Development of New Cokemaking Process, SCOPE21

Development of New Cokemaking Process, SCOPE21

As the final phase of the project, we built a test plant on the premises of Nippon Steel’sNagoya Works to confirm the performance expected at the R and D stage and collectthe engineering data for designing a commercial plant.3.1 Specifications of the pilot plantThe main specifications of the pilot plant are shown in Table I and the process flow ofthe plant in Figure 2. The pilot plant shown in Photo 1 consists of a coal pretreatmentfacility which is the scale-up version of the bench scale plant, and a coke oven.The coal pretreatment facility is designed to have a 6t/h coal throughput, and the basicspecifications are determined from the bench scale plant data. One coke oven wasconstructed. The coke oven chamber is 8m in length, which is almost half thecommercial plant, 7.5m in height and 450mm in width. New chamber walls are made ofsuper dense brick whose heat conductivity is 1.3 times higher than that of theconventional silica brick. The thickness of the bricks is designed to be as thin as 70mm.Because the reheating of the coke discharged at medium temperatures had been testedin an existing CDQ, the coke upgrading facility was excluded from the pilot plant.3.2 Operation of the pilot plantSince the first coke was discharged from the test coke oven in March 2002, the plantwas successfully run on schedule for about one year until March 2003 and thecarbonization tests were carried out 440 times. During the operation, all the operationconditions were arranged according to the testing items in order to confirm the targets ofthe concept. In the plant operation, the flue temperature was arranged between 1100°Cand 1280°C. Consequently, the coking time was ranged from 12 to 8 hours.4. Pilot plant test results4.1 Utilization of coal resourcesIn the coal rapid preheating test, the coal was heated slowly to 300°C in a fluidized beddryer, and then heated rapidly to 380°C in a pneumatic preheater, and carbonized in thecoke oven. The quality of the obtained coke was estimated by the JIS drum index(DI150/15). Table II shows the characteristics of the tested coal, and the poor-coking coalwas blended 50% in the coal charge. As shown in Figure 3, the coke strength (DI150/15)became about 2.5 points higher than conventional level at the flue temperature around1250°C.To detail the upgrading effect, the coal heated in a fluidized bed dryer was passedthrough the pneumatic preheater by the gas flow of 300°C and it was revealed that thedrum index became 0.9 points higher by virtue of the rapid preheating effect.Furthermore, 1.0 points of drum index was improved due to the increased bulk density.The reminded 0.6 points was thought due to the homogenization effect.4.2 High productivity in cokemaking

Preheating the coal charge, employing the high heat conductivity brick, and loweringthe coke discharge temperature have the effect of reducing coking time. Coking time ofpilot plant operation was 8 hours in the case of the coal charge preheated to 280°C, andthe flue temperature of 1250°C. According to the test results of the pilot plant, theproductivity of a commercial plant of the SCOPE21 process was estimated to beenhanced 2.4 times as high as that of the conventional one (Figure 4).Only a minor amount of carbon deposits was found in the area of the feed connectionand standpipe base, which was the same as in conventional process. This is consideredbecause of the effect of briquetting of fine coal according to the basic research (Figure 5).4.3 Environmental protectionEnvironmental conditions will be improved by conveying the hot coal in the sealedstructure, by preventing gas leakage the from the coke oven and by reducing NO x in thecombustion gas due to the new coke oven heating system.1) Smokeless conveying of hot coalWe developed a plug flow transport method for conveying the preheated coal in the pilot plant test. Thetransport rate of 350t/h was a sufficiently high rate even in commercial plants. This charging system makes itpossible to charge high temperature preheated coal into coke a oven safely and cleanly without scatteringdusts.2) Low NO x combustion from coke ovenThe pilot plant is equipped with a new combustion system that will attain the high productivity, uniformheating and low NO x emissions which are the basic requirements the next-generation coke oven has to meet.The new heating chamber is as large as that of the typical commercial plant. Its chamber wall is made ofsuper dense silica brick high heat conductivity for higher productivity. As shown in Figure 6, NO x concentrationin the combustion gas was less than 100ppm when the flue wall temperature was 1250°C, which was thesame temperature measured in the actual scale combustion test.3) Gas leakageIt is usually very difficult to prevent gas leakage from the coke oven because the seal is not perfect and theoven is operated with a gas pressure that is higher than the ambient pressure. SCOPE21 process has anairtight structure in which the oven was completely covered with hoods and a gas pressure control system forthe coke oven was developed for a sub-atmospheric pressure operation. The collected engineering data wasused for the feasibility study of a commercial plant.4) Energy savingThe SCOPE21 process can reduce net energy consumption by 21% as shown in Figure 7. The netenergy consumption for carbonization can also be decreased by preheating the coal charge and by loweringthe coke discharging temperature although an extra power needs in the coal pretreatment system.

5. Blueprint of the commercial plant5.1 Design of the plant scaleThe production capacity of a new coke plant is about 4000t/day (1.5Mt/year) coke,which is high enough for 4000 cubic meter class blast furnace. Figure 8 is a conceptualdescription of the commercial plant, and its specifications are listed in Table III. Becausethe SCOPE21 process has a higher productivity than the conventional one, the numberof required ovens decreases in half or less.5.2 Construction costThe construction cost of the SCOPE21 process is estimated to be reduced by 16% incomparison with the conventional one as shown in Figure 9. The reduction of thenumber of coke ovens dominates the reduction of the construction cost.5.3 Coke production costThe coke production cost of the SCOPE21 process is estimated to be reduced by18% in comparison with the conventional one as shown in Figure 10. The increase in theratio of poor coking coal dominates the reduction of the cost.6. ConclusionJapan developed an innovative cokemaking process SCOPE21 to meet the futurecoal demands and environmental protection. The pilot plant was successfully operatedand the project concepts were confirmed. 50% utilization of poorly caking coal made agood quality coke. Productivity of coke oven was enhanced 2.4 times of conventionalone without any torment of carbon trouble, achieving uniform heating and low NO xcombustion. The construction cost as well as coke production cost was estimated to bereduced by less 20% compared with the conventional process.The blast furnace method will remain as the most important ironmaking technologyeven in the 21st century. I am confident that the SCOPE21 process will becommercialized in the near future and contribute to the development of cokemakingtechnologies in many countries.References1. K.Nishioka, “Challenge for innovative cokemaking process in Japan,” 3rdInternational Cokemaking Congress Proceedings, Gent, Belgium, 1996, pp.285-290.2. H.Taketomi, K.Nishioka, Y.Nakashima, S.Suyama, M.Matsuura, “Research on coalpretreatment process of SCOPE21,” 4th European Coke and Ironmaking CongressProceedings, Paris, France, June 2000, pp.640-645.

3. S.Suyama, K.Nishioka, T.Yamada, H.Shima, I.Sugiyama, H.Fujikawa, M.Yamamoto,“Development of SCOPE21 Cokemaking Process,” 1st China International CokingTechnology and Coke Market Congress 2002, Beijing, P.R.China, September 2002,pp.122-132.

Hot briquetting machineCoal plugconveying systemEmission freecoal chargingDust collecting systemHighly sealed oven doorPneumaticpreheaterCoalFinecoalEmission freecoke pushingCoarsecoalCoking chamber・Medium temp. carbonization・Super denced brick & thin wall・Pressure controlEmission freecoke dischargingEmission free coketravelling systemCDQCoke upgradingchamberFluidized bed dryerTable I Main specifications of the pilot plantMain equipmentBasic specificationsFluidized bedPneumatic preheaterBriquetting machineCoke ovenCoke quenching carCoal throughput : 6.0 dry-t/hrCokeFigure 1 Schematic diagram of the SCOPE21 process flow.Coal throughput : 6.0 dry-t/hr (coarse coal): 2.4 dry-t/hr (fine coal)Type : double rollMold : massec type (18cc)Capacity : 2.4t/hrOven size : 7.5mH x 8.0mLx 0.45mWBrick material : super densed brickHeat conductivity: 2.3kcal/m hr KBlastfurnaceCoalhopperFine coalFluidizedbeddryer CoarsecoalPneumaticpreheaterBriquettingmachineHot coalconveyingsystemPusherCokeovenCOGSeparaterFeederGuideDry quencherCokeHot gas generatorFigure 2 Schematic diagram of the pilot plant.AIRMGCOGN2

Photo 1 The pilot plant of SCOPE21.Table II Characteristics of the tested coals.Proximate analysis(%,dry)VMAshFluidity index,MF(log ddpm)BlendingRatio(%)Coal A (coking coal) 24.6 9.0 2.70 25Coal B (coking coal) 26.3 9.0 1.77 25Coal C (poor-coking coal) 34.6 9.2 1.70 5086Drum Index,D I 150 15 (-)8482+ heatingBulk densityHomogenization80ConventionalSCO P E21Figure 3 Effect of improvements on the coke strength by the SCOPE21 process.

2520ConventionalCoking time (hr)15105Charging coal temp.・Conventional:25℃・SCOPE21 :330℃SCOPE21Tar seam temp. :1000℃Tar seam temp. :900℃01050 1100 1150 1200 1250 1300Flue temperature (℃)Figure 4 Reduction of coking time by the SCOPE21 process.5Carbon deposition(kg/m 2 -ch)43210ConventionalBriquettingNon-briquettingSCOPE21Figure 5 Effect of briquetting of fine coal on carbon deposition.400NOx (ppm,02=7%)300200100Conventionalheating flue flueNew typeheating flueTarget08001000 1200Heating flue wall temperature (℃)1400Figure 6 Relationship between heating flue wall temperature and NO x proportion.

Development ofNew Cokemaking Process,SCOPE21Kiyoshi FUKADAJFE Steel CorporationJAPAN

Service time of coke ovens in JapanNumbers of coke ovens86422001 year2010 year020 25 30 35 40Service time (years)End ofoven life45

Main topics of the presentation1. Outline of the SCOPE21 process.2. Pilot plant test results.3. Feasibility study of commercial plant.

Targets of SCOPE211. Increasing the ratio of poor-coking coalfrom 20% to 50%.2. Higher productivity for reducing theconstruction costs.3. Reducing NO x by 30% and no smoke /no dust operation.4. Energy saving by 20% for reducing CO 2 .

Commercialization steps of SCOPE21Scale oftest plant1stB.P.2ndP.P.3rdC.P.Coal pretreatmentprocess0.6t/h(1/200×C.P.)6.0t/h(1/20×C.P.)240t/h(120t/h×2set)Coke ovenCombustion chamber(Actual scale test)1 coke oven(½ length)34t/oven×nB.P : Bench scale plantP.P : Pilot plantC.P : Commercial plant

SCOPE21 process flowHot briquetting machineEmission freecoal chargingCoal plugDust collecting systemconveying systemHighly sealed oven doorPneumaticpreheaterEmission freecoke pushingCoking chamberEmission freecoke dischargingEmission free coketravelling systemCoalFinecoalCoarsecoal・Medium temp. carbonization・Super denced brick & thin wall・Pressure controlCDQCoke upgradingchamberFluidized bed dryerCoke quenching carCokeBlastfurnace

Carbonization Image of SCOPE21Temperature (°C)10008006004002003 ReheatingSCOPE212 Carbonizing1 Rapid heatingConventional0 2 4 6 8 10 12 14 16 18Coking time (Hr)

Results of the pilot plant test

External view of the pilot plant 1

Overall process flow of the pilot plantFine coalCOGCoalhopperFluidizedbeddryerCoarse coalPneumaticpreheaterBriquettingmachine Hot coalconveyingsystemPusherSeparaterFeederGuideCokeovenDry quencherCokeHot gas generatorAIRMGCOGN2

Main specifications of the pilot plantMain equipmentFluidized bedPneumatic preheaterBriquetting machineCoke oven6.0 dry-t/hBasic specifications6.0 dry-t/h (coarse coal)2.4 dry-t/h (fine coal)Double roll, massec type (18cc)2.4 t/hSize : 7.5mH x 8.0mL x 0.45mWWall : Super Dense Silica2.3kcal/m hr °C

Construction of the pilot plantFlueCoking chamber

Pushing operation of coke cake

Improvement of coke strength86Drum Index, DI 150 158482+ 2.50.9 Rapid heating1.0 Bulk density0.6 Homogenization80ConventionalSCOPE21

Reduction of coking timeby the SCOPE21 processCoking time (Hr)252015105Charging coal temp.Conventional: 25°CSCOPE21: 330°CSCOPE21ConventionalTar seam temp.:1000°C900°C01050 1100 1150 1200 1250 1300Flue temperature (°C)

Relationship between heating flue walltemperature and NO x content400NO x (ppm, O 2 =7%)3002001000800Conventionalheating flue1000 1200New typeheating flue1400Heating flue wall temperature (°C)Target

Blueprint of the commercial plant

Main specification of SCOPE21Conventional(ref.)SCOPE21Charging Moisture (%)coal Temperature (°C )Coke ovenoperationCoke ovenBasicspecificationsFlue temp.Coking timeProductivityDimensionsWall brick(°C )(h)(m)Number of ovens9.0 025 3301250 125017.5 7.41 2.47.5H x 16L x 0.45W7.5H x 16L x 0.45Wdense silica super dense silica(Thickness = 100mm) (Thickness = 70mm)126 53*Assuming of coke production capacity =about 4000 t/day

(Production capacity : 4000 t-coke/daytConventional process126 ovensCommercial plantSCOPE21 process53 ovens

Energy saving by the SCOPE21 processEnergy consumption (%)100806040200Conventional-21%SCOPE21

Cost reduction by SCOPE2110080-16%10080-18%Cost (%)604020Cost (%)60402000ConventionalSCOPE21ConventionalSCOPE21Construction costCoke production cost

Summary1. The basic technologies of SCOPE21process were established by 10 yearnational program.2. The SCOPE21 process has greateconomical advantages over theconventional process.

Coke oven construction programCompany(Location)Production(Oven)OperationstartNippon Steel(Nagoya)0.17 Mt/y(25)‘04(April)Under construction(Reconstruction)JFE Steel(Fukuyama)0.5 Mt/y(50)‘06(June)Under construction(Additional construction)Mitsui Mining(Kitakyusyu)0.5 Mt/y(46)‘06Under construction(Reconstruction)Nippon Steel(Oita)1.0 Mt/y‘08Under contemplation(SCOPE type)

*Biography (Kiyoshi Fukada)I am a senior researcher of JFE Steel Corporation and primarily responsible for cokemaking process.I majored in chemical engineering at the Kyoto University, and then joined a steel company, NKKCorporation predecessor of JFE Steel Corporation, in 1991.I began my career as a researcher in the field of coal and coke and have spent more than 10 yearsanalyzing bituminous coal, improving cokemaking technology, developing new cokemaking processand so on. As a result, I have innovated some techniques for reducing production cost or saving energyconsumption to actual plants.In 1994 I joined the national project, SCOPE21 conducted by the Japan Iron and Steel Federationand the Center for Coal Utilization, Japan. I carried out basic research and contributed to thedevelopment of coal preheating technology.Furthermore, from 2000 to 2002, I was at the Aachen University of Technology in Germany as aguest researcher and studied about the reduction of energy consumption in ironmaking process.Nowadays, the balance of coking coal supply and demand has changed rapidly. Therefore I haveconsiderable interest in research for coal utilization technology which is unaffected by the balancebetween supply and demand.

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