2 replies to this topic

[jonol92]

Hello,

I'm a first year chemical engineering student currently on an internship working on a project investigating fouling problems in a small power plant burning 95% poultry litter.

An option i would like to explore is the surface treatment of standard carbon steel by applying a paint in an attempt to smooth its surface and make nucleation of fouling deposits less likely. I wouldn't expect massively impressive results from this method but seeing a small effect would be nice!
Is there a paint that is likely to meet this requirement to some extent or is this idea fruitless? Naturally i want to keep costs to a minimum but as much money as necessary can be spent. The paint would need to be applied to the front wall of the superheaters and a another heating surface where gas temperature passing over is 800-1100 degrees celsius. Hot gases leaving the furnace typically impact these areas currently and large deposits build up too quickly. Please don't worry about heat transfer here or other methods of dealing with the fouling, i'll cover that bit! I just want to know if paint is a viable option and be pointed in the direction of something that might have the desired effect.

Thanks in advance,
Jonathan

[Art Montemayor]

Jonathan:

This is a very interesting and possibly a very important problem to resolve from a practical and economic point of operation.

I would not expect a paint, coating, or similar application to work successfully. My experience tells me that the most direct, and practical method to apply is a strictly alloy selection method. The stainless steels, chrome, and nickel alloys come immediately to mind. The reason I emphasize an alloy instead of a coating is that I have had far too many coating failures in the past - most. if not all of them causing more problems and harm than good. When a coating starts to fail or fall short of expectations, it usually means it will contaminate or foul your operation worse than what you originally had.

Of course, the alloy answer is always, in my experience, the most expensive answer. But, as a practical matter, that should be expected. There are no free rides or free lunches in engineering. There is always a trade off one has to confront before coming to a succesful solution. The best advantage of using an appropriate alloy is that the maintenance to keep it doing its job is nil as compared to a coating or surface treatment.

[jonol92]

Thanks for your response, much appreciated!

I was uncertain as to whether this method would be effective in this application but i guess that confirms it. Currently i'm exploring the installation of extra sootblowers in the right places to clean off the fouling rather than preventing it. The problem is that blowing high pressure steam at carbon steel three times a day seven days a week tends to make it a bit weaker (to say the least) so the station here currently coats the target surfaces with inconel (makes sense, it puts up with high temperature and is resistant to corrosion)!

As you said, that's not exactly cheap and thats just a coating of the alloy.
So are you talking about a coating of alloy over the current surfaces or do you mean replacing the actual components entirely with a new material (cos that sounds like a fair old job in a power station!)? I suppose if you are talking about the latter then this is really a theoretical exercise in this case but something to learn from for new builds, but a coating may be feasible in the station here.

Thanks again, Jon