JPH0784337B2 - Fly Ash treatment method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for treating fly ash produced in large amounts in a coal-fired thermal power plant, etc., and particularly uses the fly ash as a cement material, a building material, an aggregate, or the like. It is about the method of processing to the ready state.

[Conventional technology and its problems]

At present, fly ash produced in coal-fired thermal power plants and the like is used as a cement admixture. However, if mixed in a large amount, the quality standard of the cement will not be satisfied, and therefore its application and use amount are limited.

That is, the fly ash usually contains a few percent to a dozen percent (wt%, hereinafter the same) of unburned components. On the other hand, according to the JIS standard for cement, the allowable content of unburned content (described as ignition loss in JIS) is 0.6% or less in the case of ordinary boltland cement.

Therefore, for example, fly fly with 6% unburned
Due to the regulation of unburned substances according to this JIS standard, only 10% or less can be used as a cement material.

Moreover, since limestone, which is the main raw material for cement, is produced in large quantities in Japan and at a relatively low cost, it is not necessary to use fly ashes which does not bring about quality improvement such as strength improvement.

For these reasons, there is currently a limit to the use of fly ashes for cement, and it is desired to develop applications for fly ashes that are produced in large quantities.

By the way, if the unburned content of fly ashes is 1% or less, 50
%, The unburnt content regulation by the JIS standard does not pose a problem, and in the case of ultrafine fly ashes of several μm or less, the cement strength is greatly improved due to the close packing effect of the ultrafine particles. Will occur.

[Object of the Invention]

Therefore, the present invention provides a method of treating ultrafine grain fly ashes with an unburned content of 1% or less generated in a coal-fired thermal power plant, etc., and treating them as a cement material, a building material, an aggregate, etc. in a large amount and at a low cost. The purpose is to propose.

[Means for Solving the Problem and Its Action]

The present invention has the above-mentioned object of crushing fly ashes until the unburnt content becomes 1% by weight or less at a melting point or lower and at an ashing temperature of the unburned content or higher, and then pulverized or pulverized. After that, the fly ash is ashed at a temperature not higher than the melting point and not lower than the ashing temperature of the unburned component until the unburned component becomes 1% by weight or less, which is achieved by a method for treating fly ash.

In the present invention, for example, fly ash generated in a coal-fired thermal power plant or the like is ashed at a temperature not higher than the melting point of the fly ash and higher than the ashing temperature of unburned components in the fly ash.

Here, the ashing temperature means the temperature at which the weight of the fly ash suddenly begins to decrease when left for a certain period of time at a certain atmospheric temperature, that is, the unburned content in the fly ash burns, as shown in the test results of FIG. Refers to the starting temperature. In the example of FIG. 5, about 450 ° C. is the ashing temperature.

For example, as shown in the examples, ashing is performed at a relatively low temperature of about 300 to 600 ° C.

Such a temperature can be easily obtained at low cost by utilizing waste heat of a boiler (for example, a boiler of a coal-fired thermal power plant).

By the above ashing, the fly ashes having an unburned content of 1% or less are ultra-finely pulverized to obtain ultra-fine fly ashes having a particle size of several μm or less. Alternatively, after ultra-fine pulverization to make ultra-fine fly ash having a particle size of several μm or less, the above ashing is performed to reduce the unburned content to 1% or less.

Limestone, which is the main raw material for cement, often has an average particle size of several tens of μm, and ultrafine fly ash having a particle size of several μm or less can fill the voids of limestone to form the closest packing.

Further, in the present invention, pre-pulverization can be performed prior to the above-mentioned ashing or ultrafine pulverization.

Further, in the present invention, the above ashing can be performed in an oxygen-rich atmosphere.

Any of these pre-milling and ashing with oxygen-enriched air has the effect of shortening the ashing time. This is because the pre-milling increases the specific surface area of the fly ash, and the oxygen-enriched atmosphere increases the ashing rate.

〔Example〕

FIG. 1 is a diagram showing the flow of one embodiment of the method of the present invention.

In FIG. 1, fly ash produced from an electrostatic precipitator (not shown) of a coal-fired thermal power plant is recovered by a hopper 1 and sent to a tube mill 2 which is a pre-crusher from a line 9 and has an average particle size of 5 to 5. Primary pulverization to about 10 μm is carried to the ashing device 3 through the line 10.

On the other hand, the air for ashing is sent from a line 15 to an adsorption-type oxygen production device (for example, a pressure swing adsorption / separation device) 7 filled with a synthetic zeolite for separating oxygen and nitrogen,
Only oxygen is recovered from the line 16, mixed with the air supplied from the line 20 to become oxygen-enriched air, and sent to the air heater 8 from the line 21. In the air heater 8, the oxygen-enriched air is sent from the line 17, heated to 300 to 600 ° C. by using the high temperature boiler waste gas sent from the line 19 as a heat source, and sent to the ashing device 3 from the line 18.

In this ashing device 3, the unburned components in the fly ash are burned by the oxygen-enriched air at 300 to 600 ° C.
It is reduced to the following and sent to the ultrafine grain mill 4 from the line 11.

In the case of fly ash, which is easily ashed, the tube mill 2 as the pre-crusher and the oxygen production device 7 may be unnecessary.

The ultra-fine grain mill 4 is a stirring mill (for example, a simple horizontal type Aniura type mill (Japanese Patent Application No. 61-47484), a two-axis independent rotating mechanism mill (Japanese Patent Application No. 61-38811), a jacket type outer cylinder and fins. A mill with an inner cylinder of a cooling system (Japanese Patent Application No. 61-38)
No. 812)] and the like are preferably used.

The above fly ash which has been pulverized by the ultrafine grain mill 4 is sent to the classifier 5 through the line 12 and has an average grain size of 2 to 5.
Classified into ultrafine particles of 3 μm or less and coarse particles other than that, the latter is returned to the ultrafine particle mill 4 from the line 14 and pulverized again, the former is from the line 13 as an ultrafine particle fly ashes product with unburned content of 1% or less. It is collected in the product tank 6.

Among the products thus obtained, 30% of normal cement was mixed with 0% of unburned matter and ultrafine fly ash having an average particle size of 1.3 μm, and a strength test of concrete was carried out.

As a result, it was confirmed that the compressive strength was about twice as high as that of the concrete without mixing the ultrafine fly ash.

In addition, due to the pore water removal effect of ultrafine particles, the amount of mixed water during concrete preparation could be reduced by more than 10%, the excess water was reduced, and concrete cracking did not occur.

Further, as schematically shown in FIG. 2, the ultrafine atomized fly ash super-particles 23 are the cement particles 22 shown in FIG.
It has been found that it is filled in the gap 24 of the above and exerts a pairing effect to improve the fluidity of the cement.

Further, as shown in FIG. 4, the ashing rate of unburned matter in the ash is
When ashing was performed with normal air without using the oxygen maker 7 without crushing with the pre-crusher 2 (average particle size 23 μm) (crushed with the pre-crusher 2 rather than AF in FIG. 4). (Average particle diameter 5 μm or less) When ashing is performed with normal air without using the oxygen production device 7 (B in FIG. 4), further crushing is performed by the pre-crusher 2 (average particle diameter 5 μm or less). It was also confirmed that ashing with oxygen-enriched air (oxygen concentration of 50% by volume) using the oxygen production device 7 (C in FIG. 4) becomes faster.

〔The invention's effect〕

According to the method of the present invention described above, the following effects can be obtained.

(1) Since the ashing is performed at a temperature lower than the melting point of the fly ash, there is no melting of the fly ash, and the inner wall of the ashing device,
There is no welding of fly ash on transportation equipment, piping, etc., and handling is easy.

Incidentally, depending on the fly ash, it may be welded to the ultra pulverizer during ultra pulverization, and in the case of such a fly ash, if ultra fine pulverization is performed after the above ashing, the The fly ash is not welded and super fine pulverization is easy.

(2) Since ultrafine fly ash removes pore water in cement and other granular and powdery materials, the amount of water used when making concrete or when kneading with granular and powdery materials, etc. can be greatly reduced. In addition, extra water does not ooze out after curing, and it has the effect of preventing cracks, and the number of contact points between particles is extremely large due to ultrafine particles, increasing the strength of concrete and other product materials.

(3) If the fly ash is pre-milled or ashed in an oxygen-rich atmosphere, the pre-milling increases the specific surface area of the fly ash, increasing the ashing speed in the oxygen-rich atmosphere, thus greatly shortening the ashing time. Is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a basic flow of an embodiment of the method of the present invention,
Fig. 2 shows the closest packing condition of cement particles and ultrafine fly ashes, Fig. 3 shows the filling condition of cement particles when there is no ultrafine fly ashes, and Fig. 4 shows the test results of ashing characteristics. FIG. 5 and FIG. 5 are views showing test results regarding the ashing temperature.

Claims (4)

[Claims] 1. After ashing fly ash until the unburnt content is 1% by weight or less at a melting point or less and an unburnt content ashing temperature or higher, and then ultra-fine pulverization or ultra-fine pulverization, A method for treating fly ash, characterized in that fly ash is ashed at a temperature not higher than the melting point and not lower than the ashing temperature of the unburned component until the unburned component becomes 1 wt% or less. 2. A method for treating fly ash according to claim 1, wherein boiler exhaust gas is used as a heat source for the hot air for ashing. 3. The fly ash is pre-ground before ashing or ultra-fine grinding.
The method for treating fly ash described in. 4. The method for treating fly ash according to claim 1, wherein ashing is performed in an oxygen-rich atmosphere.