This boiler adopts the water-cooling air distributor, under-bed oil gun ignition technology. Oil gun burns in the under-bed pre-combustion chamber firstly, and then it changes to be high-temperature flue gas (<800℃) by mixing with the cool air. After that, through the air chamber, it enters into the combustion chamber to heat the materials in it. At the initial period of ignition, boiler proper should be pre-heated, so that the smoke temperature could be relatively low, and later it could be raised gradually according to the temperature of material layer. Front oil pressure of oil gun is 2.0MPa, oil volume is 100~350Kg/h, light diesel (0#) oil is adopted. And the oil gun is of mechanical atomization.