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• Environmental Considerations for Electric Arc Furnace Recycling

Before permits were granted for battery recycling within electric arc furnace steelmaking operations, extensive trials were undertaken by the operators in collaboration with the battery industry. These trials included both processing considerations and environmental considerations. Extensive independent environmental monitoring and environmental impact assessments were undertaken at several trial locations throughout Europe.

At the first trial at Nedstaal B.V. in The Netherlands, the permitting authorities, The Provincial Executive of Zuid-Holland, applied the same requirements as for the Waste

Incineration Air Emissions Decree, the strictest environmental standard in the Netherlands. The emissions were monitored by Tauw Milieu, an independent, government approved, environmental assessment agency.

Most importantly they reported that no dioxin issues were noted with the addition of batteries into the electric arc furnace. The dioxin level was measured from the electric arc furnace with and without the addition of batteries. With the addition, the level increased by only 0.20 x 10"8 kg/charge, and this was comparable with values measured previously during standard production. The NOx level fell by 10% to 5.49 kg/charge during the same trial. They therefore concluded that the dioxin and NOx levels remained within the normal fluctuations expected of steel plants due to the heterogeneous nature of scrap. These findings have also been confirmed by trials at ASW Sheerness Steel in The United Kingdom. With additions of batteries up to 2% of charge weight, the dioxin emission levels fell below the control level, measured with no battery additions. That is not to say that battery additions reduce dioxin emissions, but confirms again that emissions remain within normal fluctuation arising from changes in scrap quality.

For the Provincial Executive of Zuid-Holland, the dioxin level was not therefore considered significant. The other determining factors for the acceptance of batteries into the electric arc furnaces of Nedstaal B.V. were the mercury and cadmium contents. In both cases, the levels measured were well below the acceptance level of the stringent standards set within the Waste Incineration Air Emissions Decree.

Trials at Nervacero, Spain, measured the metals and heavy metal content of the emissions. Three comparisons were made between loads with battery additions and controls. These were: the sum of Pb, Cr, Cu and Mn in mg/Nm3, the sum ofNi and As in mg/Nm3 and the sum of Hg and Cd in ng/Nm3. In each case the values were more than five times lower than the permit levels. Additionally the total particulate emission level did not increase and remained approximately four times lower than the permitted level.

The use of the slag product is unaffected by battery additions. The slag produced during battery recycling in the USA passes US EPA, TCLP tests. Slag produced while recycling batteries in Europe continues to be sold as construction material.

Adding batteries creates no additional health and safety issues for plant staff. The batteries are added along with the steel scrap into large charging containers. These are loaded directly into the furnace mechanically. There is no need to shred or pre-treat the batteries before addition to the furnace.

The environmental arguments for using the existing metals industry to recycle batteries rather than developing dedicated processes are strong. The industry is subjected to stringent environmental regulations, which control the emission of potential pollutants to atmosphere, water and land. Additionally the use of products and by-products are also subjected to tight regulatory control. Adding batteries to the feed streams of the metals industry, at the levels recommended, do not significantly affect the process, its environmental controls, or the markets available for the products. Indeed in many instances, adding batteries to the process enhances the by-products and will help to ensure that they are recycled, rather than landfilled, in the future.

The metals industry has a massive infrastructure with established markets for all of its products and by-products. The industry has enough capacity to recycle all of the scrap batteries produced globally many times over. Consequently the battery industry can be very selective over who they send batteries to for recycling. The companies selected by the battery industry for partnership will recycle all of their by-products that are affected by battery additions.

The steelmaking electric arc furnace produces approximately 40% of the steel required for modern living. Consequently it is a very stable industry with an environmental control system firmly established, and readily able to respond to any additional environmental controls imposed on it in the future. This is already a well-established recycling route for many other multi-metal, end-of-life consumer products. Recycling batteries within these processes does not add any additional burden to the operators because they are already used to handling varied feeds within their processes.

• Other Integrated Recycling Approaches

Within the metals industry, some small consortiums or individual companies have sought to manage the growing environmental waste problems within their industry in a responsible manner, by dedicating equipment and resources to manage waste problems in-house. As with the steelmaking route, primary batteries can also be successfully recycled within these processes. One obvious disadvantage of these processes, compared to electric arc furnace steelmaking, is availability. These processes are unique in their approach and often small scale, compared to the very large electric arc furnaces producing steel. Although the primary focus of some of these operations remains almost exclusively in-house waste, other companies have embraced the opportunity offered by recycling wastes for other industries including batteries.

DK Recycling und Roheisen GmbH, of Duisburg, Germany, operate a blast furnace to produce foundry pig iron from iron containing dusts and sludges. This process is unique in that unlike conventional blast furnace operations, DK are able to cope with significant amounts of zinc. Zinc typically forms accretions on the furnace wall leading to clogging and increased furnace wear. Through a specialist knowledge in the handling of zinc in the blast furnace and careful attention to certain operational parameters, DK Recycling are able to take wastes where the zinc burden is up to 300 times higher than conventional blast furnaces. The sludge from the gas cleaning plant occurs as a pure zinc concentrate, which is sold to the zinc industry.

Today DK Recycling und Roheisen GmbH recycle mercury free manufacturing scrap from primary battery manufacturing facilities and are undergoing further trials to extend this service to collected post consumer batteries.

Valdi is a subsidiary of a foundry company, AFE Metal, and a special industrial waste handler, Tredi. This company has grown out of the environmental branch of Feursmetal, one of the foundry sites within the AFE portfolio.

In 1990, AFE Metal was faced with a scheduled closure of the facility handling the waste from the Feurs foundry. This gave the company four years in which to develop alternatives to their waste handling problem. They embarked upon a research and development project which included reducing raw material consumption, reorganising wastes within the plant and developing in-house recycling processes. The project was so successful that in 1995, AFE Metal decided to extend their know-how to other foundries and similar wastes. In 1997, the decision was taken to diversify and set up a specific company, Valdi, to operate the recycling processes.

Today Valdi recycle various metal or mineral containing by-products into ferro-alloys within a dedicated 10,000 tonne per year facility in the Feurs foundry. Primary batteries have been included as one of the recycleables within the facility since 1994.

Batteries are continually fed into a 3.5 MVA electric arc furnace via an automatic feeding system during the melting process. Unlike the electric arc furnace steelmaking route, which can only facilitate batteries up to approximately 3% of the feed, the Valdi process loads batteries into a furnace which is void of steel except for a small heel, which is maintained to begin the melting process Only lime and reductant are added to the furnace together with the batteries to reduce manganese dioxide and neutralise the gases produced.

The iron, manganese and zinc contained within the batteries are all reduced within the bath. The iron and manganese are diluted with the liquid heel and the zinc is vaporised, where it is re-oxidised on contact with the oxygen in the air, in just the same way as in conventional steelmaking processes.

The manganese, iron and steel combine to form a ferromanganese, which is less pure than traditionally produced ferromanganese, but still able to be used in several applications including the production of high resistance castings such as teeth for mechanical diggers. The zinc oxide is captured within a bag filter plant and sold to a zinc reclaimer.

The electric arc furnace has been specially adapted in order to cope with the high volume of zinc oxide evolved and to control fugitive emissions. An additional extraction port has been added to the roof of the furnace to help to extract the zinc oxide and the entire furnace is contained within a 'dog-house', an enclosure designed to restrict environmental emissions within the working space (Figure 5). The 'doghouse' is also fitted with a forced ventilation fan, which improves the extraction process. These additional environmental controls, together with an activated carbon injection system and specially designed bag filters, allow Valdi to process batteries containing up to 500 parts per million of mercury without any adverse effects on the local environment. The ability to process batteries containing some added mercury makes Valdi unique among the integrated metals industry processing routes.

The electric arc furnace dust produced by Valdi is contaminated to some extent by the mercury. This means that the dust cannot be sent for processing within the pyrometallurgical zinc industry. The dust is therefore sent for processing via a hydrometallurgical route, however this is a far more expensive option. The slag produced from the process is recycled as an aggregate in much the same way as the steelmaking electric arc furnace slag.

The industrialisation of these processes has won the company the EUREKA prize of Lillehammer, for outstanding environmental achievement in 1999. Valdi do not intend to stop here. The current capacity of the Valdi process is approximately 5,000 tonnes

Figure 5. Valdi Furnace contained within a 'Dog-House'

for used batteries. They have ambitious plans to extend the recycling of batteries to a second facility at Le Palais, also in France.

Valdi see that one of the biggest problems of recycling batteries within their furnaces is the water content. With batteries containing up to 10% moisture, a significant proportion of the energy required by the furnace is used to dry the batteries. This is not an efficient use of the energy. Furthermore when processing large quantities of batteries in this way, there is also a risk associated with rapid expansion of gases during the drying process. Consequently Valdi intend to install an upfront multiple hearth furnace in their new facility to produce direct reduced iron, D.R.I., from the batteries and then melt this within an electric arc furnace to produce ferromanganese.

In addition to improving the melting efficiency of the furnace, this step also brings additional advantages. These include better separation of zinc from pollutants within the gas phase, lowering dust volume, and increasing the zinc concentration. With the inclusion of this new facility, Valdi's capacity will increase to approximately 15,000 tonnes of batteries per year.

Within the zinc industry Waelz kilns are used to concentrate the zinc oxide within the electric arc furnace dust coming from the steel industry. The Waelz kiln is a large rotating furnace operating under oxygenating conditions at approximately 1300 degrees centigrade. Under these conditions the zinc content of the electrical arc furnace dust is increased from between 20 to 25% by weight, to 55 to 60% by weight. This upgraded dust is then either converted into zinc metal by smelting or electrolysis, or used in the rubber or animal feed industry. The only by-product of the Waelz kiln is a slag, which is suitable for civil engineering applications or as an additive in the cement industry.

The Waelz kiln operation is subjected to the same stringent environmental standards as the EAF steelmaking process. Trials have been undertaken in Europe and the USA to determine whether these same standards are met when operating with mercury free primary batteries as part of the feed.

Independent environmental assessments have shown that there is no increase in the emission of solids to the atmosphere and these are well below statutory requirements. With the addition of batteries, the total particulate emission level, measured during trials in Spain, did not increase and remained 30% below the permitted level. Furthermore, treating batteries does not increase the heavy metal content of the emissions. As for the electric arc furnaces, the heavy metal content of emissions are measured as the sum of Pb, Cr, Cu and Mn in mg/Nm3. With the addition of batteries at up to 15% of the charge, no increase in the normal operating levels was measured. In both cases the values were more than 10 times lower than the permit levels.

As expected, the manganese content of the slag increased, but this was not deleterious and the leachability of the slag did not increase. A waste is considered toxic when a leachate shows a value for the ecotoxicity standard, EC50, of greater than, or equal to, 3,000 mg/1. In all cases, the EC50 value was less than 200 mg/1.

Conclusions

Europe is, and will remain, at the leading edge of battery waste management. The European Union is keen to see the expansion of battery collection and recycling and continues to propose new legislation in an attempt to harmonise efforts across Europe. It would appear however that because the Member States remain free to be able to impose economic instruments or deposits at will, and the Directive fails to define individual responsibility, it is unlikely to achieve this aim.

Many innovative and diverse processes have been developed over a number of years to tackle the growing problem of battery waste. Some have been proposed simply to resolve issues on a national level, while others are clearly looking to the future and much larger volumes. As with any competitive market, the processes which will prove sustainable in the long-term will be those which are able to adapt to changes in battery compositions and remain economically viable. The elimination of mercury from alkaline and zinc carbon batteries, for example, increases the opportunities for recycling and reduces the need for dedicated facilities concentrating on the control of hazardous materials.

Integrated waste management schemes, rather than a dedicated schemes, would appear to be an alternative way forward for many used consumer products. In light of the findings in the UK Department of Trade and Industry report, collecting similar waste streams together, the comingled approach used for small household chemical wastes in the Netherlands for example, would appear to have significant environmental benefits over dedicated battery collection schemes operated elsewhere. Alkaline and zinc carbon batteries would appear to be ideal candidates for such an approach, given that they can now be recycled in the metals industry together with other metal bearing waste. Not only will this provide the most environmentally beneficial solution, but it would also provide the most economically viable solution.

References

1. Assessing the Environmental Effects ofDisposal Alternatives for Household Batteries, Institute for Risk Research, University of Waterloo, Ontario, Feb. 1992

2. Behaviour of Mercury in Used Dry Batteries Buried in Landfill Sites, Urban City Cleaning, Vol. 49, No. 212, June 1996.

3. Analysis of the Environmental Impact and Financial Costs of a Possible New European Directive on Batteries, Environmental Resources Management, November 2000.

Used Battery Collection and Recycling G. Pistoia, J.-P. Wiaux and S.P. Wolsky (Editors) © 2001 Elsevier Science B.V. All rights reserved.

LEAD/ACID BATTERIES

A. Pescetelli, E. Paolucci and A. Tine

Texeco s.r.l., Via Pomarico 58, 00178 Rome, Italy*

Introduction

The world is getting increasingly aware of the need to limit the consumption of nonrenewable resources and the production of waste. This requirement is accomplished by taking advantage of recycling technologies and re-using the materials at the end of their useful life. In this framework, recycling of the largely used lead/acid batteries, containing metals, chemical compounds and other harmful substances, is a correct way to put into effect these concepts.

Collecting and recycling these batteries with high efficiencies, currently underway in all developed countries, allows the drastic limitation of environmental pollution while contributing to the availability of significant lead volumes to meet the industrial demand. At the same time, recovering lead from batteries significantly reduces the need to depend on its primary resources, i.e. lead ores, thus delaying their depletion.

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