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

[Daniel W. <dan...@gm...>]

Hector, the actual criteria for throwing the pressure drop error in the PFR
model is a negative pressure value after the pressure drop calculation
step:
https://github.com/DanWBR/dwsim3/blob/master/DWSIM/Objects/Reactors/PFR.vb#L828

Hey, we live relatively close to each other. I'm in Manaus, Amazonas. Could
we say that both of us live in the Amazon? :-)

Regards,
Daniel

2016-04-27 9:30 GMT-04:00 Hector Perez <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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>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>