PURPOSE: To diffuse carbonaceous slurry uniformly into gas containing oxygen while atomizing by employing an operational burner having a structure including a central columnar gas flow containing oxygen, an annular slurry flow and a frusto-conical gas flow containing oxygen.

CONSTITUTION: A carbonaceous slurry supply pipe 14 is coupled with the upper end of a distributor 16 having a frusto-conical lower wall 19 and an annular slurry conduit 25 at the forward end constituting a pipe 28. The distributor 16 makes uniform a carbonaceous slurry flow front the conduit 25. A pipe 23 comprises a conduit 27 for passing gas containing oxygen and a part thereof enters from the open end of the pipe 23 and passes through a conduit 27. The remainder flows through an annular conduit 31 defined by the inner wall of the pipe 22 and the outer wall of the pipe 28. Annular carbonaceous flow exiting the conduit 25 for carbonaceous slurry intersects with a frusto-conical flow of gas containing oxygen immediately below the lowermost end of the pipes 28, 23 and then sheared and diffused uniformly into gas containing oxygen.