The waste battery scrap can be metallurgically treated to separate lead from various impurities such as sulphates, oxides and other metals in scrap. An attempt has been made to smelt the treated battery scrap for recovery of lead as well as for SO= pollution abatement

Basak, A C

Bhattacharya, A P

Ghosh, S B

Maharaj, Lal

Ramachandrarao, P

Singh, O

Singh, S D

Vaish, A K

English

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PROCEEDINGS: NS-EWM1996® NML, JAMSHEDPUR, pp. 177-182Utilisation of waste battery scrapA.K.VAISH, S.D.SINGH, A.P.BHATTACHARYA, S.B.GHOSH,0. SINGH, A.C. BASAK, LAL MAHARAJ ANDP.RAMACHANDRA RAONational Metallurgical Libratory , Jamshedpur - 831 007, India.ABSTRACTThe waste battery scrap can be metallurgically treated to separate lead fromvarious impurities such as sulphates, oxides and other metals in scrap. An attempthas been made to smelt the treated battery scrap for recovery of lead as well as forSO,, pollution abatement.INTRODUCTIONThe storage battery scrap is the chief source of secondary lead production.More than 40% of the total lead consumption goes to the manufacture of batteriesand around 80 percent of it re-enters the markets as secondary lead. This secondarylead containing antimony is used in the battery manufacture. The battery consists ofpositive and negative plates which comprises of mainly 86 present PbO2 and 95percent Pb respectively, when fully charged. Generally these batteries are scrappedafter about two years' use. Apart from metallic lead in plates , connectors, posts etc.lead is present in the form of lead oxide and lead sulphate in the used up batteries.The wastebattery scrap treated in the present investigation was mostly free from leadplates and metallic lead and it mainly constitutes the oxides and sulphates of lead.However, thepresence of sulphate in the scrap is responsible for excessive fume lossand consequent lower recovery during smelting . The smelting of waste battery scrapis generally carried out in a blast or shaft furnace, a rotary furnace or a reverberatoryfurnace. In the present investigation an attempt has been made for better recoveryof metallic lead from waste battery scrap after its necessary treatment and also toavoid the S Ox pollution during smelting. The smelting was carried out in apilot scale.cupola furnace.Review of literatureLead can be recovered from waste battery scrap by electrolysis method aswell as smelting route. Ponomarev and Znev1'1 obtained compact lead of 99.5%purity from waste powder consisting of lead and zinc by electrolysis. The solution177A.K.VAIS et.al.from lead electrolysis was used for zinc extraction. Lead and its alloys can be refinedelectrolytically"' using an anode of impure metal or alloy and a cathode on whichpure metal is deposited. Recovery of used lead was successfully done by Panckenkoand Delimarskirt') by fused bath electrolysis. Waheed et alj41 tested battery wastesby electrolysis in alkaline solution with stainless steel as cathode and mild steel asanode. Dey etal's1leached the battery wastes containing sulphates with 20 percentNaOH solution and electrolysed the leach liquor between stainless steel cathodeand graphite anode to recover lead. Lead from the materials of storage battery flatwastes was recovered by Delimackie et all"] by electrolysis in molten NaOH withiron electrodes. Randaccio''' pantented a process by which different types ofscraps, viz. powder, filling etc. of various metals containing lead in sufficientamount can be treated to get higher recoveries by smelting. Reznik and Zarembaleisuggested processing the battery scrap containing 80% Pb and .2 to 3% Sb in a shaftfurnace with natural draft at 900°-1000°C with 2.5% of reduce. The recoveryobtained was reported to be 87%. The smelting of battery scrap in an electricfurnace without pre-treatment for the elimination of sulphur with high recoveryhas been claimed in a Japanese patent'91. The smelting of battery scrap has beenpractised fora long time, still the recovery of lead is not very good due to the slag-matte losses and sulphur fumes.Present InvestigationAn attempt has been made to recover lead from waste battery scrap after itstreatment with wash water and concentrated solution of soda ash. The objective isto mitigate the pollution of sulphur and increase the recovery of lead. Severalexploratory trials have been carried out in a pilot scale cupola furnace at the NationalMetallurgical Laboratory, Jamshedpur, utilizing the waste battery scrap.Process DetailsThe first set of experiments was carried out by smelting 60 kg of waste batteryscrap without any treatment. The charge consists of battery scrap powder, woodcharcoal, soda ash pellets, limestone lumps and mill scale. The typical chargecomposition was as follows :Waste battery scrap 60 kgWood charcoal 3 kgLimestone 1.8 kgMill scale 1.8 kgSoda ash pellets 2.1 kg178A.K.VAISH et.al.The second set of experiment was carried out with treated battery scrap.First, the whole mass of battery scrap was washed with water with a view to removethe sulphuric acid and then with a concentrated solution of soda ash at the ambienttemperature in order to remove the sulphur.In each case, the temperature in the smelting zone was around 1250'- 1300'Cand lead was tapped periodically. The typical analyses of waste batter scrap, slag-matte and lead metal is shown in Table-1. Fig. 1 illustrates a conceptual flow diagramfor the mitigation of lead particulates from exit gases of pilot scale cupola furnaceand another conceptual flow diagram for the mitigation of lead particulates as wellas SO,gases is shown in Fig.2.Table-1 : Typical analysis of waste battery scrap, slag matte and lead metalComposition (%)Pb SWaste battery scrap 75.04 5.38Slag matte 25.65.95*Lead metal 96 .91 2.49* % Pb in PbOPossible reactions during smeltingThe lead sulphate of battery scrap reacts with soda ash to from lead carbonatewhich decomposes to form lead oxide. Also lead sulphate reacts with calcium oxideto form lead oxide. Finally the entire lead oxide is reduced by carbon as well as byiron . The scheme of reactions is as follows :+ Na CO3Pb SO -> Pb CO3 + Na, S O44 2PbCO3 -> PbO + CO,CaCO, -> CaO + CO2PbSO4 + CaO -> CaSO4 + PbOPbO+C -> Pb+COPbO + Fe -> Pb +FeO179A.K.VAISH et al.RESULTS AND DISCUSSIONAs a matter of fact, the smelting of battery scraps has been in practice sincelong back, but the smelting processes are not economical basically due to lowrecovery of lead metal - for which both fume and slag matte losses and the sulphatepresent in the battery are responsible. If the sulphur can be removed from the scrapprior to smelting, the recovery could have increased considerably. In the presentsituation, the sulphur content in the battery scrap was treated by absorbing it in ahighly alkaline solution of soda ash. By doing so it was possible to remove majorportion of S O3 and acid mist along with SO2, as shown in Table-2. The main reactionoccurring are :Na2CO3 + SO2 -> Na2SO3 + CO2,NaCO3 + SO3-> Na2SO4+ CO2Table-2 : Typical analyses of treated and untreated battery scrap and lead recoveryS (%) Lead recovery (%)Without treatment 5.38 72.0With treatment 2.48 86.5Table-2 clearly indicates that by treating the battery scrap with alkalinesolution of soda ash, sulphur could be drastically brought down and lead recoveryimproved by 14%. During smelting of treated battery scrap, negligible amount ofreddish fumes, which are generally SO. mist, were coming out through the chimneywas observed. However, gas analysis is yet to be done to confirm this observation.The main source of loss of lead metal is the production of excessive fumes.Recovery can always be improved by collecting the fumes and treating them to recovermetallic lead. For this purpose, we have proposed two conceptual flow diagram (Figs.1and 2) for the mitigation of lead particulate matter, as well as to control the SOXemission. In the Fig. 1, the effluent gases containing lead particulates and SOX gas cometo the dust catcher where lead particulates are arrested. Exit gases from the dust catchersystem are brought-down to 150-250°C which finally enters the bag filter assemblywhere mostly fine lead particulates are arrested. Finally, the exit gas temperature fromthe bag filter are let off through the stack to the ambient air. A flue gas desulphurization(FGD) system has been proposed to abate the SOX gases before releasing to the ambientair which is shown in Fig.2. Literaturet10] survey shows that lead particulate matter couldbe arrested in a bed of activated carbon where the exit gas velocity is about 1-1.5 m/s.180A.K.VAISH et.al.AFTERBURNERTORCHC -AIRBLASTDUSTCATCHER niL\CHARGE HOODCHARGINGDOORLEAD /SLAGFINESCOOLEREFFLUENT STACKBAG FILTERS150-250%LEAD OXIDE & FINESEXHAUSTFANFig.1 : Conceptual flow diagram for the mitigation of lead particulatesSPRAY TOWERFOR ABSORBINGS02' GASEFFLUENTSTRCKLEAD t PACKED__ _ PUw (y^_SLAG TOWER - -isFOR ADSORBING LIME SLURRY EXHAUSTLEAD SPM PIT FANFig.2 : Conceptual/low diagram for the mitigation of lead particulates and SOx gals181A.K.VAISH et al.Here the novelty of this technique is that while the lead particulate matters areadsorbed on the surface of activated carbon of bituminous origin whereas the SOxgases are absorbed by activated carbon. This SOX gases are converted to H2SO4 whensprayed by water whereas lead particulates matters could be substantially recoveredby treating the bed with H2SO4. Even after this the gas is send through a wetscrubbing system with dual alkali (Na2CO3 and CaO) solution to arrest remainingSOx gases. The reactions schemes are given below :Na2CO3 + H2O + SO2-> Na2SO3 + H2O + CO2Na 2 SO3 + H2O + S02 -> 2 NaHSO3Regeneration process :2 NaHSO3 + CaO + H2O -> Na2SO3 + CaSO3. I/2 H2O + 3/2H2OCONCLUSION1. The treated waste battery scrap consisting of mainly the sulphates and oxidesof lead was successfully smelted almost without SO. pollution.2. The recovery of lead from treated waste battery scrap increased considerablybeyond 86.5%REFERENCES[1] Ponomaren , V.D. and Znev, B.N.Iznest . Vyschikh. Ucheb. Zavedenie, TsvetnayaMet2, No. 584-87 (1959).12] French Patent No.1338526, Aug. 16, 1962.[3] Panchenko, I.D. and Delimarskir, Yu.K., Zhur. Prikad Khim.33. 153-7 (1960).[4] Waheed, A.K.A et.al., Indian Chem. Engr. 3168-71, 179 (1961).15] Dey, Biman et.al (CSIR) Indian Pat. No.59,250, July 5, 1958.[6] Delimackie, Ya K et.al. Ukrain Khern. Zhur. 23, 817-2 (1957).(7] Randaccio, Cario, Ital. Pat. No. 531, 121, Dec. 1, 1955.[8] Reznik , I.O. and Zaremba, N.I. Sbornik Nauch Trudon Goserdarst Nauch- Issledovatel Inst.Tavetuyka Metal 1945, No. 10, 277-92.(9] lap. Pat. No. 10,654('57) Dec.21.(10] Heavy Metal Pollution Conference, Hydelburg, 1987, Vol.1-2.182

Utilisation of waste battery scrap

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Utilisation of waste battery scrap

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