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Propylene, MeOH, Water distillation

Propylene, MeOH, Water distillation

Propylene, MeOH, Water distillation

Dear experts.
I'm studying chemical process design from biomass as a student.
I'm planning to design a distillation column that recycles propylene with 99.9% purity at a flow rate of 54,256 kg-mol/hr at the rectification section, where propylene+MeOH+Water enters as a feed.
We have to get propylene as a top product, MeOH and Water as a bottom product.
The reaction in the propylene reactor part before the distillation consists of the following steps 1 and 2.

* Reactions in Propylene Reactor:
1. 2MeOH -> Ethylene +2H2O(Conversion ratio of MeOH is 60%)
2. MeOH + Ethylene -> Propylene +H2O (Conversion ratio of Ethylene is 100%)
- operating condition : 450 degC , 2kg/cm2g

But I don't know how can I access for this distillation
Does anyone advice me how to solve the problem.
Thanks in advanced.

RE: Propylene, MeOH, Water distillation

Quote (ENG-TIPS.com)


Student posting in Eng-Tips forums for help with theses or coursework is forbidden. This is considered cheating. Offending posts will be removed from the site and offending members will lose their membership privileges.

Good luck,

To a ChE, the glass is always full - 1/2 air and 1/2 water.

RE: Propylene, MeOH, Water distillation

Thanks , Latexman.
I'm sorry I didn't know that policy.
I'm not really a college student. I am a new employee who is studying in the same way such as a student.

And I don't get your sentence. "the glass is always full - 1/2 air and 1/2 water."

Could you give me more advice, please?

RE: Propylene, MeOH, Water distillation

The misunderstanding is that the phrase is a tag line that is part of Latexman's signature, and is not meant to be part of his reply.

RE: Propylene, MeOH, Water distillation

Are you asking us to help you design the entire distillation process from scratch or do you have a specific question?

RE: Propylene, MeOH, Water distillation

I'm just wondering how should I access from where at first.

Please I'm waiting for any advices

RE: Propylene, MeOH, Water distillation

From what understanding, knowledge, experience, and resources are you starting, w.r.t. distillation in general and this specific separation?

Good luck,

To a ChE, the glass is always full - 1/2 air and 1/2 water.

RE: Propylene, MeOH, Water distillation

I'd start by looking for any literature on this ternary system and see if there' is any non-ideal behaviour. If you have simulation software, you can use that for thermodynamic data, otherwise that's another literature search endeavor (NIST webbook is a good place to start). Start with what you did when learning about binary system distillation and you'll see what gaps you have to fill in because it's a ternary system.

RE: Propylene, MeOH, Water distillation

I'm practicing process simulation by using pro 2 simulation tool.

At first, I used a shortcut column for decision num tray of a distillation.

Component : propylene/ methanol/ water
Thermo : NRTL01

Feed : Total fluid flowrate : 220 kg-mol/hr
Composition Mole : propylene : 25 , methanol : 15, h2o : 60
Temperature : 311 K
Pressure : 1.5 kg/cm2

Shortcut: Condenser : subcooled, Fixed Temperature : 318 K
Spec : Propylene from top 99.9%
Water from bottom 99%

First, when I simulated this model , the result said " ** WARNING ** UNIT 1, 'SCD1' - MINIMUM REFLUX calculations FAILED to
converge. Incorrect specification of the KEY components MAY be
a possible cause."
Second, there are no values of 'total trays, feed tray, R/R-MIN' in the text result.

I can't solve this problems.

Thank you.

RE: Propylene, MeOH, Water distillation

for simulating separations I use a different solution (Excel / Matlab + Prode thermo library) and my knowledge of PROII is limited, anyway you may read the operating manual for the details,
as first step you should select the models, there are many sources of VLE data including propylene-methanol-water , you may also find many papers, see for example


for similar mixtures and conditions I have used Peng-Robinson-NRTL with Huron Vidal or LCVM mixing rules, also CPA (or other models with association contribute) could be an option but slow,

for simulating the column I would manually vary the number of trays to find an optimal solution, I can do that automatically in Excel with Prode (a simple heuristic optimization),
I do not know if you have a similar option is PROII (some expert can add comments)

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