Injection of bf flue dust into the bf a full scale test at bf no 3 in lule
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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 lule

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


Topics

Introduction

Practical aspects

Mixing flue dust and coal

Wear

Process evaluation

Summary

Future work

Topics



Dedusting of bf gas
Dedusting of BF gas

  • Cyclone + wet scrubber

  • 35 000 tonnes dry BF-dust

  • 10 000 tonnes of sludge



Briquettes

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




Methods for addition

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


Blendning at coal yard
Blendning at coal yard

Coal

Coal + Flue dust

Coal + Flue dust + Coal

Raw coal hopper

900 t Coal + 100 t Flue dust


Blendning at coal yard1

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


Mixing of coal powder and bf dust in fine coal silo

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


Mixing of coal powder and bf dust in fine coal silo1

+ 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




Consequence of wear in an injection lance
Consequence of wear in an injection lance


Process evaluation
Process evaluation

  • Gas efficiency – normal variations

  • Fuel rate – normal variations

  • Gas distribution – normal variations

  • Si – normal variations

  • S – slightly improved

  • Productivity – no change


Si in hot metal comparison between experimental bf and bf no 3
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


Summary

BF flue dust is an extremly abrasive material experimental BF and BF no 3

Mixing of BF flue dust and coal powder as late as possible

No process problem during injection

Problems related to wear

Summary


Future work

Suitable pneumatic transport system experimental BF and BF no 3

Best option for mixing

Minimize wear in pipes and lances

Future work


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