This is a knauff product which I believe he imports from Belgium. What is relevance of coal powered fire station is their a by production it
The raw material is harvested from the waste from coal fire power stations . When you burn coal you but lots of sulphur compounds into the atmosphere causing acid rain. the way they control this is by using "scrubbers" to pull the sulphur compounds out of the system and tie them up as Calcium sulphate. this is then calcined at relatively high temperature to form the Alpha Hemi Hydrate. Its more environmentally friendly than cement but not as good as Anhydrite.
Another cement replacement product PFA is also harvested from the same source and this is in world wide shortage at present de to the closure of so many coal fired stations. it sort of follows that Alpha Hemi will go the same way at some point.