IME Process Metallurgy and Metal Recycling, RWTH Aachen University Prof. Dr.-Ing. Dr. h.c. Bernd Friedrich Development of Secondary Antimony Oxides for the Application in Plastic Products F. Binz, B. Friedrich EMC 2015, June 15-17, Düsseldorf

Applications of antimony Source: EU

Production of antimony trioxide – state of the art Filtered air Pure antimony Cooling Filtered air Antimony trioxide Bagfilter Rotary drum furnace Sb 2 O 3 Wt.-%Pb [ppm]As [ppm]Fe [ppm] Grain size [µm] > 99,80< 1000< 750< 300, Requirements for product quality Source: Campine

Global antimony reserves More than 50 % of global reserves on Chinese territory Source: USGS MCS 2011

Price development Source: DERA Global shortage of supply Tightening of exports - China Floods - China Export restrictions, mine closing - China nominal price antimony real price antimony real price antimony trioxide

Project goals Sb-rich residues from lead softening Direct fuming of qualified antimony white from drosses Validation of applicability Antimony trioxide production from lead refining residues creates independency for European suppliers

Origin of feed material for fuming Softening Decopperised bullion lead Soft lead for further refining Air / O 2 Pb-, Sn-, Sb-,As- oxides Low selectivity from air blowing Slag always contains multiple elements High effort to treat slag / limited usability Low selectivity from air blowing Slag always contains multiple elements High effort to treat slag / limited usability Sn %As %Sb % Sn-rich12,211,218,6 As-rich0,616,28,5 Sb-rich0,34,032,2 Typical slag compositions

Vapor pressure modelling I PbO content in drosses is considered the major barrier for fuming of a qualified product Extensive partial pressure calculations are carried out to determine process boundaries regarding PbO content in feed material and fuming temperature Vapor pressures and activities are taken into consideration Partial pressure ratio as outcome is directly linked to condensate composition

Vapor pressure modelling II p Sb2O3 / p PbO Calculated partial pressure ratio as indicator for product quality Condensate requirement Industrial dross compositions Desired dross compositions State of the art drosses are not suited for a fuming process due to high PbO contents  Preconditioning of the feed material is necessary An increase in fuming temperature decreases selectivity  trade off between productivity and quality

Dross conditioning by increased selectivity in softening Highly selective oxidation of Sn, Sb and As by oxidation with defined oxygen partial pressure By-element concentration Pb Sb-rich dross low in accompanying oxides is won in second oxidation stage Usage of rotary injectors to compensate kinetic disadvantages N 2 + O 2

Experimental procedure Crude lead analysis Calculation of specific oxygen concentrations Melting of 400 kg crude lead Oxidation with Sn- specific O 2 content Oxidation with Sb- specific O 2 content Change in slag colour Sn wt.- %As wt.-%Sb wt.-% 0,4970,4336, °C

Sb rich drosses composition Sb dross PbO Wt.- % Sb 2 O 3 Wt.- % SnO 2 Wt.- % Cd ppmAs ppmSe ppmTe ppm 142,652,81, ,056,20, ,356,40, ,655,30, Milling of dross to < 90 µm Analysis by XRF Selective oxidation with low oxygen partial pressures nearly doubles Sb 2 O 3 content compared to industrial practice Desired 70 Wt.-% Sb 2 O 3 could not be reached  reduction of PbO content is necessary Arsenic is lower than 0.7 Wt.-% in all drosses  importance for fuming

Dross conditioning by selective reduction Industrial Sb-rich dross Reduction step Low Sb (< 10 %) lead phase High Sb 2 O 3 (> 70 %) slag phase Petcoke Refining Fuming  Optimal coke addition and temperature need to be determined Sb 2 O 3 [%] PbO [%] ZnO [%] SnO 2 [%] As 2 O 3 [%] 35,762,50,890,30,11

Experimental Procedure Milling Reduction for 60 min at desired temperature Separation of Slag and metal after cooling 300 g Dross X g Petcoke Mixing Slag Metal Milling XRF Remelting Spark emission spectrometer

Results Selective reduction allows preconditioning of slags to Sb 2 O 3 contents > 70 Wt.- % Stoichiometric coke addition in regards to PbO + C  Pb + CO should not exceed a factor of 0,6; obtained products at 800 °C are SlagPbOSb 2 O 3 Fe 2 O 3 ZnOSnO 2 As Wt.-%21,575,20,691,571,240,18 MetalSbPbAs Wt.-%7,6192,220,015 Increasing antimony losses to metal phase

Antimony white fuming Improved softening process State of the art softening Selective reduction Lead bullion Air / O 2 Coke Defined N 2 / O 2 mixture Lead bullion Pb Dross, ~30 Wt.-% Sb 2 O 3 Pb Dross, >70 Wt.-% Sb 2 O 3 Pb If dross >70 Wt.-% Sb 2 O 3 If dross < 70 Wt.-% Sb 2 O 3 Qualified Antimony white PbO rich residue Proposed flowsheet Sb 2 O 3 Wt.-% Pb [ppm] As [ppm] Fe [ppm] > 99,80< 1000< 750< 30

First fuming results

Summary and outlook Thermochemical considerations reveal that state of the art Sb-rich drosses are not suitable for direct fuming of antimony white  Sb-enrichment is crucial Two methods have been evaluated in lab scale to achieve Sb-enrichment > 70 Wt.-% in drosses 1. Optimization of softening to increase selectivity by controlled oxygen partial pressures 2. Sb-enrichment in drosses by selective reduction of PbO Until now desired enrichment can only be achieved by a reduction step or combination of both processes First trials show possibility to fume qualified antimony white from drosses Second project half will focus on fuming A new lab-scale installation allows research regarding optimal fuming parameters Upscaling to industrial scale furnaces

IME Process Metallurgy and Metal Recycling, RWTH Aachen University Prof. Dr.-Ing. Dr. h.c. Bernd Friedrich EMC 2015, June 15-17, Düsseldorf Thank you for your attention! Acknowledgements: The project upon which this publication is based is funded by the German Federal Ministry of Education and Research under project number 03X3592. This publication reflects the views of the authors only.