Greg Epelbaum, Boiler Engineering Manager, Covanta Energy

Eric Hanson, Boiler Reliability Director, Covanta Energy

Dr. Michael Seitz, President AmStar Surface Technology

May 12, 2010, Orlando, Florida, USA

• Fireside corrosion is the biggest challenge for EfW boilers

• MSW is the most heterogeneous, unpredictable fuel, which constantly changes with weather, seasons, locations, economy, politics, social behavior, etc…..

• Fireside corrosion is typically driven by the following 4 simultaneously occurring mechanisms:

– corrosion by gaseous phase including “active oxidation” by

Challenges for EfW boiler Reliability

– corrosion by gaseous phase including “active oxidation” by chlorine (HCl, Cl2) ;

– condensation of alkali and heavy metals chloride and/or sulfates;

– deposit induced corrosion and sulfidation of condensed chlorides ;

– molten salts eutectics cause dissolution of protective oxide scales and tube metal

• Intensity of corrosion can be controlled to a certain degree by a proper design for an EfW boiler :

– combustion system and furnace design;

– proper design criteria for the main operating parameters;

– “smart” superheater location

• Boiler tube surface protection:

– refractory;

Solutions to improve EfW boiler Reliability

– refractory;

– tube shields;

– surface treatments, such as weld overlays, thermal sprays, laser claddings and fused coatings, and AmStar 888® is one of these technologies, and like some others, it can be use as a part of the solution;

– Relevance and importance to EfW future

• The material development of Alloy 888® was initiated in 2002, in a partnership between Special Metals Welding Products Company and AmStar Surface Technology.

• This material (which is a Nickel Chrome alloy, with carbide and boride additions) was developed for environments with erosion, corrosion, or a combination of both. It became a proven technology for many large utility boilers, Fluid Bed boilers, recovery boilers, refineries before it entrance to EfW.

• The coating is applied using a high velocity spray system

AMSTAR 888® CLADDING MATERIAL

• The coating is applied using a high velocity spray system (HVCC), and requires no post treatment:

– can be field or shop applied ;

– can be applied over untreated surface or potentially over treated surface, such as Inconel weld overlay;

– can be repaired if defects occur in the future

• AmStar 888® cladding technology is a combination of the new alloy and the special coating technique. AmStar Surface Technology Company is developer and applicator.

• AmStar 888® cladding technology was proven in other industries, but not in EfW.

• To find cost effective alternatives to Inconel Weld overlay.

• To expand boundaries of boiler tube protection by surface treatments:

AMSTAR 888® CLADDING TRIALS AT COVANTA PLANTS

Objectives

•treatments:

– different facilities;

– different boiler designs;

– different boiler areas

Montgomery Boiler, MSW 600TPD: 885psi, 830F, 171KPPH

AmStar Pass2 RW application at Montgomery

Flue Gas T: 1300 – 1600 F; Tube metal t: ~550F

Pass2 RW ~130 ft2 area prepared by AmStar prior to cladding

B#3 Jan-08 Outage Coating thickness reading before applying Passivator

AmStar Roof WW application at Montgomery

Flue Gas T: 1000 – 1200 F; Tube metal t: ~550F

Roof WW area covered by slag before it was removed prior to AmStar’s cladding

B#3 Jan-08 Outage Roof (Screen-FSH) ~130 ft2After applying Passivator

AmStar Pass2 RW application at Montgomery

Boiler 3 - March 2010 Outage

Amstar Coating - 2nd Pass RW

TOP 7' DOWN

Tube # thickness thickness

Left 13 19 31.3

17 22.1 21.1

B#3 Mar-10 Outage

Pass2 RW inspection: No Coating loss, Passivator’s intact

B#3 Mar-2010 Outage Pass2 RW Inspection

21 23.4 18.8

25 20 31

29 38 22.5

33 24.6 23.2

37 31.8 32.8

Right 39 29.7 26.7

AmStar Tube Trial at Montgomery B#2 FSH

Flue Gas T: 1000 – 1200 F; Tube metal t: ~750 - 800F

B#2 Sep-09 Outage AmStar Tube sample (third from Left) after ~ 6months operation

York Boiler, MSW 448TPD: 800psi, 800F, 138KPPH

AmStar Furnace RW application at York B#2

Flue Gas T: 1500 – 1800 F; Tube metal t: ~530F

B#2 Pass1 RW ~200 ft2 area with some refractory obstruction prior to cladding

12 months later: no thinning ordelamination in the area ofcladding applied over old WO

AmStar Tube Trial at York B#1 Finishing SH

AmStar 888® cladding on left tube after 3.5 years of operation in comparison to an unprotected adjacent tube being in service for only 18

Flue Gas T: 1200 – 1500 F; Tube metal t: ~730 - 770F

being in service for only 18 months;

Mar-2010 Outage:Same condition after ~5 years of

operation

Niagara Boiler, MSW 1100TPD: 1275psi, 750F, 305KPPH

AmStar Tube Trial at Niagara B#4 Finishing (SH3)

Flue Gas T: 1200 – 1300 F; Tube metal t: ~750 - 790F

Mar-2010 Outage:Trial tube removed during SH3 replacement after ~1 year of operation

Essex Boiler, MSW 760TPD: 650psi, 760F, 240KPPH

Metal Protection Trial in Essex Platen SH

Installed in Essex #1 Mar-08� Panel 3-4 Top 40ft: Ams888

� Panel 3-5 Top 40ft: Cladding Y

� Panel 3-6 Top 40ft: Cladding X

Flue Gas T: 1400 – 1600 F; Tube metal t: ~750 - 820F

AmStar Platen Finishing SH application at Essex B#1After 1 year of operation

AmStar Panel 3-4 (left) and Coating Y Panel 3-5 (right)

Panel 3-7 (non-trial) with Inconel 625 weld overlay for the lead and trail tubes and 8 unprotected SA-213T22 tubes in between

AmStar Platen Finishing SH application at Essex B#1

After 2 years of operation

AmStar Panel 3-4 at 10' from Roof (lead tube at the front).

AmStar Panel 3-4 at 35’ from Roof welded to non-trial panel with Inconel 625 weld overlay for the lead and trail tubes and 8 unprotected SA-213T22 tubes

Conclusion

• AmStar 888® cladding technology has been tested in a number of field trials over the last 4 years at different EfW facilities.

• It has shown very encouraging results, with no thickness loss (wastage) for Waterwalls (including those covered by old and deteriorated weld overlays).

• It has also shown very promising results for some superheater applications, where the metal temperatures do not exceed a level conservatively estimated to be approximately 800 F (425C). (425C).

• However, at the Essex FSH trial AmStar 888® cladding, as well as other surface treatments, have not achieved the desired performance for certain SH tubes:

– more investigation and field trials should and will be conducted;

– especially with a trend in EfW calling for higher plant efficiency

Higher SH Steam P & T would result in more challenging

superheater location

Many thanks to the plants for their support for these field trials