7 replies to this topic

[JArchy123]

Basically I have to design a reactor for the conversion of CH4 to CO and H2. I have included below an excel file with  some of the paper I am getting formulae from. I have so far assumed a 95% conversion of CH4 and H2O in the first reaction step. But I have been told to use Euler's approach to compute for each XCH4 step (and associated XCO2 step) the value of the molar fractions of your reactants and products which in my case will be a function of XCH4 and, for some, XCO2. I was wondering how to start this as I know how Euler's approach works but I don't have a clue on how to start this for three reaction steps. 

Attached Files

•  Paper Formulae.xlsx   597.78KB   13 downloads

Edited by JArchy123, 22 December 2021 - 09:18 PM.

[Pilesar]

A literature search should give clues for starting. Here is one paper that may be useful:  https://macsphere.mc...2016Aug_PhD.pdf

[breizh]

Hi,

reference document attached for those interested .

Breizh 

[JArchy123]

I've been working on this all week and asked around some other forums but I keep getting different answers and mixed results. I have three reactions occurring simultaneously.

CH4 + H2O --> CO + 3H2
CO + H20 <--> CO2 + H2
CH4 + 2H2O <--> CO2 + 4H2

 

My lecturer and I have assumed the first reaction has a CH4 conversion of 95% with the flow rate of both the CH4 and H2O being 134.4753 mol/s. If I have the 95% conversion, I am wondering how much H2O would be provided to each of the other two steps; that is assuming the other 5% of the CH4 is going to the other steps.
 

I basically have conducted calculations to find the reaction rate of each step for varying CH4 conversions from 0.99 to 1*10^-10 (assumed to be 0). I have then fixed the conversion of the third step to a set value and then used the left over H2O from the third in the second assuming it is fully used up. I then used Euler's approach to find the Weight Catalyst according to the equations in the literature. This allowed me to find the weight of catalyst for the CH4 conversion and then the CO2 conversion. I then had to make the weight of catalyst equal for the XCH4 at 0.95 conversion and then for XCO2 conversion at 0.05 assuming that the rest of the CH4 is converted to CO2 in the 2nd and 3rd steps. Are my assumptions correct and is the correct methodology as I have been working on this for at least three weeks now and have felt that I have regressed? I have attached my excel spreadsheet below (labelled under Calculation of Catalyst Weight)

 

 

Also how would I calculate the reactor diameter as for the mean voidage calculations I need to determine the tube diameter.

Edited by JArchy123, 26 December 2021 - 06:17 PM.

[breizh]

Hi,

https://groups.googl...-2.pdf?part=0.1

 

Consider the link above to support your work.

Good luck

Breizh

[Pilesar]

The syngas reactions you reference are typical of a steam-methane reformer where steam is supplied at about a nominal three to one ratio with the gas. You might research 'steam methane reforming' to get more details.

[SilverShaded]

I'm not really sure what you've done and can't see your spreadhseet but all reactions are occuring simultaneoulsy.  Your spreadsheet should be calculating composition at each euler step and recalculating the rate of reaction based on composition at that step.  This should continue until you reach the CH4 conversion level your require.  The number of euler steps * dW(catalyst) gives you the quanitity of catalyst required.

I think i have a spreadhseet somewhere showing the procedure for a tatoray process using RK4 and 80 components, if i can find it i might include it here.
 

[JArchy123]

I'm not really sure what you've done and can't see your spreadhseet but all reactions are occuring simultaneoulsy.  Your spreadsheet should be calculating composition at each euler step and recalculating the rate of reaction based on composition at that step.  This should continue until you reach the CH4 conversion level your require.  The number of euler steps * dW(catalyst) gives you the quanitity of catalyst required.

I think i have a spreadhseet somewhere showing the procedure for a tatoray process using RK4 and 80 components, if i can find it i might include it here.
 

Thanks that would be quite helpful as I'm still a bit clueless