intro to coco - steven selverston's website · intro to coco steve selverston cwru february...

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...... Intro to COCO

Steve Selverston

CWRU

February 26, 2015

Steve Selverston Intro to COCO

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.. COCO

Free Chemical Process Simulator1

Steady-State and Equilibrium Calculations

Mass Balances

Energy Balances

Vapor/Liquid Equilibrium

Reactors

Steam Table Data

Easy Flowsheet Interface

1www.cocosimulator.orgSteve Selverston Intro to COCO

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.. Running on Apple

To run on Apple, use a Windows emulation tool 2

Parallels

VMWare Fusion

CrossOver Mac

VirtualPC for Mac

VirtualBox

Wineskin Winery

WinOnX

Citrix XenApp

Wine Bottler

BootCamp

2http://www.macping.com/top-10-windows-emulator-for-mac-that-will-allow-convenient-access-of-windows-applications-on-your-mac/


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.. Some Noteworthy Specs

Over 430 Chemicals in Standard Library for TEA

Several Thermo Calculation Methods to Choose From:

Peng-RobinsonRedlich-Kwong-SoaveWilsonNRTLUNIFAC/VLEPrausnitz Chemical Theory


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.. Example Process Flowsheet

Figure : Synthesis of Methanol 3.


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.. Getting Started with COFE

Figure : Empty COFE Flowsheet


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.. Adding A Stream to the Flowsheet

...1 Flowsheet → Configure

...2 Property Packs → TEA

...3 New → Choose Model Set

...4 Add Compounds

...5 Insert a Stream

...6 Double-Click on Stream

...7 Enter Temperature, Pressure, Composition, Flow Rate


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Figure : Calculated Properties


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Figure : Property Packs


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Figure : Use of a Single Water Stream

A huge number of useful calculations can be done by using a singlestream containing, e.g., water. A flow rate must be supplied, butfor intensive properties it doesn’t matter what value is used.


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.. COCO for Steam Tables

Ex: What is the specific volume of water at 250 oC and 1.9 MPa?Ans: Just double-click on the stream, enter the parameters, andread the properties (0.11789 m3/kg).

Figure : Specific Volume of Water (HW 1)


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.. COCO for Steam Tables

Ex: A rigid container contains 1 kg of water at 90 C. If 200 g ofthe water are in the liquid phase and the rest is vapor, determinethe pressure in the tank and the volume of the tank.

Figure : HW 2, Problem 1


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.. Internal Energy

Not all properties are included by default. What if we want theinternal energy of the overall system? Just click on the FlowsheetConfiguration button and add internal energy.

Figure : Modifying the Properties Table


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.. Internal Energy

Now one can see overall internal energy values (e.g., HW 2problem 2).

Figure : Overall Internal Energy in Table.


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.. Unit Operations

Figure : Selecting a HEX from “Insert Unit Operation”)


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.. Simple Heat Exchanger

Figure : Provide Input Parameters (Green means “Solved” or“Complete”)


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Figure : HEX Unit Operation


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Figure : Show GUI for More Editing


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Ex: What will be the final temperature of a cool stream (1 mol/s,300 K) after exchanging heat with a hot stream (0.2 mol/s, 350K), assuming 100 % Efficiency?

Figure : Results of a Simple Simulation

Ans: 310 K


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.. HEX with Phase Change

Ex: What will be the final temperature of a cool stream (1 mol/s,300 K) after exchanging heat with steam (0.2 mol/s, 500 K),assuming 100 % Efficiency?


Ans: 373 K. Why this value?


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Ans: Some water has changed into the vapor phase!


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Figure : Now with 800 K Steam

Ans: Still 373 K, but now a greater fraction of vapor


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.. Practice Problem 1

It is desired to heat up a 10 mol/s stream of water (101,325 Pa,300 K), using a ’hot’ water stream flowing at 1 mol/s. Assumingthe use of a heat exchanger with 100 % efficiency, plot the outlettemperature of the cold stream as a function of the inlettemperature of the hot stream from 350 to 450 K, for six values ofpressure between 100 and 800 kPa.


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.. Solution

Flowsheet → Parametric Study

Choose Inputs

Choose values for From, To, Interval

Choose Output


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.. Parametric Study Results Table

Figure : Parametric Study Results.


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Plot all the data using, e.g., Excel, OpenOffice Calc, Origin orGnuplot.

300

310

320

330

340

350

360

370

340 360 380 400 420 440 460 480

Tem

pera

ture

of

Cold

Out

(K)

Temperature of Hot In (K)

100 kPa200 kPa380 kPa520 kPa660 kPa800 kPa

Figure : Effect of Temperature and Pressure on Heat Transfer.


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.. Vapor-Liquid Equilibrium Problems

Figure : MeOH-Water PX (Koretsky Fig. 8.3)


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.. Methanol and Water Composition

Figure : MeOH-Water TX (Koretsky Fig. 8.4)


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.. Azeotropes- RKS versus UNIFAC

Figure : RKS Fails


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.. Azeotropes- RKS versus UNIFAC

Figure : UNIFAC/VLE Works


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.. Koretsky Ex 2.4. First Law for Closed Systems.

From page 55 of Koretsky textbook:

Steam enters a turbine with mass flow rate of 10 kg/s. Theinlet pressure is 100 bar and inlet temperature is 500 C. Theoutlet contains saturated steam at 1 bar. At steady-state,calculate the power generated by the turbine in kW.


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.. Koretsky Ex 2.4

Solution using COCO Simulator

Use the Expander unit operation

Use a ’test stream’ to find the temperature of saturated steam(about 99.62 C).

Use parametric study to find the isentropic efficiency at whichthat temperature is reached in the output (about 0.712)

Double-click on the expander to see the power


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.. Koretsky Ex 2.4


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.. Koretsky Ex 2.4

Answer: See the calculated Energy Generation


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.. Koretsky Ex 2.10. Thermochemical Data for U and H .

From paage 68 of the textbook:10 mol/s of liquid hexane flows into a steady-state boiler at 25 C.It exists as a vapor at 100 C. What is the required heat input tothe heater? Take the enthalpy of vaporization at 68.8 C to be

∆hvap,68.8 = 28.88 kJ/mol (1)


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.. Koretsky Ex 2.10

Solution strategy in COCO:

Use the HeaterCooler unit operation

In the HeaterCooler GUI, choose “Specify OutputTemperature”

Note: no need to look up the heat of vaporization


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.. Koretsky Ex 2.10


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.. Koretsky Ex 4.9. Generalized Compressibility Charts.

From page 199 of the textbook:Calculate the volume occupied by 10 kg of butane at 50 bar and60 C using the Redlich-Kwong equation and the generalizedcompressibility charts.


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.. Koretsky Ex 4.9

Solution using COCO:

Solve using a single stream!

Use 10 kg/s as the basis flow rate


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.. Koretsky Ex 4.9

(0.0001 m3/mol)(1 mol

0.05812 kg)(10 kg) = 0.019 m3 (2)


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.. Koretsky Ex 7.1. Fugacity in the Vapor Phase.

From page 308 of the textbook: Determine the fugacity and thefugacity coefficient for saturated steam at 1 atm.

Use a single stream

Which property pack to use? Compare several against theresults from the Koretsky textbook.


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.. Ethanol → Isobutanol

Suppose we want to study the heat transfer associated with thisreaction:

2C2H5OH → C4H10O+H2O (3)

From the CRC Handbook of Chemistry and Physics, one finds:

Species ∆hf ,298, kJ/mol

C2H5OH -277.6C4H10O -279.5H2O -285.8


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To predict the reaction enthalpy, we expect that

∆hf ,rxn =∑

hf ,products −∑

hf ,reactants (4)

= (−279.5 + (−285.8))− 2 · (−277.6) (5)

= −10.1 kJ/mol (6)


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.. Chemical Reactions

Lets look at the reaction using COCO simulator (adapted examplefrom 4.)

Simplest reactor is the Fixed Conversion Reactor

Build reaction pack

Specify stoichiometry

We’ll look at isothermal and adiabatic operation


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.. Chemical Reactions

Several reactor models to choose from


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.. Ethanol Conversion


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.. Aside- Flowsheet Customization

Can choose from a variety of icons to customize yourflowsheet diagrams

Right-click on unit → Icon → Select Unit Icon


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.. Ethanol Conversion

If we use standard conditions and a flow rate of 2 mol/s ofpure ethanol, with 100 percent conversion, we get a resultclose to what we predicted

Which thermodynamic model to use?


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.. Thermodynamic Models

Choosing the right thermodynamic model is one of the mostimportant responsibilities of the engineer carrying out processsimulations. One guide, from 5, is shown below.

5Hill and Justice. Understand Thermodynamics to Improve ProcessSimulations (2011).


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.. Thermodynamic Models

Plot from 6.

6Hill and Justice. Understand Thermodynamics to Improve ProcessSimulations (2011).


intro to coco - steven selverston's website · intro to coco steve selverston cwru february...

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