NATURAL GAS ECONOMY IN THE PROCESS OF AIR HEATING IN THE HOT -BLAST STOVES

Abstract

On the Ukrainian metallurgical enterprises blast furnaces work with the temperature of heating of blowing 1050-1180 °C, simultaneously a temperature under the dome of air-heater is 1250-1350 °С. Air-heaters heat, by both domain gas and naturally-domain mixture with the warmth of combustion 3,9-4,5 Mj/m 3 and maintenance of natural gas in mixture 1,5-3 %. research of thermal work of block of air-heaters, attendant a high furnace by volume of 1386 m 3 is executed. Applying the mathematical modelling, the study of the hotblast stoves, which are heated by a mixture of natural and blast-furnace gases, was carried out, and the basic parameters of the hot-blast stoves operation were determined. Mathematical model allows on the known structural parameters of air-heater and its attachment, composition of fuel and terms of its incineration, on the given expense of blowing, to determine the temperature of heating of blowing, gas expense, air of burning expense and smoke gases expense, temperature of smoke gases and attachment on it height in the period of heating, and also change of temperature of blowing on the height of attachment in the period of blowing. It is shown that the saving of natural gas can be achieved by changing the fuel mixture to the blast furnace gas. For ensuring the required temperature of the air blast when the hot-blast stoves are heated by the blast furnace gas, two variants of their operation were considered: 1) the enrichment of combustion air with technological oxygen; 2) preheating the combustion components (fuel and atmospheric air) before burning. It was found that the first variant can be implemented by enriching the combustion air with the process oxygen up to 26 % and increasing the consumption of the blast furnace gas by 32 %, but these lead to increasing of the specific costs of the air heating by 21 %. The implementation of the second variant can be ensured by heating of the combustion components to 150 °C and increasing the consumption of the blast furnace gas by 20 %. However, these lead to reducing of the specific costs of the air heating by 6.6 % and make the second variant is cost-effective.