In order to study the effects of low NO_x combustion retrofit on the atmosphere in main combustion zone of the boiler and on the coal ash fusion behavior

the compositions of flue gas in main combustion zone of two coalfired boilers after low NO_x combustion retrofit were tested and the flue gas composition distribution range was obtained. Then

an atmosphere-adjustable ash fusion test system was built up. The atmosphere of the ash fusion tests were prepared to simulate the combustion area flue gas atmosphere of the boilers studied. The results show that

after the low NO_x combustion retrofit

the volume fraction of CO in the main combustion area increased from 2%～3% to 7%～15%

the combustion atmosphere changed from weak reducing atmosphere to strong reducing atmosphere

and the ash fusion point decreased obviously.