PURPOSE: To eliminate a delay in ignition of CWM and combustion at a low temperature and reduce non-combustion of fine powder coal contained in CWM by a method wherein two-fluid type liquid fuel such as CWM, etc., is injected and in this case a part of water within CWM is already evaporated.

CONSTITUTION: CWM is sent from a service tank to a heater acting as a reservoir tank, heated and pressurized and sent to a burner. CWM passes through a pressure feeding passage 22 of two-fluid type liquid fuel injector 31, enters a small diameter part of a through-pass hole 10, passes between a valve body 12 and a valve seat 11, is injected from a nozzle 18 toward a deep end of each of mixing chambers 7 and its pressure is reduced to the pressure within the mixing chambers 7. Heat energy is released through this pressure reduction and a part of water in the CWM is evaporated. Injection vapor is sent by a boiler through a vapor feeding passage 24, vapor passage 23 and 9, injected from a nozzle 8 into the mixing chambers 7, mixed with CWM and agitated and then CWM is atomized. Then, CWM is transported to the mixing chamber 6 where it is also atomized. Mixture is injected from an outlet injecting port 3 into a combustion chamber, its pressure is reduced to atmospheric pressure and further evaporated to speed-up ignition of fine powder coals.