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| Pulse Detonation is the latest boiler-cleaning technology and will soon be specified as the product of choice to replace aging sootblowers throughout North America.
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Long sootblowers, wall blowers, water cannons and acoustic devices are the major technologies employed by boiler operators to combat ash accumulations. Pulse Detonation is the newest technology and is starting to be specified as the product to replace aging soot removal devices throughout North America. As independent research, tests and installations have shown, pulse detonation has proven itself in the various boiler regions as equally efficient, if not more efficient, than older technologies in controlling ash accumulations, limiting unplanned plant outages and increasing electrical productivity per ton of coal burned. |
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| Wall Blowers: |
| Wall blowers are used for cleaning the furnace wall. The wall blower is a short retractable lance that is extended slightly (1 to 2 inches, 2.5 to 5 cm) past the face of the water wall tubes when activated. The lance rotates about its axis while a nozzle at the tip directs the working fluid tangentially against the furnace wall. According to the Babcock & Wilcox Steam book, wall blowers clean an oval area roughly 12' high by 10' wide, around the insertion point. The cleaning area is reduced if the deposits are difficult to remove.
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| Long Sootblowers: |
| Long sootblowers are used to clean surfaces in the convective pass; i.e., tubes in the superheater, reheater and economizers. As with the wall blowers, long retractable sootblowers extend into the furnance when active and retract outside the boiler wall when idle. In operation, the retractable sootblower rotates as it is inserted and retracted out of the boiler. Two opposed nozzles direct the working fluid in a helical pattern as the sootblower advances and withdraws. The nozzles may be mounted perpendicular to the sootblower axis or canted to provide more dwell time. Generally, sootblowers are installed in pairs on opposite sides of the boiler, with each cleaning from wall to boiler centerline. The retractable sootblower is capable of cleaning in a radius of 4 to 9 feet (1.2 to 2.7 m) from centerline, depending on the difficulty of deposit removal and tube spacing.Long sootblowers and wall blowers may use steam, air, or water as the working fluid. The use of steam is the most common, as an economical choice, although this drains resources from producing electricity.Dry steam is generally used at 200 deg. F (93 deg. C) of superheat at a pressure of 200 to 250 psig (1.38 to 1.725 MPa). Steam has the advantage of providing twice the kinetic energy of air at the same pressure, but with the disadvantage of having the potential to introduce exessive moisture into the combustion gas. If steam sootblowers are installed outside, privisions for heating and drainage to prevent freezing must be made, adding additional maintenance hours.Air sootblowers are considered to be superior to steam sootblowers, mainly because a minimal amount of moisture is introduced into the combustion gas. As noted, air has less kinetic energy than steam at a given pressure. Air pressure is normally about 180 psig (1.240 MPa). The use of air sootblowers also requires the installation and/or use of plant compressors to provide the necessary air. This potentially drains plant resources and adds to the overall cost and maintenance requirements.Water is used as a medium for wall blowers, and almost never for long retractable sootblowers. The density of a water jet has the potential to provide very-high-impact energy and efficient cleaning, although there is great concern about tube damage and failure due to thermal shock (9). The amount of moisture introduced may also be of concern as it can alter the heat exchange rate and affect the bonding structure of ash.
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| Water Cannon: |
| The invention of the water cannon is a relatively recent development and is significantly different from conventional wall blowers. The water cannon directs a water jet across the furnace box, where it impinges on and removes slag from the opposite boiler wall. Operating water pressure is typically 175 PSI. The water cannon is mounted at an opening in the boiler wall that typically allows 90 degrees horizontal and 60-90 degrees vertical traverse, which allows single cannon coverage of a very large wall area. Cleaning is performed by sweeping the water jet across the boiler wall. Penetration of water into the outer slag layer and its expansion into steam is indicated as the primary mechanism of slag removal, although thermal shock may also play a role. The concern regarding thermal shock and its long-term effect on waterwall tubes is currently being evaluated.
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| Acoustic Horns: |
| Acoustic horns, sometimes referred to as sonic horns, have become widely utilized in the last 15 years. Their operating principle is to use relatively intense sound pressure to dislodge ash. The horns operate with a sound pressure on the order of 150 dB. Two ranges of operating frequency are used: above 75 Hz to avoid resonance with other plant components, and in the infrasonic or near infrasonic frequency range of 10 to 35 Hz. They are utilized in the economizer, air heater, electrostatic precipitator (ESP) and baghouse regions of a boiler. They have also been used for cleaning the Selective Catalytic Reduction (SCR) reactors, which are used for NOx control.The major advantages are their ability to reach areas that are inaccessible to traditional removal methods and their relatively low operating cost. Their major disadvantages are their inability to remove harder deposits and the potential for resonant vibration of boiler structure. Acoustic horns must be operated frequently; on the order of every 20-30 minutes to prevent loose ash accumulation.
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| Pulse Detonation: |
| Pulse detonation, also referred to as detonation wave technology, has been considered as an alternative to conventional cleaning methods. In operation, the device employs a detonation-initiated blast wave to break up and remove deposits from heat-exchanger surfaces. The pulse detonation cleaning technique is different from the action of an acoustic horn, because high frequency operation is not required for successful cleaning. The reported advantages of pulse detonation cleaning are the ability to remove harder deposits as well as loose slag and ash. Each pulse detonation combustor can clean a relatively large area and reach areas inaccessible to conventional steam sootblowers. Maintenance is reduced compared to traditional sootblowers. |
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 | Email us to learn more about our next generation ash removal product. |
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