Apparatus and method of controlling the thermal performance of an oxygen-fired boiler

Abstract

A method of controlling the operation of an oxy-fired boiler includes combusting a fuel that comprises oil heavy residues in a boiler, the oil heavy residues including hydrocarbon molecules having a number average molecular weight from approximately 200 to approximately 3000 grams per mole, discharging flue gas from the boiler, recycling a portion of the flue gas to the boiler, combining a first oxidant stream with the recycled flue gas to form a combined stream, splitting the combined stream into a plurality of independent split streams, introducing each independent split stream at a different elevation of the boiler, and controlling independently a parameter of each of the independent split streams to adjust the heat release at each respective elevation of the boiler to vary the heat release profile of the boiler by adding a second oxidant stream to each respective independent split stream to form respective independent oxygen enriched split streams.

What is claimed is: 
     
         1 . A method of controlling the operation of an oxy-fired boiler, the method comprising:
 combusting a fuel that comprises oil heavy residues in a boiler, the oil heavy residues including hydrocarbon molecules having a number average molecular weight from approximately 200 to approximately 3000 grams per mole;   discharging flue gas from the boiler;   recycling a portion of the flue gas to the boiler;   combining a first oxidant stream with the recycled flue gas to form a combined stream;   splitting the combined stream into a plurality of independent split streams;   introducing each independent split stream at a different elevation of the boiler; and   controlling independently a parameter of each of the independent split streams to adjust the heat release at each respective elevation of the boiler to vary the heat release profile of the boiler by adding a second oxidant stream to each respective independent split stream to form respective independent oxygen enriched split streams.   
     
     
         2 . The method according to  claim 1 , wherein:
 the oil heavy residues comprise asphaltene.   
     
     
         3 . The method according to  claim 1 , wherein:
 the boiler is a tangentially fired boiler.   
     
     
         4 . The method according to  claim 1 , wherein:
 controlling independently the parameter of each independent split stream further includes changing a heat absorption in the boiler to a desired heat absorption pattern.   
     
     
         5 . The method according to  claim 1 , wherein:
 at least one of the split streams is introduced into the boiler at a hopper zone located below a windbox, at the windbox and/or in an overfire compartment located above the windbox.   
     
     
         6 . The method according to  claim 1 , wherein:
 at least a portion of the combined stream is introduced into the boiler in a lower portion of the windbox.   
     
     
         7 . The method according to  claim 6 , wherein:
 the at least one split stream that is introduced into the boiler at the windbox is about 50 to about 100 weight percent of the combined stream.   
     
     
         8 . The method according to  claim 1 , wherein:
 the at least one split stream is introduced into the boiler in a lower portion of an overfire compartment.   
     
     
         9 . The method according to  claim 1 , wherein:
 the at least one split stream is introduced into the boiler in an upper portion of an overfire compartment.   
     
     
         10 . A method comprising:
 combusting a fuel that comprises oil heavy residues in a boiler, where the oil heavy residues that comprise hydrocarbon molecules having a number average molecular weight from 200 to 3000 grams per mole;   discharging flue gas from the boiler;   recycling a portion of the flue gas to the boiler;   combining a first oxidant stream with the recycled flue gases to form a first combined stream;   splitting the first combined stream into a plurality of independent split streams;   combining a second oxidant stream to each respective independent split stream provided to the boiler to form respective independent oxygen enriched split streams;   introducing each independent oxygen enriched split stream to a different elevation of the boiler; and   controlling independently the amount of the second oxidant stream added to each respective independent split stream to adjust the heat release at each respective elevation of the boiler to vary the heat release profile of the boiler;   wherein the first combined stream, the independent split streams, and the independent oxygen enriched split streams do not carry the fuel for the boiler.   
     
     
         11 . The method according to  claim 10 , wherein:
 the boiler is a tangentially fired boiler.   
     
     
         12 . The method according to  claim 10 , wherein:
 adding the second oxidant stream to form the respective oxygen enriched split streams is conducted at a position proximate to a point of entry into the boiler.   
     
     
         13 . The method according to  claim 10 , wherein:
 the respective split streams are sequentially introduced into the boiler.   
     
     
         14 . The method according to  claim 10 , wherein:
 at least one respective oxygen enriched split stream is introduced into the boiler at a hopper zone located below a windbox.   
     
     
         15 . The method according to  claim 14 , wherein:
 the oxygen enriched split stream introduced into the boiler at the windbox comprises about 50 to about 100 wt % oxygen, based on the total weight of the stream.   
     
     
         16 . The method according to  claim 14 , wherein:
 each oxygen enriched split stream is introduced into the boiler via an annular space disposed around an inner port, where the inner port introduces the fuel and transport air into the boiler.   
     
     
         17 . The method according to  claim 10 , wherein:
 the boiler is a wall fired boiler.   
     
     
         18 . The method according to  claim 10 , wherein:
 controlling independently the parameter of each respective oxygen enriched split stream introduced to the boiler changes the heat pattern of the boiler.   
     
     
         19 . The method according to  claim 14 , wherein:
 at least one respective oxygen enriched split stream is introduced into the boiler at an overfire compartment at the hopper zone; and   wherein the oxygen enriched split stream introduced into the overfire compartment at the hopper zone comprises up to 50 wt % oxygen based on the total weight of the oxygen enriched split stream.   
     
     
         20 . A system comprising:
 an air separation unit;   a boiler configured to combust oil heavy residues, the oil heavy residues comprising hydrocarbon molecules having a number average molecular weight from 200 to 3000 grams per mole;   a pollution control system;   a gas processing unit, wherein the air separation unit is upstream of the boiler, the pollution control system and the gas processing unit, wherein the boiler is upstream of the pollution control system and the gas processing unit, and wherein flue gas is recycled from the gas processing unit to the boiler via the air separation unit; and   a control system configured to control the addition of a first oxidant stream to the recycled flue gas to form a combined stream and to control the addition of a second oxidant stream to a plurality of independent split streams formed from the combined stream to vary the heat release profile of the boiler;   wherein each of the independent split streams to which the second oxidant stream is added is introduced to a different elevation of the boiler.