Re: [dwsim-users] reactor application - ethyl acetate

[Hector P. <hpe...@gm...>]

I see. Thank you Daniel for taking the time to answer my questions. I look
forward to continuing to use DWSIM and spread the word here in Colombia.
You've done an amazing job with this program.

Have a nice day,

Hector D. Perez
Chemical Engineering Consultant

On Wed, Apr 27, 2016 at 8:28 AM, Daniel Wagner <dan...@gm...> wrote:

> Hi Hector,
>
> For liquids, a high pressure drop would be one that vaporizes part of
> it... for gases, I guess that it would be worse because gas properties are
> heavily dependent on pressure, and that can cause changes in concentrations
> and/or fugacities, impacting the final conversion.
>
> Regards
> Daniel
>
>
> 2016-04-27 9:22 GMT-04:00 Hector Perez <hpe...@gm...>:
>
>> Hi Daniel,
>>
>> Thank you for the clarification. What is the criteria for "high pressure
>> drop" in a PFR? I'm seeing that in the acetate problem, DWSIM won't let me
>> go beyond a pressure drop of 0.23 atm.
>>
>> Thanks,
>>
>> Hector D. Perez
>>
>>
>> On Wed, Apr 27, 2016 at 8:09 AM, Daniel Wagner <dan...@gm...>
>> wrote:
>>
>>> Hi Hector,
>>>
>>> I don't know how the volume calculation works on Aspen but, in DWSIM, I
>>> do the following:
>>>
>>> PFR code (use this for line number references in the text below):
>>> https://github.com/DanWBR/dwsim3/blob/master/DWSIM/Objects/Reactors/PFR.vb
>>>
>>> - For the PFR, if you have a reactor of volume X, and the volume delta
>>> is 0.05, then the ODE (ordinal differential equation system) mass balance
>>> calculation will be done in 0.05*X volume steps until the entire volume is
>>> calculated (line 832). If you don't care about the actual pressure drop
>>> calculation, you can enter any value for the reactor length. Just be sure
>>> to input a length that doesn't result in a high pressure drop across the
>>> reactor. DWSIM calculates the pressure drop using the reactor volume and
>>> length to estimate the internal diameter, then uses the Darcy formula to
>>> calculate pressure drop. If the reactor has a catalyst bed, then the Ergun
>>> formula is used (line 797).
>>>
>>> CSTR code (use this for line number references in the text below):
>>> https://github.com/DanWBR/dwsim3/blob/master/DWSIM/Objects/Reactors/CSTR.vb
>>>
>>> - For the CSTR, the entire reactor volume is used at once and the ODE
>>> system is solved one time only (lines 559/111). There is no pressure drop
>>> calculation because this is supposed to be a batch (tank) reactor. :-)
>>>
>>> Regards
>>> Daniel
>>>
>>>
>>>
>>> 2016-04-27 0:06 GMT-04:00 Hector Perez <hpe...@gm...>:
>>>
>>>> Hi Daniel,
>>>>
>>>> Thanks for sending the file along with the updated build! I actually
>>>> went through the file and included the reverse reaction by adjusting the
>>>> Reverse Order exponents (the Aspen Plus video has both forward and reverse
>>>> reactions). I also dropped the conversion on the Conversion reactor
>>>> (to~70%) and set the equilibrium constant (for the Equilibrium Reactor) to
>>>> be k_forward/k_reverse (ratio of rate constants). My numbers are now very
>>>> close, if not the same as the ASPEN simulation video.
>>>>
>>>> One thing I did run into is that the reactor dimensions for the PFR and
>>>> CSTR in the aspen video create errors in DWSIM. I had to decrease the PFR
>>>> length because it gave me a warning about the pressure drop being too high.
>>>> The CSTR volume also had to be decreased because it gave me a mass balance
>>>> error. Do you know why the aspen dimensions don't work? This could perhaps
>>>> be a lack of feasibility check on the ASPEN side.
>>>>
>>>> Also, what is "Volume Delta (Relative)" on the PFR specs?
>>>>
>>>> One other thing I checked was the CSTR duty (compared to the ASPEN
>>>> video) and found the DWSIM value to be about 6 times lower than the ASPEN
>>>> value (perhaps something having to do with the smaller volume used in
>>>> DWSIM?).
>>>>
>>>> Thanks once again. I am really liking this simulator. It seems easier
>>>> to use than aspen.
>>>>
>>>> Hector D. Perez
>>>>
>>>>
>>>> On Tue, Apr 26, 2016 at 7:11 PM, Daniel Wagner <dan...@gm...>
>>>> wrote:
>>>>
>>>>> Hi Hector,
>>>>>
>>>>> By following the Aspen Plus video I was able to make it work, there is
>>>>> no reverse reaction. Also, there was a bug in the PFR pressure drop
>>>>> calculation, you'll have to use an updated build. Download it from this
>>>>> link and unpack the files in DWSIM's installation directory:
>>>>> https://sourceforge.net/projects/dwsim/files/DWSIM/DWSIM%203.7/Build5960.rar/download
>>>>>
>>>>> Also, I forgot to tell you that, for kinetic reactions, every compound
>>>>> in the reaction must be present even if in a small amount, i.e. 0.000001. 0
>>>>> will give you an error.
>>>>>
>>>>> You can also try the updated simulation file, I've added the
>>>>> equilibrium reactor as well.
>>>>>
>>>>> Regards
>>>>> Daniel
>>>>>
>>>>>
>>>>> 2016-04-26 18:17 GMT-04:00 Hector Perez <hpe...@gm...>:
>>>>>
>>>>>> Hi Daniel,
>>>>>>
>>>>>>
>>>>>>
>>>>>> For kinetic reactions, what are the units on the activation energy?
>>>>>> (same units as those specified for the molar entropy?). I included the DO
>>>>>> and RO exponents as well as the base compound and now get a new error on
>>>>>> the CSTR: “An error occurred during the mass balance calculation. Check
>>>>>> reaction kinetics data and reactor sizing information as well.”
>>>>>>
>>>>>>
>>>>>>
>>>>>> The PFR gives me the error: “One or more flash specification values
>>>>>> are invalid. Please check the associated UO or Material Stream for
>>>>>> incorrect specifications or miscalculated values.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Thank you, I really appreciate your assistance.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Hector D. Perez
>>>>>>
>>>>>>
>>>>>>
>>>>>> *From: *Daniel Wagner <dan...@gm...>
>>>>>> *Sent: *Tuesday, April 26, 2016 3:59 PM
>>>>>> *To: *Hector Perez <hpe...@gm...>
>>>>>> *Cc: *dws...@li...
>>>>>> *Subject: *Re: [dwsim-users] reactor application - ethyl acetate
>>>>>>
>>>>>>
>>>>>>
>>>>>> For the existing reactions, you've missed the compound
>>>>>> concentrations' direct and reverse order exponents. You also didn't define
>>>>>> the base compound, which should be the main reactant.
>>>>>>
>>>>>>
>>>>>>
>>>>>> For the conversion and equilibrium reactors, you must define the
>>>>>> corresponding reactions. Kinetic reactions only work with the PFR and the
>>>>>> CSTR.
>>>>>>
>>>>>>
>>>>>>
>>>>>> 2016-04-26 16:43 GMT-04:00 Hector Perez <hpe...@gm...>:
>>>>>>
>>>>>> Hi,
>>>>>>
>>>>>>
>>>>>>
>>>>>> I am trying to replicate the following ASPEN tutorial to set up the
>>>>>> liquid reaction for ethyl acetate formation from ethanol and acetic acid
>>>>>> using different types of reactors:
>>>>>>
>>>>>>
>>>>>>
>>>>>> https://www.youtube.com/watch?v=_DOdlUDI-kI
>>>>>>
>>>>>>
>>>>>>
>>>>>> Unfortunately, only the Gibbs reactor yielded any result with a ethyl
>>>>>> acetate flow that was 12 kmol/hr lower than the ASPEN simulation. The only
>>>>>> differences I can see is that the ASPEN simulation uses the NRTL-hoc,
>>>>>> whereas my simulation uses NRTL.
>>>>>>
>>>>>>
>>>>>>
>>>>>> The conversion reactor had zero conversion and both the PFR and CSTR
>>>>>> reactors gave the error: "The given key was not present in the dictionary."
>>>>>> I'm not sure what this means. I tried different thermodynamic models
>>>>>> besides NRTL with no avail.
>>>>>>
>>>>>>
>>>>>>
>>>>>> I will send my simulation file attached.
>>>>>>
>>>>>>
>>>>>>
>>>>>> I would really appreciate any light on the matter.
>>>>>>
>>>>>>
>>>>>>
>>>>>> Obrigado!
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> Hector D. Perez
>>>>>>
>>>>>> Chemical Engineering Consultant
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
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>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>