A steam loop for materials testing at 600C in a biomass and waste fired boiler : results of corrosion testing

• A steam loop for corrosion testing was constructed in Esshete 1250 and attached to one of the superheaters in a 100 MWth bubbling fluidised bed (BFB) boiler. The loop raised the final steam temperature to about600°Cat 140 bar.  A number of different test materials were welded into the loop for evaluation at low temperature (500°Csteam) and high temperature (600°Csteam). Their wall thicknesses were measured with a high resolution ultrasonic probe before and after exposure. A number of sections were examined metallographically after exposure. The steam loop was in service for one firing season (about 5500 h) and the fuel mixture was initially a biomass mix co-firing with 15% coal. However halfway though the firing season the coal was replaced with 15% packaging waste containing plastic and aluminium.  The latter mixture (biomass and waste) was highly corrosive and accounted for most of the corrosion.   The alloys with the highest Ni and Cr contents, Haynes230, AC66 and HR11N, showed negligible steam-side corrosion. The 11% chromium steel X20  and the nickel-base alloy HR11N were not tested at the higher steam temperature because of strength considerations. Regarding fireside corrosion at500°Csteam the alloys with the best corrosion resistance were  Haynes 230, HR11N, AC 66 and HR3C followed by Esshete 1250 and  TP347HFG.  The corrosion rate of X20 was unacceptably high and is totally unsuitable for this fuel mix.  At 600°C  Haynes 230 showed the lowest corrosion rates, followed by TP 347 HFG, HR3C, AC66, and  Esshete 1250. Large amounts of internal corrosion were seen.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Maskinteknik -- Energiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Mechanical Engineering -- Energy Engineering (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik -- Korrosionsteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering -- Corrosion Engineering (hsv//eng)

Nyckelord

Biomass

superheaters

600C steam

corrosion

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