The application of pilot scale coal evaluation to full scale boilers
Date
2011-05-12
Authors
Rajoo, Priven
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Abstract
South Africa will continue to have a reliance on coal-fired power for the foreseeable future,
given that coal is abundant, inexpensive and available. As much of the country’s good quality
coal becomes depleted, the qualities available for power generation is fast declining.
Therefore, pilot scale tests will be crucial in the development of methodologies for predicting
coal performance in specific power plants. The main objective of this research is to validate
the coal combustion performance of the Pilot Scale Combustion Test Facility (PSCTF) against
four utility boilers to determine it’s scale up capabilities. Coal samples obtained from the
operating feeders during each utility boiler test were evaluated at the PSCTF under conditions
of similitude and at variations in excess air levels.
This dissertation details the comparison of pulverized fuel (pf) burnout and gaseous emissions
between the pilot facility and four coal-fired boilers of different configurations. The pilot furnace
was able to simulate the pf burnout for the three full-scale wall-fired and the tangentially fired
boilers at elevated excess air levels and under conditions of similitude respectively. The pilot
carbon monoxide (CO) and sulphur dioxide (SO2) emission results were simulated under
conditions similitude for all four boilers. The quantitative determination of the pulverized fuel
burnout, CO and SO2 was found to be dependant on the boiler configuration (boiler size,
burner type and burner arrangement) of the full-scale boiler which indicated the setup
conditions at the PSCTF. The pilot furnace produces higher flame temperatures than the utility
boilers which results in thermal NOx and inevitably significantly higher NOx emissions.
The results emanating from this research has shown that the PSCTF is an effective tool for the
evaluating and characterising coal combustion performance on a quantitative basis. Validation
of more boilers is required to increase the degree of confidence in the PSCTF results and
understanding the impact of the full-scale boiler configurations. All future validation tests
should incorporate other pf combustion aspects. A quantitative methodology for the NOx
emission should be further investigated.