DZL series package boilers are horizontal three-pass water & fire tube boilers with a chain grate stoker structure. Threaded pyrotechnic tubes are arranged in the drum to form a convection heating surface, while the drum and the water walls on both sides form a radiation heating surface in the furnace. Each package system is fully installed and wired before being transported to site and is electrically controlled to provide functions such as stepless speed regulation for the stoker, threshold parameter alert and interlock protection.