WO2005028379A1

WO2005028379A1 - Method and apparatus for treating drain water from step of washing fly ash with water

Info

Publication number: WO2005028379A1
Application number: PCT/JP2003/012095
Authority: WO
Inventors: Shinichiro Saito; Tomomichi Nakamura; Noritoshi Tamura
Original assignee: Taiheiyo Cement Corporation
Priority date: 2003-09-22
Filing date: 2003-09-22
Publication date: 2005-03-31
Also published as: TW200512036A; AU2003264549A1

Abstract

A method for treating drain water from a step of washing a fly ash with water, wherein the drain water is subjected to pH adjustment in a gas absorption reaction/degasification vessel (21), precipitates are removed from the drain water in a first sloped plate sedimentation vessel (22) and a second sloped plate sedimentation vessel (24), suspended matters are removed from the drain water in a film filtration device (25), and precipitates removed in a first sloped plate type sedimentation vessel (22) and a second sloped plate type sedimentation vessel (24) and suspended matters removed in a film filtration device (25) are subjected to solid-liquid separation in a filter press (15). The solids separated are utilized as a part of a raw material for cement.

Description

Method and apparatus for treating fly ash washing wastewater

[Technical field]

The present invention relates to a method and an apparatus for treating wastewater generated by washing incineration fly ash discharged from incineration equipment or the like.

[Background technology]

Conventionally, combustible household waste and industrial waste are incinerated in waste incinerators, such as strike-type incinerators, fluidized-bed incinerators, melt-incinerators, Rho-Lee kilns, and batch furnaces. The incinerated ash was landfilled at the final waste disposal site, but this incinerated ash contains C a 0, S i 0 ₂ , 8 1 ₂ 0 ₃ and 6 ₂ 0 ₃ etc. necessary as cement raw materials. Therefore, it can be sufficiently recycled as a raw material for cement firing. In the cement sintering process, the raw materials are exposed to a high temperature of more than 140 ° C, so that dioxins contained in the incineration ash can be decomposed, and heavy metals are contained in cement clinker minerals. Can be captured and fixed.

For these reasons, in recent years, cement manufacturing technology using incinerated ash as a part of raw materials has been established, and incinerated main ash and incinerated fly ash have been recycled into cement. Normally, incinerated main ash is used as a raw material for cement after only removing iron by magnetic separation and removing foreign matter by sieving. On the other hand, incinerated fly ash contains a high concentration of chlorine in the form of NaC1, etc., and the chlorine component is removed by water washing to prevent a negative effect on the stable operation of the kiln and the quality of cement. Is followed by a cement raw material.

The incinerated fly ash is turned into a slurry in warm water and supplied to a solid-liquid separator such as a belt filter, where it is sprinkled from above and, at the same time, is moved above the belt filter while water is suctioned from below and washed with water. Desalting and solid-liquid separation immediately. The fly ash cake remaining on the belt fill is used as a raw material for cement, while the filtrate in which the chlorine component is dissolved contains heavy metals contained in the incinerated fly ash, as shown in Fig. 3, for example. Was treated by a simple batch-type wastewater treatment device.

The filtrate contained in the filtrate tank 1 is sent to the carbon dioxide gas reaction tank 2, where it is contained in the filtrate. Metal ions react with a large amount of carbon dioxide contained in the kiln exhaust gas and are neutralized. The filtrate is degassed in the degassing tank 3, the sediment is removed in the sedimentation tanks 4 and 5, the finishing agent is added in the chemical reaction tank 7 through the first supernatant water tank 6, and then the sedimentation tank 8 The precipitate is removed at. Further, the water is filtered in the sand filtration tanks 10 and 11 through the second supernatant water tank 9, stored in the treatment water tank 13 through the Hg adsorption tank 12, and discharged. The sediment removed in sedimentation tanks 4, 5 and 8 is stored in sludge pit 14 and then separated into solid and liquid by filtration press 15 and water is returned from filtration water tank 16 to carbon dioxide gas reaction tank 2. Is performed. In addition, the sand filtration tanks 10 and 11 and the Hg adsorption tank 12 require backwashing, and the backwash water generated at this time is sent from the backwash water pit 17 to the sludge bit 14 and filled. It is separated into solid and liquid by a press 15.

As described above, conventionally, wastewater treatment requires a large number of treatment equipment, and the equipment becomes complicated and the equipment cost increases. In addition, since batch processing was performed, not only did each tank increase in size, but also scales were easily generated due to the filtrate coming into contact with the atmosphere, which required a great deal of labor and time for equipment maintenance.

[Disclosure of the Invention]

The present invention has been made to solve such a problem, and an object of the present invention is to provide a method and an apparatus for treating fly ash washing wastewater which have a simple configuration, have low equipment costs, and can be easily maintained. And

The method for treating fly ash washing wastewater according to the present invention is a method for treating wastewater when fly ash is dissolved in water and desalted, and after adjusting the pH of the wastewater, from the wastewater adjusted for pH. This is a method in which sediment is removed by an inclined plate sedimentation tank, and suspended solids are removed from the wastewater from which the sediment has been removed by a membrane filtration device.

Furthermore, a finishing agent may be added to the wastewater from which the sediment has been removed in the inclined plate sedimentation tank, and the sediment may be removed from the wastewater to which the finishing agent has been added by the second inclined plate sedimentation tank. Good. In this case, suspended matter is removed by a membrane filtration device from wastewater from which sediment has been removed in the second inclined plate settling tank.

It is preferable to add a flocculant to the wastewater when removing the sediment by the inclined plate settling tank or the second inclined plate settling tank. In addition, the sludge plate type sedimentation tank-The sediment removed in the second slant plate sedimentation tank and the suspended solids removed by the membrane filtration device are separated into solid and liquid, and the solid can be used as a cement raw material.

An apparatus for treating fly ash washing wastewater according to the present invention is an apparatus for treating wastewater when fly ash is dissolved in water and desalted, and a pH adjusting apparatus for adjusting the pH of the wastewater, and a pH adjusting apparatus. It is equipped with an inclined plate sedimentation tank that removes sediment from the drained water, and a membrane filtration device that removes suspended solids from the wastewater from which the sediment has been removed.

A chemical reaction tank for adding the finishing agent to the wastewater from which sediment was removed by the inclined plate sedimentation tank, and a second inclined plate sedimentation tank for removing the sediment from the wastewater to which the finishing agent was added May be further provided. In this case, the membrane filtration device shall remove suspended matter from the wastewater from which sediment has been removed in the second swash plate type settling tank. Inclined plate sedimentation tank ゃ A solid-liquid separation device that separates the sediment removed by the second inclined plate sedimentation tank and the suspended matter removed by the membrane filtration device into solid and liquid and uses the solid as a cement raw material. It can also be provided.

[Brief description of drawings]

FIG. 1 is a block diagram schematically showing an apparatus for treating fly ash washing wastewater according to an embodiment of the present invention,

FIG. 2 is a cross-sectional view showing a gas absorption reaction / deaeration tank used in the embodiment, and FIG. 3 is a block diagram schematically showing a conventional apparatus for treating fly ash washing wastewater.

[Best Mode for Carrying Out the Invention]

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows the configuration of a fly ash washing wastewater treatment apparatus according to an embodiment of the present invention. Gas absorption reaction and degassing tank 21 are connected to filtrate tank 1 that contains filtrate when incinerated fly ash is washed and desalinated, and gas absorption reaction is performed. 22, a chemical reaction tank 23 and a second inclined plate settling tank 24 are sequentially connected. Further, a membrane filtration device 25 is connected to the second inclined plate settling tank 24, and a treated water tank 13 is connected to the membrane filtration device 25. In addition, the first inclined plate settling tank 22 and the second inclined plate settling tank 2 A filter press 15 is connected to 4 and the membrane filtration device 25 via a slurry pipe 14, and a filtration water tank 16 is connected to the filter press 15.

First, the filtrate contained in the filtrate tank 1 is sent to a gas absorption reaction / removal unit 21, where the pH is adjusted by a reaction with carbon dioxide gas.

Gas absorption reaction • The internal structure of the degassing tank 21 is shown in FIG. Gas absorption reactionDegassing tank 21 is roughly divided into reaction tank 31 for reacting filtrate L1 and carbon dioxide gas G in countercurrent, and degassing for dewatering wastewater L2 discharged from reaction tank 31. A tank 32 is provided. Filtration liquid L 1 from the filtrate tank 1 is supplied to the reaction tank 31 through a water supply pipe 33 and the liquid distributor plate ^{_{^{34, Ca 2+, S 0 4 2}}} -, contains metal ions Mg ²⁺ and the like. On the other hand, a large amount of carbon dioxide G is blown into the reaction tank 31 from a cement firing kiln (not shown) via the blow control device 35. The carbon dioxide gas G is blown from the air supply pipe 36 at the lower part of the reaction tank 31 through the diffuser plate 37 to the air bubbles having a fine bubble diameter of 0.5 to 3 mm. through contact with the filtrate L 1 and countercurrent, Ca ²⁺ in the filtrate _{^{L 1, S 0 4 2 -}} , and with ions of Mg ²⁺ or the like is neutralized _{_{Ca C0 3, CaS0 4, MgC0}} 3 or the like Become.

After the reaction in the reaction tank 31 is completed, the carbon dioxide gas G is exhausted to the atmosphere via the exhaust pipe 39. On the other hand, the wastewater L2, which has completed the reaction with the carbon dioxide gas G, is introduced into the degassing tank 32 to be degassed, and the metal carbonate generated by insolubilization is added by the coagulation added from an adding device (not shown). Aggregated by agent C. The wastewater L2 in the degassing tank 32 is stirred by the stirrer 40 to promote the reaction. Further, the pH value of the wastewater L2 in the degassing tank 32 is monitored by the pH meter 41, and the blowing control device 35 supplies the reaction tank 31 based on the output of the pH meter 41 so that the pH value is maintained constant. The supply amount of carbon dioxide G is controlled.

The drainage L 2 thus adjusted in pH is supplied to the first inclined plate settling tank 22 through the drain outlet 42 to remove the sediment. The sediment T generated in the removal of f32 is withdrawn through a sludge discharge port 43 by a pump or the like. The first inclined plate type settling tank 22 has a plurality of inclined plates arranged in parallel with each other, drains water upward between these inclined plates, and removes insoluble substances contained in the drainage from each inclined plate. Efficient sedimentation with very small footprint due to sedimentation on the surface Separation can be performed. The insoluble material precipitated on the surface of each inclined plate slides down the surface of the inclined plate, accumulates in the sludge hopper at the lower end, and is concentrated. On the other hand, the wastewater from which the insoluble matter has been separated enters the outflow trough located above the inclined plate, and is sent to the chemical reaction tank 23.

In the chemical reaction tank 23, a finishing agent such as chelate / ferrous chloride is added to the wastewater sent from the first inclined plate settling tank 22. Further, the wastewater is supplied to a second inclined plate settling tank 24, and after the coagulant is added again, the sediment is removed. In addition, as the first inclined plate type settling tank 22 and the second inclined plate type settling tank 24, for example, Incaramelesepare made by Nippon Inka Co., Ltd. can be used. Thereafter, the wastewater is sent to a membrane filtration device 25, where suspended substances are removed. The membrane filtration device 25 separates suspended substances contained in the influent water with high efficiency using a microfiltration device. The microfiltration device includes a drum-shaped filtration device and a disk-shaped filtration device. The drum filter is composed of a plurality of filter elements mounted around the drum rotating at a low speed, and the inflow water supplied into the drum is filtered through each filter element. On the other hand, the disk-shaped filter is mounted on a plurality of hollow disks arranged in parallel at an interval on the outer periphery of the center drum. Each disc is divided into a number of segments, and each segment has a filter element on both sides. The influent supplied into the center drum enters the segments of each disc and is filtered through filter elements on both sides of the segments.

In both the drum-type and disk-type fills, when the head loss of the fill-up increases and the level of the inflow water rises, the cleaning device is activated and the fill-up is washed with the wash water.

Such a membrane filtration device 25 is capable of filtering by the natural flow of inflow water, has a very long filter life, can be easily replaced with a filter element having a different opening diameter, and is easy to maintain. For example, it is possible to use an Inka micro filter manufactured by Nippon Inka Co., Ltd.

The wastewater from which suspended solids are separated by the membrane filtration device 25 is stored in the treated water tank 13 and released. Swept away. The sediment removed in the first inclined plate sedimentation tank 22 and the second inclined plate sedimentation tank 24 and the suspended matter separated in the membrane filtration device 25 are stored in the sludge pit 14 Then, solid-liquid separation is performed by a filtration press 15, and water is returned from the filtration water tank 16 to the first inclined plate settling tank 22, and the solid content is used as a part of the cement raw material.

It should be noted that other types of solid-liquid separators such as a belt filter and a centrifugal separator can be used instead of the filter press 15.

Further, in the above embodiment, the coagulant C was added to the wastewater L 2 in the degassing tank 32 of the gas absorption reaction and degassing tank 21, but the present invention is not limited to this. Then, only the deaeration of the wastewater 2 may be performed, and the coagulant C may be added immediately before the wastewater 2 is supplied to the first inclined plate settling tank 22.

As described above, according to the present invention, after adjusting the pH of the wastewater, sediment is removed from the pH-adjusted wastewater by an inclined plate settling tank, and membrane filtration is performed from the wastewater from which the precipitate has been removed. Since the suspended solids are removed by the device, it is possible to treat the fly ash washing wastewater with a simple device configuration, thereby reducing equipment costs and facilitating maintenance.

Claims

The scope of the claims

1. A method of treating wastewater when fly ash is dissolved and desalted in water,

After adjusting the drainage pH,

The sediment is removed from the pH-adjusted wastewater by an inclined plate settling tank,

Remove suspended solids from wastewater from which sediment has been removed using a membrane filtration device

A method for treating fly ash washing wastewater, comprising:

2. Add the finishing agent to the wastewater from which sediment has been removed in the inclined plate sedimentation tank, remove the sediment from the wastewater to which the finishing agent has been added by the second inclined plate sedimentation tank, and use the second inclined plate sedimentation Remove suspended solids from the wastewater from which sediments have been removed in the tank using a membrane filtration device

2. The method for treating fly ash washing wastewater according to claim 1.

3. The method for treating fly ash washing wastewater according to claim 1, wherein the sediment is removed by adding a flocculant to the wastewater and using an inclined plate settling tank.

4. The method for treating fly ash washing wastewater according to claim 2, wherein the sediment is removed by adding a flocculant to the wastewater using a second inclined plate settling tank.

5. The method for treating fly ash washing wastewater according to claim 1, wherein the sediment removed in the inclined plate sedimentation tank and the suspended matter removed in the membrane filtration device are separated into solid and liquid, and the solid is used as a cement raw material.

6. The solid according to claim 2, wherein the sediment removed in the inclined plate sedimentation tank and the second inclined plate sedimentation tank and the suspended matter removed in the membrane filtration device are solid-liquid separated and the solid is used as a cement raw material. Fly ash washing wastewater treatment method.

7. A device for treating wastewater when fly ash is dissolved and desalted in water,

PH adjuster for drainage pH adjuster,

an inclined plate settling tank for removing sediment from the pH-adjusted wastewater,

A membrane filtration device to remove suspended solids from wastewater from which sediments have been removed

An apparatus for treating fly ash washing wastewater, comprising:

8. Add a finishing agent to the wastewater from which sediments have been removed in the inclined plate settling tank. A chemical reaction tank,

A second inclined plate settling tank for removing sediment from the wastewater to which the finishing agent has been added, wherein the membrane filtration device floats from the wastewater from which the sediment has been removed in the second inclined plate sedimentation tank. 8. The apparatus for treating fly ash washing wastewater according to claim 7, which removes substances.

9. A solid-liquid separator further comprising a solid-liquid separator for separating the sediment removed by the inclined plate settling tank and the suspended solids removed by the membrane filtration device and using the solid as a cement raw material. 7. The apparatus for treating fly ash washing wastewater according to 7.

10. Solid-liquid separation of the sediment removed in the inclined plate sedimentation tank and the second inclined plate sedimentation tank and the suspended matter removed in the membrane filtration device, and using the solid as a cement raw material 9. The apparatus for treating fly ash washing wastewater according to claim 8, further comprising a separation device.