Slag build-up on water-wall and tubing of pulverized coal (PC) fired boilers causes problems for equipment operators. The slag forms due to a number of factors and varies from unit to unit. Coal composition, operating temperature, and fuel-to-air ratio are among the variables that impact the extent and nature of boiler slagging. Some of the effects of the slag build up, which causes equipment operators to implement boiler deslagging initiatives, are as follows:
- The heat transfer from the furnace to water-walls may be reduced.
- Large clinkers may form on the tube elements and fall, damaging the ash pit.
- Soot blowing frequency has to be increased, which accelerates tube erosion.
- Slag which forms and breaks away from the tubes may cause a thermal cycling that stresses the boiler tubes.
In order to prevent harmful boiler slag build-up, IGS employs its proprietary UTEx 6-040 or UTEx 6-041 ceramic cladding on bare boiler tube, or in conjunction with a MetalsprayTM HVAS or HVOF thermalspray coating for two primary reasons. First, the coating system provides boiler tube corrosion resistance. These materials are dense, silicon-based materials which do not react to the boiler gases. Second, their smooth texture, lack of reactivity, and low roughness (1.5 mil Rz) limit the formation of slag and clinkers. The material does not cause a change in the tube properties when applied, as in the case of boiler tube welding or corrosion resistant weld overlay. Preventing thermal cycling by boiler deslagging will reduce some of the stress that is involved in creating circumferential cracking of boiler tubes.
IGS is focused on protecting power boilers from the deleterious effects of the fuel and bi-products of combustion. Boiler deslagging through the use of ceramic cladding will lead to longer tube life and less damage to the boiler during operation.