Development of Diagnosis and Repair Methodology for Coke Oven Chamber wall for a
Battery more than Forty Years in Operation
at TATA STEEL Jamshedpur works .
B.D.Pandey , Asim Biswas , Avijit Mukherjee , Asis Kumar Sarkar & Prakhar Mishra
Abstract :
The role of coke ovens in an Integrated steel plant is pivotal , the overall profitability and productivity depends
largely on the enhancing the life span of a coke oven battery . For this, close maintenance at right time is the
only way to reduce any premature failure of batteries .In an Integrated steel plant , productivity and
profitability depends largely on enhancing the life of span of a coke oven Battery by following preventive
maintenance practices in proper times and strict Operation discipline .Coke oven Battery #3 has the unique
distinction of being first Battery in India to last for 40 years . Coke oven Battery #3 came into operation on June
11 , 1940 . It was pulled down in 1958 and re-built, increasing its number of ovens from 55 to 57 ovens . The
second phase of this Battery extended till 1975 , when it was re- built again for phase 3 and was running
successful till October 2014 The coke plant , considered to be the mother of an integrated steel plant as it not
only supplies coke to Iron making units , but also provides coke oven gas as required for other units of steel
plant . Tata Steel has truly shown the way that, with commitment and Innovation, it is possible in India also to
enhance the life of coke ovens . Battery #3 was consist of 27 ovens each in two block & could carbonize about
1450 mt of coal daily with a rated production of capacity of 1000 mt of Blast furnace grade coke per day .
Recent practices revolve around the regular inspection of the ovens in proper schedule followed by various
jobs so as to stop cross leakage of raw gas to vertical flues , ensuring proper and uniform heating and also
maintaining desired oven top condition . Battery anchorage and thrust on the wall by checking the spring
conditions , maintaining the silica bricks temp , oven sole proper shape and gap between jamb bricks and
backstays . Recent practices to keep the battery heath Oven Inspection in conventional method and thru flue
by means of Camera was in vogue on regular basis and prediction of life in years and condition of ovens in 15 scale was started , depending on the oven inspection special pointing , dry gunniting , Ceramic welding of
Silica and fireclay bricks from ovens door /charging lids and thru flues after inspection thru endoscopic
camera was started .Apart from conventional dusting of silica powder , Liquid sol of micron size activated
silica dissolved in organic solution has been injected in ovens to fill up gap of micro crack , cavities and holes
and other damages and encouraging results of cross leakage reduction has been observed .
Key Words : Cross Leakage ,Anchorage , Ceramic Welding , Liquid Dusting , Dry Guniting ,
Introduction
A coke oven battery is basically constructed by silica bricks .During operation, severe thermal shocks and
thermo mechanical stress act on this silica brick work which is highly susceptible to this shock and bricks work
condition start deteriorating as a result . So after commissioning as the time passes on the performance index
of battery takes a down ward tendency slowly and steadily . But the deterioration suddenly accelerated
sharply and needs for uncalled for capital repair become immediate .This situation caused lot of capital
investment . Thus the profitable and productive operation is terminated. This explains the need for
preventative maintenance and routine repair of coke oven battery in time .
Various stress acting on silica bricks during initials heating, Commissioning and during operation of a coke oven
battery are as follows .
1. Thermal stress arising due to the presence of residual quartz and other specific feature of silica bricks
used for construction.
2. Dynamic stress due to movement of pusher car ram in the ovens .
3. Dynamic load due to the movement of charging car .
4. Transverse stress due to the swelling pressure of coal during carbonization .
5. Thermal stress due to the charging of moist coal.
6. Thermal stress arising due the door opening and closing.
7. Stress arising due to the dead load of refractory bricks works and structural elements .
8. Frequent change in the blend of coal / power failure and thermal regime .
9. Sticker formation /Resistive Pushing
The above mentioned stress are unavoidable bound to happen in the running battery as these are the feature
of operation process .Moreover ,technological violation in pushing cycle , sticker formation , violation in
heating regime and violation in the operation and maintenance standard practices make the situation worse .
The present status of Battery of TATA STEEL Jamshedpur are as follows .
Battery No Year of Commissioning Nos of Ovens Capasity [MTPA]
3
1975
27x2
0.3
5
1995
30x1
0.2
6
1993
30x2
0.4
7
1989
27x2
0.4
8
1998
70x1
0.5
9
2000
70x1
0.5
10
2012
44x2
0.7
11
2014
44x2
0.7
Type
Avg Width/Taper Height
top charge
400/60
4500
stamp charge
460/20
4550
stamp charge
460/20
4550
stamp charge
460/20
4550
stamp charge
460/20
4570
stamp charge
460/20
4570
stamp charge
564/40
5000
stamp charge
564/40
5000
DIAGONOSIS OF DEFECTS IN OVEN AND FOR REPAIR PLAN OF COKE OVENS
A Inspection of Ovens
Proper inspection and close monitoring followed by timely repairing action taken will go a long way in
enhancing battery life . Much stress has been given on the inspection and battery life prediction by
oven health inspection system .In TATA STEEL oven wall both high wall and low wall , oven sole are
being inspected in an interval 3 months from coke side , ram side and charging/suctions Lids of oven
top .But for seriously damaged ovens , inspection frequency is much more , even after every pushing .
The inspection report are documented monthly in report and expected life is predicted from
inspection ranking and preventive action plan based on the inspection report .
The Inspection report are entered in the special log book Having diagram course and flue wise both
from Coke side and Ram side . The ovens are inspected from both coke side and Ram side and defects
are mapped in the given bellow sheet .
B
JOBS DONE TO PREVENT THE CROSS LEAKAGE
1. Conventional Dusting and Liquid Dusting
Cross leakage of raw coke oven gas from oven carbonization chamber to vertical flue may take place
if there is crack in the heating wall .This may produce crack and produce graphite in the vertical flues
and air /gas ports creating resistance to the path of heating gas . The raw gas may also burn inside
the sole flue canal and gas – air valve area causing severe damages . Heating regime is adversely
disturbed due to this cross leakages . Moreover , stack emission and suspended particulate matter
[ spm] levels goes above pollution control norm
The root cause the cross leakages is opening of joints in the Silica bricks works and formation of
micro cracks in the wall , which may be due to bad workmanship , thermal stress and ageing of the
wall and undercut . To prevent the cross leakages conventional dusting and liquid dusting process
was adopted on regular basis to seal off micro cracks ,when the cavities and major cracks was there
ceramic welding process was adopted . Stack smoking gets reduced considerable after completion of
dusting in the ovens .
2 Ceramic welding
In TATA STEEL ceramic welding process started from the year 2002 , In this process in situ sintering followed
by formation of ceramic bonding of repair mass with the affected area of silica / fireclay brick work . During the
welding process the spot temp shoots up to 2200 deg c in the area of repair . ceramic welding process is very
effective for filling the bigger cavity and joints between old and new bricks joints ,Before ceramic welding
process surface are prepared by removing loose materials from the surface of cracks for proper adherence of
welding materials . The chemistry of mother bricks and welding should match flawless surface.
Based on the oven inspection priority list of ovens which is to be take up fortnightly in the battery which are in
operation more than 20 /25 /35 years are prepared .For middle flues of ovens water cooled lances are used
for ceramic welding in the effective way . For ceramic welding thru the flues lance scope camera are used for
detection of location of crack and welding was done in a controlled way with minimum amount of rebound loss
and the result was encouraging .
C JOBS DONE TO MAINTAIN THE REFRACTORY WORK PROPER
1
Changing of oven sole bricks .
Silica sole bricks, if damaged are replaced by High Alumina quality bricks and phosphate bonded mortar are
used to filling up the joints . This type of repair works takes in general 4 to 5 hour by controlling the both side
heating wall temperature and soaking time is to be given 6 to 8 hours . The pusher ram is passed in the empty
ovens to check the oven sole levels. After checking the oven sole level final clearance for charging is to be
given. Newly repair oven sole is rechecked after the first pushing.
2 End Flue / Full wall repair
Depending on the nature of damage decision taken for end flue / full wall repair . The end flue are
subjected to spalling due to frequent door opening for long duration . It has been found that near to
door area are very susceptible to damage after continuous operation of 15- 20 years . In general end
flue upto 4th flue , 6th flue and 8th flue repair done depending on the degree of damaged in a particular
zone of coke side or Ram Side depending on the Refractory condition. Full wall repair decision taken if
the nature of damaged is irreparable by end flue technique . In general the full wall repair done by
controlling the two adjacent heating wall temp above 700 deg c + and two oven are empty and next
two ovens are kept under longer carbonization time [ may be above 25 hours with respect to normal
coking time 19 hours ] To Support the wall proper jacks of adjustable nature used for correct position
of adjacent heating wall and the spring length are checked for proper thrust on the wall .In general 3
to 4 full heating wall repaired in 50 to 55 working days including heating period .
3
Anchor maintenance
Anchors are used for correct positioning of the oven wall. it is the nature of silica bricks to expand
throughout its life span . It is a dynamic process the position of the wall tends to expands in the both
side over every year and hence the importance of anchorage is there to resist the movement of the
wall and by adjusting the thrust . In every Battery once in every three month all the spring loading
are checked with Torque Range and Bending tendency of Backstays are checked with plump and
reported in a particular format . Every three month it is being reviewed and operation efficiency are
being judged with the number of spring damaged / replaced . The decision of Backstays which is bow
in nature and replaced and there are two dedicated groups who are working throughout the year
regulate the Buckstays movement and reported in a particular format where all the data are captured
like .
a] Spring Load/ length measurement [ Earlier campaign / this campaign / difference / total damaged
spring which length could not be adjusted .
b] Gap Between Buck Stays and the Flush Plate
c] Condition of rope packing between Flash Plate and Door Frame .
d] Verticality of Buck Stay
e] Tie Road locking status
f] Back to Back distance Measurement of Buck stays
g] Condition of bricks work above the door / Mat bricks /Linton bricks
4
Door & Door Frame inspection .
All the Oven Machine in Stamping Charging Pushing(SCP) Car/ Coke Guide Car are equipped with High
pressure water jet door cleaning system and Frame cleaning Arrangement . All the door are self-sealing
type door with Stainless steel Knife edge . In door conventional type fire clay , Cordierites type Bricks
and Mono block PCPF shapes in 5 Segments are used . Door Frame , Door Body , Gap in between
Pressure Bolt and Door Frame , Refractory work , Spring Lengths are checked and reported on monthly
basis .
5
Ascension Pipe( AP) Inspection /Isolation Valve /Tie Rod Changing .
On regular basis the base/ shell temp of AP are taken to monitor the health of AP . Sometime cake
breakage and operational problem may leads to AP Base jamming and ISO Valve jamming . Time to
time check has improved the life of ISO Valves and AP .
E
JOBS DONE TO ENSURE PROPER HEATING AND TEMPERATURE REGIME
1 Regenerator face wall pointing and plastering
5
6
7
8
9
F
2 Caulking with ceramic ropes in the waste heat box base and reducer , Door frame
3 Airing of checker chamber for maintaining proper vertical top pressure
4 Regulation of waste heat box/ finger plate for adjustment VTP and AIR / Gas ratio.
Adjustment of Damper in chimney tunnel /waste heat box for control temp regime .
Dry guniting of ovens ,
Silica Patch repair / Special Pointing , .
Regenerator face wall repair
Oven Tope repair / reline of clinker bricks and maintaining the slope
Conclusion
The properties of the bricks change with the oven age and number of through openings increase in the
chamber walls , Faced with this problem TATA STEEL , has developed methods of diagnosis oven inside and the
Flue Inside with lance scope camera to detect the actual course / position of the crack and repair immediately .
A second approach is liquid dusting and Flame gunning and ceramic welding to improve the wall condition.
Third option is end flue and full wall in running battery without affecting the production and detaining the
campaign repair and enhancing the battery life . By following the strict operating discipline , heating regime
control , timely regulation of all parameters which affect the combustion , draft and timely maintenance it
is possible to enhance the Battery life span of Battery .
References
Internal documents of TATA STEEL, JSR COKE PLANT