KR101964801B1 - Red Mud Ceramics and Manufacturing Method Thereof - Google Patents

Abstract

The present invention relates to red mud ceramic comprising red mud and a manufacturing method thereof and, more specifically, to red mud ceramic without chlorosis and a manufacturing method thereof. The method for manufacturing red mud ceramic comprises the following steps: molding a composition comprising red mud, clay mineral, waste crushed stone sludge, an inorganic coupler and a chlorosis reducing agent and manufacturing a molded article; and sintering the molded article. The red mud ceramic can provide a ceramic material having excellent strength while applying the high content of red mud which is generated as industrial by-products without cement or concrete.

Description

Red Mud Ceramics and Manufacturing Method Thereof}

The present invention relates to a red mud ceramic comprising a red mud and a method of manufacturing the same. In addition, the present invention relates to a red mud ceramic and a method of manufacturing the same, which does not cause whitening.

Red mud is an industrial by-product from the process of producing aluminum hydroxide (Al (OH) ₃ ) and aluminum oxide (Al ₂ O ₃ ) from bauxite raw minerals. In Korea, aluminum hydroxide is extracted by a Bayer method, that is, a method of extracting aluminum hydroxide by adding sodium hydroxide to a raw mineral containing a large amount of alumina, and the remaining sludge is called a red mud. It is called a scarlet clay and is discharged in a state of high viscosity sludge having a water content of about 30 to 50% by weight.

Red mud chemical compositions are mostly SiO ₂ , Al ₂ O ₃ and Fe ₂ O ₃ , and due to Fe ₂ O ₃ , reddish-like color is expressed, which is commonly referred to as red mud. When red mud is used as a construction material It contains about 10.0% of Na ₂ O, which causes whitening. This is because sodium hydroxide (NaOH) is used as an extract during the extraction of aluminum from bauxite gemstones, and therefore, a large amount of unrecovered sodium hydroxide solution was present in the red mud as a residue. Indicates.

Red mud is being discharged over 120 million tons per year in sludge worldwide and over 40 million tons in dry powder, and the amount is increasing every year. Sludge red mud is discharged 200,000 tons per year in Korea, but there is no way to process red mud itself, so it is not only used in building materials, but also there is no fundamental treatment. In particular, the world's red mud loading place is not suitable, and the leachate spillage causes environmental problems such as damage to nearby crops and lives. Therefore, treatment of red mud sludge is urgently needed.

In addition, there is a research to manufacture plastics such as bricks using clay and waste, but there is a problem of whitening phenomenon in red mud, so red mud is used as a small amount of pigment and red mud is used as a main component. Research into the manufacture of ceramics is insignificant.

Korea Patent Registration Publication No. 10-1887089 (2018.08.03)

Disclosure of the Invention The purpose of the present invention is to provide a high-strength ceramic material using red mud as a waste resource without including cement or concrete.

In addition, the disclosure of the present invention is to provide a method for manufacturing an energy-saving ceramic by lowering the firing temperature than the conventional ceramic firing temperature, when manufacturing a ceramic, including red mud. It is an object to provide a high-strength ceramic material capable of firing at 800 to 1100 ° C., which is a conventional ceramic firing condition, and also capable of low temperature firing at 500 to 800 ° C.

In addition, the disclosure of the present invention is to provide a red mud ceramic material that can be applied to the actual building, such as red mud to suppress the occurrence of whitening phenomenon during the manufacture of the ceramic, so that aesthetic appearance does not occur.

One aspect of the present invention for achieving the above object is to prepare a molding by molding a composition mixed with red mud, clay mineral, waste stone sludge and inorganic binder; And

Firing the molding;

It provides a method of manufacturing a red mud ceramic comprising a.

In addition, one embodiment of the present invention 20 to 60% by weight of modified red mud neutralized to pH 6 to 8 by pretreatment of red mud sludge with a water content of 30 to 50% by weight with sulfuric acid, bottom ash 10 to 50% by weight, waste-rock sludge 1 It includes ~ 20% by weight and 10 to 40% by weight of kaolin, and provides a red mud ceramic prepared by low-temperature baking at a temperature of 500 ~ 800 ℃.

Red mud ceramic according to an aspect of the present invention may provide a ceramic material having high strength while applying a high content of red mud produced as an industrial by-product without including cement or concrete.

Red mud ceramic according to an embodiment of the present invention does not occur whitening, it is possible to low-temperature baking has an excellent effect on the production cost and energy savings.

One aspect of the present invention can provide a high value-added up-cycling technology since the red mud, which is an industrial by-product, can be utilized in a large amount unlike the technology used as a material such as a conventional pigment.

In addition, natural clay, such as kaolin, clay, and feldspar, which are used for manufacturing ceramics, is depleted, and red mud is used as an alternative raw material to replace natural clay, thereby saving natural clay.

Red mud ceramic according to an aspect of the present invention has an effect that can be applied to brick, cement, sanitary ware, glass, tiles, building ceramics represented by refractory.

DETAILED DESCRIPTION Hereinafter, the present invention will be described in more detail with reference to the accompanying examples or embodiments. However, the following specific examples or examples are only one reference for describing the present invention in detail, but the present invention is not limited thereto and may be implemented in various forms.

Also, unless defined otherwise, all technical and scientific terms have the same meanings as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used in the description in the present invention are only for effectively describing specific embodiments and are not intended to limit the present invention.

Also, the singular forms used in the specification and the appended claims may be intended to include the plural forms as well, unless the context clearly indicates otherwise.

One aspect of the present invention comprises the steps of preparing a molding by molding a composition mixed with red mud, clay mineral, waste-rock sludge and inorganic binder; And

Firing the molding;

It provides a method of manufacturing a red mud ceramic comprising a.

The inorganic binder may be any one or a mixture of two or more selected from bottom ash, fly ash and paper ash, and the like, but is not limited thereto.

The clay minerals may be any one or a mixture of two or more selected from clays, kelp clays, red clays, kaolins, diatomaceous earths, loess, volcanic earth and clay, but are not limited thereto.

The composition may further include a bleach reducing agent which is any one or a mixture thereof selected from coffee grounds and ground coffee beans.

The coffee grounds may be obtained by drying the coffee grounds remaining after extracting coffee from the ground coffee beans.

In addition, the coffee grounds may be obtained by baking after the drying.

The composition may further include water glass.

The red mud may be a red mud sludge having a water content of 30 to 50 wt%.

The red mud may be to use a modified red mud neutralized to pH 6 to 8 by pre-treating the red mud sludge with a water content of 30 to 50% by weight with sulfuric acid.

The firing may be a low-temperature firing at a temperature of 500 ~ 800 ℃.

The composition may be a mixture of 20 to 60% by weight red mud, 10 to 50% by weight bottom ash, 1 to 20% by weight waste stone sludge and 10 to 40% by weight kaolin.

The composition may further comprise 0.1 to 30% by weight of a bleach reducing agent which is any one or a mixture thereof selected from coffee grounds and ground coffee beans.

The composition may further comprise 5 to 20% by weight of water glass.

One aspect of the present invention is a red mud ceramic manufactured by the manufacturing method according to the above aspect.

Specifically, one embodiment of the present invention 20 to 60% by weight of modified red mud neutralized to pH 6 to 8 by pretreatment of red mud sludge with water content of 30 to 50% by weight with sulfuric acid, bottom ash 10 to 50% by weight, waste-rock powder 1 to 20% by weight of sludge and 10 to 40% by weight of kaolin, and provides a red mud ceramic prepared by low-temperature baking at a temperature of 500 ~ 800 ℃.

The red mud ceramic may further include 0.1 to 30% by weight of a whitening agent, which is one selected from coffee grounds and ground coffee beans or a mixture thereof.

The red mud ceramic may further include 5 to 20% by weight of water glass.

Hereinafter, each configuration of the present invention will be described in more detail.

First, the red mud ceramic according to one embodiment of the present invention may include red mud, clay mineral, waste-rock sludge and inorganic binder.

More specifically, the red mud may be 20 to 60% by weight, inorganic binder 10 to 50% by weight, 1 to 20% by weight of waste-rock sludge and 10 to 40% by weight of clay minerals.

In addition, if necessary, the whitening agent may further include 0.1 to 30% by weight or 5 to 20% by weight of water glass.

In one embodiment of the present invention, the red mud is obtained as an industrial by-product generated in the process for producing aluminum hydroxide (Al (OH) ₃ ) and aluminum oxide (Al ₂ O ₃ ) from the bauxite ore, the water content of 30 ~ Obtained in 50% by weight of sticky sludge. Therefore, it may be used without pretreatment such as separate drying, but if necessary, it may be used as semi-dried red mud sludge having a water content of 20% by weight or less or dry red mud powder having a water content of 10% by weight or less by performing drying. . However, it may be to use a red mud sludge having a water content of 30 to 50% by weight from the viewpoint of eliminating the increase in costs of drying.

In addition, since the red mud is an inactive component which is not activated at 900 ° C. or lower, firing at a high temperature of 1100 ° C. or higher is required for firing.

Therefore, in one aspect of the present invention may be to reduce the energy by lowering the firing temperature to enable low-temperature firing, for this purpose by using a modified red mud neutralized to pH 6 ~ 8 by pre-treating the red mud sludge with an acid component It may be. The acid component used in the pretreatment may be hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and the like, but preferably sulfuric acid. Pretreatment to pH 6 ~ 8 using sulfuric acid produces Na ₂ SO ₄ component, which acts as an alkali in the firing process, lowering the melting point to increase the efficiency of sintering, and as a melting point lowering agent and clarifier to lower the firing temperature. It is preferable because it can work. In addition, red mud modified by acid treatment can be safely applied as a building material because no harmful substances are detected as a result of heavy metal dissolution test.

That is, by using a modified red mud neutralized to pH 6 to 8 by pretreatment of red mud sludge having a water content of 30 to 50% by weight with sulfuric acid, low temperature firing can be performed at a temperature of 500 to 800 ° C.

In one embodiment of the present invention, the content of the red mud is not limited, but may be to use 20 to 60% by weight, more specifically 25 to 55% by weight, more specifically 30 to 50% by weight. Red mud ceramic excellent in strength in the above range can be prepared, and is preferable because it is suitable for producing a red-made ceramic material that is the color of the red mud.

In one aspect of the invention, the clay mineral may be any one or a mixture of two or more selected from clay, braze clay, red clay, kaolin, diatomaceous earth, ocher, volcanic earth and clay, etc., and mixed with red mud by using a double kaolin It is preferable because the red mud ceramic having excellent properties and excellent strength can be produced. The content of the clay mineral is not limited, but may be 10 to 40% by weight, specifically 15 to 35% by weight, more specifically 20 to 30% by weight, the red mud ceramic having excellent strength in the above range It is preferable because it can be done.

In one aspect of the present invention, the inorganic binder may be any one or a mixture of two or more selected from bottom ash, fly ash and paper ash, and the use of the bottom ash containing a large amount of unburned carbon content is unburned during firing Exothermic reaction through combustion of powdered carbon can save energy by lowering the firing temperature required for ceramic manufacturing. Bottom ash is also preferable because its constituents are mostly SiO ₂ and Al ₂ O ₃ , and thus can produce red mud ceramic with higher strength. The content of the inorganic binder is not limited, but may be 10 to 50% by weight, specifically 15 to 45% by weight, more specifically 20 to 40% by weight, lower the firing temperature in the above range, excellent strength Red mud ceramics are preferred since they can be produced.

In one aspect of the present invention, the waste-rock powder sludge is discharged as a large amount of sludge fine powder during the production of crushed fine aggregates in the quarries, waste-rock powder sludge is also generated as industrial waste, it is urgent situation of recycling. In one embodiment of the present invention, the red mud ceramic having excellent strength and low temperature firing can be produced by including the waste-rock powder sludge. The content of the waste-rock sludge is not limited, but may be to use 1 to 20% by weight, specifically 5 to 15% by weight, more specifically 7 to 10% by weight, excellent strength in the above range, low temperature A red mud ceramic capable of firing can be prepared.

In one aspect of the present invention, the bleach reducing agent may be used to prevent bleaching of the red mud, specifically, for example, may be any one or a mixture thereof selected from coffee grounds and ground coffee beans. have. The inventors of the present invention, as a result of using the liquid coffee was not able to achieve the effect of reducing whitening, but the extraction of the liquid coffee and adding the remaining coffee grounds confirmed that the whitening of the red mud is improved.

More specifically, the coffee grounds refers to those obtained by drying coffee grounds remaining after extracting coffee from the ground coffee beans. In addition, it is also possible to use pulverized coffee beans, but in contrast, it was confirmed that the improvement of the whitening phenomenon was further improved when using the one obtained by drying coffee residues remaining after extracting coffee from the pulverized coffee beans.

The drying is to remove the moisture of the coffee grounds remaining after extracting the coffee, and is not limited, but is dried at a temperature of 20 to 100 ℃, it is preferable to dry until the moisture content is less than 10%. Compared with the presence of water, the effect of reducing whitening can be further increased by drying until the moisture content is less than 10%.

In addition, after drying the coffee grounds, by performing the calcination, the whitening effect is excellent, and the powder degree can be increased to further increase the amount, and the organic matter can be reduced through calcination to prevent the strength of the construction body from being lowered. . The calcination is not limited but may be performed at 200 to 700 ° C., more specifically at 300 to 500 ° C. In addition, it may be performed for 1 to 10 hours, more specifically 2 to 8 hours.

The content of the whitening agent is preferably added in a range that does not inhibit the inherent physical properties of the red mud, the content is not limited but specifically, for example, 0.1 to 30% by weight in the composition, specifically 1 to It may include 25% by weight, more specifically 5 to 20% by weight, and sufficient whitening phenomenon occurs while preventing the strength deterioration during ceramic manufacturing without changing the inherent physical properties of the red mud in the above range The effect which prevents it can be achieved.

In one embodiment of the present invention, the water glass may be obtained by treating a silicon oxide polymer with sodium (Na) ions in a low pressure steam cooker by melting a mixture of silica sand and soda ash at 1300 ~ 1500 ℃. The strength of the ceramic can be further improved by adding steel water glass, and in particular, it is preferable because a slight decrease in strength due to the addition of the whitening agent can be eliminated. The content of the water glass is not limited, but may be to use 5 to 20% by weight, specifically 10 to 15% by weight, it is preferable because it is possible to manufacture a ceramic having excellent strength in the above range.

In one aspect of the present invention, the composition for producing the red mud ceramic may be to include water, it can be used without limiting the conventional additives used in the art as needed.

In one aspect of the invention, the red mud ceramic is prepared by molding the composition of the mixture of the red mud, clay mineral, waste-rock sludge and inorganic binder described above; And firing the molding.

More specifically, the red mud ceramic according to one aspect of the present invention

a) aging red mud, clay minerals, waste-rock sludge and inorganic binders in the open air for at least 6 months;

b) grinding and mixing the aged raw materials;

c) molding and drying the mixed composition; And

d) firing the dried molded body;

It may be prepared to include.

More specifically, the step of aging may be to ripen the raw materials for 6 months or more in the open air exposed to sunlight and wind. Through such a aging process, cracks can be prevented from occurring in the manufactured ceramic.

Next, the process of pulverizing the raw material may be to pulverize to have a crushing particle size that is easy to manufacture into a ceramic. The grinding method is not limited because it can use a commonly used method such as mill, roll. The particle size of the raw materials is not limited, but specifically, for example, 5 to 100 mesh, more specifically 10 to 80 mesh may be to be pulverized. By pulverizing in the above range it can have a strength and viscosity that can be produced from a ceramic.

Next is not limited to the process of mixing the raw materials to prepare a composition, but may be to mix in the content range described above. In addition, the ceramic may further include water to facilitate mixing.

Next, the molding step is a process of manufacturing a molding of a desired shape.

Next, the step of drying may be to dry for 1 to 10 days at 35 ~ 100 ℃ as a process for adjusting the moisture.

Next, the step of firing may be to prepare a ceramic by low-temperature baking the dried molding at a temperature of 500 ~ 800 ℃.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the following Examples and Comparative Examples are only examples for explaining the present invention in more detail, the present invention is not limited by the following Examples and Comparative Examples.

1) Whitening test

The whitening test specimens were prepared for 5 × 5 × 5 cm sized specimens and cured for 28 days at a temperature of 20 ° C. and a relative humidity of 60%. After 28 days of curing, the sides of the specimens were sealed with paraffin, and the specimens were immersed in distilled water for 14 days in a constant temperature and humidity chamber at a temperature of 7 ° C. and a relative humidity of 50%, and immersed up to 10 mm from the bottom of the specimens.

The area of whitening occurrence was quantified by photographing the degree of whitening after 14 days of immersion in the thermo-hygrostat and calculating the area of whitening with a “paintnet” program. 1 is a photograph of a test specimen in which bleaching occurred.

The whitening grade was divided into five grades according to the whitening occurrence area as shown in Table 1 below.

Department grade Whitening outbreak area ratio I No occurrence Ⅱ Less than 10% Ⅲ Less than 10%-30% Ⅳ Less than 30% ~ 50% Ⅴ 50% or more

2) compressive strength

The compressive strength of 28 days of age was measured according to KS L 5105. The unit is MPa

Hereinafter, the red mud sludge used in Examples and Comparative Examples was generated from KC Co., Ltd. located in Daebul Industrial Complex, Yeongam-gun, Jeollanam-do. The water content was 50% by weight and the pH was 11.

ingredient Content (wt%) SiO ₂ 38.8 Al ₂ O ₃ 16.1 Fe ₂ O ₃ 22.8 Na ₂ O 10.0 CaO 3.4 Etc 8.9

The coffee grounds were obtained by grinding coffee beans to extract liquid coffee and drying the remaining grounds at 50 ° C. for 24 hours.

As the calcined coffee grounds, calcined coffee grounds obtained as described above were used at 400 ° C. for 3 hours.

Example 1

Red mud was used without acid treatment of the red mud sludge of Table 2.

Raw materials aged for 6 months in the open air were mixed as shown in Table 3 to prepare a composition. With respect to 100 parts by weight of the prepared composition, 15 parts by weight of water was added to kneaded, and then put into a mold to prepare a molded product, and dried at 50 ° C. for 3 days to prepare a dried molded product.

Thereafter, the dried molded body was fired at a temperature of 600 ° C. for 1 hour to prepare a red mud ceramic.

To evaluate the physical properties of the prepared red mud ceramic is shown in Table 4 below.

[Examples 2 to 8]

Red mud ceramic was prepared in the same manner as in Example 1, except that the mixing ratio of the composition was changed as in Table 3 below. To evaluate the physical properties of the prepared red mud ceramic is shown in Table 4 below.

EXAMPLES 9-16

The red mud was immersed in sulfuric acid in the red mud sludge of Table 2 until the pH is 7, and the precipitate was filtered and washed with distilled water to use a red mud sludge having a water content of 50% by weight.

Red mud ceramics were manufactured in the same manner as in Examples 1 to 8, except that the type of red mud sludge was changed. To evaluate the physical properties of the prepared red mud ceramic is shown in Table 4 below.

[Comparative Examples 1 to 3]

A red mud ceramic was prepared in the same manner as in Example 1 except for changing the composition as shown in Table 3 below. To evaluate the physical properties of the prepared red mud ceramic is shown in Table 4 below.

Red Mud (% by weight) Bottom ash (% by weight) Waste Stone Sludge (wt%) Kaolin (% by weight) all sorts of flowers
Reducer
(weight%) Water glass (wt%) Before acid treatment After acid treatment Coffee grounds Fired coffee grounds Example 1 20 - 30 10 40 - - - Example 2 40 - 20 10 30 - - - Example 3 60 - 15 10 15 - - - Example 4 40 - 20 10 20 10 - - Example 5 40 - 20 10 20 - 10 - Example 6 35 - 20 10 20 - 15 - Example 7 40 - 20 10 20 - - 10 Example 8 40 - 20 10 20 - 10 10 Example 9 - 20 30 10 40 - - - Example 10 - 40 20 10 30 - - - Example 11 - 60 15 10 15 - - - Example 12 - 40 20 10 20 10 - - Example 13 - 40 20 10 20 - 10 - Example 14 - 35 20 10 20 - 15 - Example 15 - 40 20 10 20 - - 10 Example 16 - 40 20 10 20 - 10 10 Comparative Example 1 20 - - 10 70 - - - Comparative Example 2 20 - 30 - 50 - - -

Department grade Compressive strength (MPa) Example 1 Ⅳ 30 Example 2 Ⅳ 28 Example 3 Ⅳ 26 Example 4 Ⅱ 25 Example 5 Ⅱ 27 Example 6 I 25 Example 7 Ⅳ 28 Example 8 Ⅱ 27 Example 9 Ⅳ 32 Example 10 Ⅳ 30 Example 11 Ⅳ 29 Example 12 Ⅱ 27 Example 13 Ⅱ 28 Example 14 I 27 Example 15 Ⅳ 30 Example 16 Ⅱ 32 Comparative Example 1 Ⅳ 28 Comparative Example 2 Ⅳ 25

As shown in Table 4, when the fired body was manufactured using the red mud, the compressive strength was excellent. However, bleaching occurred, and it was confirmed that bleaching was reduced when coffee grounds were added. In addition, as shown in Examples 4 and 6, it was confirmed that the compressive strength is maintained despite using more content in Example 6 using calcined coffee grounds.

Claims (17)

Preparing a molding by molding a composition including red mud, clay mineral, waste stone sludge, inorganic binder, and whitening agent; And
Firing the molding;
Including;
The whitening agent is a method of producing a red mud ceramic is obtained by drying the coffee grounds remaining after the extraction of coffee from the ground coffee beans after drying. The method of claim 1,
The inorganic binder is any one or a mixture of two or more selected from bottom ash, fly ash and paper ash method of producing a red mud ceramic. The method of claim 1,
The clay mineral is red, clay, kaolin clay, red clay, kaolin, diatomaceous earth, loess, volcanic earth and clay, any one or a mixture of two or more selected from red clay ceramic manufacturing method. delete delete delete The method of claim 1,
The composition is a method of producing a red mud ceramic further comprising a water glass. The method of claim 1,
The red mud is a red mud ceramic manufacturing method of the red mud sludge having a water content of 30 to 50% by weight. The method of claim 8,
The red mud is a method of producing a red mud ceramic using a modified red mud neutralized to pH 6 to 8 by pretreatment of red mud sludge with a water content of 30 to 50% by weight with sulfuric acid. The method of claim 9,
Firing of the molded product is a method of producing a red mud ceramic is baked at a low temperature of 500 ~ 800 ℃. The method of claim 1,
The composition is 20 to 60% by weight red mud, 10 to 50% by weight bottom ash, 1 to 20% by weight waste stone sludge, 10 to 40% by weight kaolin and 0.1-30% by weight reduction agent red mud Method of manufacturing ceramics. delete The method of claim 11,
The composition is a method of producing a red mud ceramic containing 5 to 20% by weight of water glass. Red mud ceramic produced by the method of any one of claims 1 to 3, 7 to 11 and 13 selected from. 20 to 60 wt% of modified red mud neutralized to pH 6 to 8 by pretreatment of red mud sludge with water content of 30 to 50 wt%, bottom ash 10 to 50 wt%, waste stone sludge 1 to 20 wt% and kaolin 10 Red mud ceramic containing ~ 40% by weight, prepared by low-temperature baking at a temperature of 500 ~ 800 ℃. The method of claim 15,
The red mud ceramic is red mud ceramic further comprises 0.1 to 30% by weight of any one or a mixture thereof selected from coffee grounds and ground coffee beans. The method of claim 15,
The red mud ceramic is red mud ceramic further comprises 5 to 20% by weight of water glass.