Due to increasing stringent regulations on greenhouse gas emissions operators of thermal power plants face challenges to which they must adapt, including the requirement to co-fire (simultaneously burn different fuels in one boiler) with biomass. A key limiting factor on large scale co-firing is the response of plant components to the altered ash composition formed during co-firing.

Combustion of biomass produces vapours of alkali halide salts in the flue gas which condense on boiler tubes, causing accelerated corrosion of tube walls. This work consists of experimental and simulation based research to investigate the effects of co-firing and ash agglomeration, deposition and slagging on superheater tube life.

The objectives of this project are to:

  1. Determine the rates of superheater tube wall loss due to corrosion for a variety of peat-biomass mixtures,
  2. Assess the degradation of mechanical performance of material due to corrosion
  3. Determine the maximum allowable fractions of biomass co-firing
  4. Incorporate corrosion sub-models into thermos-mechanical models for high temperature structural materials
  5. Use models to accurately predict boiler tube performance and life expectancy.

Projected research outputs: An experimental methodology developed to measure the corrosion rate of varying ash compositions on metals.

The effect of different salts on the corrosion rate of metals and the elements of the ash which impact this.

Insight into the corrosion process, and its effect on subsurface material degradation and corrosion layer structure.

An understanding of the microstructural effects of corrosion and the impact on material performance.

Models which incorporate corrosion effects on tube life expectancy undergoing creep and fatigue damage.

Duration: 3 years

People:

  • Principal Investigator: Conor O’Hagan
  • Research Team:
  • Academic Collaborators: Dr. Rory Monaghan, Prof. Sean Leen
  • Input from: Dr. Barry O’Brien, Mr. Richard Barrett
  • Industrial Collaborators Irish Research Council, ESB & Bord na Móna

Funder: Irish Research Council, ESB & Bord na Móna

Publications:

Journal:         

C. P. O’Hagan, B. J. O’Brien, F. Griffin, B. Hooper, S. B. Leen, and R. F. D. Monaghan, “Porosity-Based Corrosion Model for Alkali Halide Ash Deposits during Biomass Co-firing,” Energy & Fuels, vol. 29, no. 5, pp. 3082–3095, 2015.

C.P. O’Hagan, R.A. Barrett, S.B. Leen, R.F.D. Monaghan, “Effect of High Temperature Corrosion on the Service Life of P91 Piping in Biomass Co-firing,” J. Press. Vessel Technol., Under Review

Conferences proceedings:

O’Hagan CP, O’Brien BJ, Leen SB, Monaghan RFD. Experimental Characterisation of Materials for Biomass Co-firing. European Biomass Conference and Exhibition, Hamburg, Germany, June 2014.

O’Hagan CP, Barrett RA, Leen SB, Monaghan RFD (2015) Effect of High Temperature Corrosion on the Service Life of P91 Piping in Biomass Co-firing ASME PVP-2015 Boston, Massachusetts, USA, , 19-JUL-15 - 23-JUL-15

Images:

Images of tubes in-situ and tubes following removal from plant

Image showing the active oxidation process

SEM image and EDX element maps of P91 sample exposed to synthetic salt for 4 days at 540°C

SEM image and EDX element maps of P91 sample exposed to synthetic salt for 4 days at 540°C