Hot corrosion/erosion of metal

[Operator Mike]

New to this forum. Would like to know thoughts on erosion of metal in air pollution control systems of a municipal sludge incinerator. Sludge burned is abnormal due to high phosphrous content. Reactor temperature is 1450 degrees F utilizing olivine sand as the fluid. High phosphorous content sludge agglomerates on sand and hardens.

Heat recovery units experience erosion/corrosion that lead to water tube leaks. Coated likely wear areas with a product that lasted 1 year. What are the best coating options?

Also looking at lime to soften the fly ash and bind SO2-SO3 specie.

[deans]

(06-09-2009 03:03 PM)Operator Mike Wrote:  New to this forum. Would like to know thoughts on erosion of metal in air pollution control systems of a municipal sludge incinerator. Sludge burned is abnormal due to high phosphrous content. Reactor temperature is 1450 degrees F utilizing olivine sand as the fluid. High phosphorous content sludge agglomerates on sand and hardens.

Heat recovery units experience erosion/corrosion that lead to water tube leaks. Coated likely wear areas with a product that lasted 1 year. What are the best coating options?

Also looking at lime to soften the fly ash and bind SO2-SO3 specie.

Hi Mike,
Working in similar industry with high wear problems through errosion & corrosion, we got greta help for a U.K based company Eutectic Company Ltd, they manufacture & apply their own product, wire based, twin wire arc spray, too soon to say how successful it is but so far it looks very promising, their web address is http://www.eutectic.co.uk & their main company, German based is http://www.castolin.com Hope this may help.
Regards
Deans

[Gordon]

Hi Mike and Dean

to the Surface Engineering Forum.

Not easy to answer. Typically materials like NiCr, inconel 625, hastelloy C alloys and chromium carbide/NiCr applied by various methods arc, plasma HVOF. All have their pros and cons depending on the specific environmental conditions. Research into experiences from similar plant operations and get advice from coating applicators that have specific experience/specialisation in coating power plant boiler tubes and the like.

[Operator Mike]

(06-11-2009 02:29 PM)Gordon Wrote:  Hi Mike and Dean

to the Surface Engineering Forum.

Not easy to answer. Typically materials like NiCr, inconel 625, hastelloy C alloys and chromium carbide/NiCr applied by various methods arc, plasma HVOF. All have their pros and cons depending on the specific environmental conditions. Research into experiences from similar plant operations and get advice from coating applicators that have specific experience/specialisation in coating power plant boiler tubes and the like.

I would think I need to take into account angle of attack, velocity of attack and hardness and shape of particle?

[drramc]

Hi,
For erosion,you need to take account of the factors like angle of attack, velocity,hardness and shape of the particles, to enable decide on coating materials.For hot corrosion,you need to know the temperature and the nature of corrosive environment in the fluid.
For finding a solution on your own you can get guidance through my following books
1.Surface Wear-Analysis, Treatment, and Prevention,ASM Intl,2001 and
2.Advanced Thermally Assisted Surface Engineering Processes, Kluwer Academic Publisher,
MA,USA,2004, now Springer.
In addition to Ni-base alloys mentioned earlier,Kanthal (Fe-Cr-C-Al) type of powder has been found useful in spent liquor recovery boilers.This a single stage powder and need no bond coat while spraying.
ram chattopadhyay

[djewell]

You may also consider an amorphous coating for your pipes. They can be extremely hard and wear resistant, yet corrosion resistant as well. They can be applied via arc, HVOF, or HVAF.

[Operator Mike]

How does one go about testing the effect of an ash particle against a steel surface? Particle at high velocity etc. We are piloting a furnace with high phosphorous content biomass fuel and one with High-P biomass+lime. Lime addition affects SO2-SO3 content in flue gas to prevent downstream corrsoion in cold end of unit. Other benefits might include softening of ash particle.

What scientific methods exist for testing particle effect at high velocity against a steel surface? Would like to test ash particle and lime ash particle for differences. ASTM methods would be nice, ash particles are varied in size from 2-500 microns, smaller particles edges are jagged compared to larger particles.

[Gordon]

Hi Mike

ASTM G 76 - 1983 - Standard Practice for Conducting Erosion Tests by Solid Particle Impringment using Gas Jets.

I think you will need to develop your own specialised test to mimic as close as possible your specific conditions ie similar particle velocity, temperature and attack angle etc. Testing using simple erosion testing rig (grit blaster) at ambient temperature may give misleading results compared to that of elevated temperatures. A hot erosion test rig (similar to a thermal spray system) - particles entrained in a hot gas stream.