The LIBS System’s Software Component
An advisory software named LIBS Online Slagging Advisor (LOSA) was also developed to demonstrate the merit of a concept where LIBS-derived data would be fed to online software to provide real-time predictions of ash fusion temperatures and indications of the slagging potential of power operations, when ash fusion temperatures (AFT) deviate from target furnace exit gas temperature (FEGT) levels.
The main components of LOSA are: a LIBS-based laser system used to measure the slagging-related coal properties in-situ and in real time, live plant data available through the plant data network, a model based on the artificial neural network for prediction of ash fusion temperatures, and the software interface (Figure 4).
4. Artificial intelligence leads to real results. The custom-designed LIBS Online Slagging Advisor software contains artificial neural network models that estimate ash fusion temperatures and provide valuable information about coal slagging potential. Courtesy: Energy Research Center, Lehigh University
The use of such software will allow boiler operators to better coordinate coal yard operations and adjust boiler control settings to mitigate the impact of slagging on boiler operation. Test experience with different boilers burning coals with a range of compositions has demonstrated that boiler control settings can be manipulated to influence slagging in coal-fired boilers. According to results from prior testing, the key is to maintain FEGTs below the coal ash fusion temperature to minimize the adverse impact of ash conditions on upper furnace slagging.
The unit parameters available for slagging control include excess oxygen (O2), mill classifier speed, vertical coal loading, overfire (OFA) register opening, and others. From parametric testing performed at Brayton Point Unit 3 in this project, it was found that increases in excess O2, opening of the OFA registers, and reduction of the classifier help to reduce FEGT. This information is provided by the software when a prescribed target value for FEGT deviates from the estimated AFT.
"Our results have been very positive," said ER Co.’s Caparo. "LIBS analyzes coal composition accurately and with good repeatability. It also predicts ash-fusion temperature accurately, with results that compare very favorably with the results obtained using the ASTM standards."
Next Steps
The Brayton Point project demonstrated the merit of the LIBS system that produces coal elemental analysis and estimated fusion temperatures. However, further development is needed to equip a LIBS system with an automatic online coal-sampling attachment and to achieve higher accuracy and repeatability, according to Romero.
The researchers have been awarded a second DOE grant to fund development of a commercial prototype of the LIBS system. They hope this next phase will move quickly so the LIBS technology will be available to power plant personnel in the near future.
--Angela Neville, JD is POWER's senior editor.
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