Hysys Manual

ENG1010 HYSYS MANUAL AND PROBLEMS

Department of Chemical Engineering Monash University First issued in 2010; Based on HYSYS Version V7.0

HYSYS HANDY HINTS 1. When a unit operation is fully specified, the bar at the bottom of the form turns green. If it is red, the text in the bar will tell you what you need to do. 2. If HYSYS will not calculate, it may be in ‘holding mode’. If it is, then the red light on the toolbar will be on. To get HYSYS running again, click on the green light

3. To change components or reaction details, click on the enter basis environment button. 4. Unless otherwise specified, use the PRSV property package. 5. If you are asked to create a stream containing say 100 kg/hr of water, and 30 kg/hr of sucrose, then the easiest way is to setup one stream. Double click on mass flow, set the composition basis to mass flows, and then enter 100 for water and 30 for sucrose. The same approach can be used to specify component mole flows in a single stream. 6. Unless otherwise specified, the pressure drops are set to zero. 7. When entering reactions, the stoichiometric coefficient is negative for reactants and positive for products. When the equation is balanced, the balance error will be 0. 8. Do not enter extra information into HYSYS. This will cause errors. Start at the front of the flow diagram and work your way through the problem. 9. Make sure you save the files regularly. 10. See also “HYSYS Tips and Common Errors” on the next page.

HYSYS Tips and Common Errors Terminology: • • • • • •

Turbine = Expander Condenser = cooler (if there is only one stream) Condenser = heat exchanger (if there are two streams) Boiler = heat exchanger (if there are two streams) Combustor = Conversion reactor Adiabatic: means no energy exchange with the surroundings/environment (either put in an energy stream and set its value to zero or simply do not put in an energy stream)

Saturated Vapour – Saturated Liquid:

• •

To indicate to HYSYS that a stream is saturated liquid: set vapour/phase fraction = 0 To indicate to HYSYS that a stream is saturated vapour: set vapour/phase fraction = 1 (Otherwise do not enter any information under vapour/phase fraction)

Reactors:

• • •

In a conversion reactor: Conversion C0 is in percentage. Cannot find a reaction to add to the reactor? Either you have not ADDED one to the Fluid Property package or you have not linked the reaction set to the Fluid Property package. Your reactor is not solved, although you have added the reaction set and your defined reaction is READY? Maybe you have added one or more empty reactions, so you have more than one reaction in your reaction set, some of which are not defined. Go back to your reaction environment and delete the extra reactions and only leave the one(s) which should be applied.

Pressure Drop:

•

For Heaters, Cooler and Heat Exchangers: You can assume that pressure drop = 0 for a heater or cooler or for both streams in a heat exchanger. Unless pressure drop is given or both inlet and outlet stream pressures are given.

•

For pumps, compressors, valves, expanders (turbines): Do NOT set pressure drop to zero. A pump increases the pressure of a liquid (by doing work on the liquid). A compressor increases the pressure a gas (by doing work on the gas). In a valve there will be a pressure decrease. An expander decreases the pressure of a gas, whilst extracting work from the gas.

Air: Only use AIR as a component when there is no reaction. If there is a reaction, use air as 21mole % Oxygen and 79 mole % nitrogen.

Adding a heat exchanger: If you are asked to add a heat exchanger to an existing process flow diagram, sketch it on paper first before you start making changes. Otherwise you may become totally confused and not be able to revert to your original process flow diagram.

Common Errors:

• • •

All data not input. Check each stream carefully Conversion entered as a fraction rather than a percentage (entering 1 will given a 1% conversion – hence very little reaction) HYSYS calculator is on HOLD (red traffic light on). This happens (a) when to go back in to the Simulation Basis Manager (to enter and extra component or reaction) – which case just press the green traffic light button. (b) when you have a Consistency error – in this case you must find the source of your error before pressing the green traffic light button. Consistency error means you have given HYSYS conflicting information for a stream’s condition. Careful checking required.

Introduction to HYSYS In designing and analysing engineering systems the calculations soon become too complex and involved to be readily solved by hand calculation. This is why most engineers make use of simulation packages. Throughout this semester, you will be using one of the common simulation packages, HYSYS, to aid in the complex calculations. The purpose of HYSYS is to simulate, or predict how a process is going to work. In particular, HYSYS allows us to determine what effect changing plant operating conditions will have on the overall process. This allows for optimisation of the plant’s performance without having to trial these conditions on the real equipment. Obviously this is an important part of engineering. Throughout this semester, we will be using HYSYS as a tool for simulating a range of engineering operations. This will enable us to expand on the work covered in lectures, as it allows you to simply estimate the performance of a plant without having to do long and tedious hand calculations. By the end of the semester, you should be able put together a entire process flow diagrams for common systems such as a gas turbine, refrigeration plant or combined cycle power generation plant. You will also be able to interrogate the process flow diagrams; in other words, you will be able to change operating conditions to see what effect they have on the performance of the process. The purpose of this laboratory manual is to aid in the setting up of simple unit operations within HYSYS.

Starting HYSYS V7.0 Simulation Package All the computers in the Engineering computer laboratory HYSYS V7.0 is installed. Click on Start, then select “All Program” button Select program name “ASPENTECH” that will lead you to several options. Select “Process Modelling V7.0” and then go to “Aspen HYSYS” and then click on “ASPEN HYSYS” in the next window.

Setting up HYSYS Process MODEL STEP 1. Setting up the simulation. Whenever you use HYSYS, there are a number of steps which need to be taken in order to get things working. These steps are outlined below. Firstly, Click File_New_Case This starts a new file and opens the simulation manager. The screen will look like:

Fig 1 The next task is to add components. Click on the Add button.

Fig 2 Click in the Match box, and begin typing the name of the component to search for a component. For example, type nitrogen (or N2), and then double click nitrogen to add it to the list of current components. It should appear in the box on the left hand side of the screen. Repeat for hydrogen and ammonia. When completed, click on the x on the top right hand side of the form. You will be taken back to the simulation basis manager window (see Fig 1). The next step is to add a fluid property package. Click on the Fluid Pkgs tab. Then click on the Add button.

Fig 3 Scroll through the list of fluid packages and click on PRSV. Do make sure that the selected property package is associated with the component list in which you have entered all the

components. When completed, click on the X on the top right hand side of the form. You will be taken back to the simulation basis manager window (see Fig 1). If you don’t need to enter reactions, click on Enter Simulation Environment. Setting up a flowsheet – a mass balance over a mixer. Once you have entered the property package and components (as described above), you need to start drawing the process block diagram. We will start by adding three streams, one containing hydrogen, one containing nitrogen, and another containing a mixture of nitrogen, hydrogen and ammonia. This would represent a typical feed to the reactor in an ammonia plant. For this you need to enter these three components (nitrogen, hydrogen and ammonia) in your component list when setting up your HYSYS simulation basis manager (Figure 2). You should see a large toolbar which contains all of the unit operations available within HYSYS. This is shown in Fig 4. It you cannot see the toolbar, press F4, and it should appear. Firstly you need to enter a material stream. Click on the blue arrow in the toolbar. Then click on the flowsheet where you want to put this stream (as shown in Fig 8). Double click on the blue arrow. This opens the properties form for the stream (Fig 5).

A

Fig 4.

Fig 5.

Under stream name, type in the name for this stream. For example, this could be S1. Under temperature, enter 300 and under pressure, enter 100000. For a mass balance on a mixer, the temperature and pressure are not important, but HYSYS likes to know them anyway. Under mass flow, enter 1000. Note that small window with unit will appear when you enter any process condition indicating units. All default units are set to SI units. (You can change the default unit to other units via the Program tab “Tools_Preference_Variables”. However in this course we will use SI unit as the default unit.) Now, double click on the 1000 entered for mass flow. This opens the composition form.

Fig 6 Enter 0.76 for nitrogen, 0.16 for hydrogen, and 0.08 for ammonia. Click OK. You will notice that the yellow bar at the bottom of the properties form (Fig 5) has turned green. This means that the feed stream is completely defined. Close this form by clicking on the X in the top right corner of the form. Try entering two more streams as follows. The procedure is identical to that described above. Stream

Temp

Press

Mass

Mass

Mass

Mass

°C

kPa

Flow

fraction H2

fraction N2

fraction NH3

S2

300

100000

150

0

1.0

0

S3

300

100000

30

1.0

0

0

Once you have done this, then we are ready to add the mixer. Click on the mixer (marked A in Fig 4. It is the button above the Tank + stirrer). Click on your flowsheet where you want to add the mixer. Now, double click on the mixer to open the properties form for this item. The form is shown in Fig 7.

Fig 7 Click on the inlets box. This lists the streams available as inlets to the mixer. Select S1; repeat for S2 and S3. Now the mixer should have the three feeds, and it is a simple matter to add the outlet stream. Click on the outlet box, and type S4. Close this form and you should notice that the output stream S4 has been added to the flowsheet, and it should be dark blue. This means that everything is known about this stream. The flowsheet should look like:

Fig 8

Double click on S4, and look at the properties. Not surprising, the mass flowrate of stream 4 is 1180 kg/hr. This is what we would calculate using an overall mass balance. Now double click on the 1180 (mass flow) to open the composition form for this stream. You can see that S4 contains 77.12 % nitrogen, 16.1 % hydrogen and 6.78 % ammonia. These numbers are calculated using the component mass balances. The power in HYSYS is the ability to simply change conditions, and have the calculations updated instantly. Try changing the flowrate of S3 to 50 kg/hr. This increases the hydrogen content of S4 to 17.5 %.

REACTORS Entering Reactions. Start a new simulation, and nitrogen, hydrogen and ammonia as the components, and enter PRSV as the property package. Close the form, but BEFORE you click Enter Simulation Environment, you need to enter the reactions for the reactor. The steps for doing this are outlined below. Click on the Reactions tab in the simulation basis manager. You should now see the first window and when you select the “Add Rxn” Tab the 2nd window will appear with different options for reaction. Firstly click Add Rxn. This will give us a list of reactions. We will start with the Conversion Reaction as the example we will be doing is a conversion reaction.

Fig 9

Fig 10

Fig 11. Now, to add a component, click on the arrow of the drop down box. Select nitrogen. Repeat for hydrogen and ammonia. The reaction we are trying to model is:

N 2 + 3H 2 → 2 NH 3 In HYSYS, reactants are treated as having a negative stoichiometric coefficient, whilst products have a positive stoichiometic coefficient. Thus we enter -1, -3 and 2 as the stoichiometric coefficient for nitrogen, hydrogen and ammonia respectively. The form should now look like:

Fig 12. Click on Basis. This is where we enter the conversion for the reaction. We will base the conversion on nitrogen, so we will leave this as our Base Component. In the box Co, type 50. This will assign a conversion of 50 % for this reaction.

Fig 13. Close the Conversion Reaction form, as well as the small reactions form (Fig 10) if it is still open. You should be back in the Simulation Basis Manager (Fig 9).

Fig 13-A Now Click on “Reaction Set” Tab. Then “Add Set” tab Click on Add to FP then another form opens; click Add Set to Fluid Package. Now click Enter Simulation Environment. Now you are ready to add this reaction in your process model. Firstly you need to enter a material stream. Click on the blue arrow in the toolbar. Then click on the flowsheet where you want to put this stream (as shown in Fig 16). To add a reactor, click on the general reactors button on the toolbar. This pops up another small toolbar (Fig 15). Click on conversion reactor. Click on the flowsheet where you want to add the reactor.

Fig. 14

Fig 15

Fig. 16

Double click on stream 1 to open the properties form (Fig 5). Change the stream name to feed. Set the temperature to 300° C, the pressure to 10000 kPa, and molar flow to 100 kgmol/hr. Double click on the 100 entered for molar flow. This opens the composition form. Enter a mole fraction of 0.25 for nitrogen, 0.75 for hydrogen and 0 for ammonia. Note: if you double click on mass flow instead of mole flow, by default you will be entering mass fraction. You can however change the basis to mole fraction by clicking on the button in Composition basis. Click OK. You will notice that the yellow bar at the bottom of the properties form has turned green. This means that the feed stream is completely defined. Close this form, and double click on the reactor. This opens the properties form for the reactor.

Fig 17. Click on the inlets box. This is where the feed stream is entered. Select feed using the drop down box. Click on vapour outlet. This is where we enter the vapour product stream. Type Vprod. Click on liquid outlet, and enter L-prod as the liquid product stream. HYSYS will automatically place any liquid products in the L-prod stream, whilst the vapour products are placed in the V-prod stream. In the Energy box, type q-r. Click on the reactions tab. This is where we assign the reactions for this reactor. Click on the arrow on the reaction set drop down box (Fig 18), and select Global rxn set. Close this form. Double click on the v-prod stream. Set the temperature to 300° C (the reactor is isothermal, so the outlet temperature is the same as the inlet temperature). HYSYS can now calculate the performance of the reactor. Look at the composition of this stream. Do the numbers make

sense? Double click on the L-prod stream. You can see the flowrate is 0. This is not surprising, since nitrogen, hydrogen and ammonia are gases under these conditions.

Fig 18. Try changing the conversion of the reactor. Double click on the reactor, click on the reactions tab, and then click on the conversion % button. Change Co to say 80. Close the form, and look at the composition of the V-prod stream. It is also possible to set-up a reactor as adiabatic (no heating or cooling). This causes a large increase in temperature, as the reaction is exothermic. You can try this for the reactor described above as well. Simply click on the temperature in the exit from the reactor (V-prod) and press delete. Then double click on the reactor, and remove the energy stream. HYSYS should now solve. What is the reactor outlet temperature now?

The CSTR Start a new HYSYS file, enter sucrose, water, carbon dioxide and ethanol as components, and select the general NRTL property package. Follow the instructions given for a conversion reactor until you get up to entering the reaction type (Fig 10). Now we will select a kinetic reaction. The following form appears:

Fig 19 The reaction occurring is sucrose + water = ethanol + carbon dioxide:

C12 H 22O11 + H 2O → 4C2 H5OH + 4CO2 This is a fermentation reaction, which is used to produce beer (ethanol is of course alcohol). Note that for a kinetic reaction you need to have data for Activation energy and preexponential factor. You need to enter them in the “Parameters”. Add the components and stoichiometry (-1 for sucrose, -1 for water, 4 for ethanol, 4 for carbon dioxide). Under forward order, type 1 for sucrose and 0 for water. Under reverse order, type 0 for ethanol and 0 for carbon dioxide. This tells HYSYS that the reaction rate only depends on the sucrose concentration. Click on the basis tab, and set rxn phase to combined liquid. Click on the parameters tab, and under forward reaction, enter 1e6 for A and 5e4 for E. These parameters tell the simulation how fast the reaction is. Close the form (and the reactions form if still open). Click on Add to FP (Fig 13A). Then another form opens; click Add Set to Fluid Package. Click on Return to simulation environment. If you receive a warning message “Some of the binary coefficients for this fluid package’s components are unknown. They will be set to zero”, just click OK.

Set up two feed streams: one containing water, the other sucrose (both at 10° C). The molar flowrate of sucrose is 100 kgmol/hr, and water is 1000 kgmol/hr. The pressure of each stream is 110 kPa. Set the composition of the water stream to be pure water, and the sucrose stream to be pure sucrose. Click on the CSTR icon on the unit ops toolbar (Fig 4) – it is the one which looks like a tank with a stirrer. Click on the place you want to add the CSTR, and then double click on the CSTR. This will open the properties form for this reactor.

Fig 20 Under inlets, enter the two feed streams (water and sucrose). Like a conversion reaction, HYSYS produces a liquid and vapour product. Enter the name of these streams (e.g. V-out and L-out). In the energy box, enter q-cstr. Click on the parameters section. This is where we enter the volume. Enter 20 m3 for the volume, and change liquid level to 90%. Click on the reactions tab, and under reaction set, select global rxn set. Close the form. The CSTR is now ready to run. Set the temperature of stream l-out to 10° C, and the CSTR will calculate. Look at the flowrate and composition of streams L-out and V-out. Notice that most of the CO2 produced is in the V-out stream. To view the conversion, double click on the CSTR, select the reactions tab, and results section. Try changing the volume of the CSTR, and see what effect this has on the conversion.

Cooling of the CSTR is critically important in many processes. The brewing industry would not exist if we could not adequately cool the reactors. Double click on stream l-out, and delete the temperature specification. Then double click on the CSTR, and remove the energy stream (design tab, connections section). HYSYS will now assume that there is no cooling (reactor is adiabatic), and calculates the outlet temperature to be 45.7° C. Such a temperature would ruin the beer which is being produced.

HEAT TRANSFER There are two ways to implement heat transfer in HYSYS. Firstly, one can use a heater or cooler:

Add a stream to your flowsheet. Now, to heat up a stream, add a heater, and double click on this unit.

Fig 19 Enter the inlet and outlet streams. You also need to enter an energy stream – lets say q-heat1. Click on parameters, and enter a pressure drop of say 0 kPa. Now we either specify the duty of the heater, or we can specify the outlet stream temperature. We will specify the temperature. Close this form, and specify the temperature in the outlet stream, and HYSYS

will calculate the duty of the heater. Double click on the heater, and click on the parameters section. You will see that the duty has been calculated for this heater. If you want to specify the duty, then remove the temperature specification of the stream exiting the heater. Then double click on the heater, click on the parameters section, and specify the duty. Now the heater exit temperature will be calculated. A similar procedure is used for the cooler. The second heat transfer option is a heat exchanger. In this instance, there are two inlet and two outlet streams. Basically, one hot stream is used to heat up a cold stream (the cold stream is thus cooling down the hot stream). Add two streams to your flowsheet, and add a heat exchanger (the icon beneath the cooler). Double click to open the properties form.

Fig 20 You need to specify that one stream enters and leaves the tube side, whereas the other stream enters and leaves the shell side of the shell and tube heat exchanger. Don’t worry about which side to put each stream – this doesn’t affect the energy balance. Click on the parameters section, and specify a pressure drop of 0 kPa in both the shell and tube sides. Close this form. Now, to calculate an energy balance, we need to know one of the outlet temperatures. Specify the outlet temperature of one stream, and HYSYS will calculate the temperature of the other.

Heat Exchanger Example. Set up a problem using the Peng Robinson Fluid package, with components oxygen, nitrogen, carbon dioxide, and water. We will look at the recovery of heat from the flue gas of a natural gas burner. In the flowsheet, add a hot-gas stream (800 °C, 200 kPa, 3100 kgmol/hr). The composition of this stream is 76.5 mol% nitrogen, 13.9 mol% oxygen, 6.4 mol% water, 3.2 carbon dioxide). Add a water stream (30 °C, 1000 kPa, 20000 kg/hr of pure water). Add a heat exchanger, and put the hot gas on the tube side, and the cold water on the shell side. Enter two streams exiting the heat exchanger, cold-gas, and steam. Set the pressure drop in the shell and tube sides to be 0 kPa. The water will cool the hot gases down to 270 °C (specify the temperature of the gases exiting the exchanger). You can see that the water is being heated up to generate steam. Determine the outlet steam temperature. Now double click on the heat exchanger, and click on the parameters section of the design tab. You can see that UA for this exchanger. So if we know the overall heat transfer coefficient, we can calculate the heat exchanger area.

PUMPS, COMPRESSORS AND TURBINES The icons below are for: 1. The pump; 2. The expander (turbine); and 3. The compressor

Pumps are used for liquid streams, and expanders and compressors are used for gas streams. Add a water stream to your flowsheet. Now, to increase the pressure (pump) the liquid, add a pump, and double click on this unit.

Fig 21 Enter the inlet and outlet streams. You also need to enter an energy stream – lets say q-pump. This represents the power to run the pump. Now we either specify the energy of the pump, or we can specify the outlet stream pressure. We will specify the pressure. Close this form, and specify the pressure in the outlet stream, and HYSYS will calculate the duty of the pump. Note Hysys also calculates the temperature of the stream exiting the pump. If you want to specify the pump duty, then remove the pressure specification of the stream exiting the pump first. The procedure for setting up a compressor is virtually identical to the pump, except it is used for gas streams instead of liquid. An expander (turbine) is used to expand (decrease the pressure) of a gas stream. The turbine uses the expansion of the gas to produce power. Add an air stream to your flowsheet, and set the inlet conditions to 10,000 kPa and 400 °C. Now, to obtain power from this stream, add an expander, and double click on this unit.

Fig 22 Enter the inlet and outlet streams. You also need to enter an energy stream – lets say q-turb. This represents the power that is produced by the turbine. Now we either specify the energy of the turbine, or we can specify the outlet stream pressure. We will specify the pressure. Close this form, and specify the pressure in the outlet stream to 200 kPa, and HYSYS will calculate the duty of the turbine to be 279 kW. Note Hysys also calculates the temperature of the stream exiting the expander (the temperature of the gas drops as it is expanded). If you want to specify the turbine duty, then remove the pressure specification of the stream exiting the expander first.

SEPARATORS In its most basic form, a separator is used to separate a stream into liquid and vapour fractions. Separators can also be used to calculate the liquid-vapour equilibrium conditions for a single stream which undergoes change in T or P, or for the mixing of multiple streams. In this example, there will be drop in pressure for the liquid stream after it enters the separator. This causes some of the liquid to evaporate. Start a new HYSYS file, enter propane and butane as components, and select the Peng Robinson property package. Enter a feed stream containing 50 mol% propane and 50 mol% nbutane at 20 °C. The pressure is 600 kPa, and the molar flow is 100 kgmol/hr. Click on the

separator unit operation, and add it to the worksheet. Double click on the separator to open the properties page.

Fig 23 Enter the feed as an inlet stream, and enter the name of the vapour outlet and liquid outlet (lets assume that they are called vap and liq). Click on the parameters section, and change Inlet deltaP to 200 kPa. Then close the properties form and have a look at the vapour and liquid product streams. The vapour stream is rich in propane (mole fraction propane = 0.774) However, the amount of vapour produced is only 5.6 kgmol/hr. It is also clear that these streams have been cooled by the evaporation within the separator. HYSYS also has the ability to add energy to a separator. Double click on the separator, and add an energy stream, Qsep (in the connections section of the design tab. Now we can either specify the energy flow to the separator, or we can set the outlet temperature. Double click on the vap stream, and set the temperature to 20 °C (an isothermal flash). Now you can see that at the higher temperature we have produced 57.25 kgmol/hr of vapour. However, the purity of the product is lower (mole fraction propane = 0.629).

Appendix: The HYSYS Unit Operations. 1. The mixer Task

Tab

Section

Action

Enter inlet and outlet

Design

Connections

Type stream name or select it

streams

from the drop down box

2. The Reactor. Task

Tab

Section

Action

Enter inlet, outlet and

Design

Connections

Type stream name or select it from

energy streams Select reactions for the

the drop down box Reactions

Details

reactor View or enter the duty for

Select global rxn set in reaction set box

Design

Parameters

the reactor (non adiabatic)

EITHER a. Set duty and exit temp is calc; or b. Set exit temp and duty is calc.

3. Heat Transfer a. Heater / Cooler Task

Tab

Section

Action

Enter inlet, outlet and

Design

Connections

Type stream name or select it from

energy streams

the drop down box

Set pressure drop

Design

Parameters

Type in pressure drop

View or enter the duty

Design

Parameters

EITHER a. Set duty and exit temp is calc; or b. Set exit temp and duty is calc.

b. The Simple Heat Exchanger Task

Tab

Section

Action

Enter tube and shell inlet,

Design

Connections

Type stream name or select it from

outlet streams

the drop down box

Set pressure drop

Design

Parameters

View the UA for the heat

Design

Parameters

Type in pressure drop

exchanger

4. Pumps / Compressors / Expander Task

Tab

Section

Action

Enter inlet, outlet and

Design

Connections

Type stream name or select it from

energy streams View or enter the duty

the drop down box Design

Parameters

EITHER a. Set duty and exit press is calc; or b. Set exit press and duty is calc.

5. Separations Flash separator Task

Tab

Section

Action

Enter inlet, v-out, l-out

Design

Connections

Type stream name or select it from

and energy streams

the drop down box

Set pressure drop

Design

Parameters

Type in pressure drop

View or enter the duty

Design

Parameters

EITHER a. Set duty and exit temp

(non adiabatic flash)

is calc; or b. Set exit temp and duty is calc.