Abstract
This paper presents the results of numerical computations for a large-scale OFz-425 CFB (circulating fluidized bed) boiler utilizing coal and syngas. Four different operating scenarios are considered, including the reference variant, corresponding to the conventional, mono-combustion of bituminous coal, and three tests involving replacement of secondary air and part of the coal stream with syngas fed by start-up burners. Pressure, gas velocity, temperature, and carbon dioxide distribution in the combustion chamber are discussed in the paper. The results indicate that the syngas supply leads to an increase in local temperature and carbon dioxide concentrations. The proposed concept is not advisable as it may lead to frequent emergency stops of the CFB boiler.
Highlights
The performance of engineering devices is degraded by the presence of irreversibilities, and entropy generation constitutes their measure [1]
Computations and validation of the model were successfully performed on data from an existing, large-scale, two-pass OFz-425 CFB boiler at 100% load, produced by RAFAKO S.A., Poland
All the discrepancies resulted from the simplifications in the defined hydrodynamic and reactions model
Summary
The performance of engineering devices is degraded by the presence of irreversibilities, and entropy generation constitutes their measure [1]. Various 3D-CFB models can be found in the literature [10,11,12,13,14,15], some of which consider the multi-fuel, CFB concept; the use of gaseous fuel, with a properly organized gas supply system, cannot be found in said literature. Such an idea may be beneficial for a power unit’s flexibility and provides the stable operation of a boiler furnace with a substantial demand reduction in its capacity
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