RU2248402C1 - Method for melting of cast iron in gas cupola - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method involves heating carbon-containing refractory coke bed and melting-through charged burden by burning of air-and-gas mixture flowing from burners; cutting-off supply of gas and air in some burners in case decrease of furnace capacity is required without stopping of melting process course, with flow rate of air-and-gas mixture from operating burners being kept at the same level.

EFFECT: reduced thermal loading of furnace shaft without changing process parameters of melting procedure other than furnace capacity, which may be decreased.

1 tbl, 1 ex

Description

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

There is a known method of smelting cast iron in a gas cupola, in which the gas and air flows, with an air flow coefficient α≈1.0, are selected so that the rate of outflow of the gas-air mixture from the burner nozzle channel ensures gas combustion in the burner tunnel (see A.A. .Black "Features of the combustion of natural gas in gas cupolas. Foundry, 1996, No. 5, p.27-28).

The disadvantage of this method is that the combustion of the gas-air mixture occurs in the burner tunnels, which during the smelting process flare up, the gas-dynamic characteristics of the combustion process are violated and the smelting is upset.

Closest to the technical nature of the claimed is a method of melting cast iron in a gas cupola (see "Melting cast iron in a gas cupola" - Foundry, 1985, No. 2, p.9-10). The method consists in heating the lining, heating the idle refractory spike containing carbon material, loading the metal charge with periodic additions of the spike and melting the charge due to the heat of the products of gas and air combustion, with an air flow coefficient α = 0.98-1.02. This method allows you to normally conduct the melting process while ensuring optimal cupola productivity, however, in production conditions, situations constantly arise when it is temporarily necessary to reduce productivity without stopping the melting course (breakdown of one of the casting conveyors, etc.). This is especially true for cupolas with continuous selection of metal, i.e. not having a piggy bank.

The objective of the proposed method is to maintain optimal operating conditions of the cupola if it is necessary to reduce the furnace productivity without stopping the melting process and without changing other technological parameters of the melting process, namely the temperature of the metal on the trough and the temperature of the exhaust gases in the area of the filling window. This is achieved by the fact that in order to reduce the furnace productivity without stopping the melt, the gas and air supply to some burners is switched off and at the same time they maintain the former, adjusted for optimal cupola productivity, air-gas mixture outflow rate from operating burners.

Reducing the flow of gas and air, thus, can reduce the heat load in the mine and reduce the cupola productivity without stopping the melting process and changing other technological parameters of the melting process.

In a gas cupola with a single refractory spike under optimal combustion conditions, i.e. the outflow rate of the gas-air mixture from the burner tunnels is 27-36 m / s, the combustion of the gas-air mixture occurs inside the blank spike, and not in the tunnels, while the cupola bottom and the spike itself are heated to a temperature of 1873-1923K, and the burner tunnels do not flare up.

The reduction in gas and air flow, while maintaining α = 0.98-1.02, providing a velocity of the gas-air mixture from the burner tunnels less than 27 m / s leads to the fact that the static pressure of the charge column exceeds the dynamic pressure of the gas-air mixture and does not allow it to penetrate inside idle ears. Combustion of the mixture occurs in the wall layers along the height of the shaft, where the static pressure is lower, and above the upper layer of the charge, while the temperature in the area of the filling window rises to 1100-1200 ° C, which leads to deformation and failure of the metal structures of the cupola, the inner layers of the KHOK and the hearth is chilled, the temperature of the metal on the gutter decreases, which does not meet the requirements of the metal pouring process. When the gas and air flow rate ensures the flow rate of the gas-air mixture from the burner tunnels above 36 m / s, the local resistance in the channels between the chokes is sharply increased and the mixture does not penetrate the chokes, but burns, rising up along the walls of the mine, where the resistance is lower and above with a charge layer, the temperature in the area of the filling window also rises to 1100-1200 ° С, which leads to deformation and failure of the metal structures of the cupola and the loading device units, and the inner layers of the CCC and the cupola bottom are chilled vayutsya metal temperature trough is reduced, which does not comply with the requirements of the process of metal casting.

An example of the method

The melts were carried out on a gas cupola with a single refractory spike with a capacity of 12 t / h, having a compression slag separator. After warming the cupola shafts and the idle refractory ears, the metal charge was piled up and melted, providing a rate of exit of the gas-air mixture from the burner tunnels equal to 31 m / s with an air flow coefficient α = 0.98-1.02. Then the cupola productivity was reduced, reducing the gas and air consumption by sequentially switching off the burners in such a way as to ensure the air-gas mixture flow rate from the burner tunnels of the working burners within 18-45 m / s, while maintaining the air flow coefficient α = 0.98-1.02 . In the course of work, the technological parameters of the melting were monitored. The melting results are presented in the table.

As can be seen from the table, the application of the method, i.e. switching off such a number of burners at which the rate of outflow of the gas-air mixture from the burner tunnels is kept within 27-36 m / s allows to conduct the melting process stably while reducing the gas cupola productivity without changing other technological parameters of the melting process.

The proposed method is comprehensively investigated and accepted for implementation at the Cheboksary Aggregate Plant.

The application of the proposed method of cast iron smelting in a gas cupola made it possible to reduce the temperature of the exhaust gases in the area of the filling window from 1200 ° C to 550 ° C and to exclude deformation of the metal structures of the cupola shaft and decommissioning of the elements of the loading device and to ensure the temperature of the metal on the gutter in accordance with the requirements of the technological process pouring metal.

Smelting conditions Cupola performance; t / h Gas consumption; m ³ / hour Air flow; m ³ / hour Air flow rate Number of working burners; PCS The flow rate of the gas mixture from the burner tunnels; m / s Flue gas temperature in the area of the filling window; ° C The temperature of the metal on the gutter; ° C Known method 12 960 8900 1,02 6 31 550 1410 nine 720 6600 0.98 6 23.3 850 1360 6 480 4450 1,0 6 15,5 1200 1310 nine 720 6600 0.98 3 47 1170 1320 nine 720 6600 0.98 4 35 600 1405 The proposed method nine 720 6600 0.98 5 28 620 1402 6 480 4450 1,0 2 47 1130 1330 6 480 4450 1,0 3 31 500 1410 6 480 4450 1,0 4 23.3 820 1375 6 480 4450 1,0 5 18.7 1100 1340

Claims (1)

A method of melting cast iron in a cupola, including heating a carbon-containing idle refractory top and melting a charged metal charge by burning a gas-air mixture flowing out from the burners, characterized in that, if it is necessary to reduce the furnace capacity without stopping the melting process, the gas and air supply to some burners is turned off and while maintaining the same, adjusted to the optimal productivity of the cupola furnace, the rate of flow of the gas-air mixture from the working burners.