Newsroom - Oct 12, 2022
Fuel Diversification Causes Corrosion of Boiler Pressure Parts Leading to Tube Leaks
Colin Bateman, IGS Corrosion Mitigation SME, explains how fuel diversification causes corrosion of the boiler pressure parts, leading to tube leaks that result in costly shutdowns.
Watch until the end to see how these forced shutdowns can be prevented.
The power industry today faces a lot of challenges, and I think there’s a lot of pressure on the industry to become more environmentally friendly to eliminate the burning of fossil fuels or to minimize that as much as possible.
What we’ve seen a lot of plants working on is improving their efficiencies in how they operate but also in changing the feedstock or the fuel that they burn. The circular economy of waste whereby everything that can be recycled is recycled and put back into that process or can be reused to make whatever product it was made and used to make originally. What cannot be recycled or efficiently or effectively recycled is then used to create energy, so you recover the energy that’s in that waste rather than just putting it in a landfill by combusting it.
Plants are burning a wider range of fuels where historically, a plant and a boiler would be specifically designed for one fuel type, for example, coal or whatever, these days, they’re burning a wide variety.
The new materials they’re combusting contain higher levels of corrosive species such as chlorine for example which is a very aggressive pitting corrosion material in these boilers. The two biggest challenges they face are corrosion from burning these different fuel types, which have more aggressive corrosive species, and from fouling because these fuels don’t combust as efficiently or as cleanly as traditional fuels like pulverized coal, etc.
They get much more residue in the boiler which can create a lot of challenges with the efficiency of the unit and particularly towards the back end problems with blocking up all of their superheaters, economizers, etc.
There’s a lot of pressure on the plants to diversify the fuel types. There’s a lot of pressure on them to reduce costs, so you start then looking at what cheaper fuels you can burn, and those cheaper fuels tend to be less refined. They’ve got more contaminants which then can possibly create more challenges in terms of the operation of the unit.
When you’re operating the boiler, you’re combusting the fuel. If you don’t manage that combustion process carefully, then you get deposition onto the surface of the internal of your boiler of these corrosive species so that can be in a scale formation, it can be a deposition just in terms of from the flue gases. And what those corrosive species will do is they’ll start to attack the metal, which is what your boiler water walls are constructed from.
And as that corrosion takes place, you then start to lose the wall thickness of the pressure boundary, and then once that gets to a critical point then, the internal pressure in the tube will cause the tube to burst.
And if you get a tube burst, you have to shut down the boiler. Shutting down the boiler takes time. You’ve got to cool down the boiler. You then have to locate the leak, you’ve got to cut that out, and you’ve got to weld in a new piece of the tube, so it can typically be three-four days.
For most plants, you’re looking at hundreds of thousands of pounds of lost revenue or hundreds of thousands of dollars of lost revenue over those three or four days, which could be avoided if they had a tube that was protected with a suitable corrosion barrier.
At IGS, we specialize in the field application of metal cladding technologies. What these metal cladding technologies will do is they’ll put a high-grade or high nobility alloy onto the surface of your pressure boundary, which then is resistant to that corrosive environment.
It’s then going to prevent any corrosive degradation of your pressure boundary. In the situation with boilers, we can go into a boiler during an outage and use high-velocity thermal spray in order to apply the IGS cladding onto the surface to protect those surfaces from any further degradation.
What that does is it obviously freezes the condition and allows you to operate without the risk of the pressure boundary being reduced and then prevents or eliminates the risk of having unplanned outages due to leaks from corrosion.