Specialty Chemistry Forums > Chemical Engineering Forum
Reactor pressure calculation
jacarandaspoon:
I am looking at designing a reactor for a reaction which contains 0.6 mL 1M HCl, 3 mL H2O and 4 mL 30% ammonia. It's been a long time since I did any undergrad chemistry, can someone please remind be how to calculate the pressures that we're going to generate here and does it depend on the vessel size?
Enthalpy:
30%w/w ammonia is about the solubility limit at room temperature, meaning 1atm ammonia partial pressure. If air is present before the volume is constrained, already 1+1atm absolute pressure is expected.
But this depends already on the presence of water before or after the volume is constrained. Dilution would reduce the ammonia partial pressure. By the way, I wouldn't trust a linear formula in this case, because the strong proportion of ammonia molecules in the solution lets them interact. This needs an experimental curve.
What can still happen is that the heat from the reaction with the acid reduces the solubility more efficiently than it reduces the proportion of ammonia. Then, the pressure may increase. This needs a numerical verification, based on the enthalpies of formation of HCl, NH3 and NH4Cl, all in water solution. The big ammonia concentration changes its heat of formation in solution, but I would just start with the heat of formation in dilute solution, hoping that the result is already clear enough.
MNIO:
I don't understand. (1) You're trying to design a reactor for reaction 0.6 mL HCl, 3mL of H2O and 5mL of 30% NH3(in water?), 8.6mL in total? (2) you want to know if pressure depends on volume?, (3) you haven't taken undergrad chemistry for a long time?
I'm sorry but this makes no sense. What exactly are you trying to make?
jacarandaspoon:
Sorry I left out a couple of important points:
There are a range of ionic salts in the reaction mixture as well. None of which will contribute to the pressure. This is the current scale of the reaction which is done in a pressure vessel which we have no information on. We are wanting to scale this to a 1L reaction. The reaction is performed at 250 degC.
Borek:
How/when do you mix the reactants? HCl/NH3 react very fast, you will be mostly limited by the mixing speed.
Is there a headspace over the mixture?
Navigation
[0] Message Index
[#] Next page
Go to full version