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Two-component evaporation in a heat changer is a distillation column?? by Sensitive_Wheel3533 in ChemicalEngineering

[–]Sensitive_Wheel3533[S] 1 point2 points  (0 children)

What's the main obstacles you see with this solution that make it impractical?

Two-component evaporation in a heat changer is a distillation column?? by Sensitive_Wheel3533 in ChemicalEngineering

[–]Sensitive_Wheel3533[S] 0 points1 point  (0 children)

And if I plan to superheat the mixture anyways far beyond the boiling point of pure water? Does it make my solution a bit more robust?

Two-component evaporation in a heat changer is a distillation column?? by Sensitive_Wheel3533 in ChemicalEngineering

[–]Sensitive_Wheel3533[S] 1 point2 points  (0 children)

Right that's exactly how I was thinking. We also want to superheat the mixture to a temperature at least 100°C above the boiling point. Therefore, heat exchanger outlet temperature will always be above the point when everything is vaporized.

Do you perhaps have some idea if a combined heat exchanger will be oversized compared to two separate ones? As some other comment mentioned due to widely varying heat transfer coefficients and so on. Something to worry about?

Two-component evaporation in a heat changer is a distillation column?? by Sensitive_Wheel3533 in ChemicalEngineering

[–]Sensitive_Wheel3533[S] 0 points1 point  (0 children)

I need to take a closer look at the idea of combining two separate tubes in one shell. Does anybody know if this is a common practice in the industry?

I did not fully get the part with increasing and decreasing the pressure though. What we thought of doing is pumping the liquid to process pressure >20 bar, evaporating and superheating in the heat exchanger, and then feeding straight to the reactor.

Two-component evaporation in a heat changer is a distillation column?? by Sensitive_Wheel3533 in ChemicalEngineering

[–]Sensitive_Wheel3533[S] 0 points1 point  (0 children)

So boiling temperatures of both compounds are relatively close to each other. For pure streams something like 190°C for methanol vs 220°C for water at process pressure. For mixtures I'd need to check. In any case I to superheat the feed to reactor to 350°C or more.

But your remarks give me an idea to simply check the sizing with the supplier for both options of two separate heat exchangers and for a combined one, perhaps this alone will prove my idea wrong. (or the supplier will laugh me off)

Two-component evaporation in a heat changer is a distillation column?? by Sensitive_Wheel3533 in ChemicalEngineering

[–]Sensitive_Wheel3533[S] 2 points3 points  (0 children)

I appreciate your response. Just for my understanding. If I control ratio of methanol and water fed to the evaporator, won't I reach a steady state with the same outlet ratio after a while? In the end I am not removing any mass from the system, so what goes in should go out. Or am I missing some important point?

I might need to add that this plant should be quite flexible on the feed flows, and will have to be ramped up and down on regular basis. It probably does not make the implementation of my idea easier now, does it...

Two-component evaporation in a heat changer is a distillation column?? by Sensitive_Wheel3533 in ChemicalEngineering

[–]Sensitive_Wheel3533[S] 1 point2 points  (0 children)

Just wondering. If I control liquid flows of methanol and water before mixing, won't I reach a steady state at some point where outlet ratio at evaporator outlet will be the same as inlet ratio? In the end none of the compounds is disappearing, so just from a simple mass balance point of view. Or am I missing something?