Biomass energy is a hot topic in our current climate. While some operators build new biomass-fired boilers, others retrofit old coal-fired boilers to burn biomass. Alcali- and sulfide-induced corrosion, however, has become a problem for many boilers.
Cracking the Code of Biomass Corrosion with HVTS
Contributed by | Integrated Global Services, Inc. (IGS)
IGS’s European operational team performed a High Velocity Thermal Spray (HVTS) application at E.ON Värme Sverige AB Åbyverket, Örebro, Sweden, on a steam boiler in 2017. ÅP5 is a 170 MW biomass-fired CFB boiler built in 1988 by Götaverken-Generator (currently Valmet Technologies Inc.) The steam conditions are 150 bar/540°C.
Åbyverket wanted to upgrade the previously installed erosion protection in preparation to the fuel change during the boiler revamp. 20 m height of waterwalls were being changed on all 4 walls.
Current Fuel mix:
|
Stemwood |
10 % |
Peat |
20 % |
|||||
|
Creosote |
30 % |
Saw dust |
20 % |
|||||
|
Branches, peaks |
5 % |
Dry wood chips |
15 % |
|||||
|
Mix B5 |
Cl 0,3g/kg |
S 1,3g/kg |
||||||
|
Dust chem |
SO3 7,5-41,6% |
Cl 0-5% |
K2O 11-21% |
|||||
|
Flying ash |
Cl 0,3% |
S 1,6% |
Si 19% |
Ca 12,5% |
pH 12,5 |
|||
Biomass Fuel Sources
Biomass fuel can be derived from various sources, including virgin wood, plants or animal residues, as well as recycled materials, such as demolition wood. Depending on the type of biomass, the combustion can generate more or less corrosion and erosion. The type of boiler is also an important factor: fluidized bed boilers will optimize combustion but will also generate erosion. Various factors influence the choice of erosion/corrosion protection.
Innovation in Corrosion Protection
IGS Subject-Matter Expert on Waste to Energy and Biomass Boiler coatings, Cyril Narjoz, said: “Some boiler operators believe that weld overlay is the only solution to protect boiler walls from biomass-induced corrosion safely. It was true many years ago, but now HVTS has proven its performance in several independent tests and practical applications. With its on-site application being much faster and easier than weld overlay, HVTS has become a favourable alternative for corrosion protection”
HVTS Application for E.ON
For E.ON Värme Sverige AB, IGS applied 993,5 m2 (20 m band) of HVTS during a 3-week period, working 24/7 with eight spray units. Director of IGS European Operations, Petr Sovadina, commented: “Our team is well-trained and experienced, however, this was our first large project in Scandinavia. We found E.ON engineers to be extremely sharp and skilled, this helped us avoid many obstacles during the project execution. We understand that operators need to squeeze critical path of boiler operations, and that is the reason why we mobilized an 8-gun team to spray 995 square meters of waterwalls in just 21 days. We are proud of our quality and provide a warranty for our work.” A boiler engineer with 20 years of experience, Petr spent the last 6 years spraying metal alloy cladding to protect boiler surfaces.
Annual Inspection
In August 2018, IGS conducted its first annual inspection of the cladding, and the result was as expected: no deviation on the HVTS cladding thickness. A thickness mapping was performed and shared with the customer. E.ON Site Manager has commented: “Our work is extremely important, that is why we choose the best service for our boilers. We closely monitor jobs performed in our boilers, and I shall admit that IGS has an experienced and quality-oriented team that listens to the customer needs and deliver on their promises.”
2018 inspection – front wall 2018 inspection - Waterwall near refractory
Inspection the following year was conducted and the report stated: “No black areas were detected (bleed through), the cladding turned out to be completely intact and without material loss.
Measurements taken showed results similar to those from the year of application.”
2019 inspection – thickness readings 2019 inspection – Waterwall near refractory
About Integrated Global Services
Integrated Global Services (IGS) is an international company with a 38-year history providing on-site corrosion protection for power boilers, oil and gas pressurized vessels and heat recovery boilers. IGS has protected more than 2,500 industrial boilers worldwide, including 500+ CFB and BFB boilers. IGS engineering staff utilizes own lab to develop and test proprietary metal alloy cladding to cope with corrosion and erosion problems of mission critical equipment.
IGS Chief Technology Officer, Iain Hall, commented: “Developed and tested in 2016, our bespoke metal alloy cladding for boiler waterwalls has shown unprecedented corrosion resistance at high temperatures found in Biomass boilers combined with its ease of on-site application.”
Global Service – Local Support
Having operational centers in strategic locations in North America, Europe, Asia and Africa, IGS delivers its services worldwide, but each market is special. Sören Stutin, General Manager IGS Scandinavia, commented: “Scandinavia is a highly educated market. Our boiler engineers have a deep understanding of metal wastage problems in boilers and multi-year experience of using thermal spray solutions. But what is the most important – Scandinavian engineers are open to innovation and absorb the best available technology to improve their operations. Swedish engineers are well-educated, curious and savvy. That makes our boiler industry so advanced.”
Summary
As the European energy market is experimenting with different biomass fuels, boiler engineers will face more arduous corrosion situations. IGS can provide an effective barrier on the existing pressure parts, which will prevent further need of panel replacement.
About IGS and Cetek
Integrated Global Services, Inc. (IGS) is an international provider of surface protection solutions headquartered in Virginia, USA. IGS operates operational hubs, subsidiaries, and sales offices around the world to service global asset owners and operators.
The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag
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