Chapter 7 Equilibrium-Stage Operations
1 Chapter 7 Equilibrium-Stage Operations
Cascades逐级接触设备 One class of mass-transfer devices consists of assembliesof individual units,or stages,interconnected so that the materials being processed pass through each stage in turn.The two streams move counter currently through the assembly;in each stage they are brought into contact,mixed,and then separated.Such multistage systems are called cascades
2 • One class of mass-transfer devices consists of assembliesof individual units, or stages,interconnected so that the materials being processed pass through each stage in turn. The two streams move counter currently through the assembly; in each stage they are brought into contact, mixed, and then separated. Such multistage systems are called cascades. Cascades 逐级接触设备
Ideal Stage理想级Equilibrium Stage 平衡级theoretical Stage理论级 y2 is in equilibrium with x2. y2 y 2 3
3 Ideal Stage理想级/Equilibrium Stage 平衡级/theoretical Stage理论级 ( ) 3 3 3 2 2 2 1 1 1 D F x t y x t y x t y x x ( ) 3 3 3 2 2 2 1 1 1 D F x t y x t y x t y x x ( ) 3 3 3 2 2 2 1 1 1 D F x t y x t y x t y x x ( ) 3 3 3 2 2 2 1 1 1 D F x t y x t y x t y x x • y2 is in equilibrium with x2
Ideal Plate/Equilibrium Plate/Theoretical Plate/Perfect plate X y2 is in equilibrium with x2. X2 4
4 Ideal Plate/Equilibrium Plate/Theoretical Plate/Perfect plate ( ) 3 3 3 2 2 2 1 1 1 D F x t y x t y x t y x x ( ) 3 3 3 2 2 2 1 1 1 D F x t y x t y x t y x x ( ) 3 3 3 2 2 2 1 1 1 D F x t y x t y x t y x x ( ) 3 3 3 2 2 2 1 1 1 D F x t y x t y x t y x x • y2 is in equilibrium with x2
1.Equipment for stage contacts 1)Typical distillation equipment Fig.20.1.Equipment for continuous distillation. 5
5 1. Equipment for stage contacts • 1) Typical distillation equipment • Fig.20.1. Equipment for continuous distillation
Conder Rectifying section reflu: Overhead product Feed plate Feed 。Equipment for Vapor continuous distillation. Stripping /Enriching Bottom product section reboiler
6 ( ) 3 3 3 2 2 1 1 1 D F x t y x t Froth x t y x x ( ) 3 3 2 2 2 1 1 1 D F x t y Liquid t y x t y x x ( ) 3 3 3 2 2 2 1 1 D F x t y x t y x t Vapor x x • Equipment for continuous distillation. 塔底产品 加热器（再沸器） 上升蒸汽 进料 回流 塔顶产品 Condenser 塔底产品 加热器（再沸器） 上升蒸汽 进料 冷凝器 塔顶产品 reflux 塔底产品 加热器（再沸器） 上升蒸汽 回流 冷凝器 塔顶产品 Feed Bottom product reboiler Liquid Vapor product Overhead Bottom product reboiler Liquid Vapor product Overhead Bottom product reboiler Liquid Vapor product Overhead Bottom product reboiler Liquid Vapor product Overhead Bottom product reboiler Liquid Vapor product Overhead Rectifying section Stripping /Enriching section Feed plate
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·2)Typical leaching equipment(自学) ·Fig.20.2. 8
8 • 2) Typical leaching equipment（自学） • Fig.20.2
2.PRINCIPLES OF STAGE PROCESSES 1)Terminology for stage-contact plants ·Fig.20.3 9
9 2. PRINCIPLES OF STAGE PROCESSES • 1) Terminology for stage-contact plants • Fig.20.3
V。=y=y Fig.20.3 Material- a a Plate 1 balance diagram for plate column Plate n-1 (Two- component n-1 Plate n system) n+l Plate n+1 VB =VN+I Plate N yo =yN+1 =LN 10 XB=XN
10 n n n n a a a a y V x L x L y y V V 1 1 1 1 − − = = n n n n a a a a y V x L x L y y V V 1 1 1 1 − − = = n n n n a a a a y V x L x L y y V V 1 1 1 1 − − = = n n n n a a a a y V x L x L y y V V 1 1 1 1 − − = = n n n n a a a a y V x L x L y y V V 1 1 1 1 − − = = n n n n a a a a y V x L x L y y V V 1 1 1 1 − − = = n n n n a a a a y V x L x L y y V V 1 1 1 1 − − = = n n n n a a a a y V x L x L y y V V 1 1 1 1 − − = = 1 1 1 1 1 1 + + − − = = n n n n n n a a y V x L x L y y V V 1 1 1 1 1 1 + + − − = = n n n n n n a a y V x L x L y y V V 1 1 1 1 1 1 + + − − = = n n n n n n a a y V x L x L y y V V 1 1 1 1 1 1 + + − − = = n n n n n n a a y V x L x L y y V V b N b N b N b N x x L L y y V V = = = = + + 1 1 b N b N b N b N x x L L y y V V = = = = + + 1 1 b N b N b N b N x x L L y y V V = = = = + + 1 1 b N b N b N b N x x L L y y V V = = = = + + 1 1 Plate 1 Plate n-1 Plate n Plate n+1 Plate N Fig.20.3 Materialbalance diagram for plate column (Twocomponent system)