Directing against the problem of high NOx emission from 75 t/h coal-fired boiler used for cogeneration

its combustion system has been retrofitted by using WR dense and dilute pulverized coal burners and deeply air-stagging technology

i.e.combination of multi-layer axial air-stagging and radial air-stagging

the secondary air for burning is divided into two parts

namely 70%~85% and 10%~30%

and being sent into furnace

making the combustion in furnace to be partitioned into heat-releasing zone

oxygen-enriched zone

and poor oxygen zone

so as to decreased the formation of NOx.Results show that the concentration of NOx emission decreases more than 40% after retrofitting

but the unburnt carbon in fly ash and slag hasn't obvious change.