Utilization of BFR plastics

Transcription

1 Utilization of BFR plastics in recovery of valuable metals during thermal treatment with solid wastes S. Oleszek-Kudlak, M. Grabda, E. Shibata, T. Nakamura IMRAM, Tohoku University, Japan IPIS PAN, Poland

2 Brominated Flame Retardants (BFRs) majority (38 %) of global production of bromine (Mehran et al., 2003) Tetrabromobisphenol A (TBBPA) 59 % of global production of BFRs in 2001 (Sarah, 2005) Reactive FR (90 %): epoxy resins, polycarbonate resins (20-25 wt % bromine) (Alaee et al., 2003) printed circuit boards (PCB) printed wire boards (PWB) Additive FR (10 %): acrylonitrile -butadiene styrene resins (ABS), high-impact polystyrene (6-18 wt % bromine) (Alaee et al. 2003, Maag et al., 2010) PC and TV set housing, PC monitors, another electronics, paper, textiles Waste of Electronic and Electric Equipment (WEEE)

3 Waste of Electronic and Electric Equipment (WEEE) Thermal processing Landfills disposal (co-combustion at MSWI, pyrolysis) Advantages: 3R of organic and inorganic fractions Disadvantages: Hazardous Emissions: PBDD/Fs,PBP, PBBz HBr (in flue gas) main products of TBBPA decomposition (Luda et al., 2003) May acts as bromination agent for selective volatilization of heavy metals from wastes (?)

4 1 a 1 M x O y (s,l) + HBr(g) = MBrz (s,l) + z o r Where: (x/a = 1/z, y/a = 1/2) P G = RT ln P o G r P THERMODYNAMIC CONSIDERATION - Bromination reaction of metallic oxides by HBr gas - 1/2 H2O HBr - standard Gibbs energy change of reaction (J/mol) - vapourpressure of the compound (atm) R - gas constant (J/mol K) T - temperature (K) 1 2 The order of reactivity of selected M x O y with HBr: H 2 O(g) PbO > Cu 2 O > CuO > ZnO > FeO > Sb 2 O 3 G o r, kj/mol Sb 2 O 3 SbBr 3 MnO MnBr 2 Ag 2 O ZnO ZnBr 2 CdO CuO CuBr 2 HgO HgBr 2 AgBr CoO CoBr 2 FeO NiO FeBr 2 Cu 2 O CdBr 2 CuBr T, K NiBr 2 Standard Gibbs free energy changes of bromination reaction of selected metal oxides

5 0 THERMODYNAMIC CONSIDERATION (II) - Vapor Pressures of Metallic Bromides - MBr x (s,l) = MBr x (g) G = RT ln P o v MBrx o G v - is Gibbs energy changes (J/mol) P - vapour pressure equilibrated with that of the pure compound (atm) R - gas constant (J/mol K) T - temperature (K) 0 BBr 3-5 TiBr 4 HgBr 2-5 TlBr BiBr 3 SnCl 4 SnBr 4 SbCl 3 Se 2 Cl 2-10 ZrBr 4 WBr 6 TaBr 5 log P, atm MoBr 4 ZnBr 2 TiBr 3 WBr 5 SbBr 3 NbBr 5 TiBr 3 ZrBr 3 FeBr 2 TiBr 2-30 MoBr ZrBr 2 3 NiBr 2 MoBr 2 CuBr AgBr /T, 1/K log P, atm BiCl 3 TeCl 4 InCl SnCl 2 InBr InCl 2 SnBr 2 TlCl InCl 3 BiCl PbBr 2 PbCl /T, 1/K

6 Concept diagram of the thermal treatment of solid wastes containing metallic oxides with BFR plastics BFR Plastics Solid Wastes Polymer CH CH 2 CH x Metallic Oxides (M x O y ) (PP, PS, ) CH 3 R (M = Zn, Pb, Cu, Fe, ) MBr z BFR (RBr) (TBBPA, DeBDE, ) HBr HBr 1 1 M Oy(s,l) + HBr(g) = MBrz (s,l) a z x + (x/a = 1/z, y/a = 1/2) 1 H 2 2 O(g) MBr z H 2 O Antimony Oxide (Sb 2 O 3 ) (Synergist) Thermal degradations of BFR plastics SbBr 3 H 2 O Vaporizations of HBr and formed SbBr M Oy(s,l) + SbBr3 (s,l) = MBrz (s,l) a z x + (x/a = 3/z, y/a = 3/2) Bromination reactions of metallic oxides 1 Sb 2 2 O 3 (s,l) Sb 2 O 3 Vaporizations of formed brominated compounds If BFRs-containing plastics might be used in practical bromination-evaporation process could open technical possibility of : recycling of selectively volatilized heavy metals, metals-free ashes (WEEE, ASR) simultaneous recycling of WEEE and metal-rich metallurgical dusts (EAF dust, plating sludge)

7 Steel production in an electric arc furnace (EAF) generates a flue by-product called EAFD dust (EAFD). Element Fe (ZnFe 2 O 4, Fe 3 O 4, Fe 2 O 3 ) Zn (ZnO, ZnFe 2 O 4 ) Pb (PbO) EAFD chemical composition: Leclerc et al., Si, Mg, Ca, C, K, Na, Al, Cu, Cr, Cd, Mn, Cl, F Some million tones of EAFD requiring disposal annually worldwide (Mehran et al., 2003) The worldwide generation of EAFD represents a possible recovery of 1.4 million tones of zinc (ebfrip.org) There are two major methods for treatment of EAFD (Pickles, 2009): 1) chemical fixation and stabilization (CFS) for landfill, 2) recycling for metal recovery (pyrometallurgical (HTMR-Waelz), hydrometallurgical or hybrid pyro-hydro techniques )) 3) simultaneous recycling with WEEE (bromination-evaporation process)???

8 PURPOSE OF THIS STUDY: recognize the reactivity of ZnO with HBr, main product of thermal decomposition of TBBPA recognize the behavior of the bromination reaction products

9 EXPERIMENTAL INVESTIGATION - Reactivity of selected metallic oxides with bromine - EXPERIMENTAL METHODS Quartz-tube reactor heated by small furnace (Furnace) SAMPLES PREPARATION Mixture of TBBPA with ZnO have been prepared according to stoichiometric mass ratio (3.34:1) (additionally: 5.17:1). SAMPLES QUALIFICATION EPMA, XRD, IC, ICP, GC/MS analysis of products in solid residue and vaporized phase after thermal treatment.

10 Experimental set-up for quartz-tube reactor experiments Furnace 2 g sample (4 tablets x 0.5 g) Quartz wool filter (300 mg) Quartz tube reactor Argon flow 50 ml/min (5 outlet TBBPA d.p. # EPMA XRD ZnBr 2 ICP IC ZnO ICP + inner wall precipitations ZnBr 2 TBBPA d.p. ICP, IC GC/MS Water 75 ml Furnace - Experimental conditions 140 C 3. Heating 10 C / min HBr * 420 C TBBPA d.p. # * 340 C 290 C 250 C 150 C IC GC/MS * 650 C * 550 C Hexane 75 ml Product of thermal decomposition of TBBPA GC/MS Expected products Analytical methods 2. Isothermal 60 min # TBBPA d.p. - product of thermal decomposition of TBBPA 1. Heating 10 C / min 4. Fast cooling 25 C * done in triplicate Average Values and Standard deviations were calculated

11 RESULTS: TIC of organic products from the thermal treatment of TBBPA:ZnO (3.34:1). No organic products were found in the hexane trap Solid residue Vaporized compounds 150 o C o C o C o C 16 Intensity (-) 290 o C o C o C x x x x o C / 550 / 650 o C x x x x 420 / 550 / 650 o C Retention time (min)

12 Weight [g] Fate of Bromine and Zinc at various temperature [%] Solid residue (Total) Zn in solid residue (ZnBr 2 ) Temp. TBBPA: ZnO Zn in solid residue (Total) Temperature [ C] Condensed phase (filter only) Zn vaporized (ZnBr 2 ) Br released Zn brominated of total Zn Zn vaporized of total Zn ± 4 61 ± 0 28±1 45 ± 1 7 ± 2 9 ± 4 REWAS (5.17:1) October 12-15, 2008 Cancun, Mexico Zn [g] Zn vaporized of Zn brominated Weight change of solid residue and Zn Distribution during thermal treatment of TBBPA and ZnO Zn loss Unreacted Br for Released Br C % % % % % % 150 (3.34:1) ± 1 64 ± 1 0 ±0 1 ± 0 4 ± 3 1 ± ± 4 67 ± 1 0 ±0 1 ± 0 2 ± 2 1 ± ± 3 63 ± 2 4 ±0 6 ± 1 4 ± 3 6 ± 5

13 Experimental set-up for isothermal runs Furnace Quartz tube reactor Ar flow 50 ml/min Argon flow 50ml/min + 5(20)vol%O 2 2 g sample (4 tablets x 0.5 g) Quartz wool filter (300 mg) + inner wall precipitations Water 75 ml Hexane 75 ml outlet Heating conditions: - ZnO bromination efficiency- ZnBr 2 ZnO ZnBr 2 TBBPA Product of thermal C d.p. # (every 10 C ), 340 and 420 C TBBPA isothermal d.p. heating TBBPA for d.p. 40 # min decomposition (temperature of effect) , 270, 290, 310 C isothermal heating for (5) (140) min TBBPA (time effect) EPMA ICP ICP - ZnBr XRD 2 vaporization IC efficiency- ICP, IC GC/MS HBr IC GC/MS GC/MS C isothermal heating for 40 min (temperature effect) Expected products Analytical methods # , TBBPA 550, d.p product C of isothermal decomposition heating for of TBBPA 10, 40, 80 min (time effect)

14 RESULTS: 80 Effect of temperature (A) and time (B) on ZnO bromination rate (%) Zn bromination Br release Zn (ZnBr2) vaporized (A) Effect of temperature TBBPA:ZnO (3.34:1) 40 min Temperature( C) Zn bromination rate (%) C 270 C 290 C 310 C Time (min) (B) Effect of time TBBPA:ZnO (3.34:1)

15 RESULTS: Zinc (ZnBr2) vaporized (%) Time (min) Effect of time (A), temperature and atmosphere (B) on ZnBr 2 vaporization yield 490 C 550 C 650 C 490 C 5%Oxygen 550 C 5%Oxygen 550 C 20%Oxygen Char residue (%) at the following heating (A) Effect of time during thermal conditions treatment of TBBPA:ZnO (3.34:1) 490 C 550 C 650 C 10 min (B) Effect 30 of temperature 21 and min atmosphere 25 during 18 heating of - 80 min TBBPA:ZnO (40 min) Argon 5% Oxygen 20% Oxygen 30 Zn (Total) Vaporization [%] Char [%] Zn (ZnBr2) for brominated Zn Zn (ZnBr2) for total Zn Zn (Metallic) for total Zn Char * ** 650* ** ** Temperature [ o C] The temperatures marked by asterisks indicate different time of thermal treatment: * - 10 min.; ** - 80 min.

16 Concept of bromination-evaporation of ZnO during heating with TBBPA 1. T < 180 C Compressed mixture of TBBPA + ZnO TBBPA ZnO Ar + 20% Oxygen 2. T = C Zno covered by melted TBBPA TBBPA melted Ar + 20% Oxygen ZnO 3. T = 250 C Ar + 20% Oxygen 4. T = 280 C Ar + 20% Oxygen Initial decomposition of TBBPA, fomation of ZnBr 2 TBBPA melted ZnO HBr HBr ZnBr 2 HBr Char-bounded ZnBr 2 and remains of unreacted ZnO ZnO ZnBr 2 HBr HBr Char 5. T = C Ar + 20% Oxygen 6. T = 550 C (80min) Ar + 20% Oxygen Oxidation of char and progresive vaporization of liberated ZnBr 2 ZnO ZnBr 2 Complete oxidation of char and vaporization of ZnBr 2. Remains of unreacted ZnO Char ZnO ZnO ZnO

17 CONCLUSIONS (I): Decomposition of TBBPA in the presence of ZnO (3.34:1): - proceeds between: o C (isothermal heating) o C (heating 10 o C/min) - releases of 64% (270 o C) of the total amount of bromine present in TBBPA Most of the inorganic bromine (96 % at o C) released from TBBPA is promptly utilized in the reaction with ZnO

18 CONCLUSIONS (II): The bromination of ZnO occurrs at max yield of: dynamic heating (10 o C/min) 67 % for TBBPA:ZnO (3.34:1) 81 % for TBBPA:ZnO (5.17:1) isothermal heating (60 min) % for TBBPA:ZnO (3.34:1) The bromination yield: - is dependent on quantity of HBr available around particles of ZnO - increases with temperature below 280 C/340 C (isothermal/dynamic) - increases with time at temperatures below 310 C (isothermal)

19 CONCLUSIONS (III): Volatilization of the formed ZnBr 2 (at Argon atmosphere) - proceeds between: o C (isothermal) - is affected by restraining impact of formed char; which decays when its concentration drops to 15% and lower

20 CONCLUSIONS (IV): From 850 C, the char serves as a source of carbon for carbothermic reduction of remaining ZnO, which evaporates from solid residue in metallic form (completed at 950 C)

21 CONCLUSIONS (V): The presence of 5 vol % of oxygen has no significant effect on: - bromination of ZnO - vaporization of formed ZnBr 2 - carbothermic reduction of ZnO The strong oxidizing conditions (20 vol % of oxygen): - has no significant effect on bromination of ZnO; - prevents carbothermic reduction of remaining ZnO - boosts vaporization of ZnBr 2 together with amplifying influence on char degradation (vaporization of ZnBr 2 completed at 550 o C 80 min)

22 Details on the research can be found in: Environ. Sci. Technol. 2009, 43(23), Environ. Sci. Technol. 2009, 43(4), J. Anal. Appl. Pyrolysis. 2010, 88, Thank you for your kind attention!

23 Additional Slides

24 Schematic of the Differential Scanning Calorimeter 2920 Differential Scanning Calorimeter DSC 2920 [ TA Instrument, New Castle, DE, 1997 ] [TA Instrument, New Castle, DE, 1997] DSC EXPERIMENTAL CONDITION Samples: mixture of TBBPA + M x O y at stoichiometric mass ratio Sample s amount: 10 mg Experimental condition: - Hermetic aluminum alodined pan - Heating range: ºC - Heating rate: 1 C/min - Argon flow: 50 ml/min

25 Analytical procedure Solid Residue Filter Condensed phase Distilled water Hexane 20 mg sample: - Before heating - After heating C sample of filter + condensed phase Samples 420, 550 C only Sample 420 C only Extraction IC (Br - ) GC-MS TBBPA d. p. Dist. water (100 ml) Mag stirrer (1h) 0.05M HCl (100 ml) Mag stirrer (1-3h) Dist. water (100 ml) US bath (3h) IC (Br - ) ICP (Zn + ) Temp. ~25 C Temp. ~70 C Temp C ZnBr 2 0.1M HCl (100 ml) ICP IC (Br - ) ICP (Zn + ) ICP US bath(1h) Temp. ~50 C total Zn + ZnBr 2 total Zn + Hexane (20 ml) GC-MS (only 420, 550 C) TBBPA d. p.

26 RESULTS: DSC curves for ZnO, TBBPA and TBBPA:ZnO (3.34:1) at a heating rate of 1 C/min T MAX = 272 C TBBPA+ZnO Heat flow [W/g] TBBPA Ref: Luda et al., 2003: T Melt = C 267 C ZnO + 2HBr ZnBr 2 + H 2 O ΔH r = J/g 260 C decomposition intensifies 308 C leak of HBr ZnO Temperature [ C]

27 RESULTS: SL 50μm Zn 50μm EPMA pictures Br 50μm O 50μm XRD patterns of solid residues from thermal treatment of TBBPA:ZnO (3.34:1) by DSC at 272 o C.

28 RESULTS: Isothermal treatment of TBBPA:ZnO (3.34:1) for 40 min 80 (%) Zn bromination Br release Zn (ZnBr2) vaporized Zn and Br distribution (%) during thermal treatment of TBBPA:ZnO (3.34:1) % Temperature( C) Fate of Bromine and Zinc at various temperature [%] Temp. Released Br Brominated Zn for total Zn Time (min) Vaporized Zn for Brominated Zn Zn loss Unreacted Br for released Br C % % % % %

29 RESULTS: Isothermal treatment of TBBPA:ZnO (3.34:1) for min 80 Zn bromination rate (%) C 270 C 290 C 310 C Zn bromination rate (%) during thermal treatment of TBBPA:ZnO (3.34:1) Fate of Bromine and Zinc for various conditions (%) Temp. Time Released Br Brominated Zn Vaporized Zn Zn loss Unreacted Br Time (min) for total Zn for Brominated Zn for released Br C min % % % % %

30 RESULTS: Effect of ZnO on degradation of TBBPA TBBPA (Barontini et al., 2004) TBBPA:ZnO (3.34:1) (This study) Degradation products no qualitative difference Released Br (Max, %) 52 (270 C) ( C) 63 (250 C) 64 (310 C) 75 (800 C) 77 (900 C) 81 (950 C) Char (%) 20 (when conversion of TBBPA completed) 20 (310 C) 34 (250 C) 32 (270 C) (290 C) (310 C) (490 C)

31 RESULTS: Effect inert and oxidizing conditions on vaporization of zinc during thermal treatment of TBBPA:ZnO (3.34:1) for 40 min 100 Argon 5% Oxygen 20% Oxygen 30 Zn (Total) Vaporization [%] Char [%] Zn (ZnBr2) for brominated Zn Zn (ZnBr2) for total Zn Zn (Metallic) for total Zn Char * ** 650* ** ** Temperature [ o C] The temperatures marked by asterisks indicate different time of thermal treatment: single asterisk - 10 min.; double asterisks - 80 min.

32 Bromination and vaporization of zinc during isothermal treatment of TBBPA and ZnO at various conditions, expressed as percentages. Argo n 5% Oxy gen 20% Oxy gen Tem p. Time Released Br / Br bounded to Zn for Br released Brominated Zn for total Zn Vapor pressure # of ZnBr 2 Vaporized Zn (ZnBr 2 ) for brominated Zn/total Zn Vaporized Zn (metallic) for remaining/tot al Zn Vaporize d Zn (total) for total Zn C min % % Pa % % % % / / 5 0 / / , / 19 0 / / / 29 0 / / , / 17 0 / / / 47 0 / / / 53 0 / / , / 57 0 / / , / 54 0 / / , / 53 4 / / ,287, / / / ,903, / / / , / 18 0 / / / 45 0 / , / / 48 0 / / , / 51 0 / / , / 54 0 / / ,903, / / / / 31 0 / , / / 46 0 / / / 50 0 / , / / 56 0 / Zn loss Char