Mechanism Modeling of SCR DeNOx System in Coal-Fired Units Based on Initial Ammonia Coverage Fraction Optimization
With large-scale integration of renewable energy generation into grid,the operating con-ditions of coal-fired units change rapidly,selective catalytic reduction(SCR)reactor inlet nitrogen oxides(NOx)concentration fluctuates dramatically.Traditional PID control can no longer meet the ultra-low emission standards for NOx,and it is necessary to establish an accurate model to predict the outlet NOx concentration in order to achieve fast and accurate ammonia injection control.How-ever,in the process of mechanism modeling,ammonia coverage fraction,a key data,is missing be-cause it cannot be measured,which affects model accuracy.To solve the problem of absence of NH3 coverage fraction,a method called initial ammonia coverage fraction optimization was proposed.Then the reaction constants and initial ammonia coverage fractions of the mechanism model were cal-ibrated by the coal-fired plant data with Improved Particle Swarm Optimization(IPSO)method.Results show that after initial ammonia coverage fraction optimization the performance of the mecha-nistic SCR model is obviously improved.Under typical conditions the average absolute percentage error of the test set is decreased by 17.1%.
coal-fired power plantNOxSCRIPSOinitial ammonia coverage frac-tions optimization