Abstract:
A detonation combustor cleaning device includes at least one combustion chamber having combustion flow path and including a deflection member. An ignition device is operatively connected to the at least one combustion chamber is selectively activated to ignite a combustible fuel within the at least one combustion chamber to produce a shockwave that moves in a first direction along the combustion flow path, impacts the deflection member, reverses direction and passes into a vessel to dislodge particles clinging to inner surfaces thereof.

Description:
BACKGROUND 
     The present disclosure relates to the art of vessel cleaning devices and, more particularly, to a detonation combustor cleaning device for dislodging debris from inner surfaces of vessels. 
     Industrial boilers operate by using a heat source to create steam from water or another working fluid, which can then be used to drive a turbine in order to supply power. Conventionally, the heat source is a combustor that burns a fuel in order to generate heat, which is then transferred into the working fluid via a heat exchanger, such as a fluid conducting tube or pipe. Burning fuel may generate residues that often are left behind forming a buildup on surfaces of associated ducting or heat exchanger. This buildup can lead to performance degrades related to an increase in pressure drop, reduced fuel efficiency, and damage to mechanical components. These performance degrades can eventually lead to costly planned or unplanned outages. Periodic removal or prevention of such buildup maintains the operational efficiency of such boiler systems. In the past, the buildup was removed by directing pressurized steam, water jets, acoustic waves, and mechanical hammering onto the inner surfaces of the combustor or heat exchanger. However, such systems are often times costly to maintain and not always effective. That is, the effectiveness of such devices will vary depending on location and use. 
     More recently, detonative combustion devices are used to remove the buildup. Detonative combustion devices that burn customer friendly fuels, such as natural gas and propane, tend to require large detonation chamber diameters and lengths, which, in turn, require a relatively large installation footprint. Moreover, in some cases, such detonation devices require oxygen enrichment in order to create the detonations. Flexible fuels, or fuels having a large detonation cell size and high direct initiation energy, such as natural gas and propane, do not burn properly in existing systems without the addition of some amount of pre oxygen. More specifically, when using flexible fuels in existing detonative combustions devices, flame propagation velocity is less than desired, resulting in little or no cleaning ability o the resulting combustion process. 
     BRIEF DESCRIPTION 
     Exemplary embodiments of the invention include a detonation device cleaning system including a vessel having a main body including an outer surface and an inner surface that collectively define an interior chamber, a fuel source including a combustible fuel, an air source including an air flow, and a detonation combustor cleaning device mounted to the vessel and fluidly connected to the fuel source, the air source and the interior chamber. The detonation combustor cleaning device includes at least one combustion chamber that defines a combustion flow path, and a deflection member, an air inlet fluidly connected to the air source and the at least one combustion chamber, a fuel inlet fluidly connected to the fuel source and the at least one combustion chamber, and an ignition device operatively connected to the at least one combustion chamber and arranged downstream of the fuel inlet and the air inlet. The ignition device is selectively activated to ignite a combustible fuel within the at least one combustion chamber to produce a shockwave that moves in a first direction along the combustion flow path, impacts the deflection member, reverses direction and passes into the interior chamber to dislodge particles clinging to the inner surface of the vessel. 
     A second exemplary embodiment of the invention includes a detonation combustor cleaning device. The detonation combustor cleaning device includes at least one combustion chamber that defines a combustion flow path, and included a deflection member. An ignition device is operatively connected to the at least one combustion chamber. The ignition device is selectively activated to ignite a combustible fuel within the at least one combustion chamber to produce a shockwave that moves in a first direction along the combustion flow path, impacts the deflection member, reverses direction and passes into a vessel to dislodge particles clinging to inner surfaces thereof. 
     Exemplary embodiments of the invention also include a method of cleaning a vessel with a detonation cleaning device. The method includes receiving a flow of air into at least one combustion chamber having a combustion flow path through an air inlet receiving a flow of fuel into the at least one combustion chamber through a fuel inlet, the flow of fuel mixing with the flow of air to form a fuel/air mixture, periodically igniting the fuel/air mixture to form a shockwave, accelerating the shockwave along the combustion flow path, directing the shockwave into a deflection member provided on the at least one combustion chamber, reflecting the shockwave off the defection member back along the combustion flow path, directing the shockwave into a vessel having a surface to be cleaned, and loosening debris from the surface to be cleaned as a result of impacts from the shockwave. 
     Additional features and advantages are realized through the techniques of exemplary embodiments of the invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. For a better understanding of the invention with advantages and features thereof, refer to the description and to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top schematic view of an interior chamber of a vessel, shown in the form of an industrial boiler, having a detonation combustion cleaning device constructed in accordance with an exemplary embodiment of the invention; 
         FIG. 2  is a cross-sectional schematic view of the detonation combustion cleaning device of  FIG. 2 ; and 
         FIG. 3  is a cross-sectional schematic view of a detonation combustion cleaning device in accordance with another exemplary embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Soot, ash, or other buildup on inner surfaces of industrial boilers or other vessels can cause efficiency losses. Examples of such efficiency losses include reduced heat transfer capability, reduced gas flow capability and reduced process “online” time. In the case of industrial boilers, the efficiency losses are often evidenced by an increase in exhaust gas temperature measured at a backend of a heat exchange process, as well as an increase in a fuel-burn rate necessary to maintain steam production and energy output. Traditionally, completely removing buildup from such fouled surfaces requires that the boiler be shut down during cleaning. Some online cleaning methods are able to extend boiler operation without localized cleaning. Cleaning while the boiler remains online generally leads to high maintenance costs, high operation costs and/or incomplete cleaning results. 
     In the systems and techniques according to exemplary embodiments of the invention, a combustion chamber or detonation combustor external to the boiler is used to generate a series of detonations or quasi-detonations that are directed into a portion of the boiler having accumulated build-up. High speed shock or sound waves having high pressure fluctuations travel through the portion of the boiler and loosen buildup from the surface. The buildup is carried away from the surfaces by gravity and/or gas flow, to a bottom portion of the boiler. The buildup is then removed from the boiler through hoppers, stacks or otherwise removed from the gas stream through environments control devices such as bag houses or electronic precipitators. As will be discussed below, the use of repeated detonations has advantages over traditional cleaning techniques, such as steam/air soot blowers or purely acoustic soot removal devices. 
     It is also desirable that a cleaning system for a boiler be able to operate to quickly remove buildups in order to minimize down-time for the boiler. In addition, it is desirable that the system be conveniently operable within a boiler environment, i.e. that it is able to physically fit within space restrictions necessary, able to reach portions of the boiler that require de-fouling, and that the detonation chamber does not interfere with boiler operation when the cleaning system is not in use. It is also desirable that the installation of such a cleaner not take up excessive floor space outside the boiler or require major modifications to the boiler for access. It is also desirable that the cleaning system be able to operate using a broad range of fuel types. A detonation combustor based cleaning system that can provide these and other features will be described in more detail below. 
     As used herein, the term “pulse detonation combustor” (PDC) will refer to a device or system that produces both a pressure rise and velocity increase from the detonation or quasi-detonation of a fuel and an oxidizer, and that can be operated in a repeating mode to produce multiple detonations or quasi-detonations within the device. A “detonation” is a supersonic combustion in which a shock wave is coupled to a combustion zone, and the shock is sustained by the energy release from the combustion zone, resulting in combustion products at a higher pressure than the combustion reactants. For simplicity, the term “detonation” as used herein will be meant to include both detonations and quasi-detonations. A “quasi-detonation” is a supersonic turbulent combustion process that produces a pressure rise and velocity increase higher than a pressure rise and velocity increase produced by a sub-sonic deflagration wave. 
     Exemplary PDCs, some of which will be discussed in further detail below, include an ignition device for igniting combustion of a fuel/oxidizer mixture, and a detonation chamber in which pressure wave fronts initiated by the combustion coalesce to produce a detonation wave. Each detonation or quasi-detonation is initiated either by an external ignition source, such as a spark discharge, laser pulse, heat source, or plasma igniter, or by gas dynamic processes such as shock focusing, auto ignition or an existing detonation wave from another source (cross-fire ignition). The detonation chamber geometry allows the pressure increase behind the detonation wave to drive the detonation wave and also to blow the combustion products themselves out an exhaust of the PDC. 
     Various chamber geometries can support detonation formation, including round chambers, tubes, resonating cavities and annular chambers. Such chambers may be of constant or varying cross-section, both in area and shape. Exemplary chambers include cylindrical tubes and tubes having polygonal cross-sections, such as, for example, hexagonal tubes. As used herein, “downstream” refers to a direction of flow of at least one of fuel and/or oxidizer. 
     With initial reference to  FIG. 1 , a detonation device cleaning system  1  includes a vessel, shown in the form of an industrial, an industrial boiler is indicated generally at  2 . Vessel  2  includes a main body  4  having an outer surface  6  and an inner surface  7  that defines an interior chamber  8 . In the embodiment shown, vessel  2  includes a flange  10  that is provided on main body  4 . Cleaning system  1  also includes a detonation combustor cleaning device  20  operatively connected to flange  10  and, as will become more fully evident below, an air source  23  and a fuel source  24 . Detonation combustion cleaner  20  is selectively operated to direct a shockwave  26  onto inner surface  7  to loosen any build-up of debris. 
     As best shown in  FIG. 2 , detonation combustor cleaning device  20  includes a main or first combustion chamber  31  and an initiator tube or second combustion chamber  32 . First combustion chamber  31  includes a first or substantially linear combustion portion  34  that extends to a second or arcuate combustion portion  36 . Substantially linear combustion portion  34  includes a substantially linear main body portion  39  having a first end portion  41  that extends to a second end portion  42  through an intermediate portion  43 . First end portion  41  is provided with a flange  45 . Similarly, second end portion  42  is provided with a flange  46 . Arcuate combustion portion  36  includes an arcuate main body portion  52  having a first end portion  54  that extends to a second end portion  55  through an arcuate intermediate portion  56 . First end portion  54  is provided with a flange  60  that is connected to flange  10  on vessel  2  while second end portion  55  is provided with a flange  61  that is connected to flange  45 , joining arcuate portion  36  to substantially linear portion  34 . In this manner, linear combustion portion  34  and arcuate combustion portion  36  combine to define a first combustion flow path  63 . 
     In addition, first combustion chamber  31  includes a connector portion  65  having a first end  66  that extends to a second end  67  that is provided with a flange  69 . Flange  69 , in a manner that will be described more fully below, serves as a connection point for second combustion chamber  32 . First combustion chamber  31  is further shown to include a deflection member  72  having a deflection surface  75 . In the exemplary embodiment shown, deflection surface  75  is curvilinear or concave in shape. 
     Further shown in  FIG. 2 , second combustion chamber  32  includes a first or substantially linear combustion section  84  that extends to a second or curvilinear combustion section  86  that leads to a second substantially linear combustion section  88  before terminating in a third substantially linear combustion section  89 . First combustion section  84  includes a main body section  91  having a first end section  92  that extends to a second end section  93  through an intermediate section  94 . Second end section  93  is provided with a flange  96 . Curvilinear combustion section  86  includes a curvilinear main body section  100  having a first end section  101  that extends to a second end section  102  through a curvilinear intermediate section  103 . First end section  101  is provided with a flange  105  that is joined to flange  96 , while second end section  102  is provided with a flange  106 . In a manner similar to that described above, second substantially linear combustion section  88  includes a main body section  110  having a first end section  111  that extends to a second end section  112  through an intermediate section  113 . First end section  111  is provided with a flange  115  that joins with flange  106  to connect second substantially linear combustion section  88  to curvilinear combustion section  86 . In addition to flange  115  on first end section  111 , second end section  112  is provided with a flange  116 . 
     In a manner also similar to that described above, third substantially linear combustion section  89  includes a main body section  121  having a first end section  122  that extends to a second end section  123  through an intermediate section  124 . First end section  122  is provided with a flange  127  that joins to flange  116  interconnecting second linear combustion section  88  and third linear combustion section  89 . Actually, flange  127  is sandwiched between flange  69  provided on connector portion  65  and flange  116 . First substantially linear combustion section  84  combines with curvilinear combustion section  86 , second substantially linear combustion section  88  and third substantially linear combustion section  89  to form a second combustion flow path  130 . 
     Second combustion chamber  32  is shown to include an air inlet  140  positioned at first end section  92  of first substantially linear combustion section  84 . Air inlet  140  is connected to air source  23  via a conduit  141 . A fuel inlet  144  is arranged approximate to air inlet  140 . Fuel inlet  144  is fluidly connected to fuel source  24  via a conduit  145 . In addition, second combustion chamber  32  is provided an ignition device or an igniter  150  that is arranged downstream of air inlet  140  and fuel inlet  144 . Igniter  150  is operatively connected to a controller (not shown) via a lead  154 . 
     Although not illustrated, such a controller may be used as is generally known in the art to control the timing and operation of various systems, such as the fuel valve and ignition source. As used herein, the term controller is not limited to just those integrated circuits generally referred to in the art as a controller, but broadly refers to a processor, a microprocessor, a microcontroller, a programmable logic controller, an application specific integrated circuit, and other programmable circuits suitable for such purposes. 
     In further accordance with the exemplary embodiment shown, second combustion chamber  32  is provided with a plurality of obstacles  160  arranged with a first substantially linear combustion section  84 . Obstacles  160  are shown in the form of a plurality cylindrical protrusions, one of which is indicated at  162 . In addition, a second plurality of obstacles  165  is provided within second substantially linear portion  88  and third substantially linear portion  89 . Obstacles  160  and  165  are disposed at various locations along first substantially linear combustion portion  84  and second and third substantially linear combustion portions  88  and  89  respectively. That is, obstacles  160  and  165  are arranged at regular intervals with an angular off-set between adjacent obstacles. Obstacles  160  and  165  serve to accelerate a combustion front or shock wave, associated with the flame front, into a detonation or quasi-detonation prior to reaching second end section  123 . Obstacles  160  and  165  are thermally integrated onto an internal wall portion (not separately labeled) of second combustion chamber  32 . Such thermally integrated obstacles may be created in various ways. For example, obstacles may include features that are machined into the wall, formed integrally with the wall, by casting or forging, by (for example) or attached to the wall, for example, by welding. In general, a thermally integrated obstacle or other thermally integrated feature in sufficient contact with an internal wall portion of second combustion chamber  32  such that obstacles  160  and  165  exchange heat effectively with second combustion chamber  32 . 
     Although described as cylindrical protrusions, it should be understood that obstacles  160  and  165  may take on a variety of forms such as, annular rings, partial protrusions, and the like. In addition, rather than being spaced equally as shown in  FIG. 2 , obstacles  160  and  165  may be placed with varying distances between adjacent obstacles. In any case, in the exemplary embodiment shown, obstacles  160  and  165  are formed having a width that is between about one-quarter and one-half of an inner diameter of second combustion chamber  32 . A length of each of the plurality of obstacles  160  and  165  is about 1½ of an inner diameter of second combustion chamber  32  or greater. 
     Having described an overall structure of detonation combustion cleaning device  20 , the general operation of detonation cleaning device  20  will be discussed with referenced to  FIG. 2 . In the section that follows, a single occurrence of a fuel fill phase, a combustion ignition, an acceleration of a flame front to detonation and a blow down and purge of combustion products will be referred to as a combustion cycle or detonation cycle. A portion of time that the cleaner system is active is referred to as a “cleaner operation”. Time when vessel  2  is being actively used for its purpose will be referred to as “boiler operation”. As noted above, vessel  2  need not be part of a boiler. However, for simplicity of reference the term “boiler operation” will be used to refer to the operation of any device being cleaned by detonation combustion device  20 . 
     In particular, and as will be discussed more fully below, one advantage of detonation combustion cleaning device  20  described herein is that, unlike other detonation cleaning systems, there is no need to shut down the vessel or other device during cleaning. Specifically, it is possible for detonation combustion cleaning device  20  to operate during boiler operation. Detonation combustion cleaning device  20  need not be running continuously during boiler operation; however, by providing the flexibility to operate detonation combustion cleaning device  20  on a regular cycle during boiler operation an overall higher level of cleanliness can be maintained without significant down-time in boiler operation. 
     In the fill phase of the detonation cycle, air and fuel are introduced into second combustion chamber  32  via air inlet  140  and fuel inlet  145 . The air and fuel pass into second combustion chamber  32  and mix to form a fuel/air mixture suitable for combustion within detonation combustion cleaning device  20 . As more fuel and air are introduced and mixed, second combustion chamber  32  fills with the fuel/air mixture, flowing along the second combustion flow path  130  toward first combustion chamber  31 . Air can be fed continuously into second combustion chamber  32  through air inlet  140  during cleaning operation. However, it may be desirable to use a valve to control reintroduction into second combustion chamber  32  by means of a controller in some embodiments. In addition, the ability to control airflow for times when detonation and combustion cleaning device  20  is not operating may also be desirable. In one exemplary embodiment, a controller (not shown) tracks an amount of time that fuel inlet  144  is open and, based upon a rate of air input to second combustion chamber  32 , operate to close fuel inlet  144  once a sufficient amount of fuel has been added such that the fuel air mixture has filled a desired portion of combustion chambers  31  and  32 . 
     Once a sufficient amount of air fuel mixture has been introduced, ignition device  150  is triggered by the controller in order to initiate combustion of the fuel air mixture within second combustion chamber  32 . If, for example, a spark initiator is used as ignition device  150 , the controller can send an electrical current to the initiator in order to create a spark at the appropriate time. In general, the ignition device introduces sufficient energy into the fuel air mixture to form a flame front within second combustion chamber  32 . As the flame front consumes the fuel by burning along with any oxidizers present within the mixture, the flame front will propagate along the second combustion flow path  130  toward first combustion chamber  31 . 
     As the flame front propagates along second combustion flow path  130 , the flame front will reach a plurality of obstacles  160 . At this point, an interaction with the flame front with inner walls of second combustion chamber  32  and plurality of obstacles  160  will generate an increase in pressure and temperature within second combustion chamber  32 . Such increased pressure and temperature tend to increase a speed at which the flame front propagates through second combustion chamber  32  and a rate at which energy is released from the fuel/air mixture by combustion at the flame front. This acceleration continues until the combustion speed rises above that expected from an ordinary deflagration process to a speed that characterizes a quasi-detonation or detonation. This detonation process takes place rapidly (in order to sustain a high cyclic rate of operation), so that obstacles  160  and  165  are used to decrease the run-up time and distance that is required for each initiated flame to transition into a detonation. 
     The flame front travels along first substantially linear portion  84  though curvilinear portion  86  into second substantially linear portion  88  and third substantially linear portion  89  encountering obstacles throughout obstacles  165 . The flame front continues to accelerate along second and third substantially linear combustion portions  88  and  89  before exiting second end section  123 . At this point, the flame front encounters deflection in surface  72  and is deflected back along first combustion chamber  31 . The flame front continues to pass along first combustion flow path  63 , through arcuate portion  36  and into vessel  2 . The flame front and shock wave  27  associated therewith impact upon inner surfaces  7  of vessel  2  loosening any debris adhered thereon. 
     By guiding the flame front into deflection surface  72 , combustion is bolstered and effectively transferred from a smaller diameter chamber, e.g. second combustion chamber  32 , into a larger diameter chamber, e.g., first combustion chamber  31  thereby allowing the use of flexible fuels. That is, fuels having an associated large detonation cell size and high initiation energy. Thus, creating and/or maintaining a flame front with detonative or quasi-detonative speeds and associated shock wave along multiple combustion flow paths into a vessel is often times difficult. However, it has been found that by deflecting the flame front in such a manner sustains combustion and, by extension, the flame front and associated shock wave. Thus, the present invention enables the use of various flexible fuels heretofore not practical in use in existing detonation combustion cleaning systems, and is able to utilize such fuels in a much more compact cleaner geometry that presently available. 
     Reference will now be made to  FIG. 3  in describing a detonation combustion cleaning device  200  constructed in accordance with another exemplary embodiment of the invention. As shown, detonation combustion cleaning device  200  includes a main or first combustion chamber  204  having a main body portion  206  including a first end portion  207  that extends to a second end portion  208  through a substantially linear intermediate portion  209 . In a manner similar to that described above, main body portion  206  defines a first combustion flow path  211 . In a manner also similar to that described above, first end portion  207  is provided with a flange  212  that is configured to couple with flange  10  on vessel  2  while second end portion  208  is provided with a flange  213 . Flange  213  is coupled to a deflection member  218  having a deflection surface  221 . Unlike the curvilinear deflection surface  72  described above, deflection surface  221  is substantially planar or linear. 
     Detonation and combustion cleaning device  200  also includes an initiator tube or second combustion chamber  230  having a first combustion section  232  that extends to a second combustion section  233  that define a second combustion flow path  235 . As shown, first combustion section  232  includes a main body section  236  having a first end section  237  that extends to a second end section  238  through an intermediate section  239 . Second end section  238  is provided with a flange  242  which, as will be described more fully below, joins first combustion section  232  to second combustion section  233 . Towards that end, second combustion section  233  includes a main body section  244  having a first end section  245  that extends to a first intermediate or curvilinear or angled section  246  that passes to a second intermediate or substantially linear portion  247  before terminating in a second end section  248 . First end section  245  is provided with a flange  250  that engages with flange  242  on first combustion section  232 . 
     Second combustion chamber  230  includes an air inlet  260  provided at first end section  237  of first section  232 . Air inlet  260  is configured to be fluidly connected to air source  23  via a conduit  261 . A fuel inlet  264  is arranged adjacent to air inlet  260 . Fuel inlet  264  is configured to be fluidly connected to fuel source  24  via a conduit  265 . An igniter  270  is arranged downstream from air inlet  260  and fuel inlet  264 . Igniter  270  is connected to a controller (not shown) through an igniter lead  271 . In a manner similar to that described above, first combustion section  232  includes a first plurality of obstacles  280 . Obstacles  280  serve to accelerate a flame front passing through second combustion chamber  230  along second combustion flow path  235 . A second plurality of obstacles  285  are formed within second combustion section  233  and serve to further accelerate the flame front passing along second combustion flow path  235 . Each of the plurality of obstacles  280 ,  285  are represented by cylindrical protrusions, one of which is indicated at  290 , that extend off an inner wall portion (not separately labeled) of second combustion chamber  230 . 
     As described above, igniter  270  initiates combustion of a fuel/air mixture present within second combustion chamber  230  creating a flame front having an associated shock wave. The flame front moves along second combustion flow path  235  before exiting second end of section  248  of second section  233 . Upon exiting second section  233  the flame front impact deflection surface  221  is reflected back along first combustion flow path  215 . The flame front and associated shock wave move along first combustion flow path  215  through first end portion  207  and exit into vessel  2  impacting upon inner surfaces to loosen debris there from. As noted above, by deflecting the flame front and associated shock wave, from a smaller combustion chamber to a larger combustion chamber, detonation combustion cleaning device  200  is configured to burn flexible fuels/mixtures such fuels containing methane/natural gas, propane, ethylene, hydrogen, acetylene, and many other gaseous or vaporize fuels. In essence, detonation combustion cleaning device  20  is configured to detonate fuels/mixtures having a large detonation cell and that require large detonation initiation energy without oxygen enrichment or the fuel/air mixture. 
     In general, this written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of exemplary embodiments of the present invention if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.