WO2009110356A1

WO2009110356A1 - System and method for treating bleed gas from cement kiln

Info

Publication number: WO2009110356A1
Application number: PCT/JP2009/053323
Authority: WO
Inventors: 淳一寺崎; 紳一郎齋藤
Original assignee: 太平洋セメント株式会社
Priority date: 2008-03-07
Filing date: 2009-02-25
Publication date: 2009-09-11
Also published as: TW200940158A; CN103933836A; KR20110000620A; JPWO2009110356A1; CN101959824A

Abstract

A bleed gas from a cement kiln is purified with a catalyst by efficiently removing organic pollutants contained in the bleed gas, while minimizing the poisoning of the catalyst by an acidic gas. A system (1) for treating a bleed gas from a cement kiln is provided which includes: a probe (5) which bleeds a kiln discharge gas passage, which extends from the bottom of a cement kiln (4) to a lowermost-stage cyclone, of part of a combustion gas; a first heat exchanger (11) which recovers heat while cooling the bleed gas (G2) taken out by the probe (5); a bag filter (12) which separates dust from the bleed gas (G2) cooled by the first heat exchanger (11); a second heat exchanger (17) by which the bleed gas (G3) from which dust has been separated is heated with the heat recovered by the first heat exchanger (11); and a catalyst device (18) which decomposes organic pollutants contained in the bleed gas (G4) heated by the second heat exchanger (17) and removes the pollutants therefrom.

Description

Cement kiln extraction gas processing system and processing method

The present invention relates to a processing system and processing method for a cement kiln extraction gas, and in particular, removes organic pollutants contained in the extraction gas extracted from the kiln exhaust gas flow path from the bottom of the cement kiln to the bottom cyclone. Related to a processing system and the like.

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 combustion gas, the dust is separated into coarse powder and fine powder by a classifier. In addition to returning the coarse powder to the cement kiln system, fine powder (chlorine bypass dust) containing the separated potassium chloride and the like was recovered.

As described above, in the chlorine bypass system, dust containing chlorine is separated and recovered from the extracted combustion gas. However, a considerable amount of sulfur oxide (SOx) is gas in the extracted gas after separating the dust. Therefore, the exhaust from the chlorine bypass cannot be released to the atmosphere as it is. Chlorine bypass exhaust may also contain persistent organic pollutants (POPs) such as dioxins (PCDD, PCDF, co-PCB), polychlorinated biphenyls (PCBs), and volatile organic pollutants (VOC). There is a need to deal with them appropriately.

International Publication No. 97/21638 Pamphlet

As one of the methods for removing organic pollutants such as POPs and VOCs, a method of decomposing using a catalyst is known. Even in a chlorine bypass system, by providing a catalyst device on the exhaust path, chlorine bypass exhaust is provided. It is conceivable to remove organic pollutants from water.

However, a large amount of SOx-derived acidic gas exists in the chlorine bypass exhaust, which poisons the catalyst and lowers the catalytic activity. Therefore, it is difficult to put it into practical use simply by installing the catalyst device on the exhaust passage. It is. In addition, if the recycling of wastes into cement raw materials or fuels continues to increase in the future, there is concern about an increase in the contents of POPs and VOC components in the chlorine bypass exhaust. For this reason, in the future, it is expected that catalyst deactivation due to acidic gas will be suppressed, and more efficient removal of organic pollutants will be required.

Therefore, the present invention has been made in view of the above problems in the prior art, and minimizes poisoning of the catalyst by acid gas when purifying the cement kiln extraction gas using a catalyst device. Meanwhile, an object is to efficiently remove organic pollutants contained in the extracted gas.

In order to solve the above-mentioned problem, 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. A first heat exchanger that recovers heat while cooling the extraction gas extracted by the extraction unit, a separation unit that separates dust from the extraction gas cooled by the first heat exchanger, and the first A second heat exchanger that heats the extraction gas from which the dust has been separated using heat recovered by the heat exchanger, and a catalyst device that removes organic pollutants from the extraction gas heated by the second heat exchanger It is characterized by providing. Organic pollutants refer to residual organic pollutants (POPs) such as dioxins (PCDD, PCDF, co-PCB), polychlorinated biphenyls (PCBs), and volatile organic pollutants (VOC).

And according to this invention, in order to cool the extraction gas extracted with the extraction means with the 1st heat exchanger, and to remove the acidic gas in extraction gas, the poisoning of the catalyst by acidic gas is restrained low. Can do. In addition, the cooled extraction gas is reheated by the second heat exchanger, adjusted to a temperature suitable for decomposition of the organic pollutant, and then introduced into the catalyst device, so that the organic pollutant is efficiently removed. Is possible. In addition, at this time, since the extraction gas is heated by using the heat recovered by the first heat exchanger, the extraction gas can be heated by effectively using the recovered heat amount, thereby reducing the operation cost. It is also possible to plan.

In the cement kiln bleed gas processing system, the separation means can be constituted by a dry dust collector, and is cooled by the first heat exchanger between the dry dust collector and the first heat exchanger. An adding means for adding a desulfurizing agent to the extracted gas can also be provided. In particular, when the addition means is provided, the acidic gas in the extracted gas can be more reliably removed, and the poisoning of the catalyst by the acidic gas can be minimized.

In the cement kiln extraction gas processing system, the separation means can be constituted by a wet dust collector, whereby the acidic gas in the extraction gas can be more reliably removed, and the catalyst is covered with the acidic gas. Poison can be minimized.

In the cement kiln bleed gas treatment system, the first heat exchanger can be constituted by a corrosion-resistant heat exchanger whose inner wall is subjected to a corrosion-resistant treatment, and a dust collector and the like after the first heat exchanger are also included. Corrosion-resistant treatment can be performed. As the corrosion resistance treatment, a coating such as a fluororesin can be used.

Further, the present invention is a method for treating a cement kiln extraction gas, wherein a part of the combustion gas is extracted from a kiln exhaust gas flow path from the bottom of the cement kiln to the bottom cyclone, and the extracted extraction gas is Heat is recovered while cooling with the first heat exchanger, dust is separated from the cooled extracted gas, and the extracted gas from which the dust has been separated is introduced into the second heat exchanger, and the first heat exchanger The heat extracted in step (b) is used for heating, and the heated extraction gas is introduced into the catalyst device to remove organic pollutants from the extraction gas. According to the present invention, as in the case of the above-described invention, poisoning of the catalyst by acidic gas can be minimized, and organic pollutants in the chlorine bypass exhaust can be efficiently removed.

In the cement kiln extraction gas processing method, the extraction gas extracted can be cooled to 200 ° C. or less by the first heat exchanger, and according to this, the sulfur oxide in the extraction gas is efficiently removed. And more heat can be recovered from the first heat exchanger. In addition, the minimum of cooling will be about 20 degreeC which is normal temperature.

In the method for treating a cement kiln extraction gas, the extraction gas from which the dust has been separated can be heated to 150 ° C. or more and 500 ° C. or less by the second heat exchanger. It is possible to efficiently decompose and remove harmful pollutants in the gas. When the temperature of the extraction gas is less than 150 ° C., it is difficult to desire a sufficient decomposition rate of harmful pollutants, and when it is higher than 500 ° C., there is a problem that the catalyst life is adversely affected.

As described above, according to the present invention, when the cement kiln extraction gas is purified using the catalyst device, it is possible to minimize the poisoning of the catalyst by the acid gas, and the organic contamination contained in the extraction gas. Substances can be removed efficiently.

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

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

The gas extraction unit 2 is a facility for extracting a part of the combustion gas from the kiln exhaust gas flow path from the bottom of the cement kiln 4 to the lowermost cyclone (not shown). The gas extraction unit 2 separates a probe 5 for extracting combustion gas, a cooling fan 6 for supplying cold air into the probe 5 to quench the extraction gas G1, and coarse dust D1 contained in the extraction gas G1. It is composed of a cyclone 10 as a classifier.

The gas processing unit 3 is a facility for removing harmful substances in the extracted gas. The gas processing unit 3 collects the first heat exchanger 11 that cools the extraction gas G2 discharged from the cyclone 10 and the fine dust D2 in the extraction gas G2 that is cooled by the first heat exchanger 11. Bag filter 12, a dust tank 13 for collecting the fine dust D2 discharged from the first heat exchanger 11 and the bag filter 12, an induction fan 16 for inducing the exhaust gas G3 of the bag filter 12, and an induction fan 16 includes a second heat exchanger 17 that heats the exhaust gas G3 attracted by 16, a catalyst device 18 that removes organic pollutants from the exhaust gas G4 heated by the second heat exchanger 17, and the like.

The first heat exchanger 11 is provided for cooling the extraction gas G2 and removing the acid gas in the extraction gas G2. When cooling the extraction gas G2, it is preferable to cool it to 200 ° C. or less, thereby promoting the reaction between calcium and sulfur contained in the extraction gas and removing sulfur oxides (SOx). Is possible. When the desulfurization action is insufficient, the blowing device 14 may be installed on the pipe line 11a connecting the first heat exchanger 11 and the bag filter 12, and a desulfurizing agent may be added as necessary. As the desulfurizing agent, slaked lime, quick lime, calcined cement material (cement material separated from the lowermost cyclone of the preheater, etc.), coal ash or the like can be used. Moreover, in order to improve the corrosion resistance with respect to acidic gas, it is preferable to use the corrosion-resistant heat exchanger by which coating, such as a fluororesin, was given to the 1st heat exchanger 11 at the inner wall.

The second heat exchanger 17 is provided to reheat the exhaust gas G3 in the front stage of the catalyst device 18 and adjust the temperature of the exhaust gas G3 to a temperature suitable for the catalyst activity. Between the 2nd heat exchanger 17 and the 1st heat exchanger 11, the connecting pipe line 17a for circulating a heat medium is provided, and the 2nd heat exchanger 17 is the 1st heat exchange. The exhaust gas G3 is heated using the heat recovered by the vessel 11. When the exhaust gas G3 is heated, it is preferably heated to 150 ° C. or higher and 500 ° C. or lower, whereby the organic pollutant removal efficiency in the catalyst device 18 can be improved. When the amount of heat in the second heat exchanger 17 is insufficient, a heater (not shown) or the like may be installed on the connecting pipe line 17a to supplementarily heat the heat medium.

The catalyst device 18 is provided for decomposing and removing organic pollutants such as persistent organic pollutants (POPs) and volatile organic pollutants (VOC) contained in the exhaust gas G4. The catalyst device 18 is configured in a honeycomb shape, and can be configured to be relatively small even when a large amount of exhaust gas is processed. In the catalyst device 18, any catalyst capable of removing POPs and VOC, such as an oxide catalyst such as a titanium / vanadium catalyst, a noble metal catalyst having a noble metal selected from platinum, palladium, rhodium and ruthenium, can be disposed. In addition, by comprising an oxide-based catalyst on the upstream side and a noble metal-based catalyst on the downstream side, the upstream titanium / vanadium catalyst efficiently decomposes NOx and the like in addition to POPs and VOC, and the downstream side. A platinum-based catalyst can efficiently remove CO, odor, and the like. Here, the titanium / vanadium catalyst means a catalyst essentially including titanium (Ti) and vanadium (V). This catalyst exhibits a high function for decomposing and removing organic pollutants, and has a high decomposition activity (denitration activity) of NOx, which is a harmful substance.

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 4 to the lowermost cyclone, a part of the combustion gas is extracted by the probe 5, and at the same time, the cooling air from the cooling fan 6 causes the melting point of the chlorine compound to be 600 to 700. Rapidly cool to below ℃. Next, in the cyclone 10, the extraction gas G1 exhausted from the probe 5 is separated into the coarse powder D1 and the gas G2 containing the fine powder D2, and the coarse powder D1 is returned to the cement kiln system while being 250 to 600 ° C. The extracted gas G2 is introduced into the first heat exchanger 11.

Then, in the first heat exchanger 11, the sulfur content (SOx) and the acid gas are removed while cooling the extraction gas G2 to 200 ° C. or less. Next, in the bag filter 12, the fine powder D2 in the gas G2 is collected and collected in the dust tank 13 as chlorine bypass dust. Next, the exhaust gas G3 of the bag filter 12 is attracted by the attracting fan 16 and reheated to 150 ° C. or more and 500 ° C. or less in the second heat exchanger 17. Thereafter, the heated exhaust gas G4 is introduced into the catalyst device 18, and organic pollutants such as POPs and VOC are decomposed to purify the exhaust gas G4. The exhaust gas G5 purified by the catalyst device 18 may be released to the atmosphere via an exhaust fan (not shown), or may be returned to the cement process for heat recovery.

As described above, in the present embodiment, the extraction gas G1 extracted by the probe 5 is cooled by the first heat exchanger 11, and the acidic gas in the extraction gas G1 is removed. 18 poisoning can be suppressed to a low level. In addition, the cooled exhaust gas G3 is reheated by the second heat exchanger 17 and adjusted to a temperature suitable for the decomposition of the organic pollutant, and then introduced into the catalyst device 18, so that the organic pollutant is efficiently removed. It becomes possible. In addition, since the heat recovered by the first heat exchanger 11 is used when the exhaust gas G3 is heated, the exhaust gas G3 can be heated by effectively using the recovered heat amount, thereby reducing the operating cost. It becomes possible.

Next, a second embodiment of the cement kiln extraction gas processing system according to the present invention will be described with reference to FIG. In this figure, the same components as those of the processing system 1 of FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

As shown in the figure, this processing system 20 includes a first heat exchanger 11 that cools the extraction gas G2 in the gas processing unit 3, and a wet extraction gas G2 that is cooled by the first heat exchanger 11. Wet dust collector 21 that collects dust, an induction fan 16 that attracts exhaust gas G3 of wet dust collector 21, a second heat exchanger 17 that heats exhaust gas G3 attracted by induction fan 16, and a second heat exchanger 17 And a catalyst device 18 for removing organic pollutants from the exhaust gas G4 heated in step (b). In addition, the structure of the gas extraction part 2 is the same as the case of the processing system 1 of FIG.

The wet dust collector 21 is provided to collect water-soluble components and dust contained in the extraction gas G2 cooled by the first heat exchanger 11, and includes dust and water-soluble chlorine containing sulfur oxide (SOx) and the like. Collect the compound. A circulating liquid tank 22 is provided below the wet dust collector 21, and a mist separator 23 is disposed on the downstream side of the circulating liquid tank 22.

In the processing system 20, the extraction gas G1 extracted by the probe 5 is cooled to 200 ° C. or less by the first heat exchanger 11, and after removing SOx contained in the extraction gas G2, the extraction gas G1 is further extracted by the wet dust collector 21. Wet dust collection of SOx remaining in the gas G2. Therefore, the acidic gas in the extracted gas G2 can be more reliably removed, and poisoning of the catalyst device 18 by the acidic gas can be minimized.

In addition, after wet dust collection by the wet dust collector 21, the exhaust gas G3 from the wet dust collector 21 is reheated to 150 ° C. or more and 500 ° C. or less by the second heat exchanger 17, and then the catalyst device 18 is passed through. Organic pollutants such as POPs and VOCs can be efficiently decomposed and removed. Furthermore, in the second heat exchanger 17, the exhaust gas G3 is heated using the heat recovered by the first heat exchanger 11, so that it is possible to reduce the operating cost, as in the first embodiment. The effect of this can be obtained.

It is a flowchart which shows 1st Embodiment of the processing system of the cement kiln extraction gas concerning this invention. It is a flowchart which shows 2nd 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 Cement kiln 5 Probe 6 Cooling fan 10 Cyclone 11 First heat exchanger 11a Pipe line 12 Bag filter 13 Dust tank 14 Blowing device 16 Induction fan 17 First 2 heat exchanger 17a Connecting pipe 18 Catalytic device 20 Cement kiln extraction gas processing system 21 Wet dust collector 22 Circulating liquid layer 23 Mist separator

Claims

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;
A first heat exchanger that recovers heat while cooling the extraction gas extracted by the extraction means;
Separation means for separating dust from the bleed gas cooled by the first heat exchanger;
A second heat exchanger for heating the extraction gas from which the dust has been separated using heat recovered by the first heat exchanger;
A cement kiln extraction gas processing system comprising: a catalyst device that removes organic pollutants from the extraction gas heated by the second heat exchanger.
The cement kiln extraction gas processing system according to claim 1, wherein the separation means is a dry dust collector.
The cement according to claim 2, further comprising addition means for adding a desulfurizing agent to the bleed gas cooled by the first heat exchanger, between the first heat exchanger and the dry dust collector. Kiln extraction gas processing system.
The cement kiln bleed gas treatment system according to claim 1, wherein the separation means is a wet dust collector.
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,
Recovering heat while cooling the extracted gas extracted by the first heat exchanger;
Separating dust from the cooled bleed gas,
The extraction gas from which the dust has been separated is introduced into a second heat exchanger and heated using the heat recovered by the first heat exchanger,
A method for treating a cement kiln extraction gas, wherein the heated extraction gas is introduced into a catalyst device to remove organic pollutants from the extraction gas.
The cement kiln bleed gas treatment method according to claim 5, wherein in the first heat exchanger, the extracted bleed gas is cooled to 200 ° C or lower.
The method for treating a cement kiln extraction gas according to claim 5 or 6, wherein in the second heat exchanger, the extraction gas from which the dust has been separated is heated to 150 ° C or more and 500 ° C or less.