RU2253076C1 - Method of melting in gas cupola - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method comprises burning a gas fuel in the furnace. The gas fuel is made of hydrogen supplemented with carbon-containing agents such as gas hydrocarbons, liquid hydrocarbons or finely divided carbon in amounts of 2-19% of the hydrogen mass.

EFFECT: reduced power consumption and heightened temperature in the furnace.

1 dwg, 1 tbl, 1 ex

Description

The proposed method relates to metallurgy and can be used in foundry for melting materials for the production of castings.

A known method of melting in a gas cupola containing a water-cooled shaft with built-in gas burners and water-cooled beams, which are loaded with a refractory nozzle, consisting of refractory and heat-resistant materials (see USSR Author's Certificate No. 1610209, class F 27 B 1/08, B. I. No. 44, 1990).

The disadvantage of this method is that it does not allow melting of refractory charge materials, since when the temperature rises in the area of the refractory nozzle above 1650 ° C, deformation of the nozzle bodies is observed, they begin to melt and stick together, which leads to a decrease in the passage section of the shaft, making it difficult the combustion process and leads to a breakdown of the heat.

Of the known closest in technical essence is the "Method of melting metal in a gas cupola" (see USSR Author's Certificate No. 269947, class C 21 C; B 22 V, B.I. No. 16, 1970), according to which melting carried out in a gas cupola with ledges in the mine in such a way that natural gas is burned above the surface of the melt with an air flow coefficient α≈0.9-0.98. Above the burner tunnels, the composition of the gas phase in the overheating chamber is changed due to the supply of natural gas and α≈0.6-0.7, and in the melting zone α≈0.4-0.5.

However, this method does not allow creating a high temperature in the cupola, leading to an increased energy consumption, since a significant amount of heat is expended on the dissociation of methane.

The technical result of the proposed method is to reduce the energy intensity of the melting process, increasing the temperature in the furnace and the possibility of melting refractory materials.

The essence of the proposed method lies in the fact that the melting of the material, including burning gaseous fuel in the furnace, heating, melting and overheating of the material with combustion products, according to the invention is carried out in such a way that hydrogen is used as fuel, to which carbon-containing substances, for example gaseous, are added, liquid hydrocarbons or finely divided carbon in the form of crushed graphite, charcoal, thermoanthracite in an amount of 2-19% by weight of hydrogen.

This combination of new features with the known ones allows to reduce the energy consumption of the melting process, to increase the temperature in the furnace, which ensures the melting of refractory materials, since hydrogen has a higher calorific value and heat production compared to natural gas, the torch is shorter when burning hydrogen, and, therefore, the thermal stress is higher and no energy is expended on the dissociation of methane. Since hydrogen combustion products have low luminosity, it is necessary to have small carbon particles in the furnace atmosphere, which makes gas streams luminous and increases the heat transfer efficiency in the melt overheating zone and in the charge melting zone.

The proposed method of melting in a gas cupola is illustrated in the drawing, which shows a diagram of its implementation. The drawing shows: 1 - supporting part, 2 - cupola shaft, 3 - overheating chamber, 4 - gas burners, 5 - upper ledge, 6 - lower ledge, 7 - water cooling pipes, 8 - piggy bank. The lining is made of zirconium products having a fire resistance of 2500 ° C.

The method is as follows. In the gas burner 4 serves fuel - hydrogen and air as an oxidizing agent. In addition, to increase the luminosity of the products of the combustion of hydrogen, carbon-containing substances are supplied to the burning torch in an amount of 2-19% by weight of hydrogen, which increases the efficiency of heat transfer in the overheating chamber 3 and the cupola shaft 2. Overheating chamber 3, the shaft is heated for 20-30 minutes cupolas 2 and a piggy bank 8. Then, charge materials are loaded onto the lower ledge 6. Rising up, the illuminated products of hydrogen combustion heat and melt the mixture. The melt in the drip-jet mode flows from the lower ledge 6 into the overheating chamber 3, where it is additionally overheated in the bath formed on the bottom of the overheating chamber, and then enters the piggy bank. The use of hydrogen as fuel makes it possible to increase the temperature in the furnace and to ensure the melting of refractory charge materials.

The introduction of a carbon-containing substance in an amount of 2-19% by weight of hydrogen is due to the need to increase the efficiency of heat transfer by increasing the luminosity of hydrogen combustion products. If the amount of carbon-containing substance is less than 2%, the luminosity of the combustion products will not provide effective heat transfer, the productivity of the melting unit and the temperature of the melt are reduced. An increase in the amount of carbon-containing substance in excess of 19% does not lead to a further increase in heat transfer efficiency.

An example implementation of the method is as follows

The melts were carried out in an experimental gas cupola with water-cooled ledges in the mine. The fuel used was industrial hydrogen, which was burned in air. A carbon-containing substance in the form of finely dispersed carbon was introduced directly into the burning torch, the amount of which varied from 0.5 to 21% by weight of hydrogen.

After heating the lining of the cupola and the piggy bank, a charge containing cast iron and up to 65% of steel scrap was loaded. The consumption of hydrogen in all heats was kept constant. The melt refinement by chemical composition was carried out in an induction mixer. The results of swimming trunks are presented in the table.

Smelting conditions The temperature of the combustion products in the overheating chamber, ° C Melt temperature, ° С The consumption of carbon-containing substances,% by weight of hydrogen Furnace productivity, t / h Specific fuel consumption, kg / t Note The known method. Fuel-natural gas. 1700 1450 0 0.5 143.4 30% FeO formed in the melt The proposed method. 1900 1480 0.5 0.7 42.9 1900 1490 1,0 0.75 40,0 Fuel is hydrogen. 1900 1535 2.0 0.96 31.25 1900 1540 7.0 0.98 30.6 1900 1540 13.0 1,0 30,0 1900 1540 19.0 0.97 30.9 1870 1530 20,0 0.95 31.6 1850 1520 21.0 0.95 31.6

As can be seen from the table, the use of hydrogen as fuel allows melting of charge materials having a high melting point, and the addition of 2-19% of carbon-containing substances to the combustion products reduces the energy intensity of the melting process. The addition of less than 2% of carbon-containing substances to the high-temperature zone of the burning flame of hydrogen does not provide the necessary luminosity of the flame, the melt temperature decreases, the cupola productivity decreases, and the specific fuel consumption increases. When more than 19% of finely dispersed carbon is added to the combustion products, the melt temperature decreases, since a greater amount of heat is spent on heating particles of carbon, and the furnace productivity and specific fuel consumption do not change.

The proposed method provides a technical effect and can be carried out using means known in the art. The environmental situation is significantly improved due to a decrease in the content of carbon oxides in emissions from the cupola.

The proposed method of melting can be used in the melting of refractory non-metallic materials containing oxides of silicon, aluminum, magnesium, chromium, in the smelting of mineral raw materials (refractory natural minerals) to produce mineral wool in the building materials industry, cast refractory products, stone casting, moreover, the furnace design can be with water-cooled elements in the mine, with an external overheating chamber, with a single refractory ears.

Claims (1)

A method of melting a material, including burning gaseous fuel in a furnace, heating, melting and overheating the material with combustion products, characterized in that hydrogen is used as fuel, to which carbon-containing substances are added, for example, gaseous, liquid hydrocarbons or finely divided carbon in an amount of 2 ÷ 19% by mass of hydrogen.