Methods and systems for controlling the products of combustion

A combustion control method, comprising:

• providing a high concentration CO2 stream, an oxygen supply stream, and a combustion fuel stream, wherein each stream has a flow rate and a composition;
• splitting the high concentration CO2 stream into a primary diluent stream and a secondary diluent stream, each having a flow rate;
• utilizing a combustion system to perform the steps of:
• adjusting the primary diluent stream flow rate independently of the overall flow rate of the high concentration CO2 stream;
• combining the primary diluent stream and the oxygen supply stream to form an oxygenation stream;
• combusting the oxygenation stream and the combustion fuel stream in a primary combustion zone of a combustor to form a combustion products stream with a temperature and a composition;
• calculating, based upon a flow rate and a composition of the combustion fuel stream, a flow rate of the oxygen supply stream required to produce substantially stoichiometric combustion in the primary combustion zone;
• and
• adjusting the flow rate of the oxygen supply stream to the calculated flow rate required to produce substantially stoichiometric combustion in the primary combustion zone;
• wherein the combustion system comprises:
• a high concentration carbon dioxide (CO2) stream;
• at least one CO2 flow regulation device configured to adjust an overall flow rate of the high concentration CO2 stream and split the high concentration CO2 stream into a primary diluent stream having a flow rate and a secondary diluent stream having a flow rate, wherein the at least one flow regulation device is further configured to adjust the primary diluent stream flow rate independently of the overall flow rate of the high concentration CO2 stream;
• an oxygen supply stream having a flow rate;
• at least one oxygen flow regulation device configured to adjust the oxygen supply stream flow rate;
• a mixing device arranged to combine the primary diluent stream and the oxygen supply stream to form an oxygenation stream having a flow rate and an oxygen to CO2 ratio;
• a combustion fuel stream having a flow rate and a composition;
• a combustor consisting of at least a primary combustion zone and a burnout zone, wherein the combustor is configured to mix and combust the oxygenation stream and the combustion fuel stream within the primary combustion zone at a flame temperature and a primary residence time sufficient to produce a hot products stream at about equilibrium conditions, and configured to dilute the hot products stream with the secondary diluent stream within the burnout zone to form a combustion products stream having a lower temperature than the hot products stream;
• an expansion device configured to expand the combustion products stream to form an expanded products stream having a lower temperature than the combustion products stream;
• a control system, comprising:
• a first controller configured to regulate the flow rate of the oxygen supply stream in proportion to the flow rate of the combustion fuel stream so as to produce substantially stoichiometric combustion in the primary combustion zone;
• a second controller configured to regulate the oxygen to CO2 ratio of the oxygenation stream by controlling the primary diluent stream flow rate to produce a primary combustion zone flame temperature configured to provide:
• an adequate margin between a combustor average velocity, a blow-off limit of the combustor, and the primary residence time within the combustor sufficient to produce a combustion products stream at about equilibrium conditions;
• at least one temperature sensor operatively connected to the control system and the at least one CO2 flow regulation device, and configured to measure the temperature of the combustion products stream and send a signal to the control system, which is configured to adjust the secondary diluent stream flow rate based on the temperature of the combustion products stream to produce a desired temperature of the combustion products stream at some location after an exit of the combustion system;
• wherein the control system is configured to calculate a set point of the first controller required to produce substantially stoichiometric combustion in the primary combustion zone based upon a flow rate and a composition of the combustion fuel stream;
• and
• at least one load controller configured to control the flow rate of the combustion fuel stream to maintain a desired load condition in the expansion device.