Co-firing combustor with gas fuel and liquid ammonia

Abstract

Co-firing a combustor with gas fuel and ammonia using various approaches is disclosed. Each method fires a gas fuel in a primary combustion zone using a head end fuel nozzle, in a secondary combustion zone using a first axial fuel stage (AFS) injector set, and/or a tertiary combustion zone using a second AFS injector set over a particular combustor load range, and transitions to firing with ammonia using an ammonia atomizer. The methods may transition to ammonia combustion alone or ammonia with gas fuel combustion. The cross flow of the first AFS injector set stabilizes combustion of ammonia, and the second AFS injector set provides a quenching effect, each of which contributes to efficient ammonia combustion with or without gas fuel combustion.

What is claimed is: 
     
         1 . A method, comprising:
 in a combustor including a head end (HE) fuel nozzle set aimed into a combustion liner to combust fuel in a primary combustion zone, a first axial fuel stage (AFS) injector set aimed into the combustion liner to combust fuel in a secondary combustion zone downstream of the primary combustion zone, and a second AFS injector set aimed into the combustion liner to combust fuel in a tertiary combustion zone downstream of the secondary combustion zone, and an ammonia atomizer aimed into the combustion liner to combust ammonia in at least the primary combustion zone, performing the following:   for a first combustor load range from a 0% combustor load up to a 50% combustor load, fueling the HE fuel nozzle set to introduce and combust a gas fuel in the primary combustion zone;   for a second combustor load range between a 10-20% combustor load range up to the 50% combustor load, additionally fueling the first AFS injector set to introduce and combust the gas fuel in the secondary combustion zone;   for a third combustor load range between a 35% combustor load and the 50% combustor load, additionally fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone;   at the 50% combustor load, transitioning to an ammonia fueling mode by stopping supply of the gas fuel to the HE fuel nozzle set, the first AFS injector set, and the second AFS injector set and starting combusting ammonia in at least the primary combustion zone using the ammonia atomizer; and   for a fourth combustor load range between a greater than 50% combustor load and a 100% combustor load, fueling only the ammonia atomizer to introduce and combust ammonia in at least the primary combustion zone.   
     
     
         2 . The method of  claim 1 , wherein, while gradually increasing a fuel mass flow rate (FMFR) of ammonia to the ammonia atomizer, the transitioning includes: gradually reducing the FMFR of the gas fuel to the HE fuel nozzle set to zero, then gradually reducing the FMFR of the gas fuel to the first AFS injector set to zero, and then gradually reducing the FMFR of the gas fuel to the second AFS injector set to zero. 
     
     
         3 . The method of  claim 2 , wherein the transitioning further includes:
 temporarily maintaining the FMFR of ammonia to the ammonia atomizer at a first current level prior to starting the gradual reducing of the FMFR of the gas fuel to the first AFS injector set to zero and continuing the gradual increasing of the FMFR of ammonia to the ammonia atomizer after starting the gradual reducing of the FMFR of the gas fuel to the first AFS injector set to zero, and   temporarily maintaining the FMFR of ammonia to the ammonia atomizer at a second current level prior to starting the gradual reducing of the FMFR of the gas fuel to the second AFS injector set to zero and continuing the gradual increasing of the FMFR of ammonia to the ammonia atomizer after starting the gradual reducing of the FMFR of the gas fuel to the second AFS injector set to zero.   
     
     
         4 . The method of  claim 3 , wherein the transitioning further includes setting the FMFR of ammonia to the ammonia atomizer at a maximum desired level in response to the FMFR of the gas fuel to the second AFS injector reaching zero. 
     
     
         5 . The method of  claim 1 , further comprising, for the fourth combustor load range between the greater than 50% combustor load and the 100% combustor load, injecting only air using the HE fuel nozzle set, the first AFS injector set, and the second AFS injector set. 
     
     
         6 . A method, comprising:
 in a combustor including a head end (HE) fuel nozzle set aimed into a combustion liner to combust fuel in a primary combustion zone, a first axial fuel stage (AFS) injector set aimed into the combustion liner to combust fuel in a secondary combustion zone downstream of the primary combustion zone, and a second AFS injector set aimed into the combustion liner to combust fuel in a tertiary combustion zone downstream of the secondary combustion zone, and an ammonia atomizer aimed into the combustion liner to combust ammonia in at least the primary combustion zone, performing the following steps during a first co-fired mode:   for a first combustor load range from a 0% combustor load up to a 50% combustor load, fueling the HE fuel nozzle set to introduce and combust a gas fuel in the primary combustion zone;   for a second combustor load range between a 10-20% combustor load range up to the 50% combustor load, additionally fueling the first AFS injector set to introduce and combust the gas fuel in the secondary combustion zone;   for a third combustor load range between a 35% combustor load and the 50% combustor load, additionally fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone; and   for a fourth combustor load range between a 20% combustor load and a 100% combustor load, fueling the ammonia atomizer to introduce and combust ammonia in at least the primary combustion zone.   
     
     
         7 . The method of  claim 6 , further comprising: at the 50% combustor load, transitioning to ammonia fuel operation by stopping the fueling of the HE fuel nozzle set, the first AFS injector set, and the second AFS injector set; and between the 50% combustor load and the 100% combustor load, injecting only air using the HE fuel nozzle set, the first AFS injector set, and the second AFS injector set. 
     
     
         8 . The method of  claim 6 , wherein, during a second co-fired mode, the method comprises:
 fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone in a combustor load range between the 50% and combustor load and the 100% combustor load.   
     
     
         9 . The method of  claim 8 , wherein between the 50% combustor load and the 100% combustor load, a gas fuel fraction of a total fuel amount is less than 20%. 
     
     
         10 . The method of  claim 8 , further comprising, between the 50% combustor load and the 100% combustor load, injecting only air using the HE fuel nozzle set and the first AFS injector set. 
     
     
         11 . The method of  claim 6 , wherein, during a third co-fired mode, the method comprises:
 fueling the HE fuel nozzle set to introduce and combust a gas fuel in the primary combustion zone in a combustor load range from the 50% combustor load up to the 100% combustor load; and   fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone in a combustor load range between the 50% combustor load and the 100% combustor load.   
     
     
         12 . The method of  claim 11 , wherein between the 50% combustor load and the 100% combustor load, a gas fuel fraction of a total fuel amount is between 20% and 50%. 
     
     
         13 . The method of  claim 11 , further comprising, between the 50% combustor load and the 100% combustor load, injecting only air using the first AFS injector set. 
     
     
         14 . The method of  claim 6 , wherein, during a fourth co-fired mode, the method comprises:
 fueling the HE fuel nozzle set to introduce and combust a gas fuel in the primary combustion zone between the 50% combustor load and the 100% combustor load;   fueling the first AFS injector set to introduce and combust the gas fuel in the secondary combustion zone between the 50% combustor load and the 100% combustor load; and   fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone between the 50% combustor load and the 100% combustor load.   
     
     
         15 . The method of  claim 14 , wherein between the 50% combustor load and the 100% combustor load, a gas fuel fraction of a total fuel amount is greater than 50%. 
     
     
         16 . A combustor for a turbomachine, the combustor comprising:
 a head end (HE) fuel nozzle set aimed into a combustion liner to combust fuel in a primary combustion zone;   a first axial fuel stage (AFS) injector set aimed into the combustion liner to combust fuel in a secondary combustion zone downstream of the primary combustion zone;   a second AFS injector set aimed into the combustion liner to combust fuel in a tertiary combustion zone downstream of the secondary combustion zone;   an ammonia atomizer aimed into the combustion liner to combust ammonia in at least the primary combustion zone; and   a controller configured to:
 sequentially supply a gas fuel to the HE fuel nozzle set, the first AFS injector set, and the second AFS injector set; and 
 supply ammonia as an ammonia fuel to the ammonia atomizer from a 20% combustor load up to a 100% combustor load. 
   
     
     
         17 . The combustor of  claim 16 , wherein the controller operates the combustor in a first co-fired mode of operation, which comprises the steps of:
 for a first combustor load range from a 0% combustor load up to a 50% combustor load, fueling the HE fuel nozzle set to introduce and combust the gas fuel in the primary combustion zone;   for a second combustor load range between a 10-20% combustor load range up to the 50% combustor load, fueling the first AFS injector set to introduce and combust the gas fuel in the secondary combustion zone;   for a third combustor load range between a 35% combustor load and the 50% combustor load, fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone; and   between the 50% combustor load and the 100% combustor load, discontinuing the supply of gas fuel to the HE fuel nozzle set, the first AFS injector set, and the second AFS injector set.   
     
     
         18 . The combustor of  claim 16 , wherein the controller operates the combustor in a second co-fired mode of operation, which comprises the steps of:
 for a first combustor load range from a 0% combustor load up to a 50% combustor load, fueling the HE fuel nozzle set to introduce and combust the gas fuel in the primary combustion zone;   for a second combustor load range between a 10-20% combustor load range up to the 50% combustor load, fueling the first AFS injector set to introduce and combust the gas fuel in the secondary combustion zone;   for a third combustor load range between a 35% combustor load and the 100% combustor load, fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone; and   between the 50% combustor load and the 100% combustor load, discontinuing the supply of the gas fuel to the HE fuel nozzle set and the first AFS injector set.   
     
     
         19 . The combustor of  claim 16 , wherein the controller operates the combustor in a third co-fired mode of operation, which comprises the steps of:
 for a first combustor load range from a 0% combustor load up to the 100% combustor load, fueling the HE fuel nozzle set to introduce and combust the gas fuel in the primary combustion zone;   for a second combustor load range between a 10-20% combustor load range up to the 50% combustor load, fueling the first AFS injector set to introduce and combust the gas fuel in the secondary combustion zone;   for a third combustor load range between a 35% combustor load and the 100% combustor load, fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone; and   between the 50% combustor load and the 100% combustor load, discontinuing the supply of the gas fuel to the first AFS injector set.   
     
     
         20 . The combustor of  claim 16 , wherein the controller operates the combustor in a fourth co-fired mode of operation, which comprises the steps of:
 for a first combustor load range from a 0% combustor load up to the 100% combustor load, fueling the HE fuel nozzle set to introduce and combust the gas fuel in the primary combustion zone;   for a second combustor load range between a 10-20% combustor load range up to the 100% combustor load, fueling the first AFS injector set to introduce and combust the gas fuel in the secondary combustion zone; and   for a third combustor load range between a 35% combustor load and the 100% combustor load, fueling the second AFS injector set to introduce and combust the gas fuel in the tertiary combustion zone.