Method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace, wherein at least two shafts are interconnected via a gas transfer channel, the method comprising, in production mode,
- loading the carbonate mineral rock at the a top of the furnace,
- preheating said rock,
- firing said rock with the decarbonation thereof into calcined material,
- cooling the calcined material via cooling air, and
- unloading the calcined material at the a bottom of the shafts,
- each shaft operating alternately in firing mode and in preheating mode, one shaft being in firing mode for a predetermined time period while at least one other shaft is in preheating mode, and vice-versa,
- the firing mode comprising:
- said loading of carbonate mineral rock at the top of the shaft in firing mode,
- in the presence of said preheated carbonate mineral rock descending into said shaft,
- combusting fuel in the presence of oxygen so as to obtain said firing of said rock and the decarbonation thereof into calcined material with the release of combustion fumes in the form of a gaseous stream descending co-currently in the shaft in firing mode, and
- said gaseous stream containing these combustion fumes moving from the shaft in firing mode to said at least one shaft in preheating mode using said gas transfer channel,
- the preheating mode comprising:
- said preheating of the loaded carbonate mineral rock via heat exchange with the gaseous stream containing the combustion fumes from the gas transfer channel, which is ascending in said at least one shaft in preheating mode, counter-currently to said loaded carbonate mineral rock, and
- discharging from the furnace a gaseous effluent based on the gaseous stream containing the combustion fumes, at the top of said at least one shaft in preheating mode,
- wherein said fuel combustion occurs in the presence of an excess of oxygen relative to stoichiometric requirements and wherein the method further comprises
- collecting a portion of the gaseous effluent discharged from the furnace,
- forming an oxidizing mixture by mixing said collected portion of the gaseous effluent discharged from the furnace with concentrated dioxygen, and
- introducing this oxidizing mixture at the top of the shaft in firing mode so as to ensure said fuel combustion in the presence of oxygen,
- the gaseous effluent discharged from the furnace being concentrated in CO2.