The retrofit of a conventional 200 MW unit with HG-670/13.7-HM18 type lignite boiler involving tiny-oil technology is discussed.The burner is equipped with a fan-mill pulverizing system in which the high-temperature flue gas is used as the desiccant.Some features of the existing lignite boiler against the application of tiny-oil technology are realized such as large flow rate of the fan-mill

low concentration of the pulverized coal during cold-starting of the boiler

large size of the primary nozzles

as well as the hexagonal arrangement of the burner.These concerns are successfully addressed by employing a duo-oil-gun arrangement in the combustor and an oil-gun heater in the flue duct.Experimental results of cold-starting of the retrofitted boiler show that

pulverized coal is able to be stably ignited and combusted within the feeding range of 2~12 t/h.Both the steam temperature and pressure rising rates satisfy the requirements of the operation rules.By applying the tiny-oil technology

an oil-saving rate of 76% is achieved.