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Carbon Number Calculation For Ng


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#1 Ankit_Kumar

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Posted 08 January 2017 - 04:54 PM

Dear All,

 

At Ammonia/Methanol steam reformer, for steam to carbon ratio moles of steam & moles of carbon are calculated based on flow & composition of feed e.g. Natural Gas.

 

Appreciate if anyone can explain why CO2 present in NG is not considered in total carbon number calculation?

 

Also i have seen as most of recycle gas(supplied for hydrogenation) contains some amount of CO which is used for measuring total Carbon of Steam-NG mix feed to reformer? 

 

Regards



#2 Saml

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Posted 08 January 2017 - 06:41 PM

Not completely sure, so take it with a grain of skepticism. I think that it is because S/C ratio is intended to prevent carbon formation.

 

CO2 is on the products side of the Bouduard reaction, so it tends to remove carbon from the catalyst's surface

 

2CO <-> CO2 + C

 

Other solid carbon formation reactions (cracking and carbon monoxide reduction) do not involve CO2 but do involve hidrocarbons and CO, so the former is not counted, but the last two are.



#3 Ankit_Kumar

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Posted 09 January 2017 - 04:01 PM

The three main reactions for carbon formation are hydrocarbon cracking (Equations (i) and (ii)), carbon monoxide disproportionation (the Boudouard reaction) (Equation (iii)) and carbon monoxide reduction (Equation (iv)).

 

CH4 ⇌ C + 2H2     ΔH298 = +75 KJ mol–1 (i)

CnHm → nC + (m/2)H2 (ii)

2CO ⇌ C + CO     ΔH298 = –172 KJ mol–1 (iii)

CO + H2 ⇌ C + H2O     ΔH298 = –131 KJ mol–1 (iv)

So i am confident about your opinion.



#4 Sanjay shah

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Posted 11 January 2017 - 05:25 AM

Hi ankit

In reformer,  ch4 and other higher hydrocarbon converted into CO and  CO2, but co2 is not taking part in reaction .  That's why for considering  c mole , co2 is avoided.

 

CH4+H2O--> CO+3H2 

CO+H2O--> CO2+H2

-------------------------------

CH4+2H2O---->CO2+4 H2O

 

regards






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