JPH1160299A - Modification of fly ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modification process for fly ash in which the unburned portion in the fly ash is efficiently removed, the fly ash that has not been able to be used conventionally is made possible to be used in the fly ash cement, and in addition, the amounts of alkali and chlorine in the clinker produced in the cement plant can be reduced. SOLUTION: From the top opening of the external heating type rotary kiln, is fed fly ash containing unburned carbon and a part of the combusting gas exhausted from the kiln 26 of the cement plant is introduced into the insulating furnace 5 surrounding the external heating type rotary kiln 4 to heat the fly ash fed at 600-1,000 deg.C to combust the unburned carbon included in the fly ash and remove it. At the same time, the dust D in the exhaust gas from the insulating furnace is recovered and treated outside the system of the cement plant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reforming fly ash generated in a coal-fired thermal power plant or the like, and more particularly to a method for obtaining fly ash which can be used by being mixed with fly ash cement and a cement plant. The present invention relates to a method for modifying fly ash, which can reduce the amounts of alkali and chlorine in the clinker produced in the above.

[0002]

2. Description of the Related Art Fly ash generated in a coal-fired thermal power plant or the like is partially used as a mixture of Portland cement or mixed with cement when producing fly ash cement. However, most of the remaining waste is disposed of by landfill or other methods.

[0003] The composition of fly ash that can be used for fly ash cement is specified in JISA 6210, and the upper limit of ignition loss, which is an alternative property of unburned matter, is specified to be 5% or less. I have.

In recent years, since the NOx content in exhaust gas generated from a pulverized coal combustion boiler has been regulated, unburned components contained in fly ash collected from the pulverized coal combustion boiler exhaust gas have increased. The amount of fly ash that can be used as fly ash specified in the JIS has been greatly reduced, and the amount of fly ash discarded has been further increased.

On the other hand, alkalis and chlorines contained in a cement raw material are volatilized by being exposed to a high temperature in a kiln sintering zone in a cement plant, and then coagulate in a preheater section to cause a coaching trouble. Hinder stable operation. In addition, when a large amount of these remains in the cement clinker, cement is produced by this clinker, and when it is made concrete together with a certain kind of aggregate, an alkali-aggregate reaction is caused to significantly weaken the concrete. There is a risk.

Accordingly, the present invention has been made in view of the above problems, and it is an object of the present invention to efficiently remove unburned components in fly ash and to remove fly ash that could not be used conventionally. It is an object of the present invention to provide a method for reforming fly ash, which is capable of mixing and using the same, and reducing the amounts of alkali and chlorine in clinker produced in a cement plant.

[0007]

According to the first aspect of the present invention,
A method for reforming fly ash, comprising supplying fly ash containing unburned carbon from an upper end opening of an externally heated rotary kiln, and burning gas discharged from a cement plant kiln into an insulated furnace surrounding the externally heated rotary kiln. , And the supplied fly ash is heated to 600 ° C.
To 1000 ° C. to burn and remove unburned carbon contained in the fly ash, collect dust in the exhaust gas from the adiabatic furnace, and treat the dust outside the cement plant.

According to a second aspect of the present invention, in addition to a part of the combustion gas discharged from the kiln of the cement plant, combustion air is introduced into the insulated furnace, and fuel such as heavy oil is burned in the insulated furnace. It is characterized by making it.

The invention according to claim 3 is characterized in that after collecting coarse dust contained in the combustion gas discharged from the kiln of the cement plant, the combustion gas is introduced into the heat insulating furnace.

According to the first aspect of the present invention, fly ash is heated to 600 ° C. to 1000 ° C. to burn and remove unburned carbon contained in the fly ash, and collect dust in the exhaust gas from the adiabatic furnace. Therefore, it is possible to obtain fly ash that can be used by being mixed with fly ash cement, and to reduce the amount of alkali and chlorine in clinker produced in a cement plant.

According to the second aspect of the present invention, since the combustion air is introduced into the insulated furnace and fuel such as heavy oil is burned in the insulated furnace, the temperature of the combustion gas discharged from the kiln of the cement plant is low. In this case, or even when the operation of the kiln of the cement plant is stopped, it is possible to obtain fly ash that can be continuously mixed with fly ash and used.

According to the third aspect of the present invention, after collecting coarse dust contained in the combustion gas discharged from the kiln of the cement plant, the combustion gas is introduced into the heat insulating furnace. In addition, the coarse dust is not solidified on the surface of the externally heated rotary kiln in the heat insulating furnace.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a specific example of an embodiment of the method for modifying fly ash according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a first embodiment of an apparatus for carrying out a method for reforming fly ash according to the present invention, wherein the fly ash reforming apparatus 1 is installed adjacent to a cement plant 2. Is done. In this figure, the flow of a solid substance containing a powdery substance is shown by a solid line, and the flow of a gas substance containing dust is shown by a dotted line.

The fly ash reformer 1 has a receiving tank 3 for receiving fly ash from a coal-fired thermal power plant or the like, and heats the fly ash to burn unburned carbon contained in the fly ash. An externally heated rotary kiln 4 and an insulated furnace 5 for removing by heating, a reformed fly ash cooling device 6 for cooling heated fly ash, and a heat exchange between the exhaust gas of the insulated furnace 5 and cooling air. , A dust collector 8 for collecting dust in exhaust gas from the heat insulating furnace 5, a tank 9 for storing the collected dust, and the like.

The receiving tank 3 is configured to be able to receive the pumped fly ash, and the outlet thereof is provided with a rotary feeder 3a for extracting the received fly ash. A transport machine 10 such as an air slide for transporting the extracted fly ash to the entrance of the externally heated rotary kiln 4 is provided downstream of the receiving tank 3.

The externally heated rotary kiln 4 includes, for example,
A single-cylinder external heat rotary kiln described in JP-A-6-134435 or a multi-cylinder external heat rotary kiln described in JP-B-57-36512 is used.

An inlet chute 4a for receiving fly ash from the transporter 10 is inserted into the upper end opening of the externally heated rotary kiln 4.
Is supplied into the rotary kiln 4 of the external heat type. The fly ash gradually moves in the outlet direction by the rotation of the externally heated rotary kiln 4, and during this movement, the unburned carbon contained therein is burned by the hot gas introduced into the insulated furnace 5 described later.

The insulated furnace 5 is disposed so as to surround the body of the externally heated rotary kiln 4, and a part of the combustion gas G discharged from the kiln 26 of the cement plant 2 from below the insulated furnace 5. The unburned carbon of the fly ash taken in and received by the externally heated rotary kiln 4 is burned by the combustion gas G. Insulation furnace 5
In order to adjust the temperature of the combustion gas introduced into the furnace, a cold air intake damper 12 is provided between the rotary kiln 26 and the heat insulating furnace 5.
Is provided.

The lower part 5a of the heat-insulating furnace 5 is formed in a hopper shape, and is configured to collect coarse dust having a relatively large particle diameter contained in the combustion gas G collected by inertia in the heat-insulating furnace 5. . The collected coarse dust is returned to the preheater 24 of the cement plant 2 by a transporter (not shown).

Downstream of the heat insulating furnace 5, a reforming fly ash cooling device 6 for cooling the fly ash heated in the heat insulating furnace 5 is provided. Although not shown in detail, the reforming fly ash cooling device 6 is, for example, a water-cooled cooling device having a double pipe, in which the reforming fly ash supplied from the supply port 6a passes through the cooling device 6. While passing through and discharging from the discharge port 6b, the cooling water supplied from the water supply port 6c and cooled in the opposite direction to the reforming fly ash is configured to be cooled. The cooling water is discharged from the drain 6d.

The fly ash discharged from the cooling device 6 is used as modified fly ash F by mixing it with cement when producing fly ash cement. In addition to the water-cooled cooling device, for example, an air-cooled cooling device described in JP-A-6-134435 can also be used.

The heat exchanger 7 is provided for exchanging heat between the exhaust gas of the insulated furnace 5 and the cooling air. The exhaust gas of the insulated furnace 5 is guided from the exhaust gas supply port 7a to the heat exchanger 7 and is cooled. The heat is exchanged with the cooling air supplied from the air supply port 7b. The exhaust gas from the heat-insulating furnace 5 whose temperature has been lowered by heat exchange with the cooling air is guided to the dust collector 8 from the exhaust gas outlet 7c.

On the other hand, part of the cooling air whose temperature has risen is returned to the heat insulating furnace 5 from the cooling air discharge port 7d, and the rest is released to the atmosphere. Further, a rotary feeder 7e is provided at a lower portion of the heat exchanger 7 in order to extract dust in the exhaust gas of the heat insulating furnace 5 collected in the heat exchanger 7, and the dust extracted by the rotary feeder 7e is transported (not shown). It is transported to the tank 9 via the route.

The dust collector 8 is provided with an exhaust gas outlet 7c of the heat exchanger 7.
For example, a bag-type dust collector is used to collect dust in the exhaust gas of the heat-insulating furnace 5 guided from the furnace. The exhaust gas from the heat insulating furnace 5 guided to the dust collector 8 is discharged to the atmosphere from the discharge port 8b after dust is removed. Also,
In order to transport the collected dust to the tank 9, a rotary feeder 7e and a transporter (not shown) are provided.

The tank 9 is provided for collecting and storing dust collected by the heat exchanger 7 and the dust collector 8.
The dust D collected in the tank 9 originally contains a large amount of alkali and chlorine which should be contained in a clinker manufactured in the cement plant 2 described below.
This dust D is disposed of outside the cement plant 2.

Next, the cement plant 2 adjacent to the fly ash reforming apparatus 1 will be described. The cement plant 2 includes a suspension play heater 24 provided with a plurality of cyclones 23, a calciner 25, a rotary kiln 26, a clinker cooling device 28, and the like. Thereafter, it is calcined in a calciner 25 and calcined in a rotary kiln 26 to become a cement clinker. The cement clinker is cooled by a clinker cooling device 28 and temporarily stored in a clinker silo (not shown) and then sent to a finishing step.

In the above process, the alkalis and chlorine contained in the cement raw material M are volatilized by being exposed to a high temperature in the sintering zone of the rotary kiln 26, and then coagulate in the suspension preheater 24 to generate a coating trouble. Or hinder stable operation.
Further, if a large amount of alkalis and chlorines remain in the clinker, as described above, an alkali-aggregate reaction may be caused and concrete may be significantly weakened, so that a part of the combustion gas G discharged from the rotary kiln 26 is removed. Extraction is being done. In the present invention, the combustion gas G is introduced into the externally heated rotary kiln 4 of the fly ash reformer 1.

Next, referring to FIG. 1, the fly ash reforming apparatus 1 according to the present embodiment obtains fly ash which can be used by being mixed with fly ash cement, and is manufactured in a cement plant. The step of reducing the amounts of alkali and chlorine in the clinker will be described.

Fly ash from a coal-fired thermal power plant or the like is received by the receiving tank 3 and extracted from the receiving tank 3 by the rotary feeder 3a.
0 transports to the externally heated rotary kiln 4.
Then, fly ash is supplied into the externally heated rotary kiln 4 from the upper opening through the inlet chute 4a,
It moves to the outlet side with the rotation of the externally heated rotary kiln 4.

On the other hand, part of the combustion gas G discharged from the rotary kiln 26 of the cement plant 2 is approximately 100%.
Although the temperature is about 0 ° C., the combustion gas G is directly introduced into the insulated furnace 5 or the combustion gas G is introduced into the cold air intake damper 12.
The temperature is lowered to about 600 ° C. at the lowest temperature by introducing cooler air, and then introduced into the heat insulating furnace 5. The temperature of the combustion gas G discharged from the heat insulating furnace is about 800 ° C. to 900 ° C.
It is preferable to control the temperature of the combustion gas at the inlet of the adiabatic furnace 5 so that the temperature of the insulated furnace 5 is set to ℃.

Then, the unburned carbon contained in the fly ash moving in the externally heated rotary kiln 4 is burned by the combustion gas G and removed from the fly ash. This combustion reduces, for example, the unburned carbon content of the received fly ash at about 6% by weight to about 1% by weight after combustion.

In the externally heated rotary kiln 4, the fly ash in which the unburned carbon contained therein is burned is then supplied to a reformed fly ash cooling device 6, which is cooled with water to lower the temperature. It is used as a mixture with cement when producing fly ash cement.

On the other hand, the combustion gas G introduced into the heat insulating furnace 5
In the hopper-shaped lower portion 5a, coarse dust having a relatively large particle size contained in the combustion gas G is collected by inertial dust collection.
And returned to the suspension preheater 24 of the cement plant 2. Since the content of alkali and chlorine in the coarse powder dust is small, even if the dust is returned to the suspension preheater 24, it does not increase the alkali and chlorine in the clinker manufactured in the cement plant 2.

The combustion gas G introduced into the adiabatic furnace 5 from which coarse dust has been removed has a temperature of about 850 ° C., is supplied to the heat exchanger 7 and exchanges heat with the cooling air. The exhaust gas from the heat-insulating furnace 5 whose temperature has been lowered by heat exchange with the cooling air is guided to the dust collector 8 from the exhaust gas outlet 7c. On the other hand, part of the cooling air whose temperature has increased to about 400 ° C. due to heat exchange with the combustion gas G is returned to the insulated furnace 5 and used as a part of the heat source of the insulated furnace 5, and the rest is released to the atmosphere. Released.

In the heat exchanger 7, a part of the fine powder of the dust contained in the combustion gas G is recovered, and the fine dust is extracted by the rotary feeder 7e and then transported to the tank 9.

Further, the combustion gas G discharged from the heat exchanger 7 becomes approximately 150 ° C. at the inlet of the dust collector 8,
Here, the remaining fine dust contained in the combustion gas G is collected and collected in the tank 9 via the rotary feeder 8c.

The fine dust D contained in the combustion gas G transported from the heat exchanger 7 and the dust collector 8 to the tank 9 contains a large amount of alkali and chlorine contained in the cement raw material M supplied to the cement plant 2. By recovering this and treating it outside the system of the cement plant 2, the amount of alkali and chlorine in the clinker manufactured in the cement plant 2 can be reduced.

Next, a second embodiment of the apparatus for carrying out the fly ash reforming method according to the present invention will be described with reference to FIG. In this embodiment, the same devices as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. Also in this embodiment, the fly ash reforming apparatus 31 is installed adjacent to the cement plant 2 and, in FIG. Is indicated by a dotted line.

The fly ash reforming device 31 includes a receiving tank 3 for receiving fly ash from a coal-fired thermal power plant or the like, an externally heated rotary kiln 4, an insulated furnace 5, a reforming fly ash cooling device 6, , Heat exchanger 7
, A dust collector 8 and a tank 9 are the same as in the first embodiment, but in this embodiment, the heat exchanger 3
2, a cyclone 33, and a fuel supply device for heavy oil or the like are provided.

The combustion gas G discharged from the rotary kiln 26 of the cement plant 2 is introduced into the heat exchanger 32 through an exhaust gas supply port 32a, and is supplied to a combustion air supply port 32b.
And heat exchange with the combustion air guided to the insulated furnace 5. The combustion gas G whose temperature has been lowered by heat exchange with the combustion air is guided to the cyclone 33 from the exhaust gas outlet 32c. On the other hand, the combustion air whose temperature has increased is supplied to the insulated furnace 5 from the combustion air outlet 32d.

In order to extract coarse dust having a relatively large particle diameter in the combustion gas G recovered in the heat exchanger 32, a rotary feeder 32e is provided below the heat exchanger 32.
Is provided, and the extracted coarse dust is returned to the preheater 24 of the cement plant 2 via a transporter (not shown).

The cyclone 33 is provided for collecting coarse dust having a relatively large particle diameter in the combustion gas G introduced through the heat exchanger 32. The combustion gas G introduced from the exhaust gas outlet 32 c of the heat exchanger 32 is introduced into the inlet 33 a of the cyclone 33, and the coarse dust collected when the combustion gas G passes through the inside of the cyclone 33 is removed. A rotary feeder 33d is provided for extraction. Then, the collected coarse powder dust is returned to the preheater 24 of the cement plant 2 via a transporter (not shown). Further, the combustion gas G discharged from the outlet 33 b of the cyclone 33 is led to the heat insulating furnace 5.

The heat insulating furnace 5 is provided with a supply port (not shown) for introducing the combustion air from the heat exchanger 32 in addition to the structure shown in the first embodiment.
A fuel supply device (not shown) for supplying fuel O such as heavy oil in the heat insulating furnace 5 is provided. In addition, the cement plant 2 adjacent to the fly ash reformer 31
The configuration is the same as that of the embodiment.

Next, referring to FIG. 2, the fly ash reforming apparatus 31 according to the present embodiment obtains fly ash which can be used by being mixed with fly ash cement, and is manufactured in a cement plant. The step of reducing the amounts of alkali and chlorine in the clinker will be described.

Fly ash from a coal-fired power plant or the like is received in the receiving tank 3 and is supplied to the rotary feeder 3.
After being extracted by a, it is transported to the externally heated rotary kiln 4 by the transporter 10. Then, it is supplied to the inside from the upper opening of the externally heated rotary kiln 4 via the inlet chute 4a, and gradually moves to the outlet side as the externally heated rotary kiln 4 rotates.

On the other hand, part of the combustion gas G discharged from the rotary kiln 26 of the cement plant 2 is approximately 100%.
Although the temperature is about 0 ° C., the combustion gas G is supplied to the heat exchanger 3
2 and heat exchange with the air introduced into the cyclone 33 to heat this air.

By exchanging heat with the combustion gas G, about 4
The air that has reached 00 ° C. is introduced into the heat insulating furnace 5 and is used as combustion air. On the other hand, the combustion gas G is introduced into the cyclone 33 at about 350 ° C., where a part of the coarse dust having a relatively large particle size is removed. The removed coarse dust is returned to the suspension preheater 24 of the cement plant 2. In addition, since the alkali and chlorine content of the coarse dust collected in the heat exchanger 32 and the cyclone 33 are small, even if the dust is returned to the suspension preheater 24, the alkali in the clinker produced in the cement plant 2 It does not increase the chlorine content.

Since the temperature of the combustion gas G guided from the cyclone 33 to the heat insulating furnace 5 has dropped to about 330 ° C., in this embodiment, the fuel O such as heavy oil in the heat insulating furnace 5 is used.
Need to be fired. For that purpose, the combustion air from the above-described heat exchanger 32 is used. The combustion of the fuel O controls the gas temperature at the outlet of the adiabatic furnace 5 to 800 ° C. to 900 ° C.

By the heat insulating furnace 5 maintained at a high temperature, unburned carbon contained in the fly ash moving in the externally heated rotary kiln 4 is burned and removed from the fly ash. The amount of unburned carbon to be removed is the same as in the first embodiment.

Thereafter, as in the case of the first embodiment, the fly ash in which the unburned carbon is burned in the externally heated rotary kiln 4 is then converted into a modified fly ash cooling device
After being cooled in, as modified fly ash F,
It is used as a mixture with cement when producing fly ash cement. In addition, the exhaust gas from the heat insulating furnace 5 exchanges heat with cooling air.

Further, the fine dust contained in the exhaust gas from the heat insulating furnace 5 is collected in the heat exchanger 7 and the dust collector 8, and the fine dust is removed from the alkali contained in the cement raw material M supplied to the cement plant 2. Since it contains a large amount of chlorine, it is possible to reduce the amount of alkali and chlorine in the clinker produced in the cement plant 2 by collecting and treating this outside the cement plant 2.

According to the present embodiment, the cyclone 33 removes coarse dust contained in the combustion gas G discharged from the rotary kiln 26 of the cement plant 2 in advance. It is possible to prevent the occurrence of solidification of coarse dust on the surface of the externally heated rotary kiln 4 in the furnace 5 and to continue the operation in a stable state for a long time.

Further, in this embodiment, the temperature of the combustion gas G introduced into the heat insulating furnace 5 is set low in order to prevent solidification or the like, or the cement plant 2 is not used for some reason.
Even when the operation is stopped, there is an advantage that the operation of the fly ash reforming apparatus 31 can be continued by introducing the combustion air into the adiabatic furnace 5 and burning the fuel O such as heavy oil.

The fly ash modified by the method according to the present invention can be used as a mixed material of Portland cement in addition to being used by mixing it with fly ash cement.

[0055]

According to the first aspect of the present invention, it is possible to obtain fly ash which can be used by being mixed with fly ash cement, and to reduce the amount of alkali and chlorine in clinker produced in a cement plant. A method for modifying fly ash that can be reduced can be provided.

According to the second aspect of the present invention, even if the temperature of the combustion gas discharged from the kiln of the cement plant is low, or the operation of the kiln of the cement plant is stopped, the fly ash cement is continuously provided. And a method for modifying fly ash, which can obtain fly ash that can be used in a mixed state.

According to the third aspect of the present invention, the coarse dust is not condensed on the inside of the insulated furnace and on the surface of the externally heated rotary kiln in the insulated furnace, and the operation is stable for a long period of time. Can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a first embodiment of an apparatus for carrying out a fly ash reforming method according to the present invention.

FIG. 2 is a schematic view showing a second embodiment of the apparatus for carrying out the fly ash reforming method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fly ash reformer 2 Cement plant 3 Receiving tank 4 External heating rotary kiln 5 Insulation furnace 6 Reforming fly ash cooling device 7 Heat exchanger 8 Dust collector 9 Tank 10 Transporter 12 Cold air intake damper 23 Cyclone 24 Suspension play heater 25 Calcination furnace 26 Rotary kiln 28 Clinker cooling device 31 Fly ash reforming device 32 Heat exchanger 33 Cyclone D Dust F Modified fly ash G Combustion gas M Cement raw material O Fuel

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yukio Nakazaki 1-6-1 Otemachi, Chiyoda-ku, Tokyo Japan Cement Co., Ltd.

Claims (3)

[Claims] 1. A fly ash containing unburned carbon is supplied from an upper end opening of an externally heated rotary kiln, and a part of combustion gas discharged from a cement plant kiln is introduced into an insulated furnace surrounding the externally heated rotary kiln. Then, the supplied fly ash is heated to 600 ° C. to 1000 ° C. to burn and remove unburned carbon contained in the fly ash, and collect dust in the exhaust gas from the adiabatic furnace. A method for modifying fly ash, characterized by treating it outside. 2. A combustion air is introduced into the insulated furnace in addition to a part of the combustion gas discharged from the kiln of the cement plant, and fuel such as heavy oil is burned in the insulated furnace. The method for modifying fly ash according to claim 1. 3. The method according to claim 1, wherein after collecting coarse dust contained in the combustion gas discharged from the kiln of the cement plant, the combustion gas is introduced into the insulated furnace. Method for reforming fly ash.