Traditional Soot Blowers
Electric power generation plants usually have dozens of soot blowers in operation. Until recently there were limited choices on how to regulate and effectively clean boilers, with the most common technologies being steam and compressed air soot blowers.
These were the most well-known traditional soot blowers to combat fouling accumulations:
1. Steam soot blowers
2. Air soot blowers
3. Water cannons soot blowers
4. Acoustic (sonic) horn soot blowers
Steam Soot Blowers.
A common application at oil, coal, or multi-fuel source power plants is retractable or rotary steam soot blowers. Several steam soot blowers are usually found at each level of the boiler tower. A traveling lance with nozzle jets penetrates narrow openings in the boiler tube banks to blast the tubes clean.
The primary elements of the typical steam soot blower:
1. A means to convey the nozzle-conveying mechanism, including the lance tube, carriage, and drive motor.
2. A means to supply the blowing medium into the nozzle-poppet valve, feed tube, packing gland, and lance tube.
3. A means to support and contain the lower component, which is a canopy-type beam with a two-point suspension.
4. Integral components protected by the beam control the blowing cycle and supply power to the drive motor.
Typical soot blower operation begins with the blower in the retracted position. At startup, the carriage moves along guide rails or rollers located on each side of a beam to insert the lance tube into the boiler. The carriage then begins the cleaning cycle. The carriage continues to move and the lance tube rotates through the boiler tube banks. At the furthermost point, the carriage reverses its direction and the lance tube starts to return on a different nozzle path. The carriage continues to retract until the nozzle reaches the boiler wall, at which point the blower shuts off. The carriage continues to the start position.
From this brief description we can understand why these very complicated mechanical devices are so expensive.
Steam potentially introduces excessive moisture and condensation in the boiler, with accompanying damage to the pipes, supports, and refractories (thermos shock phenomena). If steam soot blowers are installed outside, provisions for heating and drainage to prevent thermos shocks must be made, thereby adding maintenance hours.
1. High capital, operational, and maintenance costs.
2. Damages pipes, boiler structure, and refractories inside the boiler.
3. Huge devices make it impossible to install them in all the desired places.
4. Large service platforms are required.
5. Low cleaning effectiveness.
6. Hundreds of spare parts must continuously be kept in stock.
7. The steam supply costs five to ten dollars per cleaning cycle.
Steam soot blower regular maintenance and operation requirements require regular inspection and replacement of parts: :
|1. Blown and damaged Nozzles
2. Worm and Damaged Carriage Housing
3. Warped, Melted and Corroded Lance Tubes
4. Entangled Cable and Power Cords
|5. Failed Gearbox Seals
6. Corroded Feed tubes
7. Loose packing tensioner
8. Worn motors, gears, steam traps,
Air Soot Blowers.
Air has less kinetic energy than steam at a given pressure (air pressure is normally 180 psig or 1.24 Mpa). The use of air soot blowers requires the installation of plant compressors to provide the necessary pressure.
Comparative advantages of air soot blowers:
- Less capital, operation and maintenance cost.
- More effective.
- Less damage the boiler structure.
Disadvantages when compared to the “Soot Gone” system.
- Requires a high pressure compressor with the dryer system.
- Carries a high capital, operational, and maintenance cost.
Water Canon Soot Blower.
The application of water cannon soot blowers is a relatively new development and is significantly different from conventional wall blowers. The water cannon directs a water jet across the furnace ox where it impinges on and removes slag from the opposite boiler wall.
Cleaning is performed by sweeping the water jet across the boiler wall. The primary mechanism of slag removal is the penetration of water into the outer slag layer and its expansion into steam, although thermal shock may also play a role . The concern regarding thermal shock and its long-term effect on water tubes is currently being evaluated.
Water is used as a medium for wall blowers, and almost never for long retractable soot blowers. 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, refractory, and boiler structure damage and failure due to thermal shock.
Advantages over Steam or Air soot blowers:
- More effective.
- Fewer capital and operation costs.
Disadvantages compared to Steam or Air soot blowers:
- In the short-term, affects the boiler structure, pipes, and refractories.
- In the long-term, ruins the equipment
- High maintenance costs
Acoustic Horns Soot Blowers
Acoustic horns, sometimes referred to as sonic horns, have become widely utilized in the last 25 years. The operating principle is to use intense sound pressure to dislodge ash. The horns operate with sound pressure up to 150 dB.
Acoustic horns are utilized in the economizer, air heater, electrostatic precipitator (ESP), and baghouse regions of the boiler. They also clean Selective Catalytic Reduction (SCR) reactors, which are used for NOx control.
The major advantage of acoustic horn blowers is their relatively low operating cost.
- Unable to remove deposits.
- Potentially resonant vibration of boiler structure.
When The Existing Approach is Unacceptable
The traditional soot blowers described above are not effective, are expensive to operate and maintain, and require maintenance of a large stockpile of spare parts, whose value can reach hundreds of thousands and even millions of dollars.
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