In situ Determination of Fuel Particle Reaction Rates by Simultaneous Measurement of Particle Temperature and Size

摘要

The most widespread example of gas-solids reactions in practice is the combustion of solid fossil fuels for power and/or heat production. One possibility of efficiency enhancement provide combined gas and steam turbine processes with pressurized combustion, as have been applied in the recent decades in power generation from liquid energy sources. The exploitation of this potential concerning solid fossil fuels is the subject of research and development worldwide. In this context, the mechanism of the char burning under elevated pressure has so far been scarcely studied. Yet this mechanism is the determinating factor of the attainable reaction rates and the necessary particle residence times that hence are the parameters for the plant size of such a pressurized furnace. In conventional atmospheric power plants, the reaction rate of particle combustion plays an important part, too. The highest possible particle burnout degree on the one hand provides that a high thermal efficiency is attained and on the other hand determines the quality of the ash as a byproduct. For the current practice of using the obtained power plant ash as aggregate in the cement industry, a loss at red heat of 5% by weight must not be exceeded. The present report describes investigations examining the combustion behavior of char particles under conditions of high temperature and pressure by means of in situ determination of the reaction rates. On the basis of the two possible reaction paths - i.e., primary oxidation of carbon into carbon monoxide or carbon dioxide, respectively - a comparison is made between the measured reaction rates and the theoretical maxima.