NOVELTY - The furnace has a perpendicular cylindrical shaped furnace main portion (1) that burns the coal cokes (C) deposited on the inside. A biomass combustion apparatus (3) burns a biomass solid fuel (B) in the height position of a side wall portion (5) corresponding to an overheating zone (11) of the furnace main portion. The biomass combustion apparatus supplies the biomass combustion heat to overheating zone of the furnace main portion.    USE - Melting furnace used for melting iron.    ADVANTAGE - Since the biomass combustion heat can be directly supplied to the height position of the overheating zone of furnace main portion, the biomass combustion heat can be used effectively for melting the to-be-melted raw material. Hence the quantity of the coal cokes thrown in from upper direction can be reduced. Since the consumption of coal cokes restrained and the fuel cost is reduced, the generation of greenhouse gas can be suppressed with the carbon-neutral property of biomass solid fuel.    DETAILED DESCRIPTION - The furnace has the biomass combustion apparatus which is equipped with a cylindrical burner main portion for accommodating the biomass solid fuel ranging from a longitudinal direction intermediate portion to a front-end portion (3A), while having a blower outlet in the front-end portion. A hot-air supply pipe (4) supplies the heating combustion air (H) for heating the biomass solid fuel in the cylindrical burner main portion, and continues combustion to the front-end portion vicinity of the intermediate portion of the cylindrical burner main portion. The biomass solid fuel consists of the short cylinder shaped or circular disc shaped biocoke that is heated to predetermined temperature and combined highly rigid, while compressing the plant-derived biomass feedstock by high voltage. The predetermined inclination-angle of the biomass combustion apparatus is set to 25-60 degrees . The arrangement height position of the biomass combustion apparatus is the same or more upward than the arrangement height position of a tuyere (6).    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of the melting furnace.    Furnace main portion (1)    Biomass combustion apparatus (3)    Front-end portion (3A)    Hot-air supply pipe (4)    Side wall portion (5)    Tuyere (6)    Overheating zone (11)    Biomass solid fuel (B)    Coal cokes (C)    Heating combustion air (H)