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Multiple Reactions Cstr In Hysys

cstr multiple reactions hysys

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#1 ChE student17

ChE student17

    Junior Member

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Posted 21 November 2018 - 10:15 AM

Good day,

I am a new member of the community. I would like to ask for help in dealing with errors upon the use of Aspen HYSYS.

For our plant design, we need to simulate a CSTR reaction with multiple reactions in it. So, we added a reaction set comprising of 6 reactions. All reactions are of the type: Heterogeneous Catalytic.

The reactions in the set comprises of 1 main reaction (for the desired product), and 5 side undesired reactions. For context, the following are the reactions:
Main reaction:   Glycerol + NaOH ---> Sodium lactate + H2 + H2O

Side reactions:  Glycerol + H2 ---> 1,2-propanediol + H2O

                          1,2-propanediol + H2 ---> 2-propanol + H2O

                          Glycerol + H2 --->  Ethylene glycol + Methanol

                          Glycerol + 2 H2 ---> Methanol + Ethanol + H2O

                          Ethylene glycol + H2 ---> 2 Methanol

The feed for the reactor is only composed of glycerol, NaOH, and water. The H2 needed for the side reactions would be produced in situ when the main reaction proceeds.

Now, here lies our problem. When we simulate the reactor using all reactions in one reaction set, the reaction would not show overall conversion, and thus means the reaction would not proceed and produce the product. However, when we separate each reactions and do 1 reaction per reactor (e.g. a reaction set would only have 1 reaction to be used for each reactor) and connect them in series, there will be a displayed conversion and the reactions would proceed (with the products on the output).

But, in reality, the reaction should be simultaneous in one reactor, and thus (as advised to us), the simulation should be one reactor only. Since by doing a series of reactors, it would mean that the reaction would proceed consecutively, which isn't true in our case.

So, in your opinion, what could go wrong in our simulation that it would produce error when the reactions are placed all together? Any tip to properly model it in HYSYS?

Thanks in advance for your help. And, please notify me on some missing info to help our case.

P.S. We used the same values for pressure, temperature, and reactor volume for both simulation.

Edited by Lactic Guest, 21 November 2018 - 10:39 AM.

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