Appleby Coke Ovens, Scunthorpe by Manoj Sharma This paper was ...

BackgroundIn December 1995 continuous obscuration meters were installed in the 2 coke oven battery stacks.These meters give an indication of poor gas combustion and/or oven leakage. Following theinstallation the EA gave AFCO a daily average consent limit of 60% which stayed in place until June2004 when it was reduced to 50%. This new limit made it difficult to stay in consent and a number ofout of consent reports were submitted to the EA. In 2006 following a significant number of out ofconsent reports an action plan was agreed with the EA to arrest the situation. This action planinvolved significant work in the gas alleys on the gas pipe work, waste gas boxes and air distributionsystem. This work was carried out successfully but did not fully solve the problem and it was agreedin a further action plan to start a project to improve obscuration.The main issues since the start of the whole exercise in 2006 have beeni. Gas pipe work blockages.ii. Carbon build up on the air distribution dussenplatters.iii. Water damaged end flues and air ports.iv. Blocked/broken gas nozzles.The problems identified since the start of the improvement work is listed. Some of these problems,specificallya. Sliding joint missing on 3&4 batteriesb. Access to gas cannons on OSC batteriesc. Collecting main to Conducting main restriction on 3&4 Batteries have not beenactioned to date.Project workA DMAIC methodology has been adopted to carry out the project. In this methodology the variousphases e.g. Define, Measure, Analyse, Implement and Control were carried out.In the Define phase, project charter (Figure – 1) has been prepared which talks about the businesscase, problem statement, goal, in scope, out of scope, deliverables etc.Also it has the system for reviewing the progress based on the plan. The expected financial benefits(tangible or intangible) also indicated on it. Further, to understand the process better SIPOC has beencreated, which talks about supplier (Providers of Inputs to the proces), input (Material, resources, ordata required to execute the process), Process (Collection of activities that takes one or more kinds ofinput and creates output that is of value for the customer), output (the products or services that resultfrom the process) and customer (the recipient of the Process output) and establish a relationshipbetween.

Business Case:Obscuration is a very important parameter for coke ovenbatteries from environmental point of view. It effects thesurrounding environment. If obscuration increases,external complaints started increasing. Running below50% level is a prime factor in license to operate.Problem Statement:In past 12 months average obscuration from stack 1&2was frequently above 50%.Goal:To run the stacks at AFCO below 50% by CY08.In Scope :Heating, minor wall repairs etc.Out of Scope:Major regenerator problem, coal quality, gas quality etc.DeliverablesPROJECT CHARTERTeam Members / Potential Team MembersNameRoleMr. M.K.SharmaMemberMr. Tim BartholomewMemberMr. Nigel WeltonMemberMr. Mick ScarfMemberMr. Simon ClowesMemberMr. Martin KeechMemberMr. Stuart BirdMemberProject StatusProcess Impacted: Coke makingClient(s) Impacted: Environment DepartmentBig Y Impacted: Stack ObscurationProject TimelineStart Date: 10/06/2008 Completion Date: 31/12/2008Phase (Expected) Completion DatesDefine: 10/06/2008Measure: 15/06/2008DMAJun’08 Jul’08 Aug’08 Sep’08 Oct’08 Nov’08ICDec’08EPA compliance of Obscuration (

Process capability of stack1 of AFCODMAICVariable: Obscuration stack 1 Mean: 40.4780Sigma (Total):8.69222 Sigma (Within):3.80441Specifications: LSL=1.00000 Nominal= ---- USL=50.0000Normal: Cp=2.147 Cpk=.8343 Cpl=3.459 Cpu=.8343LSL -3.s(T) USL +3.s(T)100908070Frequency60504030201000 10 20 30 40 50 60 70 80TotalWithinProcess capability of stack 2 of AFCODMAICFrequencyVariable: Obscuration Stack 2 Mean: 51.6044Sigma (Total):6.64802 Sigma (Within):3.80441Specifications: LSL=1.00000 Nominal= ---- USL=50.0000Normal: Cp=2.147 Cpk=-.141 Cpl=4.434 Cpu=-.141LSL -3.s(T) USL +3.s(T)13012011010090807060504030201000 10 20 30 40 50 60 70 80 90TotalWithinFigure – 2

After completing the requirements of Measure phase, the project moved into the Analyse phase. Acause and effect diagram (Figure - 3) was prepared for high obscuration and keeping in mind thethings which are in scope of this project.DMAICDeveloping Cause &Effect Diagram For Obscuration3. Airport Condition 2. Flame ConditionsMissingCarbonCarbonBlockedBroken1.1 CrackHole in the wall1.71.63.21.43.31.51.31.2LooseJammingFusedMaterial3.1ChockedImproperseatingBottom Flue only2.22.3 No burning4.3MajorLeakage4.52.1Excess gasvolumeInadequate air4.1Minorleakage4.2Crack at end fluesCandle light flames4.42.4High StackObscurationEFFECT1.Nozzle condition4.LeakagesCAUSESFigure - 3There were several issues which can impact obscuration but may be out of scope the project. Tounderstand root cause of the problem, a decision was taken to conduct full survey of all(4X33X26=3536) flues of heating walls. The survey was specifically done on four parameters viz.1.Nozzle Condition 2. Airport Condition 3. Flame (Top & Bottom) Condition & 4. Leakages. Theoutcome of the survey was then plotted in graphs (Figure - 4).

NOZZLE CONDITIONSDMAICBatt#1 Nozzle ConditionBatt#2 Nozzle Condition3.172.4937.5648.5313.9194.34Crack Chocked,damaged etc. GoodCrack Chocked,damaged etc. GoodAll Batteries Nozzle Condition15.216.0878.70Crack Chocked,damaged etc. GoodBatt#3 Nozzle ConditionBatt#4 Nozzle Condition5.54 2.7114.593.8591.7481.56Crack Chocked,damaged etc. GoodCrack Chocked,damaged etc. GoodAIRPORT CONDITIONSDMAICBatt#1 Airport ConditionBatt#2 Airport Condition7.244.7592.7695.25Debris etc.GoodDebris etc.GoodAll Batteries Airport Condition7.9292.08Debris etc. GoodBatt#3 Airport ConditionBatt#4 Airport Condition8.7110.9791.2989.03Debris etc.GoodDebris etc.Good

3.93 7.72TOP FLAME CONDITIONSDMAICBatt#1 Flame ConditionBatt#2 Top Flame Condition6.4523.081.8124.4370.4873.76Xs Gas Chocked,no flame etc. GoodXs Gas Chocked,no flame etc. GoodAll Batteries Top Flame Condition3.9329.3366.74Xs Gas Chocked,no flame etc. GoodBatt#3 Top Flame ConditionBatt#4 Top Flame Condition3.513.9632.6937.1063.8058.94Xs Gas Chocked,no flame etc. GoodXs Gas Chocked,no flame etc. GoodBOTTOM FLAME CONDITIONSDMAICBatt#1 Flame ConditionBatt#2 Bottom Flame Condition6.451.81 1.2423.0870.4896.95Xs Gas Chocked,no flame etc. GoodXs Gas Chocked,no flame etc. GoodAll Batteries Bottom Flame Condition88.35Xs Gas Chocked,no flame etc. GoodBatt#3 Bottom Flame ConditionBatt#4 Bottom Flame Condition3.512.383.96 4.1994.1291.86Xs Gas Chocked,no flame etc. GoodXs Gas Chocked,no flame etc. GoodFigure - 4

The conclusions which can be derived by the analysis are:• 15 % nozzles are in cracked condition (live with them) and 6% in bad shape.• 8% of the airports are in bad shape and many of them making the chamber excess in gas.• The excess gases (4%) are the major reasons for high Obscuration.• There are very few (0.28%) leaky flues.• 31% top flame are not burning in Batt#2,3&4 , major reason of green pushes.• 2.6% of the bottom flame also not burning Batt#2, 3&4.Once spotting the problem, actions needs to be started to resolve them under Implement phase of theproject. But before that in order to quickly hit the target a criterion was set by which all the heatingwalls can be prioritised. The criterion was shown in Table - 3.Sl. Criteria Major Impact PriorityNo.1. Walls having more than one excess gas flues Obscuration One2. Walls having any non burning flues Heating Profile Two3. Walls having one excess gas flue Obscuration Three4. Walls having more than one inadequate burning Heating Profile Fourflues5. Other walls None RestTable – 3The priority list is prepared based on the criterion and started actions under Control phase of theproject. A system was established to monitor the job execution on a daily basis. Every week the jobplanning was done and compliances were monitored and updated in the database. A sample prioritylist is shown in the Figure - 5 (Color coding was done to identify walls where actions already taken).

Priority 1 Priority 2 Priority 3 Priority 4 Rest3 108 6 99A 1018 104 7 92 5028 1 12 112 13168 66A 13 99101 81 19 9127 130 22 12954 5 23 8867 11 36 11496 14 37 862 16 45 634 32 48 618 35 57 599 42 69 4115 49 74 8917 70 78 7720 93 87 5124 98 90 11525 105 102 8226 111 106 5829 118 109 5630 132 110 12631 116 8433 117 8333A 121 5534 123 7640 125 6453 128 4471 132A 3972 6575 6279 3880 12794 8595 73100 60103 52107 47113 21119 97120 66122 46124 43Figure – 5Once all the walls got attended (during 3 rd week of October’2008), a 2 nd round of survey wasconducted on all of 3536 flues. Then the findings are plotted on the data warehouse. By applyingsimilar criterion which was used in initial round of survey results (defects) are tabulated. Then, theseresults are compared with the initial results and outcomes are very encouraging. The comparisongraphs are shown in Figure 6.

---> %ge DefectsSurvey Comparison All Battery35302520151050Nozzle Airport Flame(X's)Top Flame(Ckd)Bottom Flame(Ckd)LeakagePhase I (Jun'08) 6.08 7.92 3.93 29.33 7.72 0.28Phase II (Oct'08) 1.27 3.48 2.15 11.57 1.02 0.28Figure - 6Based on the 2 nd round of survey a new priority list was prepared keeping the criterion same. Actionsstarted based on the priority list and monitoring also done as it was done before. In the 2 nd priority list(Figure – 7), a shifting of number of walls was observed (from left to right) which indicates that wallsare having less defects than before. This was a good symptom and encouraging factor for the team.Phase - 2 ListPriority 1 Priority 2 Priority 3 Priority 4 Rest 136 Nil 100.0%13 5 2 105 1 0 Once 0.0%71 18 6 99A 3 0 Twice 0.0%4 100 10 114 7 0 Third 0.0%8 14 76 11 0 Fourth 0.0%9 15 89 17 0 Fifth 0.0%12 16 132A 20 0 Sixth 0.0%24 19 77 2527 21 99 2628 22 115 2930 23 95 3633A 31 127 3934 32 113 4140 33 88 4348 35 90 44107 37 94 45109 38 117 4654 126 4763 128 4967 62 5072 66A 5374 73 5675 78 5779 84 5880 91 5985 93 6087 118 6192 81 6496 82 6598 83 66101 86 68102 97 69103 108 116104 112 120106 121 124110 129111 131122 42123 51125 55132 7010911913016 3 40 43 340 0 0 0 0 0 0 1360 0 0 0 0 00 0 0 0 0 00 0 0 0 0 00 0 0 0 0 00 0 0 0 0 0

---> Obs. in %ge---> Obs. in %geFigure – 7In the month of November’2008, the coke plants started getting the hit of worldwide economicslowdown. From 1 st week of November’2008 we have started reducing the production slowly and bythe end of December’2008, reduced the schedule by 20% of the capacity. The schedule reductionalso helped a lot in combustion of gases in the flues. The running average of stack obscurations wasshown in the graph (Graph – 1), before and after the project execution. There were some kicksbecause of change in settings of drafts and/or gas feeding but the overall trend is downwards andwithin the norms of EA.Daily average Obscuration Data of Stack 1807060504030201001/06/200808/06/2008807060504030201001/06/200808/06/200815/06/200822/06/200829/06/200806/07/200813/07/200820/07/200827/07/200803/08/200810/08/200817/08/200824/08/200831/08/200807/09/200814/09/200821/09/200828/09/200805/10/200812/10/2008Daily average Obscuration Data of Stack 215/06/200822/06/200829/06/200806/07/200813/07/200820/07/200827/07/200803/08/200810/08/200817/08/200824/08/200831/08/200807/09/200814/09/200821/09/200828/09/2008Graph – 119/10/200826/10/200802/11/200809/11/200816/11/200823/11/200830/11/200807/12/200814/12/200821/12/200828/12/200805/10/200812/10/200819/10/200826/10/200802/11/200809/11/200816/11/200823/11/200830/11/200807/12/200814/12/200821/12/200828/12/2008In order to further reduce the obscuration, changes in design of the nozzles (Figure – 8) are alsounder consideration in the flues where nozzle blocks got broken. The process needs to continue andefforts are ON to further reduce the obscuration level.Figure – 8