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Title:
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Neuro-fuzzy control in a steam boiler at Hoogovens
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Author(s):
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Published by:
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Publication date:
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ECN
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1998
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ECN report number:
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Document type:
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ECN-I--98-009
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Other
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Number of pages:
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Full text:
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44
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Download PDF
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Abstract:
A neuro-fuzzy controller has been designed for a burner system in a gasfuelled steam boiler at Hoogovens Staal in IJmuiden, Netherlands. In
comparison to the existing conventional controller, the intelligent
controller will yield a tighter NOx emission control and enhance energy
efficiency. The controller maximises energy efficiency under the constraint
of a maximum NOx emission level, and was designed with a fuzzy network
structure. This structure makes optimal usage of the fruitful
cross-fertilisation of two advanced control techniques: fuzzy logic,
providing transparency and interpretability, and neural networks, providing
learning ability. The controller has been trained on real historic process
data to perform optinially. The underlying assumption is that the non-linear
static map generated by the neural network can adequately represent the
system's inverse dynamic behaviour in the ranges of interest. This design
procedure is less time-consuming and more cost-effective than the
conventional design method of analytic modelling, frequency response
analysis, and manual fine-tuning. In addition to these advantages in its
design phase, the neuro-fuzzy controller can show several important
advantages in its application phase. First, the costs of practical
implementation will be low since standard fuzzy logic controllers can be
used, and additional sensors are not needed. Second, the neuro-fuzzy
controller will show an excellent performance. This is due to its
non-linearity, which makes it very flexible: its performance is optimal under
a larger range of process conditions instead of only in one working point.
Also, the controller can detect sudden process perturbations, such as strong
load changes or large variations in fuel gas composition, and has learned how
to compensate for these accordingly before they would affect the NOx emission
level. The improved controllability of the NOx emission level allows the
steam boiler to be operated closer to its NOx emission constraint and thus
closer to its maximum efficiency. Moreover, energy efficiency will increase
by minimization of the electrical energy consumption of the recycle flow
ventilator. Furthermore, a tighter fuel/air ratio control and a more stable
boiler operation are expected. Superior performance over the existing
controller can be proven by on-line application. 25 refs.
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