Design 003H AmmoniaSynthesis EconomicAnalysis

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Design-003H Revised: Nov 7, 2012

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Ammonia Synthesis with Aspen HYSYS® V8.0

Part 3 Process Economic Analysis

1.

Lesson Objectives

Acquire basic knowledge on the evaluation of the economics of a chemical process

Build upon the closed loop Ammonia Synthesis process simulation

Add process stream prices in feed and products

Add utility costs in the equipment

Learn how to perform economic evaluation within Aspen HYSYS.

Transform simplified process into a more realistic design

Economic Analysis of followings:

Capital Cost

Operating Cost

Raw Materials Cost

Product Sales and Utilities Cost

Estimation of ‘Pay Off’ period

2.

Prerequisites

Aspen HYSYS V8.0

Microsoft Excel

Completed design modules Design-001H and Design-002H




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3. Background, Recap of Ammonia Process

The examples presented are solely intended to illustrate specific concepts and principles. They may not

reflect an industrial application or real situation.

4. Brief Introduction to Process Economic Analysis

During the conceptual design phase 80% of capital costs are determined and 95% of your operating costs are

determined at this phase. Operating costs are typically 2-3 times the amount of capital costs. Decisions made

during the conceptual design process have a major impact on the final project – so it is important to make the

right decisions based on rigorous cost estimates instead of guesswork. The typical workflow of the cost

estimation process is shown below.




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Typical Workflow of Cost Estimation

5.

Aspen HYSYS Solution

The following flowsheet was developed for a closed loop Ammonia Synthesis process.

5.01. Open the solution .hsc file for the closed loop Ammonia Synthesis.

(Design_002_AmmoniaSynthesis_ClosedLoop.hsc )




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5.02. The final step of Design_002 was to run a Case Study. This altered the Temperature of stream S6, and

thus changed the purity of stream NH3. Double click on stream S6. In the Worksheet | Conditions page,

change the Temperature back to 26.85°C.

5.03. Next, double click on TEE-100 and set the Flow Ratio of Purge to .019. We are now ready to evaluate

cost.

5.04. First we wil l enter the buying and sell ing prices of our feed and product streams in order to determine if

our process is capable of making money. Double click the SynGas feed stream and go to the Cost

Parameters form under the Worksheet tab. SelectMass Flow for Flow Basis and enter 0.26 Cost/kg for

Cost Factor.




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5.05. Next, double click the product stream NH3. In the Cost Parameters form, select Mass Flow for Flow

Basis and enter 500 Cost/ton for Cost Factor.




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5.06. To view the total stream costs, go to the Economics tab in the ribbon and select Stream Price.

5.07. This will open up the Model Summary Grid. Here you can view the total cost for each material stream.

SynGas has a total cost of $15,941/hr, while the product stream NH3 has a value of $28,794.7/hr. In

this case the product stream is roughly twice as valuable as the feed stream. This is a good sign and

indicates that this process may be profitable.




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5.08. Next we will estimate costs for utilities. Double click on energy stream Q-Comp1. Select Power for

Utility Type.




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5.09. Double click on energy streamQ-Comp2 and select Power for Utility Type.

5.10. Double click on energy streamQ-Heater and select Fired Heat (1000) for Utility Type.




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5.11. Double click energy streamQ-Cooler and select Cooling Water for Utility Type.

5.12. Double click Q-Reac and select Cooling Water for Utility Type.




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5.13. To view the utility summary, click Flowsheet Summary in the Home tab of the ribbon.

5.14. The Flowsheet Summary window wil l appear. Go to the Utility Summary tab. Here you can view the

cost of each utili ty and the total costs of utilities. The Total Costs of Hot Utilities are $2792/hr, and the

Total Costs of Cold Utilities are $25.47/hr.

5.15. The operating profit of this process is equal to:




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The operating profit of this process is $10,036.23 per hour. The next step is to evaluate the capital costs

of the process.

5.16. This simulation has so far taken into account the mass and energy balances but it has yet to consider

realistic equipment design constraints. This simulation is highly simplified and has served to prove this

process has potential to be profitable. The next step is to transform this highly simplified design into a‘real-life’ design which wi ll provide more accurate estimations for capital and operating costs. This is

done using the built in economics in Aspen HYSYS.

Transform simplified design using built in Economic Analyzer

5.17. Go to the Economics tab, and select Activate Economics. This will enable the Economic Analysis

functionality in Aspen HYSYS.

5.18. When the economic analysis is Activated, the Integrated Economics buttons are enabled and ready to

apply economic calculations. Next, click the Map button.

5.19. The map function is a key step in determining project scope and cost. This function enables unit

operations from the simulation model to be mapped to “real-world” equipment so that preliminary

equipment sizing can be performed. This mapping process is analogous to equipment selection and

sizing and will serve as the basis in determining costs. When the Map button is cl icked, the following

window will appear. Press OK to continue.




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5.20. The following window titled Map Preview will allow you to change the mapping for certain unit

operations. The Economic Analysis has pre-defined default mappings for unit operations. However,

these may be changed to create a more realistic cost evaluation. For example, the default mapping for

heaters are floating head shel l and tube exchangers, but heater block E-100 is a furnace which burns

natural gas.

Select E-100 and click the drop down menu under Equipment Type.




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5.21. A new window will appear, select Heat exchangers, heaters and press OK.

5.22. Next, choose Furnace and click OK.




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5.23. Lastly, select Vertical cylindrical process furnace and click OK.




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5.24. You have now successfully changed the mapping of E-100 and its cost wil l be evaluated accordingly. We

must also change the mapping of the reactor from an agitated tank to a plug flow reactor. For this

process it is sufficient to model the reactor as a shell and tube heat exchanger, because the reactor wil l

be a vessel containing tubes. Select the CRV-100

and click the drop down menu to change equipmenttype. Select Heat exchangers, heaters | Heat Exchanger | Fixed tube sheet shell and tube exchanger.

Click OK in the mapping window to complete the mapping process.

5.25. Next, click on Size. The sizing process will complete.

5.26. Select View Equipment to view the results of the sizing.




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5.27. The Economic Evaluation Equipment Summary Grid will open. Go to the Equipment tab. You may

encounter an error for CRV-10 involving both the shell and tube streams being heated. This can be

addressed by changing the outlet temperature (stream S5V) from CRV-10 to 481.8 °C, which assures

that the shell stream will decrease in temperature.

5.28. We are ready to evaluate. Click the Evaluate button in the ribbon. The economic engine will perform

the analysis, it may take a few moments.




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5.29. Click View Equipment, and go to the Equipment tab to view any errors that occurred during evaluation.

These errors will tell you what inputs or changes are required in order to cost the simulation more

realistically.

5.30. The evaluation error for compressor E-100 states that the material specified is inadequate for design

conditions. To fix this, go to the EFU VERTICAL tab and select a suitable material for construction.

Select 304S (stainless steel) for Material.




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5.31. The error for K-100 is that the inlet temperature is too high. To fix this we will had a cooler before the

compressor to cool down the inlet stream.

5.32. Double click K-100 and remove stream SynGas as an Inlet stream. Create an Inlet stream called

SynGas2. Add a Cooler block to the flowsheet and select SynGas as the Inlet stream, SynGas2 as the

Outlet stream, and create an Energy stream called Q-Cooler2. Specify a Delta P of 0 and an outlet

Temperature of 300 K. Double click stream Q-Cooler2 and specify Cooling Water as the Utility Type.

The flowsheet should now look like the following.

5.33. The errors for both E-101 and CRV-100 are that there are no materials in the database that are suited

for such a high temperature and pressure combination. These materials will likely have to be custom

made for this specific process and priced accordingly. However for this simplified simulation, we can try

lowering the operating pressure in order to get a cost estimate. In real life it may not be plausable to




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change the operating conditions, as the reaction kinetics may be very dependent on temperature and

pressure. However, for this simulation we are not using kinetics. Therefore the reaction wil l not be

affected.

5.34. Double click each compressor and change the outlet pressure to 190 bar_g. The process will now

operate at lower pressures, allowing economic evaluation to produce a cost estimate.

5.35. Repeat the mapping and sizing process since a new piece of equipment now exists on the flowsheet.

When ready, click Evaluate. The equipment results will now look like the following in the Economic

Evaluation Equipment Equipment Grid. There should not be any errors.

5.36. Go the Summary tab to view results.

5.37.

This table displays the different costs associated with constructing and operating this process as well as

the total product sales per year. This process appears to have the potential of being a highly profitable

investment, with a payoff period of only 3.64 years.

5.38. Click on the Investment Analysis button.




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5.39. This will open up a Microsoft Excel spreadsheet that summarizes the results. In the Excel spreadsheet

there will be the following sheets: Run Summary, Executive Summary, Cash Flow, Project Summary,

Equipment, Utility Summary, Utility Resource Summary, Raw Material Summary, and Product

Summary.

5.40. The Executive Summary sheet is a very useful sheet which displays the project name, capacity, plant

location, description, scheduling, and investment information. This is shown below.

5.41. The Cash Flow sheet is also useful and displays various costs and assumptions that went into making the

economic estimations.




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6.

Conclusion

Aspen HYSYS along with the economic analyzer tool can quickly create first approximations of process sizing and

costs. This is very useful when attempting to compare several process designs to decide which design will have

the best potential to be profitable. If a process has proven to be profitable at this level of analysis, costing

engineers will then take this preliminary design and fine tune it in a more detailed costing application such asAspen Capital Cost Estimator. Taking a conceptual design from a process simulator and being able to accurately

estimate the associated costs is extremely valuable and can be the difference between a successful investment

and a company going out of business.




7. Copyright

Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be

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liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential

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Design 003H AmmoniaSynthesis EconomicAnalysis

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