JP5151112B2 - Hot metal desulfurization treatment method - Google Patents

Description

  The present invention relates to a method of desulfurizing a hot metal by adding a flux containing a desulfurizing agent to the hot metal and rotating and stirring the impeller.

2. Description of the Related Art Conventionally, there has been known a method for performing desulfurization treatment of hot metal by adding a desulfurizing agent or the like into pig iron contained in a hot metal ladle and mechanically stirring the hot metal using an impeller.
In this conventional method, as shown in FIG. 3, the rotation speed of the impeller is controlled to a constant value (for example, 120 to 140 rpm) during the desulfurization treatment period. Further, as shown in FIG. 3, the flux is added to the hot metal in two portions in the initial stage during the desulfurization treatment period. For example, 2/3 of the total amount of flux to be added is added at the first time, and the remaining 1/3 is added at the second time.

In relation to such a conventional method, one that quickly stops the rotation of the impeller (see Patent Document 1) or one that prevents an operation stop due to an overload of a stirring motor that rotates the impeller (see Patent Document 2) Etc. are known.
JP 2003-82408 A JP 2003-82409 A

By the way, in the conventional method, as shown in FIG. 3, the rotation speed of the impeller is controlled to a constant value during the desulfurization treatment period. However, the following desulfurization reaction mechanism hinders improvement of desulfurization efficiency. The knowledge that it is.
That is, the desulfurizing agent (CaO 2 or the like) is supplied in the form of powder or particles to the hot metal, but the desulfurization reaction proceeds depending on the reaction interface area (surface area) of the desulfurizing agent. When the impeller rotation speed is controlled to be constant, the reaction on the surface of the desulfurizing agent is saturated at a certain time. For this reason, the desulfurization agent lost the new reaction interface, the desulfurization reaction stopped, and the knowledge that the improvement of the desulfurization reaction beyond it was not expectable was acquired.
The present invention has been completed based on the knowledge, and its purpose is to newly create a reaction interface of the desulfurizing agent during the desulfurization treatment period and to improve the desulfurization efficiency of the hot metal. It is in providing the desulfurization processing method of this.

In order to solve the above-described problems and achieve the object of the present invention, each invention is configured as follows.
A first invention is a method of performing desulfurization processing of hot metal by adding a desulfurizing agent to hot metal and rotating the impeller to stir the hot metal, and the impeller is removed from the start of the desulfurization processing until a predetermined time elapses. After rotating at a predetermined rotational speed, the rotational speed of the impeller is relatively lowered and held for a certain period of time, and then the rotational speed of the impeller is relatively increased from when it is lowered, and then the desulfurization process is terminated. I made it.

A second invention is a method for performing desulfurization treatment of hot metal by adding a desulfurizing agent to hot metal, rotating the impeller, and stirring the molten iron, and the impeller is removed from the start of the desulfurization treatment until a predetermined time elapses. The impeller is rotated at a predetermined speed, and then the impeller is temporarily stopped. Thereafter, the impeller is rotated at a speed higher than that at the time of the stop to finish the desulfurization process.

  A third invention is a method for performing desulfurization treatment of hot metal by adding a desulfurizing agent to hot metal and rotating the impeller to stir the hot metal, wherein all steps of the desulfurization treatment are performed in the previous stage, the middle stage, And the latter step, the impeller is rotated at a predetermined rotational speed in the previous step, and the impeller is rotated relative to the rotational speed of the previous step in the middle step, The desulfurizing agent in the hot metal was floated on the surface, and in the latter stage process, the rotation speed of the impeller was relatively increased with respect to the rotation speed in the middle stage process.

According to a fourth aspect of the present invention, in the third aspect, in the intermediate step, instead of the method, the rotation of the impeller is temporarily stopped so that the desulfurizing agent in the hot metal floats on the surface, In the latter process, instead of the method, the impeller is rotated at a higher rotational speed than when it is stopped to perform the desulfurization treatment.
According to a fifth aspect of the present invention, in the third or fourth aspect of the invention, in the previous step, a part of the entire desulfurizing agent to be added is further added at a predetermined timing.
In the latter stage process, the remainder of the entire desulfurization agent is further added at a predetermined timing .

In the present invention, since the rotation speed of the impeller is temporarily reduced or the rotation of the impeller is temporarily stopped during the desulfurization treatment period, the stirring of the molten iron is temporarily restricted. For this reason, the desulfurization agent in a saturated state reacted with sulfur (S) in the hot metal can be raised or floated on the surface of the hot metal.
Further, in the present invention, since the desulfurizing agent is raised on the surface of the hot metal, the rotational speed of the impeller is increased again, or the impeller is rotated again, so that the increased desulfurizing agent collides with the impeller and causes cracks. Occurs or breaks. For this reason, a new reaction interface appears by the crack etc. of a desulfurization agent, and, thereby, a new desulfurization reaction advances.
Therefore, according to the present invention, it can be expected that the desulfurization efficiency of the hot metal will be remarkably improved by the above mechanism as compared with the conventional one.

Embodiments of the present invention will be described below with reference to the drawings.
In the embodiment of the method of the present invention, as shown in FIG. 1, desulfurization is performed by mechanically stirring hot metal with an impeller 2 in a hot metal ladle 1 containing hot metal a. The impeller 2 is a wing-type impeller, for example.
The impeller 2 is rotated by a motor 3. The rotation control of the motor 3 is performed by the control device 4, whereby the rotation control of the impeller 2 is performed.
An input device 5 capable of various settings is connected to the control device 4. The input device 5 can set a rotation control pattern (operation pattern) of the impeller 2 performed by the control device 4 through the rotation control of the motor 3 (see FIG. 2).

(First example of hot metal desulfurization method)
Next, a first example of the hot metal desulfurization method performed using the apparatus shown in FIG. 1 will be described with reference to FIG.
In this first example, the user uses the input device 5 to change the operation pattern of the control device 4 so as to realize an operation pattern as shown in FIG. It is assumed that the memory is preset. And the control apparatus 4 shall perform rotation control of the motor 3 so that the drive pattern of the set impeller 2 may be implement | achieved.

In the hot metal desulfurization treatment of the first example, the entire process is divided into a first-stage process, a middle-stage process, and a second-stage process (see FIG. 2).
Here, the first-stage process is a period (time) from the time when the impeller 2 starts to rotate until the predetermined rotation speed is reached until the desulfurization reaction is saturated and the desulfurization reaction does not proceed. This is a period in which the desulfurizing agent entrained in the hot metal is levitated, and the latter process is a period in which the impeller 2 is rotated at a predetermined rotational speed and the desulfurizing agent is entrained in the hot metal in order to advance the desulfurization reaction again. . Usually, the first step is 3 to 5 minutes, the middle step is 0.5 to 1.5 minutes, and the latter step is 3 to 5 minutes.

In this desulfurization treatment, a flux containing a desulfurization agent (CaO or the like) is added to the hot metal a at a predetermined timing during the treatment period.
First, when the desulfurization treatment is started, the impeller 2 is started to rotate, and in the previous step, the impeller 2 is rotated at a predetermined rotation speed (for example, 120 to 140 rpm) for a predetermined time. Immediately after the start of the desulfurization treatment and in the previous step, a part of the total flux to be added is added to the hot metal a at a predetermined timing. In this example, immediately after the start of the desulfurization treatment, ½ of the total flux (including the desulfurization agent) to be added is added (introduced), and the impeller 2 is rotated for a predetermined rotation speed period (previous term). In the middle of the step), 1/4 of them were added.

Since the CaO-based desulfurization agent tends to agglomerate in the hot metal, if it is added at once, the desulfurization agent becomes a large lump and unreacted CaO is increased. However, if the number of divisions is increased, the dust is sucked by the dust collector at the time of charging, and the loss increases. Therefore, it is preferable to load the flux containing the desulfurizing agent in two or three times as described above.
As a result, in the previous step, the desulfurizing agent added to the hot metal a reacts with sulfur (S) in the hot metal a, but the desulfurization reaction becomes saturated at a certain point, and the desulfurization reaction proceeds thereafter. Disappear.

In the medium-term process, the rotation speed of the impeller 2 is relatively lowered with respect to the predetermined rotation speed in the previous-stage process, and the lowered state is maintained for a predetermined time. At this time, the rotational speed of the impeller 2 is lowered to 60 rpm, for example, and the state is maintained for about 30 seconds, for example.
As a result, since the stirring of the hot metal a is temporarily restricted in the intermediate process, the desulfurization agent in which the desulfurization reaction is saturated in the previous process can be raised or floated on the surface of the hot metal a. Therefore, the reduction in the rotation speed of the impeller 2 and the maintenance time for the reduction in the middle-stage process are required to raise or float the desulfurizing agent on the surface of the hot metal a.

Here, in the mid-term process, the rising point of the desulfurizing agent (slag) becomes black on the hot metal surface and can be confirmed visually or with a monitor.
In the middle-stage process, it is preferable to reduce the rotation speed of the impeller 2 as described above from the viewpoint of shortening the processing time rather than stopping the rotation of the impeller 2 as described later. That is, when the rotation of the impeller 2 is stopped, it takes time to stop the rotation of the impeller 2 and increase it again to a predetermined number of rotations in order to secure the stirring time, and the addition of equipment becomes large. Because.

  In the latter stage process, the rotational speed of the impeller 2 is increased relative to the rotational speed of the middle stage process, this increased state is maintained for a predetermined time, and the desulfurization process is resumed. Thereafter, the rotation of the impeller 2 is stopped. To complete the desulfurization process. In this latter process, the remaining 1/4 of the flux is added to the hot metal a at a predetermined timing. In this example, the remaining flux is added in the middle of the period when the rotation of the impeller 2 reaches a predetermined rotation speed.

  As a result, in the latter process, the rotational speed of the impeller 2 is increased again in a state where the desulfurizing agent floats on the surface of the hot metal a, so that the desulfurizing agent in the saturated state collides with the impeller 2. Cause cracks or cracks. In addition, the form of the impeller 2 is preferably one that can ensure the original stirring action and can effectively realize those phenomena.

For this reason, a new reaction interface appears in the desulfurization agent due to the crack or crack, and a new desulfurization reaction proceeds through the reaction interface. Furthermore, since the flux containing the desulfurizing agent is newly added (added) in the latter stage process, the added desulfurizing agent causes a desulfurization reaction with sulfur in the molten iron a.
Therefore, in the hot metal desulfurization treatment having the operation pattern as shown in FIG. 2, the hot metal desulfurization efficiency can be remarkably improved by the above mechanism.

(Second example of hot metal desulfurization method)
Next, a second example of the hot metal desulfurization method performed using the apparatus shown in FIG. 1 will be described.
In the second example, as in the first example, all processes of the hot metal desulfurization process are divided into a first stage process, a middle stage process, and a second stage process. Similarly, a flux containing a desulfurizing agent is added to the hot metal a at a predetermined timing of the treatment period (for example, the same timing as in the first example).

However, in the second example, the method in the first step is basically the same as the method in the first step in the first example, but the method in the middle step and the second step is changed as follows. Since this is done, the different changes will be described.
That is, the rotation of the impeller 2 is temporarily stopped in the medium-term process in the second example. As a result, in the medium-term process, as in the first example, the desulfurization agent in which the desulfurization reaction in the hot metal a is saturated can be floated on the surface.

Further, in the latter process in the second example, the rotation of the impeller 2 once stopped is resumed, and the rotation speed of the impeller is set to a predetermined rotation speed (for example, the predetermined rotation speed in the previous process), and this state is maintained for a predetermined time. The desulfurization treatment was performed while maintaining, and then the rotation of the impeller 2 was stopped to finish the desulfurization treatment. As a result, in the latter process, the same operation and effect as in the later process in the first example can be realized.
Therefore, according to the second example, similar to the first example, the desulfurization efficiency of the hot metal can be significantly improved as compared with the conventional example.

It is explanatory drawing for demonstrating the outline | summary of the apparatus for implement | achieving embodiment of the method of this invention. It is explanatory drawing of the operation pattern of the impeller explaining the 1st example of the desulfurization processing method of the hot metal of this invention. It is explanatory drawing of the driving | operation pattern of the impeller explaining the example of the conventional desulfurization processing method of hot metal.

Explanation of symbols

a Hot metal 1 Hot metal pan 2 Impeller 3 Motor 4 Control device 5 Input device

Claims (5)

A method of adding a desulfurizing agent to hot metal and rotating the impeller to stir the hot metal to desulfurize the hot metal,
The impeller is rotated at a predetermined rotational speed from the start of the desulfurization treatment until a predetermined time has elapsed, and then the rotational speed of the impeller is relatively lowered and held for a certain period of time, and then the rotational speed of the impeller is decreased from the time of reduction. The hot metal desulfurization treatment method is characterized in that the desulfurization treatment is finished after the relative increase. A method of adding a desulfurizing agent to hot metal and rotating the impeller to stir the hot metal to desulfurize the hot metal,
The impeller is rotated at a predetermined rotational speed from the start of the desulfurization treatment until a predetermined time has elapsed, and then the impeller is temporarily stopped rotating, and then the impeller is rotated at a higher rotational speed than when stopped. A desulfurization treatment method for hot metal, characterized in that the desulfurization treatment is terminated. A method of adding a desulfurizing agent to hot metal and rotating the impeller to stir the hot metal to desulfurize the hot metal,
The entire process of the desulfurization process is divided into a first-stage process, a middle-stage process, and a second-stage process,
In the first stage process, the impeller is rotated at a predetermined rotational speed,
In the middle stage, the rotational speed of the impeller is lowered relative to the rotational speed of the previous stage so that the desulfurizing agent in the hot metal floats on the surface,
In the post-construction process, the rotational speed of the impeller is relatively increased with respect to the rotational speed of the medium-term process. In the intermediate stage, instead of the method, the rotation of the impeller is temporarily stopped so that the desulfurizing agent in the hot metal floats on the surface,
4. The desulfurization processing method according to claim 3, wherein, in the latter step, the desulfurization treatment is performed by rotating the impeller at a higher rotational speed than when stopped in place of the method. In the first stage process, at a predetermined timing, a part of the total desulfurization agent to be added is added,
5. The hot metal desulfurization method according to claim 3, wherein in the latter step, the remainder of the entire desulfurizing agent is added at a predetermined timing.

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