JP2012056777A - Treatment method and apparatus of micropowder containing fluorine, calcium, selenium and heavy metals - Google Patents

Abstract

A fine powder containing fluorine, calcium, selenium and heavy metals such as chlorine bypass dust is treated at low cost.
SOLUTION: A fine powder containing fluorine, calcium, selenium and heavy metals, water, and a sulfiding agent are mixed to produce a slurry, and the slurry is separated into solid and liquid to obtain a solid content and a liquid content. Then, the liquid component is drained and the solid content is slurried, followed by the flotation treatment, and the wastewater generated by the flotation treatment is used in a cement manufacturing facility. After slurrying the solid component, sulfuric acid and a scavenger can be added to perform the flotation process, and the pH is adjusted by adding alkali to the wastewater generated by the flotation process. A part of the waste water obtained by solid-liquid separation of the tail and solid-liquid separation of the obtained liquid and floss can be used in a cement production facility.
[Selection] Figure 1

Description

  The present invention relates to a method and apparatus for treating fine powders containing fluorine, calcium, selenium and heavy metals, such as chlorine bypass dust recovered by a chlorine bypass system attached to a cement production facility.

  Focusing on chlorine, sulfur, alkali, etc., which causes problems such as blockage of preheaters in cement manufacturing facilities, from the bottom of the kiln of the cement kiln to the bottom cyclone A chlorine bypass system for extracting a part of combustion gas and removing chlorine from the kiln exhaust gas flow path is used.

  In this chlorine bypass system, chlorine is unevenly distributed on the fine powder side of the dust generated by cooling the extracted combustion gas, so the dust is separated into coarse powder and fine powder by a classifier, and the coarse powder is converted into a cement kiln system. At the same time, the fine powder (chlorine bypass dust) containing the separated potassium chloride and the like was recovered.

  However, the extracted combustion gas contains lead, cadmium, selenium, and other heavy metals, fluorine, calcium, etc. in addition to chlorine. In any case of returning to the raw material system, it is necessary to treat appropriately.

  Therefore, Patent Document 1 discloses a flotation process after slurrying fine powder containing calcium and lead components, such as fine powder collected in the process of exhausting cement kiln exhaust gas by chlorine bypass technology, and adding chemicals. , A method of separating calcium components and lead components by a simple operation and recovering the lead components at a high rate is disclosed.

Japanese Patent No. 4083791

  According to the treatment method described in Patent Document 1, lead contained in chlorine bypass dust can be removed effectively, but a filtrate of chlorine bypass dust having a low fluorine concentration is produced, and at the time of flotation. A filtrate with a high fluorine concentration is produced. Conventionally, a mixed solution of these filtrates has been subjected to wastewater treatment. However, in particular, the treatment of fluorine and selenium has been expensive, which has been a factor in increasing operating costs.

  Therefore, the present invention has been made in view of the above problems in the prior art, and provides a method for treating fine powder containing fluorine, calcium, selenium and heavy metals such as chlorine bypass dust at a low cost. The purpose is to do.

  In order to achieve the above object, the present invention provides a method for treating fine powder containing fluorine, calcium, selenium and heavy metals, comprising fine powder containing fluorine, calcium, selenium and heavy metals, water, and sulfide. The slurry is mixed with the agent to produce a slurry, and the slurry is solid-liquid separated to obtain a solid content and a liquid content. The liquid content is drained, and the solid content is slurried, followed by a flotation process. The wastewater generated by the flotation process is used in a cement production facility.

  And according to the present invention, the wastewater generated by the flotation process is used in the cement manufacturing facility, and only the liquid after the solid-liquid separation by adding the sulfiding agent is drained, so fluorine, selenium and heavy metals The drug cost required for the treatment can be significantly reduced, and the increase in operating cost can be suppressed.

  In the above fine powder processing method, after slurrying the solid content, sulfuric acid and a scavenger can be added to perform the flotation treatment, performing flotation efficiently, gypsum by flotation processing, It is possible to separate and recover heavy metals such as lead. Moreover, the wastewater obtained by solid-liquid separation of the froth can be used instead of water for slurrying of the solid content obtained by solid-liquid separation of chlorine bypass dust attached to the cement production facility.

  Moreover, alkali is added to the tail generated in the flotation process, the pH is adjusted, the tail after the pH adjustment is subjected to solid-liquid separation, and the drainage obtained by solid-liquid separation of the obtained liquid and floss. Some can be used in cement production facilities. By adjusting the pH, heavy metals contained in the tail can be discharged out of the system.

  Furthermore, the fine powder containing fluorine, calcium, selenium and heavy metals can be made into dust contained in the gas extracted from the kiln exhaust gas passage from the kiln bottom of the cement kiln to the bottom cyclone, Chlorine bypass dust etc. can be processed at low cost.

  Further, the present invention is a processing apparatus for fine powder containing fluorine, calcium, selenium and heavy metals, wherein a fine powder containing fluorine, calcium, selenium and heavy metals, water and a sulfiding agent are mixed. Slurry generating means for generating a slurry, a solid-liquid separator for solid-liquid separation of the slurry generated by the slurry generating means, a wastewater treatment apparatus for wastewater treatment of the liquid discharged from the solid-liquid separator, It is characterized by comprising a flotation machine that performs a flotation process after slurrying the solid content discharged from the solid-liquid separator, and a cement production facility that uses the waste water of the flotation machine. According to the present invention, as in the case of the above-described invention, the chemical cost required for the treatment of fluorine, selenium, and heavy metals, and thus the operating cost can be greatly reduced.

  As described above, according to the present invention, it is possible to treat fine powder containing fluorine, calcium, selenium and heavy metals at low cost.

It is a flowchart which shows 1st Embodiment of the processing apparatus of the fine powder containing the fluorine, calcium, selenium, and heavy metals concerning this invention. It is a flowchart which shows 2nd Embodiment of the processing apparatus of the fine powder containing the fluorine, calcium, selenium, and heavy metals concerning this invention.

  Next, an embodiment for carrying out the present invention will be described in detail with reference to the drawings. In the following description, the method for treating fine powder according to the present invention is applied to the treatment of dust contained in the gas extracted from the kiln exhaust gas flow path from the bottom of the cement kiln to the bottom cyclone. The case will be described.

  FIG. 1 shows a cement kiln bleed dust processing apparatus (hereinafter abbreviated as “processing apparatus”) to which the first embodiment of the processing apparatus for fine powder according to the present invention is applied. Separately, the gas extraction unit 2, the gas processing unit 3, and the fine powder processing unit 4 are configured.

  The gas extraction unit 2 is equipment for extracting a part of the combustion gas from the kiln exhaust gas passage from the kiln bottom of the cement kiln 5 to the lowermost cyclone (not shown). The gas extraction unit 2 includes a probe 6 for extracting combustion gas, a cooling fan 7 for rapidly cooling the combustion gas extracted by supplying cold air into the probe 6, and dust contained in the extraction gas G1 discharged from the probe 6. It is comprised from the cyclone 10 etc. as a classifier which isolate | separates the coarse powder D1 in the inside.

  The gas processing unit 3 is a facility for collecting fine powder D2 and water-soluble components contained in the exhaust gas G2 discharged from the cyclone 10. The gas processing unit 3 includes a wet dust collector 11 that wet-collects fine powder D2 contained in the exhaust gas G2, an exhaust fan 12 that discharges the exhaust gas G3 of the wet dust collector 11 to the outside of the system, and the like.

The wet dust collector 11 collects the fine powder D2 in the exhaust gas G2 and removes chlorine from the exhaust gas G2, and the sulfur content (SO ₂ ) in the exhaust gas G2 and quick lime (CaO) contained in the fine powder D2 react with water. The resulting slaked lime (Ca (OH) ₂ ) is reacted to produce gypsum (CaSO ₄ .2H ₂ O). The wet dust collector 11 includes a scrubber 13, a circulating liquid tank 14, and a cleaning tower 15, and a pump 14 a for circulating the slurry is provided between the scrubber 13 and the circulating liquid tank 14.

  The fine powder processing unit 4 separates and recovers gypsum and sulfides of heavy metals such as lead from the solid content in the slurry S1 from the wet dust collector 11, and also performs drainage treatment and effective use of the generated liquid content. It is.

  The fine powder processing unit 4 adds a sulfurizing agent such as sodium hydrosulfide (NaSH) to the slurry S1, sulfides lead chloride, lead oxide, etc. in the slurry S1 to sulfides of heavy metals such as lead sulfide (hereinafter referred to as “sulfide”). And the first solid-liquid separator 21 for separating the slurry S2 after the addition of the sulfiding agent into a solid-liquid separation, and the first solid-liquid separator 21. A slurry tank 22 for adding water to the cake C1 produced to produce a slurry S3, an adjustment tank 23 for adjusting the pH value to 3 to 4 by adding a pH adjuster such as sulfuric acid to the slurry S3, and the pH adjusted An adjustment tank 24 for adding a hydrophobizing agent as a scavenger to the slurry S4, a flotation machine 25 that attaches sulfides in the slurry S5 to air bubbles, floats and separates them, and froth F from the flotation machine 25 Is separated into solid and liquid to produce cake C2, and sulfidation of heavy metals A second solid-liquid separator 26 that collects water, an adjustment tank 28 that adjusts the pH by adding alkali to the tail T from the flotation machine 25, and a third liquid-liquid separation of the slurry S6 from the adjustment tank 28. A solid-liquid separator 29 and a wastewater treatment device 30 for draining the filtrate W1 discharged from the first solid-liquid separator 21 are configured.

  Next, the operation of the processing apparatus 1 will be described with reference to FIG.

  From the kiln exhaust gas flow path from the kiln bottom of the cement kiln 5 to the lowermost cyclone, a part of the combustion gas is extracted by the probe 6 and at the same time, the extracted combustion gas is cooled by the cooling air from the cooling fan 7 and the melting point of the chlorine compound It is rapidly cooled to below 700 ° C. Next, the extracted gas G1 from the probe 6 is separated into coarse powder D1 and exhaust gas G2 containing fine powder D2 by the cyclone 10, and the coarse powder D1 is returned to the cement kiln system.

On the other hand, the exhaust gas G2 containing fine powder D2 is supplied to the scrubber 13 of the wet dust collector 11, and the slurry S1 is circulated between the scrubber 13 and the circulating liquid tank 14. In the slurry S1 produced by the wet dust collector 11, Ca (OH) ₂ produced by the reaction of CaO in the fine powder D2 with water is present, so the sulfur content (SO ₂ ) present in the exhaust gas G2 is slaked lime. And reacts as follows.
SO ₂ + Ca (OH) ₂ → CaSO ₃ .1 / 2H ₂ O + 1 / 2H ₂ O
CaSO ₃ · 1 / 2H ₂ O + 1 / 2O ₂ + 3 / 2H ₂ O → CaSO ₄ · 2H ₂ O
Thereby, the sulfur content in the exhaust gas G2 is rendered harmless and gypsum (CaSO ₄ .2H ₂ O) is generated.

  Next, in the adjustment tank 20, a sulfiding agent is added to the slurry S1 from the wet dust collector 11, and lead chloride, lead oxide, etc. in the slurry S1 are sulfided to produce sulfide. In addition, it is not necessary to perform the production | generation of sulfide by providing the adjustment tank 20 in the back | latter stage of the wet dust collector 11, and you may carry out by adding a sulfidizing agent to the scrubber 13 of the wet dust collector 11, or the circulating liquid tank 14.

  Next, the slurry S2 in which sulfide is generated is solid-liquid separated by the first solid-liquid separator 21, the filtrate W1 is separated from the slurry S2, drained by the wastewater treatment device 30, and discharged into sewage or the ocean. At the same time, the separated cake C 1 is supplied to the slurry tank 22. Since the filtrate W1 contains heavy metals remaining without precipitation due to the addition of low-concentration fluorine, selenium, and a sulfurizing agent, these are treated by the wastewater treatment device 30.

  Next, in the slurry tank 22, water is added to the cake C1 to generate a slurry S3. Furthermore, in the adjustment tank 23, sulfuric acid is added to the slurry S3 as a pH adjuster to adjust the pH value to 3 to 4, and in the adjustment tank 24, a hydrophobizing agent as a collecting agent is added.

  Next, the slurry S5 to which the hydrophobizing agent is added and air are supplied to the flotation machine 25, and in the flotation machine 25, bubbles are generated and sulfide is attached to the bubbles, and the sulfide is attached. The air bubbles that floated up, that is, Floss F, are collected. At this time, the gypsum contained in the slurry S5 is discharged from the flotation machine 25 as a tail T.

  Next, in the second solid-liquid separator 26, the floss F from the flotation machine 25 is subjected to solid-liquid separation, and a cake C2 is generated to recover heavy metal sulfides. The filtrate W2 generated at this time is supplied to the adjustment tank 20 and used to adjust the solid-liquid ratio of the slurry in the adjustment tank 20.

  At the same time, the tail T of the flotation machine 25 is supplied to the adjustment tank 28, and an alkaline agent is added to adjust the pH of the tail T to precipitate residual heavy metals such as cadmium. As the alkaline agent, slaked lime, sodium hydroxide, barium hydroxide and the like can be used. Furthermore, when using slaked lime as an alkaline agent, fluorine and sulfate radicals can be precipitated and removed from the liquid. In this case, troubles caused by circulation of fluorine and sulfate radicals can be avoided. In particular, for sulfate radicals, troubles of coaching growth in the cement manufacturing process and an increase in SOx concentration in the exhaust gas can be avoided.

  In the third solid-liquid separator 29, the precipitated heavy metals and gypsum S can be recovered on the cake C3 side. This gypsum S contains the above heavy metals, but there is no problem because it is extremely small. Further, the filtrate W5 is effectively used in a raw material dryer of a cement production facility. Even when the filtrate W5 having a relatively high fluorine concentration is used in the process preceding the cement kiln of the cement production facility, most of the fluorine contained in the filtrate W5 is discharged together with the clinker. It is unlikely that fluorine will circulate in the cement manufacturing process and the fluorine concentration in the clinker will rise extremely. Further, selenium and heavy metals that have not precipitated on the cake C3 side are also discharged together with the clinker.

  Next, a cement kiln bleed dust processing apparatus (hereinafter abbreviated as “processing apparatus”) to which the second embodiment of the processing apparatus for fine powder according to the present invention is applied is shown. The basic configuration is the same as that of the processing apparatus 1 shown in FIG. 1 and is different from the processing apparatus 1 in that a third solid-liquid separator 42 is provided between the flotation machine 25 and the adjustment tank 28. Accordingly, the solid-liquid separator 44 at the rear stage of the adjustment tank 28 becomes the fourth solid-liquid separator. In the following description, in the processing apparatus 41, the same components and substances as those of the processing apparatus 1 are denoted by the same reference numerals and symbols, and detailed description thereof is omitted.

  The configuration of the gas extraction unit 2, the gas processing unit 3, and the adjustment tank 20 to the second solid-liquid separator 26 of the fine powder processing unit 4 of the processing device 41 is the same as that of the processing device 1 of FIG.

  In the processing device 41, the tail T from the flotation machine 25 is solid-liquid separated to produce a cake C3, and the gypsum S is recovered from the third solid-liquid separator 42, and from the third solid-liquid separator 42 An adjustment tank 28 for adjusting pH by adding alkali to the filtrate W3 and a fourth solid-liquid separator 44 for solid-liquid separation of the slurry S6 from the adjustment tank 28 are provided.

  In the present embodiment, since it is configured as described above, in the second solid-liquid separator 26, the floss F from the flotation machine 25 is subjected to solid-liquid separation, and cake C2 is generated to recover heavy metal sulfides. Then, the filtrate W2 generated at this time is supplied to the adjustment tank 20, and the tail T of the flotation machine 25 is supplied to the third solid-liquid separator 42 to generate the cake C3 and collect the gypsum S. To do. On the other hand, the filtrate W3 solid-liquid separated by the third solid-liquid separator 42 is supplied to the adjustment tank 28.

  Next, in the adjustment tank 28, an alkaline agent is added to the filtrate W3, the pH of the filtrate W3 is adjusted, and residual heavy metals such as cadmium are precipitated.

  In the fourth solid-liquid separator 44, the precipitated heavy metals are collected on the cake C4 side, and the filtrate W5 is effectively used in a raw material dryer of a cement manufacturing facility. Even in the present embodiment, even when the filtrate W5 having a relatively high fluorine concentration is used in the preceding stage of the cement kiln of the cement manufacturing facility, most of the fluorine contained in the filtrate W5 is: Since it is discharged together with the clinker, it is unlikely that fluorine will circulate in the cement manufacturing process and the fluorine concentration in the clinker will rise extremely. Moreover, selenium and heavy metals that have not precipitated on the cake C4 side are also discharged together with the clinker.

  In the above embodiment, the fine powder D2 is wet collected using the wet dust collector 11, but the fine powder D2 stored in the tank or the like via the dry dust collector is not directly used in the adjustment tank 20 without using the wet dust collector 11. The slurry may be added while adding water and a sulfurizing agent.

  Moreover, after classifying the coarse powder D1 with the cyclone 10, the exhaust gas G2 containing the fine powder D2 is introduced into the wet dust collector 11. However, the extraction gas G1 extracted by the probe 6 is directly introduced into the wet dust collector 11 without providing the cyclone 10. May be.

  As described above, according to the present embodiment, the filtrate W5 from the third solid-liquid separator 29 or the fourth solid-liquid separator 44 is effectively used in the cement production facility. The cost associated with the wastewater treatment generated by the flotation process can be significantly reduced. In addition, by treating the wastewater generated by the flotation treatment with alkali, it is possible to prevent the circulation of highly volatile components such as cadmium among heavy metals in the system, so there is no adverse effect on the cement. . Furthermore, since no hydrochloric acid or the like is used in the processing of the fine powder, there is no adverse effect such as corrosion on the cement manufacturing facility.

  In the above-described embodiment, the processing method according to the present invention is applied to the dust (such as chlorine bypass dust) contained in the gas extracted from the kiln exhaust gas flow path from the bottom of the cement kiln to the bottom cyclone. Although the case where it applied to a process was illustrated, this invention can be utilized for the process of the fine powder containing fluorine, calcium, selenium, and heavy metals besides these dusts.

DESCRIPTION OF SYMBOLS 1 Processing apparatus 2 Gas extraction part 3 Gas processing part 4 Fine powder processing part 5 Cement kiln 6 Probe 7 Cooling fan 10 Cyclone 11 Wet dust collector 12 Exhaust fan 13 Scrubber 14 Circulating liquid tank 14a Pump 15 Washing tower 20 Adjustment tank 21 First tank Solid-liquid separator 22 Slurry tanks 23, 24 Adjustment tank 25 Flotation machine 26 Second solid-liquid separator 28 Adjustment tank 29 Third solid-liquid separator 30 Wastewater treatment apparatus 41 Treatment apparatus 42 Third solid-liquid separator 44 4th solid-liquid separator G1 Extraction gas G2, G3 Exhaust gas D1 Coarse powder D2 Fine powder S1-S5 Slurry C1-C4 Cake W1-W5 Filtrate F Floss T Tail

Claims (5)

A fine powder containing fluorine, calcium, selenium and heavy metals, water and a sulfiding agent are mixed to produce a slurry,
The slurry is subjected to solid-liquid separation to obtain a solid component and a liquid component, and the liquid component is subjected to wastewater treatment.
After slurrying the solid content, the flotation process,
A method for treating fine powder containing fluorine, calcium, selenium and heavy metals, characterized in that wastewater generated by the flotation treatment is used in a cement production facility.   The fine powder containing fluorine, calcium, selenium and heavy metals according to claim 1, wherein the solid content is slurried and then the floatation treatment is performed by adding sulfuric acid and a scavenger. Method. PH is adjusted by adding alkali to the tail generated by the flotation process,
The tail after the pH adjustment is subjected to solid-liquid separation, and a part of the waste water obtained by solid-liquid separation of the obtained liquid and froth is used in a cement production facility. The processing method of the fine powder containing the fluorine, calcium, selenium, and heavy metals of description.   The fine powder containing fluorine, calcium, selenium and heavy metals is dust contained in a gas extracted from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone. Item 4. A method for treating fine powder containing fluorine, calcium, selenium and heavy metals according to item 1, 2 or 3. Slurry generating means for generating a slurry by mixing fine powder containing fluorine, calcium, selenium and heavy metals, water, and a sulfiding agent;
A solid-liquid separator for solid-liquid separation of the slurry produced by the slurry production means;
A waste water treatment device for treating waste liquid discharged from the solid-liquid separator;
After slurrying the solids discharged from the solid-liquid separator, a flotation machine for flotation treatment,
A processing apparatus for fine powder containing fluorine, calcium, selenium and heavy metals, comprising a cement production facility using waste water of the flotation machine.

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