JP3168709B2 - Separation and removal method of unburned carbon from fly ash - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for producing fly ash, which is recovered from coal fuel gas by an electric dust collector.
The present invention relates to a method for efficiently separating and removing unburned carbon from fly ash containing unburned carbon.

[0002]

2. Description of the Related Art In a coal-fired thermal power plant, fly ash recovered from exhaust gas by an electric dust collector contains a considerable amount of unburned carbon. This fly ash has been conventionally used in large quantities in the cement industry, civil engineering and construction industries as a cement admixture, a concrete aggregate and the like. However, fly ash is also obtained by combustion of crude oil other than coal, etc., and is generated by combustion of coal in places other than thermal power plants.

[0003] Conventionally, fly ash generated in a thermal power plant has a relatively small amount of unburned carbon, and even when used as a cement admixture, a concrete aggregate, or the like.
Although there was no particular problem, in recent years low-priced, low-grade coal has been used for the purpose of reducing power generation costs, and the amount of nitrogen oxides (NOx) generated by combustion has been reduced. For example, a large amount of unburned carbonaceous material tends to remain in the generated fly ash due to a tendency to lower the combustion temperature in order to reduce the temperature. Unburned carbonaceous material (usually called unburned carbon)
If fly ash containing a large amount of ash is used, for example, as a raw material for fly ash cement, any problem that causes blackening of the cement or a reduction in the strength of the hardened cement occurs. For this reason, various methods for separating and removing unburned carbon from fly ash have been conventionally developed.

[0004] Known methods for separating and removing unburned carbon from fly ash include (1) a method in which fly ash is reburned to burn and remove unburned carbon, and (2) a method in which unburned carbon is removed. Focusing on this point, since it is contained in relatively large fly ash particles,
A method of separating and removing unburned carbon using a sieve, that is, fly ash having a large amount of unburned carbon, (2 ') a method of classifying unburned carbon using an airflow classifier, (3) a method of separating unburned carbon Focusing on this point, there is a method in which unburned carbon-containing fly ash is made to be in a fluidized state by an air current to separate and remove unburned carbon, since the specific gravity of the fly ash is lower than that of fly ash.

[0005] Among the above conventional methods, the combustion method (1) requires a larger amount of fuel in order to obtain fly ash which is originally used on the premise that it is inexpensive. There is a problem that it cannot be said. on the other hand,
In the classification method using a sieve of (2), it is difficult to treat a large amount of unburned carbon-containing fly ash in a short time due to operational restrictions of using a sieve. The method (2 ') of classifying unburned carbon-containing fly ash with an airflow classifier has the advantage of treating large quantities in a short time, and is a method suitable for industrial use. The unburned carbon contained in such large fly ash particles is
There is a problem that fly ash on the fine particle side tends to enter during the treatment, and it is difficult to reduce the unburned carbon content in the recovered fly ash to a sufficient level.

[0006] As an improvement of (3) a method of treating unburned carbon-containing fly ash in a fluidized bed by an air current, fly ash is arranged in a layer in a container or on a plate and compressed from below the fly ash layer. There is also known a method in which air is blown to form a fluidized bed, and in this fluidized bed, unburned carbon having a low specific gravity (that is, having a low density) is floated to an upper portion of the bed to collect and remove the unburned carbon. However, in this method, it is important that the entire layer forms a uniform flow state in order to achieve the purpose, and if a uniform flow state is not formed, there is a problem that sufficient separation cannot be realized. is there. That is, when fine particles are mixed, for example, when fine particles having a size of 10 μm are mixed in fly ash, it is possible to form a uniform fluidized bed which is considered to be separated due to a difference in specific gravity of the particles. It is difficult to achieve an intended separation because it is difficult and an uneven flow state such as partial fluidization and blow-through of a compressed gas occurs. In addition, this method has a disadvantage that the amount of processing per hour is reduced because the residence time of fly ash in the layer required for separating unburned carbon is increased.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for efficiently removing unburned carbon from fly ash containing a large amount of unburned carbon, such as fly ash, which is recovered from coal fuel gas by an electric dust collector. It is an object of the present invention to provide a method for separating and removing with a relatively simple facility, with a small amount of energy consumption, and with a high separation efficiency without the necessity.

[0008]

Means for Solving the Problems The present invention resides on a surface.
It has one or two or more weirs that are inclined so as to have an angle of 45 degrees or less with respect to the left-right direction of the surface, and inclines only in the front-rear direction so that it has an inclination angle of 45 degrees or less.
While supplying fly ash in the form of a layer on the upper side of the plate placed at an angle , the plate has an amplitude of 0.05 to
The present invention relates to a method for separating unburned carbon from fly ash, wherein the unburned carbon is caused to float on the upper surface of the layer by applying a vibration of 10 mm and a frequency of 30 to 300 Hz, and then slide down along the weir.

Next, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic view of an example of the structure of an apparatus suitable for carrying out the method for separating and removing unburned carbon from fly ash according to the present invention, and FIG. 2 is a cross-sectional view taken along the line II of the apparatus of FIG. .

In the separation device shown in FIG.
Are arranged so as to have an inclination angle of 15 degrees (α in FIG. 2) only in the front-back direction from the horizontal. However, the angle of inclination of the plate 1 is not necessarily required to be 15 degrees, and an appropriate angle of inclination of 45 degrees or less is set in consideration of the amount of fly ash to be treated, the required level of removal of unburned carbon, and the like. Good. Usually, a tilt angle of 5 to 30 degrees is preferable, and it is particularly preferable to arrange them at a tilt angle of 10 to 20 degrees.

The plate 1 is provided so that fly ash supplied on the plate does not fall from the side.
A side plate 2 is provided. However, this side plate is not necessary if the plate has a sufficient width for the amount of fly ash to be supplied.

On the surface of the plate 1, efficient separation of fly ash and unburned carbon (more precisely, efficient separation of fly ash having a low unburned carbon content and fly ash having a large unburned carbon content) In order to realize (separation), a weir 3 is provided. The weir 3 is arranged so as to have an angle of 15 degrees (β in FIG. 1) with respect to the horizontal direction of the surface . However, the inclination angle of the weir is not necessarily 15 degrees, and an appropriate inclination angle of 45 degrees or less is set in consideration of the amount of fly ash to be treated, the required level of unburned carbon removal, and the like. Just fine. Usually, the inclination angle is preferably 5 to 30 degrees, and particularly preferably, the inclination angle is 10 to 20 degrees. When a plurality of weirs are provided, the inclination angles of the weirs do not necessarily have to be the same, and may have different inclination angles. In the illustrated plate, each of the weirs 3 is described as being formed independently and attached to the surface of the plate 1.
It may be formed integrally with the plate (that is, formed as a plate having irregularities). Also,
There is no particular limitation on the shape (such as the cross-sectional shape) of the weir. Also, regarding the number of weirs, the distance between weirs, the size of weirs, etc.
The amount may be appropriately determined in consideration of the amount of fly ash to be treated, the level of removal of necessary unburned carbon, and the like. However, the height of the weir is usually adjusted to be 25 mm or less.

In the apparatus shown in FIG. 1, an unburned carbon recovery groove 4 is formed on one side surface of the plate 1. The unburned carbon recovery groove 4 is for efficiently collecting and removing unburned carbon (fly ash having a high unburned carbon content) for separation and removal, which slides down along each of the weirs 3. .

A spring 5 and a vibration device 6 are provided below the plate 1. The vibration device 6 includes the plate 1
The amplitude is 0.05 to 10 mm (preferably 0.2 to 5 m
m), frequency 30 to 300 Hz (preferably 50 to 20 Hz)
0 Hz), which is a vibration imparting device having a function of applying a violent vibration such as a known device (for example, a device that generates vibration by moving a piston in a cylinder by compressed air or electromagnetic force, or decenters a weight (weight). Electric motor that generates vibration by rotating a shaft attached to it)
Can be used by appropriately selecting from the following.

In carrying out the method for separating and removing unburned carbon from fly ash according to the present invention, for example, FIGS.
First, an apparatus as shown in (1) is prepared, the apparatus is vibrated, and fly ash (fly ash containing a large amount of unburned carbon to be treated) 7 is supplied above the plate 1 in a layered manner. The fly ash layer 7 'is formed. Considering the separation efficiency of the target unburned carbon,
The fly ash layer 7 'on the plate has a thickness of 20
mm. That is, at the time of the separation operation, the fly ash layer on the plate has a thickness equal to or slightly smaller than the height of the weir, which is effective for efficient separation of unburned carbon. Is desirably determined in consideration of the height of the weir on the plate of the separation device to be used. And for that purpose, it is preferable to supply fly ash using a fixed-quantity supply device. In addition, the vibration of the apparatus may be stopped when the fly ash is supplied, and the vibration may be started after supplying a certain amount of the fly ash.

The fly ash layer 7 'supplied and formed on the plate 1 has a uniform mixture even when supplied.
Recovered fly ash that is relatively heavy due to the vibration of plate 1 (fly ash with low unburned carbon content)
7 "sinks to the lower side, whereas the particles 8 having a high content of unburned carbon rise to the top of the layer because they are relatively light, and violently jump off the surface of the layer. A surface layer that moves is formed, and the particles 8 containing a large amount of unburned carbon in the surface layer are light and in a violent motion state. It easily slides down (moves to the side) and slides into the unburned carbon recovery groove 4. On the other hand, most of the recovered fly ash 7 ″ sinking below (relatively heavy particles)
Gets over the weir 3 without sliding down along the weir 3. The recovered fly ash 7 ″ is pressed by unburned carbon that has not been separated in the previous area or by other particles that have been separated but have not yet reached the unburned carbon recovery groove 4. Along with the unburned carbon that has passed over the weir 3, a similar separation process is performed again before proceeding to the next weir 3. Such a separation and recovery operation is performed as many times as the number of weirs. The particles 8 having a high carbon content and the recovered fly ash 7 ″ can be realized in a short time and with high separation efficiency.

1 and 2 (weir height: 5 m)
m, the number of weirs: 5), and the unburned carbon content rate was 5.2.
Weight of fly ash at a rate of 300 g / min and an amplitude of 1.5 so that the thickness of the fly ash layer is 4 mm.
mm, the plate was vibrated at a frequency of 100 Hz, and the separation operation according to the present invention was performed. As a result, fly ash having an unburned carbon content of 2.9% by weight was approximately 2%.
It was recovered at a rate of 20 g / min.

[0018]

According to the method for separating and removing unburned carbon from fly ash according to the present invention, the amount of unburned carbon in fly ash can be efficiently reduced by using a simple vibration device. . In addition, the intense vibration of the plate used in the present invention causes unburned carbon (fly ash containing a relatively large amount of unburned carbon) to jump to the surface of the fly ash layer with a high selectivity in a short time. Since it comes out, a large amount of fly ash can be processed in a short time. Furthermore, by increasing the number of weirs to be installed and performing multi-stage separation operations, the unburned carbon content level can be arbitrarily reduced to a required level. On the other hand, the unburned carbon content in fly ash containing a large amount of separated unburned carbon is larger than the unburned carbon content in fly ash separated by the conventional method. It can be used again as fuel.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of the structure of an apparatus suitable for carrying out the method for separating and removing unburned carbon from fly ash according to the present invention.

FIG. 2 is a sectional view taken along the line II of the device of FIG. 1;

[Description of Signs] 1 plate 2 side plate 3 weir 4 unburned carbon recovery port 5 spring 6 vibrator 7 supply fly ash 7 'fly ash layer 7 "recovered fly ash 8 unburned carbon (unburned carbon content Many particles)

Claims (1)

(57) [Claims] 1. The method according to claim 1 , wherein the object is located on the surface and has a 45
It has one or more weirs that are inclined to have an angle of less than or equal to one degree, and fly above the plate that is installed only in the front-rear direction so as to have an inclination angle of 45 degrees or less. While supplying ash in layers, the plate has an amplitude of 0.05 to 10 mm and a frequency of 30 to 30.
A method for separating unburned carbon from fly ash, wherein unburned carbon is caused to float on the upper surface of the layer by applying a vibration of 0 Hz, and then slide down along the weir.