Abstract: The invention relates to a burner, particularly for the gasification of solid carbonaceous materials by partial combustion. The burner comprises a central channel (2) and at least one coaxial channel (6). The channels (2, 6) are defined by concentric walls (3, 5) having free downstream outer ends profiled to define an annular slit (10) forming a discharge end of the coaxial channel (6) and converging towards an adjacent discharge end of the central channel (2). The burner (1) is encased by a cooling jacket (14) and comprises a front face (21) with double walls spaced by one or more baffles (28) defining a coolant flow path operatively connected to the cooling jacket (14). The cooling jacket (14) has an upstream section (14A) and a transitional section (25) narrowing down to the front face (21) having a smaller outer diameter than the upstream cooling jacket section.