KR101740599B1 - Method of Preparing Artificial Light-Weight Aggregates - Google Patents

Abstract

The present invention relates to a method of coating a material composed of a ceramic oxide raw material and coating it with a coating material composed of silica, limestone and dolomite after coating with a coating material having a different range of particle size depending on the particle size of the object, The present invention relates to a method for producing an artificial lightweight aggregate for producing a uniform foamed aggregate.

Description

TECHNICAL FIELD The present invention relates to a method for preparing an artificial lightweight aggregate,

The present invention relates to a method for manufacturing an artificial lightweight aggregate, and more particularly, to a method for manufacturing an artificial lightweight aggregate, which comprises forming and classifying a material composed of a ceramic oxide material, coating the material using a coating material composed of silica, limestone and dolomite, The present invention relates to a method for producing an artificial lightweight aggregate, which is produced by uniformly foaming an aggregate material by coating with a coating material having a particle size of 50 to 500 m < 2 >

Fly ash discharged from thermal power plants is divided into fly ash and bottom ash according to the characteristics. In Korea, annual fly ash is 6.84 million tons and flooring is 1.15 million tons (YD Jo, "Electric Industry and Environmental Effect "pp. 343-352 in Korea Electric Association, Electricity Almanac, Seoul, 2009). Fly ash is mostly recycled because it has fine particle size and excellent composition. It is said that rejected ash because of its large carbon content and large particle size can not be recycled, and it is being processed by landfill (KD Kim, "A Study on Application and Fabrication of Functional Ceramics for Ecofriendly Waste Recycling Process ", pp. 25-35, Ph. D. Thesis, Kyonggi University, Suwon, 2010.). In recent years, studies have been actively carried out on the production of stable artificial lightweight aggregate by treating coal fly ash of the thermal power plant in Korea in an environmentally friendly manner. This study has the advantage of providing environmentally conservation effect and high-performance artificial lightweight aggregate to the construction and environment field at low cost when the economic result is obtained (SD Kang, "A study on manufacturing of autoclave lightweight concrete with fine sludge Crystal Growth and Crystal Technology, "J. K.," Development of Artificial Lightweight Aggregates Using Coal Bottom as Ash and Clay, "J. Kor. Institute of Mineral and Energy Resources Engineer, 35 (1998) JH Lee, JH Shim, JH Kim, SP Kang, SJ Choi and MH Kim, "A study on the strength properties of concrete containing bottom ash as part of fine aggregate", J. Architectural.

Generally, in the production of artificial lightweight aggregate, a direct method of putting an aggregate molding directly into a furnace heated to a sintering temperature is used. The cross-sectional structure of the aggregate produced therefrom includes a so-called black core (black core) And a shell of red color surrounding it. However, the artificial aggregate foamed by the black core mechanism has a disadvantage in that the pore size in the black core and the pore size in the shell are different from each other, and the pore size distribution of the entire specimen is not uniform. Further, when the black core portion is excessively developed, cracks may be generated on the surface of the aggregate, and the black core portion may be exposed to the outside, resulting in nonuniformity of the aggregate shape and decrease in strength (CR Austin, JL Nunes and JD Sullivan, "Basic Quot; Black Corings in Structural Clay Products ", J. Am. Ceram., Vol. 14, pp. 1-11 (1942); Soc., 40 [6] 179-87 (1957); CM Riley, "Relation of Chemical Properties to the Bloating of Clays", J. Am. Ceram. Soc., 34 [4] 121-28 (1951). .

In recent years, MA Kang et al. Have proposed a method of producing artificial lightweight aggregate using a so-called elevated temperature method, in which the aggregate is gradually heated from the carbon oxidation temperature as a raw material, thereby forming a black core and having a uniform pore size and distribution (Kang, SG Kang, GG Lee and YT Kim, "Fabrication of Artificial Light-Weight Aggregates of Uniform Bloating Properties Using a Temperature homogeneously-bloated aggregates by the temperature elevation method can be obtained by mixing the aggregates prepared by the black core mechanism with the aggregate of the aggregate (s) The sintering temperature is slightly higher than that of the specimen. Therefore, the amount of liquid phase formed on the surface of the specimen is increased to such a degree that the so-called fusion phenomenon is likely to occur between the aggregates.

Generally, artificial lightweight aggregate is manufactured using rotary kiln. The fusion of aggregate causes aggregate mass in the rotary kiln, which makes it difficult to mass-produce, and even if the kiln is blocked, operation may be stopped. Therefore, it is very important to solve the fusion problem in the case of a composition in which a large amount of liquid phase is generated on the aggregate surface, but a literature suggesting a solution to this problem is not disclosed yet.

In addition, research on artificial lightweight aggregate mainly relates to weight reduction by foaming, and the foaming behavior is that the gas generated by the reduction action of iron due to the oxidation reaction of carbon induces expansion of the substrate to lighten it. Lee (KGLee, "Bloating mechanism for coal ash with iron oxide", J. Korean Cryst. Growth Cryst. Technol. 24 (2014) 77) (SHKang, KGLee, YTKim, SGKang, "Effects of chemilophysical properties of carbon on bloating characteristics using artificial lightweight aggregates using coal ash ", Advances in " Sintering Science and Technology Ⅱ., 232 (2011) 35) analyzed the effect of type and content of C on the generation of foaming gas in the production of artificial lightweight aggregate by recycling fly ash. In case of adding small amount of carbon, The amount required for production is not sufficient, and when a high content of carbon is added, surface densification is hindered and it is difficult to reduce the weight. In addition, Tsai et al. (Chen-Chiu Tsai et al., "Effect of SiO ₂ -Al ₂ O ₃ -flux ratio change on the bloating characteristics of lightweight aggregate material produced from recycled sewage sludge", J. Hazardous Materials B134 (2006) 87) but to investigate the foaming properties of a SiO ₂ -Al ₂ O ₃ -flux ratio change in the artificial lightweight aggregate recycling the sludge was the composition of the used raw material is difficult to predict properties of the aggregate produced to vary.

As a result, the present inventors have made extensive efforts to solve the problems of the prior art. As a result, the present inventors have found that, in a method of manufacturing an artificial lightweight aggregate, coating is performed using a coating material composed of silica, limestone, and dolomite as a material composed of a ceramic oxide raw material, It is confirmed that the fusion of the aggregates generated in the firing process can be prevented when the foamed aggregate is manufactured and the low melting point such as slag, dredged soil or acidic clay is collected to collect the foamed gas required for lightening the aggregate. It is possible to form the lightweight aggregate without the addition of any additive and flux, and the present invention has been accomplished.

It is a main object of the present invention to provide a method for manufacturing an artificial lightweight aggregate which can prevent fusion of aggregates occurring in a firing process during the manufacturing process of an artificial lightweight aggregate.

Another object of the present invention is to provide a method for manufacturing an artificial lightweight aggregate capable of improving the foaming property of an artificial lightweight aggregate and forming a lightweight aggregate without adding any additive or flux.

In order to achieve the above object, the present invention provides a method of manufacturing a ceramic body, comprising the steps of: (a) molding a ceramic oxide raw material containing silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) (b) the particle size of the molded body is classified on the basis of 10 mm, and a coating material containing silica (SiO ₂ ), limestone (CaCO ₃ ) and dolomite (CaCO ₃ .MgCO ₃ ) is added to the body, Coating a molded article having a size of less than 10 mm with a coating material having a particle size of 0.15 to 0.8 mm and coating a molded article having a size of 10 mm or more with a coating material having a size of 0.3 to 1.0 mm; And (c) firing the molded body coated with the coating material.

The method for producing an artificial lightweight aggregate according to the present invention can prevent fusion of aggregates occurring in a firing process during the manufacturing process of an artificial lightweight aggregate, and can produce a uniform artificial lightweight aggregate. In addition, the artificial lightweight aggregate having improved foam properties can be produced without the addition of any additives or fluxes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view schematically showing a method for producing an artificial lightweight aggregate of the present invention. FIG.
FIG. 2 is a photograph of the molded aggregate, classification, coating, and artificial lightweight aggregate produced according to one embodiment of the present invention.
3 is a photograph showing the microstructure of the artificial lightweight aggregate before and after the coating of the molded aggregate formed in the sowing machine according to Example 1 of the present invention.
FIG. 4 is a graph showing the specific gravity and the water absorption ratio of the artificial lightweight aggregate before and after the coating of the molded aggregate formed in the shoemaker according to Example 1 of the present invention.
FIG. 5 is a photograph of an artificial lightweight aggregate before and after coating of a molded aggregate formed in a gulley machine according to Example 1 of the present invention. FIG.
FIG. 6 is a photograph showing the microstructure observed after firing of an artificial lightweight aggregate of less than 10 mm in a molded aggregate formed in a saddle stitcher according to Example 1 of the present invention. FIG.
7 is a graph showing the specific gravity, the water absorption rate, and the unit volume mass after firing of the artificial lightweight aggregate of less than 10 mm formed in the gulley machine according to Example 1 of the present invention.
FIG. 8 is a photograph of a microstructure observed after firing of an artificial lightweight aggregate of 10 mm or more in a molded aggregate formed in a sailboiler according to Example 1 of the present invention. FIG.
9 is a graph showing the specific gravity, the water absorption rate, and the unit volume mass after firing of the artificial lightweight aggregate having a size of 10 mm or more formed in a shedder according to Example 1 of the present invention.
10 is a photograph showing the microstructure of the artificial lightweight aggregate of less than 10 mm of the formed aggregate formed in the granulator according to the second embodiment of the present invention after firing.
11 is a graph showing the specific gravity, the water absorption rate, and the unit volume mass after firing of the artificial lightweight aggregate of less than 10 mm formed in the granulator according to the second embodiment of the present invention.
12 is a photograph showing the microstructure of the artificial lightweight aggregate of 10 mm or more of the formed aggregate formed in the granulator according to the second embodiment of the present invention after firing.
13 is a graph showing the specific gravity, the water absorption rate and the unit volume mass after firing of the artificial lightweight aggregate of 10 mm or more formed in the granulator according to the second embodiment of the present invention.
14 is a photograph showing an artificial lightweight aggregate subjected to surface modification according to Example 3 of the present invention.
15 is a photograph showing an artificial lightweight aggregate according to a comparative example of the present invention.
16 is a graph showing a sintering schedule according to Example 3 of the present invention.
17 is a graph showing the physical properties ((a) specific gravity and (b) absorption ratio) of the low melting point coating material.
18 is an optical image photograph showing the microstructure ((a) surface and (b) section) of the low melting point coating material.
19 is a graph showing the volume ratio and the water absorption ratio of the low-artificial lightweight aggregate according to the presence or absence of the coating of the low melting point coating material.
20 is a graph showing the temperature and the water absorption ratio of the low-temperature artificial lightweight aggregate according to the coating of each raw material and the temperature calcined by the two-stage firing method.
21 is an optical image photograph of the artificial lightweight aggregate which is fired and baked.
22 is an optical image of an artificial lightweight aggregate which is fired at two stages.
23 is a flowchart schematically showing a method for producing an artificial lightweight aggregate of the present invention.

According to the present invention, in the method of manufacturing an artificial lightweight aggregate, when a coating material composed of silica, limestone, and dolomite is coated on a material made of a ceramic oxide raw material and an artificial lightweight aggregate is manufactured using a rotary kiln, It was confirmed that the fusion phenomenon can be prevented.

Accordingly, in one aspect, the present invention provides a method of manufacturing a ceramic body, comprising the steps of: (a) molding a ceramic oxide raw material containing silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) as a main component to form a molded body; (b) the particle size of the molded body is classified on the basis of 10 mm, and a coating material containing silica (SiO ₂ ), limestone (CaCO ₃ ) and dolomite (CaCO ₃ .MgCO ₃ ) is added to the body, Coating a molded article having a size of less than 10 mm with a coating material having a particle size of 0.15 to 0.8 mm and coating a molded article having a size of 10 mm or more with a coating material having a size of 0.3 to 1.0 mm; And (c) firing the molded article coated with the coating material.

As shown in FIG. 1, the present invention discloses an artificial lightweight aggregate in which a ceramic coating material is coated and sintered from a ceramic oxide raw material containing silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) as a main component, The artificial lightweight aggregate according to the present invention uses a material composed of a raw material of a ceramic oxide, and comprises the steps of: (a) preparing a spherical shaped body having a predetermined diameter to improve the molding ability of the ceramic oxide raw material; (b) (C) subjecting the shaped body to a sintering process with a predetermined amount of the ceramic coating material in a pelletizer, (d) putting the coated molded material into a preheated rotary kiln, and , And (e) discharging the baked material from the baking furnace.

In the present invention, due to the high sintering temperature at the time of producing the artificial lightweight aggregate, the amount of the liquid phase formed on the surface of the specimen is increased to such an extent that the aggregate is clogged to prevent the fusion phenomenon in the rotary kiln , Coating with a coating material having a particle size in a different range according to the particle size of the formed body, and firing at different firing temperatures.

In the present invention, the step (b) may further include the step of surface-modifying the surface of the molded body with a low-melting-point coating material.

Characterized in that the surface modification is carried out with a low melting point raw material in order to collect the foaming gas required for lightening the artificial lightweight aggregate recycling the bottoms and dredged soil which are circulating resources.

The artificial lightweight aggregate is lightened by foaming, and the foaming mechanism is the formation of the surface that can generate the foaming gas and collect the generated gas. The foaming gas is produced by the reducing atmosphere in which the organic material contained in the aggregate is plugged into the outer shell when the aggregate is fired. The reaction formula by the reducing atmosphere is as follows.

3Fe ₂ O ₃ -> 2FeO · Fe ₂ O ₃ + 1 / 2O ₂ ---------------------- (1)

3Fe ₂ O ₃ + C - > 2Fe ₃ O _{4 +} CO - (2)

Fe ₃ O ₄ + C -> 3 FeO + CO - (3)

FeO _(s) - & gt _; FeO _{(l )} - (4)

The reactions of the equations (1) to (3) are reported to react with oxygen generated by the reducing atmosphere and Fe ₂ O ₃ and C of the aggregates, resulting in lightweighting of the aggregate by the discharge of CO ₂ (KGLee, "Bloating mechanism for coal ash with iron oxide ", J. Korean Cryst. Growth Cryst. Technol. 24 (2014) 77).

The formation of a surface capable of collecting the generated foaming gas is defined as a viscous behavior which is a behavior occurring in a low melting point compound and a surface densification in which surface pores are reduced by densification. In the case of viscous behavior, it is possible to manufacture lightweight aggregate because it has the advantage of increasing the volume expansion rate by foaming. In order to form a glassy material capable of collecting the foaming gas together with the foaming gas, raw materials having a low melting point must be added to form a surface (SHKang, KGLee, "Bloating mechanism of artificial lightweight aggregate for recycling & , J. Korean Ceram. Soc., 47 (2010) 445).

The ceramic oxide raw material contains silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) as a main component and can be used for natural soil, inferiority, dredged soil, fly ash, reject ash, coal fly ash, coal ash, But it may be at least one selected from the group consisting of steelmaking slag, molten slag, incineration slag, waste catalyst slag, sewage sludge, sludge incineration ash, paper ash and red mud, but is not particularly limited as long as it is a raw material containing silica and alumina as main components. These ceramic oxide raw materials include not only silica and alumina but also iron oxide (FeO), ferric trioxide (Fe ₂ O ₃ ), dioxide (P ₂ O ₅ ), calcium oxide (CaO), sodium oxide (Na ₂ O) MnO) as a main component.

In the molding process, a molded product having a spherical shape of 4 to 15 mm can be manufactured by using an extruder or a pelletizer.

The coating material may be coated to 1 to 10% by weight, preferably 2 to 8% by weight, based on the shaped body. Coating more than 10% by weight does not satisfy the lightweight aggregate standard because the coating layer is peeled off or the weight of the aggregate increases.

The firing temperature of the molded article of less than 10 mm is 1120 to 1180 ° C, and the firing temperature of the molded article of 10 mm or more is 1160 to 1200 ° C.

The coated artificial lightweight aggregate can be reused by re-classification. For molded articles having a particle size of less than 10 mm, particles greater than 1 mm, particles between 0.15 and 1.0 mm, and particles less than 0.15 mm may be reused as aggregates and coatings, respectively, and reused as fly ash and dredged soil. In the case of a molded article having a particle size of 10 mm or more, particles larger than 1 mm, particles of 0.3 to 1.0 mm and particles smaller than 0.3 mm may be reused as aggregates and coating materials, respectively, and reused as fly ash and dredged soil.

Specifically, the production method of artificial lightweight aggregate of the present invention is silica (SiO ₂₎ and alumina (Al ₂ O ₃₎ in preparing the uniform foamed aggregate using a ceramic oxide material containing as a main component, silica (SiO ₂₎ , Limestone (CaCO ₃ ) and dolomite (CaCO ₃ .MgCO ₃ ), the particle size of the coating material and the firing temperature are varied according to the particle size of the formed body, thereby preventing fusion of aggregates occurring in the firing process .

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are for illustrating the present invention only and that the scope of the present invention is not construed as being limited by these embodiments.

[Example]

Example 1

The coal ash, fly ash, and dredged soil used in this example were generated from a 'Y' thermal power plant in Korea and their chemical composition (wt%) was analyzed by XRF (ZSX-100e, Rigaku, Japan) Respectively. A 10 ± 1 mm spherical shaped body was prepared by mixing coal ash, fly ash and dredged soil and using an extruder (VANHO, 450-1 Haksan, Ri Chilgok-Gun, Korea).

The formed aggregate was classified into 10.0 mm or less / 10.0 mm or more. Then, the coated aggregate was coated with 5wt% of the aggregate weight of the coating material mixed with silica (SiO ₂ ), limestone (CaCO ₃ ) and dolomite (CaCO ₃ .MgCO ₃ ). The molded body and the coating material were put together in a pelletizer and rotated at a speed of 40 rpm and a slope of 50 ° for about 5 minutes. The aggregate compacts having completed the coating were then dried at 105 DEG C for 24 hours and then fired. The aggregate sintering method used in this example was a direct firing method and a two-step firing method in which a compact was put into a preheated electric firing furnace in advance and held at that temperature for 10 minutes before being discharged. Also, in the case of the two-stage sintering method, the sintering schedule of FIG. 16 was performed in order to make it similar to the rotary kiln sintering condition. In the examples, firing was carried out in a rotary kiln in order to evaluate applicability to mass production conditions.

FIG. 2 shows a photograph of a molded aggregate manufactured according to an embodiment of the present invention, classification, coating, and observation of artificial lightweight aggregate after firing. FIG. 3 is a photograph of the microstructure of the artificial lightweight aggregate before and after the coating of the molded aggregate formed in the machine according to Example 1 of the present invention. FIG. 3 is a photograph showing the state of fusion of the artificial lightweight aggregate. Respectively.

According to Example 1 of the present invention, the outer / inner microstructure of the formed aggregate formed after the firing of the artificial lightweight aggregate of less than 10 mm was observed (Fig. 6), and the firing of the artificial lightweight aggregate of the molded aggregate The outer / inner microstructure was also observed (Fig. 8).

As shown in FIGS. 2 and 5, the formed aggregate did not undergo fusion between the aggregates even after the coating and firing process. As shown in FIGS. 10, 12, and 14, the artificial lightweight aggregate having a uniform structure .

Example 2

Example 1 was carried out in the same manner as in Example 1, except that a pelletizer (WOONG BI MACHINERY CO., LTD.) Was used instead of the shoe mill.

FIG. 2 shows a photograph of a molded aggregate manufactured according to an embodiment of the present invention, classification, coating, and observation of artificial lightweight aggregate after firing. The outer / inner microstructures of the formed artificial lightweight aggregate of less than 10 mm in size were observed after firing of the artificial lightweight aggregate of the molded artificial aggregate according to Example 2 of the present invention (Fig. 10) External / internal microstructures were also observed (Figure 12).

As shown in FIG. 2 and FIG. 5, the molded aggregate does not cause fusion between the aggregates even after the coating and firing process. As shown in FIGS. 5, 6, and 8, the artificial lightweight aggregate having a uniform structure .

Example 3

The raw materials used in this experiment were bottom ash and dredge soils, slag generated in a plasma melting apparatus, and Acid Clay (Donghae Chemical Co., Ltd., Korea). The coal fly ash was discharged from the domestic Y thermal power plant after burning bituminous coal, and the dredged coal was used for the construction of the power plant. Each raw material was pulverized to a size of 100 mu m or less. The chemical composition of the pulverized raw materials was analyzed by XRF (ZSR-100e, Rigaku, Japan), and the results are shown in Table 2.

Each raw material was pulverized to a size of 100 μm or less using a pin mill, and the artificial lightweight aggregate was formed into a spherical shape of about 10 mm through a mixing process according to the mixing ratio of each material. In order to investigate the surface melting behavior of various raw materials for surface modification, 100% composition of slag, slag, dredged soil and acid clay were prepared and their characteristics were examined. Based on these results, since the composition for producing artificial lightweight aggregate is high in refractoriness, there is no plasticity at low temperature and low temperature at low temperature, so dredged dregs of plasticity point paste are mixed at 70:30, Lightweight aggregate was formed and no additives were used. About 5 wt.% Of slag, dredged soil and acid clay were coated on the aggregate, and then dried at 105 ° C for 24 hours using a dryer. As the firing method, a direct firing method and a two - step firing method were selected to control the rate at which foam gas is generated and discharged to the outside of the aggregate, the surface densification and the surface vitrification speed. In the case of direct firing, the firing temperature was varied from 1000 ° C to 1200 ° C at intervals of 100 ° C. After each addition at each temperature, it was maintained at the maximum temperature for 10 minutes and discharged, thereby minimizing the discharge time of the foam gas. In the case of two-stage firing, it is a method to give a sufficient time for the foaming gas to be discharged to the outside of the aggregate. The firing is firstly performed at 900 ° C to induce the discharge of gas, and then the second firing is performed at 1150 ° C. . The schedule of the two-stage firing method is as follows: (a) 3 minutes at 900 ° C for 7 minutes + 1150 ° C for 3 minutes, (b) 4.5 minutes at 900 ° C for 10.5 minutes + 1150 ° C, Min, and the sintering schedule graph is shown in Fig. After firing, the specimens were measured by volume ratio and water absorption ratio according to KS L 3114 standard. For the microstructure analysis, the fracture profiles of the aggregates were measured by using Camscope (DSC-105, Sometech, Korea ).

Confirmation of surface melting behavior of raw materials

In order to confirm the surface behavior of each raw material, an artificial lightweight aggregate was prepared with 100% composition of each raw material by using amorphous slag, dredged soil, and acid clay, which can form vitreous at low temperature. Artificial lightweight aggregate was prepared by the same method to confirm the surface behavior. The sintering of artificial lightweight aggregate was carried out at 600 ℃ to 1200 ℃ for 10 minutes at 100 ℃ intervals.

FIG. 17 shows bulk specific gravity and water absorption according to temperature and raw materials. Samples made from 100% slag are sintered at 700 ° C, and at 900 ° C or higher, the surface becomes vitrified and open pores disappear, resulting in almost zero absorption. In the case of acidic clay, the specific gravity value decreases sharply in the range of 1000 ~ 1100 ℃. It decreases gradually from 700 ℃ to about 4% as compared with the water absorption value. And the increase of the absorption rate at 1100 ° C. is judged to occur as the surface is divided as shown in the optical image of FIG. 18. Also, the dredged soil tends to have a lower specific gravity from about 1000 ° C, and the lowering of the water absorption value between 1100 ° C and 1200 ° C can be regarded as evidence of glassy formation on the surface. The specific gravity of the specimens prepared at 100% in-situ tends to decrease at over 1100 ° C, but it is judged that the foaming is not performed due to the high refractoriness, and the tendency of the absorption rate to increase from 1200 ° C . In Fig. 18, the surface of the specimen was observed at 900 ° C, and the slag was observed to cover the surface. The acid clay gradually became glassy at 700 ° C, . In the case of dredged soil, it is confirmed that black core is formed from about 1000 ° C and vitreous is formed between 1100 and 1200 ° C.

Properties of Surface Modified Artificial Lightweight Aggregate (Direct Fire Calcination)

In Fig. 17, the surface behavior of the aggregate prepared at 100% of the bottom ash was checked and it was found that the surface became vitrified and foamed at 1200 deg. On the other hand, the slag, dredged soil and acidic clay were found to be able to form vitreous on the surface at a relatively low temperature compared to the inferior. Therefore, 30wt% of dysplasia, which is a plasticity point, was prepared and the slag, dredged soil, and acidic clay, which are raw materials that can form glass at low temperature, can be coated To prepare a specimen.

FIG. 19 is a graph showing the volume ratio and the water absorption ratio of the low-artificial lightweight aggregate according to the presence or absence of the coating material. The foamed behavior of the uncoated aggregate is similar to the foamed behavior of 100% in the case of FIG. 17, and since the surface is not densified to 1100 DEG C, no foam is formed, and the bulk specific gravity is 1.6 or more. And the volume specific gravity was reduced to 1.2.

On the other hand, the coated aggregate foamed from 1000 ℃ regardless of the type of coating, and the volume specific gravity was between 1.3 and 1.4, which satisfied the lightweight aggregate standard of KS F 2534. As shown in the cross-sectional photograph of FIG. 20, the black core and the large pores are observed when the uncoated aggregate has a temperature of 1200 ° C., whereas the coated aggregates have the pores from 1000 ° C. .

In FIG. 19 (b), the absorptivity of the aggregates coated with the uncoated aggregate showed a tendency opposite to that of the bulk specific gravity because the coating material was not coated tightly on the aggregate surface (FIG. 21) ) Was different from that of the other samples because the heat treatment was carried out for 10 min at the maximum temperature for the direct firing. Therefore, it is considered that the uncoated aggregate was more heat-treated than the aggregate which was coated on the surface.

In the artificial lightweight aggregate production line, firing is done at the rotary kiln. Therefore, the artificial lightweight aggregate is fired while moving inside the rotary kiln from low temperature to high temperature. Therefore, the fire behavior can be predicted by the fire firing method in the previous section, but the capture behavior of the foam gas is not explained. The purpose of this study is to clarify the foaming mechanism.

As shown in FIG. 19, since the surface of the specimen coated at 1000 ° C shows surface densification, the single-stage firing temperature was set at 900 ° C. and the uncoated aggregate was foamed at a temperature between 1100 ° C. and 1200 ° C., The temperature was set at 1150 ° C and the firing time was adjusted to 10 minutes (a), 15 minutes (b), and 20 minutes (c) (Fig. 16)

In FIG. 20, the temperature and the water absorption ratio of the low-temperature artificial lightweight aggregate according to the coating of each raw material were shown by the two-stage firing method. In the case of firing through the two-stage firing method, the specimens fired at 900 ° C for 7 minutes and 1150 ° C for 3 minutes showed a decrease in specific gravity of 0.3 to 0.4 compared with the specimens not coated, Coated specimens showed lower specific gravity than uncoated specimens. As a result of comparing the firing through the two-stage firing method with the direct firing, it can be seen that the trapping of the foaming gas influences the weight reduction of the foaming gas in the production of the artificial lightweight aggregate. This is because surface densification and vitrification are important for foaming . In the case of (a) and (b), (b) and (c), the sintering proceeds and the bulk specific gravity is increased. do.

FIG. 21 shows that the formation of many pores in the specimen can be confirmed by coating the raw material having a lower melting point than the specimen not coated with the optical image of the two-stage fired coating by coating each raw material.

As a result, it was confirmed that the specific gravity was lowered in the same manner as the direct firing method, and the trapping behavior of the foaming gas was confirmed by the two - stage firing method. Therefore, it is possible to predict the foaming behavior in rotary kiln, which is a condition of actual mass production.

Fig. 14 shows the molded aggregate produced according to Example 3 of the present invention. As shown in Fig. 14, after the coating and firing process of the molded aggregate, fusion between the aggregates did not occur.

Comparative Example

Example 1 was carried out in the same manner as in Example 1, except that the coating was not carried out.

FIG. 15 shows the molded aggregate produced according to the comparative example of the present invention. As shown in Fig. 15, the formed aggregate had fusion between the aggregates.

[Test Example]

* Specific gravity: measured according to KS L 3114.

* Absorption rate: Measured according to KS L 3114.

Unit volume mass: measured according to KS F 2505.

FIG. 4 is a graph showing the specific gravity and the water absorption ratio of the artificial lightweight aggregate before and after the coating of the molded aggregate formed in the shoemaker according to Example 1 of the present invention. In FIG. 4, (Fig. 7 and Fig. 9) after the firing of the artificial lightweight aggregate after firing, the specific gravity after firing of artificial lightweight aggregate of 10 mm or more molded in the pelletizer according to Example 2 of the present invention, (Fig. 11 and Fig. 13) in which the absorption rate and the unit volume mass are measured.

The artificial lightweight aggregate produced according to the embodiment of the present invention has a specific gravity of 1.6 or less, an absorption rate of 15% or less, and a unit mass of 80% or less, which is similar to that of the uncoated case, .

It was possible to foam at low temperature through the coating of low melting point raw material after adding 30wt% of ash dredged soil which does not foam with high fire resistance. As a result of the surface coating of slag, dredged soil and acidic clay, which is a raw material with low melting point, the specific gravity value of about 0.3 ~ 0.4 can be reduced at 1100 ℃, which is relatively low temperature range, compared with uncoated specimens. As a result of the direct fire firing method and the two-step firing method to control the generation and discharge rate of foam gas, the surface densification and the rate of vitrification, the weight reduction of the artificial lightweight aggregate has a significant effect on the amount of foaming gas, Respectively. As a result of the direct firing method and the two-stage firing method, the tendency of the same specific gravity to be lowered was confirmed, and the same result was obtained in the conditions of mass production which is used in actual field.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be.

Claims (8)

A method for producing an artificial lightweight aggregate comprising the steps of:
(a) preparing a shaped body by molding a ceramic oxide raw material containing silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) as main components;
(b) the particle size of the molded body is classified on the basis of 10 mm, and a coating material containing silica (SiO ₂ ), limestone (CaCO ₃ ) and dolomite (CaCO ₃ .MgCO ₃ ) is added to the body, Coating a molded article having a size of less than 10 mm with a coating material having a particle size of 0.15 to 0.8 mm and coating a molded article having a size of 10 mm or more with a coating material having a size of 0.3 to 1.0 mm; And
(c) firing the molded body coated with the coating material.
The method of claim 1, further comprising the step of surface-modifying the surface of the molded body with at least one kind of low melting point coating material selected from the group consisting of slag, dredged soil and acidic clay after the classification of step (b) Method of manufacturing lightweight aggregate.
delete The method of claim 1, wherein the ceramic oxide raw material is selected from the group consisting of natural soil, underfill, dredged soil, coal fly ash, reject ash, coal fly ash, coal ash, steel dust, steelmaking slag, molten slag, Sludge, ash, sludge ash, paper, and red mud.
The method of producing an artificial lightweight aggregate according to claim 1, wherein the molding is carried out using a kneader or a kneader.
The method of manufacturing an artificial lightweight aggregate according to claim 1, wherein the formed body has a spherical shape of 4 to 15 mm.
The method for producing an artificial lightweight aggregate according to claim 1, wherein the coating material is coated in an amount of 1 to 10% by weight with respect to the molded article.
The method for producing an artificial lightweight aggregate according to claim 1, wherein the firing temperature of the molded article of less than 10 mm is 1120 to 1180 ° C, and the firing temperature of the molded article of 10 mm or more is 1160 to 1200 ° C.

Images