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December 23, 2010, 05:12 
Xu & Froment methane steam reforming UDF

#1 
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Sungjong Jo
Join Date: Nov 2010
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Hi.
I'm trying to make a UDF about steam reforming using Xu & Froment equation ("Methane Steam Reforming, Methanation and WaterGas Shift:I.Intrinsic Kinetics") My problem is unit conversion. Xu & Froment's rate constant has a unit of (kmol/kg/h). and DEFINE_VR_RATE macro guide said that macro has return value of (kgmol/m^3/sec) what should i do to make it fit in Fluent format. i tried 1. cell density 2. cell density*(sum of each reaction's reactants mole fraction) it does not match up with reference value. anybody who has experience about steam reforming UDF give me some advice,plz. 

January 26, 2012, 08:49 

#2 
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Kerem Aksakal
Join Date: Apr 2011
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sorry for late reply, but is there any possibility that you miss the fact that, reaction rate in Xu and Froment is for per kg catalyst rather than per m^3. That means it should be taken as a surface reaction or should be taken into account as porous region. (very thin catalyst thickness which is defined as porous region will do the job.)


April 3, 2014, 22:46 

#3  
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Li Jiageng
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Quote:
Have you solved this problem? Recently, I have the same question as you. I want to use Xu & Froment equation to make a UDF in fluidized bed and face the unit convertion problem. 

June 6, 2014, 23:18 

#4 
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Sungjong Jo
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I couldn't solve the problem.
Instead I used other equation that converted from Xu&Froment rate equation into Arrhenius equation. It was research paper written in Korean. "A Comparative Study for SteamMethane Reforming Reaction Analysis Model" (You can find it from "www.dbpia.co.kr") This paper compared the original Xu&Froment equation written in UDF with three Arrhenius coefficient modified model. Arrhenius coefficient modified model approximately well followed conversion rate graph of original equation but this paper recommended UDF method. Because it was more accurate. Anyway I used model 3 coefficient model. I don't know it will help for your problem. But it could be alternative solution. <REFORMING EQUATION> Equation 1. CH4 + H2O ↔ CO + 3H2 Equation 2. CH4 + 2H2O ↔ CO2 + 4H2 Equation 3. CO + H2O ↔ CO2 + H2 <ARRHENIUS EQUATION> Ki = Ai * T^(Bi) * exp(Ei/RT) <Reaction coefficient for three Arrhenius type reaction models> model 1 Eq. (1) Ei : 2.40×108 // Ai : 9.490×1016 // Bi : 0 Eq. (2) 2.439×108 // 2.290×1016 // 0 Eq. (3) 6.413×107 // 4.390×104 // 0 model 2 Eq. (1) 2.40×108 // 4.745×1014 // 0 Eq. (2) 2.439×108 // 1.145×1014 // 0 Eq. (3) 6.413×107 // 2.195×102 // 0 model 3 Eq. (1) 2.40×108 // 6.811×1035 // 7 Eq. (2) 2.439×108 // 1.145×1014 // 4 Eq. (3) 6.413×107 // 2.195×102 // 0 

November 11, 2014, 19:37 

#5 
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Li Have you rectified how to sort the issues with XU and Froment rate equation in your fluidized bed as I have similar problem. I thought about multiplying the rate with the density of catalyst
kmol/Kgcat/s x Kg/m3. this will change the rate to kmol/m3/s. what do you or anyone think of this method for a fluidized bed system. Please really need your replies and support urgently. Thanks 

May 24, 2016, 04:18 

#6  
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Quote:
In my case I treat the fixed catalyst bed as homogenous. This enables me to convert the units by just multiplying with the total mass of catalyst in my reactor, divide it by the volume of the catalyst bed and by 3600. does this help? 

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froment, steam reforming, udf 
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