Plenty of steam is needed in the milk powder production process of sterilizing, concentrating and drying; therefore, a stable steam boiler has a direct impact on the milk production quality. Heilongjiang Feihe Dairy Industry Co., LTD., established in 1962, has won the Gold Award of Monde Selection. As hazy weather appears frequently in recent years, air quality issues have aroused great concern of the whole society. The Chinese government has successively launched "coal to gas" and other environmental policies to improve the air environment. Feihe Dairy is taking an active part in environmental protection, the company decided to replace the present 2 sets of 35 tph coal-fired steam boilers and one set of 20 tph coal-fired boiler with 3 sets of 35 tph gas-fired steam boilers. Considering that the steam boiler is a core equipment of the production line, the company had attached great importance to this purchase and held an open tender. ZOZEN successfully won the bid with excellent product quality and service, and provided the company with 3 sets of SZS series gas-fired steam boilers. This series of boiler adopts the design of membrane water wall; the gastight test must be done before installing thermal insulation layers, to ensure there is no flue gas leak under the condition of micro-positive pressure combustion and help reduce the heat loss of the boiler body. In addition, to effectively reduce the NOx emission, the boilers are equipped with large volume furnaces and advanced low NOx burners imported from Europe.