THERMODYNAMIC JUSTIFICATION OF OPPORTUNITY OF USING HIGH-TEMPERATURE COMBUSTION FLANKS FOR OXIDATION OF MELT IMPURITIES IN AGGREGATES OF CONVERTER TYPE. REPORT 1. THERMODYNAMIC ANALYSIS OF PROCESSES IN COMBUSTION FLAME WHEN USING NATURAL GAS

Increase in productivity and reduction of resource and energy capacity in steel production in converters predetermine development of technological measures and improvement of design of aggregates providing preheating of scrap and other charge materials, intensification of afterburning of waste gases in working space of steelmaking unit and redox processes in liquid bath while maintaining satisfactory durability of blowing devices and lining of the converter. Using fuel-oxygen combustion flames in converter process allows solving a number of multi-purpose technological problems. Combustion of fuel in working space of converter during formation of jet or use of submerged combustion flames significantly changes hydrodynamic pattern in reaction zones and liquid bath. Thermodynamic methods have been used to determine dynamics of combustion processes of gaseous fuels and oxidation of converter bath elements during their interaction with high-temperature flame combustion products. Calculation of the process of flame interaction with chemical elements of the bath was carried out for equilibrium conditions. It was established that use of combustion flames changes composition of gas phase in working space of converter, in which H₂ and H₂O are formed in addition to those traditionally present when oxygen is blown with O₂ , CO, and CO₂ . Presence of these gases changes thermal regime and oxidizing ability of the gas phase. When burning gas-oxygen fuel, optimal composition of initial gas mixture (natural gas + oxygen) should correspond to a ratio of 100  %  CH4   +  69  %  O₂ , while a vapor-gas phase containing 40  % of CO₂ and 60  % of H₂O is formed as a product of oxidation reactions. The total enthalpy of gas-oxygen fuel combustion at converter melting temperatures with oxygen excess ratio of more than 1.0 (up to 2.0) is approximately 200  kJ/mole of the initial reagents, with methane oxidation by carbon dioxide (–7) ÷ (–14.5) KJ/mole of initial reagents) at 1800  K and the process becomes endothermic at temperatures over 2000  K (ΔH₂₂₀₀ = (+7.7) ÷ (15.4) kJ/mole); with water vapor gas oxidation (ΔH_{1800  –  2200} = (+19.5) ÷ (+70) kJ/mole of the initial reagents. Therefore, only when the methane is oxidized with oxygen temperature of flame can be more than 1800 K. Use of carbon dioxide, water vapor as an air oxidizer does not give necessary thermal effect. 

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