ZOZEN SZS series oil-fired/gas-fired boiler proper adopts the D-type structure. One side is the furnace, and the other side is the convection heating surface. The partition walls around the furnace body, the partition wall between furnace and convection section, and the front and rear walls all adopt the membrane wall structure. There are foreign advanced burner, economizer and condenser installed at the end of flue gas duct, which can lower the exhaust gas temperature to 60℃, achieve the thermal efficiency of over 98% and control the emission of NOx to less than 30mg/Nm3. This kind of boiler has the characteristics of energy saving and environmental protection, safety and efficiency, simple operation and maintenance, and fully automatic control system which can realize unattended operation.