5 replies to this topic

[daraj]

Hi,

 

does anyone know how to set up aspen plus/EDR to model say a condenser where as the gas mixture cools in the process side, because of equilibrium favoring, a couple of the components react and release heat at the same time(which also needs to be removed to reach the target outlet temperature). and then we need to export the exchanger to EDR to size it

[Pilesar]

Since the question is in the student section, I will respond as if you were a student...

If the quantity of heat released due to reaction were small compared to the condensation duty, I would ignore it as being covered by my equipment design safety factor. Otherwise, account for the duty in another way. For example, if the reaction duty were 25% of the condensation duty, I would consider increasing the feed flow by 25% before calculating the exchanger design in order to be conservative. You could instead model increased feed superheat by adding the duty to the original feed stream in the model, or a combination of the two methods. An even fancier way would be to adjust the heat of vaporization of the condensing stream so that the extra duty is automatically included. Check whether the reaction affects other important heat transfer parameters like surface tension or viscosity. 

[Bobby Strain]

I would ask AspenTech.

 

Bobby

[daraj]

Thanks to both of you, i will try to chk with aspentech

 

Pilesar iam trying to first have a heatex block to cool the gas down to target outlet temp. (no condensation only sensible cooling in this exchanger) and then stick a REQUIL to calculate outlet composition at this constant temperature . i can add the duties from heatex block and REQUIL to get the total cooling duty. But U may be a bit tricky

[daraj]

 

 You could instead model increased feed superheat by adding the duty to the original feed stream in the model, or a combination of the two methods. An even fancier way would be to adjust the heat of vaporization of the condensing stream so that the extra duty is automatically included. Check whether the reaction affects other important heat transfer parameters like surface tension or viscosity. 

 

i need to predict outlet composition of process gas as well which will keep changing as reaction proceeds along the length of the exchanger

 

[Pilesar]

Model the heat transfer in your reactor unit to determine the outlet composition. You will need a different simulation unit to use for the heat transfer equipment design which depends on density, velocity, viscosity, heat capacity, etc. Simplifying assumptions will have to be made somewhere. It may take some iteration between the reactor unit and the heat exchanger unit to match the process heat curve. I don't know the fidelity required for your simulation, but developing a user-added unit is a possibility although I would not recommend that