JP5680450B2 - Chlorine bypass exhaust gas treatment device and treatment method - Google Patents

Description

  The present invention relates to an apparatus and a method for treating gas discharged from a chlorine bypass facility for extracting chlorine from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone to remove chlorine. About.

  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 From the kiln exhaust gas flow path, a chlorine bypass facility for extracting a part of combustion gas and removing chlorine is used.

  As shown in FIG. 3, the chlorine bypass facility includes a probe 53 for extracting a part of combustion gas from a kiln exhaust gas flow path from the bottom of the kiln 52 to the lowermost cyclone (not shown), and a probe 53. A cooling fan 54 for rapidly cooling the extraction gas G1 by supplying cold air therein, a cyclone 55 as a classifier for separating the coarse dust D1 contained in the extraction gas G1, and a fine powder D2 discharged from the cyclone 55 A cooler 56 that cools the extracted gas G2, a cooling fan 57 that supplies cool air to the cooler 56, a bag filter 58 that collects dust dust D2 in the extracted gas G2 cooled by the cooler 56, and cooling A dust tank 59 for collecting the fine powder D2 discharged from the vessel 56 and the bag filter 58, a dissolution tank 60 for dissolving the fine powder D2 from the dust tank 59 in water, A solid-liquid separation device 61 for solid-liquid separation of the slurry S1 from the tank 60 into a water-washed cake C and waste water L is provided, and the water-washed cake C separated from the solid and liquid and the residue R after waste water treatment are kiln. The system is returned to the system, and the waste water L is discharged after the waste water treatment.

In the chlorine bypass facility 51, since a large amount of SO ₂ is contained in the exhaust gas G3 of the bag filter 58, the exhaust gas G3 cannot be discharged out of the system as it is, and a kiln system is provided via an exhaust fan (not shown). I was returning. At this time, if the exhaust gas G3 is returned to the outlet side of the fan (IDF) for attracting the exhaust gas from the cement kiln 52, there is a problem that SO ₂ in the exhaust gas released from the chimney to the atmosphere increases. Moreover, when the exhaust gas G3 is returned to the preheater attached to the cement kiln 52, there is a problem that the heat loss of the cement firing system and the clinker production amount are reduced, and that the trouble of coaching due to the concentration of sulfur is caused. is there.

  Therefore, the present invention was made in view of the problems in the above-described conventional technology, and the gas discharged from the chlorine bypass facility (chlorine bypass exhaust gas) without increasing the heat loss of the cement firing system, The objective is to process at low cost while ensuring stable operation of the cement firing system.

  In order to achieve the above-mentioned object, the present invention is a chlorine bypass exhaust gas treatment apparatus, which bleeds while cooling a part of combustion gas from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone. A first dissolution tank attached to a chlorine bypass facility for recovering chlorine bypass dust from the extracted gas, and slurried while adding an alkaline agent to the recovered chlorine bypass dust, and produced in the first dissolution tank A solid-liquid separation device for solid-liquid separation of the formed slurry, a second dissolution tank for re-dissolving the cake generated in the solid-liquid separation device, and a slurry after re-dissolution generated in the second dissolution tank And a desulfurization tower for desulfurization of the exhaust gas by contacting the exhaust gas with the exhaust gas of the chlorine bypass facility.

Then, according to the present invention, by adding an alkali agent to the chlorine bypass dust, varying the CaCl ₂ and CaCO ₃ contained in the chlorine bypass dust to Ca (OH) _2, chlorine bypass the Ca (OH) ₂ Since it is used for desulfurization of equipment exhaust gas, calcium contained in chlorine bypass dust can be effectively used for desulfurization, and stable operation of the cement firing system is ensured without increasing the heat loss of the cement firing system. However, the chlorine bypass exhaust gas can be treated at a low cost.

In addition, in order to remove potassium and chlorine in the slurry in the solid-liquid separator, the chlorine content of the re-dissolved slurry is low, and it is possible to minimize the dissolution of gypsum causing scale trouble, It is possible to suppress the production of singenite (K ₂ Ca (SO ₄ ) ₂ ) or the like that hinders the effective use of the recovered material.

Furthermore, since CaCl ₂ dissolves in water, if it is not changed to Ca (OH) ₂ , it will be contained in the industrial salt recovered later, and this will cause a decrease in the purity of the industrial salt. since the varied hard Ca (OH) ₂ dissolved in water by reaction with, it is also possible to prevent a reduction in the purity of the industrial salt.

  In addition, lead (Pb) and selenium (Se) among the heavy metals contained in the chlorine bypass dust are contained in the filtrate side by adding an alkali agent. Since selenium is included in the recovered industrial salt, there is no problem, so that lead and selenium can be efficiently removed from the chlorine bypass dust.

  In the chlorine bypass exhaust gas treatment device, a second solid-liquid separation device for solid-liquid separation of the slurry discharged from the desulfurization tower, and a filtrate solid-liquid separated by the second solid-liquid separation device are used for the second treatment. Supply means for supplying to the dissolution tank. As a result, the filtrate separated from the solid and the liquid can be recycled and used effectively, and gypsum can be recovered on the cake side.

  In the chlorine bypass exhaust gas treatment apparatus, a sulfiding agent and a pH adjuster are added to the filtrate separated by solid-liquid separation in the first solid-liquid separation device, and an adjustment tank is provided that insolubilizes heavy metals contained in the filtrate. Can do. As a result, lead or the like can be insolubilized and efficiently recovered at a later stage.

  The said chlorine bypass waste gas processing apparatus can be equipped with the 3rd solid-liquid separation apparatus which carries out solid-liquid separation of the filtrate discharged | emitted from the said adjustment tank. As a result, heavy metals such as lead can be recovered on the cake side.

  The chlorine bypass exhaust gas treatment apparatus may further include a salt recovery device that recovers salt from the filtrate discharged from the third solid-liquid separation device, and further, heat recovered from the extracted gas is supplied to the salt recovery device. A gas gas heater used for salt recovery can be provided. Thereby, salt can be recovered while effectively using the heat of the chlorine bypass exhaust gas.

  The gas gas heater can recover heat from the exhaust gas of a high-temperature dust collector that collects the extracted gas, and heat efficiency is improved by recovering heat from the removed high-temperature gas.

Further, the present invention is a method for treating chlorine bypass exhaust gas, wherein a part of the combustion gas is extracted from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the lowest cyclone, and extracted from the extracted gas. In a chlorine bypass facility for recovering chlorine bypass dust, after slurrying while adding an alkali agent to the recovered chlorine bypass dust, the slurry is dehydrated, the resulting cake is redissolved, and the cake is redissolved The slurry is brought into contact with the exhaust gas of the chlorine bypass facility, and the exhaust gas is desulfurized. According to the present invention, similarly to the above-described invention, it is possible to treat the chlorine bypass exhaust gas by effectively using calcium contained in the chlorine bypass dust for desulfurization, and minimize the dissolution of gypsum causing scale trouble. In addition, it is possible to suppress the production of syngenite (K ₂ Ca (SO ₄ ) ₂ ) that inhibits the effective use of the recovered material, and it is possible to prevent a decrease in the purity of the industrial salt to be recovered. Further, lead and selenium can be efficiently removed from the chlorine bypass dust.

In the chlorine bypass exhaust gas treatment method, the pH of the slurry can be adjusted to 13 or more and 14 or less, and CaCl ₂ and CaCO ₃ contained in the chlorine bypass dust are efficiently changed to Ca (OH) ₂ in this pH region. Can be made.

  As described above, according to the present invention, chlorine bypass exhaust gas can be processed at low cost while ensuring stable operation of the cement firing system without increasing the heat loss of the cement firing system.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows 1st Embodiment of the processing apparatus of the chlorine bypass waste gas concerning this invention. It is a whole block diagram which shows 2nd Embodiment of the processing apparatus of the chlorine bypass waste gas concerning this invention. It is a whole block diagram which shows the conventional chlorine bypass installation.

  Next, modes for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a chlorine bypass facility provided with a first embodiment of a chlorine bypass exhaust gas treatment apparatus according to the present invention. The chlorine bypass facility 1 is arranged from the kiln bottom of a cement kiln 2 to a lowermost cyclone (not shown). From the kiln exhaust gas flow path leading to the air, a probe 3 for extracting a part of the combustion gas while being cooled by cold air from the cooling fans 4 and 5, and coarse dust of dust contained in the extracted gas G1 extracted by the probe 3 A cyclone 6 that separates D1, a cooler 7 that cools the extracted gas G2 containing fine powder D2 discharged from the cyclone 6, a bag filter 8 that collects the extracted gas G3 from the cooler 7, and a bag filter 8 A desulfurization tower 11 that performs a desulfurization treatment of the exhaust gas G4 supplied via the fan 10, and a dust that stores dust D5 (D3 + D4) discharged from the cooler 7 and the bag filter 8 The tank 9, the first dissolution tank 12 that is slurried while adding an alkaline agent to the dust (chlorine bypass dust) D 6 discharged from the dust tank 9, and the slurry S 1 discharged from the first dissolution tank 12 are solidified. The first solid-liquid separation device 13 for liquid separation, the second solid-liquid separation device 15 for solid-liquid separation of the slurry S3 generated in the desulfurization tower 11, and the cake C1 discharged from the first solid-liquid separation device 13 Is dissolved in the filtrate L2 (circulated water CW) from the second solid-liquid separator 15 and the filtrate L1 discharged from the first solid-liquid separator 13 is added with a sulfiding agent and pH adjustment. The adjustment tank 16 to which the agent is added, the third solid-liquid separation device 17 for solid-liquid separation of the filtrate L3 discharged from the adjustment tank 16, and the like. About the structure of the probe 3-the dust tank 9, since it is the structure similar to the conventional chlorine bypass installation except the point which cools the combustion gas G with the two cooling fans 4 and 5, detailed description is abbreviate | omitted.

The first dissolution tank 12 slurries the dust D6 from the dust tank 9 using water (or hot water) and adds an alkali agent such as NaOH to convert CaCl ₂ and CaCO ₃ contained in the dust D6 into Ca. Provided to change to (OH) ₂ .

  The first solid-liquid separator 13 is provided for solid-liquid separation of the slurry S1 discharged from the first dissolution tank 12. The cake C1 subjected to the solid-liquid separation is supplied to the second dissolution tank 14, and the filtrate L1 is supplied to the adjustment tank 16.

  The second dissolution tank 14 is provided for re-dissolving the cake C1 discharged from the first solid-liquid separator 13, and the slurry S2 obtained by dissolving the cake C1 in the circulating water CW is a bug in the desulfurization tower 11. It is used for desulfurization of the exhaust gas G4 of the filter 8.

  The desulfurization tower 11 is provided to desulfurize the exhaust gas G4 supplied from the bag filter 8 through the fan 10 using the slurry S2 supplied from the second dissolution tank 14. The slurry S3 containing dihydrate gypsum generated by the desulfurization is returned to the second solid-liquid separator 15, and the desulfurized exhaust gas G5 is returned to the exhaust gas system of the cement kiln 2.

  The second solid-liquid separation device 15 is provided for solid-liquid separation of the slurry S3 supplied from the desulfurization tower 11, and the filtrate L2 obtained by solid-liquid separation is recirculated in the second dissolution tank 14 as circulating water CW. Used. On the other hand, dihydrate gypsum Gy is recovered on the cake C2 side where the solid-liquid separation is performed.

The adjustment tank 16 is provided to add a sulfurizing agent such as NaSH or a pH adjusting agent to the filtrate L1 discharged from the first solid-liquid separation device 13 so as to insolubilize heavy metals such as lead. As the pH adjuster, NaOH, Ca (OH) ₂ , CaO, Mg (OH) ₂ , sulfuric acid or the like can be used.

  The third solid-liquid separation device 17 is provided for solid-liquid separation of the filtrate L3 discharged from the adjustment tank 16, and industrial salt may be recovered from the filtrate L4 subjected to solid-liquid separation by a salt recovery device, Waste water can also be treated. Further, heavy metals such as lead are recovered on the cake C3 side where the solid-liquid separation is performed.

  Next, operation | movement of the chlorine bypass installation 1 which has the said structure is demonstrated, referring FIG.

  While extracting a part G of the combustion gas from the kiln exhaust gas flow path from the kiln bottom of the cement kiln 2 to the lowermost cyclone by the probe 3, it is cooled by the cold air from the cooling fans 4, 5. Thereby, microcrystals of the chlorine compound are generated. Since the fine crystals of the chlorine compound are unevenly distributed on the fine powder side of the dust contained in the extraction gas G1, the coarse powder D1 classified by the cyclone 6 is returned to the preheater attached to the cement kiln 2 as a cement raw material.

  The extraction gas G2 containing the fine powder D2 separated by the cyclone 6 is introduced into the cooler 7, and heat exchange between the extraction gas G2 and the medium is performed. The extracted gas G3 cooled by heat exchange is introduced into the bag filter 8, and the bag filter 8 collects the dust D4 contained in the extracted gas G3. The dust D4 collected by the bag filter 8 is temporarily stored in the dust tank 9 as the dust D5 together with the dust D3 discharged from the cooler 7, and is introduced into the first dissolution tank 12 as the dust D6.

The dust D6 introduced into the first dissolution tank 12 is mixed with water (or warm water) and an alkaline agent such as NaOH in the first dissolution tank 12 to generate a slurry S1. Here, the pH in the first dissolution tank 12 is adjusted to 13.5 ± 0.5. As a result, CaCl ₂ and CaCO ₃ contained in the dust D6 react with the alkali agent to generate Ca (OH) ₂ , and these calcium components can be effectively used for desulfurization in the desulfurization tower 11 at the subsequent stage. As the alkaline agent, KOH or the like can be used in addition to NaOH.

In addition, since CaCl ₂ is dissolved in water, it is contained in the recovered filtrate L4 of the third solid-liquid separation device 17 in the subsequent stage unless it is converted into Ca (OH) ₂ by reacting with the alkali agent. It will be included in the salt. As a result, since the purity of the industrial salt is lowered, the reaction with the alkali agent also has an effect of preventing the purity of the industrial salt from being lowered.

  Furthermore, lead (Pb) and selenium (Se) among heavy metals contained in the dust D6 are separated into the filtrate L1 and the filtrate L2 in the ratio shown in FIG. Since a large amount is supplied, lead can be efficiently recovered through the adjustment tank 16 and the third solid-liquid separator 17 at the subsequent stage. Selenium is rarely recovered by the adjustment tank 16 and the third solid-liquid separation device 17, but there is no problem even if it is included in the recovered industrial salt, so it should be efficiently removed from the dust D6. Can do. On the other hand, insoluble metals such as cadmium, copper, zinc, lead, selenium and fluorine compounds contained in the cake C1 are finally discharged out of the system together with the gypsum Gy in the second solid-liquid separator 15.

  Next, the slurry S1 discharged from the first dissolution tank 12 is subjected to solid-liquid separation by the first solid-liquid separation device 13, and the cake obtained by solid-liquid separation while solid-liquid separation of the slurry S1 is washed with water. Remove chlorine. The cake C1 from which the chlorine content has been removed is supplied to the second dissolution tank 14 and the re-dissolved slurry S2 is supplied to the desulfurization tower 11 and used for desulfurization. The exhaust gas G5 after desulfurization is introduced into the exhaust gas system of the cement kiln 2.

Here, Ca (OH) ₂ present in the re-dissolved slurry S2 reacts with SO ₂ contained in the exhaust gas G4 of the bag filter 8 in the desulfurization tower 11, and dihydrate gypsum (CaSO ₄ .2H ₂ O). Converted to At this time, since the potassium and chlorine contents were removed in the first solid-liquid separator 13, the chlorine content of the slurry S2 obtained by re-dissolving the cake C1 is low, and the dissolution of gypsum causing scale trouble is minimized. In addition, it is possible to suppress the formation of singenite (K ₂ Ca (SO ₄ ) ₂ ). In addition, when syngenite is added to cement, the production must be suppressed because it affects cement quality, particularly strength.

  Next, the slurry S3 discharged from the desulfurization tower 11 is solid-liquid separated by the second solid-liquid separator 15 and the dihydrate gypsum Gy obtained on the cake C2 side is pulverized together with the cement clinker by a cement mill to produce cement. Can be used. On the other hand, the separated filtrate L2 can be reused for the production of the slurry S2 in the second dissolution tank 14 as the circulating water CW.

On the other hand, the filtrate L1 solid-liquid separated by the first solid-liquid separator 13 is supplied to the adjustment tank 16, and a sulfurizing agent such as NaSH or a pH adjuster is added to the filtrate L1 to precipitate heavy metals such as lead. Then, the solid-liquid separation is performed by the third solid-liquid separation device 17 to recover the heavy metal on the cake C3 side. If necessary, a filter aid is added before the filtrate L3 is supplied to the third solid-liquid separator 17. Further, industrial salt may be recovered from the filtrate L4 subjected to solid-liquid separation by the third solid-liquid separation device 17, and the filtrate L4 may be discharged after the waste water treatment. When the industrial salt is recovered, CaCl ₂ is changed to Ca (OH) ₂ as described above, so that an industrial salt having a low calcium concentration and a high KCl content can be obtained.

  Next, a second embodiment of the chlorine bypass exhaust gas treatment apparatus according to the present invention will be described with reference to FIG.

  The chlorine bypass facility 31 includes a high-temperature dust collector 32 instead of the cooler 7 and the bag filter 8 of the chlorine bypass facility 1, and a gas gas heater 33 is disposed after the high-temperature dust collector 32, and the atmosphere heated by the gas gas heater 33. Is used for salt recovery. Since the other components of the chlorine bypass facility 31 are the same as those of the chlorine bypass facility 1 shown in FIG. 1, the same reference numerals are given and description thereof is omitted.

  The high-temperature dust collector 32 is, for example, a heat-resistant bag filter having a heat resistance up to about 900 ° C. or a high-temperature processing type electric dust collector having a heat resistance up to about 900 ° C., and the fine dust D2 discharged from the cyclone 6 is collected. The extracted gas G2 is collected without cooling, and the collected dust (chlorine bypass dust) D3 is supplied to the dust tank 9.

  The gas gas heater 33 is provided to heat the air A1 taken from the surroundings by the extracted gas G3 discharged from the high temperature dust collector 32 and to use the high temperature air A2 heated by the gas gas heater 33 for subsequent salt recovery. Further, the heat exchange with the air A2 enables the temperature of the exhaust gas G4 to be desulfurized in the desulfurization tower 11 to be adjusted, and the occurrence of consolidation can be suppressed. Further, the heat recovered by the gas gas heater 33 may be used for raising the temperature of the exhaust gas G5 in the desulfurization tower 11.

  With the above configuration, the extraction gas G2 containing the fine powder D2 separated by the cyclone 6 is introduced into the high temperature dust collector 32, the dust D2 contained in the extraction gas G2 is collected in the high temperature dust collector 32, and the dust D3 discharged from the high temperature dust collector 32 is collected. Is temporarily stored in the dust tank 9 and introduced into the first dissolution tank 12 as dust D4. In addition, the air A1 taken from the surroundings and the exhaust gas G3 of the high temperature dust collector 32 are introduced into the gas gas heater 33, and after heat exchange between them, the high temperature air A2 is used for salt recovery and discharged from the gas gas heater 33. The exhaust gas G4 is introduced into the desulfurization tower 11 and then desulfurized. Other flows are the same as in the case of the chlorine bypass facility 1.

  As described above, the chlorine bypass exhaust gas treatment apparatus according to the present embodiment has the same effect as that of the first embodiment, and uses the sensible heat of the chlorine bypass exhaust gas for salt recovery. Can be reduced.

  Moreover, in the said embodiment, although the case where the dust D6 was dissolved in the dissolution tank 12 was demonstrated, when calcium content is insufficient, the coarse powder D1 isolate | separated with the cyclone 6 is fractionated, and dissolution tank 12 or It can also be dissolved in the dissolution tank 14 to supplement the calcium content.

DESCRIPTION OF SYMBOLS 1 Chlorine bypass facility 2 Cement kiln 3 Probe 4, 5 Cooling fan 6 Cyclone 7 Cooler 8 Bag filter 9 Dust tank 10 Fan 11 Desulfurization tower 12 1st dissolution tank 13 1st solid-liquid separation apparatus 14 2nd dissolution tank 15 Second solid-liquid separator 16 Adjustment tank 17 Third solid-liquid separator 31 Chlorine bypass facility 32 High-temperature dust collector 33 Gas gas heater

Claims (9)

Extracted while cooling a part of the combustion gas from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the bottom cyclone, and attached to a chlorine bypass facility for recovering chlorine bypass dust from the extracted gas,
A first dissolution tank that is slurried while adding an alkali agent to the recovered chlorine bypass dust;
A solid-liquid separation device for solid-liquid separation of the slurry produced in the first dissolution tank;
A second dissolution tank for re-dissolving the cake produced by the solid-liquid separator;
An apparatus for treating chlorine bypass exhaust gas, comprising: a desulfurization tower configured to contact the exhaust gas of the chlorine bypass facility with the redissolved slurry generated in the second dissolution tank and desulfurize the exhaust gas.   A second solid-liquid separation device for solid-liquid separation of the slurry discharged from the desulfurization tower, and a supply means for supplying the filtrate separated by the second solid-liquid separation device to the second dissolution tank The chlorine bypass exhaust gas treatment device according to claim 1, comprising:   3. A control tank for adding a sulfiding agent and a pH adjuster to the filtrate solid-liquid separated by the first solid-liquid separator and insolubilizing heavy metals contained in the filtrate is provided. An apparatus for treating chlorine bypass exhaust gas as described in 1. The chlorine bypass exhaust gas treatment device according to claim 3 , further comprising a third solid-liquid separation device for solid-liquid separation of the filtrate discharged from the adjustment tank.
  The chlorine bypass exhaust gas treatment device according to claim 4, further comprising a salt recovery device that recovers salt from the filtrate discharged from the third solid-liquid separation device.   The chlorine bypass exhaust gas treatment device according to claim 5, further comprising a gas gas heater that uses heat recovered from the extracted gas for salt recovery in the salt recovery device.   The said gas gas heater collect | recovers heat | fever from the exhaust gas of the high temperature dust collector which collects the said extraction gas, The chlorine bypass waste gas processing apparatus of Claim 6 characterized by the above-mentioned. In the chlorine bypass facility for extracting the chlorine bypass dust from the extracted gas while extracting a part of the combustion gas from the kiln exhaust gas passage from the kiln bottom of the cement kiln to the lowermost cyclone,
After slurrying while adding an alkali agent to the recovered chlorine bypass dust, the slurry is dehydrated,
Redissolve the resulting cake,
A method for treating a chlorine bypass exhaust gas, wherein the slurry in which the cake is re-dissolved is brought into contact with the exhaust gas of the chlorine bypass facility to desulfurize the exhaust gas.   The chlorine bypass exhaust gas treatment method according to claim 8, wherein the pH of the slurry is adjusted to 13 or more and 14 or less.

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