Corrosion of Boiler Materials - Effect of Co-Firing Biomass with Coal

Abstract:

In order to examine the corrosive effects of co-firing biomass with coal in existing subcritical and possible future (ultra) supercritical boilers, typical and potential boiler tube alloys have been exposed to simulated furnace wall and superheater/reheater environments in the 1MWTH pulverised coal fired Combustion Test Facility (CTF) at Power Technology. A total of four CTF runs have been completed, each of which were nominally of 50 hours duration. Up to 15 furnace wall and 16 superheater/reheater steel alloy specimens were exposed to a range of metal temperatures, with differing heat fluxes and gaseous environments, representative of pulverised coal combustion under low NO_x conditions with biomass additions. The biomass fuels were co-fired with Daw Mill coal, furnace wall corrosion specimens having previously been tested without biomass additions in this environment, providing base line corrosion data for comparison. Numerous previous tests with coals provided baseline data for superheater/reheater corrosion rates. Biomass was fired at both 20% and 10% on a thermal basis, representing proportions significantly above and close to the maximum proportions expected to be utilised in actual plant, enabling examination of concentration effects. The specimens were exposed to the combustion environment on air-cooled, precision metrology, corrosion probes.

When co-firing with wood at both 20% and 10% on a thermal basis, there was no discernable worsening of either furnace wall or superheater/reheater corrosion when compared with firing coal alone. Whilst there was no comparable data for TP316 austenitic stainless steel superheater/reheater specimens, the measured corrosion rates were substantially reduced when compared to the ferritic T22 specimens exposed at the same location.

1. Introduction
2. Experimental Program
3. Results
4. Discussion
5. Conclusions
6. Recommendations
7. References

Publication Year:

2004

Publisher:

Department of Trade and Industry

DOI:

No DOI minted

Author(s):

Davis, CJ & Pinder, LW