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Injection of BF flue dust into the BF - a full-scale test at BF No. 3 in Luleå

Injection of BF flue dust into the BF - a full-scale test at BF No. 3 in Luleå. Introduction Practical aspects Mixing flue dust and coal Wear Process evaluation Summary Future work. Topics. BF no 3. Dedusting of BF gas. Cyclone + wet scrubber 35 000 tonnes dry BF-dust

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Injection of BF flue dust into the BF - a full-scale test at BF No. 3 in Luleå

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  1. Injection of BF flue dust into the BF - a full-scale test at BF No. 3 in Luleå

  2. Introduction Practical aspects Mixing flue dust and coal Wear Process evaluation Summary Future work Topics

  3. BF no 3

  4. Dedusting of BF gas • Cyclone + wet scrubber • 35 000 tonnes dry BF-dust • 10 000 tonnes of sludge

  5. PCI-plant

  6. Composition of briquettes BF dust Filter dust Pre-mix of steel scrap, desulphurisation scrap and BOF sludge (coarse particles) Water Cement BF-dust reduces the strength of the briquettes A briquette without fluedust reaches the same strength after 4 days of curing as a fluedust containing briquette after 3 - 4 weeks Briquettes

  7. Screen analyses of flue dust and coal

  8. Chemical analyses of flue dust and coal

  9. Blending flue dust and coal at the stockyard Mixing flue dust and coal powder in the fine coal silo of the injection plant Mixing flue dust and coal powder just in front of tuyeres (not tried at SSAB) Methods for addition

  10. Blendning at coal yard Coal Coal + Flue dust Coal + Flue dust + Coal Raw coal hopper 900 t Coal + 100 t Flue dust

  11. Uneven distribution of coal and BF-dust Dustemissions during handling Increased pressure drop over filter Increased vibrations in grinding equipment Loss of capacity in grinding equipment Wear in pipes and lances Blendning at coal yard

  12. Fine coal silo Coal-85 BF No.3 Fine coal silo Coal-98 BF dust • 100% BF dust • 10% BF dust • 90% PC Screening Injection vessels Coal-85 Injection vessels Coal-98 32 tuyeres Distributor Mixing of coal powder and BF-dust in fine coal silo Cyclone BF No. 3

  13. + Improved accuracy + No loss of capacity in the grinding equipment + No problem with pressure drop over filter Wear in pipes and lances Mixing of coal powder and BF-dust in fine coal silo

  14. Wear problem in injection lances outer inner

  15. Wear problem in injection lances outer inner

  16. Consequence of wear in an injection lance

  17. Process evaluation • Gas efficiency – normal variations • Fuel rate – normal variations • Gas distribution – normal variations • Si – normal variations • S – slightly improved • Productivity – no change

  18. Si in hot metal, comparison between experimental BF and BF no 3 • Raceway is a large part of the total cross section in the EBF => => Higher SiO-generation • The influence of iron oxide and oxygene partial pressure on raceway conditions is more pronounced in the EBF • Effects of residual FeO • - desiliconisation Si +2(FeO) ⇄ SiO2 +2Fe • - consumption of char and coke fines • - decreased melting point of tuyere slag

  19. BF flue dust is an extremly abrasive material Mixing of BF flue dust and coal powder as late as possible No process problem during injection Problems related to wear Summary

  20. Suitable pneumatic transport system Best option for mixing Minimize wear in pipes and lances Future work

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