JP5068698B2 - Cement kiln extraction gas processing system and processing method - Google Patents

Description

  The present invention relates to a cement kiln extraction gas processing system and a processing method, and in particular, extracts a part of combustion gas from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone to remove chlorine. It relates to systems.

  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.

  This chlorine bypass system is, for example, as described in Patent Document 1, after cooling the extracted combustion gas, the dust in the exhaust gas is separated into coarse powder and fine powder by a classifier, and the separated chlorine content is separated. This system recovers fine powder (chlorine bypass dust) containing a large amount of (potassium chloride / KCl).

  The fine powder can be collected by dry dust collection method or wet dust collection method. Among these, in the treatment system using wet dust collection method, the extraction gas from the kiln exhaust gas flow path is introduced into the wet dust collector. In the scrubber section of the wet dust collector, water is sprayed to form a collection medium, and fine powder is separated from the extracted gas. At that time, the chlorine content (KCl) contained in the fine powder is dissolved in the liquid. Moreover, the sulfur content in the extraction gas is reacted with slaked lime or the like to produce gypsum. The gas from which fine powder has been removed (hereinafter referred to as “clean gas” as appropriate) is discharged to the atmosphere through an exhaust fan, while the slurry is separated into solid and liquid to recover gypsum. It is treated and discharged into sewage or the ocean (for example, see Patent Document 2).

International Publication No. 97/21638 Pamphlet International Publication No. 2006/035631 Pamphlet

  As described above, in the processing system using the wet dust collecting method, the scrubber section sprays water on the extraction gas to collect fine powder, but the extraction gas discharged from the classifier is high temperature, so the wet dust collector When water is sprayed on, water evaporates and a large amount of water vapor is generated. On the other hand, heat is exchanged in the scrubber portion, and the temperature is lowered. Therefore, the water vapor is attracted to the exhaust fan together with the clean gas and flows in the exhaust pipe, but is condensed in the process and adheres to the exhaust fan and the pipeline. Since the moisture is acidic, there is a problem that the exhaust fan and the pipe are corroded.

  In addition, inside the wet dust collector, some of the generated slurry may scatter and flow into the exhaust pipe. The gypsum contained in the dispersed slurry may be condensed due to moisture condensed, the viscosity of the slurry, etc. There is a problem that it adheres to the surface and causes vibration and failure.

  Therefore, the present invention has been made in view of the above-described problems in the prior art, and when wet collecting dust from cement kiln bleed gas, acidic moisture and gypsum content in the slurry are exhaust fans and exhaust. The purpose is to prevent adhesion to the inside of the pipe and to prevent corrosion and failure of those facilities.

In order to solve the above problems, the present invention is a cement kiln extraction gas processing system for extracting a part of combustion gas from a kiln exhaust gas passage from the bottom of the cement kiln to the lowest cyclone. A cooling device that cools the extraction gas extracted by the extraction device, a wet dust collector that wet-collects dust contained in the extraction gas cooled by the cooling device, and a gas discharged from the wet dust collector. A temperature raising device for heating, and the cooling device and the temperature raising device are one heat exchanger that exchanges heat between the extracted gas extracted by the extraction device and the gas discharged from the wet dust collector. Oh, wherein the Rukoto.

According to the present invention, since the extraction gas extracted by the extraction device is cooled and then introduced into the wet dust collector, generation of a large amount of water vapor in the wet dust collector can be avoided. Therefore, it becomes possible to prevent acidic moisture from adhering to the exhaust fan and the exhaust pipe and corroding those facilities. In addition, the temperature of the exhaust gas discharged from the wet dust collector is raised, so that the gypsum content in the slurry can be prevented from sticking to the exhaust fan and exhaust pipe, and the rate of vibration and failure can be reduced. become. Further, since the cooling equipment and the temperature raising equipment can be integrated, not only the equipment cost can be reduced, but also the extracted gas extracted by the extraction device can be used as the heat source for temperature raising. Therefore, effective utilization of thermal energy can be achieved.

  The cement kiln extraction gas processing system includes a solid-gas separation device disposed between the extraction device and the cooling device and having heat resistance of at least 300 ° C., and the extraction gas extracted by the extraction device is 300 ° C. The solid-gas separation apparatus can be introduced at a temperature of 700 ° C. or lower. According to this, since the extraction gas can be solid-gas separated while maintaining the temperature higher than the resynthesis temperature of dioxins, it is possible to suppress the resynthesis of dioxins.

  The cement kiln extraction gas processing system includes a classifier for separating coarse powder from the extraction gas extracted by the extraction device, and the exhaust gas containing fine powder discharged from the classification device is supplied to the cooling device or the heat exchanger. Can be supplied.

The present invention is also a method for treating a cement kiln extraction gas, wherein a part of the combustion gas is extracted from a kiln exhaust gas passage from the bottom of the cement kiln to the bottom cyclone, and the extracted extraction gas was wet type dust collector the dust contained in the bleed gas after cooling, by elevating the temperature of the exhaust gas after removal of dust by wet type dust collector, the cooling and temperature rise was removing the dust and the extracted gas It is characterized by carrying out at the same time by heat exchange with later exhaust gas . According to the present invention, as in the case of the above-described invention, it is possible to suppress acidic moisture and gypsum content in the slurry from adhering to the exhaust fan and the exhaust pipe, and to prevent corrosion and failure of those facilities. Become. Further, since the cooling equipment and the temperature raising equipment can be integrated, not only the equipment cost can be reduced, but also the extracted gas extracted by the extraction device can be used as the heat source for temperature raising. Therefore, effective utilization of thermal energy can be achieved.

  As described above, according to the present invention, when wet dust is collected from cement kiln bleed gas, acidic moisture and gypsum content in the slurry are prevented from adhering to the exhaust fan and exhaust pipe, and their facilities It is possible to prevent corrosion and breakdown of the product.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an embodiment of a cement kiln extraction gas processing system according to the present invention. The processing system 1 is roughly composed of a gas extraction unit 2 and a gas processing unit 3.

  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 separates a probe 6 for extracting combustion gas, a cooling fan 7 for supplying cold air into the probe 6 to rapidly cool the extraction gas G1, and coarse powder D1 in dust contained in the extraction gas G1. It consists of cyclone 10 etc. as a classifier.

  The gas processing unit 3 is a facility for collecting water-soluble components and fine powder D2 from the exhaust gas G2 discharged from the cyclone 10, and washing the collected fine powder D2 and the like with water. The gas processing unit 3 includes a high-temperature bag filter 11 that collects the fine powder D2 contained in the exhaust gas G2, a heat exchanger 13 that recovers heat from the exhaust gas G3 of the high-temperature bag filter 11, and the exhaust gas cooled by the heat exchanger 13. It comprises a wet dust collector 15 that removes residual dust and sulfur from G4.

  The high-temperature bag filter 11 collects fine powder D2 from the exhaust gas G2 from the cyclone 10, and is thermally decomposed in the cement kiln 5 such as dioxins (PCDD, PCDF, co-PCB), polychlorinated biphenyls (PCBs), and the like. Provided to prevent resynthesis of persistent organic pollutants (POPs). The high-temperature bag filter 11 is, for example, a bag filter including a ceramic filter, and is a high heat-resistant solid-gas separation device having heat resistance up to about 900 ° C.

  Various types of such bug filters have been developed, such as those in which a plurality of rod-shaped ceramic tubes (ceramic filters) formed into honeycomb cells are arranged, and those using a sheet-like ceramic filter. The filter type is not particularly limited as long as it can collect fine particles of 0.1 μm or more from the exhaust gas G2.

  In general, since the temperature of the extraction gas G1 immediately after extraction from the probe 6 is 700 ° C. or less, the high-temperature bag filter 11 does not necessarily have heat resistance up to 900 ° C., and heat resistance up to at least 700 ° C. Sex is enough. An induction fan 12 that attracts the exhaust gas G3 after removing the fine powder D2 and introduces it into the heat exchanger 13 is provided at the subsequent stage of the high-temperature bag filter 11.

  The heat exchanger 13 is provided to cool the exhaust gas G3 discharged from the high temperature bag filter 11 and to raise the temperature of the exhaust gas (clean gas) G5 discharged from the wet dust collector 15. Inside the heat exchanger 13, a pipe line 13a for circulating a heat medium is provided. The inlet of the heat medium of the pipe line 13a is connected to an exhaust pipe 15a extending from the wet dust collector 15, while the outlet of the heat medium is connected to an unillustrated raw material mill, a sludge dryer or the like via an exhaust fan 14. Connected.

The wet dust collector 15 collects residual dust from the exhaust gas G4 cooled by the heat exchanger 13, and the sulfur content (SO ₂ ) in the exhaust gas G4 reacts with water by the quick lime (CaO) contained in the fine powder D2. It is prepared to react with slaked lime (Ca (OH) ₂ ) generated in this way to produce gypsum (CaSO ₄ .2H ₂ O). The wet dust collector 15 includes a scrubber 16, a circulating liquid tank 17, and a cleaning tower 18, and a pump 16 a for circulating the slurry is provided between the scrubber 16 and the circulating liquid tank 17.

The slurry S produced by the wet dust collector 15 contains fine powder D2 supplied from the high-temperature bag filter 11 and slaked lime generated by reaction of quick lime in the dust remaining in the exhaust gas G4 with water. The sulfur content (SO ₂ ) present reacts with slaked lime 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 G4 is removed, and gypsum (CaSO ₄ .2H ₂ O) is generated. For the purpose of supplementing slaked lime, a slaked lime slurry storage tank 21 and a pump 21a for supplying slaked lime slurry are connected to the slurry circulation path 16b. In addition, the circulating liquid tank 17 is provided with a sulfuric acid storage tank 20 and a pump 20a that supply sulfuric acid and adjust the pH value of the circulating slurry to 5 to 6 in case slaked lime becomes excessive.

  Next, the operation of the processing system 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, part of the combustion gas is extracted by the probe 6 and at the same time, the melting point of the chlorine compound is 700 ° C. or less by the cold air from the cooling fan 7. Quench quickly. Next, in the cyclone 10, the extracted gas G1 exhausted from the probe 6 is separated into the coarse powder D1 and the exhaust gas G2 containing the fine powder D2, and the coarse powder D1 is returned to the cement kiln system.

  On the other hand, although the exhaust gas G2 of 400-700 degreeC is introduce | transduced into the high temperature bag filter 11, since the high temperature bag filter 11 has heat resistance to 900 degreeC, the exhaust gas G2 supplied from the cyclone 10 is used as it is at temperature. Solid-gas separation is possible. Here, the reason why the exhaust gas G2 is solid-gas separated at a high temperature is to suppress the resynthesis of residual organic pollutants such as dioxins as described above.

  That is, dioxins have the property that they can be thermally decomposed if they are completely burned at a high temperature of 800 ° C. or higher, but then recombined when exposed to a temperature range of about 300 ° C. In addition, the fine powder D2 and chlorine in the exhaust gas G2 function as a catalyst for the resynthesis reaction and promote the generation of dioxins. Therefore, if the temperature of the exhaust gas G2 is lowered in the state where the fine powder D2 is mixed, organic pollutants There is a risk of greatly increasing the concentration of.

  Therefore, a high-temperature bag filter 11 is installed at the subsequent stage of the cyclone 10, and the exhaust gas G2 is solid-gas separated while being maintained at a temperature higher than the resynthesis temperature of dioxins. The resulting fine powder D2 and chlorine are separated from the exhaust gas G2. Thereby, resynthesis of dioxins can be suppressed and generation of organic pollutants can be suppressed.

  Next, the exhaust gas G3 of the high temperature bag filter 11 is attracted by the attracting fan 12 and supplied to the heat exchanger 13. On the other hand, the fine powder D2 collected by the high-temperature bag filter 11 is collected by a dust tank (not shown) or the like and supplied to the slurry circulation path 16b.

  Next, in the heat exchanger 13, the exhaust gas G3 of the high-temperature bag filter 11 and the clean gas (about 50 ° C.) G5 discharged from the wet dust collector 15 are heat-exchanged, and the exhaust gas G3 is cooled to 150 ° C. or less and simultaneously cleaned. The gas G5 is heated to 300 ° C. or higher. The heated clean gas G6 is attracted by the exhaust fan 14 and used as a heat source for drying cement raw material, sludge and the like.

  On the other hand, the cooled exhaust gas G4 is supplied to the scrubber 16 of the wet dust collector 15, and water is sprayed on the exhaust gas G4 to generate the slurry S. At this time, since the temperature of the exhaust gas G4 is 150 ° C. or lower, a large amount of water vapor is not generated even if the water and the exhaust gas G4 come into contact with each other. And the dust from the high temperature bag filter 11 is supplied and washed with water. At this time, as described above, the sulfur content in the exhaust gas G4 is removed, and gypsum is generated. When the slaked lime in the wet dust collector 15 is insufficient, the slaked lime slurry is replenished from the slaked lime slurry storage tank 21 to the slurry circulation path 16b through the pump 21a. To adjust the pH.

  The clean gas G5 after removing the residual dust is attracted by the exhaust fan 14 and flows into the pipe 13a in the heat exchanger 13, and as described above, heat for recovering heat from the exhaust gas G3 of the high-temperature bag filter 11 Used as a medium. On the other hand, the slurry S containing gypsum and dust is supplied to a subsequent treatment facility (not shown), and toxic substances such as heavy metals and gypsum are separated and recovered, and wastewater containing chlorine and the like is collected. Released after water treatment.

  As described above, according to the present embodiment, since the exhaust gas G3 of the high-temperature bag filter 11 is cooled to 150 ° C. or less and then introduced into the scrubber 16 of the wet dust collector 15, a large amount of water vapor is generated in the wet dust collector 15. Can be avoided. Therefore, a large amount of acidic water does not flow into the exhaust pipe 15a, and it is possible to prevent the exhaust fan 14 and the exhaust pipe 15a from being corroded.

  In addition, since the clean gas G5 discharged from the wet dust collector 15 is heated by the heat exchanger 13, even if a part of the slurry S scattered in the wet dust collector 15 flows into the exhaust pipe 15a, It is possible to prevent gypsum from adhering to the exhaust fan 14 and the exhaust pipe 15a, and to prevent acid moisture in the exhaust gas from the wet dust collector 15 from adhering to the exhaust fan 14 and the exhaust pipe. The occurrence rate can be reduced. Note that the clean gas G5 does not necessarily rise to 300 ° C. or higher because it is sufficient to prevent acidic moisture in the exhaust gas from the wet dust collector 15 from adhering to the exhaust fan 14 and the exhaust pipe and causing corrosion. It is not necessary to warm, and it is sufficient to raise the temperature above the saturated water vapor temperature.

  In the above embodiment, the heat exchanger 13 is provided between the high-temperature bag filter 11 and the wet dust collector 15. However, the cooling device for cooling the exhaust gas G3 of the high-temperature bag filter 11 and the clean gas of the wet dust collector 15 are provided. A temperature raising device for raising the temperature of G5 may be installed separately.

  Further, after separating the coarse powder D1 with the cyclone 10, the exhaust gas G2 containing the fine powder D2 is introduced into the wet dust collector 15, but the extracted gas G1 extracted by the probe 6 is directly supplied to the high-temperature bag filter 11 without providing the cyclone 10. It may be introduced. Further, it is preferable to install the high temperature bag filter 11 because less dust is introduced into the heat exchanger 13, but without the high temperature bag filter 11, the extraction gas extracted from the exhaust gas G2 from the cyclone 10 or the probe 6 is extracted. The gas G1 can also be introduced into the heat exchanger 13.

It is a flowchart which shows one Embodiment of the processing system of the cement kiln extraction gas concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cement kiln extraction gas processing system 2 Gas extraction part 3 Gas processing part 5 Cement kiln 6 Probe 7 Cooling fan 10 Cyclone 11 High temperature bag filter 12 Induction fan 13 Heat exchanger 13a Pipe line 14 Exhaust fan 15 Wet dust collector 15a Exhaust pipe 16 Scrubber 16a Pump 16b Slurry circulation path 17 Circulating liquid tank 18 Washing tower 20 Sulfuric acid storage tank 20a Pump 21 Slaked lime slurry storage tank 21a Pump G1 Extraction gas G2 to G4 Exhaust gas G5, G6 Clean gas D1 Coarse powder D2 Fine powder S Slurry

Claims (5)

An extraction device for extracting 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 lowermost cyclone;
A cooling device for cooling the extraction gas extracted by the extraction device;
A wet dust collector that wet-collects dust contained in the extraction gas cooled by the cooling device;
A temperature raising device for raising the temperature of the gas discharged from the wet dust collector ,
The cooling device and heated apparatus, cement kiln, wherein one heat exchanger der Rukoto of which heat exchange between the gas discharged from the wet dust collector and bled by bleed gas by the extraction device Extraction gas processing system. 2. The cement kiln extraction gas according to claim 1 , wherein the heat exchanger raises the gas discharged from the wet dust collector to a saturated water vapor temperature or higher by using heat recovered from the extraction gas. Processing system. A solid-gas separation device disposed between the extraction device and the cooling device and having heat resistance of at least 300 ° C .;
Processing system of the cement kiln extracted gas according to claim 1 or 2, characterized in that introduced into the bleed air has been extracted gas solid gas separator at 300 ° C. or higher 700 ° C. or less of the temperature by the bleed system. Comprising a classifier for separating coarse powder from the extraction gas extracted by the extraction device;
4. The cement kiln bleed gas processing system according to claim 1 , wherein exhaust gas containing fine powder discharged from the classifier is supplied to the cooling device or heat exchanger. A part of the combustion gas is extracted from the kiln exhaust gas flow path from the kiln bottom of the cement kiln to the bottom cyclone,
After the extracted gas extracted from the extracted gas is cooled, wet dust collection is performed on dust contained in the extracted gas;
By elevating the temperature of the exhaust gas after the removal of the dust by the wet type dust collector,
The method for treating a cement kiln extraction gas, wherein the cooling and the temperature increase are simultaneously performed by heat exchange between the extraction gas and the exhaust gas after the dust is removed .

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