"*
Recyclingof nickel-cadmium
batteriesand processwastes
processes and operations of the
new SA6 NlFE plant.
-
Feeding systems lor sludge
and powderwasles
residues
HfQ
IO,
N.-E. Barring
SAB NIFE, Sweden
During the1970s big investmentswere madeinventilation and
enclosuresatthemanufacturingplantinoskarshamninorder
to reducetheconcentrationofcadmiumdust in the workplace
air. The ventilated air had to be cleaned to meet the emission
standards set by the authorities, and this resulted. in
considerably increased amounts of separated filter dust,
composed mainly of cadmium and nickel oxides. Awaste
water treatment plant was also built in which thevarious liquid
wastes from the manufacturingprocesses are treated before
being dischargedtotheBalticSea.In this plantcadmiumand
niqkel are removed from the liquid wastes by hydroxide
precipitation, flocculation, sedimentation, flotation and finally
separation and dewatering of the hydroxide sludge in a press
filter.The maximum accepted concentratlonsofcadmiumand
nickel in the purified water correspond to a maximum daily
discharge of 0.07 kg cadmium and 0.7 kg nickel.
Recovery of cadmium, nickel and cobalt from sludges
and filterdust
The above mentioned control and purification processes
produceconsiderable amountsofsludgeandfi1terdust.These
wastes, which contain high concentrations of cadmium and
nickel, must be treated by safe methods and at reasonable
costs.A recycling plant was built in close cooperation with the
National Environmental Protection Board and with the local
authorities responsible for controlling pollution. The recycling
capacity of the plant was designed to allow for the wastes
produced by a North American subsidiary in a new battery
manufacturing plant similar to that in Oskarshamn to be
shipped to Oskarshamn for treatment. Furthermore, large
amounts of wastes from earlier operation of the plant had
accumulated and these were also to be recycled.
The recycling system, which began operation in 1977, is
shown schematically in Figure 1. Some important data
concerningthe plantare given inTablel.About100 tonnesof
filter cakes from leaching residues and iron hydroxide
precipitates are produced annually in the plant. These filter
cakescontainsmallamountsofcadmiumandnickelsoitwas
necessaryto find asafe andeconomicwaytodispose ofthem.
Finally, after several discussions with the responsible
authorities about possible alternatives, it was decided that the
filter cakesshouldbedumped inacontrollableareawithin the
communal landlillforsolidwastes.This area isseparatedfrom
those where household and normal induslrial wastes are
dumped.The liltercakewaste is put on a bedoffinegroundraw
IimeaboullOcm thickandthe flow of rainwater is monitoredby
I
I
pH 1 3
1
%SO,
Pure
Steam
Water
Leaching
60°C
Introduction
The NlFE battery was invented by the Swede Waldemar
Jungner and hassince1910 been producedbyNlFEJungner.
The base product is the open nickel-cadmium battery with
pocket electrodes and alkaline electrolyte. Today these
batteriesare producedandmarketedbytheSABNIFEdivision
of the Sonesson Group. About 90% of the batteries are sold
outside Sweden. Technical development and main
production are centralized at Oskarshamn, Sweden, but
batteries are also manufactured at several of the
18subsidiaries in Europe, North and South America and
Australia.
I
Leaching
+
Separation of cadmium
by slectrolysis
Separated Steam NaOH
iron fraction
I
I
,
60'c
H&O,
H20,
1
P"W
nicks4
and
H,SO,
cobalt
sulphate
SOI"t10"
led directly
IO process
lor making
active nickel
material
I
Separation 01 lron
pH38
Steam
Na2S
1
___1
f
Alkaline sludge from
waste-water treatment plan!
I
Separation Of cadmium
residues as CdS
tip
H~O
s t y
Converting CdS
toCdSO,
,
CdSOaSalutlon
I 1. Cadmium, nickel and cobalt recovery system
Table 1. Recovery plant data
Capacity
Processed wastes
Recovered cadmium
Recovered nickel
Recovered cobalt
Residues to be disposed
Filtercakes of leached wastes:
FrI!ercakes of ikon precipitate:
Recovery eniciency for cadmium:
tonnelyear
365
17
44
I
40
55
99.7%
sampling at the lowest point of the area. A dumping area for
15 years operation has been prepared by the communal
agency responsibleforthelandfill.ThisagencYwillalso handle
the dumping of the filtercakes at a somewhat increased rate.
Processes for the recyclingof production scrap and
scrap batteries.
The scrap batteries being recycled are initiallyoftheNlFEtype
but small nickel-cadmiumcells of the sealed type can also be
treated. This latter type of cell is no longer produced by SAB
NlFE butan increasingnumberare being imporiedand used
in differentkind of tools, calculators. electric shavers, etc. The
normal procedure has always been that customers have
returned worn-out batteries to the company. For many years
the major part of the cadmium and nickel was recycledfrom
these scrap batteries. The processes used would not have
been acceptable by today's quality standards for
environmental protection and the operation was halted at the
beginning of the 1970s. A large number of returned scrap
batteries have since been accumulated by the company. As
more stringent rules against Pollution are being introduced in
many countries, the supply of scrap of all types of
nickel-cadmiumbatteries seems to be very large compared
with the available recycling capacity.
A differentSOUlCe Of nickel-cadmiumscrap is the pocket scrap
arising during electrode manufacturing. Differentcotours on
the Plates from the cadmium and nickel electrode production
$
,. i
i .
..~
:,
.i
i
,,
..
.
.
.
,'
.
lines makes itpossibletosoltthisscrapin asafeand easy way.
--Thecadmium and nickel pocket scrap is crushedseparately
inadisintegrator.Thecadmiumandnickelmaterialsaresifted
from the steel scrap and a more complete separation is
achieved magnetically. The steel residuesfromthe cadmium
electrode scrap are treated further together with the other
cadmium-containingmaterials.
Figure 2 outlines how the scrap batteries are dismantled and
how the cell components are dealt with in the following five
treatment steps:
(1) Positive plates containing about 18% nickel together with
graphite and iron. These plates are sold to steelworks.
(2) Cell cnntainers of steel containing bottom sludge rich in
cadmium and nickel. The containers are treated in two
steps with sulphuric acid to bring the sludge into solution
andarethenwashedwith water.Theacidso1ution istaken
tothe leachingstepinthechemicalrecyclingprocess.The
wash water is usedfor makingupnewsolutionsfortheacid
treatment The steel scrap is sold.
(3) Cell containers of plastic materials are treated in the same
way as thesteelcontainers.Thecleaned plasticcontainers
are ground to granules which are packed and sold.
(4) Negative plates, which are the cadmium electrodes
containing mainly cadmium and iron. These plates are
rinsed in water to remove the crusts of carbonate formed
on exposure of me plates to the air. The plates are then
placedinaretortfurnaceandheatedt0850"C whereupon
the cadmium is distilled. The metal is condensed and
collected in a receiver from which it is directly cast into
sticks. These cadmium sticks are used as raw material in
the production of cadmium electodes. The distillation
processisperformedinareducingatmosphereinorderto
reducethe cadmium residueas far as possible.
(5) The consumer type sealed nickel-cadmium cells
containing nickel, cadmium, iron and plastic material.
These cells. which are cylindrical or button shaped, are
packed indrums.Thedrumsareplacedinaretortfurnace
and heated to 400-500°C in an atmosphere with a slight
excess of oxygen. In this pyrolysis step the plastic material
isdecomposedintogaseswhichareburntinagas burner
at 900°C inan excessof air. The exhaustgases are washed
in a wet scrubber to remove chlorides and any fluorides
present.When the pyrolysis IS over the temperature in the
retort furnace is increased to 850°C and cadmium is
distilled as described in (4) above. The residues of the
distillation contain about 30% nickel and are sold, as are
the large amounts of distillation residues from (4).
Theventilationair from theventilation hoods iscleanedin a bag
filter while the rest of the ventilation air from the building has to
pass through a dust collector with a cassette filtering element.
Thisisalsoasafetyfilterin the eventof an unforseendischarge
occuring at the furnaces.
Some importantdesigndatafortherecyclingplantaregivenin
Table 2.
Operating experience.
The chemical recycling plant has functioned well from the
outset and the expected results have been obtained. There
have of course been problems, for example difficulties in
removing the acid aerosols developed during cadmium
electrolysis,butthesehavebeensolved and the plantfulfillsthe
high quality standards set for both the internal and external
environment As the depressed raw material prices for
cadmium are to some extent balanced by increased nickel
prices, the economic return of the operation is quite
satisfactory. This is especially true if the additional costs of
handlingthese problemwastes withoutrecyclingare included
in the cost estimate.
In the battery recycling processes on the other hand, there
have been several difficult problems during the running-in
period. After some additions and modifications to the
equipment it now seems that the mechanics are working
satisfactorily.Thethermal part ofthe process is in theory simply
a distillation of cadmium but in practice it is an advanced
process with irilricate material choices. Difficultiesin finding
the appropriate quality of material for some key parts of the
equipment have caused most ofthe problems. It is too earlyto
say that all these problems have been solved but the plant is
now in continuous operation.
Both the recycling plants were built with economic support
from the NationalEnvironmentalProtectionBoard as full-scale
demonstration plants. The recycling systems, the scrapping
machines and the furnace processes were developed at the
company to be applied directly in the full-scale plants.
Table 2. Design data of plant for recovery of scrap nickel-cadmiumbatteries.
C.p.slh
Rconmd m d m u d matbrial
Cadmium (recovery efficiency $!9.5%)
NicKel-containing iron scrap (mainly nickel pocket plates and nickel sinter)
mer iron scrap (distillationresidues and steel containers)
Flastic material
1000 tonne banetieslyear
150 tonnelyear
340 tamelyear
480 tonnelyear
30 tonnelyear
mote.
Banery derails such as Ids and Separators
Emissions of cadmium dust wilh piocess ventilation
Waste water discharged to waste water trealmenl plant
Cadmium in the waste water
2 tonnelyear
15 kglyear
2 200 m3lyear
400 kglyear