THE CLEANLEAD PROJECT: “DEVELOPING A NEW CONCEPT ‘CLEANLEAD’ FACTORY FOR EUROPE”
A Pproject
partially founded by the European Union within the “GROWTH
PROGRAMME”. This three
year Pproject had a duration of
three years, and it has been was successfully completed in accomplished
on April 2004.
PROJECT PARTNERS INVOLVED
Técnicas Reunidas S.A. (ES), Britannia Refined Metals Ltd (UK), Orzel
Bialy S.A. (PL), Instytut Metali Niezelaznych (PL), Coventry University (UK),
Lafarge Plasterboard Ltd (UK), Faculdade de Ciéncias da Universidade de Lisboa
(P), Netherlands Organisation for Applied Scientific Research (NL), Magneto
Special Anodes B.V. (NL), Membraan Applicatie Centrum Twente (NL), Kovohute Prĭbram
A.S. (CZ), Institute for Nonferrous and Rare Metals (RO)
OBJECTIVES
Secondary lead consumption is certain bound to
raise due to an ever
increasing demand
for lead acid batteries for the demand for automotive
industry, and also related to new uses
such as the electric vehicles andor
hybrid vehicles, solar and renewable energy storage and,
portable and auxiliary batteries in emergency systems, etc.
The lead battery recycling industry currently faces the challenge of
improving the conventional processes
aiming to avoid toxic wastes generation (slags, mattes, etc) generation
and trying to complying with the
more stricter environmental regulations.
The CLEANLEAD pProcess
provides a new, low energy
cost, zero-waste generation sustainable option which
can substantially improve substantially the
current lead smelting operations. The new process has been developed to deal
efficiently with the whole batteriesy
components, includinge.g.
drained acid treatment, optimisation of the smelting stage and
hydrometallurgical treatment of the battery pastes.
Cleanlead Process Conceptual Diagram
DRAINED ACID TREATMENT
The CLEANLEAD Process for drained acid treatment not only prevents the
current production
of sludge for disposal from being produced, but also turns
the acid into reusable products. Depending on the applied process option,
commercial synthetic gypsum, or acid for new batteries may be produced refilling
or biotreatment may be used on theof
effluents can be performed. This wide range of purposes
options
makes the described technology applicable
suitable
for to many different cases applications and
industrial problems.
Commercial Gypsum Production
Detail of the gypsum product
Current processes turn the drained acid containing metallic impurities
into a waste sludge for disposal by adding lime or sodium hydroxide. This treatment has severeimplies
associated environmental costs. The CLEANLEAD Process makes commercial synthetic
gypsum through drained acid purification by means of membrane techniques such
as diffusion dialysis and nanofiltration or chemical precipitation prior to lime
addition. The CLEANLEAD synthetic gypsum fits complies with the
specifications to be used asfor feed
material in the
plasterboard industry, as an additive in the cement industry and also in
floorscreeds manufacturing since the process can be
conducted
adjusted
to get different gypsum products. Besides environmental advantages,
producing commercial gypsum versus in place of an acid sludge is economically
attractive.
Obtaining reusable battery acid
presents attractive economic revenue.
Membrane Electrolysis cell
The Ddeveloped
electrochemical process allows obtaining can produce a clean
and concentrated sulphuric acid (30% w/w) suitable for filling new
batteries refilling through . This is achieved
with electrodialysis technology, yielding efficient removal of the
metallic impurities.
Biological treatment
The CLEANLEAD Process also provides
includes biotreatment
of drained acid blended with other industrial alkaline effluents (landfill
leachates, etc) by means of biologically produced H2S to remove the impurities and yield getting
finally a non non-polluting final productstream.
OPTIMISED SMELTING OPERATIONS
Improved Operation
Rotary Furnace
Desulphurised battery paste smelting methods were developed within the
CLEANLEAD project as an alternative to conventional raw paste smelting. Very positive
results have been obtained in trials performed in a 500 kg rotary furnace,
which are summarised as follows:
• Ddecreaseding
smelting temperature up down to 900 ºC
• 3-4 times shorter smelting time
• Sslag
amount reduction by 65-75%
• Sstable
silica slag type being produced
• Rreducedtion consumption of
fluxes and reductants consumption
• Llead
bullion yield up to 75% of the charge mass
• Ddusts
volume reduction and low SO2 emission
Producing Stable Slag
Electric Furnace Isasmelt Furnace
Further achievements on preventing unstable slag from being produced are
available within the CLEANLEAD technology. Conventional unstable sodium-based slag can be re-smelted in an electric arc furnace. Tests carried out in
a 80 kVA pilot unit confirm that re-smelting
of soda slag in the presence of iron oxides and sand produces non-toxic stable
ferrosilicate slag. In addition, some matte is generated, which reduces SO2 emissions.
Another way developed process uses deals
with using the sodium sulphate slag from an Isasmelt furnace as
flux in athe
rotary furnace. In
tests Tthis slag performed as well as the currently
used sodium carbonate flux and therefore can replace it, thus reducing the operating cost.
Benefits
The technological innovations described above have been integrated in the CLEANLEAD
optimised smelting process, which providespresents
great flexibility and important
improvements to suit local operating requirements. The gathered
benefits of the optimised smelting processes are:
·
ØStable
ferrosilicate slag is
produced complying withwithin current and future
environmental regulations is produced, avoiding the current
generation of unstable and toxic sodium-based slag.
·
ØElimination
or substantial reduction of SO2 gas emission.
·
ØDecreaseding
energy consumption and total operating
costs.
·
Ø Improveding process performance and environmental aspects
impact
of furnace operations.
HYDROMETALLURGICAL TREATMENTy
A Novel
Process as an Advantegous
Optiona
Preferred Alternative
to Smelting
Lead Electrowinning Pilot Cell
A novel process under in the CLEANLEAD
technology deals with the hydrometallurgical treatment of battery paste to
obtain pure Pb. This approach stands as is an
advantageous
superior alternative option
to smelting and offers zero waste and low cost sustainable
technology.
An Eco-efficient and Low Cost Technology
In this process, battery paste is reduced and desulphurised to render it
suitable for feeding a low energy lead electrolytic process. Reduction is
carried out by adding drained battery drained
acid together with a small amount of lead bearing sulphides such as mattes, concentrates,
fumes, etc., as reducing agents, which givesinvolve
lower costs and an extra amount of improved lead recovery
eventually recovered. The desulphurisation is performed with
sodium hydroxide, which is regenerated in a subsequent step. This saves consumable
the cost of consumables
and produces valuable gypsum. Desulphurised paste is leached with sodium
hydroxide at 60 ºC, and then the pregnant solution containing dissolved lead
passes to lead electrowinning in alkaline media, having an energy requirement
of 0.5 kWh/kg Pb and current efficiencies close to 100%. The developed
electrolytic process shows important technical and environmental advantages,
and offers present
lower operating costs than conventional lead smelting technology.
Vesatility of
Products
As an alternative to lead electrowinning, the CLEANLEAD pProcess
also allows pure Lead Oxide production at very competitive cost, which is
suitable for new pastes the manufacturing
of new pastes or other industrial applications.
The CLEANLEAD Process represents a radical innovation and definitive
solution to the current problems the secondary lead
industry is presently facing in Europe and worldwide.
The new technologies deal efficiently with all battery components, e.g.
drained acid, metallic lead, and pastes, proposing providing the
best solution infor
every case.
Sustainability is a must for is fundamental to the
developed CLEANLEAD process, by pursuing zero-waste emissions, getting
obtaining
substantial savings in operating and environmental costs, and producing
reusable valuable products instead of toxic wastes or slags generated by
conventional smelting processes.
High quality and diversified products can be obtained, such as pure lead
oxide, pure electrolytic lead, commercial gypsum, etc.
The Pprocess provides versatility
and flexibility, which can be implemented as a whole or step by step, and easy to be easily adapted
to local industrialy
conditions and requirements.
CONTACT
PERSON: Mr. Carlos Frías,
TÉCNICAS REUNIDAS, S.A., R&D Division
Calle Sierra Nevada,
16 - San Fernando de Henares - 28830 Madrid (SPAIN)
Phone: 34 91 6558780;
Fax: 34 91 6558789; E-mail: cfrias@tecnicasreunidas.es