JP2013151414A - Apparatus and method for treating cement kiln dust - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently recover minor components such as lead from dust included in cement kiln combustion gas at low cost.SOLUTION: An apparatus 1 for treating cement kiln dust is equipped with: a classifier 8 classifying dust included in combustion gas exhausted from a cement kiln 2; a flotator 16 recovering an object to be recovered by flotation method from fine powder classified by the classifier 8. Lead or the like exists dominantly in the fine powder side classified by the classifier 8 among the dust included in combustion gas exhausted from the cement kiln 2, and only the fine powder is made the object to be treated by the flotator 16, so that the amount of the object itself to be treated decreases. Thus the amount of calcium content being the object to be removed decreases; and the additive amount of chemicals such as sulfuric acid for removing the calcium content can be greatly reduced, whereby the treatment cost can be suppressed low. The dust may be one from chlorine bypass equipment or alkali bypass equipment. As the classifier 8, a centrifugal type ultra-fine powder air classifier can be used.

Description

  The present invention relates to a cement kiln dust processing apparatus and processing method, and more particularly to an apparatus and method for recovering trace components such as lead from dust contained in combustion exhaust gas of a cement kiln.

  In recent years, recycling of incineration ash and other wastes into cement raw materials or fuels has been promoted, and as the amount of waste processed increases, the amount of heavy metals such as lead brought into the cement kiln also increases. Since an increase in heavy metals is predicted to be a problem, countermeasures are required.

  Therefore, for example, in Patent Document 1, a fine powder containing a calcium component and a lead component, water, and sulfuric acid are mixed to adjust the liquidity to pH 4 or less, and calcium sulfate and lead sulfate, which are solid components, are added. A sulfate generation step of preparing a slurry containing, a pH adjustment step of adjusting the liquidity to pH 5 or more by adding an alkali agent to the slurry, and adding a collector (sodium n-dodecyl sulfate) to the slurry; Proposal of a treatment method for calcium powder and fine powder containing lead component, including floatation with calcium sulfate as the main component and lead / calcium separation process to obtain sedimentation with lead sulfate as the main component. Has been.

JP 2006-299394 A

  However, when the lead recovered by the conventional lead recovery method or the like as described in Patent Document 1 is reduced to the hillside, it is necessary to increase the lead concentration of the recovered material. For this purpose, treatment such as removing calcium from the recovered material is necessary, and there is a problem that the treatment cost increases, such as adding a large amount of chemicals such as sulfuric acid.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and is an apparatus that can efficiently recover trace components such as lead from dust contained in cement kiln combustion gas at low cost. And to provide a method.

  In order to achieve the above object, the present invention is a cement kiln dust treatment apparatus, which is included in a probe that bleeds while cooling a part of the combustion gas discharged from the cement kiln and the combustion gas extracted by the probe. A first classifier that separates coarse dust dust, a dust collector that collects extracted gas containing fine powder discharged from the first classifier, and dust discharged from the dust collector into fine powder and coarse powder A second classifier to be separated, a coarse powder tank for temporarily storing the coarse powder classified by the second classifier to be transported to the cement grinding process, and the second classifier It comprises a flotation machine that collects a collection object from fine powder by a flotation method.

  According to the present invention, among the dust contained in the combustion gas discharged from the cement kiln, trace components such as lead are unevenly distributed on the fine powder side classified by the second classifier, and only this fine powder is floated. Since the amount of the processing object can be reduced by selecting the processing object by the selection machine, the amount of calcium to be removed is also reduced, and the amount of chemicals such as sulfuric acid for removing the calcium is greatly increased. The processing cost can be kept low.

  In the cement kiln dust treatment apparatus, the dust can be dust from a chlorine bypass facility or an alkali bypass facility, and lead and the like can be simultaneously removed while removing chlorine or alkali.

  In the cement kiln dust treatment apparatus, the second classifier can be a centrifugal ultrafine powder air classifier. This classifier is preferable because it has characteristics such as easy adjustment of the classification point, simple structure, and high maintainability.

  The present invention also relates to a cement kiln dust treatment method, wherein a part of the combustion gas discharged from the cement kiln is extracted while cooling, and coarse dust particles contained in the extracted part of the combustion gas are separated. , Collecting the fine powder-containing extraction gas after separating the coarse powder, separating the dust obtained by collecting the dust into fine powder and coarse powder, and collecting the dust obtained by collecting the fine powder-containing extraction gas The coarse powder obtained when separated into fine powder and coarse powder is temporarily stored for transport to the cement crushing process, and the dust obtained by collecting the fine gas-containing extraction gas is classified into fine powder and coarse powder. From the fine powder obtained upon separation, the collection object is collected by the flotation method.

  According to the present invention, similar to the above-described invention, the amount of chemicals such as sulfuric acid for removing calcium can be greatly reduced, and trace components such as lead can be recovered while keeping processing costs low. Can do.

  In the cement kiln dust processing method, the desalted cake obtained by desalting the fine powder obtained when the dust obtained by collecting the fine gas-containing extraction gas is separated into fine powder and coarse powder is recycled. After dissolution, the collection object can be collected by the flotation method.

  In the cement kiln dust processing method, the fine powder obtained when the dust obtained by collecting the fine powder-containing extraction gas is separated into fine powder and coarse powder, is collected by a wet dust collector to form a slurry, From the slurry, the object to be recovered can be recovered by the flotation method.

  In the cement kiln dust processing method, the recovered lead is reduced to a mountain base, or the volume is reduced and finally disposed, and industrial salt is recovered from the salt water generated in the lead recovery step, or the salt water is drained. After treatment, it can be discharged into sewage or / and the ocean. Thereby, lead can be removed or recovered from cement kiln dust, and industrial salt can be recovered while removing water-soluble chlorine.

  As described above, according to the present invention, trace components such as lead can be efficiently recovered from dust contained in cement kiln combustion gas at low cost.

1 is a schematic view showing an embodiment of a cement kiln dust treatment apparatus according to the present invention.

  FIG. 1 shows an embodiment of a cement kiln dust treatment apparatus according to the present invention. The cement kiln dust treatment apparatus 1 is a kiln exhaust gas flow path from a kiln bottom of a cement kiln 2 to a lowermost cyclone (not shown). Further, a probe 3 for extracting a part of the combustion gas, a cyclone 5 as a classifier for separating coarse dust contained in the combustion gas extracted by the probe 3, and an extraction containing fine powder discharged from the cyclone 5 A cooler 6 for cooling the gas, a super fine powder classifier 8 as a second classifier for classifying the dust collected by the cooler 6 and the bag filter 7, and fine powder classified by the super fine powder classifier 8 The bag filter 10 for collecting dust, the dissolution tank 11 for dissolving the fine powder collected by the bag filter 10 in water and slurrying the slurry, and sulfidizing the slurry slurryed in the dissolution tank 11 A drug reaction vessel 12 to react with the addition of chemical etc., and the like flotation machine 16 for recovering lead and the like by flotation from the feed slurry from drug reaction vessel 12.

  Since each device from the probe 3 to the bag filter 7 in the cement kiln dust processing apparatus 1 is installed in a general chlorine bypass facility, detailed description thereof is omitted.

  The ultrafine powder classifier 8 is configured to further supply dust fine powder having an average particle size of about 9 μm or less supplied from the cyclone 5 through the cooler 6 and the bag filter 7, and fine powder having an average particle size of 0.5 μm to 5 μm (lead removal efficiency and In consideration of the handling properties of fine powder, etc., it is preferably provided for separation into a fine powder having an average particle diameter of 1 μm to 3 μm, for example, MP-250, MP-360, manufactured by Japan Pneumatic Industrial Co. A dry air classifier such as MP-460 can be used.

  The coarse powder tank 9 is installed to temporarily store the coarse powder separated by the ultra fine powder classifier 8, and is equipped with a shipping facility for transporting the coarse powder to the cement crushing process via a vehicle.

  The bag filter 10 is provided for collecting the fine powder separated by the ultra fine powder classifier 8. A wet scrubber may be used in place of the bag filter 10.

  The dissolution tank 11 is provided for dissolving the fine powder collected by the bag filter 10 in water to form a slurry. When a wet scrubber is used instead of the bag filter 10, the dissolution tank 11 is not necessary. .

  The chemical reaction tank 12 is provided to add and react each chemical solution supplied via the pumps 13, 14, and 15 to the slurry supplied from the dissolution tank 11, and has a plurality of stirring tanks.

  The flotation machine 16 is provided to separate the slurry supplied from the chemical reaction tank 12 into a lead recovered material as a floss, a chlorine-containing material as a sink, and the like. The foaming agent and air are supplied via

  The filter press 18 and the vertical solid-liquid separator 19 are each arranged for solid-liquid separation of the floss or sink from the flotation machine 16.

  Next, operation | movement of the cement kiln dust processing apparatus 1 which has the said structure is demonstrated, referring FIG.

  The extraction gas from the kiln exhaust gas flow path from the kiln bottom of the cement kiln 2 to the lowermost cyclone is cooled by the cold air from the cooling fan 4 in the probe 3 and then introduced into the cyclone 5 to obtain coarse powder and average It is separated into fine powder and gas having a particle size of about 9 μm or less. The separated coarse powder having a low chlorine content is returned to the cement kiln system.

  Fine powder and gas having a high chlorine content are collected by the bag filter 7 after being cooled by the cooler 6. The dust collected by the bag filter 7 and the dust discharged from the cooler 6 are classified by the ultrafine powder classifier 8, and fine powder having a high lead concentration with an average particle size of about 0.5 μm to 5 μm is collected by the bag filter 10. After being collected, it is slurried in the dissolution tank 11. The coarse powder having an average particle size of 5 μm or more can be temporarily stored in the coarse powder tank 9 and used in the cement grinding step.

  Next, the slurry in the dissolution tank 11 is supplied to the drug reaction tank 12. Further, a sulfurizing agent such as sodium hydrosulfide (NaSH) and sulfuric acid (HSO) are added to the chemical reaction tank 12 through pumps 13 and 14. The reason for adding sodium hydrosulfide and sulfuric acid is to sulfidize lead chloride and the like contained in the slurry to produce lead sulfide (PbS) and precipitate it. Here, the amount of fine powder classified by the ultra fine powder classifier 8 is significantly smaller than before, the amount of sulfuric acid added can be halved, and the amount of other chemicals can also be reduced.

  Further, a flotation agent is added to the drug reaction tank 12 through a pump 15. As the flotation agent, an organic compound heavy metal scavenger having a xanthate group (R—O—CaNa), a dicarbamic acid group (R—NH—CSNa), a thiol group (—SH), or the like can be used. .

  The slurry from the chemical reaction tank 12 is supplied to the flotation machine 16. The flotation machine 16 is supplied with a foaming agent via a pump 17. MIBC (Methyl Isobutyl Carbinol) etc. can be used for a foaming agent. The flotation machine 16 is further supplied with air, and the slurry is separated into a floss containing lead and a tail-side slurry containing gypsum by a flotation operation.

  The floss containing lead is supplied to the filter press 18 and separated into a cake containing lead sulfide and water. Here, the high-quality lead recovery product can be directly returned to the mountain, or may be finalized by reducing the volume. The separated water can be returned to the flotation machine 16 and reused in the flotation process. Furthermore, since excess foaming agent remains in the separated water, the amount of the drug can be reduced by circulating it.

  On the other hand, the tail-side slurry containing gypsum from the flotation machine 16 is solid-liquid separated in the vertical solid-liquid separator 19, and the separated salt water can be added to the cement grinding step. The separated salt water may be discharged into sewage or the ocean after water treatment, or the water obtained may be returned to the dissolution tank 11 after desalting in the salt recovery step.

  As described above, in the above-described embodiment, the chlorine content is removed by the chlorine bypass facility and classified by the ultrafine powder classifier 8, and the lead concentration is high. Since lead and the like are collected, the amount of chemicals such as sulfuric acid for removing calcium can be greatly reduced, and the processing cost can be kept low.

  In the above embodiment, the dust obtained by the chlorine bypass facility is used as the object to be treated. However, if the dust is discharged from the cement kiln, it is discharged from the preheater and collected by an electric dust collector, a bag filter, or the like. Dust and the like can be treated similarly. Moreover, the dust obtained by the alkali bypass facility can be used as a processing object. In this case, trace components such as lead can be efficiently removed while removing alkali from the combustion exhaust gas of the cement kiln.

DESCRIPTION OF SYMBOLS 1 Cement kiln dust processing apparatus 2 Cement kiln 3 Probe 4 Cooling fan 5 Cyclone 6 Cooler 7 Bag filter 8 Super fine powder classifier 9 Coarse powder tank 10 Bag filter 11 Dissolution tank 12 Chemical reaction tank 13 Pump 14 Pump 15 Pump 16 Flotation Machine 17 Pump 18 Filter press 19 Vertical solid-liquid separator

Claims (7)

A probe for extracting while cooling a part of the combustion gas discharged from the cement kiln;
A first classifier for separating coarse dust particles contained in the combustion gas extracted by the probe;
A dust collector that collects an extraction gas containing fine powder discharged from the first classifier;
A second classifier that separates dust discharged from the dust collector into fine powder and coarse powder;
A coarse powder tank for temporarily storing the coarse powder classified by the second classifier for transport to a cement grinding process;
A cement kiln dust treatment apparatus comprising: a flotation machine that collects an object to be collected from fine powder classified by the second classifier by a flotation method.   The cement kiln dust treatment apparatus according to claim 1, wherein the dust is dust from a chlorine bypass facility or an alkali bypass facility.   The cement kiln dust treatment apparatus according to claim 1 or 2, wherein the second classifier is a centrifugal ultrafine powder air classifier. Extracting while cooling a part of the combustion gas discharged from the cement kiln,
Separating dust coarse powder contained in a part of the extracted combustion gas,
Dust extraction gas containing fine powder after separating coarse powder,
The dust obtained by collecting the dust is separated into fine powder and coarse powder,
The coarse powder obtained when the dust obtained by collecting the fine powder-containing extraction gas is separated into fine powder and coarse powder is temporarily stored for transport to the cement grinding process,
Cement kiln dust treatment characterized in that a recovery object is recovered by a flotation method from fine powder obtained when dust obtained by collecting the extracted gas containing fine powder is separated into fine powder and coarse powder Method.   After re-dissolving the desalted cake obtained by desalting the fine powder obtained when the dust obtained by collecting the fine gas-containing extraction gas is separated into fine powder and coarse powder, the floating beneficiation method The method according to claim 4, wherein the object to be collected is collected by the method. The fine powder obtained when the dust obtained by collecting the fine powder-containing extraction gas is separated into fine powder and coarse powder is collected by a wet dust collector to form a slurry,
6. The cement kiln dust treatment method according to claim 4 or 5, wherein a recovery object is recovered from the slurry by a flotation method. The collected lead is reduced to the mountain or reduced in volume and finally disposed.
Cement kiln dust according to claim 4, 5 or 6, wherein industrial salt is recovered from the salt water generated in the lead recovery step or discharged into sewage or / and the ocean after draining the salt water. Processing method.

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