(1) Field of the Invention
The invention relates to industrial equipment. More particularly, the invention relates to the 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.
One aspect of the invention is directed to an apparatus for providing detonative cleaning communication through a vessel wall. A first conduit extends from the vessel wall. A first valve has an open condition permitting communication through the first conduit and a closed condition. A second conduit has an insertion portion dimensioned to be received within a receiving portion of the first conduit. A second valve has an open condition permitting communication through the second conduit and a closed condition.
In various implementations, one valve may be a sliding gate valve and the other valve may be a sliding gate valve or a hinged gate valve. One of the valves may be manually-actuated or machine-actuated and the other may manually-actuated or machine-actuated. There may be means for sealing the first conduit relative to the second conduit over a first range of insertion of the second conduit within the first conduit. The second conduit may have an interior surface off-axis to an exterior surface.
Another aspect of the invention involves an apparatus for providing detonative cleaning communication through a vessel wall. A conduit defines a flow path through the vessel wall. A valve along the flow path has an open condition and a closed condition.
In various implementations, a source of fuel and oxidizer may be coupled to the conduit. Means may ignite charges of the fuel and the oxidizer. The valve may be secured relative to the wall. The valve may be along a downstream half of the flow path. The valve may be a first valve at an upstream end of an access conduit. The apparatus may include a second valve along the conduit upstream of the first valve and upstream of an insertion portion of the conduit within the access conduit. The valve may be a first valve between a main portion of the conduit and a downstream insertion portion of the conduit. The apparatus may include a second valve at an upstream end of an access conduit receiving the insertion portion.
Another aspect of the invention involves a method for cleaning a surface within a vessel. The vessel has a wall and an access conduit initially sealed by a first valve. An insertion portion of a combustion conduit is inserted into the access conduit. The combustion conduit has a second valve. A seal is formed between the access conduit and the combustion conduit. The first valve is opened. The second valve is opened. Combustion gases are passed through the combustion conduit into the vessel. The insertion portion is withdrawn from the access conduit.
In various implementations, the first valve may be opened during an intermediate stage of the insertion. A seal may be formed between the combustion conduit and the access conduit. The seal may be formed before the opening of the first valve. The opening one valve may comprise a pivotal movement of a gate of that valve. The opening of the other valve may be manual.
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.
Like reference numbers and designations in the various drawings indicate like elements.
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 shock wave 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 shock wave 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.
Various equipment operate under substantial differential pressure. For example, a positive pressure furnace will have interior pressures above ambient exterior pressures. This pressure difference imposes constraints on the ability to connect and disconnect soot blower components from the furnace while the furnace is in operation. Accordingly, a valve system may be provided for coupling soot blower equipment to the furnace.
In the exemplary embodiment, the insertion conduit has an upstream flange mounted to a downstream surface 174 of a body 176 of a second valve 178. The upstream surface 180 of the second valve body is mounted to a downstream main conduit section or segment of a soot blower combustion conduit (e.g., to the downstreammost segment 60 of
In a hot install operation, with the furnace operating and the first and second valves closed, the insertion conduit (preferably as a unit with the rest of the combustion conduit) may be brought into alignment with the access conduit and inserted, a distal portion adjacent its downstream end 182 passing through the seal and sealing therewith. Depending on the particular implementation, further translation of the insertion may be unnecessary. In that case, the valves may be opened to permit soot blasting. To remove the insertion conduit, the valves may be closed and the insertion conduit withdrawn from the seal assembly. In other implementations, however, after the initial sealing insertion, the first valve may be opened with the second valve closed and the insertion conduit further inserted so as to pass through the first valve and optionally into the spacer conduit.
Although illustrated heretofore with coaxial interior and exterior surfaces, the insertion conduit may have other arrangements (e.g., for directing the soot blower output in a desired direction). For example,
In an exemplary sequence of assembly, the access valve 302 has been preinstalled to the vessel (e.g., when the vessel is built or during a shutdown thereof). Remaining assembly steps may be performed hot (e.g., with the vessel in operation). The access valve is initially in its closed condition. One or more threaded studs 330 (
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 cleaning technologies. Aspects of the existing equipment and technologies may influence aspects of any particular implementation. Accordingly, other embodiments are within the scope of the following claims.