Environmental Engineering Reference
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Open Closed
Burner A fuel changeover valve
Open Closed
Burner A fuel-air changeover valve
Closed Open
Burner A exhaust gas changeover valve
Closed
Open
Burner B fuel changeover valve
Closed
Open
Burner B fuel-air changeover valve
Open
Closed
Burner B exhaust gas changeover valve
Return to preceding aperture
Fuel flow regulative valve
Control operation resumed
Preceding aperture-
Control operation resumed
Combustion air flow regulative valve
Preceding aperture-
Control operation resumed
Exhaust gas flow regulative valve
Preceding aperture-
FIGURE 5.51 Concept of operating sequences of changeover valves and flow regulative
valves. (From Hida, A., Nippon Steel Corp. Tech. J. , 363:49, 1997. With permission.)
5.3.2
S IGNAL P ROCESSING M ETHOD
The basic signal processing method is in accordance with the study made by
Yamatake-Honeywell Co., Ltd. It is described below. In a conventional continuous
control method, feedback control is employed with measured signals. However, for
regenerative combustion, modifications must be made to the signal processing
method. The following three processing methods are available:
1.
The controlled variables, such as fuel/airflow rate, temperature of pre-
heated air, and so on, are fixed until the flow rate or pressure becomes
stable from the moment of fuel cutoff.
2.
Intermittent control is executed with a cycle excluding the fuel cutoff
timing.
3.
Measurement signals are compensated for with the effects of transient
response and used for continuous control.
The first method is applied in an ignition sequence for an example and is the
most typical control method under these circumstances. It provides stable perfor-
mances with a high controllability on condition that tuning for the fixed period and
bumping at the beginning of control are observed carefully. One drawback of this
method is that responsiveness cannot be increased when the output is fixed for long
periods depending on the changeover cycle or fuel cutoff duration. In the case of
 
 
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