JP2009035450A - System and method for treating cement kiln extraction gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To remove sulfur contained in a cement kiln extraction gas, and to efficiently remove persistent organic pollutants contained therein. <P>SOLUTION: A system 1 for treating a cement kiln extraction gas comprises a probe 6 to extract part of a combustion gas from a kiln exhaust gas channel from the bottom of a cement kiln 5 to a lowermost stage cyclone, a cyclone 10 to separate the extraction gas extracted in the probe 6 to a coarse powder D, a fine powder, and a gas G2, a sprayer 11 to add activated carbon for adsorbing persistent organic pollutants to the exhaust gas G2 from the cyclone 10, and a wet dust collector 12 to collect the dust of the exhaust gas G2 in a wet state to which activated carbon is added. Persistent organic pollutants may be dissolved in a solvent, and then it may be separated from the extraction gas in a circulation fluid tank 14 of a wet dust collector 12. Fractionation treatment can be simplified by equipping the latter part of the wet dust collector 12 with a fractionation part 4 to fractionate a dust slurry S1 discharged from the wet dust collector 12 into a substance containing sulfur and a substance containing persistent organic pollutants. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a processing system and a processing method for a cement kiln extraction gas, 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 obtain chlorine and sulfur components. And a processing system for removing residual organic pollutants and the like.

  In the past, focusing on chlorine being a particular problem among chlorine, sulfur, alkali, etc. that cause problems such as blockage of preheaters in cement production facilities, from the kiln bottom of the cement kiln to the bottom cyclone Chlorine bypass equipment is used to extract chlorine from a part of the kiln exhaust gas flow path and remove chlorine. In this chlorine bypass facility, after extracting the combustion gas, dust containing chlorine is separated from the extracted combustion gas. However, the extracted gas after separating the dust contains a considerable amount of sulfur oxide in a gaseous state. Therefore, the chlorine bypass exhaust cannot be released to the atmosphere as it is.

Therefore, as described in Patent Document 1, a desulfurization method for desulfurizing sulfur content in the extracted gas by wet-collecting the extracted gas extracted from the vicinity of the inlet hood of the cement kiln with a wet dust collector has been proposed. Yes. In this method, quick lime (CaO) contained in fine dust in the extraction gas is reacted with water in the wet dust collector to generate slaked lime (Ca (OH) ₂ ), and the slaked lime and the extraction gas Is reacted with sulfur dioxide (SO ₂ ) to produce gypsum. Thereafter, the generated gypsum is recovered and discharged out of the cement kiln system, thereby removing the sulfur content in the extracted gas.
JP 2004-002143 A

  However, according to the desulfurization method described in Patent Document 1, the sulfur content in the extracted gas can be removed, but as the amount of waste brought into the cement manufacturing plant increases in the future, the combustion exhaust gas from the cement kiln May contain residual organic pollutants such as dioxins (PCDD, PCDF, co-PCB), polychlorinated biphenyls (PCBs), etc., which may be contained in the extracted gas due to the use of a desulfurizing agent or water washing treatment. If the sulfur content is removed, it will be mixed into the waste material and waste liquid after the desulfurization treatment, and as a result, it will be difficult to treat the waste material or the like, and a treatment facility will be required.

  Therefore, the present invention has been made in view of the above-described problems in the conventional technology, and can remove sulfur in the extracted gas and efficiently remove residual organic pollutants. It is an object of the present invention to provide a processing system and a processing method for a simple cement kiln bleed gas.

  In order to achieve the above object, the present invention is a cement kiln extraction gas processing system, and an extraction means for extracting a part of combustion gas from a kiln exhaust gas passage from the bottom of the cement kiln to the lowermost cyclone. And an addition means for adding a treatment agent for treating residual organic pollutants to the extraction gas extracted by the extraction means; and wet dust collection for collecting dust from the extraction gas to which the treatment agent is added. Means. The persistent organic pollutant refers to dioxins (PCDD, PCDF, co-PCB), polychlorinated biphenyls (PCBs), and the like.

  And according to this invention, in order to wet-collect the extraction gas which added the processing agent for processing a residual organic pollutant with respect to the extraction gas extracted by the extraction means, and added the processing agent after that The sulfur content in the extraction gas can be extracted as gypsum, and at the same time, residual organic pollutants in the extraction gas can be removed. In addition, when a wet dust collector has been used as a facility for removing sulfur, the dust collector can be used, so that an increase in facility cost can be minimized. Furthermore, before the dust in the bleed gas is slurried, the residual organic pollutant and the treatment agent are brought into contact with each other, so that the contact between them can be improved and the residual organic pollutant can be efficiently removed. Is possible.

  In the cement kiln bleed gas processing system, the adding means may add an adsorbent that adsorbs the residual organic pollutant as a processing agent for processing the residual organic pollutant. According to this configuration, the residual organic pollutant is adsorbed on the adsorbent, and then the adsorbent that has adsorbed the residual organic pollutant is separated from the extracted gas by the wet dust collecting means. Organic contaminants can be easily removed.

  In the cement kiln bleed gas processing system, the adding means can add a solvent that dissolves the residual organic pollutant as a processing agent for processing the residual organic pollutant. Since the liquid in which the residual organic pollutants are dissolved has a large droplet diameter, for example, it falls freely in the circulating liquid phase constituting the wet dust collector, and most of the liquid is separated from the extracted gas passing through the liquid tank. In addition, the portion where the droplet diameter is small and did not fall freely in the circulating liquid phase is separated from the extraction gas by a mist separation device (mist separator, mist catcher, demister), etc. in the subsequent stage, Persistent organic contaminants can be easily removed.

  In the cement kiln bleed gas processing system, the adding means may be provided with a spray means for spraying the processing agent on the bleed gas extracted by the bleed means. As a result, the processing agent can be uniformly added to the entire bleed gas, and the removal efficiency of residual organic pollutants can be improved.

  In the cement kiln bleed gas processing system, there can be provided a separating means for separating the dust collected by the wet dust collecting means into a substance containing sulfur and a substance containing residual organic pollutants. As a result, sulfur and residual organic pollutants can be separated and recovered, and harmful substances can be recovered in an easy-to-process state.

  Further, the present invention provides a method for treating a cement kiln bleed gas, wherein a part of the combustion gas is extracted from the kiln exhaust gas passage from the bottom of the cement kiln to the bottom cyclone, and the extracted bleed gas is The present invention is characterized in that a treatment agent for treating residual organic pollutants is added, and the dust of the extracted gas to which the treatment agent is added is wet-collected. According to the present invention, similar to the above-described invention, it is possible to remove the sulfur content in the extracted gas and efficiently remove the residual organic pollutant.

  In the cement kiln extraction gas treatment method, as a treatment agent for treating the residual organic pollutants, activated carbon, activated coke, coal, coal ash, activated carbon, blast furnace ash, and ash containing unburned carbon One or more selected can be added to adsorb residual organic pollutants.

  In the method for treating a cement kiln bleed gas, as a treating agent for treating the residual organic pollutant, an organic solvent that is hardly soluble in water (aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, ethers) , Esters, and ketones), and one or more selected from the group consisting of octanol, dichloromethane, hexane, toluene, and xylene can be added.

  In the processing method of the cement kiln extraction gas, the processing agent can be sprayed on the extracted extraction gas, whereby the processing agent can be uniformly added to the entire extraction gas, and the residual organic It becomes possible to improve the removal efficiency of pollutants.

  In the method for treating a cement kiln bleed gas, the wet dust-collected dust can be separated into a substance containing sulfur and a substance containing persistent organic pollutant, and the sulfur and the residual organic pollutant are separated. By separating and collecting, it becomes possible to collect harmful substances in a state that is easy to process.

  As described above, according to the present invention, it is possible to remove the sulfur content in the extracted gas and efficiently remove residual organic pollutants.

  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. This processing system 1 is roughly divided into a gas extraction unit 2, a gas processing unit 3, and a separation processing unit 4. Composed.

  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 D contained in the extraction gas G1. It consists of cyclone 10 etc. as a classifier.

  The gas processing unit 3 is a facility for removing harmful substances in the extracted gas. The gas processing unit 3 includes a sprayer 11, a wet dust collector 12 that wet-collects dust in the exhaust gas G2 discharged from the cyclone 10, and an exhaust fan for discharging the exhaust gas G3 from the wet dust collector 12 to the outside of the system. 18 etc.

  The sprayer 11 removes residual organic pollutants such as dioxins (PCDD, PCDF, co-PCB) and polychlorinated biphenyls (PCBs) from the exhaust gas G2 from which the coarse dust D has been removed ( Hereinafter, it is provided for appropriately adding a “hazardous substance removing agent”). The sprayer 11 is disposed between the cyclone 10 and the wet dust collector 12, and the spray port is connected to a pipe line 10 a extending from the exhaust port of the cyclone 10.

  As the harmful substance removing agent to be sprayed, activated carbon can be used, and when activated carbon is sprayed on the exhaust gas G2, the activated carbon acts as an adsorbent and adsorbs and removes residual organic pollutants present in the exhaust gas G2. be able to. In addition to activated carbon, activated coke, coal, coal ash, blast furnace ash, ash containing unburned carbon, and the like can be used as the harmful substance removing agent.

  The wet dust collector 12 is provided for collecting dust in the exhaust gas G2 and removing chlorine, sulfur and residual organic pollutants from the exhaust gas G2. The wet dust collector 12 includes a mixing 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 mixing scrubber 13 and the circulating liquid tank 14. . In addition, a sulfuric acid storage tank 16, a pump 16a, a slaked lime slurry storage tank 17, and a pump 17a are arranged to supply sulfuric acid for adjusting the pH of the circulating slurry to the circulating liquid tank 14.

In the dust slurry S1 generated by the wet dust collector 12, there is slaked lime (Ca (OH) ₂ ) generated by the reaction of quick lime (CaO) in fine powder with water, and therefore, the sulfur content present in the exhaust gas G2. (SO ₂ ) 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 G2 is decomposed and gypsum (CaSO ₄ .2H ₂ O) is generated. The gypsum thus generated is supplied to the separation processing unit 4 as the dust slurry S1 together with the activated carbon that has adsorbed the residual organic contaminants.

  The separation processing unit 4 is a facility for separating the dust in the dust liary S1 into gypsum and activated carbon. This fractionation processing unit 4 supplies a slurry slurry 22 to which the dust slurry S1 is supplied and agitates, and a surface reformer that applies a shearing force to the slurry S2 discharged from the slurry tank 22 to modify the surface of the activated carbon. 27, the adjustment tank 23 for generating bubbles by adding a foaming agent to the slurry S2, the flotation device 24 for attaching activated carbon to the bubbles and floating to separate them, and the tailing from the flotation device 24 are separated into solid and liquid Thus, a cake is formed, and a solid-liquid separator 25 that collects gypsum and a filter press 26 that collects the floss from the flotation machine 24 by solid-liquid separation and collects activated carbon are included. Note that gypsum can also be collected on the floss side of the flotation machine 24 in relation to the specific gravity of the suspension. Alternatively, gypsum crystals may be grown and physically classified and recovered.

  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, a part of the combustion gas is extracted by the probe 6 and at the same time, the melting point of the chlorine compound is 600 to 700 by the cold air from the cooling fan 7. Rapidly cool to below ℃. Next, in the cyclone 10, the extracted gas G1 exhausted from the probe 6 is separated into coarse powder D and gas G2 containing fine powder, and the coarse powder D is returned to the cement kiln system.

  On the other hand, the exhaust gas G2 from which the coarse powder D has been removed is discharged to the pipeline 10a, and the sprayer 11 sprays activated carbon as a harmful substance removing agent on the exhaust gas G2 in the pipeline 10a. Subsequently, the exhaust gas G2 sprayed with activated carbon is supplied to the mixing scrubber 13 of the wet dust collector 12, and the sulfur content in the exhaust gas G2 is brought into contact with the slurry while circulating the slurry between the mixing scrubber 13 and the circulating liquid tank 14. To produce gypsum. And the produced gypsum and the activated carbon which adsorbed the residual organic pollutant are collected and supplied to the slurry tank 22 as the dust slurry S1. At the same time, the exhaust gas discharged from the circulating liquid tank 14 is cleaned in the cleaning tower 15 to remove harmful substances remaining in the exhaust gas. The exhaust gas G3 from the cleaning tower 15 may be released to the atmosphere via the exhaust fan 18 or may be returned to the cement process for heat recovery.

  In order to prevent scale troubles in the flow path of the circulating slurry supplied to the mixing scrubber 13, it is preferable to adjust the pH of the circulating fluid in the circulating fluid tank 14 to around 4-6. Therefore, when the pH of the circulating fluid in the circulating fluid tank 14 increases too much, the classification point of the cyclone 10 is changed to reduce the CaO concentration in the fine powder, or the sulfuric acid storage tank 16 is used as necessary. It is preferable to add the sulfuric acid to be stored to the circulating liquid tank 14.

  Next, after the slurry S1 from the circulating liquid tank 14 is stirred in the slurry tank 22, a shearing force is applied to the slurry S1 discharged from the slurry tank 22 by the surface reformer 27 to modify the surface of the activated carbon. I do. This surface modification is performed when activated carbon is in a poor separation state, and can improve flotation floatability by surface modification. Next, in the adjustment tank 23, the slurry S2 and the foaming agent Mix. Then, the slurry S2 mixed with the foaming agent and the air are supplied to the flotation machine 24, and in the flotation machine 24, bubbles are generated, and activated carbon is attached to the bubbles, and the activated carbon is attached to the air bubbles. Remove.

  In addition, when activated carbon is used, sulfur is adsorbed in addition to residual pollutants, but the sulfur is dissolved on the aqueous solution side in the mixing scrubber 13 and the circulating liquid tank 14, and is contained in G2 (fine powder + gas). It is recovered as gypsum by reaction with calcium in the fine powder and slaked lime replenished as a slurry from the slaked lime slurry storage tank 17. In addition, when the slaked lime slurry cannot be charged, limestone, slaked lime, quicklime, cement raw material, calcined cement raw material, or the like can be added to the circulating liquid tank 14 or the slurry tank 22 as a calcium component. In the case where the calcium content is not adjusted, the portion where the residual organic contaminants are adhered and the portion deposited as gypsum can be recovered, and the sulfur content in the unreacted liquid can be moved to the tank 28 as it is.

  Next, in the filter press 26, the floss from the flotation machine 24 is subjected to solid-liquid separation, and the activated carbon is recovered. The recovered activated carbon is burned together with the fuel in the cement kiln 5 so that the residual organic pollutants contained in the activated carbon can be completely decomposed.

  At the same time, in the solid-liquid separator 25, the tailing from the flotation device 24 is solid-liquid separated to produce a cake, and then the cake is dried by a dryer (not shown) to collect the gypsum. The collected gypsum can be put into a cement mill or the like, pulverized with a clinker, and used as a part of cement.

  Waste liquid from the solid-liquid separator 25 and the filter press 26 is stored in a tank 28 and discharged after treatment of waste water or added to a cement grinding mill system.

  As described above, according to the present embodiment, the harmful substance removing agent for adsorbing the residual organic pollutant is added to the extracted gas extracted by the probe 6, and then the harmful substance removing agent is added. Since the extraction gas is subjected to wet dust collection, the sulfur content in the extraction gas is extracted as gypsum, and at the same time, residual organic pollutants in the extraction gas can be adsorbed and removed by activated carbon. If a wet dust collector has been used as a facility for removing chlorine and sulfur, the dust collector is used as a device for separating activated carbon adsorbing residual organic pollutants from the extracted gas. Therefore, an increase in equipment cost can be minimized. Further, a harmful substance removing agent is added in the front stage of the wet dust collector 12, and before the dust in the extracted gas is slurried, the residual organic pollutant and the harmful substance removing agent are brought into contact with each other. The residual organic pollutant can be efficiently removed.

  In the above embodiment, an adsorbent for adsorbing the residual organic pollutant is added to the extracted gas extracted by the probe 6, but the residual organic pollutant is dissolved instead of the adsorbent. A solvent may be added. The solvent may be an organic solvent (aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, ethers, esters, ketones) that is sparingly soluble in water, such as octanol, dichloromethane, hexane, toluene, xylene. Also by this method, the residual organic pollutants in the extracted gas can be efficiently removed. In this case, the solvent is added from the mixing scrubber 13 or the circulating liquid tank 14 and reacted (dissolved) with the residual organic contaminants by the mixing scrubber 13. The solvent is contained in the drainage liquid of either the solid-liquid separator 25 or the filter press 26 depending on whether the solvent is lighter or heavier than water. The waste liquid is stored in the tank 28, and only the solvent part is separated by specific gravity separation and burned as fuel. The drainage liquid from which the solvent portion has been separated is returned to the slurry tank 22, discharged after treatment with waste water, or added to the cement grinding mill system.

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 4 Separation processing part 5 Cement kiln 6 Probe 7 Cooling fan 10 Cyclone 10a Pipe line 11 Sprayer 12 Wet dust collector 13 Mixing scrubber 14 Circulating liquid tank 14a Pump 15 Cleaning Tower 16 Sulfuric acid storage tank 16a Pump 17 Slaked lime slurry storage tank 17a Pump 22 Slurry tank 23 Adjustment tank 24 Flotation machine 25 Solid-liquid separator 26 Filter press 27 Surface reformer 28 Tank

Claims (10)

Extraction means for 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;
An adding means for adding a processing agent for treating residual organic pollutants to the extracted gas extracted by the extracting means;
A cement kiln extraction gas processing system, comprising: wet dust collection means for collecting dust of extraction gas to which the treatment agent is added.   The processing of the cement kiln extraction gas according to claim 1, wherein the adding means adds an adsorbent that adsorbs the residual organic pollutant as a processing agent for processing the residual organic pollutant. system.   The cement kiln extraction gas processing system according to claim 1, wherein the adding means adds a solvent that dissolves the residual organic pollutant as a processing agent for processing the residual organic pollutant. .   The cement kiln bleed gas processing system according to claim 1 or 2, wherein the adding means includes spray means for spraying the processing agent on the bleed gas extracted by the bleed means.   5. The apparatus according to claim 1, further comprising a separation unit that separates the dust collected by the wet dust collection unit into a substance containing sulfur and a substance containing a residual organic pollutant. Cement kiln bleed gas treatment system. 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,
A processing agent for treating residual organic pollutants is added to the extracted gas extracted,
A method for treating a cement kiln bleed gas, wherein the dust of the bleed gas to which the treating agent is added is wet-collected.   One or more selected from the group consisting of activated carbon, activated coke, coal, coal ash, activated carbon, blast furnace ash and ash containing unburned carbon is added as a treating agent for treating the residual organic pollutant. The processing method of the cement kiln bleed gas of Claim 6.   The cement kiln bleed gas according to claim 6, wherein at least one selected from the group consisting of octanol, dichloromethane, hexane, toluene and xylene is added as a treating agent for treating the residual organic pollutant. Processing method.   The method for treating a cement kiln bleed gas according to claim 6 or 7, wherein the treatment agent is sprayed on the extracted bleed gas.   10. The method for treating a cement kiln extraction gas according to any one of 6 to 9, wherein the wet dust collected dust is separated into a substance containing sulfur and a substance containing persistent organic pollutants.

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