JP5709199B2 - Method and apparatus for treating incinerated fly ash and cement kiln combustion gas bleed dust - Google Patents

Description

  The present invention relates to a method and apparatus for treating incineration fly ash generated when municipal waste or the like is incinerated, or wastewater generated when water is washed with chlorine bypass dust or the like.

  Incineration ash generated when municipal waste is incinerated has recently been recycled as a raw material for cement in view of the danger of depleting the final disposal site. Of municipal incineration ash, fly ash that is carried with gas and collected by the dust collector contains 10 to 20% chlorine, so it is necessary to remove the chlorine before recycling as cement raw material. . Thus, water-washing desalination equipment such as a belt filter is used to wash away water-soluble chlorine compounds contained in incineration fly ash (hereinafter referred to as “fly ash”), and then use them as raw materials for cement.

  On the other hand, a chlorine bypass system that removes chlorine that causes problems such as blocking of a preheater in a cement manufacturing facility has been used. In recent years, the recycling of waste as cement raw material or fuel has been promoted, and as the amount of waste processed increases, the amount of chlorine and other volatile components brought into the cement kiln also increases, and the amount of chlorine bypass dust generated also increases. It has increased. Therefore, development of an effective utilization method of chlorine bypass dust has been demanded.

  From this point of view, in the cement raw material treatment method described in Patent Document 1, water is added to waste containing chlorine to elute and filter out chlorine in the waste, and the obtained desalted cake is used as a cement raw material. In addition to using it, the wastewater is purified and discharged as it is, or the salinity is recovered, so that the chlorine bypass dust is effectively used without causing environmental pollution.

  In the above cement raw material treatment method, as shown in FIG. 2, the object to be treated (fly ash or chlorine bypass dust) and water are stirred and mixed in a stirring tank to dissolve chlorine, and after solid-liquid separation in a filtration facility The desalted cake is used as a raw material for cement. On the other hand, since the separated filtrate contains heavy metals, it is detoxified by pH adjustment or chemical addition in a hazardous substance removal facility and then discharged as waste water.

Japanese Patent Laid-Open No. 11-100343

  However, since fly ash and chlorine bypass dust contain a lot of calcium, calcium dissolves in the process of stirring and mixing fly ash, chlorine bypass dust and water, and calcium scale deposits on the equipment and piping, and filtration equipment Various problems such as clogging occur. Therefore, it is necessary to periodically replace and clean the parts, which leads to an increase in operating cost due to a decrease in operating rate. Also, in the drainage process after solid-liquid separation, it is deposited as a scale in pipes, reaction tanks, storage tanks, etc., so it is necessary to periodically replace and clean parts, and various chemicals are used to prevent this. Necessary. On the other hand, in the process of processing and recovering heavy metals by adjusting pH or adding chemicals, there is a problem that it is necessary to install a thickener having a small influence of calcium scale, a sedimentation tank requiring a large space, or the like.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and provides a treatment method for fly ash and the like that can be easily managed and maintained, and can reduce the installation area of the apparatus. The purpose is to do.

In order to achieve the above object, the present invention is a method for treating incineration fly ash and cement kiln combustion gas extraction dust, which is generated when incineration waste and incinerated fly ash collected by a dust collector or / and wastewater generated dust contained in the combustion gases bled from the kiln exhaust gas passage leading to the bottom cyclone when washed with water from the kiln of the cement kiln is introduced into the amphoteric ion-exchange resin, the amphoteric ion-exchange resin , Removing calcium from the waste water, and performing waste water treatment for further removing heavy metals and organic components on the waste water after calcium removal.

According to the present invention, before the waste water treatment is performed, the amphoteric ion exchange resin can remove calcium contained in the waste water generated when the incinerated fly ash and / or dust is washed with water. It is possible to prevent the calcium scale from being deposited on equipment and piping. As a result, various problems such as clogging of the belt filter can be avoided, maintenance and operation costs can be reduced, and a settling tank that requires a large space is not required. The area can also be kept small.

In the method for treating incinerated fly ash and cement kiln combustion gas extraction dust, after contacting the incinerated fly ash or / and the slurry in which the dust is dissolved with SO ₂ gas or / and CO ₂ gas, solid-liquid separation is performed. The filtrate obtained can be introduced into the amphoteric ion exchange resin. By changing the calcium content in the slurry to gypsum or / and calcium carbonate with SO ₂ gas or / and CO ₂ gas and reducing the amount of dissolved calcium, calcium can be removed more efficiently and amphoteric Precipitation of calcium scale in equipment before introduction into the ion exchange resin can be reduced.

Furthermore, the solid content can be obtained after adjusting the pH of the slurry containing the incinerated fly ash after contact with the SO ₂ gas or / and CO ₂ gas and / or cement kiln combustion gas extraction dust, At this time, the pH of the slurry can be adjusted to 7.0 or more and 10.5 or less. Thereby, the heavy metal melt | dissolved by pH adjustment can be unevenly distributed to the solid content side, and the process cost of the chemical | medical agent required for waste water treatment can be reduced.

In the method for treating incinerated fly ash and cement kiln combustion gas bleed dust, in order to bring SO ₂ gas and / or CO ₂ gas into contact with the slurry, when the slurry is obtained by dissolving the incinerated fly ash, When the slurry is contacted with the exhaust gas of an external cement kiln or / and the exhaust gas of a chlorine bypass system for removing chlorine from the combustion gas attached to the cement kiln, and when the slurry is a solution in which the dust is dissolved, The slurry can be contacted with the exhaust gas of the cement kiln or / and the exhaust gas of a chlorine bypass system for removing chlorine from the combustion gas attached to the cement kiln, and the operating cost and equipment cost can be kept lower. it can.

In the incineration fly ash and cement kiln combustion gas extraction dust treatment method, the waste water after the removal of calcium can be treated with a membrane to remove the heavy metals and organic components, and the operation cost can be further reduced while keeping the drug cost low. Can be reduced.

The present invention also relates to a device for treating incinerated fly ash and cement kiln combustion gas extraction dust, which is generated when incinerated waste and is recovered by a dust collector and / or a kiln for cement kiln. and bi ion exchange resin to remove calcium from waste water generated during washing with water the dust contained in the combustion gases bled from the kiln exhaust gas passage leading to the bottom cyclone Ass, calcium by the amphoteric ion-exchange resin A wastewater treatment apparatus that performs wastewater treatment to remove heavy metals and organic components from the wastewater after removal is provided. According to the present invention, as in the case of the above-described invention, it is possible to avoid various problems caused by the calcium scale, to reduce maintenance / operation costs, and to reduce the installation area of the apparatus.

  As described above, according to the present invention, it is possible to provide a processing method for fly ash and the like that can be easily managed and maintained, and that can reduce the installation area of the apparatus.

It is a flowchart which shows one Embodiment of the processing apparatus of the fly ash and cement kiln combustion gas extraction dust concerning this invention. It is a flowchart which shows an example of the conventional water washing processing system of fly ash and chlorine bypass dust.

  Next, an embodiment for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an embodiment of a processing apparatus for fly ash and cement kiln combustion gas bleed dust according to the present invention. In this processing apparatus 1, from the bottom of a cement kiln such as fly ash or chlorine bypass dust. Dust contained in the combustion gas extracted from the kiln exhaust gas flow path up to the lower cyclone (cement kiln combustion gas extraction dust) can be processed separately, or these can be processed simultaneously, but in the following explanation The case where only fly ash is processed is illustrated.

  This processing apparatus 1 removes heavy metals in the water-washing process 2 for washing the fly ash F with water, the dissolved calcium removal process 3 for removing calcium dissolved in the water-washed filtrate of the fly ash F, and the filtrate after the calcium removal. It consists of a heavy metal removal step 4 and an organic component removal step 5 that removes organic components after heavy metal removal and before discharge.

In the water washing step 2, the fly ash F stored in the storage tank 21 is dissolved in water for desalting, and the SO ₂ gas and / or CO ₂ gas is further introduced into the dissolution reaction tank 22 and discharged from the dissolution reaction tank 22. A storage pit 23 for storing the slurry, a filter press 24 for solid-liquid separation of the slurry S1 discharged from the storage pit 23 into cake C and filtrate L1, and a filtrate L1 discharged from the filter press 24. It is comprised with the storage tank 25 to store.

SO ₂ gas and / or CO ₂ gas is introduced into the dissolution reaction tank 22, thereby changing the calcium content in the slurry to gypsum (CaSO ₄ ) and / or calcium carbonate (CaCO ₃ ), and the amount of dissolved calcium Reduce. As the gas introduced into the dissolution reaction tank 22, for example, exhaust gas from a cement kiln containing CO ₂ or exhaust gas from a chlorine bypass system attached to a cement kiln containing SO ₂ gas is used.

  The storage pit 23 is provided for storing the slurry from the dissolution reaction tank 22, and the pH may be adjusted by a pH adjuster in the storage pit 23.

  The dissolved calcium removal step 3 is a storage tank that temporarily stores the ion exchange resin 31 that removes calcium dissolved in the filtrate L1 supplied from the storage tank 25 and the decalcified waste water L2 from which calcium has been removed by the ion exchange resin 31. 32 and a storage tank 33 for temporarily storing demineralized calcium-containing water L3 discharged from the ion exchange resin 31.

  The ion exchange resin 31 is provided to remove calcium dissolved in the filtrate L1 supplied from the storage tank 25, and an amphoteric ion exchange resin or the like can be used. An amphoteric ion exchange resin is a resin having a function of ion-exchange with both cationic anions by using a crosslinked base material such as crosslinked polystyrene and having a quaternary ammonium group and a carboxylic acid group in the same functional group chain. is there. For example, amphoteric ion exchange resin, Diaion (registered trademark), AMP03 manufactured by Mitsubishi Chemical Corporation can be used. The ion exchange resin 31 can separate the electrolyte and the non-electrolyte in the aqueous solution, and can also perform the mutual separation of the electrolyte.

  The heavy metal removal step 4 is provided to remove heavy metals contained in the decalcified waste water L2 supplied from the storage tank 32, and stores the chemical tank 45, the decalcified waste water L2, and the chemical for storing a chelating agent, a sulfurizing agent, and the like. And a heavy metal reaction tank 40, a filter 41 for collecting a solid content in which heavy metal is adsorbed, a heavy metal sulfide, and the like, and a storage tank 42 for storing the filtrate L5 discharged from the filter 41.

  The heavy metal reaction tank 40 is provided to remove residual heavy metals contained in the decalcified waste water L2 from the storage tank 32 from the waste water using a chemical such as a chelating agent or a sulfurizing agent supplied from the chemical tank 45. .

  The filter 41 has a microfiltration membrane and is provided for filtering the treated water L4 from the heavy metal reaction tank 40 to remove residual heavy metals and suspended substances. The filtrate L5 discharged from the filter 41 is stored in the storage tank 42. By circulating this filtrate L5 between the filter 41 and the storage tank 42 and backwashing, heavy metals and the like can be efficiently removed. . On the other hand, although the decalcification waste water L2 is supplied to the filter 41 as the treated water L4 via the heavy metal reaction tank 40, the decalcification waste water L2 may be supplied directly to the filter 41.

  The organic component removal step 5 is provided to remove residual heavy metals and the like with the filter 41 and remove organic components contained in the filtrate L6 stored in the storage tank 42.

  The filter 43 has a finer filtration membrane than the filter 41, and has an ultrafiltration membrane, a reverse osmosis membrane, etc., and removes organic components contained in the filtrate L6 from the storage tank 42, or COD The filtrate L7 discharged from the filter 43 is stored in the storage tank 44. As in the case of the filter 41, the filtrate L7 is circulated and washed between the filter 43 and the storage tank 44. Thus, organic components and the like can be efficiently removed. On the other hand, the filtrate L6 is supplied to the filter 43, but the decalcified waste water L2 from the storage tank 32 may be supplied to the filter 43 after being processed in the sand filter and the chelate tower.

  Next, the operation of the processing system 1 having the above configuration will be described with reference to FIG.

First, in the water washing step 2, the fly ash F stored in the storage tank 21 is supplied to the dissolution reaction tank 22, and water is added to the fly ash F to make a slurry. Further, CO ₂ gas or / and SO ₂ gas is introduced into the dissolution reaction tank 22 to change the calcium content in the slurry to CaCO ₃ or / and CaSO ₄ , and at the same time, the slurry is made by the CO ₂ gas and SO ₂ gas. The pH is adjusted to 7.0 to 10.5 to precipitate heavy metals in the slurry. The fly ash slurry from the dissolution reaction tank 22 is temporarily stored in the storage pit 23. If the pH is out of the range, the acid (H ₂ SO ₄ , H ₂ SO ₃ , HCl, etc.) is stored in the storage pit 23. ) And an alkali (NaOH, Ca (OH) _2, etc.) pH adjuster to adjust the pH to 7.0 to 10.5 to precipitate heavy metals in the slurry.

  The filter press 24 separates the slurry S1 from the storage pit 23 into filtrate L1 and cake C while washing with fresh water. The cake C after washing is used as a cement raw material in the cement kiln, and the cake washing water is returned to the dissolution reaction tank 22. Here, since the heavy metal precipitated by the pH adjustment is unevenly distributed on the cake C side, a part of the heavy metal contained in the fly ash F is removed. Further, the filtrate L1 discharged from the filter press 24 is temporarily stored in the storage tank 25.

  Next, in the dissolved calcium removal step 3, the filtrate L1 from the storage tank 25 is supplied to the ion exchange resin 31, and the calcium dissolved in the filtrate L1 is removed. When the filtrate L1 is introduced into the ion exchange resin 31, the decalcified waste water L2 from which the calcium content has been removed and the desalted calcium-containing water L3 from which the salt has been removed and contain the calcium content are discharged over time. The decalcified waste water L2 discharged from the ion exchange resin 31 is temporarily stored in the storage tank 32, and the desalted calcium-containing water L3 is stored in the storage tank 33 and then discharged.

  By supplying the decalcified waste water L2 to the heavy metal reaction tank 40 and bringing it into contact with a chemical that adsorbs and solidifies heavy metals such as a chelating agent, a sulfiding agent, a pH adjuster, etc. supplied from the chemical tank 45, The contained heavy metals can be recovered. This treated water L4 is supplied to the filter 41 and separated into a solid content concentrated water containing heavy metals and a filtrate L5. In addition, the filtrate L5 that has passed through the filter 41 is circulated between the storage tank 42 and the filter 41, and the filtrate L5 is subjected to backwashing of the filter 41, whereby the concentrated water concentrated by heavy metals is efficiently recovered. The collected concentrated water can be treated with, for example, a cement kiln, and the filtrate L5 discharged from the filter 41 is stored in the storage tank 42.

  The filtrate L6 from which heavy metals have been removed is supplied to the filter 43 in the organic component removal step 5, and the filtrate L7 that has passed through the filter 43 is circulated between the storage tank 44 and the filter 43 in the same manner as the filter 41. By using the liquid L7 for back washing of the filter 43, the concentrated water in which the organic component is concentrated is efficiently recovered, and the recovered organic component concentrated water is treated with a cement kiln or the like. On the other hand, the filtrate L8 after the organic component concentrated water recovery is discharged as it is or after salt recovery.

  In the above embodiment, the decalcification waste water L2 is supplied to the heavy metal reaction tank 40 for processing. However, the decalcification waste water L2 may be supplied directly to the filter 41, for example, the storage tank 40 is not provided. It is also possible to add the chemical into the pipe, supply the liquid to the filter 41, and supply the liquid from which heavy metals and suspended substances have been removed by the filter 41 to the organic component removing step 5.

  Moreover, in the said embodiment, although the decalcification waste_water | drain L2 is supplied to the heavy metal reaction tank 40 and processed, the liquid which removed the heavy metal and the suspended solids with the sand filter, the chelate tower, etc. is an organic component removal process. 5 can also be supplied.

  In the above-described embodiment, the heavy metal is concentrated and collected using the filter 41 in the heavy metal removal step 4, but a filter press, a lamella separator, or the like can be used instead of the filter 41.

In the above fly ash treatment, the cake C washed with the filter press 24 is used as a cement raw material. However, the cake after washing the cement kiln combustion gas extraction dust with water has a calcium component of CaCO ₃ or / and Since it is changed to CaSO ₄ , the content of Ca (OH) ₂ is reduced, the influence on the setting time is reduced, and it can be added directly to the cement finishing process while maintaining the stability of the cement quality. In addition, this makes it possible to suppress the circulation and concentration of heavy metals in the cement manufacturing process, and to reduce chemical costs compared to conventional wastewater treatment.

DESCRIPTION OF SYMBOLS 1 Processing apparatus of fly ash and cement kiln combustion gas extraction dust 2 Water washing process 3 Dissolved calcium removal process 4 Heavy metal removal process 5 Organic component removal process 21 Storage tank 22 Dissolution reaction tank 23 Storage pit 24 Filter press 25 Storage tank 31 Ion exchange resin 32 33 Storage tank 40 Heavy metal reaction tank 41 Filter 42 Storage tank 43 Filter 44 Storage tank 45 Drug tank

Claims (6)

Incinerated fly ash generated by incineration of waste, and / or dust contained in combustion gas extracted from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the bottom cyclone The waste water generated when washing with water is introduced into the amphoteric ion exchange resin,
Calcium was removed from the waste water by the amphoteric ion-exchange resin,
A method for treating incinerated fly ash and cement kiln combustion gas bleed dust, wherein waste water after removing calcium is further subjected to waste water treatment for removing heavy metals and organic components . The SO ₂ gas or / and CO ₂ gas is brought into contact with the incinerated fly ash or / and the dust-dissolved slurry, followed by solid-liquid separation, and the obtained filtrate is introduced into the amphoteric ion exchange resin. A method for treating incinerated fly ash and cement kiln combustion gas bleed dust according to claim 1. After adjusting the pH of the slurry containing the incinerated fly ash after contact with the SO ₂ gas or / and CO ₂ gas to 7.0 or more and 10.5 or less, solid-liquid separation is performed to obtain The method for treating incinerated fly ash and cement kiln combustion gas extraction dust according to claim 2, wherein the filtrate obtained is introduced into the amphoteric ion exchange resin. In order to bring SO ₂ gas and / or CO ₂ gas into contact with the slurry,
When the slurry is the one in which the incineration fly ash is dissolved, the exhaust gas from the external cement kiln and / or the chlorine bypass system exhaust gas for removing chlorine from the combustion gas attached to the cement kiln is added to the slurry. Contact,
When the slurry is one in which the dust is dissolved, the slurry is brought into contact with the exhaust gas of the cement kiln or / and the exhaust gas of a chlorine bypass system for removing chlorine from the combustion gas attached to the cement kiln. The processing method of incineration fly ash and cement kiln combustion gas extraction dust of Claim 2 or 3 characterized by these. The method for treating incinerated fly ash and cement kiln combustion gas bleed dust according to any one of claims 1 to 4, wherein the heavy metal and organic components are removed by membrane treatment of the waste water after the removal of calcium. Incinerated fly ash generated by incineration of waste, and / or dust contained in combustion gas extracted from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the bottom cyclone An amphoteric ion exchange resin that removes calcium from wastewater generated when washing
Processing incineration fly ash and cement kiln combustion gas extracted dust, characterized in that it comprises a waste water treatment apparatus for performing a waste water treatment to remove heavy metals and organic components with respect to waste water after removal of the calcium by the amphoteric ion-exchange resin apparatus.

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