KR101110252B1 - Sludge discharging method in pickling equipment for manufacturing orient electrical steel sheet - Google Patents

Abstract

The present invention precipitates silica sludge remaining in an acid solution in the course of pre-annealed and shot blasted (Shot Blaster) treated with hydrochloric acid in order to produce an electric steel sheet with a beautiful surface before cold rolling. The specific gravity of the sludge precipitated through the specific gravity meter using gamma ray installed on the lower discharge line of the sedimentation tank in the pickling tank was controlled to control the specific gravity to be discharged at the proper time before it solidified. When the shut-off valve is opened at the same time, the pump is driven to discharge treatment, and the discharge cycle is processed for 4 to 6 hours to produce a grain-oriented electrical steel sheet having a beautiful surface.

According to the present invention, the specific gravity of SiO ₂ sludge measured by gamma ray is controlled at 1.55 to 1.70, and the sludge discharge cycle is 4 to 6 hours to solve the problem of clogging of pipes and nozzles and to secure surface quality. It provides the effect of protecting workers from toxics.

Directivity, electrical steel, pickling tank, sedimentation tank, specific gravity measuring instrument, gamma ray, sludge

Description

SLUDGE DISCHARGING METHOD IN PICKLING EQUIPMENT FOR MANUFACTURING ORIENT ELECTRICAL STEEL SHEET}

1 is a process chart showing a general oriented electrical steel sheet manufacturing process,

Figure 2 is a graph showing the rate of precipitation of SiO ₂ in the hydrochloric acid circulation tank during the general manufacturing process,

3 and 4 are schematic diagrams showing the configuration of an apparatus for explaining the present invention.

♧ description of the symbols for the main parts of the drawing ♧

10..Sedimentation tank 12 ....

14 .... Shut-off valve 16 .... Industrial water piping

18 .... Open / close valve

The present invention precipitates silica sludge remaining in an acid solution in the course of pre-annealed and shot blasted (Shot Blaster) treated with hydrochloric acid in order to produce an electric steel sheet with a beautiful surface before cold rolling. It relates to a sludge discharge method in pickling equipment for producing oriented electrical steel sheets that controls the specific gravity so that they can be discharged smoothly at an appropriate time before solidification.

As is well known, oriented electrical steel sheets mainly used in motors and transformers are in weight percent, with C: 0.046 to 0.058, Si: 3.0 to 3.3, Mn: 0.09 to 0.12, Cu: 0.02, and Sol-Al: 0.027. It is a steel plate made into.

Such a grain-oriented electrical steel sheet is a pre-annealing step (2), descaling step (3), pickling step (4) and winding step (5) after the steel sheet (strip) is supplied from the material supply equipment (1) as shown in FIG. It is manufactured through.

At this time, in order to evenly distribute the inhibitor (Inhibitor) in the hot-rolled material is subjected to an annealing process for 60 seconds in the crack zone of 900 ℃ past the heating zone of the maximum temperature 1100 ℃ before cold rolling.

By gradually cooling after coiling in the annealing process to 580 ℃ during hot rolling, there is presented a dense scale layer on the surface of the steel sheet form, magnetite (Fe ₃ O ₄₎ and hematite (Fe ₂ O ₃₎ is a main component of the scale layer has a high temperature annealing process Is reduced to Wistatite (FeO) at.

In addition, after cooling to 750 ° C. in the air-cooling zone at the end of the annealing furnace, it is quenched to room temperature by water spray. At this time, since the quenching takes place in a short time, most of the reduced Wistatite (FeO) layer remains without oxidation to room temperature. The pickling layer forms a scale layer that is easy to pickle, and the Wistatite (FeO) layer is easily peeled off, and the peeling occurs only by a difference in cooling rate between the steel sheet and the scale layer.                         

There are two ways to descale the scale layer advantageously past the annealing furnace into a state suitable for cold rolling.

One of them is the mechanical method of spraying the 0.6mm shot ball accelerated by the turbine on the surface of the steel sheet to physically remove the scale. In this case, the removal of the scale is the rotational speed of the turbine, the projected amount of the shot ball, etc. It can be controlled by adjusting the surface roughness and the degree of scale removal.

The other method is to chemically remove 18% of hydrochloric acid by chemically supplying the pickling tank which reacts with the iron plate and reacting with fine residual scales which have not been removed by mechanical method.

FeO + 2HCl → FeCl ₂ + H ₂ O ------- (1)

In order to obtain excellent magnetic properties, the grain-oriented electrical steel sheet contains about 3% of the Si component, which is the most effective alloy component for increasing the resistivity, and thus has the advantage of being able to produce a product having low iron loss and good magnetic properties.

On the other hand, the Si component in the steel remains in the acid solution during the chemical reaction between the hydrochloric acid and the oxide layer, which acts as a detrimental factor for the sludge deposition in the pickling facility.

That is, some of the Si components in the steel are present as Fe ₂ SiO ₄ under the surface oxide layer (Fe ₂ O ₃ , Fe ₃ O ₄ , FeO), and the oxide layer is formed by chemical reaction with hydrochloric acid as shown in Equation (1). During the removal process, the Fe ₂ SiO ₄ layer on the top of the iron is also reacted with hydrochloric acid.

At this time, iron (Fe) reacts with hydrochloric acid to form iron chlorides (FeCl _2, FeCl ₃ ), but the chemically stable SiO ₂ component does not react and remains in the hydrochloric acid solution.

The SiO ₂ component has a particle size range of 0.3 ~ 100㎛ and precipitates and solidifies in the circulation system as the hydrochloric acid solution circulates over time, forming a sludge layer in the tank or clogging the pipe. Is shown graphically in FIG. 2.

In particular, when stopped due to periodic maintenance or equipment problems, the amount of precipitation is increased. Therefore, the sludge layer deposited in the circulation tank is removed by periodic cleaning every two to three months to prevent clogging problems.

In addition, there is a high concentration of hydrochloric acid harmful to the human body in the acid tank, so the work to remove the sludge layer is to be urgently solved in terms of improving the working environment.

In the existing hydrochloric acid circulation system, a separate settling tank circulated a certain amount of acid solution and settled in the settling tank to remove SiO ₂ , but there was no way to check the SiO ₂ deposition status in the circulating tank. It was discharged every time.

Furthermore, since the sludge deposition condition depends on the treated steel grade and line conditions, if the operator's experience is too short, excessive thin sludge discharge causes hydrochloric acid loss, and if the time is too long, the precipitated sludge component hardens and discharges. There was a disadvantage that became difficult.                         

In addition to the sedimentation method, there are SRP, centrifugal separation, and micro-filter method for removing SiO ₂ , but since SRP facility uses neutralization method using ammonia, it is not applicable to pickling facilities that require 18% hydrochloric acid. The centrifugal separation method, the method using a micro filter, etc. are not used for performance.

The present invention was created to solve this in consideration of the limitations of the prior art as described above, by installing a gamma ray in the lower portion of the sedimentation tank, detecting the change in specific gravity in the sedimentation tank to check the sludge sedimentation state with time in the cab When reaching a certain value, the pump in the rear stage is started and discharged to automatically discharge the sludge online without operator's intervention to prevent the blockage of pipes due to deposition and to prevent sludge hardening through periodic automatic discharge. The purpose is to provide a sludge discharge method in the pickling equipment for producing oriented electrical steel sheet is easy to maintain, repair and clean the facility because the frequency of hydrochloric acid is reduced.

In order to achieve the above technical problem, the specific gravity of the sludge precipitated through the specific gravity meter consisting of a light emitting unit for emitting a gamma ray and a light receiving unit for receiving a gamma ray installed in the bottom discharge pipe of the precipitation tank in the pickling facility When the measured sludge has a specific gravity of 1.55 to 1.70, the shutoff valve provided on the discharge line is opened and the pump is driven to discharge treatment, and the sludge discharge period is controlled to 4 to 6 hours. It is characterized by providing sludge discharge method in pickling equipment for manufacturing electrical steel sheet.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

3 and 4 are device configuration diagrams for explaining the present invention.

As shown in Figure 3 to 4, the specific gravity measuring instrument 12 consisting of the light emitting portion 12a and the light receiving portion 12b is provided on the lower discharge pipe of the settling tank 10, the shut-off valve on the pipeline directly below 14 is provided, and the industrial water pipe 16 is provided under the opening / closing valve 18 at the rear end thereof.

In addition, a discharge pump (P) is installed at the lower end of the discharge pipe connected to the industrial water pipe (16).

In addition, it is preferable that the specific gravity measuring device 12 uses gamma ray.

According to the present invention having such an arrangement, a grain-oriented electrical steel sheet is manufactured through a process as illustrated in FIG. 1, in which the mechanical scale is removed from the shot blaster after preliminary annealing and 4.5 μm remains on the surface. 18% hydrochloric acid is fed to the hydrochloric acid circulation tank to remove less scale layers.

In this case, the acid solution reacts in the pickling tank in the circulation tank and is combined with the low concentration of recovered acid containing a large amount of SiO ₂ to have a concentration of 8 to 15% for each circulation tank.

In this process, in order to remove SiO ₂ deposits generated during the reaction, a separate circulation line is formed from the circulation tank toward the SiO ₂ removal device, thereby continuing to remove SiO ₂ on-line.

In addition, in a large sedimentation tank capable of securing a constant deposition time in the SiO ₂ removal apparatus, SiO ₂ itself can be precipitated by specific gravity difference, but it is preferable to add a settling agent to enhance the precipitation effect. .

The settling agent may be divided into a solution type and a powder type, in which the solution type is diluted with a 10% solution to 6.85ℓ / hr, and the powder type is diluted with a 0.05% solution to 8.22ℓ / hr give.

At this time, the effect of the settling agent is most effective at 60 ℃ or less.

Thus, the SiO ₂ -containing acid solution flowing into the settling tank is settled to the bottom with sufficient settling time until recovered to each circulation tank through the overflow line in the tank.

Precipitated SiO ₂ is accumulated from the top of the shut-off valve (14) at the bottom, and the specific gravity change of the sludge is measured through the gamma ray specific gravity measuring instrument (12).

When the specified specific gravity change occurs, sludge is discharged. At this time, after the sludge is discharged, the sludge remaining in the discharge pipe can be completely pushed out to the pit by flushing through the industrial water pipe 16. Will be.

Thus, the residue is cured on the discharge duct to prevent closing the discharge duct.

Particularly, in the position immediately above the shutoff valve 14, water is accumulated to allow a certain portion of water to be discharged from the end immediately after the gamma ray specific gravity measuring instrument 12 and to maintain the function of the specific gravity measuring instrument 12. More preferred.

When the sludge is discharged through the above-described process, the optimum conditions for the use of the gamma ray specific gravity measuring instrument 12 are found through the comparative examples of Tables 1 and 2 below to achieve the most efficient discharge according to the specific gravity of the sludge.

At this time, the hydrochloric acid concentration, residual Si, and hydrochloric acid consumption in the sludge varying according to the measurement specific gravity and discharge time detected by the gamma ray specific gravity measuring instrument 12 are shown in Table 1 and Table 2.

In addition, the determination condition was to find the most effective condition by the residual Si concentration and hydrochloric acid consumption in the solution overflowed in the Si removal equipment and recovered to the pickling tank according to the discharge cycle.                     

In the results according to the discharge cycle of Table 1, in the case of Comparative Example 1, the specific gravity is still low and dilute, excessive consumption of hydrochloric acid, while the residual Si in the recovered hydrochloric acid solution was low.

In Comparative Example 2, when the cycle was increased to 8 hours, the hydrochloric acid consumption slightly decreased, but the residual Si rapidly increased, indicating that the SiO 2 removal effect was insufficient.

However, Inventive Example 1 showed that the discharge cycle was 4 hours, while the residual Si was kept low while reducing the amount of hydrochloric acid, while Inventive Example 2 was increased when the cycle was increased to 6 hours. Although slightly increased, the consumption of hydrochloric acid decreased considerably.

Conventional example is a value measured by taking a sample without the specific gravity measuring instrument 12, it was poor compared to the invention example.

In conclusion, it was found that Inventive Examples 1 and 2, which can manage low residual Si and low hydrochloric acid consumption, are better than the conventional examples and Comparative Examples 1,2.

In the case of Table 2, when the specific gravity value is measured by the specific gravity of gamma ray, when the specific gravity value is 1.55 or less, the amount of hydrochloric acid is excessively increased as in Comparative Example 1, and when the specific gravity value is 1.70 or more, the residual Si increases rapidly. The trend is to

Therefore, it can be judged that Inventive Example 1 and 2 which have a preferable range of residual Si and hydrochloric acid consumption are suitable conditions.

As described in detail above, according to the present invention, the specific gravity of SiO ₂ sludge measured by gamma ray is controlled at 1.55 to 1.70, and the sludge discharge cycle is 4 to 6 hours to solve the problem of clogging of pipes and nozzles. It ensures the surface quality and provides the effect of protecting workers from toxics.

Claims (2)

When manufacturing oriented electrical steel sheet, In the pickling facility, the specific gravity of the sludge deposited is measured by a specific gravity meter consisting of a light emitting part emitting a gamma ray and a light receiving part receiving a gamma ray installed on the lower discharge pipe of the sedimentation tank, and the measured specific gravity of the sludge is 1.55 to 1.70. Sludge discharge from pickling equipment for producing oriented electrical steel sheet, characterized in that to open the shut-off valve provided on the discharge pipe at the same time to drive the pump discharge treatment, the discharge cycle of the sludge is controlled 4 to 6 hours Way. The method according to claim 1, After the sludge is discharged, the sludge is discharged from the pickling facility for manufacturing a grain-oriented electrical steel sheet further comprising the step of flushing the industrial sludge using industrial water through an industrial water pipe connected to a lower portion of the shutoff valve on the discharge line. Way.

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