Combustion Apparatus

Abstract

A burner for a combustion apparatus, a combustion apparatus comprising such burners, and a method of operation of the same are described. The burner comprises: a fuel input conduit for supplying fuel to the burner; a combustion gas input conduit for supplying combustion gas to a first stage combustion site; an overfire gas input conduit for supplying overfire gas to a second stage combustion site; and gas supply means; wherein the gas supply means is adapted to supply gas switchably between a first mode of operation wherein air is supplied in suitable proportion to both the combustion gas input conduit and the overfire gas input conduit; and a second mode of operation wherein an oxygen containing gas other than air is supplied to the combustion gas input conduit and substantially no gas is supplied to the overfire gas input conduit.

1 . A burner for a combustion apparatus comprising:
 a. a fuel input conduit for supplying fuel to the burner;   b. a combustion gas input conduit for supplying combustion gas to a first stage combustion site;   c. an overfire gas input conduit for supplying overfire gas to a second stage combustion site; and   d. gas supply means;
 wherein the gas supply means is adapted to supply gas switchably between: 
 a first mode of operation wherein air is supplied in suitable proportion to both the combustion gas input conduit and the overfire gas input conduit; and 
 a second mode of operation wherein an oxygen containing gas other than air is supplied to the combustion gas input conduit and: substantially no gas is supplied to the overfire gas input conduit. 
   
     
     
         2 . A burner in accordance with  claim 1  wherein the gas supply means is adapted to supply an oxygen containing gas other than air comprising a mixture of an oxygen enriched gas and a second gas. 
     
     
         3 . A burner in accordance with  claim 2  wherein the oxygen enriched gas is substantially pure oxygen. 
     
     
         4 . A burner in accordance with  claim 2  wherein the second gas has a reduced nitrogen, content relative to air. 
     
     
         5 . A burner in accordance with  claim 4  wherein the second gas is recycled flue gas. 
     
     
         6 . A burner in accordance with  claim 1  wherein the oxygen containing gas other than air has a proportion of oxygen which gives a, combustion process performance generally equivalent to that achieved with air, for example being around 20 to 50% by volume. 
     
     
         7 . A burner in accordance with  claim 1  wherein the gas supply means is adapted to switchably supply either air or the oxygen containing gas other than air additionally to the fuel input conduit to at least assist in transporting the fuel to the combustion chamber. 
     
     
         8 . A burner in accordance with  claim 7  wherein the gas supply means includes varying means for varying the proportion of gas supplied to one or more of the fuel input conduit, the combustion gas input conduit and the overfire gas input conduit. 
     
     
         9 . A burner in accordance with  claim 1  wherein the combustion gas input conduit comprises plural fluidly independent input conduits fluidly connected to the gas supply means. 
     
     
         10 . A combustion-apparatus comprising:
 a. a combustion chamber; and   b. one or more burners located so as to define combustion sites within the combustion chamber, each burner comprising a fuel input conduit for supplying fuel to the burner, a combustion gas input conduit for supplying combustion gas to a first stage combustion site, an overfire gas input conduit for supplying overfire gas to a second stage combustion site, and gas supply means, wherein the gas supply means is adapted to supply gas switchably between a first mode of, operation wherein air is supplied in suitable proportion to both the combustion gas input conduit and the overfire gas input conduit, and a second mode of operation wherein an oxygen containing gas other than air is supplied to the combustion gas input conduit and substantially no gas is supplied to the overfire input conduit.   
     
     
         11 . A combustion apparatus in accordance with  claim 10  comprising a boiler for generating steam. 
     
     
         12 . A combustion apparatus in accordance with  claim 10  comprising a fuel supply of pulverized coal. 
     
     
         13 . A combustion apparatus in accordance with  claim 10  wherein the combustion gas input conduit is a first combustion gas input conduit comprising a part of the burner and including at least one further fluidly independent combustion gas input conduit fluidly connected to the gas supply means for supplying gas directly to at least one of the burner and another component of the combustion apparatus. 
     
     
         14 . A combustion apparatus in accordance with  claim 10  including a flue gas recirculation conduit. 
     
     
         15 . A combustion apparatus in accordance with  claim 14  wherein the flue gas recirculation conduit is fluidly connected to one or more of the gas supply means and at least one of the fuel input conduit and the combustion gas input conduit such that a mixture, including flue gas may be supplied to the combustion chamber in use in the, second mode of operation. 
     
     
         16 . A method of firing a burner in a combustion apparatus comprising firing the burner selectively in one of two modes of operation, comprising in a first mode of operation:
 supplying fuel to the burner;   supplying combustion gas comprising air to a first stage combustion site;   supplying overfire gas comprising air to a second stage combustion site;   causing combustion of fuel to occur in a two stage process;   
       and in a second mode of operation:
 supplying fuel to the burner; 
 supplying combustion gas comprising an oxygen containing gas other than air to a first stage combustion site; 
 causing combustion of fuel to occur in a single stage process.