Pilot Scale Studies of the Fireside Corrosion Effects of Biomass Co-Firing and/or Oxy-fuel Coal Firing

Fireside corrosion testing is a complex process with many variables.  Testing at laboratory, pilot or full scale presents many difficulties.  Pilot scale testing has been found to offer advantages over laboratory or full scale plant based testing, although limitations still remain.  Pilot scale testing enables a wide range of variables to be examined with relatively good control of test parameters relative to full scale plant, whilst ensuring all combustion related parameters are examined, something that is often missing from simulated, laboratory scale work.  E.ON Engineering’s 1MWth Combustion Test Facility has been used to conduct fireside corrosion test work whilst firing a variety of coal and coal-biomass blends in air-fuel fired mode and coals with various sulphur and chlorine contents in oxy-fuel fired mode.  Metallographic examination has been used to accurately determine metal losses whilst scanning electron microscopy and x-ray elemental analysis has been used to characterise the corrosion damage.  The rates and types of corrosion produced are described for both the furnace wall and superheater / reheater areas of pulverised fuel fired boilers.  Both co-firing and oxy-fuel firing have the potential to increase, sometimes dramatically, fireside corrosion rates.