Transactions of the Society of Instrument and Control Engineers
Online ISSN : 1883-8189
Print ISSN : 0453-4654
ISSN-L : 0453-4654
Application of Optimal Periodic Control Theory to Catalytic Denitrification Control of Refuse Incinerator Plant
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1986 Volume 22 Issue 9 Pages 942-947


Aiming to reduce consumption amount of ammonia (NH3), which is blown into the catalytic denitrification process of the refuse incinerator plant, application of the periodic control method has been studied.
Through a step response examination in an actual plant, remarkable process dynamic characteristics have been observed: namely, that time-constant (Tu) of blowing in NH3 is smaller than (Td) of blowing off.
Applying the optimal periodic control theory to the process, the following analytical results are obtained: (i) Optimal bang-bang type periodic control of NH3 blowing is more effective in reducing NH3 consumption than optimal continuous steady state control, and (ii) The NH3 consumption reduction rate depends on the Td/Tu ratio and the ζ parameter (ζ=aimed denitrification rate/process capable denitrification rate)
Because the theoretical solution of the optimal control period is approximately zero, a practical finite periodic control has been examined on an actual catalytic denitrification process. Results of the examination have shown that the NH3 reduction level is acceptable but lower than the theoretical value.
In actual plants, because of wide fluctuation of nitrogenoxide (NOx) generation, simple periodic control cannot maintain exhaust NOx concentration under the required NOx concentration for a long time. The periodic control with feedback correction of control timing has been proposed and demonstrated to be effective by simulation.

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