Improved Fuel Distribution Stationary Coal Nozzle

Fuel Distribution Kickers

Anti-Roping Coal Deflector

Improved Fuel Distribution Stationary Coal Nozzle

Power & Industrial Services has been developing ways to improve the wear life of stationary coal nozzles and nozzle tips for many years. In addition, we have been working with Nels Consulting in order to develop burner performance improvement techniques that enhance boiler performance. We have done our research using 2 scale two-phase flow modeling to test ideas. We subsequently field tested our findings at the PacifiCorp, Jim Bridger Power Station on 508 MW Combustion Engineering boilers.

The key to our success has been "Fuel Conditioning", using Fuel Distribution Kickers to disrupt the coal roping flow into and out of the stationary coal nozzle. Coal roping causes poor fuel distribution exiting the nozzle tip which results in flame variations. These flame variations range from sub-stoichiometric fuel rich zones, where the reducing atmosphere causes slagging and water wall erosion, to high oxygen zones, which create high thermal NO_x generation. With wide variations at each burner, unit control is difficult which causes NO_x levels as well as boiler efficiency to suffer.

Stage I Development

Our first stage development involved removing the stationary coal nozzle rib and adding two sets of coal distribution kickers to break up the coal rope.

Results

• 21% improvement in fuel distribution.
• Flame stabilization.
• Boiler control systems have become more effective, making load changes and NO_x control easier to achieve.
• Boiler slagging, water wall erosion and soot blowing costs are reduced.
• Improved fuel distribution and flame patterns have resulted in better lower furnace absorption and have also reduced exit gas temperatures by an average of 30°.
• Disruption of coal roping has reduced localized wear in the stationary coal nozzle and nozzle tip.
• After an 18 month on-line inspection, the nozzle tips showed little wear and were scheduled to run for another 18 months.
  
  

Stage II Development

Stage II development uses the same Fuel Distribution Kickers with the addition of an Anti-Roping Coal Deflector attached at the inlet to the stationary coal nozzle.

Results

• Uniform coal distribution exiting the coal nozzle.
• Further reduction of wall slagging and soot blower costs.
• Improved flame stabilization, due to uniform fuel distribution, has increased boiler efficiencies while reducing exit gas temperatures by 30° - 50°.
• Easier NO_x control.

Our Fuel Conditioning techniques have shown dramatic improvements in burner wear life and burner performance.

We have modeled a new tip design to go along with the coal nozzle so we can offer both them as a package. The new tip does not have splitter plates and will still give direction flow during 30° up or down operation. Tip life should significantly improve without splitter plates.

Note: The number, size and location of our Kickers and the size of the Anti Roping Deflector are determined by Nels Consulting based on coal and air flow data supplied for each unit.

Advantages

• Localized wear at the coal nozzle outlet and nozzle tip caused by coal roping will be greatly reduced. Longer adjustable tip life.
• Uniform coal distribution exiting the tip will result in a more stable flame, lower L.O.I. and better NO_x control.

Disadvantages

• This design increases the pressure loss through the primary air system by 1.7 to 2.0 inches of water. This could be a problem at plants where exhausters are maxed out.
  
  
  

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