Observer design for the Selective Catalytic Reduction of NOx in a loop reactor

Abstract

The aim of this work is to show how to design a soft-sensor to monitor the Selective Catalytic Reduction (SCR) of NOx with NH3 in a loop reactor, i.e. a loop-shape system made of N units with periodical variation of the feed position. The design procedure of Zeitz (1977) is used and, even if the design procedure remains basically heuristic, some general guidelines to design the observer are given. The proposed observer is demonstrated to allow for a quick and reliable estimation of the inlet NOx concentration, as well as of the outlet reactants conversion and of the temperature profiles in the reactors, using some temperature measurements in the reactor, even when the NOx and the NH3 concentration in the feed change. The results may be used for control purposes, thus avoiding expensive hardware sensors and time consuming on-line measurements.

N2O decomposition over the circulating ashes from coal-fired CFB boilers

“…The dots represent the results by experiments, while the lines stand for the results by model prediction with Eq. (13). It can be seen that the model predictions and experimental results agree well.…”

“…Circulating ashes, the circulating bed materials in the CFB boilers, are generally with narrower size distribution, larger specific area and less carbon content than those bed materials only residing in the furnace and could be excellent catalyst to accelerate N 2 O decomposition [9][10][11]. Interacting with NH 3 , the circulating ash can even accelerate the destruction of NO and N 2 O at the same time, and thus it was suggested that NH 3 could be added at the cyclone entrance to reduce NO and N 2 O emission from CFB boilers [11][12][13]. Though the importance and effectiveness of the catalytic effect of circulating ash were recognized, the associated chemical kinetics has not been carefully studied.…”

Dynamics and control of loop reactors - a review

“…This model allows to derive stability conditions for the control scheme and suggest a control scheme for a realistic system with one sensor, at fixed position in lab coordinates, in each unit. Thus, the control should automatically adjusts V sw to assure its value within the range (13).…”

“…Other advanced approaches, such as the use of observers or soft sensors [10,13] for forced unsteady-state reactors, have been proposed to control a single traveling temperature wave.…”

Control of Rotating Wave Trains in a Loop Reactor

“…For this purpose, an algorithm, whose detailed description was not reported, was employed by the authors for the reconstruction of the temperature pattern. Other advanced approaches, such as the use of observers or soft sensors for forced unsteady-state reactors, have been proposed to control a single traveling temperature wave. − …”