KR20120101876A - Manufacturing method of lightweight aggregate - Google Patents

Abstract

PURPOSE: A manufacturing method of a lightweight aggregate is provided to manufacture light aggregate which has excellent physical properties to be used in concrete. CONSTITUTION: A manufacturing method of a lightweight aggregate comprises the following steps: pulverizing fly ash collected from the fluidized bed boiler; separating from the fly ash one or more of calcium based chemical compound and sulfur compound; manufacturing a composition for the light aggregate by using the separated fly ash; and molding and sintering the composition for the light aggregate. The separation step separates one or more of the following: CaO, CaSO3, CaSO4 and SO3. The separation step uses a magnetic flux selector, a centrifuge or a cyclone separation method. The composition for the light aggregate additionally includes clay. The separated fly ash and clay are included at a mixing ratio of 9.5:0.5 to 0.5: 9.5. [Reference numerals] (AA) Pulverizing step; (BB) Separation step of harmful material; (CC) Manufacturing step of compositions for lightweight aggregate; (DD) Molding and sintering step of compositions for lightweight aggregate; (EE) Lightweight aggregate

Description

Manufacturing Method of Lightweight Aggregate

The present invention relates to a method for producing lightweight aggregate using coal ash recovered from a fluidized bed boiler.

The demand for fluidized bed boilers is increasing rapidly as the awareness of environmental regulations increases and the demand for eco-friendly power plants increases. This fluidized bed boiler has the advantage of reducing pollutants, such as nitrogen oxides and sulfur oxides, because the temperature of the furnace is kept relatively low at 800 to 900 ℃ and circulating the fuel in the form of particles compared to the conventional pulverized coal boiler. . As another advantage, the fluidized bed boiler can be applied to a variety of fuel compared to the conventional boiler. For example, low coal, low lignite, oil shale, petroleum coke, municipal waste, industrial waste, and the like can be given. In addition, the fluidized bed boiler is low in the amount of pollutants to reduce the installation of environmental equipment, such as desulfurization and denitrification facilities, providing economic efficiency even in operating costs.

Although it does not have such desulfurization facilities, it provides more than 90% of desulfurization efficiency by adding limestone during combustion.However, calcium-based and sulfur-based compounds such as toxic substances generated during the desulfurization process remain in coal ash to effectively treat the coal ash waste. This is required. In general, coal ash wastes of thermal power plants are buried in the ocean and the like, and recently, a method of recycling to concrete aggregates, etc. has emerged. However, as mentioned above, coal ash recovered from a fluidized bed boiler has a large amount of sulfuric acid when applied to concrete. The presence of a cargo and the like react with C3A (3CaO-Al ₂ O ₃ ), which is a constituent mineral of cement, and this reaction can produce sintering hydrate, erythrite, resulting in sulfate erosion. In addition, CaO may increase the basicity (CaO / SiO ₂ ) to cause usability deterioration due to expansion after concrete placement or to cause cracks in concrete, resulting in durability problems.

An object of the present invention for solving the above problems, by using the coal ash recovered from the fluidized bed boiler to provide a lightweight aggregate of excellent properties that can be applied to concrete, lightweight to recycle the coal ash of the fluidized bed boiler at an economic cost It is to provide a method for producing aggregate.

According to an aspect of the present invention,

Grinding the coal ash recovered in the fluidized bed boiler,

Separating at least one of calcium and sulfur compounds from the coal ash,

Preparing a composition for lightweight aggregate using the separated coal ash, and

It relates to a method for producing a lightweight aggregate comprising the step of molding and baking the composition for the lightweight aggregate.

The separating step is CaO, CaSO ₃ , CaSO ₄ , and SO ₃ At least 1 sort (s) can be isolate | separated. In addition, the separating may be magnetic separation, centrifugation or cyclone separation.

The magnetic force selection method may be performed using a magnet of 500 to 50,000 gauss. In addition, the centrifugation may be carried out at 5 G to 2,000 G.

The light aggregate composition may further include clay. In addition, the clay may be included in a mixing ratio of the separated coal ash to clay 9.5: 0.5 to 0.5: 9.5 (w / w).

Another aspect of the present invention relates to a lightweight aggregate manufactured by the method for producing a lightweight aggregate.

Another aspect of the invention relates to a lightweight aggregate comprising coal ash recovered from a fluidized bed boiler.

Method for producing lightweight aggregate according to the present invention CaO, CaSO ₃ , CaSO ₄ , SO ₃ in the coal ash recovered from the fluidized bed boiler Separating harmful components that can degrade the properties or usability of concrete, such as can be effectively applied to concrete, and can provide a lightweight aggregate with excellent properties. In addition, since the coal ash recovered in the fluidized bed boiler can be used for lightweight aggregate, the reuse rate of the coal ash can be increased.

Figure 1 shows briefly the manufacturing method of the lightweight aggregate according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to FIG. 1.

The present invention provides a method for producing lightweight aggregate using coal ash recovered from a fluidized bed boiler. The manufacturing method of the lightweight aggregate can be effectively applied to concrete by removing harmful components that may cause durability problems, erosion, etc. of the concrete in the coal ash of the fluidized bed boiler, it can provide a lightweight aggregate with excellent mechanical properties.

 (1) removal of harmful substances

The removal of the harmful substance is to remove the harmful substances in the concrete from the coal ash powder after crushing the coal ash to provide purified coal ash. By using the purified coal ash to provide an appropriate basicity (CaO / SiO ₂ ) in the production of lightweight aggregates can lower the firing temperature and significantly lower the degree of cracking during foaming. In addition, it is possible to reduce the occurrence of erosion or cracking of the concrete according to the harmful substances.

The coal ash is recovered from a fluidized bed boiler. When the harmful substance is contained in a large amount of concrete (exceeding the limit of light aggregate composition prescribed by KS), it may cause erosion or cracking of concrete, which may cause durability problems. May cause The harmful substance may be at least one of the calcium-based and sulfur-based compounds, for example, CaO, CaSO ₃ , CaSO ₄ , and SO ₃ It may be one or more of the above, but is not limited thereto.

The removing of the harmful substances may include a crushing step of coal ash and a separation step of coal ash.

Crushing stage of coal ash

The crushing step of the coal ash is to crush the coal ash to fine powder to facilitate the separation of the harmful substances and the production of light aggregate.

The grinding method may use a grinding apparatus known in the art, and more specifically, impact crusher, jaw crusher, grinding, raymond mill, hammer mill, cone crusher, roller mill, rod mill, ball mill, wheel mill, atri It may be carried out in a wet and / or dry manner using a shunt mill or the like.

For example, in the crushing step, the coal ash recovered from the fluidized bed boiler is first pulverized with a roll or jaw crasher and then secondly pulverized with a Raymond mill. . The particle size can be appropriately adjusted according to the method of using the coal ash, preferably 100 ㎛ or more, 10 to 100 ㎛, less than 10 ㎛ can be easily separated from the harmful substances. Before entering the primary grinding process, washing and drying of coal ash may be included. The first and second grinding process may be performed for 0.5 to 2 hours, respectively.

Separation stage of coal ash

The coal ash separation step separates harmful substances from the crushed coal ash. The separation method may be a magnetic screening method, a cyclone separation method, centrifugal separation, and the like, and preferably, a magnetic screening method and a cyclone separation method may be used.

For example, the magnetic screening method may remove a harmful substance from the coal ash by using the magnetic difference of the particles, and may use a magnetic screening device including an electromagnet or a permanent magnet. The magnetic force of the electromagnet or permanent magnet is not particularly limited, but may be preferably 500 to 50,000 gauss, more preferably 2000 to 20,000 gauss. In addition, the magnetic separator may be suspended, drum, lattice, pulley, etc., but is not limited thereto.

The centrifugation separates the ash and the toxic substances according to the specific gravity using centrifugal force. The range of the centrifugal force is not particularly limited, but may be preferably 5 G to 2,000 G. In addition, the centrifugal separation may use a drum-type or cyclone-type centrifugation using frictional charging, but is not limited thereto.

(2) step of manufacturing lightweight aggregate

The manufacturing step of the light weight aggregate is to produce a light aggregate composition using the separated coal ash powder after the separation step, and then to produce a light weight aggregate through a molding and baking process.

The manufacturing step of the light weight aggregate may include a manufacturing step of the composition for light weight aggregates, a molding step of the light weight aggregate composition, and a firing step of the molded body. In addition, the manufacturing step of the lightweight aggregate may further comprise the step of ripening the composition after the manufacturing step of the composition for lightweight aggregate.

Steps for preparing a composition for lightweight aggregate

The manufacturing step of the composition for light weight aggregate is prepared by using a coal ash separated by a molding method alone or by mixing the coal ash and clay to produce a light aggregate composition having a suitable viscosity. The manufacturing step of the light aggregate composition may be carried out by wet mixing for 10 minutes to 2 hours using a mill or agitator.

The clay acts as a caking additive and increases workability to facilitate molding. In addition, it is possible to increase the strength after the sintering of the aggregate by increasing the base forming density.

The clay may be a mixture with pellet-based clay minerals (LECA, HAYDIT and KERAMSIT clay) prepared using dredged soil or other siliceous material. The dredged soil is separated from the gravel and stone using a sorter, and if necessary to remove impurities such as salt through a washing process. Next, after the first grinding using a roll crusher may be mixed with the refined coal ash powder through the second grinding using a high speed mill.

The clay may be used in a mixing ratio of the coal ash powder to clay 9.5: 0.5 to 0.5: 9.5 (w / w), preferably 9: 1 to 7: 3. When the clay is included within the range of the above-mentioned criteria, it is possible to form a uniform mixture, and to improve the mechanical strength of the aggregate after sintering.

In addition to the above components, it may further include other components depending on the use of the lightweight aggregate. For example, natural materials such as sand, gravel, and the like, EAF dust, sewage sludge incineration, stone powder, aluminum dross, red mud, and the like, but are not limited thereto.

Aging stage of the composition for lightweight aggregate

The aging step of the light aggregate composition may be selectively performed according to the molding method of light weight aggregate. For example, the composition is filter pressed to form a filter cake, and then the filter cake is aged at room temperature for 1 to 7 days, preferably for 3 to 7 days, to uniform the water distribution in the cake. The water content of the filter cake may be 20 to 25%.

Forming step of the composition for lightweight aggregate

The molding step molds the composition to the desired shape. The molding method may be selected according to the use, and the composition may be treated by an appropriate method to form a molded article. For example, during extrusion molding of lightweight aggregate, the composition may be directly injected into an extruder or a pelletizer, or molded into a desired shape using a vacuum refining machine. The composition can also be pelletized after grinding again and second mixing.

Molded  Firing stage

The firing step of the molded body is to produce a lightweight aggregate by firing the molded body. The firing step may use a sintering furnace known in the art, for example, a rotary kiln, a box furnace, a tube furnace, a microwave sintering furnace, or the like, but is not limited thereto.

In the firing step of the molded body may be injected into the sintering furnace and calcined for 0.1 to 20 hours at a temperature of about 950 to 1250 ℃ (1 to 100 ℃ / min). In addition, when using a rotary kiln, a molded object can be baked, moving at a speed of about 1-4 m / min. The molded body is introduced in about 5 to 20% based on the cross-sectional area of the sintering furnace. The sintered compact is slowly cooled to a temperature of about 400 to 500 ° C. while passing through a cooler, and then naturally cooled to room temperature.

Hereinafter, the present invention will be described in more detail with reference to the following Examples and Comparative Examples. The following examples are merely examples for illustrating the present invention, and do not limit the protection scope of the present invention.

Example  1: Manufacture of Lightweight Aggregate (Magnetic Sorting Method)

Alumina balls (volume 30%) and coal ash powder 500g were added to a 3liter alumina pot, followed by dry ball milling for 5 h at 120 rpm. Next, 500 g of water was added and pulverized with a wet mole to obtain coal ash of 50 μm or less. The pulverized coal ash slurry was magnetically separated using a magnetic separator (5,000G, model name: JSM-6390). Measures EDS (Energy Dispersive Spectros) to sort coal ash separated into small particles with low content of calcium and sulfur element, mixes the coal ash and clay (9: 1 w / w), Molded. The molded product was put in a box furnace and baked at 1150 ° C. for 20 minutes to produce a lightweight aggregate. The prepared light weight aggregate is shown in Table 1 by measuring the components (KS L 4007, 3128 reference analysis), specific gravity and absorption (KS F 2533 and KS F 2529).

Example  2: Production of lightweight aggregate (centrifugal separation)

Light aggregates were prepared and measured in the same manner as in Example 1 except that the pulverized coal slurry of 50 μm or less of Example 1 was placed in a 50 cc centrifugal vessel and centrifuged by applying a centrifugal force of 20,000 G for 30 seconds. The results are shown in Table 1.

Example  3: manufacture of lightweight aggregate ( Cyclone  Separation method)

Put alumina ball (30% of volume) and 500g of coal ash powder in 3liter alumina pot, dry ball mill for 5h at 120 rpm, dry grinding below 50um using small laboratory cyclone A light aggregate was prepared and measured in the same manner as in Example 1, except that was added. The results are shown in Table 1.

Comparative example  1: manufacture of lightweight aggregate

Light aggregate was prepared and measured in the same manner as in Example 1, but not through the separation step of the pulverized coal ash. The results are shown in Table 1.

Configuration Comparative Example 1 Example 1 Example 2 Example 3 CaO 32.59 9.8 15.4 16.4 SO ₃ 0.94 0.04 0.09 0.09 importance 1.32 1.53 1.46 1.46 Absorption rate (%) 19.8 22.8 20.9 20.7

Referring to Table 1, the lightweight aggregate according to the present invention is the content of CaO and SO _{3 that} is legal to the limit value (CS F 2583, CaO: 20.0% or less, SO ₃ : 0.5% or less) of concrete aggregate prescribed in KS As a result, it can be seen that by using the coal ash recovered from the fluidized bed boiler, it is possible to provide a lightweight aggregate applicable to concrete.

The method for producing lightweight aggregate according to the present invention can provide a lightweight aggregate having excellent properties applicable to concrete by using coal ash recovered from a fluidized bed boiler, and can improve the recycling degree of coal ash recovered from a fluidized bed boiler. .

Claims (12)

Grinding the coal ash recovered in the fluidized bed boiler,
Separating at least one of calcium and sulfur compounds from the coal ash,
Preparing a composition for lightweight aggregate using the separated coal ash, and
Method for producing a lightweight aggregate, characterized in that it comprises the step of molding and baking the composition for light weight aggregate.
The method of claim 1,
The separating step is CaO, CaSO ₃ , CaSO ₄ , and SO ₃ Method for producing a lightweight aggregate, characterized in that for separating at least one of the.
The method of claim 1,
The separating step is a method for producing lightweight aggregate, characterized in that using the magnetic separation method, centrifugal separation or cyclone separation method.
The method of claim 3,
The magnetic force selection method is a method for producing a lightweight aggregate, characterized in that carried out using a magnet of 500 to 50,000 gauss.
The method of claim 3,
The centrifugation is a method for producing lightweight aggregate, characterized in that carried out at 5 G to 2,000 G.
The method of claim 1,
The lightweight aggregate composition is a method for producing a lightweight aggregate, characterized in that it further comprises clay.
The method of claim 1,
The clay is a method of producing a lightweight aggregate, characterized in that contained in the mixing ratio of the separated coal ash to clay 9.5: 0.5 to 0.5: 9.5 (w / w).
The method of claim 1,
The manufacturing method of the light weight aggregate is a method of manufacturing a light weight aggregate, characterized in that further comprising the step of aging the composition for light weight aggregate after the step of preparing the composition for light weight aggregate.
The method of claim 8,
The aging step is a method for producing a lightweight aggregate, characterized in that for 1 to 7 days at room temperature after the filter pressing the composition for lightweight aggregate.
The method of claim 1,
The firing temperature in the firing step is a manufacturing method of light weight aggregate, characterized in that 950 to 1250 ℃.
Light aggregate, characterized in that produced by the method for producing a light aggregate of any one of claims 1 to 10.
Light weight aggregate, characterized in that containing coal ash recovered from the fluidized bed boiler.

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