KR101903366B1 - Processing method of fly ash using air classfication and electrostatic separation - Google Patents

Abstract

Disclosed is a method for treating fly ash using distribution and electrostatic sorting, which reduces content of unburned carbon in fly ash by treating high unburned carbon content fly ash via distribution and electrostatic sorting step, so as to be applied as an admixture of cement and concrete. According to an embodiment of the present invention, the method for treating fly ash using the distribution and electrostatic sorting comprises the following steps: introducing high unburned carbon content fly ash; primarily distributing the high unburned carbon content fly ash into large particles of fly ash and granular fly ash; primarily sorting the primarily distributed large particles of fly ash electrostatically; secondarily distributing the primarily electrostatically sorted fly ash and the primarily distributed granular fly ash; and secondarily sorting the secondarily distributed fly ash electrostatically.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of treating fly ash using classification and electrostatic separation,

The present invention relates to a method of treating fly ash using classification and electrostatic separation, and more particularly, to a method for treating fly ash by classifying and electrostatically separating fly ash, And a method of treating fly ash using classification and electrostatic sorting that can be utilized as an admixture.

In recent years, various measures have been sought to realize low carbon green growth and low carbon society, escaping from the existing carbon-dependent economic paradigm, and it is expected that regulations on coal-fired power plants will be followed as one of various detailed measures. It is expected to change the burner and reduce the boiler combustion temperature to reduce SOx and NOx emissions. This change in coal-fired power generation method directly affects the quality of fly ash, and it is expected to discharge a large amount of fly ash (hereinafter referred to as "unburned carbon high-content fly ash"), which has a higher content of unburned carbon than conventional fly ash.

At present, about 65% of fly ash is used as cement and concrete admixture, but it can not be used as an admixture of cement concrete due to the decrease of strength in unburned carbon high fly ash. Therefore, the fly ash content of unburned carbon is largely reclaimed, and a method to utilize such unburned carbon high fly ash is desperately needed.

Even if the use of fly ash is newly developed, it is not easy to develop the use of fly ash as a new material because the particle size, color and residual carbon amount are different depending on the production of coal or the combustion conditions. In particular, reducing the content of unburned carbon to an allowable range is indispensable for use as a new material.

As for the reduction of the content of unburned carbon, methods such as screening classification, electrostatic classification, wet classification, dry classification, air classification, It has not been commercialized because the abatement treatment is not easy

In addition, various other chemical additives or methods for treating fly ash have been proposed (U.S. Patent No. 6,136,089), which oxidizes fly ash-carbon to ozone to lower the absorption capacity for surfactants. While this method has potential advantages, it has not been applied in the industry due to complexity and cost, or limited performance in process applications.

U.S. Patent No. 6,136,089 (October 24, 2000)

The object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a fly ash for reducing the content of unburned carbon in fly ash by treating unburned carbon high fly ash through classification and electrostatic separation steps, To provide a method of processing ash.

The task of the present application is not limited to the above-mentioned problems, and another task which is not mentioned can be clearly understood by a person skilled in the art from the following description.

According to one aspect of the present invention, a method of treating fly ash using classification and electrification comprises: introducing unburned carbon high content fly ash; First classifying the unburned carbon high content fly ash into fly ash of the assembly and fly ash of fine granules; A first electrostatic screening of fly ash of said first classified assembly; Classifying the fly ash of the first electrostatically sorted fly ash and the fly ash of the first classified fly ash; And a second electrostatic screening of the second classified fly ash.

The unburned carbon high-content fly ash may contain 6 wt% to 30 wt% of the porous unburned carbon.

The first electrostatic separation step may include first electrostatic separation of fly ash of the first classified assembly, crushing the first electrostatically sorted fly ash, and inputting the second electrostatic sorted fly ash to the second classification step have.

Further, the method may further include mixing the second electrostatically sorted fly ash with the secondarily classified fly ash.

In addition, the second classifying step may include finely dividing the charged fly ash when the second electrostatic sorted fly ash and the first sorted fine fly ash are introduced, Of fly ash and the remaining fly ash, and the upper 30% of fly ash having the second-order classified second-order granules can be input to the second electrostatic separation step.

Meanwhile, in the second classifying step, when the second fly ash separated by the second electrostatic separation and the fly ash of the first classified fine are fed, the loaded fly ash is pulverized as a differential unit, Of fly ash and the remaining fly ash, and the second 60 < th > fly ash having the second-order classified large-scale fly ash can be input to the second electrostatic separation step.

Further, before the step of sorting the first electrification and the step of sorting the second electrification, the step of removing the foreign substances of the first classified fly ash and the second classified fly ash and supplying them to the electrostatic separator can do.

The present invention can be used as a cement and concrete admixture by reducing the content of unburned carbon in fly ash by treating unburned carbon high fly ash through classification and electrostatic separation steps.

Accordingly, fly ash with reduced unburned carbon can be added to cement and concrete to obtain economical effects such as fluidity improvement and hydration heat reduction.

Further, the present invention can reduce the cost of processing by-products of thermal power plants and cogeneration plants by using unburned carbon-rich fly ash as a cement and concrete admixture, thereby improving environmental problems.

The effects of the present application are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a block diagram conceptually showing a fly ash processing apparatus according to an embodiment of the present invention.
2 is a flowchart illustrating a method of processing fly ash according to an embodiment of the present invention.
3 is a flowchart illustrating a method of processing fly ash in accordance with another embodiment of the present invention.
4 is a flowchart illustrating a method of processing fly ash according to another embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood, however, that the appended drawings illustrate the present invention in order to more easily explain the present invention, and the scope of the present invention is not limited thereto. You will know.

Also, the terms used in the present application are used only to describe certain embodiments and are not intended to limit the present invention. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram conceptually showing a fly ash processing apparatus according to an embodiment of the present invention; FIG. 2 is a flowchart for explaining a fly ash processing method according to an embodiment of the present invention; .

The unburned carbon high-content fly ash in the present invention is a by-product which is generated by burning coal in a coal fired combustor in a thermal power plant and has a specific gravity of 2.23 to 2.42 and a powder degree of 74 to 90% And it has a spherical shape and plays a role of improving the fluidity of cement when it is used as an admixture of cement or concrete. However, here, fly ash contains fly ash as much as 6% to 30%, and it targets fly ash that can not be used as cement concrete admixture material according to ASTM C618 standard.

In addition, it is a fly ash of cogeneration plant and circulating fluidized bed power plant. It has an irregular shape because the combustion temperature in the boiler is as low as 900 ℃ or less, and there is porous unburned carbon, and it is not suitable for use as cement and concrete admixture. And the like.

The chemical composition of such unburned carbon high-content fly ash is shown in [Table 1].

Chemical composition SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO LOI weight% 57.56% 20.47% 4.8% 0.88% 10.34%

In addition, there are many coal-fired power plants using fly ash in Vietnam power plant, Vietnam is difficult to ignite, and there is a lot of unburned carbon remaining after burning, and the loss of fly ash is 10% to 20%. Here, the loss on ignition (LOI) is the weight percentage of the raw material by the strong heat (950 ± 25 ° C) as a percentage of the weight of the raw material. It means that the content of unburnt briquettes in fly ash .

Referring to Figs. 1 and 2, a method of treating fly ash using a fly ash treatment apparatus will be described.

When the unburned carbon high content fly ash is introduced into the first classifier 20 from the reservoir 10 storing the unburned carbon high fly ash as the raw material at step S110, the first classifier 20 feeds the unburned carbon First, the high-content fly ash is classified (S120).

In the first classifying step S120, when the unburned carbon high-content fly ash is injected into the first classifier 20 in which the classifying air is circulated, air and fly ash The fly ash fed by the swirling flow and the centrifugal force meets the rapidly rotating minute fly ash and is separated into the fly ash of the assembly and the fly ash of the granule.

The fly ash of the assembly containing the unburned carbon which has not passed the fly ash is discharged to the bottom of the first classifier 20 and discharged to the outside. The fly ash of fine granules passing through the fly ash passes through the fly ash of the classifier 20 And can be discharged after collecting in the cyclone through the upper duct Duct.

The assembled fly ash discharged to the lower portion of the first classifier 20 can be input to the first electrostatic classifier 40. Here, the fly ash of the assembly means a level of 30% of the input capacity, and the particle size of the fly ash may be 70 탆 or more. At this time, the ignition loss of the fly ash can be more than 21%.

The fine fly ash collected in the cyclone of the first classifier 20 may be introduced into the second classifier 30 through the hopper 51. Here, the fine fly ash means a level of 70% of the input capacity, and the particle size of the fly ash can be less than 70 mu m. That is, the fine fly ash can be a small amount of the lower 70%.

When the first classified fly ash is input to the first electrostatic classifier 40, the first electrostatic classifier 40 performs the first electrostatic screening of the first classified fly ash (S130).

The first electrostatic separation step (S130) can remove unburned carbon around 10% contained in the fly ash through the electrostatic separator 40. The work function values of unburned carbon and minerals (SiO ₂ , Al ₂ O ₃ ) in fly ash are known to be 4.00 eV, 4.70 to 5.00 eV and 4.38 eV, respectively.

Accordingly, when the carbonaceous particles and the mineral particles contained in the fly ash come into contact with the copper plate, the electrostatic separator 40 charges the carbonizable particles, which are unburned carbon, positively and positively, ). In this way, the triboelectrified unburned carbon and the mineral particles pass through the electric field, while the (+) charged unburned carbon migrates to the negative plate, and the negatively charged mineral particles migrate toward the bipolar plate and electrify. That is, the unburned carbon of the electrostatically sorted fly ash is discarded.

The first electrostatic screened fly ash is finely ground through the crusher 50 and then stored in the hopper 51. Here, the pulverized fly ash amounts to about 20% of the charged amount, and the particle size of the fly ash may be about 45 탆

When the first electrostatic sorted fly ash stored in the hopper 51 and the fly ash of the first sorted fine granules are fed into the second classifier 30, the second classifier 30 is fed with the input fly ash The second classification is performed (S140).

In the second classifying step S140, the fly ash injected into the second classifier 30 is lowered by the cyclone effect through the air. And discharges fine granular fly ash from below the second classifier 30. The discharged fine fly ash can be introduced into the electrostatic separator (60) through the hopper (31). Here, the fine fly ash means an amount of 20% of the input capacity, and the particle size of the fly ash can be 45 탆 to 69 탆. At this time, the ignition loss of fly ash is about 10%.

And, above the second classifier (30), fine fly ash can be recovered through the airflow. Here, the fine fly ash means an amount of 80% of the input capacity, and the particle size of the fly ash can be 40 탆 or less. At this time, the ignition loss of fly ash is less than 7%.

When the second classified fine fly ash is input to the electrostatic separator 60, the electrostatic separator 60 performs the second electrostatic separation of the charged fly ash of the second sorted fine granules (S150).

The second electrostatic separation step (S150) can remove unburned carbon around 10% contained in the fly ash through the electrostatic separator (60). When the carbonaceous particles and the mineral particles contained in the fly ash come into contact with the copper plate, the electrostatic separator 60 charges the carbonizable particles, which are unburned carbon, positively and negatively, It is charged. In this way, the triboelectrified unburned carbon and the mineral particles pass through the electric field, while the (+) charged unburned carbon migrates to the negative plate, and the negatively charged mineral particles migrate toward the bipolar plate and electrify.

Here, the unburned carbon of the second electrostatically sorted fly ash can be discarded or recycled as a low calorific fuel. Here, the unburned carbon of fly ash means an amount of 10% to 20% of the charged capacity.

Then, the fly ash as the second electrostatic sorted mineral can be recovered as it is. Here, the fly ash means an amount of 80% to 90% of the input capacity, and the ignition loss of the fly ash is about 4% to 6%.

The fine fly ash recovered from the second classifier 30 is fed into the mixer 80 through the hopper 31 and the second electrostatic sorted fly ash recovered by the electrostatic separator 60 is fed to the hopper 61. [ , The mixer 80 mixes the fly ashes of the second classified fly ash with the second fly ash sorted (S160).

The step of mixing the fly ash (S160) can mix and discharge the particulate fly ash and the second electrostatically sorted fly ash through the mixer 80 in a proportional manner. The discharged fly ash can be recovered through the hopper 90 as it is.

Therefore, it is possible to control the ratio of the final amount to the initial amount of input, and to balance the ignition loss. As a result, high-quality fly ash with a heat loss of 6% or less can be obtained.

Accordingly, the fly ash recovered in the present invention can be used as cement, concrete admixture, and soft fire for improving soft ground by reducing unburned carbon. It is also expected to increase the recycling of industrial wastes and contribute to environmental protection.

Meanwhile, before the first and second electrostatic separation steps S130 and S150, the charged fly ash is removed and uniformly distributed in the fly ash through the air slide, and the electrostatic separator 40, 60 (S125, S145).

In the steps (S125 and S145) for removing and supplying the fly ash, foreign materials such as metal contained in the fly ash are once removed through gravity by passing through the air slide separated by the two ends, The main fly ash is uniformly distributed in a flat and well dispersed state, and is supplied to the electrostatic separators (40, 60) while falling through three feed feeds.

Accordingly, it is possible to supply foreign matters to the step of uniformly electrifying the fly ash, thereby improving the characteristics of the fly ash.

Meanwhile, a sieving test can be performed for each particle size (90 μm, 70 μm, 45 μm, and 20 μm) of fly ash in each step to set a classification threshold. In addition, the setting can be changed by analyzing the ignition loss by the particle size of the fly ash.

3 is a flowchart illustrating a method of processing fly ash in accordance with another embodiment of the present invention.

1 and 3, when unburned carbon high-content fly ash is introduced into the first classifier 20 from the reservoir 10 storing the unburned carbon high-content fly ash as a raw material, the first classifier 20) first classifies the unburned carbon high fly ash (S210).

In the first classifying step S210, when the unburned carbon high-content fly ash is pumped into the first classifier 20 together with air, a swirling flow occurs in the first classifier 20 through the air The fly ash flows toward the circumferential surface of the cylinder of the first classifier 20 under the action of centrifugal force and comes into contact with the inner surface and descends while drawing a spiral flow along the inner circumferential surface. At this time, the fly ash having a large particle size separated from the gas flow at the bottom of the first classifier 20 can be discharged as it is.

Above the first classifier (20), fly ash with a small particle size and light weight is discharged through the air stream. The discharged fly ash of the fine granules can be introduced into the second classifier 30 through the hopper 51. Here, the fly ash having a small particle size and a light fineness means an amount of 70% of the input capacity, and the particle size of the fly ash may be less than 70 mu m. That is, a small size and lightweight fly ash can be a small 70% of the grain size.

The assembled fly ash discharged to the lower portion of the first classifier 20 can be input to the first electrostatic classifier 40. Here, the fly ash of the assembly means a level of 30% of the input capacity, and the particle size of the fly ash may be 70 탆 or more. At this time, the ignition loss of the fly ash can be more than 21%.

When the fly ash of the first classified assembly is input to the electrostatic separator 40, the first electrostatic screen 40 separates the fly ashes of the first classified assembly into the first electrostatic separation (S220).

In the first electrostatic separation step S220, unburned carbon in the range of about 10% contained in the fly ash can be removed through the electrostatic separator 40. The first electrostatic screened fly ash is finely ground through the crusher 50 and then stored in the hopper 51. Here, the pulverized fly ash amounts to about 20% of the charged amount, and the particle size of the fly ash may be about 45 탆

When the first electrostatic sorted fly ash stored in the hopper 51 and the fly ash of the first sorted fine granules are fed into the second classifier 30, the second classifier 30 is fed with the input fly ash The second classification is performed (S230).

In the second classifying step S230, the fly ash injected into the second classifier 30 is lowered through the air by the cyclone effect. At this time, the fly ash can be pulverized into fine units by the pulverizing means. The pulverized fly ash discharges finely granulated fly ash below the second classifier 30. Here, the pulverization of the fine unit means pulverizing the particle size of the fly ash in a unit of 45 mu m.

The discharged fine fly ash can be input to the electrostatic separator 60 (S235: Y). Here, the fly ash having finer particle size means the amount of 30% of the input capacity, and the particle size of the fly ash can be 45 탆 to 69 탆. At this time, the ignition loss of fly ash is 10%. That is, the second pulverized flyash having finer particle size means the upper 30% fly ash having a larger particle size

Then, the remaining particulate fly ash can be recovered through the airflow above the second classifier 30 (S235: N). Here, the fine fly ash means an amount of 70% of the input capacity, and the particle size of the fly ash can be 40 탆 or less. At this time, the ignition loss of fly ash is less than 7%.

When the second classified fine fly ash is charged into the electrostatic separator 60, the electrostatic separator 60 performs a second electrostatic separation on the charged second sorted fine fly ash (S240).

The second electrostatic separation step S240 can remove unburned carbon of about 10% contained in the fly ash through the electrostatic separator 60. The unburned carbon 70 of the electrostatically sorted fly ash can be discarded or recycled. Here, the unburned carbon 70 of the fly ash means an amount of 10% of the input capacity.

Then, the fly ash as the second electrostatic sorted mineral can be recovered as it is. Here, the fly ash means an amount of 90% of the input capacity, wherein the ignition loss of the fly ash is less than 6%.

The remaining fine fly ash recovered in the second classifier 30 is fed into the mixer 80 through the hopper 31 and the fly ash recovered in the electrostatic separator 60 is fed through the hopper 61 to the mixer 80 , The mixer 80 mixes the charged second fly ash fine fly ash and the second fly ash sorted fly ash (S250).

The step of mixing the fly ash (S250) can mix and discharge the particulate fly ash and the second electrostatically sorted fly ash through the mixer (80). The discharged fly ash can be recovered through the hopper 90 as it is. Therefore, it is possible to control the ratio of the final amount to the initial amount of input, and to balance the ignition loss.

As a result, high-efficiency fly ash can be processed as compared with the input, and high-quality fly ash 100 having a heat loss of 6% or less can be obtained.

Meanwhile, the classification threshold can be set by performing a sieving test for each particle size (90 μm, 70 μm, 45 μm, and 20 μm) of the fly ash in each step in each step. In addition, the setting can be changed by analyzing the ignition loss by the particle size of the fly ash.

Accordingly, the fly ash treated according to the present invention can be utilized for soft ground improvement cement and concrete admixture with fly ash with reduced unburned carbon.

4 is a flowchart illustrating a method of processing fly ash according to another embodiment of the present invention.

1 and 4, when unburned carbon high-content fly ash is introduced into the first classifier 20 from the reservoir 10 storing the unburned carbon high-content fly ash as a raw material, the first classifier 20 first classifies the unburned carbon high fly ash (S310).

When the unburned carbon high-content fly ash is introduced into the first classifier 20 together with air, the first classifying step S310 causes the swirling flow to occur in the first classifier 20 through the air The fly ash flows toward the circumferential surface of the cylinder of the first classifier 20 under the action of centrifugal force and comes into contact with the inner surface and descends while drawing a spiral flow along the inner circumferential surface. At this time, the fly ash having a large particle size separated from the gas flow at the bottom of the first classifier 20 can be discharged as it is.

Above the first classifier (20), fly ash with a small particle size and light weight is discharged through the air stream. The discharged fly ash of the fine granules can be introduced into the second classifier 30 through the hopper 51. Here, the fly ash having a small particle size and a light fineness means an amount of 70% of the input capacity, and the particle size of the fly ash may be less than 70 mu m. That is, a small size and lightweight fly ash can be a small 70% of the grain size.

The assembled fly ash discharged to the lower portion of the first classifier 20 can be input to the first electrostatic classifier 40. Here, the fly ash of the assembly means a level of 30% of the input capacity, and the particle size of the fly ash may be 70 탆 or more. At this time, the ignition loss of the fly ash can be more than 21%.

When the fly ash of the first classified assembly is input to the electrostatic separator 40, the first electrostatic screen 40 separates the fly ashes of the first classified assembly into the first electrostatic separation (S320).

The first electrostatic separation step S320 may remove unburned carbon of about 10% contained in the fly ash through the electrostatic separator 40. The first electrostatic screened fly ash is finely ground through the crusher 50 and then stored in the hopper 51. Here, the pulverized fly ash amounts to about 20% of the charged amount, and the particle size of the fly ash may be about 45 탆

When the first electrostatic sorted fly ash stored in the hopper 51 and the fly ash of the first sorted fine granules are fed into the second classifier 30, the second classifier 30 is fed with the input fly ash The second classification is performed (S330).

In the second classifying step S330, the fly ash as the first classifier is lowered to the second classifier 30 through the air by the cyclone effect. At this time, the fly ash can be pulverized into ultrafine granules by the pulverizing means. The pulverized fly ash discharges finely granulated fly ash below the second classifier 30. Here, the pulverization of the ultrafine granular unit means pulverizing the particle size of the fly ash in a unit of 20 mu m.

The discharged fine fly ash can be input to the electrostatic separator 60 (S335: Y). Here, the fly ash having fine particle size means an amount of 60% of the input capacity, and the particle size of fly ash can be 20 to 69 탆. At this time, the ignition loss of fly ash is 9%. That is, the pulverized finely divided fly ash means the upper 60% fly ash having a large particle size

At the upper part of the second classifier 30, the remaining fine fly ash can be recovered through the airflow (S335: N). Here, the ultra fine fly ash means an amount of 40% of the input capacity, and the particle size of the fly ash can be 20 탆 or less. At this time, the ignition loss of fly ash is less than 3%.

When the second classified fine fly ash is charged into the electrostatic separator 60, the electrostatic separator 40 performs a second electrostatic separation on the charged second fine classified fly ash (S340).

The second electrostatic separation step (S340) can remove unburned carbon of about 10% contained in the fly ash through the electrostatic separator (60). It is possible to recover the fly ash as the second electrostatic sorted mineral as it is. Here, the fly ash means an amount of 90% of the input capacity, wherein the ignition loss of the fly ash is less than 6%.

The remaining fine fly ash recovered in the second classifier 30 is fed into the mixer 80 through the hopper 31 and the fly ash recovered in the electrostatic separator 60 is fed to the mixer 80 through the hopper 61, (80), the mixer (80) mixes the second classified fly ash fly ash and the second fly ash sorted fly ash (S350).

The step of mixing the fly ash (S350) can be carried out by mixing the fly ash with ultrafine fly ash and the second fly ash sorted through the mixer (80). The mixed discharged fly ash can be recovered through the hopper 90 as it is. Therefore, it is possible to control the ratio of the final amount to the initial amount of input, and to balance the ignition loss. As a result, high-efficiency fly ash can be processed as compared with the input, and high-quality fly ash 100 having a heat loss of 6% or less can be obtained.

On the other hand, a sieving test can be performed for each particle size (90 μm, 70 μm, 45 μm, and 20 μm) of the fly ash in each step to set the classification threshold. In addition, the setting can be changed by analyzing the ignition loss by the particle size of the fly ash.

Accordingly, the fly ash recovered in the present invention can be utilized for cement and concrete admixture. In addition, fly ash in which unburned carbon is reduced can be added to cement and concrete to obtain economical effects such as fluidity improvement and hydration heat reduction. In addition, by treating unburned carbon-rich fly ash as cement and concrete admixture, it is possible to reduce the cost of processing by-products of thermal power plants and cogeneration plants, thereby improving environmental problems. It is also expected to increase the recycling of industrial wastes and contribute to environmental protection.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or scope of the invention as defined in the appended claims. . Therefore, the above-described embodiments are to be considered as illustrative rather than restrictive, and the present invention is not limited to the above description, but may be modified within the scope of the appended claims and equivalents thereof.

10: Storage 20: Primary Classifier
30: Second classifier 50: Crusher
40, 60: electrostatic separator 80: mixer
31, 51, 61, 90: Hopper

Claims (7)

Introducing unburnt carbon high fly ash;
First classifying the unburned carbon high content fly ash into fly ash of the assembly and fly ash of fine granules;
A first electrostatic screening of fly ash of said first classified assembly;
Classifying the fly ash of the first electrostatically sorted fly ash and the fly ash of the first classified fly ash; And
And a second electrostatic separation of the second classified fly ash,
Wherein the second classifying step comprises:
When the second electrostatic sorted fly ash and the first sorted fine fly ash are charged, the charged fly ash is pulverized into fine units, and the uppermost 30% fly ash having the larger particle size and the second fly ash Classification,
Wherein the fly ash of the upper 30% with the second-order classified major is charged into the second electrostatic separation step. The method according to claim 1,
Characterized in that the unburned carbon high-content fly ash contains 6 wt% to 30 wt% of the porous unburned carbon. The method according to claim 1,
Wherein the first electrostatic separation step comprises:
The first fly ash of the first classified assembly is first electrostatically sorted,
Wherein the fly ash separated by the first electrostatic separation is pulverized and charged into the second classification step. The method according to claim 1,
Further comprising mixing the second electrostatically sorted fly ash with the secondarily classified fly ash. ≪ Desc / Clms Page number 20 > delete The method according to claim 1,
Wherein the second classifying step comprises:
When the second electrostatic sorted fly ash and the first classified fine fly ash are charged, the charged fly ash is pulverized as a differential unit, and the upper 60% fly ash having the largest particle size and the second fly ash Classification,
Wherein the fly ash having the second largest particle size and having the largest particle size of 60% is charged into the second electrostatic separation step. The method according to claim 1,
Before the first electrostatic separation step and the second electrostatic separation step,
And removing the foreign matter of the first classified fly ash and the second classified fly ash and supplying the removed foreign matters to the electrostatic separator.

Images