Abstract
Heat exchanger surfaces such as superheaters, reheaters, and economizers in power plants are subject to fouling depending on the type of fuel used. When fossil fuels (e.g., coal, fuel oil) or biomass fuels (e.g., wood, agricultural residues) are combusted, ash, sintered slag, and sticky alkali compounds accumulate on these surfaces, reducing heat transfer and operational efficiency. This article categorizes these fouling types from a technical perspective and evaluates the effectiveness of acoustic cleaning systems (sonic horns) in removing such deposits based on academic principles.
1. Fouling Characteristics by Fuel Type
1.1. Fossil Fuels (Coal, Fuel Oil)
Fossil fuels, due to their high inorganic content, result in large amounts of fly ash and sintered slag. In particular:
- High calcium and silica content,
- Presence of sodium, potassium, and vanadium oxides,
- High flame temperature,
increase the tendency for slagging and fouling on heat exchanger surfaces [[1]].
- Superheater and reheater zones: High-temperature sintered slag is commonly formed.
- Economizer: At lower temperatures, fine particles (powdery ash) accumulate and form layers on heat transfer surfaces.
1.2. Biomass Fuels
Biomass fuels contain alkali metal oxides (K₂O, Na₂O), chlorine (Cl), and low melting point compounds, which promote the formation of sticky ash and corrosive deposits [[2]].
- Chloride and sulfate buildup increases the risk of chlorine-induced corrosion, especially in low-temperature regions.
- Low ash melting point → leads to viscous, glass-like deposits in steam passages.
- High volatile matter in biomass → higher particulate loading → increased risk of severe clogging.
2. Thermal and Operational Impacts of Fouling
- Heat transfer coefficients drop by 20–40%,
- Flue gas exit temperatures rise,
- Boiler thermal efficiency decreases,
- Tube cracking and thermal stresses increase,
- Cleaning frequency increases → unplanned shutdowns occur [[3]].
Thus, cleaning systems that are non-contact, non-abrasive, and operable during process conditions are required, depending on the fouling characteristics.
3. Effectiveness of Acoustic Cleaning Systems (Sonic Horns) by Fuel Type
3.1. In Fossil Fuel Applications
In boilers burning fossil fuels, acoustic cleaners:
- Dislodge sintered dry ash through resonance-induced vibrations,
- Reach dead zones where steam sootblowers or rapping hammers are ineffective,
- Avoid physical abrasion, preventing erosion of tube surfaces.
📌 In finned tube economizers, acoustic sound waves penetrate the heat exchanger gaps more effectively, providing 2–3 times better cleaning performance compared to conventional sootblowers [[4]].
3.2. In Biomass Fuel Applications
- Sticky ash and alkali compounds have low adhesion strength, making them easier to remove with acoustic waves.
- Due to high particulate loads, short and frequent pulses (e.g., 10 seconds every 7–10 minutes) are highly effective.
- The post-cleaning ash entering the gas stream is more uniform, easing filtration downstream.
- Corrosive chloride deposits can be broken down with periodic sound exposure, reducing long-term corrosion risk [[5]].
4. Technical Integration and Engineering Application
- Acoustic horns can be easily mounted near access doors in economizer sections.
- Operational parameters:
- Frequency: 75–270 Hz
- Duration: 5–15 seconds
- Interval: every 7–12 minutes
- PID-controlled automation can activate horns based on boiler temperature and ash loading conditions.
5. Conclusions and Recommendations
Considering the different fouling characteristics caused by fuel types, acoustic cleaning systems offer the following advantages for both fossil and biomass-fueled power plants:
✅ Reduce cleaning frequency,
✅ Prevent material fatigue on boiler surfaces,
✅ Improve heat transfer and overall process efficiency,
✅ Lower filtration system load and enhance emission control,
✅ Minimize corrosion and wear risks.
To ensure longer-lasting, more efficient, and safer operation of energy systems, integrating acoustic cleaning into the engineering design is no longer optional—it is essential.
References
- Basu, P. (2013). Biomass Gasification, Pyrolysis and Torrefaction. Academic Press.
- Obernberger, I., & Biedermann, F. (2005). Characterisation of Particle Emissions from Biomass Combustion. Elsevier.
- Ganesan, V. (2012). Power Plant Engineering. McGraw-Hill.
- Andersson, H. et al. (2014). Use of Acoustic Cleaning in Heat Exchangers and Boilers. Chemical Engineering & Technology.
- USER Mühendislik. (2023). Sonic Horn Teknolojisi ile Temizlik Sistemleri Kataloğu.
- Williams, A. et al. (2012). Pollutants from Biomass Combustion. IEA Bioenergy.
