Patent Publication Number: US-9851096-B2

Title: Steam generator film cooling using produced water

Description:
BACKGROUND 
     This disclosure relates generally to using produced water in a steam generator to film cool the steam generator. 
     Water separated from oil is often referred to as produced water. Other sources of produced water are possible. That is, produced water is not exclusively a byproduct of oil refining. Produced water is often characterized as untreated water having a high mineral content. 
     SUMMARY 
     A steam generator assembly according to an exemplary aspect of the present disclosure includes, among other things, a wall. Produced water acts as film cooling to at least a portion of the wall. 
     In a further non-limiting embodiment of the foregoing steam generator assembly, the produced water may be untreated water. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the produced water may be water that has been separated from oil. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the wall may provide a cylindrical combustion chamber. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the produced water may comprise a film of produced water extending across a surface of the wall. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the steam generator may vaporize the produced water to generate steam. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the produced water is introduced such that the produced water separates the portion of the wall from combustion products during operation of the steam generator. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the produced water and the combustion products may be held in a common chamber. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the produced water and the combustion products may be in direct contact. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the wall is configured such that the produced water film cooling the wall limits scale buildup on the wall. 
     A steam generator assembly according to another exemplary aspect of the present disclosure includes, among other things, a combustor wall providing at least a portion of a combustion chamber, and an inlet that delivers produced water to the combustion chamber. The produced water provides film cooling to the combustor wall. 
     In a further non-limiting embodiment of the foregoing steam generator assembly, a baffle may direct a flow of produced water along a surface of the combustor wall facing the combustion chamber. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the steam may be mixed with products of combustion. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, combustion within the combustion chamber vaporizes the produced water to form steam. 
     In a further non-limiting embodiment of any of the foregoing steam generator assemblies, the combustion chamber is configured such that the produced water film cooling the combustor wall limits scale adhering to the combustion wall. 
     A steam generator operating method according to another exemplary aspect of the present disclosure includes, among other things, introducing produced water into a combustion chamber of a steam generator, and film cooling a wall of the combustion chamber using the produced water. 
     In a further non-limiting embodiment of the foregoing steam generator operating method, the method may include limiting scaling buildup on the wall using the produced water. 
     In a further non-limiting embodiment of the foregoing steam generator operating method, the produced water is water that has been separated from oil. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
         FIG. 1  illustrates an example method for operating a steam generator. 
         FIG. 2  shows a cross-sectional view of an example steam generator assembly. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates an example method  20  for operating a steam generator. In this example, the method  20  generally includes steps  22  and  24 , although it is to be understood that each of the steps  22  and  24  may include any number of sub-steps in order to carry out or facilitate the primary steps  22  and  24 . In the example shown, step  22  includes the action of introducing produced water to a combustion chamber of a steam generator. The second step  24  includes the action of heating the produced water until the water is vaporized. The vaporized produced water exits from the combustion chamber as steam. 
     Produced water is generally considered water that has been separated from oil and not been treated. Produced water may have a higher hardness than treated water and may contain impurities. 
     The method  20  will be further described with reference to  FIG. 2 , which shows an example steam generator assembly  40  for carrying out the method  20 . It is to be understood that the disclosed steam generator  40  is only an example and that the steam generator  40  can be varied in accordance with the method  20 . 
     The example steam generator  40  is generally cylindrical and extends along an axis A from a first end  44  to an opposing, second end  48 . The steam generator  40  includes a combustor wall  52  having a surface facing inwardly toward the axis A. The combustor wall  52  provides a combustion chamber  56 . 
     In one non-limiting example, the steam generator  40  is from 7 to 21 feet (2.1-6.4 meters) long and about 4 inches (10.2 centimeters) in diameter. 
     An injector  60  at the first end  44  of the steam generator  40  delivers a mixture of fuel and oxidizer to the combustion chamber  56  near the axis A. An igniter  64  provides a flame that causes the mixture to combust. A combustion zone  68  schematically represents how the products of combustion propagate from the first end  44  toward the second end  48 . As shown, the products of combustion tend to fan radially outward when moving toward the second end  48 . 
     Water from a produced water supply  74  is delivered to the combustion chamber  56  through a plurality of inlets  72  established within the combustor wall  52 . In this example, the inlets  72  direct the water through the combustor wall  52  in a radial direction. The water then contacts a baffle  76 , which redirects the water to move in an axial direction along the combustor wall  52 . The inlets  72  are arranged circumferentially about the axis A. Water from the inlets  72  thus circumferentially surrounds the products of combustion when water moves through all the inlets  72 . 
     The products of combustion are very hot, especially near the first end  44  of the steam generator  40 . Notably, the products of combustion do not directly contact the combustor wall  52  in the area of the steam generator  40  due to the water from the inlets  72  separating the products of combustion from the combustor wall  52 . The water from the inlets  72  essentially insulates this portion of the combustor wall  52  from some of the thermal energy associated with the products of combustion. 
     More specifically, in this example, the water from the inlets  72  acts as film cooling to the combustor wall  52 . Film cooling the combustor wall  52  helps prevent scaling buildup on the combustor wall  52  from the evaporation of the water. Film cooling the combustor wall  52  limits or prevents scale from adhering and building up on the wall, which enables the steam generator  40  to utilize water from the produced water supply  74  rather than water that is not produced water. Instead of adhering to the combustor wall  52 , solids from the produced water are combusted or exit the steam generator  40  with the products of combustion and the steam. The solids exit as particulate matter. 
     Insulating the combustor wall  52  also prevents the combustor wall  52  from contacting the concentrated carbonaceous gases associated with the products of combustion near the first end  44 . 
     A liquid film cooling zone  78  generally represents the produced water that is providing film cooling. As the products of combustion and the water from the inlets  72  move toward the second end  48 , increasing amounts of the liquid water vaporize due to the thermal energy of the products of combustion. A vaporized film cooling zone  80  generally represents this vaporized water. 
     During operation, the products of combustion tend to expand radially outward. This tendency helps hold the liquid film cooling zone  78  and the vaporized film cooling zone  80  near the combustor wall  52 . 
     During operation, the products of combustion also move toward the second end  48 . This movement causes the liquid water in the liquid film cooling zone  78  and the vaporized water in the vaporized film cooling zone  80  to move toward the second end  48 . 
     As the products of combustion and the water from the inlets  72  move toward the second end  48 , the products of combustion and the water from the inlets  72  become mixed. A mixture zone  82  generally represents this mixture of the product of combustion and the vaporized water. The mixture is expelled from the steam generator  40  as steam. In another example, the mixture is condensed and used as clean (not produced) water. 
     The example steam generator  40  includes an array of nozzles  84  distributed circumferentially about the axis near the injector  60 . The array of nozzles  84  direct sprays of water radially outward toward the combustor wall  52 . 
     In this example, the nozzles  84  receive water from the produced water supply  74 . The nozzles  84  are arranged close enough to each other such that the sprays from circumferentially adjacent nozzles  84  overlap. This arrangement provides a sheet of water extending radially from the nozzles  84  toward the combustor wall  52 . The sheet of water limits thermal energy contacting an end wall  88  of the steam generator  40 , and other areas of the steam generator  40  near the first end  44 . 
     Features of the disclosed examples include directly, rather than indirectly, heating water in a steam generator combustor to produce steam. The water is produced water. The produced water film cools the combustor. 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.