流体输送设备的控制课件.ppt
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- 流体 输送 设备 控制 课件
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1、Control of Distillation Column(精馏塔控制)Lei XieInstitute of Industrial Control,Zhejiang University,Hangzhou,P.R.China2012/05/23Problem DiscussionCVs(被控变量):P,LD,LB,xD,xBMVs(操作变量):D,B,L,QH,QC,DGDVs:F,xF,TFTo design your multi-loop control system to satisfy the above requirements and reduce interactionCon
2、tentsnDistillation Principle&Control ProblemsnColumn Pressure ControlnMaterial Balance(物料平衡)ControlnProduct Purity Control(1)Distillate Purity Control(2)Bottom Purity Control(3)Both Distillate&Bottom Purity ControlnOther Control SchemesA Typical Distillation Columnwith Two ProductsProcess Descriptio
3、n,Balance Conditions,Control Objectives&CVs Selection?Control ObjectivesnGuarantee operation safetynDecrease disturbancesnControl purity and composition of productsnIncrease the product yieldnReduce the operational energySelection of CVs&MVsMVs Selection?Control Problems of Distillation ColumnPressu
4、re Control ProblemCV:PMVs:QC,DG,V,L DVs:F,xFMV Selection&Control Schemes?Pressure Control SchemesFLDPCFLDPCScheme 1.1:MV is the unconden-sable vapors(不凝气)vent flowScheme 1.2:MV is the coolant flow to control column pressureApplication case based on effectiveness Level Control Problem(or Material Bal
5、ance Control)CVs:LD,LBMVs:L or D,QV or BDVs:F,xFCVs&MVs Pairing?Level Control Scheme 2.1Advantages&disadvantages?Level Control Scheme 2.2Advantages&disadvantages?Level Control Scheme 2.3Advantages&disadvantages?Measurement of Product PuritynDirect measurement approaches(1)On-line composition/quality
6、 analyzers(在线分析仪),(2)soft sensors/inferential measurement(软测量仪).nIndirect measurement approaches(1)Sensitive tray temperature(灵敏板温度)or bubble point of the liquid,if the column pressure is constant;(2)Pressure compensated temperature;(3)Difference between tray temperature and top/bottom temperature.M
7、aterial Balance(物料平衡)for a Column with Binary MixtureBDFOverall material balance:BDFBxDxFxBDFDBDBFxxxxFBxxxxFD,Balance for light component:Material balance line:BFDxFDxFDx11111Relation of D/F to 1-xD,xB?Separation factor for a Binary Mixture)1()1(11DBBDBBDDxxxxxxxxSSeparation factor S(分离度):Separatio
8、n curve:)1(1SxSxxBBD)1(111SxxxBBDorRelation of S to 1-xD,xB?Variables to Influence the Separation Factor relative volatility(相对挥发度)For variable reflux ratio L/D(回流比):nEFxLDS11 n:number of stages E:average stage efficiency Influence of L/D,xF to S?Operating Points for a binary-component columnOperati
9、ng condition:xF=0.52,n=16,E=0.816,0.2Analyze the influence of MVs!Effects of V/F to D/F&L/D in Distillate&Bottom If the feed is in the form of liquid,and the material in the condenser keeps balance,thenDLVVR(1)If L/F is constant,V/FD/F&D/L;(2)If D/F is constant,V/F D/L;(3)If V/F is constant,D/F L/F
10、L/D.Distillation Product Purity Control Problems(C)(A)(B)Distillate Purity Control ProblemCVs:LD,TR,LBMVs:L,D,QV or BDVs:F,xFCVs&MVs Pairing?Distillate ProductPurity Control Scheme 3.1AAdvantages&disadvantages:(1)Fast&strong control effect of L to TR,(2)Negative influence of reflux(回流量)fast change t
11、o column operation,(3)Difficult to control LT22 if D L.Distillate ProductPurity Control Scheme 3.1BAdvantages&disadvantages:(1)Positive influence of reflux smooth change,(2)Easy to control LT22 if D L,(3)Slow control effect of D to TR,(4)Strong coupling between TC32&LC22.Distillate ProductPurity Con
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