External Corrosion of Boiler Tubes Due to Chlorides in Fuel. 2

[stanweld]

A biomas fuel for firing a boiler has 0.01% Cl. Will this cause a problem with corrosion, especially if austenitic stainless steel is used for superheater tubes? Please provide any published data in this regard.

 

[macmet]

I do not have a lot of firsthand knowledge with superheaters, however I did work at a biomass company for a while and have some documents on the effects of chlorides on stainless steels.

If you would like, I can forward these to you. None of them were prepared by me, but I think there may be some useful information in them. Some are prepared by FW, BW, etc.

Please provide an email address or some simple way to transfer the files if you'd like to check them out.

 

[stanweld]

Thank you.
stanleyjg@zhi.com

 

[macmet]

Done and done.

Let me know how they work for you.

I might actually have a few more, but I'm at work now and didn't have time to thoroughly go through my notes.

 

[EdStainless]

Yes, it will. However your Cl level is actually rather low. A lot of coal has much higher Cl. I have seen 0.3% Cl.

There are some EPRI papers on this. I think that they are old enough to be free. Try searching on epri.com

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Plymouth Tube

 

[stanweld]

That is what I'm finding out from added research. High HCL concentrations > 400 ppm are definitely a problem in Trash Boilers.

 

[rmw]

There are lots of problems in trash boilers, chlorides being just one among many.

rmw

 

[davefitz]

some useful information and papers at <

http://www.ieabioenergy.com>

As I recall, the main problem is related to co-firing biofuels with coal. The coal has higher levels of SO2 in the fluegas, and this sulphur combines with the potassium, sodium, and phosphate in the biofuels to form a low melting temperature eutectic salt on the otuer surface of the high temperature superheater tubes. If there are local pockets of reducing environments near these tubes ( as evidenced by high CO levels), then this eutectic slat remains molten and fluxes away the protective oxide coating of the tubes.

One solution is to avoid hi CO levels by improving the biomass fuel feed arrangement to minimize slug flow pockets of unburned biomass from bypassing the main flame zone . Apparently this problem was solved at the DRAX station in England- review their fuel feed solution.