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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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