Yankee Coating Coverage Optimization--翻译

1、Drafted in May 2010Modified in December 2012最佳烘缸涂布设计 Optimal Spray Coverage（最佳覆盖率） Optimal Droplet Size（最佳喷雾颗粒） Optimal Evaporative Load（最佳蒸发负载） Other Considerations（其它因素）How Spray Coverage Works?喷淋涂层如何建立？1)2/3 of volume is in the 1/3 center of the spray area 2/3的喷涂量在中间1/3的喷涂区域2)How spray fans overl

2、ap determines whether the coating is even or not扇形喷淋重叠如何决定涂层均匀与否Dec. 2012Michael X. Meng - GHY Manufacture Operations4Single coverage 0% of a fan area overlaps by its adjacent one单层覆盖-相邻的扇形覆盖区域没有重叠部分Double coverage 50% of a fan area overlaps by its adjacent one双层覆盖-相邻扇形区域有50%的重叠面积Double coverage 50%

3、 of a fan area overlaps by its adjacent one双层覆盖-相邻扇形区域有50%的重叠面积Double coverage 50% of a fan area overlaps by its adjacent one双层覆盖-相邻扇形区域有50%的重叠面积012345616111621263136414651566166717681869196Yankee zonesCoating flow by double coverageTriple coverage 67% of a fan area overlaps by its adjacent one三层覆盖-

4、相邻的扇形覆盖区域有67%的重叠面积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?喷淋距离或者压力的变化会产生何种影响？Too close coverage is negative太近太近-涂层不好涂层不好Too Far penetration i

6、s drastically reduced太远太远-喷喷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)最佳涂层：三层覆盖（最佳涂层：三层覆盖（67%覆盖率）覆盖率）1)Type of nozzles喷嘴型号2)Space between nozzles喷嘴间距3)Distance from nozzle tips to Yankee surface喷嘴到烘缸表面的距离4)Spray-bar pressure喷射压力Do not change any single factor

7、 alone!They are related. Changes can only be made in a coordinated manner不要单独改变任何一个因素，他们都相互关联，只能同时改变。不要单独改变任何一个因素，他们都相互关联，只能同时改变。Spray-Bar Requirement喷射压力要求喷射压力要求1)Smaller diameter to increase flow velocity but should not be smaller than 100 mm直径越小，流速越快，但直径不得小于100mm。2)Nozzle space & distance from ti

8、ps to Yankee are determined by the design of nozzle喷嘴间距及喷嘴到烘缸表面的距离取决于喷嘴的设计。3)Spray Pressure 3 4 bars喷射压力3-4bar4)With recirculation if machine is 3.5 m or wider5)No oscillation needed if triple coverage如果是三层覆盖，不需要折动。Pressure vs. Droplet Size压力VS水滴大小Misperception误解误解 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为了使喷雾穿透空气阻力到达烘缸表面，纸机车速越快，喷射压力必须要大。Pressure vs. Droplet SizeThe Fact事实上事实上 The momentum (mass x velocity) determines the ability of droplets to penetrate the windage curtain layer

10、 to the Yankee surface动量（质量*速度）决定了喷雾穿透空气阻力到达烘缸表面的能力Droplet size decreases and velocity increases when spray pressure increases （压力增加时，水滴变小，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水滴冲量不会随压力的增大而增大2)smaller droplets has a much higher momentum loss in the path在喷射过程中，越小的水滴，动量流失越大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良好的混合是建立稳定均匀涂层的必备条件良好的混合是建立稳定均匀涂层的必备条件Typical chemical content is 1 1.5% or below in spray. 化药喷淋的浓度一般为1-1.5

13、%，或者更低 This can be ensured if the evaporation load is normal 如果蒸发负载正常，可以获得良好的涂层Recommend a mixing tank with heating prior to injection在喷淋前，建议加热混合槽Online static mixer is a must if no mixing tank 如果没有混合槽，必须有在线静态混合器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形成适合最佳起皱同时保护烘缸的黏性涂层Older generations of coating chemicals will form the film only when they are dried早期化药在完全干燥后才会形成涂层Some new ones can start c

16、rosslink during the drying process as temperature increases by the heat一些新化药会随着温度的升高开始发生交联反应Used to be: nearly all carry water has to be evaporated at the point of sheet pickup过去：当纸页被剥离时，几乎所有水分才会被完全蒸发Now: it is very complicated. It is a case-by-case situation现在：情况复杂，需具体分析。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，涂层会很湿，没有黏性，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，化药涂层温度过高而开始氧化，形成硬且光滑的表面，涂层黏度低（低松厚度），刮刀震动，产生针孔。Dec. 201223Michael X. Meng - GHY Manufacture OperationsTotal evaporative Rate =总蒸发率=1)Spray carry water which must be evaporated prior to wet press on the bottom of the Yankee 喷淋多余水分需在

19、压榨前被蒸发掉 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% 纸页自上烘缸到起皱，干度从35%到97%，这部分主要受益于护罩，去除水分几乎达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喷淋水量取决于喷嘴数量，型号及其喷射压力Spray is normally applied to the bottom of the Yankee, and the evaporation of carry water takes place before sheet pickup喷淋一般安装在烘缸下面，喷淋水的蒸发一般在纸页上烘缸之前In t

21、his unsheeted area, the steam inside does all evaporation, with no aid from hood在无纸区域，蒸汽全用于水分蒸发，并没有借助于护罩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喷淋水总量应该与烘缸的蒸发率及涂层化药相应，所以喷淋水应该在纸页上烘缸之前被蒸发掉。This ensures Optimal Creping ControlAnd Best Yankee Protection 这样可确保最佳的起皱和烘缸保护作用这样可确保最佳的起皱和烘缸保护作用Dec. 201226Michael X. Meng - GHY Manufacture OperationsHow to determine it?如何确定蒸发率如何确定蒸发率Evapora

23、tive rate is a direct indication of a Yankees drying capability蒸发率是烘缸干燥效率的直接指导因素It is very hard to define. 很难被定义It is normally estimated by 通常这样估算Evaporative rate = (condensing rate)/1.5 蒸发率=冷凝率/1.5Condensing rate can be measured. Normally in 250-400 kg/hr/m2冷凝率是可测的。通常为250-400 kg/hr/m2Evaporative ra

24、te is thus 150 250 kg/hr/m2因此蒸发率为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开始计时开始计时器器3.Track flash tank level记录冷凝水箱液位记录冷凝水

25、箱液位4.Use volume increase体积增长体积增长5.Yankee diameter, width烘缸直径，宽度烘缸直径，宽度6.Calculate kg/hr/m2计算计算Definition Drying need for spray water from the nozzle tips till the sheet pickup 定义-从喷嘴到纸页上烘缸时干燥所需的喷淋水 A Case Study (SZ TM1/2) Yankee width 烘缸宽度6200 mm No. nozzles 喷嘴数量25 Flow per nozzle at 4 bar 4bar压力时喷嘴

26、流量 0.51 l/min Total flow总流量 12.75 l/min Dwell distance 413 mm Dwell area 2.56 m2 Spray reaching Yankee 喷淋量80 % Specific evaporative load 单位蒸发负载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烘缸涂层烘缸涂层The role of water chemistry in pipe corrosionhas long been unknown.水化学在管道腐蚀中的作用始终是陌生的Calcium hardness forms scale on pipe walls,preventing corrosive attack.钙硬度在管壁上形成一定数量可以组织腐蚀侵害With enough calcium hardness and alkalinitythis mechanism protects yankee dryers too.足够的钙硬度和碱度也可以保护烘缸Dec. 201231Michael X. Me