JP5348792B2 - Combustion gas extraction probe and operating method thereof - Google Patents

Description

  The present invention relates to a combustion gas extraction probe for extracting a part of combustion gas from a cement kiln exhaust gas flow path and a method for operating the same.

  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, for example, as described in Patent Document 1, since chlorine is unevenly distributed on the fine powder side of the dust generated by cooling the extracted exhaust gas, the dust is separated into coarse powder and fine powder by a classifier. Separated, the coarse powder was returned to the cement kiln system, and the fine powder (chlorine bypass dust) containing potassium chloride and the like was collected and added to the cement grinding mill system.

International Publication No. 97/21638 Pamphlet

  However, in the chlorine bypass system described in the above patent document, although chlorine contained in the cement kiln exhaust gas can be removed, since POPs such as dioxin exist in the gas discharged from the chlorine bypass system, these It was necessary to take measures such as providing a catalyst tower to treat the wastewater and detoxifying it downstream.

  Accordingly, the present invention has been made in view of the above-described problems in the prior art, and suppresses the generation of POPs such as dioxins in the chlorine bypass system, thereby minimizing the equipment cost for detoxification treatment. An object of the present invention is to provide a method of operating a combustion gas extraction probe that can be suppressed to a low level.

  In order to achieve the above object, the present inventors have conducted extensive research. As a result, in the conventional chlorine bypass system, when the combustion gas is extracted while cooling the combustion gas from the cement kiln exhaust gas passage by the extraction probe, this cooling is performed. Oxygen contained in these gases and heavy metals contained in cement kiln exhaust gas cause oxy-chlorination reaction to generate POPs such as dioxins because they use air or exhaust with odor. The present invention has been found and the present invention has been made. The oxychlorination reaction is also called an oxidative chlorination reaction, and is a reaction in which heavy metal carbon compounds are chlorinated to generate POPs such as dioxins in the presence of oxygen or air.

  The present invention has been made on the basis of such knowledge, and is a method for operating a combustion gas extraction probe, in which a part of combustion gas is extracted from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone. A combustion gas extraction probe that performs extraction while cooling is characterized by using a gas having an oxygen concentration of 5% or less for the cooling.

  According to the present invention, a part of the combustion gas is extracted from the cement kiln exhaust gas flow path, and the oxygen concentration is 5% or less for cooling the extracted gas, thereby suppressing the oxychlorination reaction. And the generation of POPs such as dioxins due to this reaction can be suppressed.

  In the operation method of the combustion gas extraction probe, the gas used for the cooling can be the combustion exhaust gas of the cement kiln, and further the exhaust gas of a chlorine bypass system attached to the cement kiln.

  In the method for operating the combustion gas extraction probe, nitrogen gas from an oxygen enricher or nitrogen gas from a nitrogen gas production apparatus can be used as the gas used for cooling. In particular, when an oxygen enrichment operation of a cement kiln is performed, nitrogen generated at that time can be used, which is preferable. It is also possible to use cement kiln exhaust gas and adjust the oxygen concentration by adding nitrogen gas.

  In the operation method of the combustion gas extraction probe, superheated steam can be used as the gas used for the cooling.

  Furthermore, in the operation method of the combustion gas extraction probe, the temperature of the combustion gas extracted by the combustion gas extraction probe is 1300 ° C. or lower and 700 ° C. or higher, and the temperature of the combustion gas after cooling is 700 ° C. or lower and 150 ° C. or higher. can do.

  The present invention also relates to a combustion gas bleed probe that bleeds while cooling a part of the combustion gas from the kiln exhaust gas passage from the bottom of the kiln of the cement kiln to the lowermost cyclone, and has an oxygen concentration of 5% or less. A gas is introduced for the cooling. According to the present invention, the oxychlorination reaction can be suppressed and the generation of POPs such as dioxin due to this reaction can be suppressed as in the above-described invention.

  As described above, according to the present invention, it is possible to provide a combustion gas extraction probe capable of suppressing the generation of POPs such as dioxins and an operation method thereof in a chlorine bypass system.

It is a flowchart for demonstrating 1st Embodiment of the operating method of the combustion gas extraction probe concerning this invention. It is a flowchart for demonstrating 2nd Embodiment of the operating method of the combustion gas extraction probe concerning this invention.

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

  FIG. 1 shows a cement kiln exhaust gas treatment apparatus for explaining a first embodiment of a method for operating a combustion gas extraction probe according to the present invention. While extracting part of the kiln combustion gas, the probe 3 that cools the extraction gas G1 with nitrogen gas introduced from the cooling fan 4, the classifier 5 that removes the coarse powder D1 contained in the extraction gas G1, and the classification A high temperature bag filter 6 for solid-gas separation of fine powder D2 and exhaust gas G2 from the machine 5, a dust tank 7 for storing the fine powder D2 collected by the high temperature bag filter 6, and an exhaust gas G3 from the high temperature bag filter 6 into a cement kiln system It consists of an exhaust fan 8 for returning or releasing to the atmosphere. Since these devices have the same configuration as that installed in a general chlorine bypass system, detailed description of each device will be omitted.

  Next, the operation of the cement kiln exhaust gas treatment apparatus 1 having the above configuration will be described with reference to FIG.

  During operation of the cement kiln 2, a part of the combustion gas is extracted from the kiln bottom of the cement kiln 2 with the probe 3, and at the same time, the extraction gas G1 is set to 150 ° C. to 700 ° C. with nitrogen gas introduced from the cooling fan 4. Cooling. The point of using this nitrogen gas is a characteristic part of the present invention, and by using a cooling gas that does not contain oxygen, an oxychlorination reaction that may occur with the extraction gas G1 is suppressed, Generation of POPs such as dioxins can be suppressed. Further, in order to suppress the resynthesis of POPs skeleton materials such as biphenyl, dioxin, furan and the like, it is preferable to cool to 150 ° C. to 400 ° C.

  As the nitrogen gas, nitrogen gas generated by an oxygen enrichment apparatus using an oxygen-enriched membrane, a hollow fiber membrane, zeolite, or the like, or nitrogen gas generated by a nitrogen gas production apparatus can be used. In particular, when an oxygen enrichment operation is performed with a cement kiln 2 equipped with an oxygen enricher, the nitrogen gas generated at that time can be used as the cooling gas.

  Subsequently, the classifier 5 separates the extracted gas G1 exhausted from the probe 3 into the coarse powder D1 and the exhaust gas G2 containing the fine powder D2, and returns the coarse powder D1 to the cement kiln system.

  On the other hand, the exhaust gas G2 containing the fine powder D2 at 150 ° C. to 700 ° C. from which the coarse powder D1 has been removed is introduced into the high-temperature bag filter 6 to collect the fine powder D2. The recovered fine powder D2 is stored in the dust tank 7 as chlorine bypass dust, and then used in a cement crushing process, or washed with water and then used as a cement raw material.

  Next, the exhaust gas G3 of the high-temperature bag filter 6 from which the fine powder D2 has been removed is returned to the cement kiln system by the exhaust fan 8 or released to the atmosphere. Here, the dust collector that removes the fine powder D2 is the high-temperature bag filter 6, but an indirect cooler and a heat recovery system that do not increase oxygen are provided between the probe 3 and the dust collector, thereby applying an applicable gas temperature using a woven fabric or a non-woven fabric. A low bug filter can also be used. Further, it is possible to cool the cooling gas not containing oxygen by dividing it into a plurality of stages, for example, a part of the probe 3 and an outlet part of the probe 3.

  Next, a second embodiment of the operation method of the combustion gas extraction probe according to the present invention will be described with reference to FIG.

  The cement kiln exhaust gas treatment device 21 shown in FIG. 2 cools the extracted gas G21 using the exhaust gas G23 from the cleaning tower 28 while extracting a part of the cement kiln combustion gas from the kiln bottom of the cement kiln 22. The probe 23, the classifier 25 for removing the coarse powder D21 contained in the extracted gas G21, the wet scrubber 26 for wet-collecting the fine powder D22 and the exhaust gas G22 from the classifier 25, and the slurry S1 in the wet scrubber 26 A circulating liquid tank 27 for circulation, a cleaning tower 28 to which cleaning water is supplied, an exhaust fan 29 for returning the exhaust gas G23 from the cleaning tower 28 to the probe 23, and a collection exhausted from the circulating liquid tank 27 The dust dust slurry S2 is solid / liquid separated to obtain a gypsum GP and salt water SW, and the like. Since each of the above devices has the same configuration as that installed in a general chlorine bypass system, detailed description of each device will be omitted.

  Next, the operation of the cement kiln exhaust gas treatment apparatus 21 having the above-described configuration will be described with reference to FIG.

  During operation of the cement kiln 22, a part of the combustion gas is extracted by the probe 23 from the bottom of the kiln 22 of the cement kiln 22, and at the same time, the extracted gas G 21 is 150 by the exhaust gas G 23 from the cleaning tower 28 introduced by the exhaust fan 29. Cool to from 0C to 700C. The point of using the exhaust gas G23 is a characteristic part of the present invention. By using the exhaust gas G23 having an oxygen concentration of 5% or less as a cooling gas, the oxychlorination reaction with the extraction gas G21 is suppressed. , Generation of POPs such as dioxins can be suppressed. Further, when the oxygen concentration of the exhaust gas G23 is higher than that, the oxygen concentration can be adjusted by adding nitrogen gas or the like. In this adjustment, the amount of nitrogen gas or the like added by the oxygen concentration meter is adjusted. It can also be managed and controlled.

  Next, in the classifier 25, the extracted gas G21 exhausted from the probe 23 is separated into the coarse powder D21 and the exhaust gas G22 containing the fine powder D22, and the coarse powder D21 is returned to the cement kiln system.

  On the other hand, the exhaust gas G22 including the fine powder D22 of 150 ° C. to 700 ° C. from which the coarse powder D21 has been removed is cooled in the wet scrubber 26 by the water content of the slurry S1 supplied from the circulating liquid tank 27. Further, fine powder D22 having a high chlorine content is collected by wet scrubber 26, and dust collection slurry S2 is separated into gypsum GP and salt water SW containing KCl by solid-liquid separator 30, and gypsum GP is recovered. At the same time, the separated salt water SW is added to the cement pulverization step, discharged into sewage or the ocean after water treatment, or treated by salt recovery.

  Next, a part of the exhaust gas G23 of the cleaning tower 28 from which the fine powder D22 has been removed is introduced into the probe 23 by the exhaust fan 29 and used as the cooling gas, and the remaining exhaust gas G24 is returned to the cement kiln system, or the atmosphere To release.

  In the above embodiment, the nitrogen gas or the exhaust gas G23 of the cleaning tower 28 is used as a cooling gas in the probes 3 and 23. In addition, in the dry chlorine bypass system, a heat exchanger and a bag filter are used. Extraction gas (exhaust gas from the chlorine bypass system) having a reduced temperature through the combustion kiln exhaust gas, superheated steam, nitrogen of the cement kilns 2 and 22 having a lowered temperature through a preheater or the like without being introduced into the chlorine bypass system Gases with an oxygen concentration of 5% or less, such as inert gases other than gas, can be used. If this is advantageous from an economic standpoint, adjust these gases with nitrogen gas or the like so that the oxygen concentration is 5% or less. It can also be used. Furthermore, superheated steam can generate hydroxyl radicals that decompose POPs by optimizing conditions such as ozone, hydrogen peroxide, and ultraviolet rays, and can further enhance the effect of reducing POPs.

  Moreover, in the said embodiment, although the case where a part of combustion gas was extracted with the probes 3 and 23 from the kiln bottom of the cement kilns 2 and 22 was demonstrated, in addition to kiln bottom, from kiln bottom to the lowest cyclone. A part of the combustion gas can be extracted from the kiln exhaust gas flow path.

  Further, the classifiers 5 and 25 are arranged between the probes 3 and 23 and the high-temperature bag filter 6 or the wet scrubber 26, but without the classifiers 5 and 25, the extraction gas G1 from the probes 3 and 23, G21 may be directly introduced into the high temperature bag filter 6 or the wet scrubber 26.

  On the other hand, an indirect cooler or a heat recovery system that does not increase oxygen can be provided between the probes 3 and 23 and the dust collector, whereby a dust collector other than the high-temperature bag filter 6 and the wet scrubber 26 can be used. Further, the cooling gas not containing oxygen can be cooled in a plurality of stages, for example, the parts of the probes 3 and 23, the outlet parts of the probes 3 and 23, and the like.

DESCRIPTION OF SYMBOLS 1 Cement kiln exhaust gas processing device 2 Cement kiln 3 Probe 4 Cooling fan 5 Classifier 6 High temperature bag filter 7 Dust tank 8 Exhaust fan 21 Cement kiln exhaust gas processing device 22 Cement kiln 23 Probe 25 Classifier 26 Wet scrubber 27 Circulating fluid tank 28 Washing tower 29 Exhaust fan 30 Solid-liquid separator D1 Coarse powder D2 Fine powder D21 Coarse powder D22 Fine powder G1 Extraction gas G2 to G3 Exhaust gas G21 Extraction gas G22 to G24 Exhaust gas GP Gypsum SW Salt water

Claims (7)

  In a combustion gas extraction probe that extracts air while cooling a part of the combustion gas from the kiln exhaust gas flow path from the kiln bottom of the cement kiln to the lowermost cyclone, a gas having an oxygen concentration of 5% or less is used for the cooling. A method of operating a combustion gas bleeder probe.   The method for operating a combustion gas extraction probe according to claim 1, wherein the gas used for cooling is combustion exhaust gas of the cement kiln.   The method for operating a combustion gas extraction probe according to claim 2, wherein the gas used for cooling is an exhaust gas of a chlorine bypass system attached to the cement kiln.   2. The method of operating a combustion gas extraction probe according to claim 1, wherein the gas used for cooling is nitrogen gas from an oxygen enricher or nitrogen gas from a nitrogen gas production device.   The method for operating a combustion gas extraction probe according to claim 1, wherein the gas used for cooling is superheated steam.   6. The temperature of the combustion gas extracted by the combustion gas extraction probe is 1300 ° C. or lower and 700 ° C. or higher, and the temperature of the combustion gas after cooling is 700 ° C. or lower and 150 ° C. or higher. A method for operating the combustion gas extraction probe according to claim 1.   A combustion gas extraction probe that extracts air 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, and a gas having an oxygen concentration of 5% or less is used for the cooling. A combustion gas bleed probe, characterized by being introduced.

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