A method of operating a plant having a furnace including at least two vertical shafts connected by an overflow duct, wherein at least one burner is arranged above the overflow duct in each case such that the burner gases therefrom flow downward in burning operation of the respective shaft. A cooling gas supply is provided beneath the overflow duct in each case such that, in combination with the operation of a burner in the burner-operated shaft, the burner gas flowing downward is deflected in the direction of the overflow duct by the cooling gas ascending in the burner-operated shaft, and a supply of cooling gas is adjusted such that the temperature of the burner charge through which the burner gas flows at least in the burner-operated shaft is kept above the deacidification temperature thereof.

This invention discloses a calcination process to produce high purity CO.sub.2 from solids containing CaCO.sub.3 which operates cyclically and continuously on the solids, arranged in a packed or a moving bed, and wherein each cycle comprises a first step where the combustion at atmospheric pressure of a fuel in the bed of solids containing CaCO.sub.3 heats them up to 800-900? C. and a second step wherein a vacuum pressure between 0.05 and 0.5 atm is applied to extract pure CO.sub.2 from the solids containing CaCO.sub.3 while cooling them by 30-200? C. Said combustion can be carried out directly with air, oxygen enriched air or O.sub.2/CO.sub.2 mixtures when the process is applied to the calcination of a continuous flow of limestone in a moving bed shaft kiln. The process is also applied to calcine CaCO.sub.3 formed in reversible calcium looping processes comprising a carbonation reaction step to form CaCO.sub.3 from CaO.

This invention discloses a calcination process to produce high purity CO.sub.2 from solids containing CaCO.sub.3 which operates cyclically and continuously on the solids, arranged in a packed or a moving bed, and wherein each cycle comprises a first step where the combustion at atmospheric pressure of a fuel in the bed of solids containing CaCO.sub.3 heats them up to 800-900? C. and a second step wherein a vacuum pressure between 0.05 and 0.5 atm is applied to extract pure CO.sub.2 from the solids containing CaCO.sub.3 while cooling them by 30-200? C. Said combustion can be carried out directly with air, oxygen enriched air or O.sub.2/CO.sub.2 mixtures when the process is applied to the calcination of a continuous flow of limestone in a moving bed shaft kiln. The process is also applied to calcine CaCO.sub.3 formed in reversible calcium looping processes comprising a carbonation reaction step to form CaCO.sub.3 from CaO.

Process for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace, containing at least two shafts (1, 2) interconnected by a gas transfer channel (3), each shaft operating alternately in firing mode and in preheating mode, the firing mode comprising a combustion of fuel in the presence of air so as to obtain a firing of the rock to give calcined rock, an emission of combustion gases, and a passage of these gases from one shaft to the other by means of said channel (3), the preheating mode comprising a heat exchange between said rock and said combustion gases from said channel (3), this process additionally comprising an injection of supplementary air into said channel (3) with oxidation of unburnt products contained in the combustion gases passing through this channel.

Process for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace, containing at least two shafts (1, 2) interconnected by a gas transfer channel (3), each shaft operating alternately in firing mode and in preheating mode, the firing mode comprising a combustion of fuel in the presence of air so as to obtain a firing of the rock to give calcined rock, an emission of combustion gases, and a passage of these gases from one shaft to the other by means of said channel (3), the preheating mode comprising a heat exchange between said rock and said combustion gases from said channel (3), this process additionally comprising an injection of supplementary air into said channel (3) with oxidation of unburnt products contained in the combustion gases passing through this channel.

A method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace including the steps of collecting a portion of the gaseous effluent discharged, in preheating mode, from the furnace shaft in a recirculating circuit, forming an oxidizing mixture by mixing the portion collected from the gaseous effluent with concentrated dioxygen from a dioxygen source, and inserting the oxidizing mixture into the top of the shaft in firing mode so as to ensure the combustion of fuel in the presence of oxygen. The gaseous effluent discharged from the furnace having a high concentration of CO.sub.2.

A method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace including the steps of collecting a portion of the gaseous effluent discharged, in preheating mode, from the furnace shaft in a recirculating circuit, forming an oxidizing mixture by mixing the portion collected from the gaseous effluent with concentrated dioxygen from a dioxygen source, and inserting the oxidizing mixture into the top of the shaft in firing mode so as to ensure the combustion of fuel in the presence of oxygen. The gaseous effluent discharged from the furnace having a high concentration of CO.sub.2.

A method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace including the steps of collecting a portion of the gaseous effluent discharged, in preheating mode, from the furnace shaft in a recirculating circuit, forming an oxidizing mixture by mixing the portion collected from the gaseous effluent with concentrated dioxygen from a dioxygen source, and inserting the oxidizing mixture into the top of the shaft in firing mode so as to ensure the combustion of fuel in the presence of oxygen. The gaseous effluent discharged from the furnace having a high concentration of CO.sub.2.

A method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace including the steps of collecting a portion of the gaseous effluent discharged, in preheating mode, from the furnace shaft in a recirculating circuit, forming an oxidizing mixture by mixing the portion collected from the gaseous effluent with concentrated dioxygen from a dioxygen source, and inserting the oxidizing mixture into the top of the shaft in firing mode so as to ensure the combustion of fuel in the presence of oxygen. The gaseous effluent discharged from the furnace having a high concentration of CO.sub.2.

A method for calcining mineral rock in a regenerative parallel-flow vertical shaft furnace including the steps of collecting a portion of the gaseous effluent discharged, in preheating mode, from the furnace shaft in a recirculating circuit, forming an oxidizing mixture by mixing the portion collected from the gaseous effluent with concentrated dioxygen from a dioxygen source, and inserting the oxidizing mixture into the top of the shaft in firing mode so as to ensure the combustion of fuel in the presence of oxygen. The gaseous effluent discharged from the furnace having a high concentration of CO.sub.2.