International Journal of Materials Engineering and Technology
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Abstract: One important
characteristic of the burning process in a CFB boiler is the char load, for
which we need to have a quantitative estimate. Direct measurement of char
inventory from the commercial-scale fluidized bed boiler is difficult and time
consuming due to sampling of solid material and chemical analysis in laboratory
and it cannot be used to monitor the char inventory online. A method to
determine char loading and its variation in fluidized bed combustion depending
on process conditions was developed and validated with the laboratory-scale
measurements. We found that the standard deviation of high-frequency
fluctuations of the concentration
signals correlates to the char load. Char inventory depends on char residence
time and reactivity which all are important parameters for process monitoring
and control. The developed method which is based on analysis of vibration of
flue gas oxygen concentration can be applied to combustion control system to
estimate fuel reactivity in existing process conditions. Fuel reactivity is an
important parameter in load changes, of CFB boilers. Especially, if feed forward
control is used during the load change the description of combustion dynamics
must be known. CFB boilers based on once-through steam cycle need feed forward
controls in order to meet the requirements of power network.
Keywords and phrases: CFBC, char inventory, online measurement.
