3 replies to this topic

[karthik.kattupalyam]

haiii ,

 

one of my plant manager given a problem to process department like he want to keep a  safety valve for a reactor means (he want to find design pressure of the safety valve.)

process is initial water(200lit)is at 90 C in reactor and mcb(4600lit) is at 120 C is transferred into the reactor after that reactor is closed and maintain the temp at 120 C by heating. after 1 hour the mcb is transferred into another vessel by through that generated pressure . so his ques is what is the max pressure will occur in the reactor having cap of 6.3kl

my calculation is 

PV=nRT 

I calculated like taken total  water vapour volume and moles. but they are telling like some amount of mcb will also vaporize at 120 C. ok i can calculate by using avg mol weight but i want to find how much amount of mcb is vaporize? Is mono chloro benzene vaporize at 120 deg c ?(its boling point is 132 C)

 

please guide how to solve this and let me know if you have more information is need for that.

Edited by karthik.kattupalyam, 26 September 2013 - 01:29 AM.

[breizh]

Consider this resource to support your query.

 

http://www2.questcon...rmo/dewbub.html

 

Hope this helps

 

Breizh

[karthik.kattupalyam]

Breizh:

 

thanks for the given information

 

can i calculate like total press= sum of that partial press 

so partial pressure = vapor pressure  at 120 deg * mole fraction?

 

can i do like that?  tell me pls

[MrShorty]

partial pressure = vapor pressure  at 120 deg * mole fraction?

If I understand what you are doing, this amounts to using Raoult's law to calculate the system pressure. This would work well for nearly ideal systems, however, mcb + H2O is probably not very ideal. Without looking it up, I would even expect it is nearly immiscible like other hydrocarbon/water systems.

 

Assuming I understand what you are trying to do, in order to rigorously calculate the system pressure, you are going to need a more involved calculation scheme. A flash calculation using either a phi-phi algorithm (like briezh's link uses) or a gamma-phi algorithm (I would probably assume phi=1 and poynting factor=1 since I would not expect the pressures to be very high) with appropriate interaction parameters.

 

One simplification I use for binary immiscible systems like this (assuming no dissolved gases or other compounds) -- assume the total pressure is the sum of the pure component vapor pressures. It's obviously not exact, but it is a good first approximation.