PURPOSE: To suppress NOx concentration in a combustion exhaust gas and to increase a working efficiency by correcting a pattern of a predicted value of the NOx concentration in the residual period of the pattern set initially, on the basis of a difference from an average value of a measured value of the NOx concentration in a prescribed time before one period corresponding to the prescribed time.
CONSTITUTION: An average value Xg of a pattern Na of NOx concentration in the past (t) minutes from the time T4 to T5 is determined and an average value Xc of the pattern NA of the NOx concentration for (t) minutes between the times 6 and T7 of a combustion period X before one combustion period is determined. Then, a difference Xf between these average values Xg and Xc is calculated. This difference Xf is applied to addition-subtraction correction of basic predictive patterns NAG and NBG of the NOx concentration from the current time T5 on and thereby predicted values NAY and NBY of the NOx concentration from the current time T5 on are obtained. According to this constitution, it is possible to suppress the NOx concentration in a combustion exhaust gas to a prescribed value or below while minimizing an adverse effect thereof on operation.
SATO TAKAMI
OGATA YOSHIKUNI
