Rob
Ansys Employee

OK, a few slight changes will be needed. 

How is the chamber at 9 bar if the outlet vents to atmosphere? 

What is the volume fraction of droplets? You may be better off with DPM so read up on the models. 

Put all of the gas species into one phase, you can then react at your convenience. So, you'll have a liquid phase/spray and a gas phase containing the four species (or more than four if the reactions get complicated).