Alternative reducing agents Bio-coke

Transcription

1 Alternative reducing agents Bio-coke Nordic Recycling Day VIII September 2017 Luleå University of Technology Maria Lundgren, Swerea MEFOS AB

2 Outline Why bio-coke? Problems/challenges Bio mass (bio-coal) used in the study Carbonisation tests in technical- and semi-industrial scale RFCS-CT FLEXCOKE and CAMM Coke yield & wall pressure Cold & hot strength Method for small scale laboratory carbonisation Laboratory scale bio-coke with larger amounts of bio-coal addition With and without pre-treated bio-coal Part of European regional development project Bio4Metals and CAMM 2

3 Why bio-coke? EU 2030 Energy Strategy targets to reduce greenhouse gas emissions by 40% increase the share of renewable energy and energy efficiency to at least 27% by 2030 Increased interest using renewable biomass in general and also as part of coking coal blends CO2 neutral and the availability is sufficient in many regions High impact on green CO2 emissions du to large amount of coke in the BF 3

4 Problems/challenges Although bio mass/bio-coal has low ash content High content of lime and alkalis catalysing the solution loss reaction effecting bio-coke reactivity and strength after reaction Canada research of hardwood charcoal into the coking coal blend indicated a limitation of 5% addition The addition was 5% in technical scale bio-coke lowered in semi-industrial scale tests CRI CSR T. MacPhee et.al. Possible CO2 mitigation via addition of charcoal to coking coal blends, Fuel Processing Technology, 90 (2009) p

5 Problems/challenges Low bulk density of bio-coal large volumes in wt.% addition Pre-treatment in some way are needed for larger amounts if bio-coal addition to the coking coal blend Pre-treatment with HV coking coal with high fluidity used in laboratory scale bio-coke carbonisation tests aim to increase bulk density of the blend and to cover the reactive bio-coal particles 5

6 Bio-coals (a) (b) (c) (d) Bio-coal Ash K VM (%) C (%) CaO* (%) 2 O* Fe 2 O 3 * P* (%) SiO 2/Al 2 O 3 (%) (%) (%) * Charcoal (a) Torrefied wood high temp. (b) Torrefied wood medium temp. (c) Torrefied saw dust (d) VM= Volatile matter. *Compound in ash 6

7 Technical- and semi-industrial scale carbonisation tests at DMT D. Gajic et. Al. New Findings from the DMT Small-Scale Coking Test Retort Regarding Coke Quality and Coke Oven Wall Safety, AisTech 2012 conf. proc., Atlanta USA, p kg retort 500 kg semi-industrial coke oven with movable walls Standardised coke tests as cold strength and CRI/CSR are made 7

8 Bio-coke yield & wall pressure Coke yield larger than reference coke with charcoal addition Quite safe wall pressures with bio-coke production 8

9 Cold strength, Micum & IRSID 9

10 CRI (Coke Reactivity Index) CSR (Coke Strength after Reaction 10

11 Laboratory coke making method Thermocouple 1 Thermocouple 2 N2 tube (8 L/min) 70 mm 210 mm 220 mm 70 mm Graphite crucible Coal mix (0.8 g/cm3) Tamman furnace at LTU Coking coal bed of same bulk density as SSAB 2 thermocouples, one inside the coal bed Inert carbonisation for around 4 h 11

12 Laboratory coke making method Reference coke; 40% LV, 32% MV & 28% HV coking coal provided by SSAB Similar: Temperature profiles in comparison of retort test Mass losses in TGA Reaction rates comparable 12

13 Laboratory scale bio-coke with larger amounts of bio-coal addition Pre-treatment of torrefied wood saw dust TW SD HV coking coal Tamman furnace ~ HV coal softening temp. Pre-treated material Reported here Blends with 50 wt. % torrefied sawdust and 50 wt. % HV coal 13

14 Laboratory scale bio-coke with larger amounts of bio-coal addition Sample No. LV MV HV TW SD Pre-treated TW SD Bulk density (kg/m 3 ) Coke yield (wt. %) Bl1. Ref blend Bl2. 5% TW SD Bl3. 10% TW SD Bl4. 10% pre-tr. TW SD (14.5*) Bl6. 20% pre-tr. TW SD (21.8*) LV: low volatile MV: medium volatile HV: high volatile TW SD: Torrefied wood sawdust 14

15 TGA evaluation of coke reaction kinetics Solution loss: CC cccccccc + CCCC 2 (gg) 2CCCC(gg) Arrhenius equation: llllll aa = EE aa RRRR + llllll Apparent reaction rate: ρρ aa = 1 WW dddd dddd [gg -1 s -1 ] 15

16 Bio-coke Gasification in TG Start of reaction temperature, C-conversion Reaction rate, (ρ a ), g/gs 3,0E-05 2,5E-05 2,0E-05 1,5E-05 1,0E-05 5,0E-06 Bl1.ref B2.5% TSW Bl3.10% TSW Bl4.10% TSW1 Bl6.20% TSW1 10% Pre-tr. TW SD 20% Pre-tr. TW SD 5% TW SD 10% TW SD Ref 0,0E Temperature, C Coke Temperature, C Ref 910 5% TW SD % TW SD % Pre-tr. TW SD % Pre-tr. TW SD 860 Coke C- conv. (%) 1100 C Ref % TW SD % TW SD % Pre-tr. TW SD % Pre-tr. TW SD 28.2 Higher start of reaction temperature for pre-tr. TW SD than only 10% TW SD addition More tests needed for final conclusions 16

17 Conclusions Safe carbonisation parameters for bio-coke for additions of 5% or less Charcoal increase coke yield Bio-coke has lower cold and hot strength and higher reactivity compared to high quality reference coke Lower addition lower impact Charcoal seem to be best alterative regarding reactivity and hot strength Torrefied wood indicated to be best alterative regarding cold strength Coke & bio-coke successfully carbonised in laboratory Pre-treatment of bio-coal with HV coking coal have positive effect on bulk density and coke yield Difficulty to see clear trends for coating, reactivity etc. more test needed RFCS project application submitted for extended research in the area 17

18 Thank you for your attention! Questions? 18

19 19 Scientific Work for Industrial Use