Method For Injecting Ballast Into An Oxycombustion Boiler

Abstract

A method for injecting fuel, oxidant, and ballast into an oxycombustoin boiler is presented.

1 . Method for injecting shielding gas into a boiler comprising;
 feeding at least one fuel stream and at least one oxidant stream, essentially devoid of nitrogen, to a combustion chamber wherein the fuel is substantially combusted to produce at least one combustion chamber jet and flue gas,   passing into a region of the combustion chamber a plurality of shielding gas streams,   wherein the shielding gas streams are located, oriented, and controlled in a manner appropriate to protect an element in the region   wherein said region is selected from the group consisting of:   the combustion chamber,   a zone within the combustion chamber of predominantly radiant heat transfer,   a zone within the combustion chamber of maximum heat flux,   a zone within the combustion chamber where the heat flux exceeds a predetermined value,   a zone within the combustion chamber where the flue gas temperature is at a maximum, and   a zone within the combustion chamber where the flue gas temperature exceeds a predetermined value,   a zone within the combustion chamber where heat exchangers are placed; and   wherein said element is selected from the group consisting of:   the walls of the combustion chamber,   the sides of the combustion chamber,   heat transfer elements positioned within the combustion chamber,   heat transfer elements positioned within a zone of predominantly radiant heat transfer within the combustion chamber, and   the boiler elements in contact with the flue gas.   
   
   
       2 . The method of  claim 1 , wherein the shielding gas streams are located, oriented, and controlled such that the shielding gas is injected vertically parallel with and substantially adjacent to the walls of the combustion chamber. 
   
   
       3 . The method of  claim 1 , wherein the shielding gas streams are located, oriented, and controlled such that the shielding gas is injected in a direction substantially perpendicular or substantially parallel to the direction of the combustion chamber jet. 
   
   
       4 . The method of  claim 1 , wherein the shielding gas streams are located, oriented, and controlled such that the shielding gas is injected in a direction substantially convergent to the direction of the combustion chamber jet. 
   
   
       5 . The method of  claim 1 , wherein the shielding gas streams are injected such that at least one of the shielding gas streams has a swirl rate between 0.05 and 5. 
   
   
       6 . The method of  claim 5 , wherein the shielding gas streams are injected such that at least one of the shielding gas streams has a swirl rate between 0.26 and 1.73. 
   
   
       7 . The method of  claim 1 , further comprising
 providing system data into a control system,   controlling the injection of the shielding gas streams with this control system.   
   
   
       8 . The method of  claim 7 , wherein the system data is selected from the group consisting of:
 fuel type,   fuel characteristics,   fuel flows,   oxidant characteristics,   oxidant flows,   ballast gas characteristics to the burners,   ballast gas flows to the burners,   boiler operating conditions,   exiting flue gas composition, and   exiting flue gas temperature.   
   
   
       9 . The method of  claim 1 , further comprising
 mounting sensors in or on the elements of the combustion chamber,   inputting the output of the sensors into a control system,   controlling the injection of the shielding gas streams with this control system.   
   
   
       10 . The method of  claim 9 , wherein the sensors measure a variable selected from the group consisting of wall temperature, tube skin temperature, water wall fluid temperature, tube fluid temperature, furnace gas temperature, and heat flux. 
   
   
       11 . The method of  claim 1 , wherein the shielding gas comprises recycled flue gas. 
   
   
       12 . The method of  claim 1 , wherein the shielding gas streams passing into the combustion chamber region comprises at least one frequency with an amplitude of vibration, and wherein the boiler system comprises at least one natural frequency. 
   
   
       13 . The method of  claim 12  where the ratio between the lowest frequency created by at least one of the shielding gas injections and the lowest natural frequency of the boiler system is comprised between 0 and 0.95. 
   
   
       14 . The method of  claim 13  where the ratio between the lowest frequency created by at least one of the shielding gas injections and the lowest natural frequency of the boiler system is comprised between 1.05 and 100. 
   
   
       15 . The method of  claim 13  where the ratio between the lowest frequency created by at least one of the shielding gas injections and the lowest natural frequency of the boiler system is comprised between 1.3 and 5. 
   
   
       16 . The method of  claim 13 , wherein the flow of the different shielding gas injections is controlled by the measure of the amplitude of the vibration at a location of the oxy-boiler selected from the group consisting of:
 burners,   oxy-boiler walls,   heat exchangers,   ducts,   stack,   fans.