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Circulating Fluidized Bed (CFB) Boiler Erosion

HVTS Claddings for Coal Burning CFB Boilers:

Summary:  IGS leverages decades of experience with over 500 Circulating Fluidized Bed (CFB) Boiler High Velocity Thermal Sprayed (HVTS) cladding applications to stay at the forefront of maximizing run time and minimizing outage frequency and cost for Coal burning CFB Boilers globally.  IGS 8450 HVTS cladding has been successfully used over the past decade to provide scalable (cladding thickness is adjusted to meet specific wear rates in different locations), proactively manageable and fully refurbishable boiler tube protection, rendering erosion damage and mechanical repair of boiler tubes in Circulating Fluidized Bed (CFB) Boilers an unnecessary practice.

Corrosion-Erosion of Circulating Fluidized Bed (CFB) Boilers

Circulating Fluidized Bed (CFB) Boilers by design offer a number of advantages over conventional boiler designs, including ability to fire a wide range of fuels and lower combustion temperatures which reduce emissions.  The bottom approximately one third of these boilers is generally protected by castable refractory, but the top approximately two thirds have exposed tubes to maximize radiant and convective heat transfer.  These boilers operate by combusting fuel in a fluidized bed of non-combustible particles.  As these particles (bed material) recirculates in the furnace, it causes wastage of the furnace water wall / evaporator panels by corrosion-erosion mechanisms, an unavoidable consequence of this design of boiler.  This wastage is typically found at refractory to water wall / evaporator interface, field weld joints in the furnace (typically 4-8 meters above the refractory interface) and at tubes up stream of the cyclone inlet(s) at the top of the furnace as ash travels out of the furnace and into the cyclone.

On-Site HVTS Cladding Mitigating CFB Metal Wastage

IGS 8450 High Velocity Thermal Sprayed (HVTS) cladding is ideal for protecting CFB boiler tubes from the above described typical wastage mechanisms.  For CFB Boilers, IGS applies high alloy materials with both a ceramic and metallic component to produce a homogenous (particles typically <50um), hard (typically in excess of 1,200Hv300) and toughness to provide optimal application and performance properties for CFB Boilers.   IGS utilizes only true High Velocity application process, where atomization of the material occurs before or in a super-sonic gas stream, the only way in which to achieve such optimal cladding properties needed for reliable and predictable long-term cladding performance.  IGS HVTS offer our customers the following advantages over other thermal spray and cladding solutions;

  • IGS HVTS cladding is proactively managed to eliminate tube wastage. With IGS claddings, the HVTS cladding becomes a controlled protective sacrificial barrier that can be managed to eliminate tube wastage and therefore tube restoration in CFB furnaces indefinitely.
  • IGS HVTS cladding is completely scalable, which creates the opportunity for customers to extend their run time between outages with the assurance that they will not suffer a tube leak, and maximize the return on investment of their operating assets.

IGS Experience Cladding Metal Inside CFBs

IGS is the pioneer in the use of Thermal Spray claddings in CFB boilers.  IGS has completed over 500 CFB applications over the past two decades.  Having completed so many applications over so many years uniquely positions IGS as the knowledge leader in materials, application technology, installation, refurbishment and operating methods for successful application of our HVTS claddings.  Simply stated, we are the best positioned to know what works and what does not in many varying CFB Boiler types burning a wide range of fuels across the globe.  Where others may be experimenting with potential solutions, IGS has trusted and proven solutions.

Optimized Solutions for CFB tube wastage protection

Over the past decade, we have leveraged this experience and knowledge to develop unique materials and methods to provide reliable and predictable protective barriers in the most challenging CFB boilers globally.  We have learned that:

  • For the use of thermal spray coatings to make sense economically, they must be managed proactively so as not to expose underlying substrate material. Investing in thermal sprayed coatings and having to expend the time and money on tube restoration is not optimal.  IGS has proven success in accomplishing this.
  • Materials need to have specific properties to successfully protect boiler tubes reliably over multiple outage cycles, and for the life of the boiler. Hardness, toughness and residual stress properties are among some of the critical characteristics that determine whether coatings will wear in a controlled manner, and not cause secondary problems in the furnace such as accelerated wastage of the tubes at the coating interface, or accelerated localized wear should the coating failure in localized areas.

 

IGS coatings prevent accelerated localized wear.

 

  • Managing long term boiler tube protection is a larger challenge than just the initial application. Unlike many environments where protective claddings or coatings are used, in CFB boilers, the boiler tube protection system such as IGS HVTS cladding is a sacrificial layer.  This means it must be proactively refurbishable to be effective.  IGS creates value for its clients not only through provision of skilled personnel and proprietary fit for service HVTS cladding solutions, but also through expert inspection and wastage modelling which allows IGS to specify what materials, at what thickness should be applied where both on initial application and periodic refurbishment, to ensure long term dependable performance.

 

IGS performs high-temperature erosion testing in-house.

 

IGS CFB Boiler HVTS cladding offering creates value for CFB Boiler owners and operators by ensuring reliable and predictability of the performance of their boiler assets. Customers who view reliability and dependability of their units as mission critical to their revenue generation and / or their customers will experience the economic benefit of IGS technology and approach to CFB Boiler reliability.  Through our strategically placed operations in the Americas, Europe, Africa, CIS, Middle-East and Asia Pacific regions, IGS focuses on creating value for our customers globally by ensuring reliable and dependable performance of their mission critical assets.

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