Process for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace, and furnace used

Method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace, wherein two shafts are interconnected by a gas transfer channel, wherein said gas transfer channel is a crossover channel that directly connects one shaft to the remaining shaft of the two shafts of said vertical shaft furnace or said gas transfer channel is formed from a crossover channel that connects peripheral channels arranged around each shaft in such a way as to allow an access to combustion gases from each shaft in the crossover channel, and wherein the furnace further comprises a source of air, oxygen enriched air, or oxygen and an injection device connected to the source of air, oxygen enriched air, or oxygen and arranged to inject the air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen into said gas transfer channel wherein:

• the injection device comprises at least one straight perforated injection unit introduced into the crossover channel and supplied by said source of air, oxygen enriched air, or oxygen, said injection unit comprises one or several orifices oriented to inject the air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen towards a top portion of the crossover channel;
• or
• the crossover channel has a ceiling and a longitudinal axis (L) and the injection device for injecting air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen comprises one or several openings provided in the ceiling of the crossover channel through which the air, oxygen enriched air, or oxygen can be supplied from said source of air, oxygen enriched air, or oxygen;
• the method comprising the steps of:
• loading a mineral rock at the top of the shafts, and
• unloading a calcined mineral rock at the bottom of the shafts,
• operating each shaft alternately in firing mode and in preheating mode, with one shaft being in firing mode for a predetermined period of time while the other shaft is in preheating mode, and inversely,
• firing the mineral rock, in the shaft in firing mode, comprising a combustion of fuel in the presence of gas containing oxygen so as to obtain the calcined mineral rock, an emission of combustion gases, and a passage of these combustion gases from the shaft in firing mode to the other shaft in preheating mode by means of said gas transfer channel,
• preheating said mineral rock, in the shaft in preheating mode, comprising a heat exchange between said mineral rock and said combustion gases from said gas transfer channel,
• wherein the method further comprises a step of injecting, air, oxygen enriched air, or oxygen from said source of air, oxygen enriched air, or oxygen into said gas transfer channel so as to oxidize unburnt products contained in the combustion gases passing through the gas transfer channel.