7 replies to this topic

[A mukherjee]

Hello all,
I am trying to simulate a reactor for the combustion of mixture of methane & ethylene,with oxygen.
(CH4+C2H4+5O2=3CO2+4H2O)
I am using the Conversion reactor from General Reactor option available in HYSYS & Conversion reaction from reaction package.
But the major problem I am facing with the conversion of METHANE.
The feed contains CO2(68%),H2O(31%),N2,CH4(900 PPM),C2H4(200 PPM).
Despite using oxygen in excess amount I am getting 100% conversion of ethylene & only 25% of methane.

In HYSYS we can choose only one Base component & can specify its conversion.In first case I have chosen this component as ethylene in & specified its conversion as 100%.Then I tried the same with methane.But in both the cases I got the same result of 100% conversion of ethylene & 25% of methane.

Do I have to put two reactors in series, first one for conversion of ethylyne & 2nd one for methane?Is there any other way out?

[A mukherjee]

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[abhi_agrawa]

Mukharjee,

I believe that you are trying to model two different reaction as one reaction. As a result of which when one of the reactants is fully consumed, Hysys assumes no more reaction taking place. To clarify further, let us assume you have a total of 100 moles of reaction mixture. Ethylene is 200 ppm = 0.02 moles and methane is 0.09 moles. So Hysys calculates that when 0.02 moles of Ethylene and 0.02 moles of methane have reacted, the reaction stops as the reaction mixture does not have any Ethylene.

You should correct you modeling.

Hoe this helps,
Abhishek

[A mukherjee]

Thnxx for identifying the problem.Can you suggest me any way how can I avoid that?

[A mukherjee]

Also can you give me any idea about whether it is necessary to carry out combustion of methane at high pressure such as 17 bar(g) & generally what is feed the temperature at which such reaction is carried out?

[Padmakar Katre]

Hi,
Before I make specifc commet, let me make you understand that there is difference in terminology i.e. when you are using a converion reactor you you will have certain % of conversion of base component. The reaction here is oxidation and not combustion, yes there is difference in these two terms.
Coming to the specific issue you mentioned here, you can model the reactions with the Gibbs reactors options availabe with Hysys, there is no need to specify the reactions sets in the reactions tab of SimBasis manager window. This is a typical way of moedling these reactions, e.g. gas turbine (combsuter is a Gibbs reactor).
Do the preliminary hand calculations for the feed flows based on the stoichiometry. Define the flows of reactants accordingly. Here I envisage the issue may be with oxygen flow, which may or may not be sufficient for complete conversion of both reactants.
Please do let us know in case if the problem still persists.

[A mukherjee]

Thanxx Padmakar..Indeed the amount of oxygen was the source of problem.Now I have completed the simulation using conversion reactor.
The reaction between methane & oxygen is carried out in presence of palladium catalyst at 450degc at around 18 barg pressure.
Now I have a series of questions regarding it
1.Should I use heterogeneous catalytic reaction option instead of conversion reaction to get more accurate result?
2.From where can I get numerator & denominator constant values?
3.What is the order of such reaction?(availability of any document related with it will be highly appreciated)
4.Is there any option to insert catalyst proprety in the simulation?
5.My last question:Is reaction operating pressure has got any influence on space velocity?

Thnxx in advance.

[A mukherjee]

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