Metals in Biorefineries :

Transcription

1 The Forest Based Biorefinery: Chemical and Engineering Challenges and Opportunities (5cr) Metals in Biorefineries : Ari Ivaska Process Chemistry Centre Åbo Akademi University

2 Why are metals of importance? It is important to understand the natural existence and distribution of metal ions in tree material and the reactions of the metal ions with wood fibres and other chemicals in different stages of the paper making process and in the energy conversion processes.

3 The reasons to study Chemical forms of metals in wood, pulp and process liquors varies from metal to metal Study on metals gives important information to predict their behavior in different parts of paper making and energy conversion processes as well as their environmental impact.

4 Objectives Effects of metals on: Flows, Balances, Processes and products Metals in wood= metals in fuels Important to understand because of: Fouling of equipment (K, Ca, Si) Corrosion of hot heat transfer surfaces (K, Zn, Pb) Emission (EU directive for heavy metals: As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Tl, Sb, V)

5 Metals are important for the growth of the tree and excist as natural components in tree material Elemental distribution of different concentration ranges for stem wood of Scots pine (Pinus sylvestris) tree Concentration range, ppm (mg/kg) Elements Ca, K, Mg F, Fe, Mn, Na, P, S 10 1 Al, B, Si, Sr, Zn, Ti Ag, Ba, Cd, Cr, Cu, Ni, Rb, Sn Bi, Br, Ce, Co, I, La, Li, Pb, Se, W As, Eu, Gd, Hf, Hg, Mo, Nd, Pr, Sc, Sb Elements in red are from the EU list of dirty dozen.

6 Metals in wood are significant! Knots Chem. pulping & bleaching Chips Recovery Fillers Al Ink Bark Biofuel refining Mech. pulping & bleaching DIP Paper Metals in soil Effluents Mech. forest products Ash

7 Metal management is important Environmental effects Knots Chips Chem. pulping & bleaching Recovery Degradation of bleaching agents Fillers Al Ink Soil pollution Metals in soil Bark Biofuel refining Mech. forest products Corrosion Deposits Ash utilisation Ash Mech. pulping & bleaching Effluents DIP Paper Effects on fibre properties and adverse effects in food packaging

8 Kraft Pulp Mill & Biorefinery WP5 pulping chemicals paper pulp WP3 recycling WP5 round wood harvesting residues WP6 WP5 pulping chemicals WP5 stemwood debarking bark extraction WP 4 P WP combustion gasification chipping knots P extraction WP8 heat chips extraction P emissions emissions ash & WP1 power synthesis gas pulping black liquor separation biofuels (l) synthesis P WP5 P P WP2

9 Characterization of biofuel

10 Chemical fractionation all major ash elements H 2 O ammonium acetate Analysis alkali sulfates/ carbonates, chlorides exchangeable some CaCO 3 HCl carbonates, sulfates silicates, insoluble rest

11 Objective to investigate the forms of metal binding in Scandinavian wood-fuels by sorption of a color dye step-wise leaching in H 2 O, NH 4 Ac and HCl element analyzes of the leachates ion-chromatography of the leachates potentiometric titration of the pure biomass from tree samples

12 Metals associated with fuel matrix M + - OOC- - -COO -COO - M 2+ -COO - -COO - M 2+ Johan Werkelin, Maria Zevenhoven

13 Major Ash Forming Matter in Fuels Water soluble ash-forming matter Included minerals Organically associated ash forming matter Excluded minerals COO - COO - K + COO - Ca 2+ Minor ash forming matter, -COO - Na + heavy metals?

14 Main Ash-forming Matter Rest fraction, analysed Leached in HCl Leached in Acetate Leached in H2O for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 Si Al Fe Ti Mn Ca Mg P Na K Maria Zevenhoven mg/kg d.s

15 Heavy Metals (EDD12+Zn) Rest fraction, analysed Leached in HCl Leached in Acetate Leached in H2O 0 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 for res. wood1 wood2 As Cd Co Cr Cu Hg Mn Ni Pb Sb Tl V Zn Maria Zevenhoven mg/kg d.s.

16 Johan Werkelin Ash Elements in Spruce

17 Balance for Pine wood, bark & foliage Johan Werkelin

18 Conclusion Metal binding in trees was determined Metals: in wood: in bark: in foliage: as salts 5 10% 5 10% 10 30% anionic gr 80 90% 20 50% 20 50% as oxalate 0 10% 20 50% 10 40% Chemical mode of ash-forming elements influence ash chemistry and deposit formation Johan Werkelin

19 Metals in wood

20 Sampling for microanalysis N W E Latewood Earlywood S Wood discs from 2 meters height of a ~40- year-old Norway spruce tree were used. Annual growth rings in different compass direction One annual growth ring Microtoming Andrey Pranovich

21 Scheme used for chemical microanalysis of wood samples Wood Microtoming Thin sections (0.125 m) Extraction GC (Extractives) Acid methanolysis AcBr method THM GC UV-spectrometry GC-MS Hemicelluloses Lignin content Lignin structure Pectin ICP-MS Metals Andrey Pranovich

22 Annual growth ring Earlywood Latewood Thin wood sections Analysis Distribution of analytes within annual growth ring sugars from hemicelluloses, uronic acids lignin Andrey Pranovich metals

23 1994 WEST Annual growth ring Earlywood Latewood mg/kg wood mm Ca K Na

24 Metal content in spruce stemwood (average from 1989 and 1994 annual growth rings across the stem) Mn 2,2% Ba 1,1% Zn 0,7% Al 0,7% Sr 0,4% Fe 0,3% Cu 0,1% Rb 0,1% K 29,1% Mg 7,5% Na 6,9% Other 0,07 % Pb 0,02 % Cr 0,01 % Ni 0,03 % Co 0,01 % Cd 0,002% Ca 50,9% Andrey Pranovich

25 Binding of metal ions to wood fibres

26 Ion-exchange equilibria in wood fibres COO - H + COO - H + M + HR MR + H + + COO - H + COO - H + COO - H + COO - M + + M + + H + M COO - H + COO - H + K H MRH M HR COO - H + COO - H + COO - H + COO - H + COO - M2+ COO - + M H + COO - H + COO - H + 2 M 2HR MR2 2H K 2 MR M 2 H 2H 2 2 M HR

27 Ion-exchange equilibria in wood fibres COO - M + COO - M + COO - M + COO - N + N + MR NR + M + + COO - M + COO - M + + N + COO - M + COO - M + + M + K M N NRM N MR COO - M + COO - M + COO - M + COO - M + + X 2+ COO - X 2+ COO - COO - M + COO - M + + 2M + 2 X 2MR XR2 2M K 2 XR X 2 M 2M 2 2 X MR

28 Determination of stoichiometry of the ion exchange reaction ph:4-10 log K Ca nk Ca - nk n M M log K Mg nk Mg - nk n M M

29 The column chromatographic method Step 1 Column packing Step 2 Removal of natural ion content Step 3 Loading of pulp and rinsing Step 4 Elution of metal ions Pulp 8 g or 18 g -EDTA - HNO 3 - Deionized water - Metal ion mixtures - Deionized water M HNO 3 65 cm and 120 cm Determination of metal ion concentrations in the fractions 20 mm Naturally contained metal ions Excess of metal ions (not bound) 5 ml Collection of fractions (bound metal ions) Pingping Su, Kim Granholm

30 Study on metal ion affinities to oxygen delignified hardwood kraft pulp by a column chromatographic method Procedure: A column (65 2 cm and cm) packed with pulp Natural ion content removal (EDTA, HNO 3 ) and a rinsing with deionized water Addition of mixtures of metal ions (loading) and washing away the excess (unbound) of metal ions with deionized water Elution of metal ions with M HNO 3 Collection of fractions (5 or 10 ml) during elution Determination of metal-ion concentrrations in the fractions

31 n, mol 10 ph Mg 2+ 4 ph V, ml Fig. 1. ph and the number of mikromoles (n) of magnesium ions as function of the volume (V) of eluate in the collected fractions. MR n H ( 2) Pingping Su, Kim Granholm HR M n H K M 2H 2 2 HR M MR H 2 2

32 8 n, mol Ba 2+ Ca 2+ Mg 2+ Sr 2+ Mg 2+ Sr 2+ Ba 2+ Ca V, ml Fig. 2. The number of mikromoles (n) of Ba 2+, Ca 2+, Mg 2+ and Sr 2+ as function of the volume (V) of eluate in the collected fractions. Pingping Su, Kim Granholm

33 n, mol 4 2 Fe 2+ Mn 2+ ph 6 4 ph V, ml Fig. 3. ph and the number of mikromoles (n) of Fe 2+ and Mn 2+ as function of the volume (V) of eluate in the collected fractions. Pingping Su, Kim Granholm

34 Redox potential, mv mv ph ph o E Cell =E Cell +59.2mVlog Fe(II) M M= α M(OH) Fe(III) - MOH - n M(OH)n M(OH) M,OH M,nOH α =1+ OH K + + OH K V, ml Fig.4. The redox potential and ph plotted as function of the volume (V) of eluate for the sorption of Fe 2+ and Mn 2+. Fe(III) α Fe 3+ Fe(III) = 2+ Fe(II) Fe(II) α Fe Table 1. Calculation of the Fe 3+ /Fe 2+ ratios from the mean values of the redox potentials and ph from the data presented in fig. 4. Level Redox Potential (mv) ph Fe(III) log Fe(II) Fe(III) (%) Fe(II) (%) α Fe(III)(OH) α Fe(II)(OH) Fe(III) log Fe(II) Fe(III) ~ Pingping Su, Kim Granholm (%) Fe(II) (%)

35 8 6 Fe 3+ Mn 2+ n, mol V, ml Fig. 5. The number of mikromoles (n) of Fe 3+ and Mn 2+ as function of the volume (V) of eluate in the collected fractions. Pingping Su, Kim Granholm

36 25 n, mol Ba 2+ Cd 2+ Cu 2+ Mg 2+ Mn 2+ Na + Pb 2+ Zn 2+ Cu 2+ Pb 2+ 5 Cd 2+ Na V, ml Fig. 6. The number of mikromoles (n) of Ba 2+, Cd 2+, Cu 2+, Mg 2+, Mn 2+, Na +, Pb 2+ and Zn 2+ as functionof the volume (V) of eluate in the collected fractions. Order of affinities to the pulp: Fe 3+ >>Pb 2+ >>Cu 2+ >>Cd 2+ >Zn 2+ >Ba 2+ >Ca 2+ >Mn 2+ >Fe 2+ >Sr 2+ >Mg 2+ >K + >Rb + >Na + Pingping Su, Kim Granholm

37 LA-ICP-MS for element analysis Interface Quadrupole R.F. Generator Ion lense Laser ablation Plasma torch Detector Gas control Amplifier Vacuum pumps MCS Computer

38 Analysis of single wood fiber Pingping Su, Paul Ek

39 Pingping Su, Paul Ek

40 LA-ICP-MS scan along a single wood fiber The distribution of the metals in the single fibre of the unbleached kraft softwood The intensity / cps K Fe Mn Time / s distance, m Pingping Su, Paul Ek

41 Distribution of metal ions in tree

42 Objectives Detailed localisation of metals in different wood species (spruce, aspen, birch, larch) and tissues (sapwood, heartwood, EW, LW) by chemical microscopy Elena Tokareva

43 ToF-SIMS imaging of radial section from spruce sapwood. Total ion Ca Na 100m Mg Fe Lignin Ca, Na, Mg, K, Fe dominate in bordered pit tori. Only little lignin was observed in the same regions. Elena Tokareva

44 LA-ICP-MS of radial section from spruce sapwood Elena Tokareva, Paul Ek

45 Labelling of anionic groups Acid treatment (ph 2, 20 C) Spruce sections No treatment SrCl 2 / MgCl 2 impregnation ToF- SIMS Alkali treatment (ph 12, 60 C) O COO O OH O OH Elena Tokareva OH OH O COOCH 3 O NaOH, t C - CH 3 OH O COO OH O OH O OH COO OH O O

46 ToF-SIMS images Original spruce section Total ion Ca Sr 100 m Total ion Sr 2+ impregnated section Ca Sr Elena Tokareva 100 m

47 Speciation of calcium in black liquor

48 Construction of all-solid-state Ca 2+ ISE (= ion-selective electrode) Glassy carbon PVC PEDOT 1 Ca 2+ cocktail 2 3 Ca 2+ membrane Galvanostatic Electropolymerization: EDOT+ 0.1 M NaPSS ma (0.2mA/cm2), 714 s - Condition in 0.1 M CaCl 2, 24 h Drop-casting: mg ETH 1001,1.62 mg KTpClPB, 3.73 mg ETH 500, 161 mg PVC, 325 mg o-npoe, 3ml THF - Condition in 0.01 M CaCl 2, 24 h 1. Electrosynthesis of poly(3,4-ethylenedioxythiophene) (PEDOT) = electically conducting polymer 2. Drop-casting of Ca 2+ selective cocktail 3. All-solid-state Ca 2+ ISE Kim Granholm

49 Original, evaporated sample, 78% dry matter 3 % dry matter, diluted with water Kim Granholm

50 Durability test of Ca 2+ -ISE in black liquor 48h in black liquor (3.3%) Calibration curves Before black liquor After 48h in black liquor E / mv -80 E / mv time / h -40 Selectivity coefficients log C Ca 2+ / M lg K Ca,Na lg K Ca,K lg K Ca,Mg lg K Ca,Al Before After 48 h Kim Granholm

51 LA-ICP-MS Calcium distrubution at the membrane surface No conditioning After Ca 2+ -conditioning After in black liquor 8.5 mm LA-ICP-MS LA-ICP-MS LA-ICP-MS 0.48 mm Scan rate: 6 µm/s Laser: spot size = 15 µm, effect = 45 %, 5 Hz Kim Granholm

52 LA-ICP-MS Sodium distrubution at the membrane surface No conditioning After Ca 2+ -conditioning After black liquor LA-ICP-MS LA-ICP-MS LA-ICP-MS Scan rate: 6 µm/s Laser: spot size = 15 µm, effect = 45 %, 5 Hz Kim Granholm

53 LA-ICP-MS Depth profile of Calcium in the membrane After Ca 2+ -conditioning After black liquor Membrane thickness: ~200 µm Laser: spot size = 40 µm, effect = 35 %, 5 Hz Kim Granholm

54 LA-ICP-MS Depth profile of Sodium in the membrane After Ca 2+ -conditioning After black liquor Membrane thickness: ~200 µm Laser: spot size = 40 µm, effect = 35 %, 5 hz Kim Granholm

55 Titration of Ca 2+ -solution with EDTA using Ca 2+ ISE (100 ml of 2*10-4 M CaCl mmol Ca 2+ ) Titration curve: Gran s Plot: E / mv M EDTA / ml 10^(E/30) *0.005M = mmol Ca 2+ Linear fit: y= x y=0: x= M EDTA / ml Kim Granholm

56 Potentiometric titrations with EDTA using Ca 2+ -ISE BL (100 ml) -80 E / mv M EDTA / ml Kim Granholm

57 Potentiometric titrations with EDTA using Ca 2+ -ISE BL (100 ml) BL (100 ml) mmol Ca -80 E / mv M EDTA / ml Kim Granholm

58 10 Potentiometric titrations with EDTA using Ca 2+ -ISE (Grans s Plot) *10^(E/30) 6 4 Black liquor Black liquor mmol Ca Kim Granholm Free Ca 2+ FreeTotal Ca 2+ Ca 2+ Total Ca M EDTA / ml

59 1000*10^(E/30) 6 Black liquor Black liquor mmol Ca mmol Free Ca mmol FreeTotal Ca 2+ Ca 2+ Total Ca M EDTA / ml Free Ca 2+ = 0.01 mmol Bound Ca 2+ = 0.01 mmol 0.02 mmol 0.03 mmol Free Ca 2+ = 0.02 mmol Bound Ca 2+ = 0.01 mmol Kim Granholm

60 Conclusions The Ca 2+ -ISE can be conditioned in black liquor to eliminate the potential drift It is possible to measure Ca 2+ ions in diluted black liquors The selectivity coefficients for the Ca 2+ -ISE remains high after black liquor measurments A speciation of complexed Ca 2+ ions and uncomplexed Ca 2+ ions seems to be possible