This boiler is a single furnace in line, vhain travling grate, water tube, semipackaged steam boiler. The boiler is designed with symmetric heating surface, firm structure and sound water circulating system. Large water content and steam space ensures low water level fluctuation and high quality steam. The unique design of the furnace and flue gas flowing method through the heat transfer area ensures minimum level exchange heat loss. Therefore, this boiler has good coal adaptabillity and high efficiency. It is convenient to install and is suitable for the application to produce steam for the manufacturing process.