RU2412413C1 - Procedure for melting iron in cupola - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure consists in loading charge into shaft of gas cupola, in combustion of fuel, in heating and in charge melting. Fuel is combusted at coefficient of air consumption 0.7-0.9. Further, 0.5-0.8 of shaft volume is filled with charge. Air is supplied with peripheral and radial jets into shaft not filled with charge at velocity 1.5-7 of velocity of gas motion in shaft in outlet cross sections of nozzles and at frequency of alternate air supply with peripheral jets and radial jets at 15-60 periods per minute. Hot gas is mixed with air in vortex; ratio of air consumption in the shaft not filled with charge is increased to 1.01-1.5, combustible components are after-burned, temperature is raised to 700-1200°C and hot gases are supplied into a heat-exchanging device or infiltrated through charge.

EFFECT: fuel saving, raised output and thermal efficiency of cupola.

4 cl, 1 ex

Description

The proposed method relates to metallurgy and can be used in foundry for smelting cast iron in gas cupolas.

A known method of melting cast iron in a cupola, including burning solid fuel (coke) in a single drum, heating and melting a metal charge with hot combustion products in a mine, differs from the known method of melting in conventional cupolas in that the combustion products are selected (sucked) below the threshold of the loading window are fed into a stand-alone chamber for gas afterburning, where they are mixed with air introduced through the tube, burned, supplied to a stand-alone recuperator, partially give off heat to the recuperator air, and then through a smoke exhaust and a pipe are removed to the atmosphere. Hot air from the recuperator is piped to the cupola lances (Kuzelyov M.Ya., Skvortsov A.A., Smelyakov N.N. Handbook of a foundry worker. Second ed., Revised and revised. - M.-Sverdlovsk: Mashgiz, 1956, p. 376, Fig. 140). This method of melting in a cupola is complex and ineffective. Cupola installation takes up a lot of production space. Large heat losses are observed, explosions are possible in the gas afterburner, the afterburner and the recuperator are clogged with dust, which is difficult to remove. The efficiency of the recuperator decreases as its passages become clogged with cupola dust, air enters the cupola for burning coke with a temperature of 315 ° C, which is not enough to increase the cupola productivity and reduce fuel consumption for melting. The same disadvantages are observed with the known methods of melting in closed cupola furnaces of the Giprostanok design (Iron Casting Manual. / Ed. By Dr. N.G. Girshovich. - 3rd ed. Revised and supplemented - L. : Mechanical Engineering, Leningrad Branch, 1978, pp. 163-170, Fig. 11.5, 11.6). Common disadvantages of the melting methods in these cupolas are the insufficient reliability of devices and processes, the possibility of air suction and the formation of an explosive mixture in the gas cleaning system due to the presence of a high vacuum in it, the need to install backup smoke exhausters, and provide increased control over the tightness of the gas path and the state of the safety valves. The cupola complex is a complex, unreliable unit, its thermal efficiency is low, for afterburning cupola gases it is necessary not only to blow air, but also additionally supply gaseous or liquid fuel to the chamber afterburning cupola gases.

A known method of smelting cast iron in a coke oven gas cupola, in which the selection of gases is carried out below the loading window (Handbook of a caster. Iron casting. / Under the general editorship of Prof. NN Rubtsov. - M .: Mashgiz, 1961, p. .326, fig. 158). This method is also ineffective, expensive, thermal efficiency of the cupola is low.

Closest to the technical nature of the claimed is a method of melting cast iron in a gas cupola, including loading a metal charge, flux, supply of heated blast, characterized in that the blast with a temperature of 450-550 ° C serves for 75-83% of the melting time, in the remaining time reduce the temperature of the blast and the melting is completed at a blast temperature of 150-200 ° C (USSR Author's Certificate No. 2092569 "Method for smelting cast iron in a cupola", authors Grachev VA, Kuryaev VI, Gorelov NA, Kodanev V .N., Cl. 6 C21C 1/08, Application No. 95109586/02. Prior. 07.06.95. Applicant - Penz nsky State Technical University. Bull. №28, publ. 10.10.97). When using this method, the air is heated in a freestanding heater, spending additional fuel. At a higher air blast temperature (450-550 ° C), a higher temperature of the liquid metal is achieved, which allows thin-walled castings to be obtained, and at a lower air temperature (150-200 ° C) thick-walled castings are obtained.

The disadvantages of this method are the consumption of additional fuel in a freestanding air distributor, cupola gases are not burned up, the heat of the gases leaving the cupola is not used, the thermal efficiency of the cupola is not high, you cannot use a large amount of steel in the charge, there are significant metal losses during melting due to oxidation, it is difficult to regulate the cupola productivity and the metallurgical process of metal smelting.

The technical result of the proposed method consists in saving fuel for the smelting process, increasing productivity and thermal efficiency of the cupola, the possibility of heating the air blast and charge by using the heat of the burned cupola gases, in reducing metal losses due to oxidation, increasing the amount of steel in the charge, temperature and fluidity metal, reducing the marriage of the obtained castings.

The specified technical result is achieved by the fact that the proposed method of smelting cast iron in a gas cupola, including loading the charge into the mine, burning fuel, heating and melting the mixture with fuel combustion products, differs from the known one in that the fuel is burned at an air flow rate of 0.7-0 , 9, fill the mine with a charge of 0.5–0.8 of the mine’s volume and supply air to the unfilled mine with peripheral and radial jets at a speed in the outlet sections of nozzles of 1.5–7 the gas velocity in the mine and the frequency of changing the air supply with peripheral jets to feed radial jets of 15-60 periods per minute, create vortex mixing of hot gases with air, increase the air flow coefficient in an unfilled charge shaft to 1.01-1.5, burn down combustible components, increase the temperature of gases to 700-1200 ° C and supply hot gases to a heat exchanger for heating air or pass through a charge; The method is also characterized in that the hot gases are supplied to the recuperator and the air is heated, which is introduced into the burners of the cupola for burning fuel; The method differs in that hot gases are passed through the charge before it is loaded into the mine, the charge is heated, and then the heated charge is loaded into the mine and melted; The method differs in that hot gases are passed through the charge before it is loaded into the mine, the charge is heated, after which the hot gases are supplied to the recuperator to heat the air.

The proposed method for smelting cast iron is rationally carried out in a gas cupola with refractory and carbon-containing blank spikes. When converting coke cupola to gaseous fuel, working coke ears are not loaded into the cupola shaft, but only metal working ears and pieces of flux (limestone) are loaded. The height of the working part of the coke cupola shaft is 5 to 6 shaft diameters in the light. In this case, 5-6 metal and 5-6 coke oven heads are placed in the cupola. When transferring coke cupola to gas heating and loading only working metal spikes, the upper part of the mine remains unloaded with the charge. It was revealed that the charge V 0.5-0.8 of the shaft volume V _{1 is} filled, the upper part of the shaft remains empty, the charge remains empty, the refractory lining of this part of the shaft during heating of the gas cupola is heated to a temperature above 600 ° C.

For smelting a mixture containing more than 20% steel in a gas cupola, using a carbon-containing blank spike and supplying air with a temperature above 650 ° C to gas burners, an air flow coefficient α _{1 of} 0.7-0.9 can be maintained, and therefore oxidizing properties cupola gases are sharply reduced, waste is reduced and the fluidity of the metal is increased. But to achieve profitability and environmental cleanliness of the process, it is necessary to burn cupola gases in the unfilled charge part of the cupola mine. And since the temperature of the lining in this part of the mine is sufficient (over 600 ° C) to ignite the combustible components of cupola gases, only the necessary amount of air can be introduced to re-burn the gases without introducing additional fuel.

Since the height of the unfilled charge of the mine is small, it is necessary to supply air to the unfilled charge of the mine with peripheral and radial jets at a speed in the outlet sections of nozzles W 1,5-7 of the gas velocity in the charge W ₁ and the frequency of change of peripheral air supply by radial jets N 15- 60 periods per minute, create a vortex mixing of hot gases with air, increase the air flow coefficient in an empty charge shaft to α ₂ 1.01-1.5, burn out combustible components, raise the temperature of gases Т to 700-1200 ° С and supply hot gases in those exchange device.

It is rational to feed hot gases into the recuperator and heat the air, which then must be introduced into the burners of the cupola for burning fuel. Hot gases can be passed through the charge before it is loaded into the shaft, the charge is heated, and then the heated charge is loaded into the shaft and melted. You can pass hot gases through the charge before it is loaded into the mine, heat the charge, after which hot gases are supplied to the recuperator to heat the air. The charge must be suspended in perforated tubs in the zone of the cupola loading window, close the loading window with a door, heat the mixture with hot gases flowing around and passing through the holes of the tub for 5-15 minutes, and then load the mixture into the shaft after heating. After this, it is necessary to change the empty tub to the filled charge and to resume the process of heating the charge. It is rational to place a recuperator for heating air above the cupola cup loading window (in a pipe or instead of a cupola cupola).

The technical result of the proposed method is to save fuel on the melting process, increase productivity and thermal efficiency of the cupola, the possibility of heating the air blast and charge by using the heat of the burned cupola gases, reduce metal loss due to oxidation, increase the amount of steel in the charge, increase the temperature and fluidity of the metal , decrease in marriage of the received castings.

The technical result of the method is achieved at 0.5 · V ₁ ≤V≤0.8 · V ₁ ; 0.7 α α ₁ 0 0.9; l, 5 · W ₁ ≤W≤7 · W ₁ ; 15≤N≤60; 1.01 α α _{2 1} 1.5; 700≤T≤1200 ° C.

At V <0.5 · V ₁ and at V> 0.8 · V _1, the temperature regime of afterburning of cupola gases is violated.

If α ₁ <0.7, then the temperature of cupola gases decreases sharply and there is no afterburning of combustible components, and if α ₁ > 0.9, then the content of combustible components is insufficient for afterburning and raising the temperature of gases above 700 ° C. At W <1.5 · W _{1, the} air jets create insufficient gas turbulence, and at W> 7 · W _1, air streams slip through the waste cupola gases, and therefore the combustion process is disturbed. At N <15 and N> 60, violations of the required turbulence for ignition and combustion of gases occur. At α ₂ <1.01, gas underburning is observed, and at α ₂ > 1.5, the gas temperature sharply decreases. If T <700 ° C, then the efficiency of the beneficial use of the heat of gases is low, and if T> 1200 ° C, the oxidizing properties of gases sharply increase. Best results are achieved with the above limits.

Example

Smelted iron and steel charge in a gas cupola with a capacity of 6 tons of molten metal per hour. They made the ignition of gas burners, heated the lining, loaded the materials of the idle refractory heads (20% battle of fireclay bricks, 20% battle of high-alumina refractories, 60% battle of graphite electrodes). After heating the idle refractory ears to 1600-1650 ° C, the flow rate of natural gas and air was controlled so that an air flow coefficient of 0.7≤α ₁ ≤0.9 was achieved. Then loaded a metal charge (20% steel scrap and 80% cast iron scrap) and pieces of limestone (0.5-1% of the weight of metal filling). Filled with a charge of 0.5-0.8 volume of the mine and began melting. Air was fed into the empty shaft with peripheral and radial jets at a speed in the exit sections of the nozzles of 1.5-7 gas velocities in the shaft and the frequency of the peripheral air change with radial jets of 15-60 periods per minute, created a vortex mixing of hot gases with air, increased the coefficient of air flow in the unfilled charge mine to 1.01-1.5, burned up combustible components, increased the temperature of the gases to 700-1200 ° C and supplied hot gases to the heat exchanger. The heat of the hot gases was used to heat the air in the heat exchanger to a temperature of 650 ° C and above (up to 750 ° C). Hot gas was introduced into the burners to burn fuel. After burning, hot gases were passed through the charge until it was loaded into the mine, the charge was heated, and then the heated charge was loaded into the mine and melted. The mixture was heated in perforated tubs, which were suspended in the area of the boot window of the cupola. The mixture was heated for 5-15 minutes to a temperature of 500-600 ° C. Cast iron was smelted in a gas cupola, which was used for the production of complex and critical compressor castings. The quality of the castings was high.

It is established that when using the proposed method, compared with the known ones, fuel savings of 5-15% are achieved (for the smelting process), an increase in productivity by 10-20% and thermal efficiency of the cupola furnace by 1.1-1.4 times, heating of air blast to 650 ° С and higher, ecological purity of the final process, reduction of metal losses due to oxidation by 1.5-2 times, increase in the amount of cheap steel in the charge over 20%, increase in metal temperature by 30-50 degrees and fluidity by 1.3 -2 times, decrease in rejects of obtained castings by 2-4%.

The proposed method provides a technical effect and can be carried out using means known in the art. The implementation options of the proposed method achieve various requirements for products intended for mechanical engineering, construction. This method can be used to obtain an intermediate product - a liquid material for conversion to steel. It can be used for heating and smelting mineral materials to obtain stone casting, slag.

Claims (4)

1. A method of melting cast iron in a gas cupola, including loading the charge into the mine, burning fuel, heating and melting the mixture with fuel combustion products, characterized in that the fuel is burned at an air flow rate of 0.7-0.9, the shaft is filled with a charge of 0, 5–0.8 of the shaft’s volume and into the empty shaft the mine is supplied with air by peripheral and radial jets at a speed in the exit sections of nozzles of 1.5–7 the gas velocity in the mine and the frequency of change of air supply by peripheral jets to radial jets for 15-60 periods in a minute create vortex mixing of hot gases with air, increase the coefficient of air flow in an unfilled charge mine to 1.01-1.5, burn combustible components, raise the temperature of gases to 700-1200 ° C and supply hot gases to a heat exchanger for heating air or pass them through the charge. 2. The method according to claim 1, characterized in that the hot gases are supplied to the recuperator and the air is heated, which is introduced into the burners of the cupola for burning fuel. 3. The method according to claim 1, characterized in that the hot gases are passed through the charge before it is loaded into the mine, the charge is heated, and then the heated charge is loaded into the mine and melted. 4. The method according to claim 1, characterized in that the hot gases are passed through the charge before it is loaded into the mine, the charge is heated, after which the hot gases are fed to a recuperator for heating the air.