ZOZEN WNS series oil-fired/gas-fired boiler is a kind of fire tube wetback boiler with a two-pass or three-pass structure. It is equipped with foreign advanced burner, economizer and condenser installed at the end of flue gas duct to lower the exhaust temperature to 60℃, achieve the thermal efficiency of over 98% and control the emission of NOx to less than 30mg/Nm3. It has the characteristics of compact structure, small covering area, short installation period, easy operation and complete automatic control system which can realize unattended operation.