfall i anläggningsarbete] that has been circulated for comment should be replaced or supplemented with this type of guidance, combined with the future criteria work within the EOW Directive.
Definitions and examples
Production residue: A collective term for by-products, material for internal circulation, recycling and waste in this presentation is residual products or residual material. This term is merely one way of summarising everything that emerges over and above the production of steel.
Waste: substance or object that the holder discards of or intends to discard of or is liable to discard of. '
By-product: A substance or object that arises through a production process the main object of which is not its production may only be regarded as a by-product instead of waste if the following conditions are met:
- It shall be guaranteed that the substance or object will continue to be used.
- The substance or object shall be able to be used directly without any further processing other than normal industrial usage.
- The substance or object is produced as an integral part of a production process.
- Continued use shall be lawful, i.e. the substance or object shall fulfil all relevant product, environmental and health protection standards for the specific use and not lead to generally negative consequences for the environment or for human health.
