Technological improvements in automotive battery recycling

Resources, Conservation and Recycling 52 (2007) 368–380

Technological improvements inautomotive battery recycling

M.A. Kreusch a,∗, M.J.J.S. Ponte b, H.A. Ponte c,N.M.S. Kaminari a, C.E.B. Marino c, V. Mymrin a

a Federal University of Parana, Laboratory of Environmental Technology (LTA),PO Box 19011, Zip-Code 81531-990 Curitiba, PR, Brazil

b Federal University of Parana, Department of Mechanical Engineering,PO Box 19011, Zip-Code 81531-990 Curitiba, PR, Brazil

c Federal University of Parana, Department of Chemical Engineering,PO Box 19011, Zip-Code 81531-990, Curitiba, PR, Brazil

Received 31 October 2005; received in revised form 13 April 2007; accepted 9 May 2007Available online 3 July 2007

Abstract

Recycling of automotive batteries for the recovery of secondary lead is extremely important inBrazil, for the country does not possess large reserves of this metal. Lead is one of the most widelyused metals in the world, but it is highly toxic, posing risks for humans and for the environmentif not utilized or treated adequately. Industrial waste containing lead in Brazil are classified by theBrazilian Residue Code (NBR—10004:2004) as hazardous. The lead recycling process employedby the recycling industry in Brazil is the pyrometallurgical process in a rotary furnace. This processconsists of four stages: (1) grinding of the battery to separate plastic, electrolyte and lead plates;(2) lead reduction in a rotary furnace; (3) separation of metallic lead from slag; and (4) refiningof recycled lead. The purpose of this work is to propose process improvements aimed primarily atincreasing production output by reducing the loss of lead in slag and particulates, thereby providinga healthier work environment in line with Brazilian environmental and labor laws.© 2007 Elsevier B.V. All rights reserved.

Keywords: Lead recycling; Environmental laws; Automotive batteries; Lead slag

∗ Corresponding author. Tel.: +55 41 33613424; fax: +55 41 33613197.E-mail address: [email protected] (M.A. Kreusch).

0921-3449/$ – see front matter © 2007 Elsevier B.V. All rights reserved.doi:10.1016/j.resconrec.2007.05.004

mailto:[email protected]

dx.doi.org/10.1016/j.resconrec.2007.05.004

M.A. Kreusch et al. / Resources, Conservation and Recycling 52 (2007) 368–380 369

1. Introduction

Lead recycling in Brazil is a crucial activity in view of the country’s minor lead orereserves, which have not been exploited since 1995, but whose lead content is low. Bothcommercially and industrially, this metal is highly important. Lead production in Braziltoday consists of secondary lead obtained through recycling, and appears in a very small pro-portion of about 0.63% in worldwide production. The demand for lead is supplied throughimports of primary lead from countries such as Peru, China and Venezuela (DNPM, 2001).Although the environmental problems associated with lead are critical at an environmen-tal level, the consumption of this metal shows a constant upward trend, since it is not yeteconomically feasible to substitute the lead used in a variety of applications, especiallyin the batteries, for any other metal (Jost, 2001). Lead–acid batteries are among the mostfrequently recycled products in the US, with a reported collection and recovery rate of 99%(Higgins et al., 2007). In 1998, 63% of the lead used in the production of US goods (1.12million metric tonnes) was secondary (recycled) lead (Higgins et al., 2007). The annual pro-duction of automotive batteries in Brazil is approximately 15 million units (Ferracin et al.,2002), from which ca. 150,000 tonnes of lead can be recovered. With the new Brazilian gov-ernment regulations named Conselho Nacional de Meio Ambiente (CONAMA) Resolutionnumber 257/99, for collection and recycling of exhausted batteries, most of the producersof lead–acid batteries established the goal of increasing the use of lead yielded from therecycling of practically 100% of these batteries. Nowadays, lead recovery from exhaustedbatteries is carried out by the pyrometallurgical route, which may cause environmentalproblems like the emission of considerable amounts of dust containing lead particulate andsulphur oxides into the atmosphere (Valdez, 1997).

Lead is the world’s most commonly recycled metal on an industrial scale, with about80% of all the lead produced worldwide applied in the fabrication of automotive batteries.More than 95% of the batteries used in the US and Europe are recycled. Fig. 1 compares therefining of primary lead with the production of secondary lead, showing the growth of lead

Fig. 1. Comparison of annual lead production by mining (primary lead) and by recycling (secondary lead)(1000 tonnes).

370 M.A. Kreusch et al. / Resources, Conservation and Recycling 52 (2007) 368–380

recycling from 1980 to 1998, and an estimate of this growth from 1998 to 2006 (Winckeland Rice, 1998).

1.1. Worldwide lead production and consumption

According to estimates by the International Lead Zinc Study Group—ILZSG (2004), theworldwide production of primary and secondary metallic lead, i.e., the mined mineral andthe mineral obtained by recovery of scrap metal, respectively, reached 6.7 million tonnesin 2003, with Asia and America being the largest producers (ILZSG, 2004).

Brazil’s apparent consumption of lead in 1999 reached a total of 94,400 tonnes (DNPM,2001), while worldwide consumption in 2003 amounted to almost the entire production ofthat year, the main consumers being the United States, Asia and Europe (ILZSG, 2004).

1.2. Principal uses of lead

Lead was one of the first metals worked by humans since 3500 BC (Lund, 1971). Leadis present in a variety of alloys and its composites are prepared and used on a large scale byindustry (ATSDR, 2004; Parmeggiani, 1983). In addition, by means of these alloys, thesematerials are used for the production of batteries, pigments, roll extrusion, ammunition,cables, gasoline additives, and others (U.S.EPA, 1998).

The use of tetraethyl lead (additive) has been banned in Brazil since 1978, and has beenreplaced with ethanol. Some countries still used this additive in gasoline, which is found inconsiderable quantities in the biosphere (Winter, 2004).

1.3. Lead toxicity

Although both natural and anthropogenic processes are responsible for the releaseof lead into the environment, anthropogenic contamination is predominant (ATSDR,2004). A large amount of lead where the produced is present in the form ofenvironmental contamination (Bellinger and Schwartz, 1997). The impact caused bymining and foundry activities can persist for a long time in the environment (WHO,2004a,b).

A concentration of lead of less than 10 �g/dl is considered acceptable by the WHO (WorldHealth Organization), the CDC (Center for Disease Control) and the ACGIH (AmericanConference of Governmental Industrial Hygienists). The ACGIH also recommends thislimit for pregnant women (FAO/OMS, 1994).

Table 1 lists the biological parameters that limit the exposure of workers to lead inthe work environment. These parameters indicate the need for alterations in the processand in the environment, and/or removal of the worker from areas exposed to this heavymetal (Kreusch, 2005). Acceptable levels of lead are regulated for food and water throughDirective # 16 of the National Environmental Commission (CONAMA).

The lead recycling process in Brazil has grown steadily over the years. In addition topreserving the environment, the recycling of this element ensures its increased life cycle.Recycled lead maintains the same physicochemical properties as primary lead and hasbecome the raw material of this metal (Jolly and Rhin, 1994). There are basically three


Table 1Occupational biological parameters

Biological parameters Exposition levels

I II III IV

Lead in the blood(�g/100 ml)

≤40 40–60 60–70 >70

Lead in piss (�g/l) ≤70 70–120 120–400 >400Individual measures Annual control Quarterly control Removal of the

exposition sourceand examination forthe displayed ones

Removal of thework

Ambient measures None Control of thework environment

Necessary to improve thetechnological conditions of the workenvironment

Source: FAO/OMS (1994); Kreusch (2005).

methods for battery recycling: separation of components through unity operations of miningtreatment, pyrometallurgy and hydrometallurgy (Jolly and Rhin, 1994).

The pyrometallurgical process is composed of four stages: (1) grinding of the batteryto separate plastic, electrolyte and lead plates; (2) lead reduction in rotary furnace; (3)separation of metallic lead from slag; (4) refining of recycled lead.

According to Jost (2001), the main sources of environmental impact caused in the stagesof the recycling process are:

1. Grinding of the battery to separate plastic, electrolyte and lead plates:• Dust contaminated with lead and acid electrolyte.• Particulate lead.• Contaminated waste.

2. Lead reduction in a rotary furnace:• Lead-contaminated scraps.• Lead-contaminated dust (from filters).• Emission of SO2.• Emission of chlorinated compounds.• Production of slag.

3. Separation of metallic lead from slag and refining:• Emission of lead vapors.• Emission of SO2.• Production and removal of a fine, dry dust with a high percentage (%) of lead and

other metals.• Release of chlorine gas (Cl2).

The pyrometallurgical process for recovering lead involves redox reactions at high temper-atures (1000 ◦C).

Lead metal scrap is composed of metallic lead, oxides and lead sulphate. The reduction ofmetallic scrap into metallic lead requires the addition of carbon and iron as reducing agents,with all the components subjected to high temperatures (Machado, 2002). Two reactions


occur simultaneously:

PbO + C ↔ Pb0 + CO (1)

PbO2 + 2CO ↔ Pb0 + 2CO2 (2)

The lead oxides (PbO and PbO2) react with carbon (C—reducing agent), resulting in theformation of metallic lead (Pb0) and carbon gases.

In a third reaction, lead sulphate (PbSO4) reacts with metallic iron (Fe0—reducing agent),forming metallic lead (Pb0) and iron sulphate (FeSO4), according to the following chemicalreaction:

PbSO4 + Fe0 ↔ Pb0 + FeSO4 (3)

The generated residues are proceeding mainly from incomplete reactions that occur insidethe furnace due to the variation of temperature of about 650–1000 ◦C as is presented inEqs. (1–3), insufficiency of the reducing agent (iron or carbon) and inadequate homog-enization of raw materials. The process of reduction of the lead consists in isolating themetallic lead of the mixture of some gotten substances of the scrap: metallic lead, leadoxide (PbO), lead sulphate (PbSO4) and other metals, as for example Ca, Cu, Ag, Sb, As,and Sn.

1.4. Brazil’s environmental laws

Brazil’s environmental laws are very strict and highly detailed. In addition to municipal,state and federal laws, there are decrees, resolutions, government directives and codes. Themain code that deals with hazardous solid waste is the NBR 10004:2004 standard, whichfollows the standard of the Brazilian Association of Technical Standards (ABNT) (ABNT,2004).

In the literature it is reported that on average about 300–350 kg of slag for each ton ofproduced metallic lead are generated, and about 5% of this slag is lead composites (Kreusch,2005).

2. Materials and methods

2.1. Materials

The recycling of automotive batteries generates residues whose chemical compositioncontains a certain percentage of lead, usually in the form of oxides and sulphates. Thepurpose of this work is to propose process improvements aimed primarily at increasingproduction output by reducing the loss of lead in slag and particulates. Samples of slag andparticulates were collected to determine the materials’ chemical composition, as well asoperational data used in the battery recycling process, such as:

• What raw materials are used to obtain secondary lead;• Chemical reactions of the process.


Fig. 2. Battery recycling flowchart.

2.1.1. Flowchart of the automotive battery recycling processFig. 2 shows a flowchart of the automotive battery recycling process.The flowchart indicates several points in the process where the operation can be improved,

avoiding waste and loss of lead in slag and particulates.

2.2. Methods

2.2.1. Stages of the battery recycling processBattery recycling consists of various stages, as indicated in the flowchart (Fig. 2), each

with its own objectives, i.e., selection of recyclable battery material, separation of lead fromother metal and contaminants to minimize the emission of solid and atmospheric pollutants.The raw materials used in the battery recycling process are battery plates (±4500 kg);iron swarf (650 kg); charcoal (300 kg); sand (200 kg); baghouse particulates (10 kg). Thepyrometallurgical process in a lead recycling furnace should operate with the followingchemical reactions:

PbSO4 + 2C ↔ PbS + 2CO2 (4)

PbS + Fe0 ↔ Pb0 + FeS (5)

Eqs. (4) and (5) demonstrate that initially the lead presents in the sulphate form and after ofthe first stage of the reaction that occurs in the presence of the reducing agent (charcoal) in atemperature of about 650 ◦C. The lead is present in the form of sulphide where it is reducedin one second stage of the reaction (iron swarf) in a temperature of about 1000 ◦C. The idealtemperature so that the reaction occurs adequately and almost all the PbS is reduced to themetallic Pb0 around 900 ◦C.


2.2.2. Experimental methodologyTechnical visits were made to the battery recycling plant, where the following informa-

tion was initially collected: operational data on the process, particulate samples, and slagsamples.

The company records its operational data on a standard sheet containing the followinginformation: total execution time of the process, and the quantity, in kilograms, of batteryplate, iron swarf, charcoal, sand, and lead ingots utilized. The only really heavy raw materialis the battery plates, for the remaining material is placed in a standard container.

The particulates were collected as follows. A sample of particulates (about 500 g)emitted in the lead recycling process was taken from a baghouse. This sample was pre-pared for chemical analysis X-ray fluorescence (XRF) at LAMIR—Minerals and RockLaboratory.

Samples of slag from the recycling process were collected during 3 days from threedifferent lead slag ladles, one on each day. These samples were cut into three portions,i.e., lower, intermediary and upper portion. The slag was broken down into small piecesand ground to remove a representative sample, then pulverized in a tungsten carbide millprior to preparing pellets, which were chemically analysed by XRF at the aforementionedlaboratory.

3. Results and discussion

The results of the chemical analysis of the particulate by XRF revealed that the mainchemical component was lead, which accounted for 82.28%, as shown in Table 2.

Table 2X-ray fluorescence analysis of the particulate

Element (%)

Pb 82.28Cl 9.55Fe2O3 2.85K2O 1.53SiO2 0.65Sn 0.61Zn 0.54P2O5 0.42CaO 0.36Sb 0.34Nd 0.22As 0.21Zr 0.19Br 0.18Se 0.04Al2O3 0.03Rb 0.01

Total ∼100.00


Fig. 3. Emission of particulates proceeding from the rotary furnace.

The high percentage of lead (82.28%) in the particulate, identified by XRF analysisand shown in Table 2, indicates that the lead recycling process employed by the recyclingplant operates deficiently, for this lead is not being recycled. All this particulate (Fig. 3) iscollected in the baghouse, but only a small portion of this material (about 10 kg) is used inthe process. According to Brazilian legislation (CONAMA resolution # 316, of 29 October2002), the maximum permissible atmospheric emission of lead is 7 �g/Nm3.

The Fig. 4 shows the overall average of the main chemical elements found in the slagsamples analysed here.

The Fig. 4 presents the main joined chemical elements in the slag samples analysed bythe method of XRF and identifies the fact that the extreme amount of iron indicates that thelead recycling process operates in an inadequate manner therefore this element indicatesthat the process of reduction inside the rotating oven does not occur completely, causing anextreme loss of lead for the slag. Some factors can be also influencing the stage of reductionas, for example temperature, viscosity, quality and amount of used raw materials as vegetalcoal and iron.

Fig. 4. Analysis of slag from the battery recycling process.


Fig. 5. Slag as resulted in processing recycling lead.

The high percentage of iron, oxygen and sulphur found in the generated slag demonstratesclearly that Eqs. (4) and (5) do not occur completely inside the furnace and consequentlythe reduced lead does not finish if incorporating the same one causing a loss of materialwhich will be discarded.

The reactions do not occur due to the following factors such as temperature less than idealtemperature, insufficiency of reducing agent in this case the carbon source and presence ofexcess iron.

In accordance with the studies carried through in the recycling company, some aspectsin the process of recycling of the automotives batteries can be identified that are:

• Great variation in the production income.• Loss of lead for the slag (Fig. 5).• Economic and ambient damage.

The Fig. 6 shows secondary lead production data (kg) from the recycling plant corre-sponding to the recycling of used battery plates (kg) during the period of January throughSeptember 2004, while Fig. 7 indicates the production output during the same period.

Fig. 6. Balance of secondary lead production from recycled battery plates—January to September 2004.


Fig. 7. Secondary lead production volume—January to September 2004.

The Fig. 6 indicates that the number of used battery plates varies considerably, whichleads to an unbalanced process and, hence, to variations in the production of secondarylead.

The Fig. 7 illustrates the significant instability in the production output of secondarylead, which varies from 53.53% to 67.47%. We also found that there was a drop in theoutput of secondary lead.

This strong variation results from the following factors:

• The only really heavy raw material is the battery’s lead plate, which varies in eachproduction batch.

• The sand, charcoal and swarf are placed in a standard container and are not weighed. Asa result, there is a substantial loss of these raw materials used in the battery recyclingprocess, particularly of swarf and charcoal, for these materials do not have a constantgranulometry and are moreover stockpiled in the open air.

• The premixture of the components used in the recycling process is not homogeneous,another factor that compromises the process.

• Neither the temperature nor the chemical reaction inside the furnace are properly con-trolled.

• The process of pouring the melted lead into ingot molds requires improvements to reducespillage onto the floor.

Several proposals for improving the process have been put forward, e.g., weigh allthe raw materials utilized, improve the homogenization process, control the temperatureof the process, cover the swarf and charcoal storage areas, improve the exhaust system,and briquette the particulates, which have a high lead content. The lack of control of theprocessing temperature leads to the assumption that the loss of energy is substantial. Highlevels of iron in the process require high temperatures to melt the metallic lead, as indicatedin Fig. 4. Moreover, lower viscosities reduce the melt time. The properties established in the


Fig. 8. Comparison of secondary lead produced and slag generated in 2004.

melting of the lead would also be improved, and less lead would be lost in the slag, accordingto the diagram proposed by Lewis and Beautement (2002) (ABNT, 2004) with the use ofNa2CO3 to work at a lower temperature and a better viscosity. With the implementation ofsome of these suggestions in the process, an improvement of about 70% would be achievedin the output of secondary lead.

Based on the average quantity of lead produced during the test period depicted in Fig. 8,400 kg of slag are generated for each ton of lead. Thus, the process employed by the recyclingplant studied here generates 14.3% more slag than the maximum limit determined by theliterature, and 33.3% more slag than the minimum limit established by the literature.

Fig. 9 reveals a very substantial disproportion in the quantity of secondary lead producedand the amount of slag generated. The best result achieved is 73% of secondary lead and27% of slag, while the worst result is 53% of secondary lead and 47% of slag. Of the

Fig. 9. Percentage of secondary lead produced and slag generated in 2004.


16 samplings taken at the recycling plant, the overall average results were as follows:production of secondary lead – 60.05% and generation of slag – 39.95%. The poor qualityof the charcoal used in the process may also strongly influence the quantity of lead producedif it is not used proportionally to the other raw materials, thus generating larger quantitiesof slag.

4. Conclusions

This work enabled us to draw several conclusions about the production, consumptionand recycling process of battery plates to extract secondary lead. The slag produced in thelead recycling process and the emissions of particulates are responsible for most of theworld’s lead-related environmental degradation. Production yields of secondary lead varygreatly because the process is inefficiently operated, lacking in such basic requirements asan adequate procedure and standardization, technology and technical know-how. However,a major part of these problems can be solved by adopting the improvements proposed here,particularly insofar as it concerns a standardization of the operating system, improvingthe yield and rendering it more homogeneous. With support for research and the help ofrecycling plants, a hazardous industrial waste can be transformed into a raw material forthe production of a new product, thereby meeting environmental and labor laws.

Acknowledgments

The authors would like to acknowledge the Federal University of Parana (UFPR) andthe Laboratory of Environmental Technology (LTA).

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Technological improvements in automotive battery recycling