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Approach To Equilibrium For Primary Reformer Catalyst

Posted: Tue Dec 10, 2019 8:07 am
by ahmadkakhki
Hi
approch to equilibrium (ATE) is a way to analyze the performance of primary reformer catalyst. how we can determin this ATE and is it good way for analyzing the perforance of catalyst?
thanks

Re: Approach To Equilibrium For Primary Reformer Catalyst

Posted: Wed Dec 11, 2019 2:02 pm
by bedmonds
Hi Ahmad, I've always used the assumption that the water gas shift reaction is at equilibrium while the steam methane reforming reaction has an approach to equilibrium that is a good indicator of catalyst performance. Then an iterative approach can be used to converge to an actual approach to equilibrium using the Keq values for the two reactions. Pressure squared is used in the SMR reaction calculation since 2 moles of reactants go to 4 moles of product. The calculated value is very sensitive to knowing the correct S/C ratio and the measured reformer outlet temperature so I think best to work out S/C using HTS and LTS analyses to make sure there is a good fit-then you can determine if the temperature is correct since, if it is not, the WGS equilibrium will be wrong at the primary reformer. To have a good result lots of cross checking is required since early in the catalyst life, ATE will be very low-in the 2 deg C range. The ATE for the secondary reformer is a bit more difficulties since outlet temperature must be calculated from heats of reaction but once set up the model is easily run on a computer. I could send you the program I built but it's in a obsolete BASIC language so not easy to use since it is DOS based. Spme catalyst vendors offer software to do these calculations.
Best Regards.

Re: Approach To Equilibrium For Primary Reformer Catalyst

Posted: Wed Dec 11, 2019 3:01 pm
by ahmadkakhki
Thank you.
It is So useful.
How much is the ultimate range for ATE that we sure the catalyst have a good performance?

Re: Approach To Equilibrium For Primary Reformer Catalyst

Posted: Thu Jan 02, 2020 3:42 am
by BhupenMehta
ATE for Steam-Methane (SM) Reforming catalyst may be calculated as under:n
Approach to equilibrium for Methane steam (MS) reforming reaction for Primary and Secondary reformer can be calculated as under:
Based on process gas composition at exit of primary reformer on wet basis., exit temperature Texit in degC and pressure Pexit in kg/cm2
Calculate the equilibrium constant KMS as under:
Kp= (%CH4. %H2O)/(%CO.%H2^3)*( Pexit /10^4)^2 .. (kg/cm2)^2
Estimate the equilibrium Temperature at reactor exit
Tequil = {26830/(30.18-LN(Kp ) ) - 273.15} degC
Calculate the approach to Methane steam as under:
ATE = Texit - Tequil , degC

Re: Approach To Equilibrium For Primary Reformer Catalyst

Posted: Thu Jan 02, 2020 4:03 am
by BhupenMehta
Approach To Equilibrium (ATE) for Primary Reformer Catalyst for Steam-Methane (SM) Reforming Reaction can be calculated as under:
Based on process gas composition on wet basis, exit temperature Texit in degC and pressure Pexit in kg/cm2 at exit of primary reformer
1.Estimate the equilibrium constant KMS as under:
Kp= (%CH4. %H2O)/(%CO.%H2^3)*( Pexit /10^4)^2 .. (kg/cm2)^2
2.Estimate the equilibrium Temperature at reactor exit
Tequil = {26830/(30.18-LN(Kp ) ) - 273.15} degC
3.Calculate the approach to Methane steam as under:
ATE = Texit - Tequil , degC

Re: Approach To Equilibrium For Primary Reformer Catalyst

Posted: Sat Jan 04, 2020 5:47 am
by pbaboo
The approach to equilibrium is defined by
Kp =P(CH4)P(H2O)/P(H2)3.P(C)
Kp is inversely proportional to temperature, Therefore achieve to good equilibrium position need to use a high temperature. Water gas is also equilibrium as same equations.CO is not depend upon pressure. Higher S/C ratio gives higher CO2 contents, Kp is related to temperature. High Exit temperature gives more CO and conversely less CO2.Water gas is at equilibrium at exit of the reformer, reaches equilibrium at very fast.
ATE=Actual temp-equilibrium temp.

Re: Approach To Equilibrium For Primary Reformer Catalyst

Posted: Sat Jan 04, 2020 5:55 am
by BhupenMehta
Above curves will just provide the idea on ATE, but Kp calculation is gas composition and exit pressure dependant as shown in equation.Hence, calculation are required for each specific case depending on gas composition, exit pressure and temperature.