Using Electrolytes in HYSYS - Some things are good to know

HYSYS now allows you to use electrolytes through Aspen Properties. There are a couple of things you need to keep in mind to use this successfully. The key is that HYSYS uses the Apparent mode. Initially I thought, why take this option? Why not take the true approach which doesn't suffer from some of the below issues. It would appear that it is you, the users that have preferred this approach. I was a bit sceptic at first, but a recent visit to hard core Aspen Plus users convinced me that users indeed prefer to juggle with molecules, not with ions.

That being said, on to the practial stuff:
When using apparent mode, you have to make sure that you enter any component that will disappear from the aqueous phase in your initial composition. As an example, if you intend to model a solution of Na2CO3 that will get acidified using for example H2SO4, this will only work properly if you represent the Na2CO3 by NaOH and CO2 in you feed stream. When the conditions are such that the CO2 and NaOH will form dissolved ions, this will be honoured. But, if you add enough H2SO4, the CO2 will go to the vapour phase.