Analysis of Combustion Ash from Biomass Power Generation by EDXRF

EDXRF Analysis of Combustion Ash from Biomass Power Generation Using EDX-8100

Importance of the Topic
Biomass power plants increasingly rely on circulating fluidized bed (CFB) boilers to generate carbon-neutral electricity from wood chips, pellets, and palm kernel shells. Alkali metals such as sodium and potassium in combustion ash can adhere to bed materials, causing agglomeration, defluidization, and equipment damage. Rapid, minimally invasive monitoring of these elements is essential for maintaining efficient and reliable operations.

Study Objectives and Overview
This application note reports on qualitative and quantitative analysis of palm kernel shell (PKS) combustion ash and its coarse agglomerated particles using Shimadzu’s EDX-8100 energy dispersive X-ray fluorescence (EDXRF) spectrometer. The aim was to identify surface-bound alkali metals responsible for agglomeration and to compare untreated ash with homogenized and crushed samples.

Sample Preparation and Methodology
Four ash samples were analyzed:

• ① Coarse gray bottom ash (untreated and crushed)
• ② Coarse white bottom ash (untreated and crushed)
• ③ Fly ash (fine powder, pressure-molded)
• ④ Crushed bottom ash (pressure-molded)

Untreated samples were measured directly, while crushed samples were homogenized using an agate mortar and ball mill before pressure-molding. The EDX-8100 measured elements from carbon (Z=6) to uranium (Z=92) using a silicon drift detector and Rh target tube under vacuum.

Equipment Used

• Instrument: EDX-8100 EDXRF spectrometer
• Detector: Silicon drift detector (SDD)
• X-ray tube: Rh target, 15–50 kV, auto μA
• Collimator: 10 mmφ
• Atmosphere: Vacuum

Main Results and Discussion
Qualitative overlay of untreated and crushed gray ash revealed significantly higher Na and K signals on untreated surfaces, confirming their adhesion to coarse particles. Quantitative analysis by the fundamental parameter method showed:

• Untreated coarse ash (①-a) contained up to 0.24 wt% Na2O and 11.9 wt% K2O, decreasing to 0.095 wt% and 7.92 wt% after crushing (①-b).
• Fly ash exhibited lower Na and K but higher CaO (~31.2 wt%), indicating effective removal of melting-point-reducing components.
• Non-detected or minor levels of volatile elements such as Cl in some samples.

This demonstrates that untreated agglomerates concentrate alkali metals on their surface, promoting defluidization.

Contributions and Practical Applications
EDXRF enables rapid, minimal-preparation monitoring of key elements driving boiler fouling. Periodic on-site measurements can detect early agglomeration, guide operational adjustments, and prevent unscheduled shutdowns or damage to CFB boilers in biomass plants.

Future Trends and Opportunities
Advances in portable EDXRF instruments may allow real-time field monitoring of ash deposits. Integration with predictive maintenance software and machine learning could further optimize combustion conditions and extend equipment life. Expanded element libraries and improved detection limits will broaden applications across diverse biomass fuels.

Conclusion
EDX-8100 EDXRF provides effective qualitative and quantitative analysis of alkali metals in biomass combustion ash. The method identifies surface-bound Na and K that contribute to agglomeration, supporting proactive boiler management and sustained power generation efficiency.

References

1. Yamashita T., Shibata T. Development of Combustion Technology in CFB Boilers. Sumitomo Heavy Industries Technical Review, No. 177, Dec. 2011, pp. 5–8.
2. Visser H.J.M. The Influence of Fuel Composition on Agglomeration Behavior in Fluidized-Bed Combustion. ECN-C-04-054, 2004, pp. 1–43.