Patent EP-2284130-A1 (EP)
Inventor: NIEHOFF THOMAS
IPC: C03B5/12
Filed: 2009-07-07
Abstract: The method comprises melting a mineral base material in a cupola furnace, which has a shaft (11) to hold the base material, where a lower section of the shaft is provided with a grate and a combustion chamber (2) is disposed beneath the grate and provided with an outlet for removal of the molten base material, heating the combustion chamber by burners, supplying the burner or burners with liquid or gaseous fuel, converting the fuel with an oxygen-containing gas, and regulating the quantity and oxygen content of the oxygen-containing gas according to a parameter of the melting process. The method comprises melting a mineral base material in a cupola furnace, which has a shaft (11) to hold the base material, where a lower section of the shaft is provided with a grate and a combustion chamber (2) is disposed beneath the grate and provided with an outlet for removal of the molten base material, heating the combustion chamber by burners, supplying the burner or burners with liquid or gaseous fuel, converting the fuel with an oxygen-containing gas, and regulating the quantity and oxygen content of the oxygen-containing gas according to a parameter of the melting process selected from flue gas temperature, flue gas composition, temperature of the mineral base material to be melted or flame intensity. The oxygen-containing gas is supplied to the cupola furnace during the heating phase when none of the molten base material is removed through the outlet, where the oxygen-containing gas contains a smaller proportion of oxygen than oxygen-containing gas supplied to the cupola furnace during the melting phase, in which the molten base material is removed through the outlet. The oxygen-containing gas is supplied to the burner or burners during the heating phase, where the oxygen-containing gas contains a smaller proportion of oxygen than oxygen-containing gas supplied to the burner or burners during the melting phase. The burners are operated during the heating phase with the oxygen-containing gas having oxygen proportion of less than 21-30%, and are operated during the melting phase with the oxygen-containing gas having oxygen proportion greater of than 30%. The burners are operated such that a length of flames occurring during combustion of the fuel with the oxygen-containing gas is 65-95% of diameter of the combustion chamber. The cupola furnace is operated with a proportion of coke in the fuel of less than 20% supplied to the cupola furnace in a coke-free manner. The fuel is selected from oil and natural gas. The combustion chamber is heated with three to five burners, which are disposed in side walls of the combustion chamber. The flames of the burner are inclined at an angle of 8-12[deg] relative to the horizontal. The projections of a central axis of the burner and the combustion chamber diameter extending through a burner outlet produce an angle of 5-15[deg] on a horizontal plane. The combustion chamber is provided with a lance. The burners are operated under sub-stoichiometric conditions. The oxygen-containing gas such oxygen-enriched air or technically pure oxygen is supplied to the combustion chamber via the lance, where 5-20% of the total amount of oxygen-containing gas is supplied to the combustion chamber via the lance. The projections of a central axis of the lance and the combustion chamber diameter extending through a lance outlet produce an angle of 16-24[deg] on the horizontal plane. The oxygen-containing gas flows from the lance at a speed of 100-200 m/s. The temperature of the flue gas leaving the cupola furnace is measured and the amount and oxygen content of the oxygen-containing gas are set, so that the flue gas temperature arises at 100-140[deg] C.