Emission Free Coke Oven Doors

134 Coking Coals and Coke Making: Challenges and Opportunities

Eco–Friendly Coke OvenDoor – A Measure toMinimize Gas Emmissionfrom Coke Oven Doors

C.S.N. Sastry, C.P. Gupta and Rajeev Kumar

A B S T R A C T

The recent boom in world coke production suggests a multifold increase in greenhouse gasemissions from coke oven doors worldwide. By the end of 2010, the world will have an annualcoking capacity of approximately 433 million tons, which corresponds to 167,700 tons of globalwarming gas (CO2 equivalent) emission annually. This paper discusses the philosophy ofproviding perfect gas sealing in coke oven doors and also discusses the satisfactory results obtainedat Bhilai Steel Plant of Steel Authority of India Limited and elsewhere.

Keywords: Coke Ovens, Environment, Coke Oven Doors, Gas Emissions, Sealing

INTRODUCTION

Concerns on environmental issues are getting more and more serious worldwide. Regulationsfor coking facilities have become more stringent than ever in every country. Non-recoverycoke oven batteries may be a choice for this issue, however, considering the huge investmentsrequired to replace all existing batteries by non-recovery batteries, this choice may not befeasible. Investigations on the sources of gas emissions from existing coke batteries havenot showed any promising results in meeting the regulations and the most difficult butprobable counter-measure is to eliminate gas emissions from around coke oven doors. Itseems gas emissions from coke oven doors are still a matter of headache. In this paper, the

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Eco–Friendly Coke Oven Door – A Measure to Minimize Gas Emmission from Coke Oven Doors 135

sealing capabilities of coke oven doors and requirements for perfect gas emission preventionand report on successful results obtained at Bhilai Steel Plant (BSP) of Steel Authority ofIndia Limited (SAIL) and elsewhere have been discussed.

EMISSION FREE COKE OVENS

Coke Ovens (CO) Complex of BSP has been constantly striving to minimize the emissionsfrom coke oven doors of the coke batteries. The coke oven collective had earlier tried differentdesign of doors and different methods of door regulation to reduce gas emissions. Duringthe last 5 years, the gas leakage measured in PLD (Percentage Leaking Doors) has beencontrolled below 10 per cent level with the use of asbestos ropes for sealing.

However, the continued efforts to reduce the door leakages below 5 per cent with thistechnology seemed to be a herculean task. The Central Pollution Control Board (CPCB) ofIndia has fixed a norm of below 10 per cent PLD for a running old battery and maximum of5 per cent PLD for a new battery.

In Battery No. 3 of BSP, all the doors have been replaced with air cooled self sealingdoors of improvised IKIO design supplied by M/S Simplex Castings Limited, Bhilai. Withthis innovation the dream of achieving gas leakage of less than 1 per cent has been realizedand further efforts are being made to achieve totally emission free batteries.

This is a significant achievement, particularly, for a working battery. Following the abovesuccess, with replacement of the present doors in the remaining batteries of BSP with newIkio Design Simplex Doors, the day of achieving emission free Coke Ovens is not far away,thus contributing to the reduction of global warming.

Fig. 1 Battery No. 3 door emission – before and after installation of air cooled doors


Battery No. 3 of BSP (Start-up year- 1962, Rebuilt- 1990, Cold Repairs- 2007, Height 4.3m., 65 Ovens of Russian Design) started the conversion of existing doors to “Air Cooled SelfSealing Type Ikio-Simplex Doors” in the 1st week of April, 2008 and finished worked in the 1st

week of August 2008. Fig. 1 shows the remarkable improvement in gas emission index (GEI)of CPCB, India along with the progress of door replacements. Fig. 2 shows a currentphotograph of BSP’s Battery No. 3 with practically negligible emission.

Fig. 2 BSP’s No. 3 Battery after door replacement

M/S. Simplex Castings Ltd., Bhilai entered into a Technical Collaboration in the year1988 with M/S. Ikio Iron Works, Japan for making Emission Free Self Regulating AirCooled Doors.

Coke Ovens is the area where maximum pollution is generated. Generally, ConventionalType Coke Oven Doors are being used in Coke Oven Batteries, which are prone to heavyleakage of hazardous gases, flames, heat and dust. Due to these reasons, Coke Ovens Complexis considered as an unpreffered area to work, where workmen are exposed to pollutionresulting in low productivity. This is the main concern of all steel plants today.

Top managements of steel plants world over are concerned about pollution and workingconditions at Coke Oven Complexes and are continuously trying to improve the design ofCoke Oven Doors. M/S. Simplex Castings Ltd., Bhilai being a leading manufacturer ofCoke Oven Doors as per customer’s drawings and specifications, also realized the gravityof this problem, studied the adverse impact in-depth in consultation with users, designersand in-house studies. Various types of coke oven doors used world wide by different CokeOven Plants, posed the question of its suitability in design to meet the present environmental


norms, and after detailed study, M/S Simplex came up with “Emission Free Self RegulatingAir Cooled Coke Oven Doors” which here after are referred to simply as “Simplex Doors.”

ADVANTAGES OF EMISSION FREE SELF REGULATING AIRCOOLED COKE OVEN DOORS OF IKIO-SIMPLEX DESIGN

• Emission free• Zero emission of fire between door frame and doors, PS and CS and leveler door

window• Very less coke fall from Ovens• Door regulation is very simple and doors are user friendly for doormen and door car

operators• Maintenance of the doors is very simple• Self sealing and regulation by springs (spring steel)• Diaphragm with Knife (stainless steel sheet and high tensile flat)• Refractory material made of silica bricks having 40% alumina content• Fibre packing made of ceramic fibre sheet, containing alumina, silica and zirconia,

which can withstand operating temperatures of the level of 1050 °C continuously• The door does not rest on the oven sole; instead it is hung from the door frame

hanging bracket. Hence, the door is free for automatic regulation of the DiaphragmKnife for self sealing by springs when the temperature rises to 1050°C

• Brick retainers are of cut back design. Provision of brick compartments of 5 to 6 Nos.for easy circulation of hot air inside the chamber, so that while circulating, gas pressureon Diaphragm Knife is less and coal tar deposits on sealing surface and door framesealing face is practically negligible

• It is recommended to incorporate the door along with the door frame to maintainsurface contact of knife with sealing surface of the frame.

• High output of coke oven gas• Production of coke of high and uniform quality with optimum yield of by-products• The environment remains pollution-free

Tata Steel at its Jamshedpur Works has replaced all its existing doors with Ikio-SimplexDoors in the following batteries:

• Battery No. 7, start up 1989, height 4.5 m., OTFU, 54 ovens converted from originalcoke oven doors to IKIO-SIMPLEX Doors in 1991;

• Battery No. 5 start up 1995, height 4.5 m., OTFU, 30 ovens;• Battery No. 6, start up 1993, height 4.5m., OTFU, 60 ovens;• Battery No. 8, start up 1998, height 4.5 m., OTFU, 70 ovens;• Battery No. 9, start up 2000, height 4.5 m., OTFU, 70 ovens.


All its batteries have achieved the PLD within environmental norms.Durgapur Steel Plant at its COB # 6 (height 4.45 m., OTFU, 39 ovens) has also converted

10 doors to the new Ikio-Simplex design.Among the various international coke companies, at Lucchini-Piombino Coke Battery,

Ikio-Simplex Doors were installed during start up in June 2002 in the new battery, height 6.2m., number of ovens 45; at SMS-Demag built Al-Nasar Coke Company, for producing Coke& Chemicals at El-Tabbin, Helwan, Egypt, Ikio-Simplex Doors were installed in the 5.0m.tall Battery No.3, start up in 1978, 65 ovens, BVR type, No. of doors replaced - 25 in 2007.

Recently, Rashtriya Ispat Nigam Ltd. ( RINL ), Vishakhapatnam, COB #4; ISP, SAIL,Burnpur, COB # 10; Rourkela Steel Plant, SAIL, COB # 4; Bokaro Steel Plant, SAIL, COB #1& 2; Jindal Stainless Steel, Jajpur, COB # 1, have all gone ahead for Ikio-Simplex doorsbased on the recommendations of Mecon Limited and Centre for Engineering ( CET ), SAIL,Ranchi.

Ikio-Simplex doors are under operation in many advanced countries like Nippon SteelCorporation ( NSC ), JFE ( Formerly NKK & Kawasaki Steel Corporations ), Arcelor Mittal,Battery No. 1 & 2 at Aviles COB, Imasa, Spain, China Steel Corporation, Taiwan etc. and allare working satisfactorily for more than a decade.

From the above evidences, sealing capability of Ikio-Simplex coke oven doors has beenclearly established. For monitoring of gas emissions, five (5) week rolling average of GEI isto be used in order to observe the trend of gas emission behaviour. Every coke plant alwayshas to keep this rolling average below 10.

CONDITIONS FOR MAINTAINING GEI WITHIN NORMS

It is required to fulfill the following four conditions in order to keep GEI within a favourablerange. If any of these, is not satisfied, there will be no perfect results because these fourconditions are closely interlinked with each other.

The results obtained at BSP are the examples that fulfilled these four conditions, whichare shown below:

Condition 1 : Good DoorCondition 2 : Good Door FrameCondition 3 : Good CleanersCondition 4 : Good Maintenance

Coke Oven Doors

Roughly speaking there are two types of coke oven door body. One is a box shaped bodyrepresented by the Wolf type door and the other is a skeleton shaped air cooled door (ACD)body that originated from a Japanese engineer K. Yamasaki in 1974, when the ACD was firstput into service. Later, this door became famous worldwide by the name of “IKIO DOOR”.


Yamasaki invented this door while working for Ikio Iron Works, Japan, as Manager of DoorDevelopment and Manufacturing. His innovation was to separate door body and plugmounted sealing unit thermally, by providing skeleton type door body, which does notreceive heat from the coking chamber directly. Table 1, shows the differences between Wolfdoor and ACD. Complete separation of body and diaphragm functions for ACD is the mainreason for the above mentioned difference. In the design of ACD, in order to minimizethermal and mechanical bending of the door body, air gap was provided between door bodyand sealing unit and at the time, enough rigidity was given to door body to enable it tomaintain its straightness while coping with the counter force generated by plunger springs.

Table 1. Differences between Wolf Door and Air Cooled Door (ACD)

Type of Door Thermal Bending Sealing Unit (Diaphragm)of Door Body

Wolf Large Attached to door body directly. Receivesinfluence of thermal bending of door directly.Fitting ability to the deformed door jamb is poor.

Air Cooled Negligible or small Well isolated from door body thermally. ReceivesDoor (ACD) no influence of bending of door due to the very

small door body thermal bending.Free from influence caused by difference ofthermal expansion between door body anddiaphragm. High adjustability against doorjamb deformation.

Thanks to this design, the relative position of door and door jamb is kept unchanged allthe way and the flexible sealing unit can always keep good contact with door jamb sealingsurface. Thus, the roles of door body and sealing unit are clearly separated in the ACDdesign philosophy. Since the time “Ikio door” came into the world market, many doors withskeleton bodies appeared, but those doors, which had no distinct design philosophy,disappeared soon and only doors with rigid bodies and flexible diaphragms have survived.

Progress in ACD Design

The first ACD Ikio door soon became famous worldwide with its better sealing capabilitycompared to existing knock seal type doors because of its easy adjustment to fit knife edgeto the door jamb.

Many of the door manufacturers of the world have been supplying their products withplungers and skeleton body since then. Some of those are supplying under the license ofIkio Iron Works, Japan.


Kesao Yamasaki established his own company, Yamasaki Industries Co. Ltd. (YIC),Japan in 1984 and added many improvements to ACD later. Table 2 given below, shows thetypical structural progress in ACD design.

Table 2. Typical Structural Progress in ACD Design

Generation Manufacturer Body Cross Diaphragm Sealing Unit Sealing UnitSection Cross Section Bending Exchange or

Replacement

1st Generation Ikio “U” shape Convex or Not available Full1974 Corporation Flat Disassembling

after 1993

2nd Generation YIC after “H” shape Flat Provided Full1991 1995 Disassembling

3rd Generation YIC “H” Shape Flat Provided CartridgeBlue Sky

Major changes in ACD design are as follows:

1. Cross section of door body was changed from “U” shape to “H” shape, to improvetorsional rigidity by increasing section modulus.

2. Cross section of diaphragm was changed from convex to flat, because convexdiaphragm was not flexible enough, especially at door corners and as a result, fittingcapability of knife edge to door jamb was poor.

3. New function was added to the 2nd generation design. This was to bend diaphragmalong its length to provide better fitting of knife-edge to door jamb, which generallyhas considerable differential bowing on both sides of jamb frame.It does not take much man-power to make bending adjustments. Therefore,combination fixing of doors on ovens are not necessary.

4. The diaphragm should be replaced by a new one, after several years of service. In caseof 1st and 2nd generation designs, disassembling of all sealing parts was necessary forreplacement. To reduce manpower for replacement work, 3rd generation designintroduced cartridge type sealing unit. Disassembly became no longer necessary. Totaltime required for cartridge replacement is not longer than 5 hours with two well-trained workers. The door maintained complete sealing capability, entirely similar tothe new door, only by replacing the cartridge.

By adding the above mentioned improvements to older type ACD, 3rd GenerationACD has been accepted as the most reliable door in the market presently.


Comparison of 3rd Generation ACD with Wolf Type Door

Major advantages of 3rd generation ACD over Wolf type doors are as follows:

Thermal Bowing of Door Body

Temperature differences within a door body cause thermal bowing. Wolf type door showsthe difference as much as 120°C. On the other hand, the difference is as low as 40°C in caseof 3rd generation ACD. Bowing of Wolf type door body is easily influenced by the change ofambient temperature. Therefore, it is impossible to maintain good sealing always.

Fitting Ability to Deformed Door Jamb

Allowable door jamb bowing range for 3rd generation ACD is 20 to 25 mm. in total. Althoughthis range varies due to the actual prevailing conditions, it is much larger than that of Wolftype doors.

Maximum Allowable Gas Pressure

When a battery operates with wet coal charge, the peak gas pressure at the bottom part ofdiaphragm ranges from 150 to 300 millibar. Wolf type doors may require a lot of manpowerto cope with this peak pressure in order to maintain operation without gas emissions.

Blue Sky door keeps good sealing performance even when the gas peak pressure rises upto 2000 mm WC. This peak is generally observed when a battery operates under coal moisturecontrol system.

TYPICAL EXAMPLES OF EMISSION FREE COKE OVENS

Coke Oven Battery No.1 at Sakaide Works of Mitsubishi Chemical Corporation, Japan(Start-up: Nov.1969, Height: 6 m, Otto Design, 100 Ovens) started the replacement of itsexisting doors with the most advanced Air Cooled Doors (ACD) named “Blue-Sky” in April1999 and completed the work in May 2000. Fig. 3 shows a remarkable improvement in gasemission index (GEI) along with progress in door replacement.

Like Sakaide Works, Nippon Steel’s Oita Works also replaced their original coke ovendoors with Blue Sky Doors for all its batteries (Battery Nos.1 and 2, Start-up: 1972, Height:5.925 m, NSC Type, 156 Ovens; Battery Nos. 3 and 4, Start-up: 1976, Height: 6.092 m, NSCType, 164 ovens) and have achieved similar results. From these evidences, excellent sealingcapability of Blue Sky Door has been clearly proven with respect to operation of “emissionfree coke ovens”. At Sakaide Works, following the success experienced at Battery No. 1,recently Battery Nos. 2 and 3 ( Battery No.2, Start-up:1971, Height: 6.9 m, Carl Still Design,100 Ovens; Battery No. 3, Start-up: 1973, Height: 6.9 m Carl Still Design, 123 ovens) also hadtheir earlier doors replaced with Blue Sky Doors.


Fig. 3 Mitsubishi Sakaide No.1 Battery after doors replacement

DOOR JAMB

Bowing of Door Jamb

It is obvious that when the bowing of door jamb exceeds a certain allowable limit, we arenot able to prevent gas emission, even if we use doors with good sealing ability. However,there has hardly been any technical paper, which elaborately discusses about the relationshipbetween gas emission and door jamb bowing. Discussions about gas emissions in the past,pointed out only sealing capability of the door itself as a subject. Fig. 3 shows an exampleof a door jamb bowing measured at an existing battery in operation. There is an obviousdifference in bowing between right and left frame of a door jamb. This difference is notstrange for most of the existing batteries in operation. At Sakaide’s Battery No.1, we madebowing measurements for some number of door jambs selected by random sampling, priorto door replacement. The results showed that, bowing of all tested jambs was within anacceptable range. Then the new jambs were manufactured to replace existing old door jambswith the design similar to the original Battery No. 1 doors, which were replaced by Blue SkyDoors, without providing specially designed door jambs at all.


Prior to replacement of doors of Battery Nos. 2 and 3 at Sakaide Works, we measuredbowing of all door jambs in all the three batteries, because we found jamb bowing at BatteryNos. 2 and 3 as worse compared to that at Battery No.1. Fig. 4 shows the measurementresults. The “d” in Fig. 4 corresponds to the maximum bowing showed in Fig. 5. Fig. 5shows that more than 70% of total jambs have bowing beyond the limit that Blue Sky Doorscan accept. We have not clearly understood the exact reason why there is such an exaggerateddifference in door jamb bowing between Battery No.1 and Battery Nos. 2 and 3. The onlyplausible reason at the moment seems to be the difference in battery designs of Otto andCarl Still.

Replacement of Door Jamb

In order to achieve an emission free environment, we provided special shaped door jambs,for which the bowing is shown in Fig. 4. The back of these jambs had proper contours bywhich jambs could make good contact with the deformed brickwork face, behind the jambs.The jambs with contoured back sat on the deformed brickwork correctly.

Cases where this consideration is paid for jamb replacement.Once door jamb replacement is executed under above mentioned consideration, gas

emission due to door jamb distortion would not happen for many veary because brickworkdistortion does not progress rapidly.

Fig. 4 Door jamb bowing Fig. 5 Door jamb bowing at Sakaide Nos. 2 and 3 Batteries


If the new jambs had been manufactured as per the original design, then the result ofjamb setting on deformed brickwork would have varied geometrically from one to another.In other words, the new jamb would not give sealing face parallel to knife edge plane. As aresult, inspite of jamb replacement, perfect gas emission free environment would not berealized. It seems to us, there are few cases where this consideration is taken into account forjamb replacement.

Once door jamb replacement is executed under the above mentioned consideration, gasemissions due to door jamb distortion would not happen for many years because brickworkdistortion does not progress rapidly.

Good cleaning of door and door jamb is a must for emission free battery operation. Thetype of cleaners should be discussed in combination with the type of doors.

Door Cleaners

Generally speaking, there are two types of door cleaners. One is the mechanical type and theother is the high-pressure water jet type. The majority of cleaners are of mechanical typewith wire brush or scraper for cleaner head. This type of door cleaners, inspite of manymodifications, has some weak points. Firstly, it cannot remove deposits on the knife-edgetip and secondly, it imparts considerable strong force on the door diaphragm and in orderto counter the force imparted by cleaner heads, we lose flexibility of the diaphragm, which ismost crucial for sealing function.

High pressure water jet cleaner is friendlier towards the flexible diaphragm used forACD type doors because this cleaner does not make direct mechanical contact with thediaphragm. Some coke plants say that, they do not like this type of cleaner because a part ofthe cleaning water falls down onto the battery platform and creates secondary environmentalproblems. However, when water pressure higher than 500 to 600 bars is applied, then therequired quantity of cleaning water is too small to make any impact while falling down ontothe battery platform. Excess water evaporates quickly before it reaches the battery platform.

Advantage of high pressure water jet cleaner over mechanical cleaner is that, the formercan clean not only the diaphragm but also knife-edge tip without damaging them. The lattercannot deal with knife-edge tip with such a delicate contact. High pressure water jet cleaneris most favourable for ACD type doors.

Door Jamb Cleaner

Only mechanical cleaners have been put into service worldwide. It is the shortcomingcommon to these cleaners that they damage the jamb sealing surface while their cleanerheads are working.

Knife-edge sealing face of Yamasaki’s ACD - Blue Sky Doors is machined by speciallydesigned high precision planer to ensure that it provides perfect contact with the door jamb


sealing face. If the door jamb sealing face is not in good condition, complete gas sealingcannot be expected. Already, Yamasaki is in a position to supply high pressure water jet typejamb cleaners.

Cleaner for Jamb Inside Surface

Some times, we see carbonaceous deposits on the lower part of jamb inside surface. Whenthis deposit grows up, door may not go to the right position because door plug is blockedby the deposit. Deposit removal work today, relies only on manual operation. Although thisissue is not related directly to gas emission, we must not leave the matter as it is, when wethink about a pollution free working environment.

MAINTENANCE ASPECTS

Door

The diaphragm life of Blue Sky Doors has exceeded 7 years at Nippon Steel Corporation’sOita Works. Periodical off-line maintenance for each door is recommended. Main items ofthis maintenance are change of worn plunger springs, careful visual check-up of the projectionpiece of leveler door protector and manual removal of carbon deposit residuals on the doordiaphragm with the help of high pressure water jet. Stationary cleaning facilities for carbondeposit residuals removal play a very important role for maintaining an emission freeenvironment for long. If one tries to stop gas emissions, leaving the carbon deposits as it is,by tightening plunger screw beyond a limit to increase pressing force onto the knife-edge,there will be permanent deformation of the diaphragm and/or knife edge. Once this occurs,the cartridge will have to be replaced by a new one.

Door Cleaner

When water jet nozzle tips get worn out and increase their hole diameter, the water pressuremay decrease leading to a fall in the cleaning efficiency. Nozzle tips have to be kept in goodcondition at every moment.

Movement of nozzle head should always be appropriately adjusted so as to cover allareas of the diaphragm and knife-edge. Condition of wire brush or scraper of mechanicalcleaner is crucial. Conditions of the equipment have to be maintained at their best in orderto perform to their full potential. Adhesion of tar to wire brushes will cause loss of cleaningeffect within a short period. Deformation of scraper will damage the diaphragm extensivelyand cause gas emission.


Door Jamb Cleaner

When carbonaceous deposits left on the sealing face of door jamb grows up and forms hardscab, the knife-edge cannot have direct contact with the jamb sealing face in this area. Theknife-edge and diaphragm of this area will start distorting gradually and finally cause gasemission. The only way to avoid this undesirable situation is to always maintain the doorjamb cleaner in good condition.

M/S. Simplex Castings Ltd., Bhilai has entered into a technical collaboration with M/S.Yamasaki Industries Co. Ltd., Japan in the year 2007, for manufacturing Blue Sky Doors.

CONCLUSIONS

• Results obtained at Coke Ovens Complex of Bhilai Steel Plant (SAIL) has proved thatcomplete prevention of gas emission from around the coke oven door area is possiblewith the use of ACD doors made of Ikio-Simplex design.

• Results obtained at Mitsubishi Chemical Corporation’s Sakaide Works and NipponSteel Corporation’s Oita Works has proved that complete prevention of gas emissionfrom around coke oven door area is possible with the use of Blue Sky Doors.

• By replacing damaged door jambs and applying high sealing performance ACDs,even a battery older than 18 years can be revived for perfect gas tightness.

• To fulfill the four required conditions, such as good door, good door jamb, goodcleaner and good maintenance, one has to have correct knowledge and understandingabout coke oven doors because this the right path to long lasting emission freeenvironment surrounding the coke oven door area.

ACKNOWLEDGEMENTS

The authors would like to express their special thanks to all senior executives of the CokeOvens & Coal Chemicals Department of Bhilai Steel Plant (SAIL) who directly or indirectlycontributed to the successful implementation of ACD doors of Ikio-Simplex design for anemission free environment.

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13. Patent Pending.