Authored by Dr. K.B. Nagashanmugam, Dy Manager, R&D Center

1. PROMOTING EARLY DEVOLATILISATION OF COKING COALS TO IMPROVE CRI & CSR PROPERTIES OF COKE WHILST USING UPTO 22% OF NON-COKING COALS IN THE COAL BLEND Authored by Dr. K.B. Nagashanmugam, Dy Manager, R&D Center Shri. M.S. Pillai, Associate Vice-President (Iron complex) Shri. J.M. Sathaye, Executive Director (Works) Presented by J.M. Sathaye

2. O.P. JINDAL GROUP – REVENUE - $ 16 BN P R Jindal Sajjan Jindal Ratan Jindal Naveen Jindal Jindal Saw Jindal Stainless Jindal Steel & Power Ltd. Power Steel Infrastructure Others JSW Steel Limited JSW Energy Limited South West Port Limited Cement / Aluminium /IT 2 2

3. JSW STEEL LTD, SALEM WORKS CAPABILITIES • JSW Steel – Salem unit is a special alloy steel division of JSW steel. • It is the largest special steel plant in India with a production capacity of 1 MTPA. • All the steel grades are manufactured by BF-EOF-LF-VD route. • JSW Strength – Innovation. • JSW vision – to become world class special steel manufacturer. 3 3

4. JSW STEEL LTD, SALEMMANUFACTURING FACILITIES • Coke Oven plant - 0.5 MTPA capacity • Sinter Plant 1 - 20 Sq.Mtr • Sinter Plant 2 - 90 Sq.Mtr • Blast Furnace 1 with PCI - 402 Cu.M • Blast Furnace 2 with PCI - 550 Cu.M • Energy Optimizing Furnace 1 - 45 MT • Energy Optimizing Furnace 2 - 65 MT • Ladle Furnace - 4 Nos - 45 / 65 MT • Vacuum Degassing Unit - 2 Nos - 45 / 65 MT • Billet / bloom caster - 2 Nos. • Bar & Wire Rod Mill - 1 No. • Blooming/HV Mill - 1 No. • Air Separation Plants - 150 T & 390 T per day • Captive Power Generation - (2 x 30 + 7) MW 4 4

5. JSW STEEL LTD, SALEM WORKS COKE OVEN PLANTSTAMP CHARGED, ENERGY RECOVERY COKE OVENS • CAPACITY - 0.5 MTPA • NO. OF OVENS-120 • COAL CHARGE CAKE-50 T • BD – 1.10 - 1.15 T/M3 • POWER GENERATION THROUGH WHRB – 30MW • COMMISSIONED DURING 2007-2008. 5 5

6. HOW TO IMPROVE COKE CSR • Known methods are: • Improving the usage of high quality coking coal in the blend. • Increasing the Bulk Density of coal blend. • Increasing the rate of carbonization by increasing the coking temperature. . . . iv. Lower porosity 6 6

7. POROSITY OF COKE • Porosity depends on coal properties like rank, type, size, fluidity, carbonisation process etc. • During carbonisation, Porosity in coke is created by gas bubbles trapped in the semi-coke and arises from the path left by gases. • Hence, if most of the volatile gases are made to leave when the coal is highly fluid, then the resultant coke would be less porous. • It is known that, a less porous coke exhibits a better hot strength properties than a highly porous one. 7 7

8. COAL DEVOLATILISATION STUDY • Coal devolatilisation is a complex process in which coal is transformed at elevated temperatures to produce gases, tar and char. • No standard apparatus for studying the quantum and rates of devolatilisation of coals was available. • RDI & RI apparatus meant for sinter and iron ore analysis was modified and used for the above. 8 8

9. APPARATUS FOR THE DETERMINATION OF DEVOLATILISATION OF COALS 9 9

10. PROCEDURE FOR STUDY OF DEVOLATILISATION • A sample of 500 grams of coal is taken in the retort and heated gradually under inert atmosphere of nitrogen (to avoid oxidation) from room temperature to 950oC. • The coal is soaked for two hours at each of the following temperature intervals viz. 300, 350, 400, 450, 500, 550, 600, 700, 800, 900 and 950oC to mimic process in non-recovery ovens. • The weighing device continuously records the loss in weight of coal. • The loss in weight corresponds to the amount of volatiles removed. 10

11. ADVANTAGE OF EARLY DEVOLATILISATION • As per the results, for most coals, though the significant devolatilisation starts at 450oC, it is maximum only at the temperature range of 550-700oC. • For most coking coals, the fluidity temperature range lies between 375-550oC. • Hence, by some means, if these coals are made to devolatilise early at temperature range at which the coal is fluid, then most gases would escape when the coal is fluid, which in turn should result in coke with improved porosity. 11 11

12. REPRESENTATION OF EARLY DEVOLATILISATION TO IMPROVE COKE QUALITY

13. EARLY DEVOLATILISATION OF COALS WITH CATALYSTS • Devolatilisation studies were conducted initially using combustion catalysts (used elsewhere) with available coals. • Certain chemical compounds (in PPM levels) were found to promote early devolatilisation of coking coals in the fluidity range. • The above findings revealed that, there exists potential to improve coke properties by using these catalysts. 13 13

14. DEVOLATILISATION BEHAVIOUR OF CHIPANGA MOZAMBIQUE (HARD COKING COAL) 14 14

15. DEVOLATILISATION CURVE OF CHIPANGA MOZAMBIQUE 15 15

16. QUANTUM OF DEVOLATILISATION CURVE OF CHIPANGA MOZAMBIQUE 16 16

17. DEVOLATILISATION BEHAVIOUR OF GREGORY (SEMI-HARD COKING COAL) 17 17

18. DEVOLATILISATION CURVE OF GREGORY COAL 18 18

19. QUANTUM OF DEVOLATILISATION CURVE OF GREGORY COAL 19 19

20. DEVOLATILISATION BEHAVIOUR OF ANTHRACITE (NON-COKING COAL) 20 20

21. DEVOLATILISATION CURVE OF ANTHRACITE 21 21

22. QUANTUM OF DEVOLATILISATION CURVE OF ANTHRACITE 22 22

23. CATALYTIC DEVOLATILISATION AND EXPECTED IMPROVEMENT IN COKE PROPERTIES • The addition of catalyst to coal blend in coke ovens should lead to • the production of coke superior to the one it would have produced in its absence. • to confirm this phenomenon, “Salem box tests” were conducted by using these coals. 23 23

24. SALEM BOX TEST • Procedure: The coal samples are collected and crushed to below 3 mm size and are mixed in the required proportion to prepare the coal blend and required quantity of demineralised water is added to it to maintain approximately 10% moisture and is then homogenized by manual mixing. • This coal blend is filled inside a mild steel or stainless steel box (size 240mm x 240mm x 240mm and thickness 10mm) in 3 to 4 increments and stamped with a metal stamper till 16 kg of coal blend is compacted. • Now the box is ready for carbonization. It is then placed inside a coke oven by removing a portion of coal cake at the center of its width to accommodate the box. • The box is then placed in that place for carbonization along with coal cake. After carbonization, the box is removed and the contents were analysed for coke properties (Patent application filed in India). 24 24

25. RESULTS OF SALEM BOX TEST 25 25

26. BULK CARBONISATION IN COKE OVENS • In order to confirm these results in bulk production of coke, addition of catalysts to coal blends was performed in actual coke ovens. • Initially, the trials were conducted in selected ovens and the catalysts were added to coal blends in stamping station as illustrated in the schematic diagram. 26 26

27. BULK TEST RESULTS 27 27

28. MICUM AND POROSITY IN COKE 28 28

29. RESULTS OF BULK MANUFACTURING WITH CATALYSTS • It is possible to mix selective catalysts with coal blends containing increased percentage of inferior non-coking coals (upto 22%) in coke making and still produce coke with required CRI and CSR values. • The process reduces the carbonization time by about 2 hrs as compared to conventional coke making process without the use of catalysts • The application of catalyst helps in reducing the porosity of coke, resulting in the reduction in moisture adsorption. • Thus, economic benefit was derived from these trials and the technology is now in practical application at JSW Steel Limited, Salem Works. 29 29

30. CONCLUSION • Early devolatilisation in presence of catalyst is observed in almost all the coals analysed. • The process of devolatilisation can be speeded up and made to happen at the temperature range when coal is fluid. • Peak height and peak shift in quantum of devolatilisation curves clearly indicate the catalytic action of chemical compounds in increasing the rate of devolatilisation at lower temperatures. • Coke produced with the addition of catalysts was found to be comparatively less porous than the one produced in their absence. Water adsorption capacity test also supported this observation. • Thus the addition of catalysts makes possible the utilisation of upto 22% of non-coking coals in coal blend for the successful mass production of metallurgical coke leading to a reduction in cost per ton of coke. • Now, the values are consistent at CRI < 25% and CSR > 65% when compared with earlier values of CRI 24-28% and CSR 58-68%. 30 30

31. SCOPE FOR FUTURE WORK • It is still not clear, how these chemical compounds exert their catalytic action inside the softened coal cake during carbonization. • Further studies are being conducted to propose a suitable mechanism for their catalytic action. 31 31

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