2014 Software Global Client Conference

Transcription

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2 Simulation Thermodynamics: Best Practices Part II: Assuring the optimal Thermodynamic Methods for your simulation John R. Cunningham NA Technical Support Oct. 2, 2014 Orlando Florida

3 Mobile App: Please take a moment Check into Session by: Select Detailed Schedule Select the specific session Click on Check in Take Session Survey by: Select Detailed Schedule Select the specific session Scroll Down to Survey and Provide Feedback

4 Overview What are the steps prior to a project start, necessary to assure that you are using the optimal property packages and thermodynamic methods for your simulation and design. Part I Which physical properties will impact thermo method selection Adding new components When property estimates are appropriate Part II How composition plays an important part in method selection How characterization and cut selection can impact design When measured data may be absolutely necessary.

5 Parts of a simulation Individual Component Properties (Part I) From Library, Characterization, Estimates Combined Stream Properties Thermodynamic Methods Combined Stream Behavior Thermodynamic Methods Unit Operation Algorithm

6 From Fundamentals to Properties We have seen that reliable pure component properties can be obtained from the simulators libraries, most of the data in PRO/II component libraries originate from either DIPPR or PPDS/NEL in the UK Many non-library component properties can be estimated via group contribution methods available in PRO/II or TDM There is often a need to verify pure component values

7 Important Questions We have pure component properties, what more do we need? Mixture Properties! What are the mixture components, what is the amount of each? Where are the process conditions located with respect to the phase envelope?

8 From Fundamentals to Properties An unambiguous definition of a thermodynamic state may be given by: Temperature Pressure Composition Physical State (ideal gas, vapor, liquid, solid) Method selection decisions can be made on the basis of the above based on both the properties available and those required.

9 Mixtures with limited numbers of components

10 Temperature, C Mixtures with limited numbers of components T-X-Y Plot for PROPANE and PENTANE Composition, Mole Fraction PROPANE, (P = MPa)

11 Mixtures with limited numbers of components

12 Mixtures with limited numbers of components

13 Lets talk about composition Next Question: What is the key composition range? Most cases it s the majority components that impact the calculation On occasion it can be an impurity that matters

14 Lets talk about composition Next Questions: Is the mixture ideal or non-ideal, What type and to what degree is the extent of this non-ideality How do we think about non-ideality? Raoult s Law: Activity coefficient:

15 Lets talk about composition When non-ideality is due to attraction or repulsion between molecules we call it enthalpic (or residual) effects. Attraction results in positive deviations from ideality while repulsion tends to result in negative deviations If the non-ideality is due to molecular size it is know as entropic (or combinatorial) effects

16 Lets talk about composition

17 Lets talk about composition

18 Lets talk about composition

19 Finally different Methods may be good for different phases/properties

20 Considerations in the Critical Region: Simulation Considerations

21 Other considerations in the Critical Region: Property Considerations Heat capacity example, Cp going to infinity

22 Considerations in the Critical Region: Complex Phase Boundaries Phase boundary for water/ethyl benzene: representative of 20 or so more complex phase boundary systems

23 Considerations in the Critical Region: Thermodynamic Model Considerations Liquid Activity models (or Gamma Phi approach) uses pure component vapor pressures to calculate phase equilibria Vapor Pressure is undefined above the critical point Henrys Law is used K Replaced by: i y x i i K i l i sat i y x P i i sat i l vi exp RT P v P i H i, mix P P sat i

24 The upcoming method Selection tree is from: SELECT THERMODYNAMIC MODELS FOR PROCESS SIMULATION : A practical Guide using a Three Steps Methodology, Jean-Charles de Hemptinne, Jean-Marie Ledanois, Pascal Mougin, Alain Barreau, Edition Technip, Paris

25 We have Modified the decision tree below to be more SimSci centric

26 Working through the HC Portion of the Tree Pretty Easy The Yes side of only HC? i.e. H2/nC20 or Methane/Tetralin Our First Solution: I like CEOS where fitted alphas and Kijs are available The No side of only HC; Yes for azeotropy? Next solution: Fitted CEOS or PPR78 (French Version of PR with generated [filled] Kijs)

27 Working through the HC Portion of the Tree

28 Working through the HC Portion of the Tree No for azeotropy? Yes for close to critical? Next solution: Fitted CEOS or PPR78 No for close to critical? No for P>0.1 MPa (1 atm.) Next solution: CEOS or PPR78 Yes for P>0.1 MPa Yes for pseudo? BK10; No, CEOS w/fitted alphas

29 Working through the non-hc Portion of the Tree Pretty Easy again Yes for size asymmetry? Yes or No for P>1 MPa Both answers essentially lead to Polymer thermo solutions No for size asymmetry? No for Water + HC?

30 Working through the non-hc Portion of the Tree No for water + HC? I would like this better as water + organics Low pressure use an activity coefficient approach, high pressures an advanced CE0S Parameters are Absolutely Necessary!

31 Working through the non-hc Portion of the Tree Yes for water + HC? I would like this better as water + organics No for electrolytes? Advanced CEOS Yes for electrolytes? Electrolyte Methods in PRO/II are OLI s Pitzer based method and the e-uniquac MSE which is available for additional fee

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33 Are the Thermo Method and Physical Properties the only fluid characteristics that can impact answer? Yes for defined components (library or user added) No, for Assays and petroleum components Characterization can impact both Assay and Petro Components The number of Cutpoints will impact the separation of Assay streams Upon convergence rerun while increasing the number of cuts till product stream rates stabilize

34 Are your answers really correct? Not in this case! Default cutpoint set is not adequate Always check your answers Table 1: Stripped product stream rates for different cutpoint sets Stream Default cutpoint set Small_cuts cutpoint set Kero Steam Naphtha Kerosene Diesel Gas Oil (AGO) Resid 2443 kg/hr 167 m 3 /hr 105 m 3 /hr 84.9 m 3 /hr 126 m 3 /hr 312 m 3 /hr 5359 lb/hr 1050 bbl/hr 661 bbl/hr 534 bbl/hr 795 bbl/hr 1962 bbl/hr kg/hr m 3 /hr m 3 /hr m 3 /hr m 3 /hr m 3 /hr 1971 lb/hr 1052 bbl/hr bbl/hr bbl/hr bbl/hr 1882 bbl/hr

35 Important Background Information Know what methods are available and what data are present in the property databanks Keep in mind what the intended usage for each method is and when you re stretching those limits Help is available: On line documentation: Reference Manual, Volume 1 Keyword input manual; Component and Thermodynamics volumes Pay the price! Know what information is available. You can call the NA hotline number at any time, you will get an experienced engineer

36 Important Background - Tools Available in PRO/II s GUI (Provision) BVLE Viewing binary Phase Behavior HCURVE Tracking Pure and mixture properties PHASE Important for light ends processing and production Regression via TDM or PRO/II Developing correlation Coefficients Component Properties

37 Important Background - Tools TDM Database Manipulation Creation of library files Loading the various pure component and mixture databases Property Regression Converting data into correlated forms for databank storage for use in simulation VLE Regression Available in TDM 3.0; PRO/II 8.1 (better reliability 3.3 and 8.3) and later Data generated can be permanently stored in user libraries

38 Additional Background - Tools Keyword files UPSTREAM UNIT Matching data for production streams OPTIMIZERS and CONTROLLERS and Calculator Can be used as mathematical solvers Output file Interaction Reprint

39 Kij Input reprint, Important! Default after 8.3!

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41 Related Support, Services, Training > (800) Support > > C:/Program Files (x86)/simsci/proii93/ Manual/ Services > mic-simulation-and-operator-training-simulatorservices/ > Training > > >

42 Review and Summarize I strongly recommend these books! Direct Contact information: john.cunningham@schneider-electric.com (801) Ampla Citect OASyS DNA

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