Recently, ZOZEN took a field trip at the project location of the WNS boiler. The ZOZEN WNS series gas-fired steam boilers are horizontal wetback fire-tube boilers which have reasonable internal structure. An advanced low NOx burner is equipped with the boiler to reduce the NOx emission to less than 30mg/Nm3. At the same time, the burner can realize automatic air adjustment, which can ensure the sufficient fuel combustion.