KR102380531B1 - Method for manufacturing MgO-Cr2O3 based Seawater Magnesia Clinker - Google Patents

Abstract

MgO-Cr ₂ O ₃ Seawater magnesia clinker manufacturing method is provided.
Seawater magnesia clinker manufacturing method of the present invention, a process of preparing a synthetic magnesium hydroxide [Mg(OH) ₂ ] slurry from seawater; A process of adding Cr ₂ O ₃ additives to the synthetic magnesium hydroxide slurry in an amount of 0.1 to 2% by weight and then mixing; and a process of preparing a MgO-Cr ₂ O ₃ based seawater magnesia clinker by drying the mixed synthetic magnesium hydroxide slurry and then calcining at a temperature of 1800 to 2000°C.

Description

MgO-Cr2O3-based seawater magnesia clinker manufacturing method {Method for manufacturing MgO-Cr2O3 based Seawater Magnesia Clinker}

The present invention relates to the manufacturing technology of seawater magnesia clinker prepared after synthesizing Mg(OH) ₂ from seawater rather than sintering (dead burned) of natural Mganesite among magnesia (MgO, magnesia) raw materials, which are the main raw materials of basic refractories. it's about

The main raw material for basic refractories widely used in the iron & steel making industry is magnesia (MgO) raw material. It can be divided into two methods: a method of obtaining it by sintering, and a method of starting from seawater, synthesizing it in the form of Mg(OH) ₂ , and then calcining it at a high temperature of 1800° C. or higher to obtain sintered MgO. In general, these two are divided into natural sintered MgO and synthetic seawater MgO.

In the case of natural products, they are sold in various forms, from low-end products with MgO content of 90% to 98% or more, and high-priced MgO by electric fused rather than sintering. production and supply is widely practiced.

These natural MgO raw materials have recently caused supply instability to domestic users due to supply and demand restrictions under the influence of China's environmental policy. In other words, supply and price are unstable due to changes in China's internal policy, and the domestic refractory industry, which has a strong dependence on resources for foreign refractory materials, is trying to solve it through various channels to devise ways to secure raw materials.

Seawater magnesia manufacturing technology is currently being proposed as one way to break away from dependence on China's natural MgO refractory materials. This technology first synthesizes magnesium hydroxide (Mg(OH)2) through an ion exchange reaction of magnesium ions (Mg2+) in seawater (or seawater) with lime milk (Ca(OH)2), It is a method of obtaining sintered MgO through the drying-calcining-forming-calcining process. In the case of seawater sintered MgO, it is currently possible to manufacture up to a purity level of 98%, and the refractory materials used are different depending on the purity and physical properties (volume specific gravity, porosity). In the case of 95% grade, it is mainly applied to irregular refractories, and 98% grade is used for basic fired refractories. In the case of such seawater sintered MgO, technology development is underway to expand its use to more versatile uses through property modification.

In the case of basic fired refractories, natural sintered and electromelted MgO and seawater high specific gravity MgO are used as main raw materials, and spinel, Cr ₂ O ₃ based materials are used together depending on the conditions of the refractory material. In particular, amorphous refractories containing Cr ₂ O ₃ and basic calcined refractories are also applied to areas requiring long life, abrasion resistance and spalling resistance. For these refractories, it is common to use natural ore raw materials containing Cr ₂ O ₃ together with the main raw material or to mix and use Cr ₂ O ₃ for the purpose of high purity. In addition, some refractories use raw materials fused together with MgO and Cr ₂ O ₃ , but they are not put to practical use because they are applied to natural sintering or seawater magnesia clinker.

Therefore, the present invention has been devised to overcome the above-described limitations of the prior art, and utilizing facilities and processes for manufacturing seawater MgO, the MgO purity is maintained at 97.0% or more, and the bulk specific gravity is 3.25, which is 98% of commercial seawater MgO. It aims to provide a method of manufacturing Cr ₂ O ₃ containing seawater magnesia clinker (Cr ₂ O ₃ - Bearing Seawater MgO Clinker) with a porosity of 3% or less.

The object of the present invention is not limited to the above. Those of ordinary skill in the art to which the present invention pertains will have no difficulty in understanding the additional subject matter of the present invention from the general description of the present invention.

One aspect of the present invention is

A process for preparing a synthetic magnesium hydroxide [Mg(OH) ₂ ] slurry from seawater;

A process of adding Cr ₂ O ₃ additives to the synthetic magnesium hydroxide slurry in an amount of 0.1 to 2% by weight and then mixing; and

It relates to a seawater magnesia clinker manufacturing method comprising a; drying the mixed synthetic magnesium hydroxide slurry, and then calcining at a temperature of 1800 to 2000° C. to prepare a MgO-Cr ₂ O ₃ based seawater magnesia clinker.

It is preferable to add the SiO ₂ sintering aid in the range of 0.3 to 0.8 wt % to the magnesium hydroxide slurry.

When drying the magnesium hydroxide slurry, it is preferable to set the drying temperature to 300° C. or less.

The prepared MgO-Cr ₂ O ₃ based seawater magnesia clinker may have an apparent porosity of 3% or less, a bulk specific gravity of 3.29 to 3.32, and a crystal size of 150 μm or more.

The seawater magnesia clinker of the present invention manufactured using the above-described manufacturing process may have an apparent porosity of 3% or less, a bulk specific gravity of 3.29 to 3.32, and a crystal size of 150 μm or more.

Therefore, the seawater magnesia clinker can be applied to MgO _- Cr ₂ O ₃ system irregular refractory materials for repair that require corrosion resistance and wear resistance characteristics, and in some cases, life extension is required _. The advantage is that it is possible.

1 is a manufacturing process diagram for manufacturing a seawater magnesia clinker according to an embodiment of the present invention.
2 is a microstructure photograph observed through an optical microscope of Cr ₂ O ₃ containing seawater magnesia clinker according to an embodiment of the present invention.

Hereinafter, the present invention will be described.

The MgO-Cr ₂ O ₃ based seawater magnesia clinker of the present invention uses a synthetic magnesium hydroxide slurry formed in the process of preparing seawater magnesi clinker as a starting material, and is usually Cr ₂ O ₃ in the form of an additive in the filtration step of the slurry It can be prepared by adding a system additive, drying it, and then calcining it at a high temperature of 1800° C. or higher.

When a refractory material using seawater-synthesized MgO as a main raw material is required to have high abrasion resistance and improved lifespan depending on the usage conditions and parts, Cr ₂ O ₃ based auxiliary materials have been directly added and used. However, in the present invention, during the manufacturing process of the synthetic magnesia clinker from seawater rather than such direct addition, specifically, by adding some Cr ₂ O ₃ based additives to the synthetic magnesium slurry, MgO-Cr ₂ O ₃ based seawater magnesia clinker is manufactured. characterized in that

According to this, the MgO-Cr ₂ O ₃ method for producing a seawater magnesia clinker of the present invention includes a process of preparing a synthetic magnesium hydroxide [Mg(OH) ₂ ] slurry from seawater; A process of adding Cr ₂ O ₃ additives to the synthetic magnesium hydroxide slurry in an amount of 0.1 to 2% by weight and then mixing; and a process of preparing a MgO-Cr ₂ O ₃ based seawater magnesia clinker by drying the mixed synthetic magnesium hydroxide slurry and then calcining at a temperature of 1800 to 2000°C.

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

1 is a manufacturing process diagram for manufacturing a seawater magnesia clinker according to an embodiment of the present invention.

As shown in FIG. 1 , in the present invention, first, a synthetic magnesium hydroxide [Mg(OH) ₂ ] slurry is prepared from seawater. This synthetic magnesium hydroxide slurry is obtained by reacting carbonate-treated seawater with slaked lime [Ca(OH) ₂ ] slurry, which is obvious to those skilled in the art, and detailed description thereof will be omitted.

Next, in the present invention, after adding Cr ₂ O ₃ additives to the synthetic magnesium hydroxide slurry in an amount of 0.3 to 0.8 wt %, the mixture is mixed. And at this time, a SiO ₂ sintering agent may also be added.

_In the present invention, Cr ₂ O ₃ -based raw material is added to MgO refractory material in a certain range in order to improve _the lifespan and wear resistance of _the refractory material _. It is possible to use ₂ O ₃ raw materials as well as Cr ore with a Cr ₂ O ₃ content in the range of 44 to 60%.

On the other hand, in the present invention, the amount of the Cr ₂ O ₃ supplementary material added is preferably adjusted in such a way that the microstructure and characteristics of the raw material itself do not significantly deteriorate without significantly reducing the MgO purity of the original seawater magnesia clinker. Do.

In the present invention, the Cr ₂ O ₃ additive amount is preferably determined in the range of 0.1 to 2% by weight based on the synthesized magnesium hydroxide slurry. If the addition amount is less than 0.1% by weight, it does not affect the crystal size change in the microstructure. because it can In addition, it is not suitable for use because the quality of the refractory material is deteriorated due to an excessive increase in the pore size that is out of the appropriate content.

In addition, in the present invention, it is preferable to limit the content of the added SiO ₂ sintering aid to 0.6 to 1.2% by weight.

Subsequently, in the present invention, the mixed synthetic magnesium hydroxide slurry is dried.

When manufacturing Cr ₂ O ₃ containing seawater magnesia, it is necessary to easily manage the moisture at 8 to 12% during the molding process, and for this, the drying temperature is managed below 300℃, which is near the temperature just before the thermal decomposition of Mg(OH) ₂ Should be. At a temperature lower than this, it is difficult to manage moisture in the continuous manufacturing process, which causes equipment troubles, and it is difficult to obtain the desired physical properties of the raw material due to the decrease in the volume specific gravity of the final raw material and the increase in the porosity.

And in the present invention, by calcining the dried synthetic magnesium hydroxide slurry at a temperature of 1800 ~ 2000 ℃ MgO-Cr ₂ O ₃ To prepare a seawater magnesia clinker.

In order to produce the final Cr ₂ O3 containing seawater magnesia raw material, a firing process is required, and in order to maintain the bulk specific gravity of 3.25 g/cm 3 required for the refractory raw material, the calcination temperature must be maintained at at least 1800 ° C. If it is less than that, the growth of the periclase phase, which is a magnesia crystal phase, is insufficient, thereby lowering the volume specific gravity of the final raw material, and excessive shrinkage when applied to refractory products may cause problems or reduce the lifespan.

The seawater magnesia clinker of the present invention manufactured using the above-described manufacturing process may have an apparent porosity of 3% or less, a bulk specific gravity of 3.29 to 3.32, and a crystal size of 150 μm or more.

Hereinafter, the present invention will be described in more detail through examples.

(Example 1)

Using a synthetic magnesium hydroxide (Mg(OH) ₂ ) slurry as a starting material, as shown in Table 1 below, the manufacturing conditions were obtained when Silica (SiO ₂ ), a conventional sintering aid, was added to the slurry and when only Cr ₂ O ₃ was added. Differently, seawater magnesia clinker was manufactured, and after calcination in a laboratory rotary corrosion tester, the volume specific gravity and porosity change were compared after classification to 5~3mm.

In Table 1 below, Conventional Example 1-2 is the evaluation result of the clinker properties after firing when only SiO ₂ , which is the existing sintering aid, is added to the synthetic magnesium hydroxide slurry, and Inventive Example 1-3 is the case of adding Cr ₂ O ₃ These are the results of evaluation of the physical properties of the clinker after firing. And Inventive Example 4 is a result of evaluation of physical properties when SiO ₂ and Cr ₂ O ₃ are added together

division Conventional example 1 Conventional example 2 Invention Example 1 Invention example 2 Invention example 3 Invention Example 4 control
factor SiO ₂ addition amount
(weight%) 0.5 One 0.5 Cr ₂ O ₃ addition amount
(weight%) 0.1 0.3 0.5 0.5 clicker
characteristic importance 3.12 3.20 3.24 3.27 3.30 3.31 Porosity (%) 5.8 4.2 3.3 3.2 2.8 2.4

As shown in Table 1, in the case of Inventive Examples 1-3 in which Cr ₂ O ₃ was added to the synthetic magnesium hydroxide slurry, it can be confirmed that the volume specific gravity increased and the porosity decreased even when a small amount was added. In addition, in the case of Inventive Example 4 in which SiO ₂ and Cr ₂ O ₃ additive were added in combination, it can be seen that similar results to that when 0.5% of Cr ₂ O ₃ was added can be obtained.

On the other hand, Conventional Example 1-2 in which SiO ₂ , which is a conventional sintering aid, was added to the synthetic magnesium hydroxide slurry had the same tendency, but increased bulk specific gravity and reduced porosity compared to Inventive Example 1-4 in which Cr ₂ O ₃ was added. It can be seen that low

(Example 2)

Table 2 below is a comparison result of what kind of results are shown when raw materials corresponding to Conventional Example 1 and Inventive Example 3-4 of Example 1 are manufactured in a rotary kiln, which is an actual seawater magnesia clinker manufacturing facility.

Conventional example 1 Invention example 3 Invention Example 4 control factor SiO ₂ addition amount (wt%) 0.5 0.5 Cr ₂ O ₃ addition amount (wt%) 0.5 0.5 Clicker Characteristics importance 3.32 3.31 3.31 Porosity (%) 1.9 2.1 2.0 MgO (%) 97.9 97.8 97.4

As shown in Table 2 above, in the case of actual on-site manufacturing, the results were not the same as those of the results of firing under the laboratory conditions of Example 1, but showed similar results. Specifically, in the case of the single addition of Cr ₂ O ₃ or the combined addition of Cr ₂ O ₃ and SiO ₂ , the bulk specific gravity is similar to that of Conventional Example 1, and the purity of MgO is maintained almost the same when only Cr ₂ O ₃ is added, and Cr When ₂ O ₃ and SiO 2 were added together, a slightly lowered result was obtained. On the other hand, the content of the additive was based on 0.5% by weight, and the purity decrease due to the additive was added at a level to maintain the MgO purity of 97.2% or more, and as a result, all of 3.3 or more of the sinus volume could be maintained. As shown in FIG. 2, it is estimated that this result is due to the large growth of the crystal size to 150 μm, and the growth of the crystal size and the reduction of the grain boundary affect the wear resistance and corrosion resistance effects, as will be described later. can affect

(Example 3)

According to Example 2, MgO-Cr 2 O 3 seawater magnesia clinkers for MgO-Cr ₂ O ₃ based refractories of Inventive Examples 3-4 and Conventional Example 1 were respectively prepared. And after manufacturing a refractory material using the manufactured magnesia clinker as a main raw material of the irregular refractory material, the corrosion resistance and abrasion resistance were evaluated, and the results are shown in Table 3 below. In this experiment, for comparison, when the wear resistance and corrosion resistance of Conventional Example 1 were set to 100, respectively, the results of comparative evaluation of the corrosion resistance and wear resistance of Inventive Example 3-4 are shown in Table 3 below.

division Invention example 3 Invention Example 4 Conventional example 1 Refractory properties wear resistance 105 107 100 corrosion resistance 103 102 100

As shown in Table 3, Inventive Example 3 in which Cr ₂ O ₃ was added alone as an auxiliary material, and Inventive Example 4 in which Cr ₂ O ₃ and SiO ₂ were added in combination, seawater magnesia clinker was used as a main raw material to form an irregular shape. When the refractory material is manufactured, it can be confirmed that the result of similar or slightly increased corrosion resistance and abrasion resistance compared to Conventional Example 1 can be obtained.

As described above, in the detailed description of the present invention, preferred embodiments of the present invention have been described, but those of ordinary skill in the art to which the present invention pertains may make various modifications without departing from the scope of the present invention. Of course, this is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims to be described later as well as equivalents thereof.

Claims (4)

A process for preparing a synthetic magnesium hydroxide [Mg(OH) ₂ ] slurry from seawater;
To the synthetic magnesium hydroxide slurry, Cr ₂ O ₃ additive material: 0.1 to 2% by weight and SiO ₂ sintering aid: a step of mixing after adding each in the range of 0.3 to 0.8% by weight; and
MgO-Cr _{2 O 3 based seawater magnesia clinker including; drying the mixed synthetic magnesium hydroxide slurry, and then calcining at a temperature of 1800 to 2000° C. to produce a MgO-Cr 2 O 3 based seawater} magnesia clinker manufacturing method.
(Here, the weight % is, in the synthetic magnesium hydroxide slurry, Cr ₂ O ₃ -based auxiliary material and SiO ₂ sintering aid are mixed with respect to the total weight of the synthetic magnesium hydroxide slurry Cr ₂ O ₃ -based auxiliary material and SiO ₂ sintering aid, respectively refers to the weight ratio of
delete [Claim ₃ ] The method of claim 1, wherein the drying temperature of the magnesium hydroxide slurry is set to ₃₀₀ ° C. or less.
The MgO-Cr 2 according to claim 1, wherein the prepared MgO-Cr ₂ O ₃ seawater magnesia clinker has an apparent porosity of 3% or less, a bulk specific gravity of 3.29-3.32, and a crystal size of 150 μm or more _. O ₃ seawater magnesia clinker manufacturing method.

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