RU2333437C1 - Method of melting in cupola furnace - Google Patents

Abstract

FIELD: chemistry, metal melting.

SUBSTANCE: invention concerns ferric metallurgy, particularly melting. The method involves burning fuel, heating and melting material by fuel combustion products charged to the shaft. Fuel combustion products are transferred to the heated material at alternating feed rate within 2-60% of average feed rate with alternation frequency of 3-120 changes per minute. Fuel combustion product feed rate changes being less, the higher is feed rate alternation frequency in time.

EFFECT: increased cupola furnace productivity and temperature of obtained liquid material.

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Description

The proposed method relates to metallurgy and can be used in foundry for melting material in a cupola.

There is a known method of smelting cast iron in a cupola, according to which solid fuel is loaded into the mine — coke, kindle coke, create a blank spike, blow it with air, bring the temperature in a blank spike to 1700 ° C and higher, load the mixture onto a heated blank spike, feed it into tuyeres air up to 1000 m ³ under normal conditions, based on the production of 1 ton of molten cast iron with a stable, constant supply of air for fuel combustion, smelted cast iron, released from a cupola and used to fill molds. With this smelting method, the products of combustion of fuel are formed in direct proportion to the amount of blown air, and the products of combustion move in the mine between pieces of charge along the path of least resistance mainly at the walls of the mine (Ladyzhensky B.N., Oreshkin V.D., Sukharuk Yu.S. Liteinoe production.Edited by Ph.D. V.D.Oreshkin. - M. - Sverdlovsk, 1953, pp. 92-97; Levy L.I., Marienbach L.M. Fundamentals of the theory of metallurgical processes and casting technology alloys. - M.: Mechanical Engineering, 1970, pp. 171-182; Foundry. Edited by I. B. Kumanin . - M.: Mechanical Engineering, 1971, pp. 226-234; Barinov N.A. Water-cooled cupolas and their metallurgical capabilities. - M.: Mechanical Engineering, 1964, pp. 22-38.). The disadvantage of this method is the inefficient use of heat from the products of fuel combustion, the predominant movement of gases at the walls of the mine, the melting of the refractory lining of the mine, the need for water cooling of the mine, which leads to an increase in heat loss and a decrease in the thermal efficiency of the melting unit.

Known methods of melting material in coke oven and gas cupolas with the optimal shape of a mine of a blast furnace type (Grachev V.A., Cherny A.A. Modern methods of cast iron melting. - Saratov: Volga Book Publishing House, 1973, pp. 26-31; Experience in cast iron melting in a gas cupola / E. D. Sosnovsky, N. A. Gorelov, V. N. Morgunov, V. P. Guskov // Foundry, 1996, No. 5, pp. 9-10; Cherny A. A. Gas cupola USSR Author's Certificate No. 873739, Cl. ³ F27B 1/08). In these cupolas, changing the shape of the shaft from a cylindrical to a more complex one, such as a blast furnace, improves the distribution of hot combustion products over the sections of the shaft, makes the movement of hot gases more uniform, improves the performance of the melting units, but the efficiency of these units decreases with increasing diameter of the shaft.

The technical result of the proposed method is to achieve multiple redistribution of hot gases in the cupola mine, to intensify the turbulization of gas flows in the layers of the heated material, to improve the heat transfer from the hot gases to the charge, to reduce heat losses, to increase the cupola productivity, to increase the temperature of the resulting liquid material, to save fuel, and to increase the thermal coefficient the usefulness of the thermal unit.

The essence of the proposed method of melting material in a cupola is that they burn fuel, heat and melt the material coming into the mine combustion products, but unlike the known methods, the combustion products of the fuel are fed to the heated material alternately, increasing or decreasing the flow rate within 2 -60 percent of the average flow rate with a frequency of change of this flow rate of 3-120 vibrations per minute, and the smaller the change in the flow rate of combustion products, the greater the frequency of fluctuations in the flow rate of these products during time.

This combination of new features with the known ones allows achieving multiple redistribution of hot gases in the cupola mine, intensifying the turbulization of gas flows in the layers of the heated material, improving heat transfer from hot gases to the charge, reducing heat losses, increasing thermal efficiency (efficiency), increasing the performance of the heat unit, reduce fuel consumption by 1 ton of the resulting liquid material.

The method is as follows. The combustion products of the fuel heat the materials (pieces) of the blank ears in the shaft furnace, gradually increasing the temperature to 1650-1700 ° C. Then load the mixture, set the average consumption of combustion products, based on the required performance of the melting unit. After stabilization of the melting process and the release of liquid material with the required temperature, the combustion products are fed to the heated material in the mine alternately, then increasing or decreasing the flow rate R within 2-60 percent of the average flow rate with a frequency N of variation of this flow rate of 3-120 vibrations per minute . The smaller the magnitude of the change in the consumption of combustion products, the greater the frequency of fluctuations in the consumption of these products over time. The consumption of combustion products is determined by the flow rate of air supplied to the combustion of fuel. With changes in the consumption of combustion products and other identical conditions, the depth of penetration of gas jets in the mine changes, gas flows are redistributed, hot gases near the heated material are turbulized, heat transfer is intensified, and the melting process is economical. At R <2, turbulization in the charge layers sharply decreases, and at R> 60, the processes of afterburning of gases are disturbed. At N <3, there is no improvement in heat transfer processes, and at N> 120, intense vibration of the thermal unit occurs. The optimal values are in the range 2≤R≤60, 3≤N≤120. When cast iron is melted in coke cupola furnaces, a change in the value of R, N to the optimum limits leads to an increase in the productivity of the melting unit, a decrease in fuel consumption, an increase in thermal efficiency, and when melting in gas cupolas, a decrease in the consumption of natural gas, an increase in efficiency, and a decrease in the waste of elements in cast iron are achieved.

Since the flow rate of the combustion products is directly proportional to the flow rate of the air supplied to the combustion of fuel, the flow rate of air is subject to changes by automatic regulation. When using solid fuel in cupolas, the oxygen supplied to the idle air oxidizes carbon, predominantly hot carbon oxides are formed, the nitrogen supplied with the air is heated, and these hot gaseous products, washing the charge loaded into the mine, heat, melt and overheat the material. A change in these costs leads to a change in the depth of penetration of hot gases in the idler, the redistribution of flows in the mine, the intensification of heat transfer. The same thing happens in a gas cupola with a single ears. But during gas melting of a material, the fuel is mainly gaseous hydrocarbons (natural gas), and to achieve a positive effect with changes in air flow rates, it is necessary to change the flow rate of combustible gas, maintaining the optimal value of the air flow rate, while in direct proportion to the flow rates of air and gas, the flow rates of combustion products change passing through a single head and layers of the charge in the mine.

The effectiveness of the proposed method increases with increasing diameters of the mine cupola shaft, since in such cupola furnaces hot gases penetrate deeper into the bulk materials, more washing is washed off with hot combustion products.

The tests were carried out during the casting of cast iron in a universal cupola with a blast furnace. This cupola could run on solid or gaseous fuels.

An example implementation of the method.

Cast iron was melted in a cupola, the productivity of which was maintained under normal conditions of the production process of 7 tons of molten iron per hour. The average air consumption in coke and gas versions of the cupola was 7000 m ³ per hour, calculated on normal conditions. During gas melting of cast iron, the average consumption of natural gas was 700 m ³ / h for normal conditions. The experiments were carried out with values of 1.7≤R≤62, 2.7≤N≤123.

The results are shown in the table. In the table, when applying the proposed method in comparison with the known method, Q is the increase in cupola productivity, times; ΔT is the temperature increase of the obtained molten iron, deg .; G - fuel economy per 1 ton of molten iron obtained,%; D - increase the thermal efficiency of the cupola, times.

Table R factors; N The performance of the smelting process of cast iron by the proposed method in comparison with the known Solid fuel smelting Gaseous fuel smelting Q times ΔТ, deg G% D times Q times ΔТ, deg G% D times R is 2; N = 3 1,025 10 1,04 1,02 1,03 fifteen 1,035 1,025 R is 2; N = 60 1,1 fifteen 1.06 1,07 1.09 twenty 1,1 1.09 R is 2; N = 120 1.15 twenty 1,07 1,1 1.13 25 1.15 1,11 R = 30; N = 3 1.21 25 1.09 1,2 1.25 25 1.3 1.21 R = 30; N = 60 1.25 thirty 1.15 1.25 1.27 35 1.32 1.27 R = 30; N = 120 1.17 twenty 1.14 1,07 1.18 twenty 1.25 1.09 R = 60; N = 3 1.28 25 1.16 1.27 1.29 35 1.33 1.28 R = 60; N = 60 1,11 twenty 1,08 1.12 1,1 25 1,11 1,11 R = 60; N = 120 1,02 10 1.05 1,03 1,04 10 1.05 1,04 R = 1.7; N = 2.7 economic efficiency is not achieved, indicators are the same as when applying the known method R = 1.7; N = 123 cost-effectiveness is not achieved, there is a vibration of the cupola cup R = 62; N = 2.7 economic efficiency is not achieved, indicators are not increasing sharply R = 62; N = 123 cost-effectiveness is not achieved, there is a vibration of the cupola cup

In the optimal range of values 2≤R≤60; 3≤N≤120 efficiency is achieved, since when casting iron in a cupola with solid fuel Q = 1,02-1,28; ΔT = 10-30; G = 1.04-1.15; D = 1.02-1.27, and when melting on gaseous fuel, Q = 1.03-1.29; ΔT = 10-35; G = 1.035-1.33; D = 1,025-1,28, that is, higher than with the known melting method. Rationally increase N as R decreases.

When using the proposed method, metal losses due to oxidation are reduced, the processes of fuel combustion and afterburning of combustible components of the combustion products are accelerated, and freezing of the charge in the cupola shaft is eliminated.

The proposed method provides a technical effect and can be carried out using means known in the art, it can be used not only in foundry, but also in heating, firing, and smelting metal and nonmetallic materials in shaft furnaces of the metallurgical industry and the construction industry.

Claims (1)

A method of melting material in a cupola, including burning fuel, heating and melting material entering the mine with fuel combustion products, characterized in that the fuel combustion products are supplied to the heated material with alternating increase and decrease in flow rate within 2-60% of the average value with a frequency of change a flow rate of 3-120 vibrations per minute, and a smaller change in the flow rate of the combustion products of the fuel corresponds to a greater frequency of fluctuations in the flow rate of these products.