Advanced control system for enhanced operation of oscillating combustion in combustors

Abstract

Methods for optimizing emission levels from combustion operations, which include a system and process for optimizing levels of NOx and CO during fuel combustion including supplying flows of fuel (which is predetermined) and main oxidant to a burner. Oscillating combustion is generated by oscillating the fuel flow with an oscillating valve and combusting the oscillating fuel with the main oxidant adjacent the burner to produce combustion products. A post-combustion oxidant is injected into the combustion products where it is combusted with the combustion products. A controller is operatively associated with control units for controlling the main oxidant and post-combustion oxidant flow rates and the oscillating valve.

1 . A process for optimizing levels of NOx and CO during fuel combustion, said process comprising the steps of: 
 a) supplying a flow of a fuel to a burner;    b) supplying a flow of a main oxidant to a burner whose rate is controlled by a main oxidant flow rate control unit;    c) generating oscillating combustion by oscillating the fuel flow with an oscillating valve and combusting the oscillating fuel with the main oxidant adjacent the burner to produce combustion products;    d) injecting a post-combustion oxidant into the combustion products, a rate of the post-combustion oxidant injection being controlled by a post-combustion oxidant flow rate control unit;    e) combusting the combustion products and the injected post-combustion oxidant;    f) predetermining a rate of the fuel flow;    g) providing a controller operatively associated with the main oxidant flow rate control unit, the oscillating valve, and the post-combustion oxidant flow rate control unit;    h) determining a value or values associated with a combustion parameter selected from the group consisting of a rate of flow of the main oxidant, a rate of flow of the post-combustion oxidant, a frequency of the oscillating fuel flow, an amplitude of the oscillating fuel flow, a duty cycle of the oscillating fuel flow, and two or more combinations thereof; and    i) adjusting the combustion parameter associated with the determined value or values, wherein: 
 i) the determined value or values is based upon the predetermined fuel flow rate; and  
 ii) said determining step is performed by the controller.  
   
   
   
       2 . The process of  claim 1 , further comprising the step of measuring an oxygen concentration of the flue gas, wherein the determined value or values is based upon both the predetermined fuel flow rate and the measured oxygen concentration.  
   
   
       3 . The process of  claim 1 , wherein the combustion parameter is the flow rate of the main oxidant.  
   
   
       4 . The process of  claim 1 , wherein the combustion parameter is the flow rate of the post-combustion oxidant.  
   
   
       5 . The process of  claim 1 , wherein the combustion parameter is the oscillating frequency.  
   
   
       6 . The process of  claim 1 , wherein the combustion parameter is the oscillating amplitude.  
   
   
       7 . The process of  claim 1 , wherein the combustion parameter is the oscillating duty cycle.  
   
   
       8 . The process of  claim 1 , wherein said combusting step is performed in a boiler enclosing an oscillating combustion space where the oscillating combustion occurs and a post-combustion space where the combustion products and the post-combustion oxidant are combusted.  
   
   
       9 . The process of  claim 8 , further comprising the step of recirculating a portion of flue gas created from combustion of the combustion products and the post-combustion oxidant into one of the oscillating combustion space and the post-combustion space.  
   
   
       10 . The process of  claim 1 , wherein said combusting step is performed in an industrial boiler having a single burner, the boiler enclosing an oscillating combustion space where the oscillating combustion occurs and a post-combustion space where the combustion products and the post-combustion oxidant are combusted.  
   
   
       11 . The process of  claim 10 , wherein the combustion parameter is the flow rate of the post-combustion oxidant.  
   
   
       12 . The process of  claim 11 , wherein the fuel is natural gas.  
   
   
       13 . The process of  claim 12 , further comprising the step of predetermining the oscillating frequency, amplitude, and duty cycle.  
   
   
       14 . The process of  claim 1 , further comprising the step of: 
 a) before said steps of generating oscillating combustion, injecting a post-combustion oxidant, combusting the combustion products and the injected post-combustion oxidant, and adjusting the combustion parameter are performed, determining with the controller whether said steps of generating oscillating combustion, injecting a post-combustion oxidant, combusting the combustion products and the injected post-combustion oxidant, and adjusting the combustion parameter should be performed.    
   
   
       15 . The process of  claim 1 , further comprising the steps of determining with the controller, whether one or more of said steps of generating oscillating combustion, injecting a post-combustion oxidant, combusting the combustion products and the injected post-combustion oxidant, and adjusting the combustion parameter should be discontinued.  
   
   
       16 . A system for improved operation of a combustion process utilizing oscillating combustion, comprising: 
 a) a supply of fuel;    b) a supply of a main oxidant;    c) a supply of a post-combustion oxidant;    d) a burner for receiving said fuel and main oxidant and initiating combustion thereof to produce combustion products;    e) an oscillating valve operatively associated with said supply of fuel for achieving an oscillating flow of said fuel at said burner;    f) walls defining a combustion chamber operatively associated with said burner, and enclosing an oscillating combustion space, and a post-combustion space, said oscillating combustion space being upstream of said post-combustion space;    g) a main oxidant flow rate control unit operatively associated with said supply of main oxidant and said burner adapted and configured to control a flow rate of said main oxidant;    h) a post-combustion oxidant flow rate control unit operatively associated with said supply of post-combustion oxidant and said post-combustion space adapted and configured to control a flow rate of said post-combustion oxidant;    i) a post-combustion injection element operatively associated with said post-combustion oxidant flow rate control unit adapted and configured to inject said post-combustion oxidant into said post-combustion space to achieve combustion of the combustion products and said post-combustion oxidant; and    j) a controller operatively associated with said main oxidant flow rate control unit, post-combustion oxidant flow rate control unit, and oscillating valve.    
   
   
       17 . The system of  claim 16 , wherein said controller has an algorithm designed to determine a value or values associated with a combustion parameter selected from the group consisting of: 
 a) a rate of flow of the main oxidant;    b) a rate of flow of the post-combustion oxidant;    c) a frequency of the oscillating fuel flow;    d) an amplitude of the oscillating fuel;    e) a duty cycle of the oscillating flow; and    f) two or more combinations thereof, wherein the determined value or values is based upon a predetermined fuel flow rate.    
   
   
       18 . A process for optimizing levels of NOx and CO during fuel combustion in an industrial boiler, said process comprising the steps of: 
 a) providing flows of a fuel and a main oxidant to a burner;    b) generating oscillating combustion of the fuel and the main oxidant within a boiler to produce combustion products;    c) injecting a post-combustion oxidant into the combustion products;    d) combusting the combustion products and the post-combustion oxidant;    e) predetermining a rate of the fuel flow;    f) providing a controller adapted and configured to control a flow rate of the post-combustion oxidant;    g) determining a value associated with the flow rate of the post-combustion oxidant with a controller, the determined value being based upon the predetermined fuel flow rate; and    h) adjusting the flow rate of the post-combustion oxidant at the command of the controller using the determined value.