JP2006089298A - Method and apparatus for disposing exhaust gas in cement firing facility - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for disposing an exhaust gas in a cement firing facility capable of minimizing effects on operation of cement production, and increasing the disposable amount of industrial waste containing high level of chlorine. <P>SOLUTION: This method for disposing the exhaust gas comprises the steps of extracting a part of the exhaust gas G exhausted from a cement kiln 41 by a probe 43, cooling the extracted exhaust gas G to the melting point of a chlorine compound or lower by a cooling fan 44, collecting dust contained in the cooled gas by a cooling chamber 45 while further cooling the dust by a cooling fan 46, classifying the collected dust into a coarse powder fraction and a fine powder fraction by a classifier 50, and the each dust after classification is reutilized or disposed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for treating exhaust gas in a cement firing facility, and more specifically, the extraction rate when extracting a part of the exhaust gas containing a chlorine compound discharged from the cement firing facility is particularly high. The present invention relates to a method and apparatus for treating exhaust gas in a cement firing facility that can reduce the effect of exhaust gas on the cement firing facility.

In recent years, volatile components such as chlorine contained in industrial wastes have increased in cement kilns as the amount of industrial waste treatment using cement production facilities has increased. Volatile components such as chlorine not only degrade cement quality, but also adversely affect the operation of the entire cement manufacturing facility including cement kilns. A chlorine bypass device that removes volatile components such as chlorine is installed.
This chlorine bypass device removes volatile components such as concentrated chlorine by repeatedly volatilizing and condensing exhaust gas between the cement kiln and the preheater. By extracting and cooling the part, chlorine bypass dust that solidifies volatile components mainly composed of chlorine compounds is generated, and the chlorine bypass dust is discharged out of the cement production facility to remove the chlorine compounds from the cement. It is an apparatus which removes from a kiln (for example, refer patent document 1, 2).
Here, the conventional chlorine bypass device will be described more specifically.

  FIG. 6 is a schematic view showing an example of a conventional chlorine bypass device. In the figure, 1 is a rotary kiln for firing cement raw material M, 2 is a probe for extracting exhaust gas g from the rotary kiln 1, and 3 is an exhaust gas g extracted. 4 is a fan that sends cooling air to the cooler 3, and 5 is a cyclone type classification that classifies dust contained in the cooled exhaust gas g. , 6 is an indirect air-cooling heat exchanger that performs heat exchange of the exhaust gas g, 7 is a fan that sends cooling air to the indirect air-cooling heat exchanger 6, and 8 is exhaust gas g that is discharged from the indirect air-cooling heat exchanger 6. A dust collector that collects residual dust from the dust, 9 is a fan that exhausts exhaust gas from the dust collector 8, 10 is a storage that stores dust W containing high concentrations of chlorine discharged from the indirect air-cooling heat exchanger 6 and the dust collector 8. A silo, 11 is a hopper for storing and supplying dust W containing chlorine at a high concentration, 12 is a measuring instrument for measuring the weight of the dust W discharged from the storage silo 11, and 13 is discharged from the rotary kiln 1 It is a transport device that transports the cement clinker C for mixing.

In this chlorine bypass device, a part of the exhaust gas g is extracted from the rotary kiln 1 using the probe 2, and the exhaust gas g extracted by introducing cold air into the probe 2 is cooled below the melting point of the chlorine compound. Then, chlorine bypass dust W is generated.
Next, the chlorine bypass dust W is classified by the cyclone type classifier 5 as a classification particle size for classifying about 7 to 10 μm into coarse and fine particles, and the classified coarse particles are returned to the rotary kiln 1. By removing the dust W on the fine grain side, which is not collected by the cyclone classifier 5, through the indirect air cooling heat exchanger 6 and the hopper 11, the chlorine content circulated and concentrated in the cement kiln 1 is removed. Decrease.
By attaching this chlorine bypass device to the cement kiln 1, 30 to 60% of the amount of chlorine brought into the cement kiln 1 can be removed with the amount of extracted gas within 2% of the high-temperature exhaust gas discharged from the cement kiln 1. can do.

FIG. 7 is a schematic diagram showing an example of a conventional high extraction type chlorine bypass device, which is an apparatus that can apply the exhaust gas extraction rate in the kiln bottom of a cement kiln to a range of 2% to 5%. In the figure, 21 is a rotary kiln for firing cement raw material, 22 is a pre-heater rising duct connected to the rotary kiln 21, 23 is a probe having a double pipe structure for extracting a part of the exhaust gas g, and 24 is an exhaust gas g extracted. A first cooler for cooling, 25 is a cyclone type classifier for classifying dust contained in the cooled exhaust gas g, 26 is a second cooler for cooling the exhaust gas g from which dust is separated, and 27 is in the exhaust gas g. A dust collector that collects dust remaining in the dust collector, 28 is a suction fan that exhausts exhaust gas from the dust collector 27, and 29 is a dust tank that stores dust containing high concentration of chlorine discharged from the second cooler 26 and the dust collector 27. is there.
Cold air fans 30 to 32 are connected to the probe 23, the first cooler 24, and the second cooler 26, respectively.

In this high extraction type chlorine bypass device, the first cooler 24 first cools the exhaust gas from the rotary kiln 21 to 400 to 600 ° C. while extracting a part of the exhaust gas from the rotary kiln 21 by the probe 23 having a double pipe structure. Secondary cooling to 300-400 ° C., and then classifying the dust in the exhaust gas secondary cooled by the cyclone type classifier 25 into coarse powder and fine powder to return the coarse powder to the rotary kiln 21, and fine powder The contained exhaust gas is finally cooled to 100 to 200 ° C. by the second cooler 26, and fine powder is recovered from the exhaust gas cooled by the dust collector 27.
On the other hand, the chlorine bypass dust removed to the outside of the cement kiln 21 is processed in a cement grinding system by being added to a cement clinker or the like or directly supplied to a cement finishing mill. The chlorine content is removed by washing with water, and the residue is reused as a cement raw material so that it does not adversely affect the operation of the cement kiln 21 system by the chlorine circulated and concentrated in the cement kiln system 21. ing.
Japanese Patent No. 338714 International Publication No. 00/12444

By the way, in the conventional chlorine bypass device shown in FIG. 6, the amount of chlorine in industrial waste brought into cement kilns increases as the amount of industrial waste containing high chlorine increases. The salt treatment becomes insufficient, and there is a problem that sufficient chlorine cannot be removed from the cement kiln 1.
When the amount of chlorine increases, a chlorine bypass device capable of extracting a larger amount of exhaust gas is required. Conventionally, the amount of exhaust gas extracted from the kiln bottom is within 2%, but 2 to 5% or more. The amount of bleed is required.
Further, in the case of this chlorine bypass device, there is a problem that it becomes difficult to uniformly cool the extracted exhaust gas when the device is enlarged. Therefore, a high extraction type chlorine bypass device has been proposed which performs uniform cooling by increasing the number of cooling stages as shown in FIG.

However, this high extraction type chlorine bypass device has the following problems.
(1) The cooling process includes three steps of a probe, a first cooler, and a second cooler, and includes a step of classifying dust contained in the extracted exhaust gas with a cyclone classifier. In order to extract a large amount of exhaust gas at the kiln bottom, it is necessary to improve the pressure resistance performance of the equipment and the performance of the suction fan.
(2) Since the classified coarse powder was returned to the cement kiln, only the amount of chlorine contained in the extracted exhaust gas corresponding to the amount of chlorine contained in the coarse powder returned without being bypassed was further cemented. It is necessary to increase the amount of exhaust gas extracted from the kiln bottom of the kiln, and the chlorine bypass system itself becomes excessive.
In this case, the probe also needs to be enlarged, but there is not enough space in the kiln bottom of the cement kiln to install the enlarged probe. Therefore, the probe is installed at each of the two locations on the kiln bottom. In addition, problems in probe installation have increased, such as increasing the total amount of exhaust gas extracted by increasing the extraction gas velocity at the probe.

(3) Since it is necessary to increase the amount of exhaust gas extracted from the kiln bottom of the cement kiln, the energy loss due to the large amount of exhaust gas extracted increases, and the cement firing efficiency decreases. Therefore, there is a possibility that the influence on the operation of cement production becomes large.
(4) Since the indirect air cooling device is mainly used for the second cooler, the cooling performance is reduced due to adhesion of chloride scale inside the cooling device, and the exhaust gas extracted. The amount of is inevitably reduced.

In addition, conventional chlorine bypass devices and high extraction type chlorine bypass devices minimize the amount of collected dust by returning the coarse particles classified by the cyclone classifier to the cement kiln, and the subsequent dust treatment It is characterized by making it easier.
Therefore, if the entire amount of dust contained in the extraction gas is collected without returning the coarse particles classified by the cyclone classifier to the cement kiln, the amount of collected dust increases. There was a tendency for problems in dust processing to increase.

  The present invention has been made to solve the above problems, and even if the amount of exhaust gas extracted from the cement kiln is increased, the influence on the operation of cement production can be reduced, High chlorine content dust contained in the extracted exhaust gas can be treated more easily, and the impact on cement manufacturing operations is reduced and the amount of industrial waste containing high chlorine content is increased. It is an object of the present invention to provide an exhaust gas treatment method and treatment apparatus in a cement firing facility that can be used.

  As a result of intensive studies to solve the above problems, the present inventors have collected the dust contained in the exhaust gas by cooling the exhaust gas extracted from the cement firing facility below the melting point of the chlorine compound. By classifying the collected dust into coarse and fine particles, the amount of exhaust gas extracted from the cement firing facility can be increased, and the chlorine compound-containing dust contained in the extracted exhaust gas can be treated. Has been found to be easily performed, and the present invention has been completed.

  That is, the method for treating exhaust gas in the cement firing facility of the present invention is a method for treating exhaust gas in a cement firing facility in which part of the exhaust gas discharged from the cement kiln is extracted and chlorine compounds are removed from the extracted exhaust gas. A cooling process for cooling the extracted exhaust gas to a melting point of the chlorine compound or less, a dust collection process for collecting dust contained in the cooled exhaust gas, and the collected dust as coarse particles. It is characterized by comprising a classification step for classifying into fine particles and a treatment step for reusing or discarding each dust after classification.

By adopting such a configuration, the dust contained in the exhaust gas cooled by the dust collection process is collected, and the dust collected by the classification process is classified into coarse and fine particles, thereby firing the cement. Even when the amount of exhaust gas extracted from the facility is increased, the amount of exhaust gas extracted can be kept relatively low compared to the conventional example, and therefore the impact on the cement manufacturing operation is kept low. It becomes possible.
Moreover, since the collected dust can be easily treated, it is possible to further increase the treatment of industrial waste containing high chlorine.

  In this exhaust gas treatment method, the dust collection step includes a coarse dust collection step for separating and collecting coarse dust contained in the cooled exhaust gas, and a residue excluding the coarse dust contained in the exhaust gas. A residual dust collecting step for collecting dust, and the classification step is a classification step for further classifying the coarse dust into a coarse powder and a fine powder, and the classified coarse powder is used as a cement raw material. It is preferable to return to the cement kiln.

  By adopting such a configuration, the dust collected in the coarse dust collecting step for separating and collecting coarse dust is further classified into coarse and fine powder, and the coarse powder is cemented. Since it is returned to the baking facility, the amount of dust to be processed is reduced without impairing the efficiency of the processing apparatus, and dust processing becomes easier.

It is preferable that the classified particle diameter classified into the coarse powder and the fine powder in the classification step can be arbitrarily adjusted in the range of 5 μm to 60 μm.
With such a configuration, it is possible to arbitrarily change the chlorine concentration of coarse and fine powder obtained by classification, and it is possible to obtain dust with a chlorine concentration according to each treatment method Thus, it is easy to effectively use dust.

In this exhaust gas treatment method, the reuse is preferably one or more of addition to cement, reuse as a cement raw material, and addition to a cement-based solidifying agent.
By setting it as such a structure, it becomes possible to reduce the influence by the addition to cement. Moreover, even if only the coarse powder having a low chlorine concentration is directly circulated as a cement raw material, the amount of chlorine brought back into the cement firing facility can be kept extremely low.

In this exhaust gas treatment method, it is preferable to remove adhering chlorine compounds by water washing when reused as the cement raw material.
By adopting such a configuration, even when a fine powder having a relatively high chlorine concentration is reused as a cement raw material, the chlorine compound adhering to the dust is easily removed by washing with water. The amount of chlorine compound contained is extremely small.
Therefore, even when this dust is reused as a cement raw material, the chlorine extracted from the cement firing facility is not brought into the cement firing facility again, and the influence on the operation of the cement production facility is eliminated. Can do.

In this exhaust gas treatment method, it is preferable to discard the waste after solidifying one of the dust, the fine particles, and the residual dust using a cement-based solidifying material.
With such a configuration, the chlorine compound contained in the dust is contained by the cement-based solidifying material, and there is no possibility of leaking to the outside.

  The exhaust gas treatment apparatus in the cement firing facility of the present invention is an exhaust gas treatment apparatus in a cement firing facility for extracting a part of the exhaust gas discharged from the cement kiln and removing chlorine compounds from the extracted exhaust gas, Extraction means for extracting a part of the exhaust gas discharged from the cement kiln, cooling means for cooling the extracted exhaust gas below the melting point of the chlorine compound, and dust for collecting dust contained in the cooled exhaust gas It is characterized by comprising collecting means and classification means for classifying the collected dust into coarse and fine particles.

In this exhaust gas treatment device, the dust contained in the exhaust gas cooled by the dust collection means is collected, and the dust collected by the classification means is classified into coarse and fine particles, so that Even when the amount of exhaust gas extracted is increased to 2% by volume or more with respect to the amount of exhaust gas discharged from the cement kiln, the chlorine removal efficiency is increased, and the impact on the cement manufacturing operation is kept small. Is possible.
In addition, since the collected dust can be easily treated, it is possible to further increase the treatment of industrial waste containing high chlorine.

  The dust collecting means includes a coarse dust collecting means for separating and collecting coarse dust contained in the cooled exhaust gas, and a residual dust for collecting residual dust excluding the coarse dust contained in the exhaust gas. Conveying means comprising the collecting means, the classifying means as classifying means for further classifying the coarse dust into coarse powder and fine powder, and conveying the classified coarse powder to the cement kiln as a cement raw material It is preferable to provide.

  In this exhaust gas treatment device, it is possible to further classify the dust collected by the coarse particle dust collecting means, and to return the coarse powder content with less chlorine content directly to the cement firing facility, and the chlorine removal efficiency of the treatment device. The amount of dust to be processed can be reduced, and dust processing becomes easier.

The amount of exhaust gas extracted by the extraction means is preferably 2% by volume or more of the total amount of exhaust gas discharged from the cement kiln.
By adopting such a configuration, it becomes possible to increase the amount of exhausted gas extracted from the conventional chlorine bypass device, and as a result, the amount of chlorine compounds removed from the cement firing equipment is increased, resulting in a high chlorine content. It becomes possible to increase the processing amount of industrial waste.

According to the method for treating exhaust gas in a cement firing facility of the present invention, even if the amount of exhaust gas extracted from the cement firing facility is increased, the amount of exhaust gas extracted can be kept relatively low. Therefore, the influence on the operation of cement production can be kept low.
Moreover, since the collected dust can be easily treated, the treatment of industrial waste containing high chlorine can be further increased.

According to the exhaust gas treatment apparatus in the cement firing facility of the present invention, even when the amount of exhaust gas extracted from the cement firing facility is increased to 2% by volume or more with respect to the amount of exhaust gas discharged from the cement kiln, Chlorine removal efficiency can be increased and the impact on cement production operations can be kept low.
Moreover, since the collected dust can be easily treated, the treatment of industrial waste containing high chlorine can be further increased.

An embodiment of an exhaust gas treatment method and treatment apparatus in a cement firing facility of the present invention will be described with reference to the drawings.
The present embodiment is specifically described for better understanding of the gist of the invention, and does not limit the invention unless otherwise specified.

  FIG. 1 is a schematic diagram showing an exhaust gas treatment apparatus in a cement firing facility according to an embodiment of the present invention. In the figure, 41 is a cement kiln for firing cement raw material, and 42 is a preheater rising connected to the cement kiln 41. A duct 43 is a probe (bleeding means) whose tip is inserted into the preheater rising duct 42, 44 is a cooling fan (cooling means), 45 is a cooling chamber (coarse dust collecting means), 46 is a cooling fan, 47 is A bag filter (residual dust collecting means), 48 is a suction fan, 49 is a dust silo, and 50 is a classifier (classifying means).

  The probe 43 has a double-pipe structure, and a part of the exhaust gas G discharged from the cement kiln 41 is extracted, and the extracted exhaust gas G is cooled below the melting point of the chlorine compound by the cooling air from the cooling fan 44, that is, 700. It cools to below the temperature of ° C. Usually, it cools to the range of 400 degreeC to 600 degreeC.

The cooling chamber 45 cools the exhaust gas G extracted by the cooling fan 46 in the chamber, and simultaneously separates and collects coarse dust particles having a particle size of 100 μm or more contained in the exhaust gas G.
The chamber 45 is preferably capable of preventing a deterioration in the mixing property between the extracted exhaust gas G and the cooling air associated with the high extraction type.

  The exhaust gas G introduced into the chamber 45 is swirled inside the chamber together with the cooling air supplied by the cooling fan 46 to be cooled to a temperature lower than the heat resistance temperature of the subsequent bag filter 47. At the same time, coarse dust having a particle size of 100 μm or more contained in the exhaust gas G is separated. Since the coarse dust is difficult to cool in a short time and may damage the filter cloth of the subsequent bag filter 47, it is necessary to remove the coarse dust at the front stage of the bag filter 47.

The coarse dust separation performance is not limited as long as coarse dust having a particle diameter of 100 μm or more can be separated from the exhaust gas G, but dust having a particle diameter of several tens μm or more contained in the exhaust gas G can also be separated. Is preferred.
The tendency of the chlorine compound to adhere to dust is that the dust collected in the chamber 45 has a smaller proportion of the chlorine compound adhering than the dust collected by the bag filter 47. The coarser particle dust is, the smaller the rate of adhesion of chlorine compounds. Therefore, the coarse particles obtained by separating and collecting in advance the dust of tens of μm or more contained in the exhaust gas G in the cooling chamber 45 and classifying the collected dust again contain almost all of the chlorine compound. It can be reused as a cement raw material.

  The bag filter 47 removes dust having a smaller particle size and coagulating and adhering chlorine from the exhaust gas G ′ from which coarse dust having a particle size of 100 μm or more or several tens of μm or more has been removed. Is 150 ° C. or higher.

The classifier 50 classifies the collected dust stored in the dust silo 49 into a coarse powder and a fine powder, and has a structure in which the classification particle size for classification into the coarse powder and the fine powder can be changed. Preferably, for example, a centrifugal classifier is preferably used.
The classified particle size classified into the coarse powder and the fine powder is preferably in the range of 5 μm to 60 μm.

This classified particle size varies depending on the processing requirements for the dust separated from the exhaust gas G.
As a main treatment method of dust separated from the exhaust gas G, for example,
(1) Add to cement (2) Add to cement-based solidification material (3) Reuse as cement raw material (4) Solidify with cement-based solidification material and dispose of (5) Treatment outside cement-based system by other methods Etc.

  Normally, “(1) Addition to cement” is preferentially performed, but as the amount of industrial waste used increases, the amount of dust contained in the exhaust gas G extracted from the cement kiln 41 also increases. To do. In this case, if the total amount of the dust is added to the cement, there is a possibility that a problem occurs in the quality of the cement. Therefore, the amount of dust added to the cement is limited, and the remaining dust is treated by any one of the above treatment methods (2) to (5) or a combination of these treatment methods.

For example, in the case of (1) above, the amount of dust added must be within the allowable range for the chlorine content in cement and the content of dust components other than chlorine.
The same applies to the case (2).
Therefore, by separating the collected dust into components having different chlorine contents, it is possible to add the components so as to fall within the required allowable ranges of both components.

In the case of the above (3), if dust having a high chlorine concentration is recycled as a cement raw material, there is a risk of adversely affecting the operation of the cement production facility. Therefore, it is necessary to use dust having as little chlorine compound content as possible. .
Therefore, the method of washing the dust with water and removing the chlorine content and then returning it as a cement raw material, or as described above, classifying the dust and reusing the coarse powder with a low chlorine content as the cement raw material, One of the methods is adopted.

In the case of washing with water, fine dust having a high chlorine content is preferred in order to increase the amount of alkali salt recovered when recovering chlorine as a useful product.
In the case of (4), in order to minimize the amount of disposal, only fine particles with high chlorine concentration are selected and disposed of, and the remaining coarse powder is reused as a cement raw material.

  Here, the classifier 50 is provided at the rear stage of the dust silo 49, but the classifier 50 is not necessarily provided at the rear stage of the dust silo 49. For example, when a part of the dust is mixed with cement, It is good also as a structure attached to the crushing equipment.

  When part of dust is mixed with cement, it is determined by the control value of the chlorine concentration contained in the cement and the control value of the concentration of dust components other than chlorine compounds. It is preferable that they can be selected. Therefore, the classification particle size in the classification process is changed, dust having a chlorine concentration according to the purpose is obtained, and the addition amount is determined so that a cement satisfying both the above control values can be obtained.

  Here, for dust not added to cement, dust with a small chlorine concentration is directly reused as a raw material for cement, and when dust with a high chlorine concentration is included, washing or cement-based solidifying material, etc. It is solidified and processed appropriately, such as disposal.

Next, an exhaust gas treatment method in the cement firing facility of the present embodiment will be described.
(1) Extraction and cooling The probe 43 extracts 2 to 5% by volume of the exhaust gas G discharged from the cement kiln 41, and the exhaust gas G extracted by the cooling air from the cooling fan 44 is below the melting point of the chlorine compound. Cooling.

(2) Collection of coarse dust The cooled exhaust gas G is introduced into the cooling chamber 45 and swirled inside the chamber 45 together with the cooling air supplied by the cooling fan 46, whereby the heat resistance temperature of the bag filter 47, for example, Cool to below 200 ° C. At the same time, coarse particles having a particle size of 100 μm or more or several tens of μm or more contained in the exhaust gas G and having relatively little coagulation and adhesion of chlorine compounds are separated and collected.

(3) Collection of residual dust The exhaust gas G ′ from which coarse dust has been removed is introduced into the bag filter 47, and residual fine dust that has not been collected in the cooling chamber 45 is further collected from the exhaust gas G ′. Gather.
In the bag filter 47, all of the solidified chlorine compound is captured by the dust layer attached to the filter cloth and attached to the dust surface. Therefore, the chlorine concentration of the residual dust is higher than that of the coarse dust collected in the cooling chamber 45.

(4) Dust storage The dust silo 49 mixes coarse dust separated and collected by the cooling chamber 45 with fine dust separated and collected by the bag filter 47 and solidified and adhered with a large amount of chlorine compounds. This mixed dust is stored.
Further, depending on the method of processing the collected dust, coarse dust and fine dust may be stored in separate dust silos 49.

(5) Dust classification The classifier 50 classifies the mixed dust into coarse powder and fine powder. Further, when coarse dust and fine dust are stored in separate dust silos 49, only coarse dust may be classified according to the purpose of processing.
The classification particle diameter classified into the coarse powder and the fine powder is in the range of 5 μm or more and 60 μm or less, and the classified particle diameter is adjusted according to the use of each treatment of the coarse powder and the fine powder.

For example, when the coarse particles are directly circulated as a cement raw material, it is necessary to minimize the chlorine concentration of the coarse particles to be circulated, and only the coarse particles collected in the cooling chamber 45 are classified. By recirculating use, the amount of chlorine brought into the cement firing facility can be minimized.
The classification particle size of this coarse dust is, for example, 10 μm as the classification particle size when the treatment amount is increased as a cement raw material, but the amount of chlorine brought into the cement firing equipment is less than the treatment amount as the cement raw material. Is prioritized, the classified particle size is in the range of 30 μm or more.

  In addition, when adding to cement or cement-based solidified material, if the allowable amount of added chlorine component or dust component contained in the cement or cement-based solidified material after addition is large, do not perform classification. All of the mixed dust will be added. On the other hand, when the allowable amount of the dust component added is smaller than that of the chlorine component, classification is performed by reducing the classified particle size, and only the obtained fine particles having a high chlorine concentration are added.

(6) Reuse of dust As mentioned above, each of the coarse and fine particles can be reused by adding to cement or cement-based solidifying agent or reusing as a cement raw material. Is selected.
When reusing as a cement raw material, it is possible to directly use coarse particles after classification as described above. However, when reusing a large amount of dust, the chlorine compound contained in the dust is washed with water. It is preferable to remove.
In this way, since the dust washed with water contains a very small amount of chlorine compound, a large amount of dust can be reused as a cement raw material.

(7) Disposal of dust When the above-mentioned dust reuse does not cover all dust, the dust is discarded.
Usually, by solidifying with a cement-based solidifying material or the like, the chlorine compound contained in the dust is contained so as not to leak to the outside, and is disposed at the waste disposal site.

According to the exhaust gas treatment method of the present embodiment, the extracted exhaust gas G is cooled below the melting point of the chlorine compound, the cooled exhaust gas G is further cooled, and at the same time, coarse dust contained therein is collected, Fine dust is collected, and each collected dust is classified and disposed of according to the purpose, so the range of options for processing the collected dust can be expanded and processed easily. Can do.
In addition, since an appropriate treatment is performed on the total amount of dust containing the collected chlorine compound without returning a part of the dust to the cement kiln 41, the chlorine compound can be effectively removed from the cement firing facility. Therefore, even if the amount of the exhaust gas G extracted from the cement kiln 41 is increased, the influence on the operation of the cement manufacturing facility can be reduced.

  In addition, by expanding the range of options for the treatment of collected dust, the amount added can be reduced even when added to cement or cement solidifying material, etc., and the impact on cement quality is minimized. To the limit.

According to the exhaust gas processing apparatus of the present embodiment, since the classifier 50 for classifying the collected dust into the coarse powder and the fine powder is provided after the dust silo 49, the exhaust gas discharged from the cement kiln 41 is reduced. Even when the amount of exhaust gas extracted from the kiln bottom is increased to 2% by volume or more, the chlorine removal efficiency can be increased and the influence on the cement manufacturing operation can be suppressed to a small level.
In addition, since the collected dust can be easily treated, the treatment of industrial waste containing high chlorine can be further increased.

Examples 1 and 2 of the present invention and conventional examples will be described below.
[Example 1]
Using the exhaust gas treatment apparatus of the present embodiment shown in FIG. 1, the coarse dust collected from the exhaust gas G extracted from the kiln bottom of the cement kiln 41 in the cooling chamber 45 is collected in a bag filter (BF) 47. The 50% passing particle size, the chlorine concentration and the yield were measured for each of the fine dust obtained by separation and the total dust obtained by mixing the above-mentioned coarse dust and fine dust in a yield weight ratio.

(1) 50% passing particle size The particle size distribution was measured for each of the above coarse dust, fine dust, and total dust, and the 50% passing particle size (μm) was determined.
For the measurement, a microtrack (MK-II particle size distribution meter, manufactured by Nikkiso Co., Ltd.) was used.

(2) Chlorine concentration The chlorine concentration was measured in accordance with “potential difference measurement method” of the Japanese Industrial Standard JIS R 5202 “Chemical analysis method of Portland cement” appendix method.
(3) Yield Each of the coarse dust and fine dust was weighed to determine the yield.
These measurement results are shown in Table 1 and FIGS.

FIG. 2 is a diagram showing the particle size distribution of all dust obtained by the exhaust gas treatment apparatus of the present embodiment, and FIG. 3 is a diagram showing the cumulative particle size distribution. The chlorine concentration of this dust was 66000 ppm.
FIG. 4 is a diagram showing the particle size distribution of coarse dust separated and collected in the cooling chamber 45 and fine dust obtained by separation in the bag filter (BF) 47. The chlorine concentration of the coarse dust was 19000 ppm, the chlorine concentration of the fine dust was 167000 ppm, and the dust collection ratio (weight ratio) was coarse dust: fine dust = 68: 32.
FIG. 5 is a diagram showing the trump distribution ratio (partial classification efficiency) in the cooling chamber 45 of the present embodiment calculated from the particle size distribution and the dust collection ratio.

According to the particle size distributions of FIGS. 2 and 4, a large difference was observed in the chlorine concentration of each dust, although a large difference was not recognized in the particle size composition of each collected dust. The reason is that the coarse dust collected in the cooling chamber 45 has less adhesion of the chlorine compound produced in the cooled extraction gas to the dust surface, while the fine dust collected in the bag filter 47 This is probably because almost all of the generated chlorine compound is trapped in the dust layer that collects and adheres to the surface of the filter cloth.
The adhesion concentration of the chlorine compound in the coarse dust collected in the cooling chamber 45 was 11% of the adhesion concentration of the chlorine compound in the fine dust collected by the bag filter 47.

[Example 2]
For each of the total dust, coarse dust, and fine dust obtained in Example 1, the properties of the coarse powder and fine powder obtained by classification with the classifier 50 were tested. Test items and test methods are as follows.

(4) Classification test Using the classifier 50, the classifier 50 is set so that the following classified particle diameter (particle diameter at which the partial classification efficiency is 50%) is set to classify all dust, Fine powder was collected and weighed to determine the yield.
Here, the classified particle size was set to four levels of 10 μm, 20 μm, 30 μm, and 50 μm.
Further, the chlorine concentration was measured in the same manner as above for each of the coarse powder and fine powder.
These measurement results are shown in Table 2.

In addition, the yield and chlorine concentration for each classified particle size were measured for the coarse powder and fine powder of the coarse dust and the coarse powder and fine powder of the fine dust, respectively.
Here, the classified particle size was set to four levels of 10 μm, 20 μm, 30 μm, and 50 μm.
These measurement results are shown in Table 3.

The chlorine concentration of the coarse and fine powders obtained by classification is in the range of 7000 to 30000 ppm, and this chlorine concentration range is obtained by classifying any of the above-mentioned total dust, coarse dust, and fine dust. Any concentration of dust can be obtained.
The thing with the lowest chlorine concentration is the dust of the coarse powder obtained by classifying the coarse particle dust collected by the cooling chamber 45, and can reduce a chlorine concentration to about 7000 ppm. About this dust, the chlorine concentration has fallen to such an extent that it can be directly used as a cement raw material.

  On the other hand, the one with the highest chlorine concentration is fine dust dust obtained by classifying fine dust collected by the bag filter 47, and the chlorine concentration can be increased to about 330000 ppm. About this dust, a chlorine compound can be efficiently removed from a cement baking equipment by solidifying using a cement solidifying material etc., and discarding after that.

[Conventional example]
Coarse-grain dust separated from the exhaust gas g extracted from the kiln bottom of the rotary kiln 1 using the cyclone classifier 5 and returned to the cement kiln 1 using the conventional chlorine bypass device shown in FIG. Fine particle dust obtained by separation using No. 7 was collected, and 50% passing particle size, chlorine concentration and yield were measured in the same manner as in Example 1.
These measurement results are shown in Table 4.

From these results, the chlorine concentration of the coarse dust separated by the cyclone classifier 5 was about 1/10 of the chlorine concentration of the fine dust collected by the dust collector 7. In general, it has already been found that the above ratio in the prior art is between 8 and 16%. This is in the same range as the result of Example 1.
However, the results in Table 4 show that in the conventional chlorine bypass device, the proportion of coarse dust separated using the cyclone classifier 5 is as high as 80% of the total, and even if the chlorine adhesion concentration is low, The amount of chlorine returned to the kiln 1 corresponds to 30% of the total amount of chlorine contained in the extracted gas.

  According to Examples 1 and 2, a part of the dust containing the chlorine compound contained in the exhaust gas extracted from the kiln bottom of the cement kiln is not returned to the cement kiln, and the treatment is performed outside the cement kiln system. Therefore, chlorine can be efficiently removed from the cement firing facility. Therefore, it is possible to make a compact device without excessively increasing the amount of treatment gas of the exhaust gas treatment device in the cement firing facility, minimizing the influence on the operation of the cement production facility, and high chlorine concentration Waste can also be used.

  Moreover, since the dust containing the obtained chlorine compound can be classified to obtain dust having an arbitrary chlorine concentration, it is possible to select an efficient treatment method of the dust and increase the choice of treatment methods. be able to. Therefore, it is possible to construct an efficient and large treatment system by combining the exhaust gas treatment device and the dust treatment method in the cement firing facility.

On the other hand, in the conventional example, all chlorine compounds contained in the extracted exhaust gas are not taken out from the kiln system, and 25 to 40% of chlorine is separated by a cyclone classifier and returned to the cement kiln. I understood.
Therefore, in the conventional example, the amount of dust taken out from the cement kiln system is small, and since the chlorine concentration of the dust to be treated is high, an efficient treatment method can be adopted without employing many treatment methods. On the other hand, it was found that the rate of chlorine emission outside the cement kiln system is small.
In order to obtain the same amount of dechlorination as that of the present embodiment in the conventional example, the extraction amount of 1.3 to 1.7 times is necessary, and the heat capacity of the kiln system accompanying the increase of the equipment capacity and the increase of the extraction gas is required. It turns out that there is a risk of deterioration.

It is a schematic diagram which shows the processing apparatus of the waste gas in the cement baking equipment of one Embodiment of this invention. It is a figure which shows the particle size distribution of all the dusts obtained with the processing apparatus of the waste gas of one Embodiment of this invention. It is a figure which shows the cumulative particle size distribution of all the dusts obtained with the processing apparatus of the waste gas of one Embodiment of this invention. It is a figure which shows the particle size distribution of each of coarse-grained dust and fine-grained dust of one Embodiment of this invention. It is a figure which shows the trump distribution rate (partial classification efficiency) in the cooling chamber of one Embodiment of this invention. It is a schematic diagram which shows an example of the conventional chlorine bypass device. It is a schematic diagram which shows an example of the conventional high extraction type chlorine bypass system.

Explanation of symbols

41 Cement kiln 42 Preheater rising duct 43 Probe 44 Cooling fan 45 Cooling chamber 46 Cooling fan 47 Bag filter 48 Suction fan 49 Dust silo 50 Classifier

Claims (9)

A method for treating exhaust gas in a cement firing facility for extracting a part of exhaust gas discharged from a cement kiln and removing chlorine compounds from the extracted exhaust gas,
A cooling step for cooling the extracted exhaust gas to a melting point or lower of the chlorine compound, a dust collection step for collecting dust contained in the cooled exhaust gas, and the collected dust for coarse particles and fine particles A method for treating exhaust gas in a cement firing facility, comprising: a classification step of classifying into dusts; and a treatment step of reusing or discarding each dust after classification. The dust collecting process includes a coarse dust collecting process for separating and collecting coarse dust contained in the cooled exhaust gas, and a residual dust for collecting residual dust excluding the coarse dust contained in the exhaust gas. Consisting of a collection process,
2. The classification step is a classification step of further classifying the coarse dust into a coarse powder and a fine powder, and the classified coarse powder is returned to the cement kiln as a cement raw material. Of exhaust gas in a cement firing facility.   In the cement baking equipment according to claim 1 or 2, wherein the classification particle size classified into the coarse powder and the fine powder in the classification step can be arbitrarily adjusted in a range of 5 µm or more and 60 µm or less. Exhaust gas treatment method.   The cement recycling equipment according to claim 1, 2 or 3, wherein the reuse is any one or more of addition to cement, reuse as cement raw material, and addition to cement-based solidifying agent. Of exhaust gas treatment in Japan.   5. The method for treating exhaust gas in a cement firing facility according to claim 4, wherein when the chlorine raw material is reused as the cement material, the adhering chlorine compound is removed by washing with water.   The cement according to any one of claims 1 to 5, wherein the discarding is performed after solidifying the dust, the fine particles, and the residual dust using a cement-based solidifying material. A method for treating exhaust gas in a firing facility. An exhaust gas treatment apparatus in a cement firing facility for extracting a part of exhaust gas discharged from a cement kiln and removing chlorine compounds from the extracted exhaust gas,
Extraction means for extracting a part of the exhaust gas discharged from the cement kiln, cooling means for cooling the extracted exhaust gas below the melting point of the chlorine compound, and dust for collecting dust contained in the cooled exhaust gas An exhaust gas treatment apparatus in a cement burning facility, comprising: a collecting means; and a classifying means for classifying the collected dust into coarse and fine particles. The dust collecting means includes a coarse dust collecting means for separating and collecting coarse dust contained in the cooled exhaust gas, and a residual dust for collecting residual dust excluding the coarse dust contained in the exhaust gas. Consisting of collection means,
The classification means comprises classification means for further classifying the coarse dust into a coarse powder and a fine powder,
8. The exhaust gas treatment apparatus in a cement firing facility according to claim 7, further comprising conveying means for returning the classified coarse powder to the cement kiln as a cement raw material.   The exhaust gas treatment apparatus in a cement burning facility according to claim 7 or 8, wherein an amount of exhaust gas extracted by the extraction means is 2% by volume or more of a total amount of exhaust gas discharged from the cement kiln.

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