What role does carbon play in the calcination of strontium carbonate in step 1 of the strontian process?

Question

Wikipedia attempts to discuss the chemistry here, with the concern,

Where does the second C go?

Clearly, someone has subsequently attempted to balance $\ce{SrCO_3}+\ce{C}+\ce{H_2O}\stackrel{?}{\to}\ce{Sr(OH)_2}+\ce{CO_2}$ by doubling $\ce{CO_2}$ on the right-hand side, but this doesn't balance oxygen. Indeed, it's not hard to see this equation cannot be balanced without removing elemental carbon. If for every mole of the consumed carbonate we consume $a$ moles of $\ce{C}$, we must produce $a+1$ moles of $\ce{CO_2}$, and hence to balance hydrogen (oxygen) requires $1$ ($2a+1$) moles of $\ce{H_2O}$, so $a=0$.

This is all an attempt to make sense of the following paraphrase of Das Mineralreich:

Strontium carbonate is calcined with carbon in the presence of steam to form strontium hydroxide. The strontium and carbon dioxide formed are rejoined later in the process, forming strontium carbonate once again.

Does "calcined with carbon" imply carbon isn't consumed, but is important to have present (e.g. as a catalyst)? Or should another species be present in this equation? I assume the former, because if so the entire process has no net chemical effect; it simply relocates sugars in molasses, which is the goal of the process. If I'm right, carbon's role in the calcination will be in affecting the reaction mechanism for $\ce{SrCO_3}+\ce{H_2O}\to\ce{Sr(OH)_2}+\ce{CO_2}$, hence my tag choice.

Answer 1

I think Wikipedia's equation is not a correct representation. In the Mineralreich (Wiki link is based on Scribd, whereas the same is available on Internet Archive). With a little bit of effort one can locate the relevant paragraph

Verwendung. Strontianit ist das am leichtesten zu verarbeitende Rohmaterial für Strontiumpräparate und wird daher in Westfalen, wo er in genügender Mächtigkeit vorkommt, durch Bergbau gewonnen. Für seine Verwendung ist bemerkenswert, dass die Kohlensäure nicht wie bei Kalkspat durch einfaches Erhitzen ausgetrieben werden kann, er muss hierzu entweder in Wasserdampf oder mit Kohle, am besten mit beiden erhitzt werden. Das so oder aus dem Nitrat erzeugte Strontiumoxyd und -hydroxyd wird in der Zuckerinduslrie verwendet, um aus der Melasse noch den letzten Rest Zucker zu gewinnen. Zucker verbindet sich mit Strontian zu schwer löslichem Saccharat, einer Strontianzucker verbindung, und kann als solches von der Melasse abgeschieden werden.

Usage. Strontianite is the easiest raw material for strontium preparations to process and is therefore obtained by mining in Westphalia, where it occurs in sufficient abundance. It is noteworthy for its use that the carbonic acid cannot be expelled by simple heating, as is the case with calcite; it must be heated for this purpose either in steam or with coal, preferably with both. The strontium oxide and hydroxide produced in this way or from the nitrate is used in the sugar industry to extract the last bit of sugar from molasses. Sugar combines with strontian to form sparingly soluble saccharate, a strontian sugar compound, and as such can be separated from the molasses.

Translated with www.DeepL.com/Translator (free version)

I think the above paragraph is self-explanatory. $\ce{SrCO3}$ cannot be decomposed like calcium carbonate and we need a powerful reducing environment. It must be a two step reaction. One would get $\ce{SrO}$ first by strong heating in the presence of carbon and steam would convert the $\ce{SrO}$ to $\ce{Sr(OH)2}$. Wiki's equation attempts to combine both, as if it were a simultaneous reaction.