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Getting Start Distillation Column Design in ASPEN PLUS

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Getting Start Distillation Column Design in ASPEN PLUS Powered By Docstoc
					Process Design Project
 Steady-State Design in Aspen Plus
 系統設定
需要之軟體套件
  Aspen Plus
Aspen Properties
  Aspen Split
      Steady-State design
• Thermodynamics
• Kinetics
• Process Design
                 若有分相,需選
可以在Unit-sets中設   擇VLLE項
定新的單位表示法
可輸入任意名稱,但
無論如何一定要輸入
輸入系統之成分
                 輸入C、H、O個數後,
                 有同素異構物的可能,
                 選擇你要的


輸入成分之ID

  用Component
  name或Formula
  得到所需物質
有氣相聚合情況
的話,選擇
NRTL-HOC
Wison-HOC…
              Binary Parameters




Missing pairings的估計               輸入熱力學參數
                                  (從文獻或Aspen Properties而來)
T-xy、P-xy與xy圖繪製
T-xy or P-xy plot
  T-xy plot




按下plot wizard可
繪出xy圖
xy plot
選擇Azeotrope
Search 來得到所
有共沸點的資
料
按下        全選所有的系統
Report執   成份
行計算
               選擇VAP-LIQ-LIQ,才
               可預測到異相共沸點
由此可得到
所有的沸點
及共沸點資
料
選擇Ternary Maps繪
出系統中三成分之
RCM圖
按此選項執行
         選擇所需的
         三個成份與
         壓力
                 選擇要繪出
                 之LLE溫度
可用此Toolbar
和滑鼠右鍵來
調整你的
Ternary Map
        Distillation



Objective:
Introduce the distillation model
(RadFrac)
               Introduction

• Interface introduction
• AspenPlus basic operation
• Start with a steady-state simulation
  – A simple distillation of Propane (C3) and
    Isobutane (i-C4)
• Use “Design SPEC/VARY” function
• Set up column length and diameter
• Short-cut design method
User Interface
Define Components (C3 & i-C4)




            可自行改名稱
Properties Setting




               CHAO-SEA
Set up a Column
 Stream




Block
Feed Condition
  點擊兩次進料股 設定
Column Settings
    點兩次蒸餾塔 進行設定
Column Settings (2)
Column Sizing




   新增一個 “Tray Sizing” 功
          能
     Column Sizing
• The typical distance between trays (tray
  spacing) is 0.61m (2 ft)
                 執行



                       當輸入完畢後按此
當右下角出現藍色表示有            兩個鈕執行
結果,
出現黃色表示到達
Decanter不分相或Design
spec到邊界,              Results available
出現紅色表示無法收斂。           Results with warnings
                      Results with errors
Begin Simulation
Tray Sizing Results
Composition Results
 點選蒸餾塔 按右鍵 可看到模擬結果
   Use Design Specs
若欲使塔頂C4 純度降到 0.01,需要多大回流比?
    可用塔內”Design SPecs” 功能
      Use Design Specs
Mole Purity                Select
   0.01                  Component
Use Design Specs (2)
      選擇設計的產品流
Use Design Specs (2)
     新增一個 “Vary” 功能
Use Design Specs (2)
     設定要改變的操作變數與其上下界
Simulation Results
More Complex Distillation System
• Ideal system Non-ideal system (two
  liquid phase could occur)
  – In the column : VLE
  – In the decanter : LLE
• Use different thermodynamic properties
  method in different units
• Heterogeneous Azeotropic Distillation (or
  Ethanol Dehydration)
Heterogeneous Azeotropic Distillation
• Process Study :
  – Vinyl acetate (VAc), water and acetic acetate
    (HAc)
Boiling points of Components & Azeotropes
(UNIFAC model)
Ternary Phase Diagram
      (UNIFAC)
Heterogeneous Azeotropic Distillation
• Feed (229.2 kmol/hr):
   – Vinyl acetate (VAc), water and acetic acetate (HAc)
• Bottom: (122.9 kmol/hr):
   – HAc :94.55 mol%
   – Water : 5.45 mol%
   – VAc : <1 ppm
• Top :  decanter
   – Aqueous phase (0.5 mol% VAc, 98.2 mol% water, 1.3
     mol% HAc)
   – Organic phase (91.0 mol% VAc, 7.6 mol% water, 1.4
     mol% HAc)
Define Components and
Select Property Models
Define Components and
Select Property Models




                 下拉至 ”UNIF-LL”
                與 ”WILSON” 各一次
                 ,則左邊Property
                Methods 會有兩種模
                     式出現
Complete the Flow sheet
   Simulation Setup

Feed                  V1
Simulation Setup (Column)
Simulation Setup (Column)




                 注意:
            點選Properties可改變
            蒸餾塔內的熱物性模式
            我們將第1板至21板選
             用WILSON做運算
Decanter Block
     Decanter
Decanter Block




               注意:
        點選Properties可改變
       Decanter內的熱物性模式
       我們選用UNIF-LL做運算
Split Block (Tee)
     Simulation Setup
                        V3
                        V4
V2
                        V5
Pump Block
             P1
             P2
             P3
Results
   Reactor Modeling



Objective:
Introduce the various classes of
reactor models available.
References:
• Unit Operation Models Reference Manual,
Chapter 5, Reactors
•Web site http://support.aspentech.com/
           Reactor Overview

                   Reactors




Balance Based   Equilibrium Based   Kinetics Based
    RYield            REquil           RCSTR
    RStoic            RGibbs            RPlug
                                       RBatch
Equilibrium Based Reactors



  Objective:
  Detailed introduction to the
  specification and results of REquil
  and RGibbs reactor models.
   Equilibrium Based Reactors
• Equilibrium Reactors
  – REquil
  – RGibbs
• Do not take reaction kinetics into account
• Solve similar problems, but problem
  specifications are different
• Individual reactions can be at a restricted
  equilibrium using a temperature approach
  to equilibrium or molar extent of reaction.
      REquil: Equilibrium Reactor
• Computes combined chemical and phase equilibrium by solving
  reaction equilibrium equations
• Useful when there are many components, a few known reactions,
  and when relatively few components take part in the reactions

         Material
       (Any number)                         Material (Vapor)

     Heat (Optional)                        Heat (Optional)




                                            Material (Liquid)


March 25, 2011                Slide 63               Reactor Modeling with
                                                              Aspen Plus
         REquil: Specifications
• Specified on the REquil Input Specification
  sheet the Reactor Conditions:
  – Specify two of
     • Temperature
     • Pressure
     • Vapor Fraction
     • Duty
  – Valid phases
     • Vapor-Liquid
     • Vapor-Only
     • Liquid-Only
     • Solid-Only
     • NOT Vapor-Liquid-Liquid
REquil: Specifications   (Continued)
              REquil: Equilibrium
• Calculates equilibrium constants from Gibbs energy
• Can restrict equilibrium by specifying one of:
   – Molar extent of the reaction
   – A temperature approach to chemical equilibrium

• Temperature approach is the number of degrees above the reactor
  temperature at which chemical equilibrium is determined.

                  TEquil=TR + T
               REquil: Reactions
• Use the REquil Reactions sheet to define the reaction stoichiometry.
• By default REquil assumes that reactions will reach equilibrium
  (Temperature approach = 0o).




                                Slide 67
            REquil: Results
• Summary
  – Outlet temperature and pressure
  – Heat duty
  – Net heat duty
  – Molar vapor fraction
• Mass, mole and enthalpy balance
• Equilibrium constants. Not reported for
  reactions where restricted molar extent
  specified.
REquil: Results   (Continued)
Kinetics Based Reactors



 Objective:
 Detailed introduction to the
 specification and results of
 RCSTR, RPlug and RBatch
 reactor models.
                  Kinetics Reactors
• Kinetic reactors
   – RCSTR
   – RPlug
   – RBatch
• Used to study reactions in model detail
• Require
   – Some geometric details of the reactor
   – Details of the reaction stoichiometry and
     kinetics
 March 25, 2011      Reactor Modeling with Aspen Plus   Slide 71
     Kinetics Reactors: RCSTR
• RCSTR performs a mass and energy balance around an
  ideal continuous stirred tank reactor with known reaction
  kinetics
   – Perfect Mixing is assumed on both Macroscopic and
     Microscopic levels
                                    Heat (Optional)
        Material (Any Number)




             Heat (Optional)         Material
         RCSTR: Specifications
• Specified on the Setup Specification sheet the:
   – Reactor Conditions
      • Pressure and either Duty or Temperature
   – Holdup specifications:
      • Valid Phases to consider in RCSTR calculations
           – Vapor Only (Default)
           – Liquid Only
           – Vapor-Liquid
           – Vapor-Liquid-Liquid
           – Liquid-Free Water
           – Vapor-Liquid-Free Water
      • Volume or Residence Time for Reactor holdup
RCSTR: Specifications   (Continued)
       RCSTR: Phase Volume
• In multi-phase reactors RCSTR calculates the volume
  of each phase, using phase equilibrium results:
                      Vi f i
          VPi  VR
                     V j f j


Where
  Vpi =     Volume of phase i
  VR =      Reactor Volume
  Vi =      Molar volume of phase i
  fi =      Molar fraction of phase i
      RCSTR: Phase Volume
• Override this calculations by specifying:
  – The volume of a phase directly
  – The volume of a phase as a fraction of the
    total reactor volume
  – Residence time
  RCSTR: Phase Volume            (Continued)



• Use the Setup Specifications sheet to
  define how the phase volume/residence
  time is going to be specified.
     RCSTR: Residence Time
• If the reactor volume is specified then the
  residence time is calculated as follows:
  Overall Residence time

                 VR
          RT 
               F * f iVi

  Phase Residence time
                    V pi
          RTi 
                  F * f iVi
 RCSTR: Residence Time                         (Continued)



   Where
   RT =     Overall residence time
   RTi=     Residence time of phase i
   VR =     Reactor volume
   F =      Total molar flow rate (outlet)
   Vpi =    Volume of phase i
   Vi =     Molar volume of phase i
   fi =     Molar fraction of phase i

• Specified Phase volume or phase volume fraction is
  used instead of calculated if given.
         RCSTR: Reactions
• Can handle kinetic and equilibrium type
  reactions
• Specify reactions using a Reaction Set ID
  on the Setup Reactions sheet.
      RCSTR: User Routines
• User kinetics through the Reaction Set ID
  – Calculate the reaction rates for each
    component
              RCSTR: Results
• Summary
   – Outlet Temperature
   – Heat Duty
   – Net Heat Duty
   – Total Reactor Volume,
   – Volume of each of the phases present including salts
   – Condensed Phase Volume.Volume occupied by the
     condensed phases (liquid and solid) present in the
     reactor
   – Total Reactor Residence Time
   – Residence time of vapor and condensed phases
          RCSTR: Results
• Material and energy balances around the
  block
            RCSTR: Workshop
Objective: Determine the outlet flow rate of
 ethyl-acetate
            FEED                                         PRODUCT

 Pressure = 1 atm
 Saturated liquid
 736.160 kmol/hr water
 218.087 kmol/hr ethanol
 225.118 kmol/hr acetic                          RCSTR
   acid
                           Volume = 21,000 L
                           Temperature = 60 C
                           Pressure = 1 atm
                 Use the NRTL physical property method

                   Filename: WK3-RCSTR.BKP
            RCSTR: Workshop
• Formation of Ethyl-Acetate is modeled as an equilibrium
  reaction:
       Ethanol + Acetic-Acid  Ethyl-Acetate + Water

  where K= 3.8 or lnK = 1.335

• Use the Power Law reaction type. The equilibrium
  contact is based on molarity composition.

• If this reaction were modeled as 2 kinetic reactions
  would the results be the same?
       RCSTR: Workshop                       (Continued)



• Use the Powerlaw reaction type. The equilibrium contact
  is based on molarity composition.

• What is the outlet flow rate of Ethyl-Acetate?

• If this reaction were modeled as 2 kinetic reactions
  would the results be the same?
        RPlug: Kinetics Reactors
• Performs a mass and energy balance around an ideal
  plug flow reactor.
• Assumes perfect mixing in the radial direction
• Assumes no mixing occurs in the axial direction
• Optional coolant stream can also be specified
                                           Material Coolant
                                           (Optional)

                                            Material
   Material



Material Coolant
(Optional)
         RPlug: Specifications
• Use the Setup Configuration sheet to specify
   – Reactor tube length
   – Reactor tube diameter
   – Number of tubes (optional)
   – Valid Phases
      • One, two or three-phases
      • Vapor-Only is the default
• Use the Setup Pressure sheet to specify the pressure
  drop across the reactor.
• Additional input depends on the reactor type chosen.
RPlug: Specifications
        RPlug: Reactor types
• There are 5 reactor types available
  – Reactor with Specified temperature
  – Adiabatic reactor
  – Reactor with constant coolant
  – Reactor with co-current coolant
  – Reactor with counter-current coolant
   RPlug: Specified temperature

• Specify constant reactor temperature or temperature
  profile (linear interpolation between points).
• Duty is integrated along the length of the reactor.
RPlug: Constant Coolant Temperature

• Specify
   – Coolant temperature
   – U (Coolant - Process stream)
• Duty is integrated along the length of the reactor
• Temperature of the process stream is determined from
  the energy balance.
    RPlug: Co-Current Coolant
• Specify
   – External coolant stream
   – U (Coolant - Process stream).
• Duty is integrated along the length of the reactor
• Temperature of the process and coolant stream are
  determined from the energy balance.
RPlug: Counter-Current Coolant
• Specify
   – External coolant stream
   – Coolant outlet temperature, or molar vapor fraction
   – U (Coolant - Process stream)
• Duty is integrated along the length of the reactor
• Temperature of the process and coolant stream are
  determined from the energy balance.
      RPlug: Adiabatic Reactor
• No required specifications
• Temperature is calculated at each axial position based
  on the enthalpy balance.
RPlug: External Coolant Stream
• Can model reactor with co-current or counter-current
  coolant stream
• Counter-Current
   – Calculates coolant inlet temperature
   – Overrides specified inlet coolant temperature
   – Use design spec to manipulate coolant exit
     temperature or vapor fraction to set inlet temperature
   – Temperature cross-over allowed
• Use different physical property method for coolant
             RPlug: Reactions
• Can handle kinetic reactions
• Cannot handle equilibrium reactions
• Specify reactions using a Reaction Set ID on the Setup
  Reactions sheet
        RPlug: Residence Time
• The total residence time is calculated by integration.
• If the volumetric flow rate does not change:
                           Volume of Reactor
       Residence Time =
                          Volumetric Flowrate
   – A no-slip condition is assumed when two phases exist.
   – No liquid holdup is considered.
   – Volume available to the reacting phase is determined
     using the weighted molar volume for the vapor and
     liquid at each integration interval.
          RPlug: User Routines
• User kinetics through the Reaction Set ID
   – Calculate the reaction rates for each component
• Heat Transfer
   – Calculate the heat transfer rates per unit reactor wall
     area at any point along the reactor
• Pressure drop
   – Calculate the pressure drop for both the process and
     coolant streams at any point along the reactor.
               RPlug: Results
• Summary
   – Heat Duty
   – Reactor Minimum Temperature
   – Reactor Maximum Temperature
   – Residence Time (average for all phases present in
     the process stream)
• Material and energy balances around the block
• Profiles results versus reactor length
   – Process stream conditions
   – Coolant stream conditions
   – Property set properties
RPlug:Temperature Profile
RPlug: Molar Composition
         Profile
                RPlug: Workshop
Objective: Determine catalyst activity for a plug-flow
  reaction involving chlorine and propylene
  T = 200 C
  P = 2.027 bar
  Cl2 = 0.077 kmol/hr




                                      Reactor length = 7.62 meter
                                      Tube diameter = 50.8 mm
                                      U = 5 Btu/hr-sqft-R
  T = 200 C
                                      Coolant temperature = 200 C
  P = 2.027 bar
                                      Pressure drop = 0
  C3H6 = 0.308 kmol/hr
                   Use the IDEAL physical property method
                   Filename: WK4-RPLUG.BKP
         RPlug: Workshop                    (Continued)



Part A
• Reactions and Power Law kinetic expressions:

                Cl2 + C3H6  C3H5Cl + HCl
         R(1) = 1.5e6*EXP(-27200/RT)*[Cl2]*[C3H6]

                   Cl2 + C3H6  C3H6Cl2
          R(2) = 90.46*EXP(-6860/RT)*[Cl2]*[C3H6]

• Kinetic parameters in ENG Units
• Reactions take place in the vapor phase
       RPlug: Workshop                      (Continued)
Part B
• Add coolant inlet and outlet streams. The water coolant
  countercurrent flow is 400 lb/hr and is at 80 C and 1 atm.
  You want the outlet coolant temperature to be 90 C.
  What is the inlet coolant temperature?

Part C
• Use a design specification or run a series of runs “trial
  and error” to find the required coolant flow rate to match
  the problem specifications of 90 C outlet and 80 C inlet
  temperature.
  What is the required coolant flow?

				
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