JP5326168B2 - A method for treating coal ash used in concrete materials. - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for slurried coal ash pretreatment where unburned carbon is separated from slurried coal ash to be fed to flotation for removing the unburned carbon of coal ash so that the frequency of floatation can be reduced. <P>SOLUTION: A scavenger, a bubbling agent, and air are fed into the slurried coal ash composed of the unburned carbon-containing coal ash and water so as to produce bubbles, and the unburned carbon is caught in the bubbles. Before the slurried coal ash 6 is fed to a floatation apparatus 2 for separating tail ash having a low unburned carbon content, ultrasonic waves are emitted thereto by an ultrasonic wave generating apparatus 8 so that the separation efficiency of the unburned carbon from the coal ash is increased. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention is an efficiency for separating coal ash from unburned carbon of slurry coal ash supplied to a flotation for removing unburned carbon contained in coal ash generated in a coal-fired thermal power plant. It is related with the processing method of the slurry coal ash for improving.

  In coal-fired thermal power plants that burn coal, a large amount of coal ash is generated. Regarding this coal ash, JIS A 6201 (fly ash for concrete) is defined as fly ash 1 type: 3% or less, 2 type: 5% or less with respect to loss on ignition, and coal with low unburned carbon content. Ash has been partially used as a concrete material, but low quality coal ash higher than the unburned carbon content stipulated by JIS, which cannot be used as a concrete material, has been disposed of as industrial waste. As is well known, coal ash having an acidic pH value has an adverse effect on concrete materials.

  Unburned carbon impedes air entrainment on concrete and degrades the quality of concrete, and various methods such as electrostatic classification, combustion, and floating selection methods are used to remove unburned carbon from coal ash. Has been proposed.

  The present inventors have proposed a flotation system that separates unburned carbon from low-quality coal ash so that it can be used as coal ash for concrete (see Patent Document 1). In the flotation process described in Patent Document 1, the coal ash and the water containing the surfactant, which are conveyed in powder form from the coal-fired power plant to the ready-mix factory, are injected into a cylindrical slurry mixer to cause foaming. Rotate a stirring plate containing a magnet while pumping air into a cylindrical slurry mixer with the magnet turned on, and neutralize highly alkaline coal ash with a pH of 11-12 with carbon dioxide in the air to around pH 7 The unburnt carbon is entrained in the foamed ash, and the iron is separated as iron oxide. After confirming neutralization, the foamed ash is discharged, and then the stabilization process with a low content of unburned carbon is performed. After discharging the slurry-like residual ash to the concrete mixer, the magnet of the stirring plate is turned off to discharge iron. By this method, coal ash having about 5% unburned carbon could be separated from coal ash containing about 10% unburned carbon.

JP-A-11-171615

  Although the content of unburned carbon in coal ash used as a concrete material is within 5% by mass, in the flotation method described in Patent Document 1, coal ash derived from overseas coal or blended coal is used. Among them, since unburned carbon could not be removed up to about 5% by one flotation, it was necessary to flot the tail ash after flotation more than once. Further, in the dry powder state, the pH is checked by sampling, but it is a partial check, and it is difficult to manage the total amount of coal ash showing an acidic pH value, and the total amount of pH cannot be guaranteed.

Therefore, the present invention can more effectively separate unburned carbon from slurried coal ash supplied to flotation to remove unburned carbon from coal ash, reduce the number of flotation, Therefore, the present invention provides a method for treating slurried coal ash in which the pH of the total amount can be easily measured and acidic coal ash can be easily selected.

The slurry pulverized coal ash pretreatment method of the present invention is to produce a bubble by supplying a trapping agent, a foaming agent and air to a slurry pulverized coal ash composed of coal ash containing unburned carbon and water. Enhancing the efficiency of separating unburned carbon from coal ash by stirring the slurried coal ash before flotation to collect unburned carbon and separating tail ash with low unburned carbon content and slurry As a result, it is possible to control the total amount of pH of coal ash to be put into concrete.

  In the present invention, the unburned carbon content of the coal ash before the treatment is not particularly limited, and it may be derived from a low content of about 2% by mass or a high content of foreign coal exceeding 16% by mass. Unburnt carbon can be separated by pretreatment.

  If the amount of the coal ash in the slurry composed of coal ash and water is small, the amount of coal ash treated decreases, and if it is large, the viscosity increases and it becomes difficult to treat.

撹拌uses mixers to increase the efficiency of separating the coal ash and unburned carbon in the slurry by 10,500 rotating mixer blades (the mixer cutter) per minute.

  Unburnt carbon can be collected by using a kerosene or other known trapping agent known for conventional flotation, and bubbling agent by using pine oil or the like known for conventional flotation. .

  The tail ash can be returned to the flotation process multiple times, and unburned carbon can be further separated by flotation to reduce the carbon content.

The present invention is a slurry which shows an acidic pH value by separating unburned carbon from coal ash which is slurried by stirring slurry ash composed of coal ash containing water and unburned carbon and water. The pretreated coal ash is subjected to pretreatment, and the pretreated slurry ash is added with unburned carbon scavenger and bubbling agent, air is blown to generate bubbles, and unburned carbon is produced by floatation. Floss ash with a high content is taken out, and the water from which unburned carbon and water are separated is returned to the pretreatment as recovered water, and iron is separated from the slurryed coal ash as iron oxide by a magnet and subjected to the above flotation. Air is blown into the tail ash from which unburned carbon has been removed to neutralize and stabilize, the stabilized tail ash is made into a concentrated slurry, and the resulting concentrated slurry is used as a concrete material. Characterized by a.

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After the slurryed coal ash in the cylindrical portion is stirred to separate unburned carbon, the slurry discharge port is opened and the slurryed coal ash is supplied to the flotation apparatus. The tail ash is also sent to the stabilizer.

  In the coal ash treatment method of the present invention, the coal slurry pretreated by the slurry coal ash pretreatment method described above is floated and neutralized by blowing air into tail ash from which unburned carbon has been removed. The stabilized tail ash is dehydrated to obtain a concentrated slurry.

Moreover, coal ash treatment apparatus, the flotation device for removing by flotation slurried coal ash unburned carbon downstream of slurried coal ash pretreatment device, the tail ash from the flotation unit air And a dehydrating device for dehydrating the slurry from the stabilizing treatment device in this order.

The pretreatment method of the present invention is to stir the slurry coal ash supplied to the flotation, improve the separation efficiency of the unburned carbon in the flotation, and reduce the ignition loss value of the unburned carbon. it can. Moreover, the measurement of pH is facilitated by slurrying, acidic coal ash can be selected, and high-grade coal ash that can be used for concrete materials can be easily obtained. Concrete containing an appropriate amount of coal ash has increased long-term strength, can suppress salt penetration, has a large effect of suppressing alkali-aggregate reaction, and uses low-grade aggregate (recycled aggregate). Also shows the characteristic that strength reduction can be suppressed.

  In addition, since the pretreatment method of the present invention can reduce coal ash having a high unburned carbon content to a content suitable for concrete materials specified in JIS, conventionally, as non-standard industrial waste The coal ash that has been disposed of in landfill can be used effectively without being dumped.

  In addition, since the flotation equipment equipped with the slurry ash pretreatment device of the present invention can be easily installed in a ready-mixed concrete manufacturing plant because the equipment can be made simple and small, coal ash that was the target of industrial waste Can be used as a concrete material at low cost.

  The concentrated slurry obtained by the coal ash treatment method and the coal ash treatment equipment provided with the pretreatment method and the pretreatment apparatus of the present invention can be used as a concrete material as it is.

1 is an overall view showing an example of a coal ash treatment facility equipped with a coal ash slurrying apparatus of the present invention. 1 is a slurry coal ash pretreatment apparatus according to the present invention. It is sectional drawing which shows the example which has arrange | positioned the ultrasonic generator inside the slurry container. It is sectional drawing which shows the example arrange | positioned to the coal ash discharge pipe which made the ultrasonic generator slurry.

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  In the coal ash treatment facility shown in FIG. 1, a slurry coal ash pretreatment apparatus 1, a flotation apparatus 2, a stabilization treatment apparatus 12, and a dehydration treatment apparatus 14 are sequentially arranged.

  In FIG. 2, the slurrying container of the slurryed coal ash pretreatment device 1 has a cylindrical portion 4 formed below the hopper 3. Coal ash and water are supplied from the inlet 5 at the top of the hopper 3 to form a slurry of coal ash 6. At the lower part of the cylindrical portion 3, an openable / closable slurry discharge port 7 for discharging the slurryed coal ash 6 is provided. At this time, the pH is measured, and if it shows an acidic pH value, it is selected.

  In FIG. 2, an ultrasonic generator including an ultrasonic vibration element 8 is provided on the outer periphery of the cylindrical portion 4. In the ultrasonic generator, an ultrasonic vibration element 8 is attached around the cylindrical portion 3 at an interval, and the ultrasonic vibration element 8 is connected to an ultrasonic oscillator 9.

  As shown in FIG. 3, the ultrasonic generator 8 may be provided in the slurry container, for example, inside the cylindrical portion 3. Moreover, as shown in FIG. 4, you may provide in the coal slurry discharge pipe 7a.

  A flotation apparatus 2 is disposed downstream of the slurryed coal ash pretreatment apparatus 1. The flotation device 2 adds an unburned carbon scavenger and a foaming agent to the slurryed coal ash 6 from the slurryed coal ash pretreatment device 1 and blows air from the air blowing port 10 to generate bubbles. Coal ash containing a large amount of unburned carbon and unburned carbon in air bubbles is collected, floss ash having a high unburned carbon content is taken out, and unburned carbon and water are separated. The separated water is returned to the coal ash pretreatment apparatus 1 that has been slurried as recovered water.

  The tail ash is extracted from the extraction port 11 for extracting the tail ash from which the unburned carbon settling in the flotation apparatus 2 is separated and the unburned carbon content is reduced.

  In addition, you may make it isolate | separate iron content as iron oxide from the coal ash slurried with the magnet by arrange | positioning the stirring plate which consists of a perforated rotary plate which incorporated the electromagnet in the flotation apparatus.

  The tail ash is sent to the stabilization processing device 12 arranged downstream of the flotation apparatus 2. In the stabilization processing apparatus 12, air is blown in from the air blowing port 13, and the high alkali component is neutralized to about pH 7 by carbon dioxide in the air, so that the pH can be used for the concrete material.

  The stabilized slurry is compressed by a dehydration apparatus 14 to be a concentrated slurry of coal ash 70 to 80% by mass to be a concrete material.

[ Reference example ]
Table 1 shows the ignition loss value of coal ash used in the experiment and the ignition loss value after flotation.

This reference example is an example of increasing the separation efficiency of unburned carbon by irradiating slurry coal ash with ultrasonic waves.
(1) Ultrasonic irradiation conditions Output was 300 W, a transmission frequency of 950 kHz, and 3 minutes of irradiation were performed for 10 minutes for 10 minutes.

(2) Flotation conditions: Collection agent (kerosene): 1 g, foaming agent (pine oil): 0.06 g, coal ash: 20 g,
Water: 80 g was bubbled for 1 minute.

In Table 1, as seen in the comparative example, conventionally, coal ash that cannot reduce the unburned carbon content to about 5% or less in one flotation is repeatedly burned several times. Carbon was reduced by about 5%. On the other hand, in this reference example, as clearly shown in Table 1, by irradiating the coal slurry with ultrasonic waves, the content of unburned carbon is reliably set to a value suitable for the concrete material by one flotation. It was possible to reduce.

In addition , the content of unburned carbon could be further reduced to 5% or less by performing the flotation multiple times.

  By tailing the tail ash with air, the tail ash having a pH of about 11 was neutralized to a pH of about 7 suitable for the concrete material.

  The tail ash after stabilization treatment is compressed into a concentrated slurry of 70-80%.

  The obtained concentrated slurry was added with water and an admixture, kneaded with cement and aggregate with a mixer, and used as it was as a concrete material.

Table 2 shows the ignition loss value of coal ash used in the experiment and the ignition loss value after flotation.
In this example, slurry pulverized coal ash is stirred by a mixer to increase the separation efficiency of unburned carbon.
(1) Stirring conditions Stirring was carried out for 1 minute at a rotational speed of 10,500 times / minute using a mixer blade.
(2) Flotation conditions: 33.75 g of scavenger (kerosene): 2.025 g of foaming agent (pine oil):
Flotation was carried out with coal ash: 675 g and water: 3,825 g for about 40 minutes.
The results are shown in Table 2.

  As shown in Table 2, the content of unburned carbon could be reduced by stirring with a mixer as a pretreatment for the coal ash stabilization treatment.

1: Slurry coal ash pretreatment device 2: Flotation device 3: Hopper 4: Cylindrical part 5: Input port 6: Slurried coal ash 7: Slurry discharge port 7a: Coal slurry discharge pipe 8: Ultrasonic vibration element 9: Ultrasonic oscillator 10: Air blowing port 11: Extracting port 12: Stabilization processing device 13: Air blowing port 14: Dehydration processing device

Claims (1)

Slurry coal ash which shows acidic pH value by separating unburned carbon from coal ash which is made by slurrying coal ash consisting of coal ash and water containing unburned carbon and slurrying Performs preprocessing to sort,
Unburned carbon scavenger and foaming agent are added to the pretreated slurry coal ash, air is blown to generate bubbles, and floss ash with high unburned carbon content is taken out by flotation, unburned carbon The water separated from water is returned to the pretreatment as recovered water, and iron is separated from the slurryed coal ash as iron oxide by a magnet.
Air is blown into the tail ash from which the unburned carbon has been removed by flotation and neutralized, and then stabilized.
A method for treating coal ash used for a concrete material, wherein the stabilized tail ash is used as a concentrated slurry, and the resulting concentrated slurry is used as a concrete material as it is .