Detonative cleaning apparatus nozzle
An apparatus directs gas from an upstream conduit through a vessel wall for cleaning surfaces within the vessel. A mounting flange couples the apparatus to the upstream conduit delivering the gas. The flange has first and second faces, an inboard surface bounding a central aperture, an outboard perimeter, and an array of bolt holes between the first and second faces. A conduit extends downstream from the flange and has inner and outer walls along at least a portion of a length and a space between the inner and outer walls for carrying a cooling fluid. The apparatus has a cooling fluid inlet and a cooling fluid outlet.
(1) Field of the Invention
The invention relates to industrial equipment. More particularly, the invention relates to the detonative cleaning of industrial equipment.
(2) Description of the Related Art
Surface fouling is a major problem in industrial equipment. Such equipment includes furnaces (coal, oil, waste, etc.), boilers, gasifiers, reactors, heat exchangers, and the like. Typically the equipment involves a vessel containing internal heat transfer surfaces that are subjected to fouling by accumulating particulate such as soot, ash, minerals and other products and byproducts of combustion, more integrated buildup such as slag and/or fouling, and the like. Such particulate build-up may progressively interfere with plant operation, reducing efficiency and throughput and potentially causing damage. Cleaning of the equipment is therefore highly desirable and is attended by a number of relevant considerations. Often direct access to the fouled surfaces is difficult. Additionally, to maintain revenue it is desirable to minimize industrial equipment downtime and related costs associated with cleaning. A variety of technologies have been proposed. By way of example, various technologies have been proposed in U.S. Pat. Nos. 5,494,004 and 6,438,191 and U.S. patent application publication 2002/0112638. Additional technology is disclosed in Huque, Z. Experimental Investigation of Slag Removal Using Pulse Detonation Wave Technique, DOE/HBCU/OMI Annual Symposium, Miami, Fla. Mar. 16-18, 1999. Particular blast wave techniques are described by Hanjalić and Smajević in their publications: Hanjalić, K. and Smajević, I., Further Experience Using Detonation Waves for Cleaning Boiler Heating Surfaces, International Journal of Energy Research Vol. 17, 583-595 (1993) and Hanjalić, K. and Smajević, I., Detonation-Wave Technique for On-load Deposit Removal from Surfaces Exposed to Fouling: Parts I and II, Journal of Engineering for Gas Turbines and Power, Transactions of the ASME, Vol. 1, 116 223-236, January 1994. Such systems are also discussed in Yugoslav patent publications P 1756/88 and P 1728/88. Such systems are often identified as “soot blowers” after an exemplary application for the technology.
Nevertheless, there remain opportunities for further improvement in the field.
SUMMARY OF THE INVENTIONOne aspect of the invention involves an apparatus for directing gas from an upstream conduit through a vessel wall for cleaning surfaces within the vessel. A mounting flange couples the apparatus to the upstream conduit delivering the gas and has first and second faces, an inboard surface bounding a central aperture, an outboard perimeter, and an array of bolt holes extending between the first and second faces. A conduit extends downstream from the flange and has inner and outer walls along at least a portion of a length. A space between the inner and outer walls carries a cooling fluid. There is a cooling fluid inlet and a cooling fluid outlet.
In various implementations, the space may extend from an upstream end outside the vessel wall at least partially downstream within the wall. The cooling fluid outlet may be along the conduit and the cooling fluid inlet may be along the flange. The inner and outer walls may each have a downstream rim. The cooling fluid outlet may be between the inner and outer walls. The inner wall may essentially be formed by a first tubular piece extending from an upstream rim to a downstream rim and having interior and exterior surfaces. Along an upstream portion, the interior surface may provide the flange inboard surface. The apparatus may be combined with the vessel. The vessel may be a furnace having a furnace wall separating a furnace exterior from a furnace interior and having a wall aperture. The combination may include a detonative source of the gas. The flange may be upstream of an exterior surface of the furnace wall. The conduit may extend through the furnace wall to protrude downstream of an interior surface of the furnace wall.
Another aspect of the invention involves a soot blower nozzle. Means mount the nozzle to an upstream soot blower gas conduit. A surface guides gas from the soot blower gas conduit into the interior of the vessel. Means cool the nozzle.
Another aspect of the invention involves a method for operating an apparatus for cleaning interior surfaces within a vessel having a vessel wall. A combustion pulse is caused in a combustion conduit. Combustion gases are directed along the combustion conduit through the vessel wall to be ejected from an outlet of the combustion conduit. A cooling gas is passed along a portion of the combustion conduit exposed to heat from the vessel.
In various implementations, the passing may be essentially continuous between a number of the combustion pulses. The passing may include passing the cooling fluid along a path at least partially surrounding a portion of the combustion gas flowpath. The passing may include passing the cooling fluid along a path into the vessel interior.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Like reference numbers and designations in the various drawings indicate like elements.
DETAILED DESCRIPTION
Each soot blower 22 includes an elongate combustion conduit 26 extending from an upstream distal end 28 away from the furnace wall 24 to a downstream proximal end 30 closely associated with the wall 24. Optionally, however, the end 30 may be well within the furnace. In operation of each soot blower, combustion of a fuel/oxidizer mixture within the conduit 26 is initiated proximate the upstream end (e.g., within an upstreammost 10% of a conduit length) to produce a detonation wave which is expelled from the downstream end as a shockwave along with associated combustion gases for cleaning surfaces within the interior volume of the furnace. Each soot blower may be associated with a fuel/oxidizer source 32. Such source or one or more components thereof may be shared amongst the various soot blowers. An exemplary source includes a liquified or compressed gaseous fuel cylinder 34 and an oxygen cylinder 36 in respective containment structures 38 and 40. In the exemplary embodiment, the oxidizer is a first oxidizer such as essentially pure oxygen. A second oxidizer may be in the form of shop air delivered from a central air source 42. In the exemplary embodiment, air is stored in an air accumulator 44. Fuel, expanded from that in the cylinder 34 is generally stored in a fuel accumulator 46. Each exemplary source 32 is coupled to the associated conduit 26 by appropriate plumbing below. Similarly, each soot blower includes a spark box 50 for initiating combustion of the fuel oxidizer mixture and which, along with the source 32, is controlled by a control and monitoring system (not shown).
Extending downstream from the upstream end 28 is a predetonator conduit section/segment 84 which also may be doubly flanged and has a length L3. The predetonator conduit segment 84 has a characteristic internal cross-sectional area (transverse to an axis/centerline 500 of the conduit) which is smaller than a characteristic internal cross-sectional area (e.g., mean, median, mode, or the like) of the downstream portion (60, 62) of the combustion conduit. In an exemplary embodiment involving circular sectioned conduit segments, the predetonator cross-sectional area is a characterized by a diameter of between 8 cm and 12 cm whereas the downstream portion is characterized by a diameter of between 20 cm and 40 cm. Accordingly, exemplary cross-sectional area ratios of the downstream portion to the predetonator segment are between 1:1 and 10:1, more narrowly, 2:1 and 10:1. An overall length L between ends 28 and 30 may be 1-15 m, more narrowly, 5-15 m. In the exemplary embodiment, a transition conduit segment 86 extends between the predetonator segment 84 and the upstreammost segment 60. The segment 86 has upstream and downstream flanges sized to mate with the respective flanges of the segments 84 and 60 has an interior surface which provides a smooth transition between the internal cross-sections thereof. The exemplary segment 86 has a length L4. An exemplary half angle of divergence of the interior surface of segment 86 is ≦12°, more narrowly 5-10°.
A fuel/oxidizer charge may be introduced to the detonation conduit interior in a variety of ways. There may be one or more distinct fuel/oxidizer mixtures. Such mixture(s) may be premixed external to the detonation conduit, or may be mixed at or subsequent to introduction to the conduit.
In the exemplary embodiment, the main fuel and oxidizer are introduced to the segment 86. In the illustrated embodiment, main fuel is carried by a number of main fuel conduits 112 and main oxidizer is carried by a number of main oxidizer conduits 110, each of which has terminal portions concentrically surrounding an associated one of the fuel conduits 112 so as to mix the main fuel and oxidizer at an associated inlet 114. In exemplary embodiments, the fuels are hydrocarbons. In particular exemplary embodiments, both fuels are the same, drawn from a single fuel source but mixed with distinct oxidizers: essentially pure oxygen for the predetonator mixture; and air for the main mixture. Exemplary fuels useful in such a situation are propane, MAPP gas, or mixtures thereof. Other fuels are possible, including ethylene and liquid fuels (e.g., diesel, kerosene, and jet aviation fuels). The oxidizers can include mixtures such as air/oxygen mixtures of appropriate ratios to achieve desired main and/or predetonator charge chemistries. Further, monopropellant fuels having molecularly combined fuel and oxidizer components may be options.
In operation, at the beginning of a use cycle, the combustion conduit is initially empty except for the presence of air (or other purge gas). The predetonator fuel and oxidizer are then introduced through the associated ports filling the segment 84 and extending partially into the segment 86 (e.g., to near the midpoint) and advantageously just beyond the main fuel/oxidizer ports. The predetonator fuel and oxidizer flows are then shut off. An exemplary volume filled the predetonator fuel and oxidizer is 1-40%, more narrowly 1-20%, of the combustion conduit volume. The main fuel and oxidizer are then introduced, to substantially fill some fraction (e.g., 20-100%) of the remaining volume of the combustor conduit. The main fuel and oxidizer flows are then shut off. The prior introduction of predetonator fuel and oxidizer past the main fuel/oxidizer ports largely eliminates the risk of the formation of an air or other non-combustible slug between the predetonator and main charges. Such a slug could prevent migration of the combustion front between the two charges.
With the charges introduced, the spark box is triggered to provide a spark discharge of the initiator igniting the predetonator charge. The predetonator charge being selected for very fast combustion chemistry, the initial deflagration quickly transitions to a detonation within the segment 84 and producing a detonation wave. Once such a detonation wave occurs, it is effective to pass through the main charge which might, otherwise, have sufficiently slow chemistry to not detonate within the conduit of its own accord. The wave passes longitudinally downstream and emerges from the downstream end 30 as a shockwave within the furnace interior, impinging upon the surfaces to be cleaned and thermally and mechanically shocking to typically at least loosen the contamination. The wave will be followed by the expulsion of pressurized combustion products from the detonation conduit, the expelled products emerging as a jet from the downstream end 30 and further completing the cleaning process (e.g., removing the loosened material). After or overlapping such venting of combustion products, a purge gas (e.g., air from the same source providing the main oxidizer and/or nitrogen) is introduced through the purge port 100 to drive the final combustion products out and leave the detonation conduit filled with purge gas ready to repeat the cycle (either immediately or at a subsequent regular interval or at a subsequent irregular interval (which may be manually or automatically determined by the control and monitoring system)). Optionally, a baseline flow of the purge gas may be maintained between charge/discharge cycles so as to prevent gas and particulate from the furnace interior from infiltrating upstream and to assist in cooling of the detonation conduit.
In various implementations, internal surface enhancements may substantially increase internal surface area beyond that provided by the nominally cylindrical and frustoconical segment interior surfaces. The enhancement may be effective to assist in the deflagration-to-detonation transition or in the maintenance of the detonation wave.
The apparatus may be used in a wide variety of applications. By way of example, just within a typical coal-fired furnace, the apparatus may be applied to: the pendants or secondary superheaters, the convective pass (primary superheaters and the economizer bundles); air preheaters; selective catalyst removers (SCR) scrubbers; the baghouse or electrostatic precipitator; economizer hoppers; ash or other heat/accumulations whether on heat transfer surfaces or elsewhere, and the like. Similar possibilities exist within other applications including oil-fired furnaces, black liquor recovery boilers, biomass boilers, waste reclamation burners (trash burners), and the like.
Further steps may be taken to isolate the combustion conduit (or major portion thereof) from chemical contamination and thermal stresses.
The exemplary air curtain flange 150 (
In operation, the gas flow may supplement or replace a baseline continuous purge gas flow. The proximity of the air curtain flange 150 to the outlet 30′ may provide improved resistance to the upstream reinfiltration of combustion gases discharged from the apparatus and infiltration of general furnace gases as well as particulate contamination. In addition to contamination from particulates generated within the furnace, the air curtain flow prevents accumulation of particulate reaction products from the combustion gases especially as such gases may cool and precipitate out particles or liquid condensate which may, in turn, accommodate particle formation or sludge formation. If operated in a baseline fashion, the continuous gas flow may also provide supplemental cooling of the conduit (especially downstream of the point of introduction).
Advantageously, means are provided for maintaining the circumferentially spaced-apart relationship between the tube 220 and sleeve 254. Exemplary means include one or more spacer elements. The spacer elements may be associated with means for measuring temperature parameters of the nozzle body largely defined by the tube and sleeve downstream of the flange.
In operation, the control and monitoring system uses the first thermocouple 294 to principally monitor the temperature of the nozzle assembly portion exposed to the furnace interior. The aforementioned additional thermocouple may be monitored as a back-up in the event of a failure of the first thermocouple when it is not desirable to immediately initiate a shutdown for repair. The same or different critical temperatures may be utilized in determining shutdown based upon the outputs of the two thermocouples.
Returning to
One or more embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the invention may be adapted for use with a variety of industrial equipment and with variety of soot blower technologies. Aspects of the existing equipment and technologies may influence aspects of any particular implementation. Other shapes of combustion conduit (e.g., non-straight sections to navigate external or internal obstacles) may be possible. Accordingly, other embodiments are within the scope of the following claims.
Claims
1. An apparatus for directing a gas from an upstream conduit through a vessel wall for cleaning surfaces within the vessel comprising:
- a mounting flange for coupling the apparatus to the upstream conduit delivering the gas and having: first and second faces; an inboard surface bounding a central aperture; an outboard perimeter; and an array of bolt holes between the first and second faces;
- a conduit extending downstream from the flange and having: inner and outer walls along at least a portion of a length; and a space between the inner and outer walls for carrying a cooling fluid;
- a cooling fluid inlet; and
- a cooling fluid outlet.
2. The apparatus of claim 1 wherein:
- the space extends from an upstream end outside the vessel wall at least partially downstream within the wall.
3. The apparatus of claim 1 wherein:
- the cooling fluid outlet is along the conduit; and
- the cooling fluid inlet is along the flange.
4. The apparatus of claim 3 wherein:
- the inner and outer walls each have a downstream rim; and
- the cooling fluid outlet is between the inner and outer walls.
5. The apparatus of claim 1 wherein:
- the inner wall is essentially formed by a first tubular piece extending from an upstream rim to a downstream rim and having interior and exterior surfaces, along an upstream portion, the interior surface providing the flange inboard surface.
6. The apparatus of claim 1 in combination with:
- said vessel, being a furnace, having a furnace wall separating a furnace exterior from a furnace interior and having a wall aperture; and
- a detonative source of said gas.
7. The combination of claim 6 wherein:
- the flange is upstream of an exterior surface of the furnace wall; and
- the conduit extends through the furnace wall to protrude downstream of an interior surface of the furnace wall.
8. A soot blower nozzle comprising:
- means for mounting the nozzle to an upstream soot blower gas conduit;
- a surface for guiding gas from the soot blower gas conduit into the interior of the vessel; and
- means for cooling the nozzle.
9. A method for operating an apparatus for cleaning interior surfaces within a vessel having a vessel wall, the method comprising:
- causing a combustion pulse in a combustion conduit;
- directing combustion gases along the combustion conduit through the vessel wall to be ejected from an outlet of the combustion conduit; and
- passing a cooling gas along a portion of the combustion conduit exposed to heat from the vessel.
10. The method of claim 9 wherein:
- said passing is essentially continuous between a plurality of said combustion pulses.
11. The method of claim 9 wherein:
- said passing comprises passing the cooling fluid along a path at least partially surrounding a portion of a combustion gas flowpath.
12. The method of claim 9 wherein:
- said passing comprises passing the cooling fluid along a path into the vessel interior.
Type: Application
Filed: Dec 11, 2003
Publication Date: Jun 16, 2005
Inventor: Donald Kendrick (Bellevue, WA)
Application Number: 10/733,717