Using aspen plus for process simulation.pptx

In this power point, you will get the brief introduction of aspen plus simulation

1. Using Aspen plus for process simulation 9/29/2022 1

2. Introduction Aspen plus is a computer aided process engineering tool which has been in continual development. Its primary use is to aid in rapid computer simulation of chemical plants that operate at steady state. Aspen plus contains a collection of mathematical models for different kinds of chemical process equipment such as heat exchangers, pumps, compressors, turbines, distillation columns, chemical reactors etc. A mathematical model is essentially a collection of equations which describe the important parts of the equipment and how it works. 9/29/2022 2

3. Cont. Users can select from the pre-made models , enter in the key information about how it is used ( such as the chemicals, temperature, pressure, flowrates etc.), and use the model to compute unknown pieces of information such as (reaction extent, conversions, efficiencies, performance criteria, output conditions, energy usage, and costs). Although some of the models might be simple enough to use by hand individually, the real power of the software is the ability to link together hundreds of models into a process system, thus constructing a large model for an entire chemical plant containing potentially millions of equations . 9/29/2022 3

4. Cont. A user run a simulation using a model , which means to solve the equations in order to find the important unknowns about the process. To do this, aspen plus contains a variety of time-tested algorithms which are useful and often very effective in solving the system of equations, accurately and quickly. Finding the information/inputs to an aspen plus model in literature could be quite tedious , time consuming , and even expensive , especially for simulations with many chemicals. 9/29/2022 4

5. Cont. Fortunately, aspen plus contains a massive data base called aspen properties containing physical property information on literally hundreds of thousands of chemicals. These include: Correlation for heat capacities, thermal conductivities, viscosities etc. Contains parameters for equations-of-state models that connect temperature, pressure, enthalpy, entropy, molar volume, etc. It even has the ability of using certain theoretical methods such as UNIFAC to predict parameters where information is missing or for chemicals which are not in the data base at all, just from the structure of the molecule itself. 9/29/2022 5

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7. Cont. However, it is important to recognize that these are just models, and they can have varying degrees of accuracy depending on the temperature, pressure, and mixture conditions in which they are used. Fortunately, the aspen database also contains a very large amount of experimental measurements for the physical properties, to validate the models. On top of this, Aspen Plus now includes a direct connection to aspen capital cost estimator , which can be used to estimate the capital costs of a piece of equipment with remarkable level of detail. 9/29/2022 7

8. How does Aspen work? Aspen Plus is a collection of modules , where each module contains both mathematical model of a chemical process unit operation and a computer algorithm written specifically to solve it. Consider for example one such module for a flash drum/flash 2 ( which means that it considers two phases- vapor and liquid. ( See figure in the next slide.) 9/29/2022 8

9. Main flowsheet of flash drum 9/29/2022 9

10. Cont. In order to simulate the flush drum, Aspen Plus executes the program associated with it by entering inputs. Once given the inputs, Aspen Plus computes the outputs. The inputs always consists of two things: the model parameters and the contents of the feed streams. For this flash drum case, the parameters and inputs are: 9/29/2022 10 Inputs Parameters Feed condition: 100 Kmol/hr.: 50 % mol water, 50 % methanol Pressure: 1.2 bar Temperature: 50 degree Celsius Operating Temperature : 80 degree Celsius Pressure: 1.2 bar Operating pressure: 0.2 bar Temperature: 50 degree Celsius

11. Three ways how aspen works 1. Sequential modular approach : Processes are solved sequentially one module at a time. 2. The equation-oriented approach: uses a completely different way of solving the flowsheet model. The goal is essentially the same: given a set of model equations and certain known values and model parameters, find all of the unknown variables. However, instead of using a sequence of individual modules, the equation-oriented approach takes all of the model equations from all of the flowsheet units and creates one gigantic system of equations which describe everything in the process. a generic equation solver made to arbitrarily solve systems of nonlinear equations is then used. 9/29/2022 11

12. Cont. 3. Combination: Aspen Dynamics uses the Aspen Plus sequential modular approach to initialize the steady state simulation and the Aspen Custom Modeler equation oriented approach to solve the dynamic simulation. NB: GIGO (garbage in garbage out): Aspen does not understand what people are trying to do. 9/29/2022 12

13. Getting started Steps for simulating with aspen plus Create a new simulation Add chemicals Choose physical properties Insert unit operations and Connect the streams (create the flow of unit operations and/or processes) Enter block parameters and other inputs Successfully execute the simulation Get results from simulations and use that to solve problems 9/29/2022 13

14. Procedures for simulation i . Create a new, blank simulation(look figure below) 9/29/2022 14

15. Cont. ii. Use save us to save your simulation in to a new(.paw) file. 9/29/2022 15

16. Cont. iii. Start by specifying some basic information about the process . On the left panel there are several folders with names “Setup, Components, Methods,” etc. When the Properties tab on the bottom left is highlighted. This is a collection of forms that you have to fill out about the simulation. First, in the Setup | Specifications form , type in the title. In addition, in Units of Measurement, make sure that your Input and Output results are set to MET (metric) See figure in the next slide . These are the default units of measurement and are there for convenience( it can be changed later). 9/29/2022 16

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18. Cont. iv. Choose components. Click on the components folder on the left side of the data browser. Hence you will see a list of chemicals used in your simulation. At the glance, they are empty. you can add chemicals in a number of ways; the most general way is to use the find button at the bottom of the form/ property button . Anyway for the distillation problem, click Find and then do the search for n -hexane. This will search the Aspen Properties database. Notice that two chemicals come up because they both have n -hexane in the title. You can identify the correct one by the full name, chemical formula, molecular weight, etc. 9/29/2022 18

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21. Example: finding hexane and decane 9/29/2022 21

22. Cont. 9/29/2022 22 NB: component ID can be renamed(by double clicking the ID )

23. Cont. v. Now, choose which physical property package we want to use. Physical property packages are collections of data, equations, and models, which describe all sorts of information about the chemicals you have selected. For example, they have equations of state (which relate pressure, volume, amount, and temperature, like the ideal gas law); collections of physical properties like heat capacity, thermal conductivity, latent heats of vaporization; and vapor-liquid equilibria to predict how stuff mixes and separates. 9/29/2022 23

24. Cont. The correct choice of physical property model is absolutely critical for a valid result. To do this, go to Methods | Specifications and choose it from the dropdown box in the Base Method section. The stuff on the right side will fill in automatically. This tells you which equation of state, data set, enthalpy, and volume models this base method will use. 9/29/2022 24

25. Cont. vi. setting up the flow sheet switch to the flow sheet by clicking the simulation tab on the bottom left. Example, let’s add the pump 9/29/2022 25

26. Cont. Finally, we run the simulation Status indicators 9/29/2022 26 Input for the form is incomplete Input for the form is complete No input for the form has been entered. It is optional. Results for the form exist. Results for the form exist, but there were calculation errors. Results for the form exist, but there were calculation warnings. Results for the form exist, but input has changed since the results were generated. Symbol Status

27. Example: synthesis of Sanitizer An ethyl alcohol based hand sanitizer solution is being synthesized in Food Engineering Lab of WKU. The composition of the formulation depends on the volume of the formulation. However, the essential recommendation in the range of ingredients and composition of each excipient used as raw materials for preparation of the sanitizer are: Ethanol (96 %) , glycerol(3 %), hydrogen peroxide(98 %), and water in which all the percentages are volume by volume ratios. The production process is continuous and 10 L of sanitizer is produced every day. Determine the mass fractions of each component after the sanitizer is produced from the following combination of the ingredients at 27 degree Celsius and 1 atm pressure. 9/29/2022 27

28. Solution (the procedures are illustrated as in the pictrures) 9/29/2022 28

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32. After filling the inputs completely, run the simulation . 9/29/2022 32

33. Pressure changing equipment: pump Basically, a pump increases the liquid pressure between its inlet and outlet by Δ P : P 2 = P 1 + Δ P Example : Forty tons per hour of water with the temperature of 20 ◦C has to be pressured from 1 to 6 bar; calculate the electricity requirement of the pump if its efficiency is 70%. Solution: Select the components and appropriate thermodynamic method 9/29/2022 33

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39. Cont. Switch to the simulation environment and prepare the process flow sheet by selecting pump from the menu of pressure changers . Fill the mass fraction, mass flow, T, and P of the feed water 9/29/2022 39

40. Cont. Fill the information for the pump block like the one below 9/29/2022 40

41. Cont. Finally, run the simulation and you should get results like the one in below 9/29/2022 41

42. Flash separator example Example : 100 kmol⋅h -1 of a mixture containing 10, 20, 30, and 40 mol% of propane, n -butane, n -pentane, and n -hexane , respectively, is entering a flash distillation tower. The liquid mole fraction of the mixture is thus 80 %. Calculate the composition of both liquid and vapor phases and the temperature of the vapor–liquid mixture at 7 bar . If the temperature of the flash and the mixture is 97.34 O C 9/29/2022 42

43. Solution 9/29/2022 43

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47. Homework 9/29/2022 47 Consider the reaction of ethanol and acetic acid to produce acetyl acetate and water. Model A CSTR reactor if the temperature in the reactor is 50 ◦C, and pressure is 101 kPa. Both ethanol and acetic acid streams each have the molar flow of 50 kmol⋅h-1, temperature of 20 ◦C, and pressure of 110 kPa. The volume of the reactor is 3 m 3 . Calculate the composition of the product stream if the rate of the reaction is given by power law model.