In this presentation, the coke oven life prolongation technology is reviewed from different points of view: blend design; battery heating; operational control; refractory maintenance. A summary of major inspections in critical areas, for the evaluation of the battery conservation situation is presented. A discussion on tools for the diagnostics of the degree of damage is carried out

1. COKE OVEN LIFE PROLONGATION:
A MULTIDISCIPLINARY APPROACH
Mariano de Córdova, Jorge Madias
ABM Week, Riocentro, Rio de Janeiro, Brazil, August 17th 2015

2. Content
 Introduction
 Coke Battery Life
 Blend Design
 Operating Control
 Refractory Maintenance
 Diagnosis of the Battery State
 Conclusions
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3. Introduction

 Consulting & training for the steel industry
 Technical assistance
 Open, in-company and self-learning courses
 Library services
 Met lab services
 Technical texts for trade journals
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4. Introduction
 Content based on
 Experience of Mariano de Cordova & battery team
while working at Ternium Siderar coke plant
 Material prepared for a short course in San Nicolas,
Argentina, in August 2014 and 2015 (with attendance
of specialists from coke plants in Argentina, Brazil and
Chile)
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5. Introduction
 Factors for longer battery life
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6. Introduction
 Factors for longer
battery life
 Useful life
 After each charge, oven
walls suffer a strong
temperature drop
 This, with other factors,
can decrease resistance to
thermal shock, from 15
years life onwards
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Kasay 2008

7. Introduction
 Factors for longer battery life
 Mechanisms for oven damage
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8. Blend design
 Influence on battery life
 Pressure on walls: cracks, open joints, deformation
 Maximum value: 2 psi
 Industrial values: 0.5 -1.0 psi
 Assessment: Movable wall pilot oven
 Increased by: Higher share of low volatile coal, faster coking rate,
larger charge density
 Charge shrinkage: cracks, open joints, deformation
 Acceptable values: -7 to -15%
 Assessment: Sole-heating Oven Test ASTM D 2014
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9. Blend design
 Influence on battery life
 Ash chemistry: Spalling in some cases
 Assessment: Test of ash penetration on silica brick sample
 Fe2O3 + CaO + MgO must be low
 Stamped charging: Risk of destroying walls
 Extreme case of very high charge density >1000 kg/m3
 Not a problem in non-recovery ovens
 ZKS in Germany, start up in 1984, replacement in 2010 and later by
other stamped charging batteries
 Tata Steel Jamshedpur: battery 7 started-up in 1989, failures since
2005; all ovens recovered by 2010
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10. Battery Heating
 Influence on battery life
 Average battery temperature
 Must be maintained within a range to avoid early damage
 Recommended range: around 1300 ºC to 1100ºC
 Covers the field of stability of tridymite 1470ºC to 870ºC
 Crosswall temperature
 Temperature of flues of a wall, when coking process ends
 Its control is an assessment of thermal homogeneity along the walls
 One series of walls should be measured daily
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11. Battery Heating
 Influence on battery life
 Results show actual
temperature curve and
deviation in comparison
with the standard
 If larger deviations are
detected, inspections and
corrective actions must be
prioritized
 A thermal map can be
built, displaying normal,
cool and hot zones in the
battery
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12. Battery Heating
 Automatic measurement
 Auto-Therm system: optical fibre in pusher ram – Hyundai
Steel
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13. Battery Heating
 Influence on battery life
 Evolution of average deviation, batteries 3/4, Ternium
Siderar
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14. Battery Heating
 Influence on battery life
 Leakage of raw gas
 Leakage through cracks and open joints in the walls, needs to be
controlled periodically
 Leakage damages the wall, decreasing wall temperature and
increasing black emissions by the chimney
 Control: visual inspection of the flues that are not burning, from the
battery roof, during the first five minutes after charging
 Ten points for a large leakage, four for medium and one for small
 Gas leakage index = Total points/(Total of flues x 2)
 Gas leakage index <40 % is acceptable
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15. Battery Heating
 Visual inspection
 Automatic monitoring
system, measuring the
opacity of the off-gas
exiting the stack
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16. Battery Heating
 On line control
 Opacity of every oven charged
 Permitted opacity:
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≤ 40 %

17. Battery Heating
 Vertical temperature
 Difference between upper and lower zones of the charge
 Lower temperature too high: excessive coking, heavy
pushing, reduced coking in the upper part, more fines
 Opposite situation: high temperature in the free space, high
deposition of graphite in wall and roof, heavy pushing
 Reference values: 60ºC for COG, 35ºC for MG
 Adjustment: corrections of O2 in the off-gas
 Some flue designs have several levels of air burning and in
some cases recirculation of off-gas to improve vertical
distribution, mostly in tall batteries
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18. Battery Heating
 Combyflame system: 3 stage of air and off- gas recirculation
 More uniform vertical temperature
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19. Battery Heating
 Vertical temperatura
 Measurement
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Portable pyrometer from
battery top
Pyrometers on guide car
(three levels)
Optical fibre sensor in
pusher ram (three levels)

20. Battery Heating
 Free space temperature
 Temperature between the coal line and the oven roof
 Increases with battery and vertical temperature, and lower
oven charge
 Usually in the order of 800ºC
 If higher, excessive graphite is formed in the walls, thus
generating heavy pushing with risk of wall damage
 To have this temperature in range, the right charging height is
relevant, in agreement with the design of the battery and the
control of O2 in off-gas
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21. Operating Control
 Responsible for thermal and operating uniformity, and for the
control of the operating variables that influence the health of
the battery
 Coking machines
 High reliability and availability
 Emergency equipment and installations
 Effective preventive maintenance
 Delays
 Cycling time (between two pushings) must be constant
 An objective of admissible delays is recommended, as well as
the recording of these delays and their causes, to be able to
reduce them along time
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22. Operating Control
 Pushing regularity (delays)
 SSAB Ruukki Coking Plant,
Finland
 Goal:+6 / - 10min
 Ternium Siderar Coking Plant,
Argentina
 Goal: 0 / - 10 min / oven
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23. Operating Control
 Operating uniformity
 Assessed taking into account the average daily gross coking
time
 The delays and advances in pushing, exceeding the aimed
standard range, are detected and corrected
 When the production level is to be modified, it is
recommendable to change 15 min/day or 5 % of working
index each 5 to 7 days
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24. Operating Control
 Operating uniformity
 Automatric control: schedule, delays, gross coking time
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25. Operating Control
 Evolution of range of gross coking time, Ternium
Siderar
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26. Operating Control
 Thermal uniformity
 Assessed by the range of average daily net coking time,
detecting and correcting the ovens with larger deviation
 Causes for deviation
 Changes in blend moisture
 Changes in charge weight
 Wall temperature variations
 Operating delays or advances
 Gas combustion variations
 Manual or automatic corrections to the heating system using
data of thermocouples in the standpipe
 Semiautomatic adjustment including calorific power of gas;
Wobbe index or complex control loops, including thermal
balance of the battery
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27. Operating Control
 Automatic control system
 Determines the energy for heating the batterie
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Δ Coking time
Energy imput
Δ Pause time
Δ Energy demand

28. Operation Control
 Deviation of net
coking time
(thermal
uniformity),
ArcelorMittal
Tubarão, Brazil
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29. Operating Control
 Control of process variables
 Charge height: Low charge height may imply excessive graphite
deposition and high temperature in the free space
 Controlled by adjustment of charging and leveling operations and
periodical measurements
 Vertical contraction: Too large contraction implies excessive
graphite and high free space temperature
 Oil injection to the blend and decrease in volatile matter are measures
of control
 Pushing force: must be monitored in all ovens, this allows to
identify heavy pushing and to detect blending, heating or
refractory problems.
 Oven internal pressure: It is recommended to eliminate air
ingress that will damage refractories, by means of operating
adjustment or with individual control system of ovens
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30. Refractories
 Ceramic welding
 For hot repairing of oven walls in the long range: cracks, joints, spalling, holes,
patching, Contributes to minimize emission of black smokes.
 Gunning
 Complementary to ceramic welding, to keep sealed the oven walls and reduce
emission of black smoke by the stack by repairing the open joints.
 Dry sealing
 Sealing of very small cracks in the free space of the oven
 Only effective if applied after eliminating major leakages
 Sole maintenance
 Applied to level sole (floor floating), recover worn profile (dry sintering) and
partial reconstruction with new bricks.
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31. Refractories
 Luting
 To seal cracks in the silica ducts transporting coke oven gas to the flues
 Hot repairing of headers
 To make battery life longer for 10 or 20 years more
 Too damaged walls are selected. The first 4 or 6 end flues are rebuilt, including
roof and sole, forming repair group of one to four walls
 Tasks in regenerators, improvements in the roof and bracing system are included
 As a result, there are heating improvements, less raw gas leakages, less heavy
pushing and less emission of black smokes to the stack
 Maintenance of heating system
 Cleaning and changes of the components of the heating system
 Maintenance of doors
 To assess raw gas leakage using EPA or BCRA standards
 Results are useful to avoid air ingress to the ovens
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32. Refractory
 Standpipes and raw gas cooling system
 Cleaning of standpipes, to avoid accumulation of graphite,
making difficult the gas exit and the operation
 Control of flushing liquor nozzles, to avoid ingress to the
oven
 Bracing system
 Control, adjust or change springs
 Inspect buckstays and change them, if necessary
 Thermal imaging is useful for tie rod control, as shown by
DTE Energy
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33. Refractories
 Inspection of battery roof and tie rod in EES Coke batery
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34. Diagnosis
 The method developed by NSC allows to assess the state of
conservation of the battery periodically, taking into account
five index
 Temperature deviation
 Leakage of raw gas through the oven walls
 Crack propagation in walls
 General damage in walls
 Dilatation of refractory structure
 A yearly measurement is recommended
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35. Diagnosis
 Results: Ternium Siderar
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36. Diagnosis
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37. Conclusion
 Right blend, heating practice, good operation and
preventive refractory maintenance all along the life
time of the battery, are keys to a prolonged
battery life
 Hot repairs of headers and diagnostics of damage
are important to achieve this aim
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38. Thank you!
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Mariano de Cordova, Jorge Madias
metallon, San Nicolas, Argentina
mariano.decordova@metallon.com.ar