Fluidized Bed Boiler Tubes

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Plant Specifications

• Produces 9 billion kilowatt-hours of electricity annually
• Consumes 12,000 tons of blended coal daily
• 10 coal fired boilers
• 160MW Unit 10 was the nations first commercial scale atmospheric fluidized bed combustion boiler
• Unit 10 burns predominantly high sulfur coal from Illinois
• Evaporator area for unit 10 utilizes SA210-1, 57.15mm OD x 5.59mm wall internal rifled tube
• Units 1-9 utilize low NOx burners
• Unit 1 is evaluating selective non-catalytic reduction technology

Erosion Issue

• Original unit 10 bubbling fluidized bed boiler tubes supplied with 1mm induction fused 15Cr, 4.5Fe, 4Si, balance Ni spray coating
• Uninterrupted service life expected 5 years
• After two years service, unit experiencing tube leaks due to spray coating erosion failures
• Reoccuring forced outages due to tube leaks
• Spray coating failing due to poor erosion resistance, and coating disbonding exposing tube base material

Conforma Clad Solution

• Three alternative tube protection materials installed in unit 10 for evaluations: high chrome weld overlay 0.140” thick, thermal spray 0.040” thick, and Conforma Clad^® infiltration brazed cladding 0.030” thick.
• Two year service exposure resulted in coating failure of the weld overlay, and the thermal spray requiring the removal of test sections.
• Conforma Clad^® infiltration brazed cladding measured by eddy-current revealed thickness loss, in a localized area, in line with a catalyst injection nozzle at 0.002”. Remaining clad area had no measurable coating thickness loss.
• Fluidized bed tube life estimated at 15+ years service life

Conforma Clad ® infiltration brazed cladding measured by eddy-current revealed thickness loss, in a localized area, in line with a catalyst injection nozzle at 0.002"; remaining clad area had no measurable coating thickness loss