Improving The Efficiency Of Low-pressured
Industrial Boiler Systems Using Exergy Analysis
Author(s)
M. P. Maraj
Abstract
Much of the literature surrounding the exergetic evaluation of boilers has
focused primarily on large capacity and high-pressured systems, the majority of
which are found in power plants. In Trinidad and Tobago however,
approximately 76% of the boilers used are small low-pressured systems. This
paper looks specifically at evaluating the exergetic performance of one such lowpressured
boiler. The results of this evaluation confirm the large differences,
described in the literature, that exist between boiler first and second law
efficiencies and show that the combustion and heat transfer processes are
responsible for these low exergetic efficiencies by consuming approximately
70% of the fuel’s entering exergy.
The amount of excess air used for combustion significantly affects boiler
performance. During this study, it was found that most of these smaller boilers
were not equipped with excess air control devices and as such, excess air
amounts varied significantly and was often much higher than the recommended
15%. It was also found that for every 20% decrease in excess air, combustion
irreversibilities could be lowered by approximately 2–3%. Furthermore if the
boiler was operated with the recommended 15% excess air, simulation shows
that increasing the inlet combustion air temperatures using waste heat from the
boiler’s stack could lead to a 7% reduction in combustion irreversibilities. While
any improvement in boiler performance may have favourable consequences,
these results indicate that dramatic decreases in boiler irreversibilities cannot be
expected through air preheating and combustion control strategies and suggest
that designs which minimize combustion in boiler systems should be
investigated.
Keywords: boiler, combustion, heat transfer, exergy analysis, irreversibilities.
Keywords
boiler, combustion, heat transfer, exergy analysis, irreversibilities
Related Book
Other papers in this volume
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