[hahahanna]

Hi!!

See my picture. (notice: my calculatebase is 100 kmol)
i have calculate all my unknown variables:
x =23,07 kmol
y=45,93 -"-
z=7,40 "
w=0,6"
p=27,73"
r=2,39 "

now Im going to calculate how much natural gas (C_1,17H_4,3) i must have, if i want to make 1000kmol synthesis gas (the things i get out from the system). ( notice: C_1,17H_4,3) will contain N₂)

I have try to do like this:

100*(x/x+w)=1000kmol
(100 is my calculatebase, x is the naturalgas, and x+ w is natural gas with N₂)
and then i get my answer: 236,73 kmol

Have i done it right or should i think in another direction?
Please i really appreciate for help with this question!

[eugenedakin]

Hello hahahanna,

A very interesting question.

There are a few assumptions that I am making in order to help you out with your question:
1) CO₂ is neither being created nor reacted (the mole percent remains the same for CO₂ (r*z)
2) I am assuming that C_1.17H_4.3 is the averaged molecular composition of your feedstock.

As a suggestion, I would assume that you solve the problem 'backwards' - that meaning assume that you have made 1000kmol synthesis gas (CH₄) and then calculate the optimum C_1.17H_4.3 required.

Could you show me your calculations?

Thanks for your help.

Sincerely,

Eugene

[hahahanna]

hi!!
 i attach my calculation, i have taking a photo of my equationsystem, i think you can see what i have write.. My scanner is broken. The calculation start with the .doc file i attached.

[eugenedakin]

Hello hahahanna,

Here are some thoughts that I would use to determine the answer:

1) You want 1000 kmol of synthesis gas (or 714.29 kmol of 1.4 CH₄)
2) This means you need 1000 kmol of Carbon and 4000 kmol of Hydrogen
3) You will need 1000 kmol of Carbon (or 854.70 kmol of Carbon from C_1.17H_4.3)
4) You will need 4000 kmol of Hydrogen (or 930.23 kmol of Hydrogen from C_1.17H_4.3)
5) The limiting factor is 930.23 kmol. You will need 930.23 kmol of C_1.17H_4.3 to make 714.29 kmol of 1.4 CH₄.

Is this the way that you interpret the question?

Best wishes,

Eugene

[hahahanna]

I dont understand what you are saying exactly. Im thinking in this way:

I know that i have 100 vol % of my synthesis gas, and i have chosen it to be my calculate base, = 100 kmol.
Then i know that i have 100 kmol syntesis gas.

In this case, i know that my synthesis gas (H2,CO,CO2,CH4,N2) should be 1000 kmol, and i know that the contribute of natural gas is x kmol C^1,17H_4,3 to produce my synthesis gas.

So isn't im thinking right??

100 kmol synthesis gas * (? kmol of the contribute natural gas/(naturtal gas(x) + N2(w))=1000 kmol synthesis gas

and this will give me 236,73 kmol natural gas.

[eugenedakin]

Hello hahahanna,

Ah yes, you are right. I mistook the question to read that you wanted 1000 kmol of methane... my apologies.

Could you reprint what the question was with the beginning values?

Thanks for your help.

Sincerely,

Eugene

[hahahanna]

Hi!

My natural gas have this formula: C_1,17H_4,3 but it will also contain N₂
The synthesis gas contain the this i will get out of the wash, so:
H2 65 vol %
CO 33
CO2 0
CH4 1,4
N2 0,6
The sum of this synthesis gas, is my calculebase: 100 kmol
I know this also:
CO2/natural gas = 1,06
H2O/ natural gas= 1,94
After this i can calculate all my unknown variables in the reactor (see the picture I attach with this post. It it’s a .doc file I will attach.)
Now I know that CO2 is z, and the recirculation of CO2 is r*z, I also know that water is y. And the natural gas containing N2 is: x+w
So it must be know:
Z+(r*z)/ x+w = 1,06
y/x+w) 1,94

After that I do my equations system. And I will find all my unknow variables:
Now im going to calculated:
How much natural gas (C1,17H4,3) does it take to produce 1000 kmol synthesis gas (H2,CO,CO2, CH4,N2)??
So Im thinking in this way:
100 kmol synthesis gas * (? kmol of the contribute natural gas/(naturtal gas(x) + N2(w))=1000 kmol synthesis gas

and this will give me 236,73 kmol natural gas.

[eugenedakin]

Hello hahahanna,

Thanks for you patience. You are very close. The final equation provides you with volume percent, but you need mass to determine the number of moles present.

Let me describe this, and you let me know if it makes sense.

Convert the final concentration of synthesis gas from volume percent to mass percent (use the density of each chemical for this conversion). From here you can determine the number of moles of each chemical (periodic table of elements  This will provide you with the mass percent. With a total amount of synthesis gas of 1000 kmol, then determine the number of moles of each chemical by using the atomic weight from the periodic table (this is in units of grams per mole).

Once you know the number of moles of methane ( as CH₄ 1.4, then determine the number of hydrocarbon moles (C_1.17H_4.3).

You could follow the same steps to determine the number of moles of N₂.

I hope this helps, and thanks for your patience.

Best wishes,

Eugene

[bodhi]

sorry for my poor english .

[hahahanna]

Hi eugenedakin and bodhi for you answers!

But i think i solved it, i have done right calculations, but i could have gone a more simple way to do it.
Insted to have 5 or 6 unknown variabels i could have only 3.

I saw that later, and when recalculated in that way i did get the same answer as in this way i have shown.
Soo, yeah. i think its right. :-)

Thanks you again!!