Charging of Direct Reduced Iron in Electric Arc Furnaces
1. Charging of hot briquetted iron
Hot briquetted iron is the high temperature direct reduction iron pressurized molding, in the use of the distribution in the basket and scrap together with the addition of the furnace. TPCO 150 t electric arc furnace practice experience, a single batch of hot briquetted iron (100 mm × 50 mm × 30 mm) to use no more than 20% of the ratio is appropriate, the proportion of too large will make the furnace lumps and difficult to melt, resulting in smelting difficulties. It can be seen that, in order to speed up the production rhythm while ensuring low power consumption, should control the size of the hot briquetted iron and the ratio can not be too large.
2. Charging of Direct Reduced Iron
Batch charging
Directly reduced iron added to the electric arc furnace proportion varies, if the proportion of direct reduction of iron is less than 30%, can be used cans of material loading. The bottom of the basket is filled with light scrap, followed by heavy scrap and direct-reduced iron, to avoid too much lumping of direct-reduced iron. However, when the arc heats the thicker layers of direct reduced iron, the molten metal fills the spaces between the direct reduced iron and condenses, causing the charge to sinter into a single piece, making it difficult to add the charge as a whole to the molten pool and extending the melting cycle. When more than 30% of the charge is added in batches, due to the slow heat transfer of the direct-reduced iron, the relevant technical indicators are poor, and should be fed into the furnace by means of continuous charging.
Continuous charging
When the dosage of direct-reduced iron is large, continuous charging is adopted, usually through the charging hole at the top of the furnace to realize charging. One is to open a hole in the center of the furnace roof so that the direct reduced iron falls in the vertical direction; the other is to open a hole in the middle of the radius of the furnace roof and enter the furnace through the rail. Continuous feeding systems require a high height to ensure rapid passage of the direct-reduced iron through the slag layer. Generally, the initial feed rate is 1/2 to 1/3 of the normal feed rate, with full load feeding in the middle stage. But in the late stage, in order to quickly increase the liquid steel temperature, as soon as possible to reach the steel temperature, should slow down the feeding rate.
TPCO 150 t ultra-high-power electric arc furnace in the use of direct-reduced iron (ratio of 100%) smelting with steel and slag operation, charging using the top of the furnace continuous charging mode, first of all, the scrap steel melting, and then direct-reduced iron to join the molten pool. The charging system is as follows:
(1) The energy consumption level of scrap in the last basket is 100 kWh/t, and 500 kg/min is used for direct-reduced iron charging;
(2) When the smelting energy consumption is 200 kWh/t, the dosing rate is 1 000 kg/min; after the melt is clear, the dosing rate is 2 500 kg/min;
(3) When the measured temperature exceeds 1 560 ℃, the charging rate is about 2 900 kg/min;
(4) When there are 10-15 t and 5-10 t of direct-reduced iron left, the feeding rate of direct-reduced iron is 1 500 kg/min and 500-600 kg/min respectively.
