DZL-type chain grate boiler,is a horizontal return fire tube hybrid three boilers,internal drum arranged in a bunch of screw pipe.Left and right sides of the furnace tubes with water-cooled wall. Achieved by light chain grate mechanical stokers,with blower,draft fan for mechanical ventilation and equipped with scraper slag tapping machine automatically.Around the arch of the furnace with new furnace energy-saving technology arch.Fuel from coal scuttle fell grate into the combustion chamber ,the flame passed through the body after the arch on both sides of refraction burn-up room to go off before the smoke box ,then turned back before the smoke chamber pot control,after the passage of smoke box into the economizer,and then by the induced draft fan pumping lead to the chimney through the flue to the atmosphere.