JPS6261875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for preheating steelmaking raw materials such as scrap and reduced iron to be charged into a steelmaking arc furnace.

Conventionally, there are methods for preheating raw materials for steelmaking as shown in FIGS. 1 to 3.

The example shown in FIG. 1 is a preheating method in which a dedicated preheating chamber is installed in the furnace waste gas dust collector, and the raw material is preheated in the preheating chamber. Break flange c, communication duct d
In the dust collector for an arc furnace, in which a combustion tower e is connected to the combustion tower e, and a cooling tower f, a suction blower g, and a dust collector h are connected to the combustion tower e, there is a A dedicated preheating chamber i is provided that can preheat the scrap raw material of the arc furnace using the sensible heat of the furnace waste gas, and the furnace waste gas can be introduced from the combustion tower e to the preheating chamber i via the communication duct j. At the same time, the combustion tower e and the cooling tower f are connected by a bypass duct k, and waste gas inflow switching valves l and m are provided in the communication duct j and the bypass duct k, respectively, so that the raw material put into the preheating chamber i is transferred to the preheating chamber. The raw material is preheated for a certain period of time using furnace waste gas at step i, and the preheated raw material is collected at bucket n, the furnace lid is opened, and the material is charged into the furnace from the upper part of the furnace. Scrap raw material to be newly preheated is re-injected from the upper part of the preheating chamber and preheating is repeated.
During the period when the waste gas cannot be introduced into the furnace, the waste gas inflow switching valve l of the connecting duct j is closed, and the waste gas inflow switching valve m of the bypass duct k is opened to allow the furnace waste gas to flow through the bypass duct k and the cooling tower f to the dust collector h. I'm trying to get it installed.

In this method, normally, the reactor waste gas is led to the combustion tower e, where it is mixed with air sucked in from the break flange c section to burn unburned gas mainly composed of CO gas, and the dust collector system In order to prevent explosions within the combustion tower e, the waste gas, which has reached a temperature of 900 to 1100°C, is used to preheat the scrap raw material charged in advance into the preheating chamber i. It can be preheated to ~400℃.

The example shown in FIG. 2 is a dust collector similar to that shown in FIG. 1, but instead of the dedicated preheating chamber i in FIG. In this method, waste gas of 800 to 1100 DEG C. after being combusted in a combustion tower e similar to that shown in FIG. 1 is introduced from the upper part of the preheating chamber o to preheat the scrap raw material.

This method has the advantage that since the scrap can be directly preheated in the scrap charging bucket p, the subsequent operation of charging the scrap into the arc furnace is relatively simple.

The example shown in Fig. 3 has a configuration similar to the method shown in Fig. 2, but a pyrolysis furnace q is installed on the secondary side of the preheating chamber o, and white smoke and This is a method of thermally decomposing waste gas containing foul odors at high temperatures.

Generally, scraps used in arc furnaces come in various shapes and types, and scraps such as automobile scraps and home appliances have various paints, dusts, and oils attached to them. For this reason, when scrap is preheated using the method shown in Figures 1 and 2, the preheating reaction of the scrap generates white smoke and bad odors, which are emitted by the dust collector.
leaks to the outside and causes secondary pollution.

According to the method shown in Fig. 3, this problem can be prevented.For this purpose, a combustor r such as a burner is installed in the pyrolysis furnace q to raise the exhaust gas temperature again and promote pyrolysis. are doing.

However, the conventional preheating method shown in FIGS. 1 to 3 has various drawbacks as follows.

(b) Since the furnace waste gas introduced into the preheating chamber is combusted in the combustion tower e by introducing one or several times more outside air, it is not possible to introduce higher temperature waste gas into the preheating chamber. Preheating efficiency is low and scrap preheated to a higher temperature cannot be obtained.

(b) Since higher temperature waste gas of 1,200 to 1,300°C or higher is not used for preheating, secondary pollution such as white smoke and bad odor generated by heat exchange with scrap is likely to occur.

(c) The preheated scrap is taken out of the preheating chamber and charged into the furnace by opening the lid from the top of the furnace using a crane, etc., so the scrap remains at a constant temperature until it is inserted into the furnace. The sensible heat of the scrap, which has fallen and has been preheated, cannot be used effectively.

(d) If the scrap charging bucket p is stored as is in the preheating chamber o as shown in FIG. 2 and preheated, the bucket p will be subject to heat load and will be easily damaged.

(e) If a pyrolysis furnace q is installed to prevent secondary pollution as shown in Figure 3, the space will be too large, and the entire preheating device will also be too large, increasing equipment costs.

(F) The examples shown in FIGS. 1 to 3 are all batch preheating methods, which increases the handling of the scrap after preheating when charging into the furnace. Furthermore, since it is not a continuous charging type, the preheating time is limited by the operating cycle of the furnace.

The present invention aims to eliminate the drawbacks of such conventional methods, and aims to charge raw materials for steelmaking such as scrap and raw steel into the furnace from a raw material storage hopper, and store the raw materials for decommissioning in the raw material storage hopper. The raw material is preheated by directly introducing gas, and the waste gas after preheating is thermally decomposed in the combustion tower.
Furthermore, outside air can be sucked into the raw material storage hopper.

Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 4, a furnace waste gas suction elbow 2 provided on the furnace lid of a steelmaking arc furnace 1 is connected to a combustion tower 4 via a break flange 3, and a raw material storage hopper is installed in the middle of the suction elbow 2. By connecting the lower part of the hopper 5 so that it can be opened and closed by a damper 6, and opening and closing the damper 6 by a hopper opening/closing device 7, the raw material for steel making in the raw material storage hopper 5 passes through the suction elbow 2 and is continuously and tightly sealed inside the furnace 1. A seal cover 8 is provided on the top of the raw material storage hopper 5 so as to be openable and closable, and the top of the raw material storage hopper 5 and the combustion tower 4 are communicated through a connecting duct 9. Between the suction elbow 2 and the lower part of the raw material storage hopper 5, there is provided a waste gas introduction pipe 10 for directly introducing the reactor waste gas from the suction elbow 2 to the raw material storage hopper 5. Outside air suction pipe 11 and CO in the hopper to keep the gas as non-explosive combustion gas
A gas component control device will be provided. The gas component control device is provided at the top of the raw material storage hopper 5.
The CO gas concentration detection device 12, the outside air amount control valve 13 provided in the middle of the outside air introduction pipe 11, the above-mentioned CO
a CO gas concentration indicating controller 14 that controls the control valve 13 based on the value detected by the gas concentration detection device 12; reactor waste gas amount control valves 15 and 16 provided in the middle of the suction elbow 2 and the waste gas introduction pipe 10; An introduced waste gas amount ratio setting device 17 is provided to control these reactor waste gas amount control valves 15 and 16.

18 is a suction blower, and 19 is a dust collector.

With the above configuration, when preheating the raw material, first operate the opening/closing device 7 of the hopper 5 to close the damper 6, and then open the seal cover 8 of the hopper 5 to preheat the initial charging amount. The steelmaking raw material in the hopper 5 is charged into the hopper 5, the damper 6 is subsequently opened, the steelmaking raw material in the hopper 5 is charged into the furnace 1, and initial melting is started. Damper 6 during melting
is closed, and the furnace waste gas is passed through the suction blower 18.
so that the dust is always sucked into the dust collector 19.

Next, the steelmaking raw material for additional charging is charged into the hopper 5, and the reactor waste gas amount control valves 15, 1
6 to a proper ratio, the furnace waste gas generated by melting is made to flow into the hopper 5 via the waste gas introduction pipe 10.

The furnace waste gas during melting is usually at a high temperature of around 1300°C, and the gas composition is 30-50% CO gas, which is an unburned explosive gas. Therefore, if the reactor waste gas is allowed to flow into the hopper 5 as it is, the inside of the hopper 5 will become an explosive mixture consisting mainly of unburned CO gas, making it difficult to preheat the raw material for steelmaking in the hopper 5. Since this is dangerous, outside air is sucked into the hopper 5 through the introduction pipe 11. The intake amount of outside air is determined by operating the control valve 13 using the CO gas concentration detecting device 12 and the CO gas concentration indicating controller 14 installed above the hopper 5.
Normally, the explosion range of CO gas is 12 to 75% (610°C or higher), so if the CO gas concentration on the indicating controller 14 is set to about 0 to 3%, the CO gas concentration in the hopper 5 The outside air and furnace waste gas are sucked into the hopper 5 in a mixed state by operating the outside air amount control valve 13 so that the outside air amount control valve 13 is maintained at this set value. As a result, in the hopper 5, a combustion reaction similar to that in the combustion tower 4 of the dust collector takes place with the above-mentioned furnace waste gas and outside air, and safe and high-temperature waste gas is formed to preheat the above-mentioned raw material. .

The raw material preheated to a constant temperature in the hopper 5 is continuously and hermetically loaded into the furnace by opening the damper 6.

By repeating the above operations, additional raw materials can be safely preheated at a higher temperature.

The combustion waste gas used for preheating in the hopper 5 is introduced into the combustion tower 4 through a communication duct 9. In addition, the break flange 3 of the dust collector
Combustion is completely promoted due to the influence of air flowing in from the combustion tower 4, and the white smoke and bad odor generated by preheating can be suppressed by undergoing a thermal decomposition reaction in the combustion tower 4.

As described above, according to the device of the present invention, the furnace waste gas is properly mixed with outside air in the device that can continuously charge raw materials such as scrap and reduced iron into the arc furnace in a closed manner, and the raw material is stored in the raw material storage hopper. Since the heat is introduced into the air for preheating, the following excellent effects can be achieved.

(i) Compared to the conventional method in which preheating is performed using waste gas from the combustion tower of the dust collector, the preheating of raw materials for steelmaking can be performed with extremely high efficiency in a closed, continuous charging device.
Therefore, it is possible to simultaneously improve the furnace heat efficiency for preheating and the operational efficiency.

(ii) It is possible to suppress secondary pollution caused by the use of relatively low-temperature waste gas, such as white smoke and bad odor generated during preheating of raw materials, and the waste gas after preheating is heated in the combustion tower of the dust collector. Since it can be disassembled, special secondary pollution prevention equipment is not required, and equipment can be simplified.

(iii) Since it is a continuous charging type, the steelmaking raw material after preheating can be charged into the furnace without temperature drop.

(iv) The conventional method of charging preheated scrap into the furnace with the furnace lid open increases soot and smoke when charging into the furnace, but the present invention improves the surrounding environment because it is a closed and continuous method.

(v) A continuous charging preheating system for pellet-like raw materials such as reduced iron can be put to practical use.

[Brief explanation of the drawing]

1 to 3 are schematic diagrams showing an example of a conventional method for preheating raw materials for steel manufacturing, and FIG. 4 is a schematic diagram of a preheating device for raw materials for steel manufacturing according to the present invention. 1... Arc furnace, 2... Suction elbow, 4... Combustion tower, 5... Raw material storage hopper, 6... Damper, 9... Connection duct, 10... Waste gas introduction pipe,
11...Outside air introduction pipe, 12...CO gas concentration detection device, 14...CO gas concentration indicator controller.

Claims (1)

[Claims] 1. A storage hopper for steelmaking raw materials, such as scrap and reduced iron, whose lower part can be opened and closed, is directly connected to the suction elbow installed in the furnace lid of the arc furnace, and the raw material storage hopper and the suction elbow are connected directly to each other. In between, a furnace waste gas introduction pipe is installed to introduce the furnace waste gas from the suction elbow into the raw material storage hopper, and the furnace waste gas introduced into the raw material storage hopper is converted into non-explosive combustion gas. It is equipped with a pipe for introducing outside air and a CO gas composition control device in the raw material storage hopper, and a duct is installed between the raw material storage hopper and the combustion tower to introduce waste gas into the combustion tower after preheating the raw material for steel making. A preheating device for raw materials for steelmaking, characterized in that the device is arranged between.