When optimizing my plant in which water-ammonia is the working fluid, every pressure or temperature can be selected as variable but mass or mole fraction isn't available. How can one select this parameter as a design variable in optimization process?
In general, there are two types of variables in Hysys. Independent and dependent variables. Those which are in blue (inserted by you) and red (inserted by Hysys) are independent and the rest which are in black are dependent. You can only manipulate dependent variables. In your case, you are gonna manipulate the mole fraction. In this case follow these steps,
1) erase the total mole/mass flow of the stream.
2) calculate the mole/mass flow rate of each component based on the total flow and component fractions.
3) insert the component mole/mass flows in the composition tab.
in this case the total flow is calculated based on the flow rates you inserted, and you can also select them as manipulating variables in your optimization case.
If you need more info, do not hesitate and let me know.
@Farooq
Thanks
You are talking about data input for simulation, I have problem in optimization friend.
@ Amir
Thanks for your answer
Please tell me details of your answer.
You can change mole flow. Split your stream into pure components and then reconnect them. Change the mole flow of one of the split streams instead of the mole fraction.
In general, there are two types of variables in Hysys. Independent and dependent variables. Those which are in blue (inserted by you) and red (inserted by Hysys) are independent and the rest which are in black are dependent. You can only manipulate dependent variables. In your case, you are gonna manipulate the mole fraction. In this case follow these steps,
1) erase the total mole/mass flow of the stream.
2) calculate the mole/mass flow rate of each component based on the total flow and component fractions.
3) insert the component mole/mass flows in the composition tab.
in this case the total flow is calculated based on the flow rates you inserted, and you can also select them as manipulating variables in your optimization case.
If you need more info, do not hesitate and let me know.
Hamid reza thanks, I did so, please find the attached document to see my problem
What I would have thought that composition change of a stream can not take place without a chemical reaction or physical separation such as distillation/adsorption/absoprtion etc.
In a reaction, we either calculate the composition by stoichiometry or by kinetics which is usually dependent on the system temperature and pressure. So, compositions of the outlet stream from a reactor would depend on these conditions.
In separation process like a distillation column, we need to specify the target mole fractions of the desired component in all outflow streams for expected recovery.
So, if the mole fractions are variable in a stream, they should in principle be available for optimization for example to obtain a best combination of mole fractions in top and bottom stream of a distillation within the specified limits to optimize the reboiler duty.
But if a stream is not associated with such requirement for example two streams are joining a mixer/tee junction, there may not be a dependency on mole fractions for optimization purpose.
Ok. erase mass flow of 3600 kg/hr in condition tab. then go to the composition tab, click edit, and then select mass flow rate (basis part) there and then enter 3345 kg/hr for water and 225 kg/hr for ammonia. This can help you.
In the file you sent me,
The composition is in blue (you entered them). however, there is a relation between these mass fractions. their sum should be one. this requirement makes them dependent and you can not manipulate them individually.
Thanks Hamidreza,
I understood your suggestion and I think it may be helpful, I work on it, and will inform you whether I could reach what I have in my mind or not.
Hi Rasool,
You also have one more option. Since you are optimizing a couple of different parameters and classic optimization methods are not very good at this, you may choose to handle the optimization problems somewhere else and return the optimized data to Hysys or alternatively make a permanent link between Hysys and optimization software (e.g. Matlab) to handle the optimization problem. The later can be done through COM technology available in windows by defining the Hysys session as a server in a Matlab code to transfer relevant parameters from Hysys to Matlab and vice versa. When you do this you can overwrite all availbale variables in Hysys but you still need to be carful not to confused Hysys in terms of assigning values to dependent/independent variables.
Hi Rasool,
I am having the same problem as yours. I have not yet solve my problem, but i see some people can solve it.
You can read this science article riviste.edizioniets.com/heatandtech/articles/download/id/118
The author is from Iran.
I send an email and wait for the answer.
Dear Khoa Nguyen Ngoc
In this study although mass fractions of components are considered but they have not been varied.
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