Stahl-Zentrum. Coke quality parameters versus blast furnace process and hearth performance. Gerard Tijhuis, Luc Bol, Bart van der Velden, Huub Schulte

Transcription

1 Gerard Tijhuis, Luc Bol, Bart van der Velden, Huub Schulte Coke quality parameters versus blast furnace process and hearth performance Together we make the difference

2 Tata Steel Slide 2 Content of presentation Overview of Coke Plants Overview of Blast Furnaces Coke quality and the effect on the blast furnace Our current view on coke quality Concerns for the future

3 Tata Steel Slide 3 Tata Steel IJmuiden Coke Plants Coke plant #1 Coke plant #2 Production: 1.01 Mt 0.87 Mt # of batteries: 6 4 # of ovens: Oven height: 4 m 6.5 m Oven width: 45 & 47 cm 42 cm Year (re)build: Company/design: Didier / Otto Still

4 Tata Steel Slide 4 Coke Plant What is measured? Coke quality KPIs concentrating on the following set: CSR Representative sample of each blending pile (consumed in ~6 days), jointly for both CPs Analysis by external laboratory (DMT), so results reported with some delay Target: 60 < CSR < 70% I10 & I40 (ISO) HMS derived from this At least one sample per Coke Plant per working day, preferably two samples Analysis by own laboratory, results to be reported within 5 days Target: I10 < 21%; I40 = target ± 3% (on 9) or target ± 1% (on 25 samples) Moisture Measured after quenching at Coke Plant, and directly before charging into BF Data immediately available Target: moisture < 5% (but lower limit of 4% in environmental permit)

5 Tata Steel Slide 5 CSR (%) HMS (mm) Coke indices since CSR 30 per. Mov. Avg. (CSR) CSR HMS HMS - CP 1 HMS - CP 2 30 per. Mov. Avg. (HMS - CP 1) 30 per. Mov. Avg. (HMS - CP 2) I10 (%) I10 - CP 1 I10 - CP 2 30 per. Mov. Avg. (I10 - CP 2) 30 per. Mov. Avg. (I10 - CP 1) I10 20 I40 20 I40 (%) I40 - CP 1 I40 - CP 2 30 per. Mov. Avg. (I40 - CP 1) 30 per. Mov. Avg. (I40 - CP 2)

6 Tata Steel Slide 6 Coke I40 20 index since 2002 in more detail I40 (%) I40 - CP 1 I40 - CP 2 30 per. Mov. Avg. (I40 - CP 1) 30 per. Mov. Avg. (I40 - CP 2)

7 Tata Steel Slide 7 Content of presentation Overview of Coke Plants Overview of Blast Furnaces Coke quality and the effect on the blast furnace Our current view on coke quality Concerns for the future

8 Tata Steel Slide 8 Tata Steel IJmuiden Blast Furnaces Blast Furnace 6 Blast Furnace 7 Production 2012: 2.50 Mt HM 3.50 Mt HM Hearth diam.: 11.0 m 13.8 m # of tuyeres: # of tapholes: 3 3 Working volume: 2328 m³ 3775 m³ Last reline: Design : Hoogovens Hoogovens

9 Tata Steel Slide 9 BF performance since 2002 (weekly data and 8 wk mov.avg.) IJmuiden BF6 IJmuiden BF Productivity (thm/24h m³wv) PCI rate (kg/thm) Dry coke rate (kg/thm) IJmuiden BF6 IJmuiden BF Productivity Coke rate (incl. nut coke) Nut coke rate* ) IJmuiden BF7 IJmuiden BF6 PCI rate IJmuiden BF6 IJmuiden BF * ) Nut coke = mm (until ); 8-35 mm (since ) Nut coke rate (kg/thm)

10 Tata Steel Slide 10 Content of presentation Overview of Coke Plants Overview of Blast Furnaces Coke quality and the effect on the blast furnace Our current view on coke quality Concerns for the future

11 Tata Steel Slide 11 Coke quality and its effect on the upper Blast Furnace I40 (%) Productivity (thm/24h m³wv) IJmuiden BF7 I40 - CP 1 I40 - CP 2 30 per. Mov. Avg. (I40 - CP 1) 30 per. Mov. Avg. (I40 - CP 2) IJmuiden BF6 We cannot find a relation. Moreover, high productivity at both BFs in 2007 and early 2008, when the coke I40 and I10 were not very good. It appeared that coke quality was not the top priority in IJmuiden

12 Tata Steel Slide 12 IJmuiden operation and effect on the hearth Both BFs in IJmuiden have limited hearth volume Sump depth according to Vogelpoth near to critical line Focus on high productivity / low coke rate at acceptable coke costs Sitting dead man Strong elephant foot wear AM DK3 HKM A Ta2 Ha9 AM DK2 AM G A val A AM Ta5 IH7 Dil 5 S2 Fos Dil HKM B Ha8 AM B2 PT IJm6 (2002) Ta4 USS G14 AM DK4 SSI S1 IJm7 (2006) BF6 current BF7 current Competitors Coke quality is a critical factor (and a usual suspect)

13 Tata Steel Slide 13 This picture explains it all. Temperature ( C) BF7 - Maximum temperatures in campaign, at 1.7 m and 2.2 m below taphole level Supply issues Australia (market) Below West taphole Below North taphole Ore in the blend Supply, coking time, screens Below South taphole North -1.7 m North -2.2 m South -1.7 m South -2.2 m West -1.7 m South -2.2 m HO7-I40 (7 day avg.) I40 of BF7 coke (%)

14 Tata Steel Slide 14 Residual thickness of the hearth wall BF7 - Residual thickness below the tapholes Residual thickness (mm) I40 of BF7 coke (%) North -1.7 m North -2.2 m South -1.7 m South -2.2 m West -1.7 m West -2.2 m HO7-I40 (7 day avg.) 10 0

15 Tata Steel Slide 15 Content of presentation Overview of Coke Plants Overview of Blast Furnaces Coke quality and the effect on the blast furnace Our current view on coke quality Concerns for the future

16 Tata Steel Slide 16 Decisions taken after these events Better control of I40 at the Coke Plants: Make sure that I40 < 40 incidents are prevented at all times to protect the hearth Improve the regularity at the Coke Plants to get consistent product for each pushed oven Heating of ovens Coke End Temperature Coking time (residence time) pushing scheme Set lower limit of I40 at 43 points for 9 point average to accommodate for natural variation in the coking coal blend and process Focus on constant quality Develop in-line optical PSD measurement for better control of the particle size distribution (under development). Measure, analyse, control! Develop know how on coke texture and its effect on the BF (in progress)

17 Tata Steel Slide 17 Content of presentation Overview of Coke Plants Overview of Blast Furnaces Coke quality and the effect on the blast furnace Our current view on coke quality Concerns for the future

18 Tata Steel Slide 18 Concerns for the future Coke quality is under pressure Prime coking coals are scarce and there is constant pressure on the costs of the coking coal blend. The effect of coke quality on the BF process and campaign life is often circumstantial. Due to big financial impact, coke is an easy target for savings. Cost optimal coke quality Quality Output

19 Tata Steel Slide 19 Concerns for the future Know-how on the behaviour of coke on BF process With core drilling, tuyere raking, and excavation, a lot of information is gathered. But there is still a lot a lot to learn in the field of bosh coke and dead man. There are not many good mineralogists with knowledge on coke. Coke self sufficiency In IJmuiden it is regarded vital to have full control over the coke quality. The focus is to maintain the coke plants in operation to secure sufficient coke. With limited budgets for maintenance, this is also under pressure.

20 Tata Steel Slide 20 Our task as ironmakers: We must defend the coke quality against the attack of the higher management