JPH0783864B2 - Fly ash processing equipment - Google Patents

Description

The present invention relates to equipment for treating fly ash discharged from a refuse incinerator or the like.

[Conventional technology]

Fly ash collected by the dust collector from the exhaust gas discharged from the refuse incinerator may cause a problem if heavy metal or salt is eluted if it is filled up as it is. As a countermeasure against this, the dust is once dissolved in water, and this slurry is mixed with the exhaust gas (CO ₂ ) after fly ash dust collection to neutralize it, thereby making the heavy metal in the fly ash into a stable state called a carbonate compound. The method of doing is adopted. The fly ash slurry conventionally treated in this way is sent to the wastewater treatment facility of a refuse incineration plant and treated together with the waste liquid generated from other facilities.

[Problems to be solved by the invention]

However, in fly ash treatment equipment, fly ash needs to be dissolved in water at a concentration of about 2 to 5% in order to react with exhaust gas, so a large amount of fly ash slurry is discharged from the treatment equipment. As a result, there has been a problem that a wastewater treatment facility of a refuse incineration plant requires a very large facility, which results in a high operating cost.

In addition, since a large amount of water is required to dissolve the fly ash, there is a drawback in that the operating cost is also increased in this respect.

The present invention has been made in view of such conventional problems,
An object of the present invention is to provide a facility capable of treating neutralized fly ash slurry simply and at low cost without passing through wastewater treatment facilities in a refuse incineration plant.

[Means for solving problems]

Therefore, the present invention, the fly ash slurry after the neutralization treatment need only the suspension treatment, pH adjustment, such as performed in the drainage from other equipment of the refuse incineration plant, heavy metal treatment Focusing on the fact that it is not necessary to treat bacteria, etc., we have developed an apparatus that can treat fly ash slurry independently and easily and at low cost.

That is, the first feature of the present invention is that a dehydrator for dehydrating the fly ash slurry is provided downstream of the neutralization tank, and a filter for filtering desorbed water discharged from the dehydrator. There is a device.

The second feature of the present invention is that a settling tank for settling solids in the fly ash slurry is provided downstream of the neutralization tank, and a slurry extracted from the lower part of the settling tank is dehydrated. Dewatering device, a dewatering water discharged from the dewatering device and a fly ash slurry discharged from the settling tank, and a filtering device for filtering a part of the supernatant water of the fly ash slurry, and the remaining fly ash slurry discharged from the settling tank It has an environmental water pipe for supplying the supernatant water to the dissolution tank.

[Action]

Fly ash discharged from the dust collector is dissolved in water in the dissolution tank,
The heavy metal in the dissolved fly ash is neutralized by the exhaust gas after fly ash dust collection in the neutralization tank to become a carbonate compound,
It will be included in the fly ash slurry as part of the suspension (SS). In the first invention of the present application, most of the neutralized fly ash slurry is sent to the dehydrator on the downstream side of the neutralization tank, most of the suspension is removed as a dehydrated cake, and the desorbed water discharged from the dehydrator is Further, it is sent to a filtration device on the downstream side and discharged with the residue after dehydration removed.

Further, in the second invention of the present application, the fly ash slurry is sent from the neutralization tank to the settling tank, where the suspension in the slurry settles to the bottom of the tank. High-concentration fly ash slurry is drawn from the bottom of the settling tank and transferred to a dehydrator, where most of the suspended matter in the slurry is removed and discharged as a dehydrated cake. The desorbed water discharged from the dewatering device is sent to the filtering device to remove the residue. Also, the supernatant water discharged from the settling tank is circulated for reuse by being returned to the dissolution tank via a circulating water pipe, but part of it is drawn out of the system to adjust the salt concentration of the circulation system. The water is removed from the dehydrator and treated with the filtration device. Therefore, the circulation system is newly replenished with water commensurate with the drawn water. By providing a settling tank in this way, part of the water in the system can be circulated and used, and the amount of water supplied from outside the system to dissolve fly ash can be kept low. Since the converted slurry is sent, efficient dehydration processing can be performed with a small dehydrator.

〔Example〕

FIG. 1 shows the basic configuration of the first invention of the present application. In the figure, (A) is an exhaust gas neutralization treatment apparatus, which is a dissolution tank (1) for dissolving fly ash in water, and a fly ash slurry discharged from the dissolution tank after dust collection treatment. It is composed of a neutralization tank (2) for neutralizing with exhaust gas.

In the present invention, the dehydrator (3) and the filter (4) are arranged in this order on the downstream side of the exhaust gas neutralization treatment device (A).

The dehydrator (3) dehydrates the fly ash slurry sent from the neutralization tank (2) and can discharge the suspension as a dehydrated cake. The filtration device (4) can filter the desorbed water discharged from the dewatering device (3) to remove a residue in the desorbed water.

FIG. 2 shows a more specific embodiment based on the basic configuration of FIG. In the figure, (A) is an exhaust gas neutralization treatment facility comprising a dissolution tank (1) and a neutralization tank (2).

The dissolution tank (1) includes a stirrer (19), and can dissolve the fly ash discharged from the dust incinerator (22) and collected by the dust collector (23) with dissolved water. It is becoming like this.
Here, fly ash is dissolved to a concentration of about 2 to 5%.

The neutralization tank (2) is a stirring body (2
0), and the agitator (2) from the gas supply pipe (21).
0) The neutralization reaction is promoted by releasing the gas downward.

A dehydrator (3) and a filter (4) are provided on the downstream side of the exhaust gas neutralization treatment facility (A).
In this embodiment, a dewatering device supply storage tank (6) is provided between the neutralization tank (2) and the dewatering device (3), and a sedimentation tank is provided between the dewatering device (3) and the filtering device (4). (7) is provided.

The dewatering device supply storage tank (6) temporarily stores the fly ash slurry discharged from the neutralization tank (2) before transferring it to the dewatering device (4) and returns the residue from the settling tank (7). The fly ash slurry stored in the storage tank (6) can be extracted by the pump (18) and transferred to the dehydrator (3).

The settling tank (7) is provided to remove residues from the desorbed water discharged from the dehydrator (3). The dehydration efficiency of the dehydrator (3) is about 90%, and if the desorbed water discharged from the dehydrator (3) is filtered as it is, it will cause clogging of the filter (4). 7) is provided so that the residue in the desorbed water can be settled and removed from the bottom of the tank. This settling tank (7) has an overflow tank (71), and the debris of the desorbed water settles at the bottom of the tank, and the supernatant water is the overflow tank (71).
Flow to the filter device (4). On the other hand, the residue settled at the bottom of the tank is returned to the dehydration apparatus supply storage tank (6) by a return pipe (13).

In addition to the above configuration, a filtered water tank (8) is provided on the downstream side of the filtration device (4), and the desorbed water discharged from the filtration device (4) is temporarily stored in this filtered water tank (8). After that, it is being released.

Further, in order to backwash the filtration device (4), it is possible to supply the filtration device (4) from the filtered water tank (8) to the filtration device (4) through the pipe (14). A washing tank (9) is separately provided. The backwash water (slurry) can be returned to the dehydration device supply storage tank (6) by a return pipe (15).

In addition, the upstream piping of the dehydrator (3) and the filter (4)
Polymer coagulants are injected from the tanks (16) and (17) into the upstream side pipes as a dehydration aid and a filter aid, respectively.

In the other drawings, (18) is a pump.

FIG. 3 shows the basic configuration of the second invention of the present application.
In the present invention, the settling tank (5) is arranged on the downstream side of the exhaust gas neutralization treatment apparatus (A), and the dehydrating apparatus (3) and the filtering apparatus (4) are arranged in that order on the downstream side.

The settling tank (5) temporarily stores the fly ash slurry discharged from the neutralization tank (2) before transferring it to the dehydrator (3),
It is used to settle the suspension in the fly ash slurry so that the fly ash slurry can be withdrawn at a high concentration from the bottom of the tank and transferred to the dehydrator (3).

Between this sedimentation tank (5) and the dissolution tank (1), circulating water piping (11) for circulating and using the supernatant water in the sedimentation tank (5) to the dissolution tank (1) in the system ) Is provided.

In addition, in order to adjust the salt concentration of the circulation system in this way, a part of the supernatant water is drawn out of the system, and a drawing pipe (12) for sending this to the filtration device (4) is provided. It is provided.

FIG. 4 shows a more specific embodiment based on the basic configuration of FIG.

In the present invention, a settling tank (5), a dehydrator (3) and a filter (4) are provided on the downstream side of the exhaust gas neutralization equipment (A), but in the present embodiment, the implementation shown in FIG. 2 is carried out. Similar to the example
A dehydration device supply storage tank (6) is provided on the upstream side of the dehydration device (3).
Further, settling tanks (5) are respectively provided on the upstream side of the filtration devices (4).

The settling tank (5) has an overflow tank (51), and the suspension of the supplied fly ash slurry settles to the bottom of the tank, and the supernatant water flows into the overflow tank (51). ing. High concentration slurry at the bottom of the tank is pumped (18)
And sent to the dehydration device supply storage tank (6),
On the other hand, the supernatant water flowing into the overflow tank (51) can be returned to the dissolution tank (2) through the circulating water pipe (11). Further, a withdrawal pipe (12) is connected to the overflow tank (51) so that a part of the supernatant water can be withdrawn to the outside of the system and sent to the filtration device (4).

In addition, in other drawings, (10) is a makeup water tank,
Water corresponding to the drawn water is supplied from the makeup water tank (10) to the circulation system (dissolution tank (2)). Since the other structure is the same as that of the embodiment shown in FIG. 2, its explanation is omitted.

Next, the operation of each embodiment described above will be described.

In the embodiment shown in FIG. 1 according to the first invention of the present application, fly ash is dissolved in water in the dissolution tank (1), and the heavy metal in the dissolved fly ash is collected in the neutralization tank (2). It is neutralized by the exhaust gas after dusting to become a carbonic acid compound, which is included in the fly ash slurry as a part of the suspension. The fly ash slurry thus neutralized is sent to the dehydrator (3) on the downstream side of the neutralization tank (2), and most of the suspended matter is removed as a dehydrated cake. The discharged desorbed water is sent to the filter device (4) on the further downstream side and is discharged after the residue after dehydration is removed. In the embodiment shown in FIG. 2, the fly ash discharged from the dust incinerator (22) and collected by the dust collector (23) is mixed with water while being stirred by the stirrer (19) in the dissolution tank (1). And then neutralized by the exhaust gas while being stirred by the stirring body (20) in the neutralization tank (2). The fly ash slurry thus neutralized is sent to the dewatering device supply storage tank (6) on the downstream side of the neutralization tank (2) and once stored there, and then dewatered on the downstream side by the pump (18). It is sent to the device (3) and most of the suspension is removed as a dehydrated cake. The desorbed water discharged from the dehydrator (3) is sent to the settling tank (7) on the downstream side thereof. In the settling tank (7), the residues in the desorbed water settle at the bottom of the tank, and the supernatant water flows into the overflow tank (71). This supernatant water is drawn by a pump (18) and sent to a filter device (4) on the downstream side thereof, and after the residue is removed by the filter device (4), it is sent to a filtered water tank (8) on the downstream side, Then it is released. Further, the residue (slurry) settled at the bottom of the settling tank (7) is withdrawn from the bottom of the tank, returned to the dehydration device supply storage tank (6) through a return pipe (13), and is treated again together with the fly ash slurry. Further, the filtering device (4) is regularly washed with water which is sent back from the filtered water tank (8) through the pipe (14) and the pump (18). This backwash water (slurry) is backwashed ( It is returned to the dehydration device supply storage tank (6) through the return pipe (15) via 9), and dehydration and filtration are performed again.

Further, in the embodiment shown in FIG. 3 according to the second invention of the present application,
The fly ash slurry neutralized in the same manner as in the example shown in FIG. 1 is sent to the settling tank (5) on the downstream side of the neutralization tank (2), where the suspension in the slurry is transferred to the bottom of the tank. Settle. A high-concentration fly ash slurry is drawn from the bottom of the settling tank (5) and transferred to the dehydrator (3), and most of the suspended matter in the slurry is removed and discharged as a dehydrated cake. The desorbed water discharged from the dehydrating device (3) is sent to the filtering device (4), where the residue is removed. Also, the supernatant water discharged from the settling tank (5) is circulated and used by being returned to the dissolution tank (1) through the circulating water pipe (11), but for adjusting the salt concentration of the circulation system, etc. A part of the water is withdrawn from the system by the withdrawal pipe (12) and treated with the desorption water from the dehydration device (3) in the filtration device (4). Therefore, the circulation system is newly replenished with water commensurate with the drawn water. Further, in the embodiment of FIG. 4, the fly ash slurry neutralized in the same manner as in FIG. 2 has a settling tank (5) downstream of the neutralization tank (2).
And the suspension in the fly ash slurry settles at the bottom of the tank. The high-concentration slurry at the bottom of the tank is withdrawn by the pump (18) and sent to the dehydrator supply storage tank (6) where it is temporarily stored, after which the same process as in the embodiment shown in FIG. Is released. On the other hand, the supernatant water that has flowed from the pre-sedimentation tank (5) to the overflow tank (51) is returned to the dissolution tank (1) through the circulating water pipe (11). The part is drawn out from the drawing pipe (12) and sent to the filtration device (4). In this embodiment,
A polymer flocculant is added as a dehydration aid or a filtration aid to the inlet side of the dehydrator (3) or the filter (4), and the flocculant is discharged from the settling tank (7) or the slurry or the filter (4). ) Will be included in the backwash water. As described above, the present invention adopts the circulation system of the dissolved water using the settling tank (5). However, if the coagulant enters the circulation system, the neutralization reaction of exhaust gas is hindered. , It adheres to the device and causes a problem. In this regard, in this embodiment, the slurry from the settling tank (7) and the backwash water of the filtering device (4) are not stored in the settling tank (5) but in the dehydrator supply storage tank (6) provided downstream thereof.
Since the polymer coagulant is returned to the above, there is no risk that the polymer coagulant is mixed in the circulation system.

The table below shows the water quality of the effluent after treatment by the equipment shown in Fig. 4 analyzed by the beaker test, and the analyzed values were compared with the river discharge standard. You can see that you are doing.

[Effects of the Invention] According to the equipment of the present invention as described above, the fly ash slurry after the exhaust gas neutralization treatment can be treated with simple equipment and at low cost.

Further, according to the second invention of the present application, in addition to the above effects, by providing a settling tank, a part of the fly ash slurry after the fly ash neutralization treatment is circulated and used as dissolved water for the neutralization treatment. As a result, the amount of discharged water can be suppressed and the amount of fresh water used for neutralization can be suppressed. Therefore, the facility for treating fly ash slurry can be simplified and the facility operating cost can be reduced. Further, since the high-concentration fly ash slurry is sent to the dehydrator by providing the settling tank, the amount of slurry processed in the dehydrator can be reduced and the dehydrator can be downsized.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the basic configuration of the first invention of the present application.
FIG. 2 is an explanatory diagram showing a more specific embodiment based on the basic configuration of FIG. FIG. 3 is an explanatory diagram showing the basic configuration of the second invention of the present application. FIG. 4 is an explanatory diagram showing a more specific embodiment based on the basic configuration of FIG. In the figure, (1) is a dissolution tank, (2) is a neutralization tank, and (3)
Is a dehydrator, (4) is a filter, (5) is a sedimentation tank, and (1
1) shows circulating water pipes.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinari Fujisawa Marunouchi 1-2-2, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Yoji Ogaki 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Date Inside this steel pipe company (56) Reference JP-A-53-12165 (JP, A) JP-B-56-9390 (JP, B2)

Claims (6)

[Claims] 1. A fly having a dissolution tank for dissolving fly ash discharged from a dust collector in water, and a neutralization tank for neutralizing fly ash slurry with exhaust gas after fly ash dust collection. In the ash treatment facility, a downstream of the neutralization tank is provided with a dehydrator for dehydrating the fly ash slurry, and a filter for filtering desorbed water discharged from the dehydrator. Fly ash processing equipment. 2. A sedimentation tank is provided between the dehydrating device and the filtering device to settle the residue in the desorbed water discharged from the dehydrating device and discharge the supernatant water to the filtering device. The fly ash treatment facility according to claim 1, further comprising a return pipe for drawing out the slurry and returning the slurry to the upstream side of the dehydrator. 3. The fly ash treatment facility according to claim 1, further comprising a return pipe for returning the backwash water of the filtering device to the upstream side of the dehydrating device. 4. A fly tank having a dissolution tank for dissolving fly ash discharged from a dust collector in water and a neutralization tank for neutralizing fly ash slurry with exhaust gas after fly ash dust collection. In the ash treatment facility, a settling tank for settling the suspension in the fly ash slurry, a dehydrator for dehydrating the slurry drawn out from the lower part of the settling tank, and the dehydrator The desorption water discharged from the equipment and the filtration device for filtering a part of the fly ash slurry supernatant liquid discharged from the sedimentation tank, and the remaining fly ash slurry supernatant water discharged from the sedimentation tank are supplied to the dissolution tank. Fly ash processing equipment, which has a circulating water pipe for 5. A sedimentation tank is provided between the dewatering device and the filtering device to settle the debris in the desorbed water discharged from the dewatering device and discharge the supernatant water to the filtering device. The fly ash treatment facility according to claim 4, further comprising a return pipe for extracting the slurry and returning the slurry to the upstream side of the dehydrator. 6. The fly ash treatment facility according to claim 4, further comprising a return pipe for returning the backwash water of the filtration device to the upstream side of the dehydration device.