Promoting combustion of secondary fuel/coal mixtures
The BIO-FLAM project focused on the study of the combustion behaviour of clean fuels for power generation. More specifically, short cycle carbon containing fuels, known as secondary fuels, display unique thermodynamic properties that make them ideal candidates for replacing fossil fuels. However, there are still significant operational and environmental problems involved that may have a dramatic impact on the relevant combustion systems. The project provided a better understanding of the typical combustion behaviour of these fuels that would aid their promotion in power generation applications. Part of the project work involved the development of sampling equipment for secondary fuel/coal mixtures in power plants. The two water-cooled sampling probes of different lengths were extensively tested under full-scale co-combustion experiments at a Polish power plant. Depending on the tip design, one of the probes was able to provide deposit collection at certain surface temperatures and measurement of flue gas composition and temperature. Further minimisation possibilities of the probe, as far as diameter, weight and water supplying hoses are concerned would allow an easier operation at power plants. The new equipment may be used for conducting measurements and tests in combustion chambers of utility boilers. Apart from the probe, an optical fibre flame monitoring system has also been developed that relies on the analysis of flame pulsation parameters. Not only the addition of secondary fuel to coal may dramatically change the flame behaviour, but also properties, such as volatile content, reactivity and particle size distribution. The system can find useful applications in the area of characterisation of the ignition and combustion behaviour of different pulverised fuel mixtures. The system allows recording and processing of optical signals from the flame in order to provide measurement data for flame characterisation. Experimenting with various amounts of secondary fuel in coal, different flame parameters were derived and such data can be used as reference when investigating new mixtures of fuels. Furthermore, the data coming from measurements in a scaled down (0.5MWt) turbulent flame is also expected to contribute to the optimisation of pulverised fuel burners design.
