A method is provided for producing carbon dioxide by combusting a carbonaceous fuel with oxygen or with a gas mixture containing more than 25 mol % of oxygen obtaining a flue gas mixture, wherein the flue gas mixture is processed obtaining a secondary gas mixture containing carbon dioxide and oxygen, and wherein a part of the oxygen contained in the secondary gas mixture is catalytically reacted with a first auxiliary fuel in a reactor system comprising a series of multiple reactors, obtaining further carbon dioxide and water. A further part of the oxygen contained in the secondary gas mixture is catalytically reacted with a second auxiliary fuel in the reactor system. A corresponding apparatus is also described herein.

A method is provided for producing carbon dioxide by combusting a carbonaceous fuel with a oxygen or with a gas mixture containing more than 25 mol % of oxygen obtaining a flue gas mixture, wherein the flue gas mixture is processed obtaining a secondary gas mixture containing carbon dioxide and oxygen, and wherein a part of the oxygen contained in the secondary gas mixture is catalytically reacted with a first auxiliary fuel in a reactor system comprising a series of multiple reactors, obtaining further carbon dioxide and water. A further part of the oxygen contained in the secondary gas mixture is catalytically reacted with a second auxiliary fuel in the reactor system. A corresponding apparatus is also described herein.

A method of reducing plant emissions includes providing a MPC model for a flaring process including one-to-one models between controlled variables (CVs) including a smoke count and/or a flare count (CV1) and a noise level (CV2), and flow of assist gas as a manipulated variable (MV) and another process gas flow as a disturbance variable (DV). The MPC model receives sensed flare-related parameters during the flaring process including a measure of CV1 (CV1*) and CV2 (CV2*). Provided CV1* is above a minimum setpoint for CV1 (CV1 setpoint) and CV2* is above a setpoint for CV2 (CV2 setpoint), the flaring process is automatically controlled using the MPC model which determines an updated flow setpoint for MV from CV1* and CV2*, the CV1 and CV2 error, and the identified one-to-one models.