DESCRIPTION OF PREFERRED EMBODIMENTS

[0030] The present invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments described in detail in the following description.

[0031] 1. System Overview

[0032] The present invention comprises a laser deslagging system for cleaning boilers, fireboxes, and slope areas having typical online temperatures between 1900-2500 degrees Fahrenheit. The inventive system is designed to be useful with a variety of boilers. For example, the boiler may be a conventional boiler made of heavy-duty steel plates such as those currently used in the power industry. A firebox and substrate tubes are contained inside the boiler and are generally constructed of steel or stainless steel. The boiler walls preferably have portals to allow for access into the inside of the boiler.

[0033] The laser main unit of the present invention may have many useful features. For example, the laser is preferably constructed to meet the temperature requirements of an online boiler. The laser should have enough power to be able to reach a depth of at least 25 feet into the firebox. This distance factor may be addressed by the following formula: Power=Distance×Optics or P ₁ =D ₁ ×O ₁ . The formula explains the amount of power needed compared to the distance of the target and the size of the optics. The access angles from the portals to the firebox and tubes may be about 30 degrees in order for optimal access to be achieved. The size and strength of the beam of the laser will also be affected by the particulates in the space between the laser and the slag material and is dependent upon how dense the particulates are in that space. Other important factors in determining laser power include: size of particulates in the space while online, tube thickness, types of materials used in constructing the boiler tubes, and the type of slag depending on the type of fuel burned (e.g. bituminous coal and its additives). Thus, the laser must be designed to effectively penetrate this space despite these variables and the possible deflection of the beam due to high angles of attack.

[0034] The laser main unit is preferably fixed in a vehicle or trailer so that it is mobile. The laser beam is then run through an optical cable from the main unit to get into range of the boiler's internal structures (e.g., boiler tubes) that are contained inside of the boiler. In this embodiment, the laser beam can be channeled through the cable any distance without significant degradation and is connected to a targeting system. Such a laser is also preferably man portable and easily moved around by a single individual as needed around and in the boiler.

[0035] 2. Detailed Description of Preferred Embodiments

[0036] The construction of lasers and boiler systems is well-known to those skilled in the art and therefore a detailed description thereof is not necessary to fully understand the present invention which is directed to novel improvements in the method of cleaning boilers.

[0037] Referring to FIG. 1 , the deslagging system of the present invention is preferably used with a conventional basic boiler 15 common in industry. Such a boiler 15 is typically fueled by coal or oil and which produce steam for driving the turbines of the plant is shown. The boiler includes a firebox 13 in which during times of operation intense heat is produced by the burning of coal or oil producing fireballs (not shown). The heat is transferred to the boiler tubes 12 . As a result of the burning of coal or oil, slag 111 ( FIG. 7 ) tends to build up on the boiler tubesl 2 reducing the efficiency of the operation of the boiler 15 . Observation portals or windows 15 a are present along the walls of the firebox that enable entry into the firebox 13 during the boiler 15 operation. A furnace drain 15 b or “monkey hole” exists at the bottom of the firebox 13 near ground-level to allow for drainage of slag deposits or other materials from the boiler 15 .

[0038] FIG. 2 shows the deslagging system of the present invention. The deslagging system is preferably housed in a mobile transport unit 22 which includes a tractor 23 that pulls a trailer 24 houses a laser unit 61 . Within trailer 24 is a control room 25 which may have air conditioning to cool the equipment and operator contained therein. The trailer may also have a laser generator area 26 . Although this particular embodiment describes the tractor/trailer mobile unit, it is also envisioned by the inventor that the invention could have a number of other means for mobility. Such alternative means include, but are not limited to a van, small cart, backpack etc.

[0039] Referring now to FIG. 3 , within the control room 25 is the computer control system 31 . An operator user interface consists of a conventional computer terminal 27 , including an input device such as keyboard 27 a , an output device such as a video monitor 27 b , processor 28 , memory 29 , and database 30 . A standard computer such as an IBM PC or MacIntosh will suffice. The memory preferably includes laser control and targeting as well as optical feedback software. When activated, the software functions as a laser control and optical feedback circuit for controlling and targeting the laser operating unit 61 . The computer system 31 includes a conventional bus 27 c interface in order to send and receive signals from the respective peripheral devices. In one preferred embodiment, the computer system has a 800+ GHz processor and 500+ MB of RAM. The computer system may also include a high-capacity hard drive and a separate cooling system.

[0040] Referring now to FIGS. 3, 4 , 5 , and 6 the computer control system 31 is preferably connected to a measuring system or automated targeting and imaging system 18 and the laser operating unit 61 . The targeting and imaging system 18 preferably consists of an optical targeting system or optical sensor 18 a for viewing the inside of the boiler 15 ( FIG. 1 ) and the boiler tubes 12 ( FIG. 1 ). In one preferred embodiment, the sensor includes a wide-angle video camera and a telephoto video camera connected in circuit with the computer bus 27 c . A conventional video digitizer connected between the camera and the computer bus 27 c converts the camera video signals into a digital form recognizable by the computer system 31 . Advantageously, the computer 31 selectively relays the signals representative of the respective camera's field of view to the computer monitor 27 b for viewing by a crew operator and thus provides real-time visual feedback to the operator in the trailer.

[0041] Referring now to FIG. 5 , connected to the computer bus 27 c and stored within the trailer 24 is the laser main unit or laser operating unit 61 (hereinafter simply just “laser”) for ablating the slag 111 ( FIG. 7 ) build-up within the boiler 15 . The laser 61 includes a power source or unit 66 connected to a laser generator 62 . Inside of the laser generator 62 is a flashlamp 63 , mixing chamber or pre-chamber 64 and pumping chamber or pump 65 . The laser 61 also has a cooling system or unit 68 that preferably includes a fan 69 . Also preferably operably integrated into the cooling unit 68 is a heat exchanger 70 containing water and glycol.

[0042] The laser 61 is preferably a conventional Q-switched laser which lases in the near infrared wavelength. The laser may also include a conventional laser switch circuit that connects with the computer via the bus and in response to signals therefrom, pulses the laser on and off. The lasing material preferably is a CO2 or a Neodymium (Nd) doped YAG crystal that is excited by pulses of light from flash lamp 63 . The YAG crystal is preferably very accurately positioned between two carefully aligned mirrors, with one mirror having transmissive as well as reflective properties, to create a resonant optical cavity or lasing chamber. The flash lamp 63 is used to store energy in the YAG crystal. The Q-switch is positioned within this cavity and connects in circuit to the laser switch circuit. The Q-switch operates under the control of the computer to produce very short, intense laser pulses by enhancing the storage and dumping of energy in and out, respectively, of the laser crystal. The Q-switch in response to signals from the computer via the laser switch circuit is operative to direct a laser pulse through the mirror having the transmissive properties. The laser pulse is preferably an ultra-short, pulsed laser. The laser 61 is preferably pulsed at a rate in which the upper surface layer of slag 111 ( FIG. 7 ) is ablated while minimally affecting the underlying substrate.

[0043] When operating while the boiler is on-line, one key feature of the laser is to have enough power to stay focused despite the extremely hot medium or amount or size of the particulates inside the boiler. Further, sufficient laser power is essential because the slag is more plastic and thus more difficult to remove when the boiler is on-line.

[0044] In one preferred embodiment, the laser preferably may be a CO ₂ pulse laser supplied by one of the following: Quantel, Big Sky, STI Optronics. The dimensions of the CO ₂ pulse laser may be about 30″ wide by 48″ long and about 48″ tall. The top of the laser unit is rounded like a cylinder and is modular in construction. This laser operating unit is preferably cooled with water, and/or by a fan. This laser operating unit uses CO ₂ as the catalyst for the laser diode and is rated to be at least 10 joules at 1.06 m.

[0045] In another preferred embodiment, the laser is a CFR series laser or a Laserblast series. Such a laser typically has a power source that is the size of a toaster and a cooling unit that is a heat exchanger with water and glycol mix. The laser may also include a precipitator.

[0046] In another preferred embodiment, the laser beam is preferably invisible to the naked eye and thus is not harmful to an operator's eyes and there is no need to wear protective goggles. In this embodiment, however, the laser beam will be visible on the carbon slag. Here, the beam is approximately 1½″ to 2″ in diameter.

[0047] In yet another embodiment, the laser is a chemical laser referred to as a Coil Laser System (CLS). The primary ingredients of this laser are hydrogen peroxide, sodium or potassium hydroxide and chlorine. The chemicals in the laser are mixed automatically by the CLS and then run through an iodine diode.

[0048] In still another embodiment the laser is a sapphire laser with up to 20 joules of power having dimensions of about 48″(w)×60″(1) and about 60″(d) and an aperture approx 4 inches in diameter and travels several kilometers.

[0049] The laser may also have a re-filtration unit that reconstitutes the integrity of the gas and in essence recycles the gas. The cycle rate of such a laser beam can range up to 100 Hz.

[0050] Referring now to FIGS. 5 and 6 , the control room 25 and the computer 27 is shown connected to the laser generator area containing laser unit 61 . In this embodiment, the unit 61 is connected to the computer controls and power couplings at a first end and connected to a targeting system or laser discharge device or gun 16 via a fiber optic cable 67 at a second end. The fiber optic cable 67 is preferably run from the laser 61 inside the trailer 24 into the boiler 15 where the gun 16 is positioned. The gun 16 discharges the laser raw beam 17 at the control of the computer 27 . The raw beam 17 ablates the slag 111 that has been built up in the boiler.

[0051] Referring now to FIG. 7 , another means of deployment is described. A fiber optic cable 107 is run from laser 101 inside trailer 124 . Next, a reflective ball 121 is suspended from the top of the boiler down inside between the boiler tubes which are in need of being cleaned. The laser 101 is first directed into boiler 115 where the ball 121 is positioned. The laser 101 may also include a conventional remote switch circuit 119 that connects with computer controller 127 via the bus and in response to signals therefrom activates portable targeting system 120 .

[0052] The targeting system 120 likely takes form of a remote camera located preferably on the ball 121 and a beam of visible light projected in parallel with the laser beam 117 so that the operator can see the effect that the laser beam is having on the slag on the tubes inside the boiler.

[0053] Next, laser beam 117 is directed at the reflective surface of the ball 121 . As the laser beam 117 hits one mirror on the ball 121 , the ball rotates and the reflected laser beam moves across the length of the tube. The laser ball 121 with its mirrored or reflective surface operates to move the laser beam across the tubes much like an old-fashioned typewriter moves the typed letters across the blank page.

[0054] As the beam moves across the tube, the system 120 focuses on the slag and pulses the laser on and off as needed. In this manner, ball 121 discharges laser beam 117 at various. Thus, the laser beam 117 is able to ablate the slag 111 that has been built up in the boiler in hard to reach places.

[0055] 3 . In Use and Operation

[0056] As shown in FIGS. 8 and 9 , when in use and operation the boiler deslagging process consists of transporting a deslagging system via preferably the tractor-trailer to the boiler location within a power plant facility (Step 130 ).

[0057] A 2-4 person crew would begin to set-up the deslagging system 5 (Step 132 ). The crew is preferably formed of at least one operator, a supervisor, and at least one control room person. The crew is preferably trained to be interchangeable with each other and intimately knowledgeable of the systems they are operating. It is also beneficial if the crew members have overlapping job duties so that efficiency and safety are maximized.

[0058] Initially, the crew would boot-up computer 31 in control room (Step 133 ) and begin warming up laser operating main unit (Step 134 ). The warming process includes mixing chemicals to power the laser. The crew would next lay-out the fiber optic cable needed to reach the boiler (Step 135 ). The fiber optics connect the gun or targeting system and the laser.

[0059] In one preferred embodiment ( FIG. 8 ), the boiler remains on-line will the cleaning of the tubes occurs. However, in alternative embodiment shown in FIG. 9 , the boiler is temporarily brought off line (Step 131 ) for safety reasons and to maximize cleaning effectiveness and thoroughness.

[0060] The crew would next ensure significant safety features on the system are fully engaged (Step 136 ) and take all necessary precautions to safeguard inadvertant triggering of the laser which could severely harm an operator, or damage the fiber optics, targeting system, mobile unit, or boiler. For example, it may be necessary to shield the operator's eyes from the laser with goggles or perhaps enshroud part of the boiler with light absorbent materials to ensure no extraneous laser light is accidentally emitted.

[0061] The gun or targeting and optical triggering system is then set-up (Step 137 ). Next, the operators manually or automatically relay the set-up and targeting or perimeter data to the control room (Step 139 ). Targeting information is then received from the control room and the system is ready to be activated. Once activated, the system 5 blasts the slag from the boiler's internal structures (Step 140 ).

[0062] The crew preferably operates the system to remove slag from internal structures within the boiler starting from the bottom of the boiler and working toward the top. By working the laser beam up the tubes within the boiler starting from the ground level of the boiler, the foundation of the built-up slag is removed and thus larger sections are likely to crumble, thus quickening the pace of the slag removal.

[0063] The laser cleaning process preferably produces a by-product of just ash and thereby greatly reduces the amount of dust created up and other waste products created. The ash is then removed from the boiler via the monkey drain 15 .

[0064] Once the platenization and other materials are removed from tubes the tubes are likely to be inspected by power plant personal (Step 141 ) to ensure no destruction such as grooving or pitting has occurred. Once the inspection is complete and everything is in order, the boiler may be brought completely back on-line ( FIG. 9 ) (Step 142 ).

[0065] Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the present invention is not limited thereto. It will be manifest that various additions, modifications and rearrangements of the features of the present invention may be made without deviating from the spirit and scope of the underlying inventive concept.

[0066] For example, the YAG laser could be could be enhanced by providing the relevant laser technology existing at the time. Similarly, although tractor/trailer configuration is described, any number of mechanisms to make the laser portable could be used in its place. In addition, the individual components need not be fabricated from the disclosed materials, but could be fabricated from virtually any suitable materials.

[0067] It is intended that the appended claims cover all such additions, modifications and rearrangements. Expedient embodiments of the present invention are differentiated by the appended dependent claims.