2 replies to this topic

[trituty1989]

Hi,

 

I'm having a problem that i cannot seem to troubleshoot. My design team was tasked to carry out a simulation of the production of VAM using aspen hysys v8.6. We have come up with a successfully converged system for the first part of the project and right now I'm in charge with optimizing the reactor section. Since the conversion of ethylene was originally at ~9% using the heat transfer tab under the Design parameters page of the reactor set to Direct Q value, i thought in order to carry out a more 'real' process is to switch to the 'Formula' option of the SS Duty calculation option. The coolant I'm using is water-steam at 8bar ~130degC. But the problem is that when i switch to this formula option, the conversion drops to 0.4%. I've increased the flowrate of the coolant and it does not make much of a difference, even changing the dimensions didn't help. I can't upload my hysys file here but if there are any kind souls with sharper eyes and mind, i could send it over to your email.

[shantanuk100]

HI Trituty,

 

Could you mention the types of reaction and reactor you have considered and kinetic reaction parameters if any ?

Also, could you mention the balanced reaction that you have considered as the reaction set for the reactor, if it is not proprietary ?

 

Regards,

Shantanu

[trituty1989]

HI Trituty,

 

Could you mention the types of reaction and reactor you have considered and kinetic reaction parameters if any ?

Also, could you mention the balanced reaction that you have considered as the reaction set for the reactor, if it is not proprietary ?

 

Regards,

Shantanu

Hi Shantanu,

 

The reaction is as follows:

 

C2H4 +CH3COOH + 0.5 O2 -> CHOCOCH3 + H2O

 

and the secondary reaction is 

 

C2H4 +3O2 -> 2CO2 +2H2O

 

with impurities of ethane in the ethylene feed stream and formic acid in the acetic acid stream. The reactor considered in this case is a shell and tube heat exchanger type of reactor and the overall reaction rates are as follows:

 

R1= 0.1036e(-3674/T) ((pEpHAcpO(1+1.17pW))/((1+0.583pO(1+1.7pW))(1+6.8pHAc))

R2= 1.935x10^5 (-10116/T)((pO(1+0.68pW))/(1+0.76pO(1+0.68pW))

 

These can be found in the Luyben paper "Design and Control of a Modified Vinyl Acetate Monomer Process"