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Ammonia Synthesis with Aspen HYSYS® V8.0 Part 3 Process Economic Analysis 1. Lesson Objectives
Acquire basic knowle dge dge on the evaluation of the economics of a chemical process
Build upon the closed loop l oop Ammonia Synthesis process process simulation
Add process stream prices in feed fe ed and products
Add utility costs in the equipment
Learn how to perform economic evaluation eval uation within Aspen HYSYS. HYSYS.
Transform simplified simpl ified process into a more more realistic reali stic design desi gn
Economic Analysi s of followin foll owings: gs:
Capital Cost
Operating Cost
Raw Materials Cost
Product Sales and Utili ties Cost
Estimation Estimation of ‘Pay Off’ period
2. Prerequisites
Aspen HYSYS V8.0 V 8.0
Microsoft Excel
Completed Complete d design modules Design-001H Design-001H and Desi gn-002H gn-002H
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3. Background, Recap Recap of Ammonia Process
The examples presented are solely intended to illustrate specific concepts concepts and principle principles. s. They may may not reflect an industrial application application or real situat si tuation. ion.
4. Brief Introduction I ntroduction to Process Economic Analysis 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 – so it is important to make the right decision decisionss based based on rigorous cost estimates estimates instead of of guesswork.
The typical typical workflow of the the cost
estimation estimati on process is shown below.
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Typical Workflow of Cost Estimation
5. Aspen HYSYS Solution The following fl owsheet was developed for a closed l oop Ammonia Synthesis process.
5.01.
Open the soluti on .hsc file for the closed loop A mmonia Synthesis. ( Design_002_AmmoniaSynthesis_ClosedLoop.hsc )
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5.02.
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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. Sele ct Mass Flow for Flow Basis and enter 0.26 Cost/kg for Cost Factor.
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5.05.
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Next, double cli ck 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 vi ew 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 twi ce 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.
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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 stream Q-Comp2 and select Power for Utility Type.
5.10.
Double click on energy stream Q-Heater and select Fired Heat (1000) for Utility Type.
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5.11.
Double click energy stream Q-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 consi der realistic equipment design constraints. This simulation is highly simplified and has served to prove thi s process has potential to be profitable. The next step is to transform this highly simplified design into a ‘real-life’ desi gn which wi ll provide more accurate estimations for capi tal and operating costs. This is done using the built i n 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 functionali ty 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 ke y step in determini ng project scope and cost. This function enables unit operations from the simulation model to be mapped to “real-world” equipment so that preli minary 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 clicked, the foll owing window will appear. Press OK to continue.
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5.20.
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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 reali stic 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 cli ck 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.
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Lastly, select Vertical cylindrical process furnace and click OK.
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5.24.
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You have now successful ly 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 suf ficient to model the reactor as a shel l and tube heat exchanger, because the reactor will be a vessel containing tubes. Select the C RV-100 and click the drop down menu to change equipment type. 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.
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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 outl et temperature (stream S5V) from CRV-10 to 481.8 °C, which assures that the shel l 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.
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Click View Equipment, and go to the Equipment tab to vi ew any errors that occurred during evaluation. These errors will tell you what inputs or changes are required in order to cost the si mulation 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.
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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 inl et 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 i t 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 will 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 e stimate.
5.35.
Repeat the mapping and sizi ng 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 vi ew 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 potenti al 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.
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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 she et 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 as Aspen 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.
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7. Copyright Copyright © 2012 by Aspen Technology, Inc. (“AspenTech”). All rights reserved. This work may not be reproduced or distributed in any form or by any means without the prior written consent of AspenTech. ASPENTECH MAKES NO WARRANTY OR REPRESENTATION, EITHER EXPRESSED OR IMPLIED, WITH RESPECT TO THIS WORK and assumes no liability for any errors or omissions. In no event will AspenTech be liable to you for damages, including any loss of profits, lost savings, or other incidental or consequential damages arising out of the use of the information contained in, or the digital files supplied with or for use with, this work. This work and its contents are provided for educational purposes only. AspenTech®, aspenONE®, and the Aspen leaf logo, are trademarks of Aspen Technology, Inc.. Brands and product names mentioned in thi s documentation are trademarks or service marks of thei r respective companies.
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