I worked for years in the power industry where boiler chemicals were used as a matter of course. Chemicals never leave a boiler in dry steam but do get carried over in wet steam. All steam has some small percentage of moisture carried with it and that part can carry things like TSP with it. Unless you have a boiler designed to separate steam from the water you will carry over lots of moisture with the steam which means you will also carry over lots of your chemicals. The makeup water in such a system will need some chemical treatment or you will slowly run out of it and end up with an untreated boiler water system. If you use only volatile chemicals for water treatment, things like ammonia to control pH, every drop of steam will carry off its own fraction of the chemical and makeup water will need to be treated just like the initial fill water was.