Kennametal Conforma Clad Tungsten Carbide Cladding Yields Powerful Cost Savings for Raichur Power Station
Friday, March 6th, 2009
For coal-fired power plants, pulverized coal moves through coal burner nozzles and burner tips at high speeds, producing significant component erosion. During operation, this incessant erosion results in the loss of the burner’s engineered geometry, forcing plant engineers to continuously make operational adjustments. Excessive erosion of burner geometry also impacts optimum combustion characteristics and overall plant efficiency, usually resulting in upward trending NOx emissions. In many cases, operators are constantly monitoring, repairing, or replacing internal burner components to maintain optimum performance.
Raichur Thermal Power Station (RTPS), located approximately 20 kilometers north of Raichur, India, is part of Karnataka Power Corporation Limited, owned and operated by Karnataka State. RTPS includes seven 210 MW capacity units that generate approximately 10,000 million units annually. The plant burns roughly seven million tons of coal at 40% ash per year, meaning extreme erosion and wear issues with the burner tips.
Life expectancy for coal nozzle tips at RTPS was eight to 12 months. The tips were stainless steel (SS310) with a 6-mm layer of weld overlay for protection. During annual overhauls, the tips were refurbished by replacing the eroded portion with new stainless steel plates protected with the weld overlay. After two to three rounds of repairs, the tips were discarded and replaced.
Kennametal Conforma Clad approached Karnataka Power Corporation Limited (KPCL) about using its infiltration-brazed tungsten carbide cladding at the Raichur Thermal Power Station to protect the plant’s coal nozzle tips. KPCL accepted the proposal and encouraged experimentation on the cladded coal nozzle tip, as Kennametal’s Conforma Clad had previous success at protecting and extending the life of other burner components.
The Kennametal Conforma Clad Solution – Field Test
Kennametal Conforma Clad initiated a year-long field test with two burner tips placed side-by-side in one of RTPS’s units. One of the tips was the standard SS 310 weld overlay-protected piece while the other was SS 310 protected with 1.0 mm of Kennametal Conforma Clad infiltration-brazed tungsten carbide, which metallurgically bonds with the base substrate (SS 310). After one year of service, both coal nozzle tips were removed and examined.
The weld overlay protected tip showed extreme erosion – the top splitter was completely eroded and severe erosion was found in the rest of the splitters and partition plates. The inner annulus plate was severely eroded on the boiler side of the weld overlay- protected tip. The Kennametal Conforma Clad protected tip maintained its size and shape and showed no erosion on the boiler side.
Using these results, the Kennametal Conforma Clad burner tip was expected to last a minimum of two years. However, after reviewing the findings of the field test, Kennametal Conforma Clad designed an improved coal nozzle tip for RTPS with improved protection on the splitter, leading edge, and top plate that extended the performance of the tips even further.
For further information visit: www.conformaclad.com