JP2014108906A - Chlorine bypass system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover a demineralized cake containing less impurities with operation and equipment costs suppressed low and utilize chlorine bypass dust while expanding its applications.SOLUTION: A chlorine bypass system 1 comprises: a probe 3 extracting a part G of flue gas, while cooling, from a kiln exhaust gas flow passage extending from the kiln tail portion of a cement kiln 2 to the lowermost cyclone; a desulfurizer 10 wet-desulfurizing the extracted gas G1 from the probe; and a wet classifier 11 classifying slurry S2 discharged from the desulfurizer. Classification of the slurry discharged from the desulfurizer by the wet classifier provides a gypsum (dihydrate gypsum) slurry of a high purity, and the gypsum slurry is available in various applications, e.g. addition to cement. The classification point of the wet classifier can be 5-15 μm. Solid-liquid separators 12 and 13 for independent solid-liquid separation of slurries S3 and S4 can be provided.

Description

  The present invention relates to a chlorine bypass system for extracting a part of combustion gas from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone of a preheater to remove chlorine and the like.

  In the past, focusing on the fact that the chlorine content is particularly problematic among the chlorine content, sulfur content, alkali content, etc. that cause problems such as blockage of preheaters in cement production facilities, the bottom stage from the kiln bottom of the cement kiln Chlorine bypass systems are used to extract chlorine from a kiln exhaust gas flow path leading up to a cyclone to remove chlorine.

Since the gas discharged from the chlorine bypass system (hereinafter referred to as “chlorine bypass exhaust gas”) contains high-concentration SO ₂ gas, desulfurization treatment is required. Therefore, for example, in Patent Documents 1 and 2, after desulfurizing chlorine bypass exhaust gas using chlorine bypass dust, the slurry after desulfurization is subjected to solid-liquid separation, and a desalted cake mainly composed of salt water and gypsum (hereinafter, referred to as “desulfurized cake”). "Collected gypsum cake").

JP 2011-148861 A JP 2011-144058 A

However, the desalted cake obtained by the chlorine bypass system contains SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ , lead (Pb), and other trace components. Therefore, the inclusion of these components becomes a problem depending on the use, which has been a factor that hinders the use expansion of the recovered gypsum cake.

  Therefore, the present invention has been made in view of the problems in the above-described conventional technology, and is a recovered gypsum cake with less impurities while keeping operating costs and equipment costs low, and effective use and use of the recovered gypsum cake The purpose is to expand

  In order to achieve the above object, the present invention provides a chlorine bypass system for extracting air while cooling a part of combustion exhaust gas from a kiln exhaust gas flow path from a kiln bottom of a cement kiln to a lowermost cyclone of a preheater. And a desulfurization device that wet-desulfurizes the bleed gas from the probe, and a wet classification device that classifies the slurry discharged from the desulfurization device.

  And according to this invention, by classifying the slurry discharged | emitted from a desulfurization apparatus with a wet classifier, it becomes a highly pure gypsum (dihydrate gypsum) slurry, and can collect | recover the recovered gypsum cake with few impurities. Further, the recovered gypsum can be added to cement or used for other purposes, and the use can be expanded while keeping operating costs and equipment costs low.

  The said chlorine bypass system WHEREIN: The classification point of the said wet classifier can be 5 micrometers or more and 15 micrometers or less. Thereby, impurities contained in the slurry from the desulfurization apparatus can be efficiently concentrated in a part of the slurry.

  In the chlorine bypass system, each slurry discharged from the wet classifier can be provided with a solid-liquid separation device that separates solid and liquid separately, and the high-purity gypsum slurry is separated into recovered gypsum cake and salt water, The other slurry can be separated into a dehydrated cake with a large amount of impurities (mainly gypsum) and salt water.

  The chlorine bypass system includes a dry classifier that collects fine powder contained in the extracted gas extracted by the probe, and gas discharged from the dry classifier can be introduced into the desulfurization apparatus. Thereby, only fine powder with a high chlorine content can be processed by the chlorine bypass system.

  The chlorine bypass system includes a cooler that cools the combustion gas extracted by the probe, a dry dust collector that collects dust contained in the gas discharged from the cooler, and a pre-stage of the desulfurizer, And a dissolution tank for dissolving the dust discharged from the dry dust collector in water. Moreover, the said desulfurization apparatus can also be made into a wet scrubber, without providing these.

  As described above, according to the present invention, it is possible to obtain a recovered gypsum cake with few impurities while keeping operating costs and equipment costs low, and it is possible to effectively use the recovered gypsum cake and expand applications.

It is a whole lineblock diagram showing a 1st embodiment of a chlorine bypass system concerning the present invention. It is a whole block diagram which shows 2nd Embodiment of the chlorine bypass system which concerns on this invention. It is a graph which shows the relationship between the particle size of the dust in the slurry produced | generated with the desulfurization apparatus of the chlorine bypass system based on this invention, and lead concentration, Comprising: A vertical axis | shaft is a lead (Pb) concentration rate (times), and a horizontal axis is 10 micrometers. The passage (%) is shown. A graph showing the relationship between the particle size and cement raw material components of the dust in the slurry produced by the desulfurization of chlorine bypass system according to the present invention, the vertical axis represents cement ingredients _{(SiO 2 + Al 2 O 3} + Fe 2 O ₃ minutes) concentration rate (times), horizontal axis indicates 10 μm passage (%). It is a graph which shows the relationship between the particle size of the dust in the slurry produced | generated with the desulfurization apparatus of the chlorine bypass system which concerns on this invention, and the density | concentration of a calcium content, Comprising: A vertical axis | shaft is a concentration rate (times) of a calcium content (Ca content). The horizontal axis indicates the passage (%) of 10 μm.

  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 chlorine bypass system according to the present invention. This system 1 includes a kiln exhaust gas passage from a kiln bottom of a cement kiln 2 to a lowermost cyclone (not shown) of a preheater, A probe 3 for extracting a part of the combustion exhaust gas (reference numeral G in the figure), a cooling fan 4 for rapidly cooling the combustion exhaust gas G by supplying cold air A into the probe 3, and coarse dust D1 contained in the extraction gas G1 A cyclone 5 as a dry classifier for separating the exhaust gas, a cooler 6 for cooling the exhaust gas G2, a bag filter 7 as a dry dust collector for recovering the fine powder D2 contained in the exhaust gas G2, and the fine powder D2 mixed with water W Then, the dissolution tank 8 for generating the slurry S1, the desulfurization device 10 for reacting the exhaust gas G3 of the bag filter 7 and the slurry S1, and the slurry S2 from the desulfurization device 10 are wet-classified. The wet classification device 11, composed of each slurry S3, S4 the two to separate solid-liquid separation in solid-liquid separator 12, 13 or the like from the wet classification device 11.

  The probe 3, the cooling fan 4, the cyclone 5, the cooler 6, and the bag filter 7 are devices used in a conventional chlorine bypass system, and detailed descriptions thereof are omitted.

  The dissolution tank 8 is provided for slurrying the fine powder D2 from the cooler 6 and the bag filter 7 with water W.

  The desulfurization apparatus 10 is provided to desulfurize the exhaust gas G3 supplied from the bag filter 7 through the fan 9 using the slurry S1 supplied from the dissolution tank 8. The desulfurized exhaust gas G4 is returned to an exhaust gas passage such as an outlet of a preheater attached to the cement kiln 2 through an exhaust fan.

The wet classifier 11 uses the slurry S2 from the desulfurizer 10 as a slurry S3 in which cement raw material components (SiO ₂ , Al ₂ O ₃ , Fe ₂ O ₃ ), lead (Pb) and other trace components are concentrated, Gypsum is provided for separation into concentrated slurry S4. Here, as will be described later, in order to efficiently concentrate impurities and gypsum in each of the slurries S3 and S4, the classification point is preferably about 10 μm (5 μm or more and 15 μm or less).

  The solid-liquid separators 12 and 13 separate the slurries S3 and S4 from the wet classifier 11 separately into filtrates L1 and L2, a dehydrated cake C1 containing a large amount of impurities, and a high-purity recovered gypsum cake C2. Provided to do.

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

  The combustion exhaust gas G extracted by the probe 3 is cooled to about 350 to 550 ° C. by the cold air A from the cooling fan 4 and then introduced into the cyclone 5 as the extraction gas G1, and the coarse powder D1 and the chlorine content are unevenly distributed. The exhaust gas G2 containing the fine powder D2 is separated. Here, since the coarse powder D1 has a low chlorine content, it can be returned to the cement raw material system.

  After the exhaust gas G2 including the fine powder D2 discharged from the cyclone 5 is cooled in the cooler 6, the fine powder D2 is recovered by the cooler 6 and the bag filter 7. The recovered fine powder D2 is mixed with water W in the dissolution tank 8 to generate a slurry S1.

  Next, the exhaust gas G3 of the bag filter 7 is introduced into the desulfurization device 10 via the fan 9 and desulfurized using the slurry S1 supplied from the dissolution tank 8. The exhaust gas G4 after desulfurization is returned to the exhaust gas system of the cement kiln 2.

Here, CaO, CaCO ₃ and Ca (OH) ₂ are mixed as calcium compounds in the slurry S 1, and these react with SO ₂ contained in the exhaust gas G 3 of the bag filter 7 in the desulfurization apparatus 10. To dihydrate gypsum (CaSO ₄ .2H ₂ O).

The slurry S2 from the desulfurization apparatus 10 is introduced into the wet classification apparatus 11 and classified at a classification point of about 10 μm. Here, as shown in FIG. 3 and FIG. 4, the amount of Pb, SiO ₂ , Al ₂ O _3, and Fe ₂ O ₃ increases as the amount of passage of 10 μm increases, that is, as the solid content of 10 μm or less increases. Concentration rate increases. On the other hand, as shown in FIG. 5, the concentration of Ca, that is, dihydrate gypsum increases as the passage of 10 μm decreases, that is, the solid content of 10 μm or less is recovered. Thereby, impurities, such as a cement raw material component and lead, can be concentrated on the slurry S3 (fine powder slurry) side from the wet classifier 11, and gypsum can be concentrated on the slurry S4 (coarse powder slurry) side.

  The dehydrated cake C1 having a large amount of impurities obtained by solid-liquid separation by the solid-liquid separation device 12 contains a large amount of impurities such as cement raw material components and lead. Therefore, the dehydrated cake C1 can be reused as a cement raw material or heavy metal can be recovered by concentrating heavy metals. Process in the process. Further, the filtrates L1 and L2 from the solid-liquid separators 12 and 13 are processed by addition to a cement finishing mill, a salt recovery process, wastewater treatment, or the like.

  On the other hand, as described above, the desalted cake C2 obtained by the solid-liquid separator 13 is a high-purity dihydrate gypsum with a low content of the impurities, so that it can be crushed with a clinker and used for cement production. It can be used for other purposes.

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

  This system 21 is characterized in that a wet scrubber 22 is provided instead of the cooler 6 to the desulfurization device 10 of the system 1 shown in FIG. 1, and the other configuration is the same as the system 1.

  The wet scrubber 22 has a main body 22a that cools and removes dust by bringing the fine powder D2 and gas G2 into contact with the slurry S1 from the water and the circulating liquid tank 22b, and a circulating liquid tank 22b that circulates the slurry S1 between the main body 22a, A cleaning tower 22c for spraying industrial water and a circulation pump 22d are provided.

  Also in this system 21, the combustion exhaust gas G extracted by the probe 3 is cooled to about 350 to 550 ° C. by the cold air A from the cooling fan 4, and then introduced into the cyclone 5 as the extraction gas G <b> 1. In the cyclone 5, the extracted gas G1 is separated into coarse powder D1 and exhaust gas G2 containing fine powder D2 in which the chlorine content is unevenly distributed, and the coarse powder D1 is returned to the cement raw material system.

The exhaust gas G2 containing the fine powder D2 discharged from the cyclone 5 is introduced into the wet scrubber 22, and the wet scrubber 22 removes the dust D2 contained in the combustion exhaust gas G2 while being cooled by the slurry S1 supplied from the circulating liquid tank 22b. In addition, the calcium compound constituting the slurry S1 is desulfurized, and the calcium compound in the slurry S1 is converted into dihydrate gypsum (CaSO ₄ .2H ₂ O) by a desulfurization reaction with SO ₂ contained in the exhaust gas G2. The exhaust gas G4 discharged from the cleaning tower 22c of the wet scrubber 22 is returned to an exhaust gas flow path such as an outlet of a preheater attached to the cement kiln 2 through an exhaust fan.

  The slurry S2 from the wet scrubber 22 is introduced into the wet classifier 11, and thereafter, through a process similar to that of the first embodiment shown in FIG. 1, the cement is placed on the slurry S3 (fine slurry) side from the wet classifier 11. The dehydrated cake C1 having a large amount of impurities obtained by concentrating the raw material components and impurities such as lead and gypsum on the slurry S4 (coarse slurry) side and solid-liquid separation by the solid-liquid separation device 12 Because it contains a lot of impurities such as lead, it can be reused as a raw material for cement, or it can be processed in the heavy metal recovery process by concentrating heavy metals. The filtrates L1 and L2 from the solid-liquid separators 12 and 13 are processed by addition to a cement finishing mill, a salt recovery process, wastewater treatment, or the like. The desalted cake C2 obtained by the solid-liquid separator 13 is a high-purity dihydrate gypsum with a low content of impurities, and can be used for cement production by pulverizing with a clinker or for other uses. it can.

  As described above, in the present embodiment, since the wet scrubber 22 is installed instead of the cooler 6 to the desulfurization device 10 of the system 1 in FIG. 1, the equipment cost and the operation cost can be reduced as compared with the system 1. it can.

DESCRIPTION OF SYMBOLS 1 Chlorine bypass system 2 Cement kiln 3 Probe 4 Cooling fan 5 Cyclone 6 Cooler 7 Bag filter 8 Dissolution tank 9 Fan 10 Desulfurization device 11 Wet classification device 12, 13 Solid-liquid separation device 21 Chlorine bypass system 22 Wet scrubber 22a Main body 22b Circulation Liquid tank 22c Cleaning tower 22d Circulation pump A Cold air C1, C2 Desalination cake D1 Coarse powder D2 Fine powder G Part of combustion exhaust gas G1 Extraction gas G2-G4 Exhaust gas L1, L2 Filtration S1-S4 Slurry W Water

Claims (6)

A probe for extracting air while cooling a part of the combustion exhaust gas from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the lowermost cyclone of the preheater,
A desulfurization apparatus for desulfurizing the extracted gas by the probe in a wet manner;
A chlorine bypass system comprising: a wet classifier for classifying the slurry discharged from the desulfurizer.   2. The chlorine bypass system according to claim 1, wherein a classification point of the wet classification apparatus is 5 μm or more and 15 μm or less.   3. The chlorine bypass system according to claim 1, further comprising a solid-liquid separation device that separates each of the slurry discharged from the wet classifier separately.   The dry classification apparatus which collects the fine powder contained in the extraction gas extracted by the probe is provided, and the gas discharged from the dry classification apparatus is introduced into the desulfurization apparatus. Chlorine bypass system. In the previous stage of the desulfurization unit,
A cooler for cooling the combustion gas extracted by the probe or the gas discharged from the dry classifier;
A dry dust collector for collecting dust contained in the gas discharged from the cooler;
A dissolution tank for adding water to the dust discharged from the dry dust collector to make a slurry,
The chlorine bypass system according to any one of claims 1 to 4, wherein the slurry obtained in the dissolution tank is supplied to the desulfurization apparatus.   The chlorine bypass system according to any one of claims 1 to 4, wherein the desulfurization apparatus is a wet scrubber.

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