Yankee Coating Coverage Optimization--翻譯

1、Drafted in May 2010Modified in December 2012最佳烘缸涂布設(shè)計(jì) Optimal Spray Coverage（最佳覆蓋率） Optimal Droplet Size（最佳噴霧顆粒） Optimal Evaporative Load（最佳蒸發(fā)負(fù)載） Other Considerations（其它因素）How Spray Coverage Works?噴淋涂層如何建立？1)2/3 of volume is in the 1/3 center of the spray area 2/3的噴涂量在中間1/3的噴涂區(qū)域2)How spray fans overl

2、ap determines whether the coating is even or not扇形噴淋重疊如何決定涂層均勻與否Dec. 2012Michael X. Meng - GHY Manufacture Operations4Single coverage 0% of a fan area overlaps by its adjacent one單層覆蓋-相鄰的扇形覆蓋區(qū)域沒有重疊部分Double coverage 50% of a fan area overlaps by its adjacent one雙層覆蓋-相鄰扇形區(qū)域有50%的重疊面積Double coverage 50%

3、 of a fan area overlaps by its adjacent one雙層覆蓋-相鄰扇形區(qū)域有50%的重疊面積Double coverage 50% of a fan area overlaps by its adjacent one雙層覆蓋-相鄰扇形區(qū)域有50%的重疊面積012345616111621263136414651566166717681869196Yankee zonesCoating flow by double coverageTriple coverage 67% of a fan area overlaps by its adjacent one三層覆蓋-

4、相鄰的扇形覆蓋區(qū)域有67%的重疊面積Triple overlap 67% of a fan area overlaps by its adjacent one0123456716111621263136414651566166717681869196Yankee zonesCoating flow by triple coverage50Volumetric Distribution of Spray Nozzle03579 11 13 15 17 19 21 23 25 27 29 31110203040Spray PatternDec. 201210Michael X. Meng - GH

5、Y Manufacture OperationsVolumetric Distribution Spray CoverageTriple Coverage (50% Overlap)Spray Pattern3040200110951317212529Dec. 201211Michael X. Meng - GHY Manufacture OperationsWhat if distance or pressure change?噴淋距離或者壓力的變化會(huì)產(chǎn)生何種影響？Too close coverage is negative太近太近-涂層不好涂層不好Too Far penetration i

6、s drastically reduced太遠(yuǎn)太遠(yuǎn)-噴噴淋的穿透力大幅度的降低淋的穿透力大幅度的降低OptimalToo closeToo farOptimal: Triple Coverage (67% overlap)最佳涂層：三層覆蓋（最佳涂層：三層覆蓋（67%覆蓋率）覆蓋率）1)Type of nozzles噴嘴型號(hào)2)Space between nozzles噴嘴間距3)Distance from nozzle tips to Yankee surface噴嘴到烘缸表面的距離4)Spray-bar pressure噴射壓力Do not change any single factor

7、 alone!They are related. Changes can only be made in a coordinated manner不要單獨(dú)改變?nèi)魏我粋€(gè)因素，他們都相互關(guān)聯(lián)，只能同時(shí)改變。不要單獨(dú)改變?nèi)魏我粋€(gè)因素，他們都相互關(guān)聯(lián)，只能同時(shí)改變。Spray-Bar Requirement噴射壓力要求噴射壓力要求1)Smaller diameter to increase flow velocity but should not be smaller than 100 mm直徑越小，流速越快，但直徑不得小于100mm。2)Nozzle space & distance from ti

8、ps to Yankee are determined by the design of nozzle噴嘴間距及噴嘴到烘缸表面的距離取決于噴嘴的設(shè)計(jì)。3)Spray Pressure 3 4 bars噴射壓力3-4bar4)With recirculation if machine is 3.5 m or wider5)No oscillation needed if triple coverage如果是三層覆蓋，不需要折動(dòng)。Pressure vs. Droplet Size壓力VS水滴大小Misperception誤解誤解 The faster a machine runs the high

9、er the spray pressure has to be, in order for the spray droplets penetrate the windage curtain layer to the Yankee surface為了使噴霧穿透空氣阻力到達(dá)烘缸表面，紙機(jī)車速越快，噴射壓力必須要大。Pressure vs. Droplet SizeThe Fact事實(shí)上事實(shí)上 The momentum (mass x velocity) determines the ability of droplets to penetrate the windage curtain layer

10、 to the Yankee surface動(dòng)量（質(zhì)量*速度）決定了噴霧穿透空氣阻力到達(dá)烘缸表面的能力Droplet size decreases and velocity increases when spray pressure increases （壓力增加時(shí)，水滴變小，速度增加）Pressure vs. Droplet SizeA Case StudySpray P. bar 37Droplet, D. um11095Mass, kg 5.58E-093.58E-09Flow, l/s0.00650.01Tip velocity, m/s19.929.23Initial momentu

11、m,1.11E-071.05E-07kg.m/sTake-aways1)droplet momentum DOES NOT increase with pressure水滴沖量不會(huì)隨壓力的增大而增大2)smaller droplets has a much higher momentum loss in the path在噴射過程中，越小的水滴，動(dòng)量流失越大00.0020.0040.0060.0080.010.0120.0140.0160.0180.02100200300400500700600800Nozzle Orifice Size15 DEG65 DEG95 DEG50 DEGMedi

12、an Volume Droplet Size4 SPRAY ANGLES 100 PSINozzle Orifice SizeDroplet Size (Microns)Dec. 201218Michael X. Meng - GHY Manufacture OperationsGood Mixing Is Imperative for Stable and Even Coating良好的混合是建立穩(wěn)定均勻涂層的必備條件良好的混合是建立穩(wěn)定均勻涂層的必備條件Typical chemical content is 1 1.5% or below in spray. 化藥噴淋的濃度一般為1-1.5

13、%，或者更低 This can be ensured if the evaporation load is normal 如果蒸發(fā)負(fù)載正常，可以獲得良好的涂層Recommend a mixing tank with heating prior to injection在噴淋前，建議加熱混合槽Online static mixer is a must if no mixing tank 如果沒有混合槽，必須有在線靜態(tài)混合器Dec. 201219Michael X. Meng - GHY Manufacture OperationsCoating Application System- Pre-m

14、ix styleRecirculation LineChemicalsWaterDec. 201220Michael X. Meng - GHY Manufacture OperationsCoating Application System- Direct InjectionHard WaterChemicalsMixerSpray Boom & NozzlesFilters (2)YankeeSurfacePressureGaugesBooster PumpVariable Speed ChemicalMetering Pumps (Gear)MassFlowmetersIn-lineVS

15、VSVSFICFICFICCheckValvesDec. 201221Michael X. Meng - GHY Manufacture Operations To form a tacky film suitable for optimal creping as well as Yankee protection形成適合最佳起皺同時(shí)保護(hù)烘缸的黏性涂層Older generations of coating chemicals will form the film only when they are dried早期化藥在完全干燥后才會(huì)形成涂層Some new ones can start c

16、rosslink during the drying process as temperature increases by the heat一些新化藥會(huì)隨著溫度的升高開始發(fā)生交聯(lián)反應(yīng)Used to be: nearly all carry water has to be evaporated at the point of sheet pickup過去：當(dāng)紙頁被剝離時(shí)，幾乎所有水分才會(huì)被完全蒸發(fā)Now: it is very complicated. It is a case-by-case situation現(xiàn)在：情況復(fù)雜，需具體分析。Dec. 201222Michael X. Meng

17、- GHY Manufacture OperationsIf too much carry water The coating will be wet, non-tacky or easily washed off by the incoming sheet如果有太多水分，涂層會(huì)很濕，沒有黏性，容易被洗掉If too little carry water The coating is subject to excess heat and can start to oxidize, leading to a “Baked on” coating with a hard, glassy surfa

18、ce, often low adhesion (low bulk), blade chatter, and pin holes如果水分太少，化藥涂層溫度過高而開始氧化，形成硬且光滑的表面，涂層黏度低（低松厚度），刮刀震動(dòng)，產(chǎn)生針孔。Dec. 201223Michael X. Meng - GHY Manufacture OperationsTotal evaporative Rate =總蒸發(fā)率=1)Spray carry water which must be evaporated prior to wet press on the bottom of the Yankee 噴淋多余水分需在

19、壓榨前被蒸發(fā)掉 2）Water in the sheet from about 35% dryness to 97%, from the pickup all the way to creping point. This portion is aided by the hood, normally up to 60% 紙頁自上烘缸到起皺，干度從35%到97%，這部分主要受益于護(hù)罩，去除水分幾乎達(dá)60%。Dec. 201224Michael X. Meng - GHY Manufacture OperationsYankee DryerWetPressCoating SprayCrepeWhat

20、 much is too much or too little?多少是太多或太少？Carry water flow is determined by number of nozzles, its design and the spray pressure噴淋水量取決于噴嘴數(shù)量，型號(hào)及其噴射壓力Spray is normally applied to the bottom of the Yankee, and the evaporation of carry water takes place before sheet pickup噴淋一般安裝在烘缸下面，噴淋水的蒸發(fā)一般在紙頁上烘缸之前In t

21、his unsheeted area, the steam inside does all evaporation, with no aid from hood在無紙區(qū)域，蒸汽全用于水分蒸發(fā)，并沒有借助于護(hù)罩Dec. 201225Michael X. Meng - GHY Manufacture OperationsWhat much is too much or too little?Carry water amount should be compatible to the Yankees evaporation rate, as well as to the coating chemis

22、try, so that its removal prior to the sheet pickup is appropriate噴淋水總量應(yīng)該與烘缸的蒸發(fā)率及涂層化藥相應(yīng)，所以噴淋水應(yīng)該在紙頁上烘缸之前被蒸發(fā)掉。This ensures Optimal Creping ControlAnd Best Yankee Protection 這樣可確保最佳的起皺和烘缸保護(hù)作用這樣可確保最佳的起皺和烘缸保護(hù)作用Dec. 201226Michael X. Meng - GHY Manufacture OperationsHow to determine it?如何確定蒸發(fā)率如何確定蒸發(fā)率Evapora

23、tive rate is a direct indication of a Yankees drying capability蒸發(fā)率是烘缸干燥效率的直接指導(dǎo)因素It is very hard to define. 很難被定義It is normally estimated by 通常這樣估算Evaporative rate = (condensing rate)/1.5 蒸發(fā)率=冷凝率/1.5Condensing rate can be measured. Normally in 250-400 kg/hr/m2冷凝率是可測(cè)的。通常為250-400 kg/hr/m2Evaporative ra

24、te is thus 150 250 kg/hr/m2因此蒸發(fā)率為150 250 kg/hr/m2Dec. 201227Michael X. Meng - GHY Manufacture OperationsDec. 201228Michael X. Meng - GHY Manufacture OperationsCondensing Rate MeasurementsTAPPI Standard 0404-491.Stop discharge pump停止出口泵停止出口泵2.Start timer開始計(jì)時(shí)開始計(jì)時(shí)器器3.Track flash tank level記錄冷凝水箱液位記錄冷凝水

25、箱液位4.Use volume increase體積增長體積增長5.Yankee diameter, width烘缸直徑，寬度烘缸直徑，寬度6.Calculate kg/hr/m2計(jì)算計(jì)算Definition Drying need for spray water from the nozzle tips till the sheet pickup 定義-從噴嘴到紙頁上烘缸時(shí)干燥所需的噴淋水 A Case Study (SZ TM1/2) Yankee width 烘缸寬度6200 mm No. nozzles 噴嘴數(shù)量25 Flow per nozzle at 4 bar 4bar壓力時(shí)噴嘴

26、流量 0.51 l/min Total flow總流量 12.75 l/min Dwell distance 413 mm Dwell area 2.56 m2 Spray reaching Yankee 噴淋量80 % Specific evaporative load 單位蒸發(fā)負(fù)載239.01 kg/hr/m2 Dec. 201229Michael X. Meng - GHY Manufacture OperationsA Case Study (SZ TM1/2) Specific evaporative load 239.01 kg/hr/m2 In the range we norm

27、ally see Final confirmation should be done by comparing to the machines evaporative rateDec. 201230Michael X. Meng - GHY Manufacture OperationsDryer Coating烘缸涂層烘缸涂層The role of water chemistry in pipe corrosionhas long been unknown.水化學(xué)在管道腐蝕中的作用始終是陌生的Calcium hardness forms scale on pipe walls,preventing corrosive attack.鈣硬度在管壁上形成一定數(shù)量可以組織腐蝕侵害With enough calcium hardness and alkalinitythis mechanism protects yankee dryers too.足夠的鈣硬度和堿度也可以保護(hù)烘缸Dec. 201231Michael X. Me