JP5287881B2 - Method and apparatus for treating exhaust gas in cement firing facility - Google Patents

Description

  The present invention relates to a method and apparatus for treating exhaust gas in a cement firing facility, and more particularly, useful volatility such as halogens such as chlorine and bromine and / or halogen compounds from exhaust gas discharged from cement firing facilities. The present invention relates to a method and an apparatus for treating exhaust gas in a cement firing facility capable of collecting impurities and minimizing the influence on the operation of the cement firing facility.

In cement production facility, in accordance with the use of waste increases, halogen and / or halogen compounds such as chlorine or bromine, volatile impurities sulfur compounds such as SO _x are beginning to be brought more into the cement burning facility .
In particular, in recent years, waste plastics and the like have come to be used as an alternative fuel for cement firing facilities, but these waste plastics often contain bromine to impart flame retardancy, When this waste plastic is burned in a cement firing facility, bromine is generated, and as the amount of this waste plastic increases, bromine volatilized in the cement kiln also increases. The reason for this is that bromine is also concentrated in the cement firing facility like chlorine.
Therefore, in order to remove halogen and / or halogen compounds such as chlorine and bromine that are circulated and concentrated to a high concentration, a chlorine bypass device is generally attached to the cement firing equipment.

  FIG. 3 is a schematic diagram showing a cement manufacturing facility equipped with a conventional chlorine bypass device. In the figure, 1 is a cement raw material storage, 2 is a raw material mill for drying and pulverizing the cement raw material, and 3 is a cement raw material powder. 4 is a suspension preheater composed of multi-stage cyclones 4a to 4d, 5 is a calcining furnace, 6 is a cement kiln, 7 is a preheater rising duct (kiln bottom) connected to the cement kiln 6, and 8 is a cement kiln. 6 is a clinker cooler, 10 is an electric dust collector, 12 and 13 are exhaust chimneys, 14 is a suction fan (exhaust gas attracting means), 15 is a cooling fan, and 16 is a suction fan.

Also, 21 is a cement raw material supply line, 22 is a cement raw material powder supply line, 23 is a cement clinker conveying line, and 24 is a combustion for using cooling air discharged from the clinker cooler 9 as combustion air for the calciner 5. An air duct 25 is a suspension preheater exhaust gas line.
A chlorine bypass device 31 stores the probe 32 for extracting a part of the exhaust gas discharged from the cement kiln 6, the cooling chamber 33, the bag filter 34, and the dust from the cooling chamber 33 and the bag filter 34. The dust silo 35, the cooling fans 36 and 37, and the suction fan 38 are configured.

  In this cement manufacturing facility, volatile impurities such as chlorine are volatilized by being heated at a high temperature of 1000 ° C. or higher in the cement kiln 6, reaggregated by the suspension preheater 4, and the cement raw material in the cement kiln 6. By being brought in again, it is circulated and concentrated in the cement firing system. In particular, since halogens such as chlorine and bromine and / or halogen compounds have a high volatilization rate in the cement kiln 6, a circulation concentration ratio of 100 times or more with respect to the amount of halogen brought into the cement manufacturing facility from outside the system. Become. Therefore, the halogen and / or halogen compounds such as chlorine and bromine which are highly concentrated in the state of volatilization in the exhaust gas of the cement kiln 6 are cooled and aggregated by the chlorine bypass device 31 and removed from the system of the cement firing facility. The circulation concentration ratio is reduced.

On the other hand, there is a sulfur compound such as SO _{x as} a substance that circulates and concentrates similarly to chlorine and bromine.
Normally, sulfur reacts with lime and the like in the suspension preheater 4 and is present in the cement raw material as sulfate. The sulfate introduced into the cement kiln 6 is vaporized at 70 to 80% in a high temperature region in the cement kiln 6 and SO _x generated by combustion of sulfur contained in fuel such as powdered coal. At the same time, it is discharged from the cement kiln 6 in a high-concentration gas state. This SO _x of the vaporized gas state in the cement kiln 6 is fed into the suspension preheater 4, it is almost completely desulfurized reacted at this suspension preheater 4 and cement powder raw material. Thus, the exhaust gas discharged from a cement burning facility, and only a few ppm of the SO _x are present.

Thus, although the cement production facility shown in FIG. 3 is a facility where SO _x is almost completely desulfurized, the attached chlorine bypass device limits the environment in which desulfurization is performed in the device. The exhaust gas after extracting the exhaust gas with the preheater rising duct 7 connected to the cement kiln 6 and removing chlorine from the extracted exhaust gas may contain a considerable amount of SO _{x of} 300 to 2000 ppm. . Therefore, the exhaust gas containing a considerable amount of SO _x is returned again to the cement firing facility, and desulfurized using high-concentration cement raw material powder via the suspension preheater 4 to obtain exhaust gas not containing SOx. A treatment method for discharging to the atmosphere together with the exhaust gas to be discharged is adopted.
For example, an air-cooled extraction exhaust gas treatment device is connected to a cement firing facility, and dust containing volatile components is removed by a dust collector of the extraction exhaust gas treatment device. A cement raw material firing method used as fuel combustion air has been proposed (see Patent Document 1).

In addition, a part of the exhaust gas discharged from the cement kiln is extracted and simultaneously cooled to below the freezing point of the chlorine compound, and the coarse powder is separated from the cooled extracted gas and returned to the cement kiln. The gas is further cooled to recover the bypass dust from the extracted gas, and the extracted gas after recovering the bypass dust is passed through the region of the temperature of 800 to 1200 ° C. in the cement firing facility, thereby SO _x in the extracted gas. the method for reducing the chlorine bypass exhaust of the SO _x to reduce has been proposed (see Patent Document 2).
In these treatment methods, the returned exhaust gas is used as a combustion air in a cement firing system, so SO _x contained in the exhaust gas is desulfurized while passing through the suspension preheater. Therefore, SO _x in the exhaust gas discharged from the cement raw material firing system is maintained at several ppm or less.

Japanese Patent Laid-Open No. 10-330136 JP 2000-226241 A

However, in conventional cement production facilities, when recovering volatile impurities such as halogens such as chlorine and bromine and / or halogen compounds from exhaust gas discharged from cement firing facilities, the impact on the operation of cement firing facilities is significant. There was a problem.
For example, the exhaust gas from the chlorine bypass device 31 is mixed with a large amount of cooling air in addition to the combustion gas extracted from the kiln bottom 7 of the cement kiln 6. When this exhaust gas is introduced into the calcining furnace 5 or the combustion air duct 24 connected to the calcining furnace 5 for processing, the air contained in the exhaust gas is used as combustion air for fuel in the calcining furnace 5. However, no combustion gas is used.
The combustion air in the combustion air duct 24 connected to the calcining furnace is heated to 800 to 900 ° C. by the clinker cooler 9, but the temperature of the exhaust gas from the chlorine bypass device 31 is 100 to 150. The temperature is lower than that of the combustion air in the combustion air duct 24. Therefore, if a part of the combustion air introduced into the calcining furnace is replaced with the exhaust gas of the chlorine bypass device 31, the energy utilization efficiency of the cement firing equipment is extremely lowered.

As described above, the conventional cement manufacturing equipment has a large influence on the operation of the cement firing equipment, and it is economical due to a decrease in the firing capacity of the cement clinker and an increase in the heat consumption per unit clinker (heat intensity). There was a risk that operation would become impossible.
Moreover, when returning the exhaust gas of a chlorine bypass apparatus to the air intake port of a burner part, although energy utilization efficiency is not greatly inferior, all the exhaust gases of a chlorine bypass apparatus cannot be returned. Further, when the exhaust gas from the chlorine bypass device is returned to the air intake port of the clinker cooler, there is a problem that a long-distance gas processing path is required and the facility becomes large.

Moreover, in the conventional chlorine bypass device, a high temperature exhaust gas of 950 ° C. or higher extracted from the bottom of the kiln of the cement kiln needs to be cooled to 200 ° C. or lower, so a cooling device is required. Due to the need for high-performance dust collectors such as bag filters to collect the dust inside, the chlorine bypass device becomes complicated and large in size even though the amount of exhausted gas is small. was there.
In addition, bromine, which has increased in cement firing facilities in recent years, as well as chlorine, volatilizes in the cement kiln and then agglomerates and circulates and concentrates in a suspension pre-heater, enabling stable operation of cement firing facilities. There was a problem of adverse effects. In particular, since the temperature at which bromine volatilizes and aggregates is in a lower temperature range than chlorine, it is difficult to efficiently remove bromine from the exhaust gas in a conventional chlorine bypass device that extracts the exhaust gas at the kiln bottom of the cement kiln.
In this way, when treating exhaust gas containing halogen and / or halogen compounds such as chlorine and bromine discharged from cement production facilities, it has a small impact on the operation of cement production facilities and does not require large-scale facilities. A technology that can be processed in a simple manner has been demanded. Furthermore, a technique for efficiently removing bromine from exhaust gas has been demanded at the same time.

  The present invention has been made in order to solve the above-described problems, and has a small effect on the operation of cement production facilities, and it is a simple method that does not require large-scale facilities. An object of the present invention is to provide an exhaust gas treatment method and treatment apparatus in a cement firing facility capable of easily and efficiently removing volatile components such as benzene and bromine.

  In order to solve the above-mentioned problems, the present inventors examined the magnitude of the influence on the operation of cement production facilities due to the difference between the return destination of the exhaust gas and the gas temperature, gas amount, and gas properties in the conventional chlorine bypass device. As a result, the exhaust gas extracted from the exhaust gas generated in any one of the preheater for calcining the cement raw material and the cement kiln for calcining the calcined cement raw material is reduced to 600 ° C. to 700 ° C. or less of the melting point of the volatile component. The volatile component is attached to the dust contained in the exhaust gas to collect the dust in a high temperature state of 300 ° C. or higher, and the exhaust gas from which the dust has been removed is transferred to the preheater after the exhaust gas induction means. If this is done, it is possible to reduce the amount of cooling air introduced and minimize the impact on the operation of the cement production facility. It is possible to further, by selecting a location for extraction, found that it is possible to recover useful silver and / or halogen compounds such as bromine, and have completed the present invention.

  That is, the method for treating exhaust gas in the cement firing facility of the present invention is a cement that extracts a part of exhaust gas generated when firing cement raw material in the cement firing facility and removes volatile components from the extracted exhaust gas. A method for treating exhaust gas in a firing facility, wherein a preheater that pre-fires cement raw material, a cement kiln that fires the pre-fired cement raw material, and an extraction step of extracting a part of the exhaust gas discharged from one of them, A cooling step of reducing the extracted exhaust gas to a melting point of 600 ° C. to 700 ° C. or less of a volatile component contained in the exhaust gas, and attaching the volatile component to dust contained in the exhaust gas; A dust collecting step for collecting the dust to which the components are adhered in a high temperature state of 300 ° C. or higher, and an exhaust gas from which the dust has been removed An exhaust gas treatment process for returning the exhaust gas to the exhaust gas attraction means after the dust, and a dust circulation process for circulating and using the dust collected in the dust collection process as a cooling medium in the cooling process together with air for conveyance. It is characterized by that.

In this treatment method, the extracted exhaust gas is reduced to 600 ° C. to 700 ° C. or less, which is the melting point of the volatile component, the volatile component is adhered to the dust contained in the exhaust gas, and the dust to which the volatile component is adhered. Is collected in a high-temperature state of 300 ° C. or higher, whereby an increase in the amount of exhaust gas can be suppressed by removing volatile components at a high temperature.
After that, the exhaust gas from which the dust has been removed is returned to the preheater after the exhaust gas attracting means, so that the influence on the operation of the cement firing facility can be reduced.
In addition, since the increase in the amount of exhaust gas is suppressed, the exhaust gas treatment process can be reduced.
In addition, the dust collected in the dust collection process is circulated and used as a cooling medium in the cooling process together with the air for conveyance, so that the dust concentration in the high-temperature exhaust gas extracted from the cement firing facility is increased. It becomes possible to collect volatile components contained in the exhaust gas with high efficiency, and thus it is possible to reduce the amount of exhaust gas to be extracted.
Further, since the content of volatile components such as SO _x contained in the exhaust gas is reduced, it is possible to select an arbitrary treatment destination.

The extraction step is preferably a step of extracting a part of the exhaust gas from the kiln bottom of the cement kiln.
In this treatment method, it is possible to collect dust having a high content of volatile components such as chlorine and bromine by extracting a part of the exhaust gas from the bottom of the kiln of the cement kiln, and to collect exhaust gas at a higher temperature. It becomes possible to make the influence which it has on the operation of the cement baking equipment by bleeding smaller.

The extraction step is preferably a step of extracting a part of the exhaust gas from the lowermost cyclone of the preheater.
In this treatment method, by extracting a part of the exhaust gas from the lowermost cyclone of the preheater, it becomes possible to collect dust having a high content of volatile components such as bromine, and further to the exhaust gas of the lowermost cyclone. It is possible to reduce the influence of the extraction on the operation of the cement firing facility.

  The apparatus for treating exhaust gas in a cement firing facility of the present invention extracts a part of exhaust gas generated when firing a cement raw material in the cement firing facility and removes volatile components from the extracted exhaust gas. An exhaust gas treatment apparatus in which a preheater for calcining cement raw material, a cement kiln for calcining the calcined cement raw material, an extraction means for extracting a part of the exhaust gas discharged from the preheater, and this extraction air Cooling means for lowering the exhausted gas to 600 ° C. to 700 ° C. or lower of the melting point of the volatile component contained in the exhaust gas, and attaching the volatile component to the dust contained in the exhaust gas, Dust collecting means for collecting adhering dust in a high temperature state of 300 ° C. or higher, and exhaust gas from which the dust has been removed is discharged from the preheater. Exhaust gas treatment means for returning to the after-attraction means, and dust circulation means for circulating and using the dust collected by the dust collection means as a cooling medium for the cooling means together with air for conveyance. And

In this processing apparatus, the exhaust gas extracted by the cooling means is lowered to 600 ° C. to 700 ° C. or less, which is the melting point of the volatile component, and this volatile component is adhered to the dust contained in the exhaust gas, and then dust trapping is performed. By collecting the dust to which the volatile component adheres in a high temperature state of 300 ° C. or higher by the collecting means, it is possible to suppress an increase in the amount of exhaust gas. Therefore, the influence on the operation of the cement firing facility can be reduced.
Furthermore, since an increase in the amount of exhaust gas is suppressed, it is possible to reduce the size of the exhaust gas treatment device. Therefore, it becomes possible to remove volatile components from the exhaust gas of the cement baking equipment at low cost.

In addition, the dust collected by the dust collecting means by the dust circulating means is circulated and used as a cooling medium for the cooling means together with the air for conveyance, thereby increasing the dust concentration in the high-temperature exhaust gas extracted from the cement firing facility. Thus, it becomes possible to collect volatile components contained in the high-temperature exhaust gas with high efficiency, and therefore it is possible to reduce the amount of exhaust gas extracted by the extraction means.
In addition, since the content of volatile components such as SO _x contained in the exhaust gas is reduced, it is possible to select an arbitrary treatment destination.

According to the exhaust gas treatment method in the cement firing facility of the present invention, a part of the exhaust gas discharged from either the preheater for calcining the cement raw material or the cement kiln for calcining the calcined cement raw material is extracted. An extraction step, and a cooling step of reducing the extracted exhaust gas to 600 ° C. to 700 ° C. or lower of the melting point of the volatile component contained in the exhaust gas, and attaching the volatile component to the dust contained in the exhaust gas. A dust collecting step for collecting the dust to which the volatile component is adhered in a high temperature state of 300 ° C. or higher; an exhaust gas treatment step for returning the exhaust gas from which the dust has been removed to the exhaust gas attraction means of the preheater; A dust circulation step for circulating and using the dust collected in the dust collection step as a cooling medium for the cooling step together with the air for conveyance. , It is possible to suppress the increase in the amount of exhaust gas, it is possible to remove volatile components at an elevated temperature.
Thereafter, the exhaust gas from which the dust has been removed is returned to the preheater after the exhaust gas attracting means, so that the influence on the operation of the cement firing facility can be reduced.
Furthermore, since the increase in the amount of exhaust gas is suppressed, the exhaust gas treatment process can be reduced.

According to the exhaust gas treatment apparatus in the cement firing facility of the present invention, a part of the exhaust gas discharged from either the preheater for calcining the cement raw material or the cement kiln for firing the calcined cement raw material is extracted. Extraction means, cooling means for reducing the extracted exhaust gas to 600 ° C. to 700 ° C. or less of the melting point of the volatile component contained in the exhaust gas, and attaching the volatile component to the dust contained in the exhaust gas; A dust collecting means for collecting the dust to which the volatile component is adhered in a high temperature state of 300 ° C. or higher; an exhaust gas treatment means for returning the exhaust gas from which the dust has been removed to the exhaust gas attraction means of the preheater; and A dust circulating means for circulating and using the dust collected by the dust collecting means as a cooling medium for the cooling means together with the air for conveyance. , It is possible to suppress the increase in the amount of exhaust gas, it is possible to remove volatile components at an elevated temperature.
Thereafter, the exhaust gas from which dust has been removed is returned to the preheater after the exhaust gas attraction means using the exhaust gas treatment means, so that the influence on the operation of the cement firing facility can be reduced.
Furthermore, since the increase in the amount of exhaust gas is suppressed, the exhaust gas treatment device can be downsized, and as a result, volatile components can be removed from the exhaust gas of the cement firing facility at low cost.

It is a schematic diagram which shows the waste gas processing apparatus in the cement manufacturing equipment of the 1st Embodiment of this invention. It is a schematic diagram which shows the waste gas processing apparatus in the cement manufacturing equipment of the 2nd Embodiment of this invention. It is a schematic diagram which shows the cement manufacturing equipment which attached the conventional chlorine bypass apparatus.

The form for implementing the processing method and processing apparatus of the waste gas in the cement manufacturing equipment of this invention is demonstrated based on drawing.
Note that this embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

“First Embodiment”
FIG. 1 is a schematic diagram showing an exhaust gas treatment apparatus in a cement production facility according to a first embodiment of the present invention. A part of the generated exhaust gas is extracted by a preheater rising duct, and the extracted exhaust gas is The melting point of the volatile component contained therein is lowered to 600 ° C. to 700 ° C. or less, and the dust to which the volatile component is attached is collected in a high temperature state of 300 ° C. or more, and the exhaust gas from which the dust is removed It is an example of the processing apparatus of the waste gas returned to a suspension preheater. In FIG. 1, the same components as those in FIG. 3 are denoted by the same reference numerals.

  In the figure, 41 is an exhaust gas treatment apparatus attached to a cement manufacturing facility, and the exhaust gas discharged from the preheater rising duct 7 is inserted into the preheater rising duct (kiln bottom) 7 connected to the cement kiln 6. A probe (bleeding means) 42 for extracting a part of the air and air used as cooling air for cooling the exhausted gas extracted together with the air for conveying the circulating dust are blown, and this exhaust gas is a volatile component contained therein. A cooling fan (cooling means) 43 for lowering the melting point of the halogen element and / or halogen compound such as bromine and chlorine to 600 ° C. to 700 ° C., and the halogen element such as bromine and chlorine in the extracted exhaust gas and / or Or cyclone type dust that separates and collects dust with halogen compounds attached at a high temperature of 300 ° C or higher A collection device (dust collection means) 44, an exhaust gas line (exhaust gas treatment means) 45 for returning the exhaust gas from which dust has been removed to the suspension preheater exhaust gas line 25, and dust collected by the dust collection device 44 A circulating dust air transporting device (dust circulating means) 46 which is supplied again to the probe 42 by the conveying air blown from the cooling fan 43 and circulated, a circulating dust supply line 47, a halogen element such as bromine and chlorine, and / or Or it is comprised with the dust silo 48 which stores the dust to which the halogen compound adhered.

Next, a method for treating exhaust gas using the exhaust gas treatment device 41 will be described.
(Bleeding process)
In this step, a part of the exhaust gas discharged from the preheater rising duct 7 connected to the cement kiln 6 is extracted using the probe 42.
This exhaust gas, other dust, halogen and / or halogen compounds of chlorine and bromine which are volatile components, contains sulfur compounds such as SO _x.

(Cooling process)
The dust collected by the dust collecting device 44 is supplied again to the probe 42 by the circulating dust air transport device 46 together with the conveying air blown from the cooling fan 43, and is extracted using the dust and the conveying air. The exhaust gas is reduced to 600 ° C. to 700 ° C. or less of the melting point of the halogen element and / or halogen compound such as bromine and chlorine contained in the exhaust gas, and the halogen element and / or halogen compound such as bromine and chlorine is exhausted. It is a process of adhering to the dust inside.

For example, if the main component of the bromine compound is KBr, the melting point of KBr is 730 ° C., so the melting point is lowered to 600 ° C. to 700 ° C. or less. Thereby, the bromine compound contained in the exhaust gas is deposited and adheres to the surface of the dust in the exhaust gas, and at the same time, the collection rate of the bromine compound is increased by increasing the amount of dust in the exhaust gas.
Similarly, the collection efficiency of sulfur compounds contained in the extracted exhaust gas can be increased by increasing the dust concentration in the exhaust gas. Therefore, it becomes possible to reduce the SOx concentration in the exhaust gas. In addition, since the exhaust gas treatment does not necessarily require a high temperature treatment, it can be introduced into the suspension preheater exhaust gas line 25 to be described later.

(Dust collection process)
The dust collecting device 44 separates and collects the dust to which the halogen element such as bromine and chlorine and / or the halogen compound is attached in a high temperature state of 300 ° C. or higher.
The dust collector 44 separates and collects the dust to which the halogen element such as bromine and chlorine and / or the halogen compound is attached in a high temperature state of 300 ° C. or more, conveys it to the dust silo 48 and stores it. A part of the air is conveyed to the circulating dust air transport device 46.

(Dust circulation process)
In the circulating dust air transport device 46, the dust to which halogen elements such as bromine and chlorine and / or halogen compounds are transported from the dust collecting device 44 is supplied together with the transporting and cooling air from the cooling fan 43. It is conveyed to the probe 42 via the line 47 and circulated and used as a cooling medium for the extracted exhaust gas.
Thus, since dust collected by the dust collector 44 is circulated and supplied to the probe 42, the dust concentration in the extracted exhaust gas is increased, and halogen elements such as bromine and chlorine and / or halogens are used. It is possible to increase the collection efficiency of the compound.

(Exhaust gas treatment process)
This is a step of returning the exhaust gas from which dust is separated and collected by the dust collecting device 44 to the suspension preheater exhaust gas line 25 via the exhaust gas line 45.
The exhaust gas from which the dust has been removed is supplied to the raw material mill 2 for drying and pulverizing the cement raw material via the suspension preheater exhaust gas line 25 and the suction fan 14 and processed.

  In this process, by using the cyclone type dust collecting device 44, it becomes possible to collect dust at a high temperature, and the exhaust gas from which the dust has been removed is introduced into a predetermined portion of the suspension preheater 4 for processing. Even in such a case, it is possible to perform processing without greatly increasing the flow rate of the exhaust gas while keeping the temperature of the extracted exhaust gas high. Therefore, the influence exerted on the operation of the cement firing facility by introducing the exhaust gas can be reduced.

As described above, by circulating and using about 50% of the cooling air with respect to the amount of exhaust gas to be extracted and the dust collected by the dust collector 44, the extracted exhaust gas is converted into bromine or chlorine contained in the exhaust gas. Since the halogen element and / or halogen compound is reduced by reducing the melting point of the halogen element and / or halogen compound to 600 ° C. to 700 ° C. or less, and the sulfur compound such as SO _x is simultaneously desulfurized, this exhaust gas Can be introduced into the suspension preheater exhaust gas line 25 for processing.
Therefore, even when a gas larger than the amount of gas extracted by the conventional chlorine bypass device is extracted from the preheater rising duct 7, the influence on the operation of the cement firing facility is about 1/5 to 1/2 of the conventional device. Can be reduced.

In general, in the conventional chlorine bypass device as shown in FIG. 3, there are two types of heat loss (A) and (B) described below as influences on the calorific value for burning cement clinker.
(A) Loss heat lost to extract hot gas from the bottom of the cement kiln kiln.
(B) Heat loss due to a decrease in temperature of combustion air in order to use the cooled exhaust gas of the chlorine bypass device as combustion air in a calcining furnace.
Of these heat losses, it is generally known that the effect of the heat loss of (B) on the cement clinker calorific intensity is equivalent to 5 to 12 times the effect of the heat loss of (A) on the energy intensity. It has been.
Moreover, the cement clinker firing ability may be lowered due to the influence of the heat loss (B) on the operation of the cement firing apparatus.

In general cement firing equipment, the influence of introducing low-temperature air as high-temperature fuel combustion air for cement firing equipment depends on the preheater rising duct (kiln bottom) connected to the cement kiln. In many cases, it becomes larger than the influence due to the extraction of the high-temperature combustion gas of the same gas amount at the outlet of the lowermost cyclone 4d.
In the conventional chlorine bypass device, since the collection efficiency of halogen compounds such as chlorine was considered first, about 2% hot gas (about 1000 ° C) was extracted from the preheater rising duct of the cement kiln. After introducing the cooling air amount 5 to 10 times the amount of exhaust gas to be collected into the device and collecting dust, the exhaust gas is introduced into the fuel combustion air duct of the calciner and treated, but the cement clinker is fired. About the calorific value, an increase of about 1.5 to 2.5% is observed, and the influence on the operation of the cement burning equipment is large.

  The present embodiment eliminates the drawbacks of the conventional chlorine bypass device, and even when 2% or more of high-temperature gas is extracted from the preheater rising duct 7, the influence on the operation of the cement firing facility is conventionally increased. It can be reduced to about 1/5 to 1/2 of the apparatus.

“Second Embodiment”
FIG. 2 is a schematic diagram showing an exhaust gas treatment device in a cement production facility according to a second embodiment of the present invention, and an exhaust gas treatment device 51 of the present embodiment is different from the exhaust gas treatment device 41 of the first embodiment. The point is that in the exhaust gas treatment device 41 of the first embodiment, a part of the exhaust gas discharged from the preheater rising duct 7 is extracted using the probe 42, and further dust is separated and collected by the dust collection device 44. The exhaust gas that has been removed is returned to the suspension preheater exhaust gas line 25 via the exhaust gas line 45, whereas in the exhaust gas treatment device 51 of the present embodiment, the exhaust gas is discharged from the outlet of the lowermost cyclone 4 d of the suspension preheater 4. A part of the exhaust gas is extracted using the probe 42, and the dust is separated and collected by the dust collecting device 44 and removed. The exhaust gas is that is returned to the suction fan 14 and subsequent suspension preheater exhaust gas line 25 via the exhaust gas line 52 and the suction fan 53.

In the exhaust gas treatment device 51, since the exhaust gas extraction position is the outlet of the lowermost cyclone 4d, the concentration ratio of the bromine compound to the chlorine compound in the obtained dust can be increased.
Further, the SO _x generated in the cement kiln 6 and the calcining furnace 5 is desulfurized by the cement raw material calcined in the lowermost cyclone 4d, so that the amount of SO _x contained in the extracted exhaust gas is small. . As a result, exhaust gas can be introduced into the suspension preheater exhaust gas line 25 after the induction fan 14 and used as a heat source for the raw material mill 2 for drying and grinding the subsequent cement raw material.

Further, in the exhaust gas extracted from the outlet of the lowermost cyclone 4d, the content (concentration) of chlorine and / or chlorine compound is 1/3 to 1/4 as compared with the exhaust gas from the preheater rising duct 7. On the other hand, the content of bromine and / or bromine compounds is often the same.
In the exhaust gas treatment device 51, the exhaust gas from which dust has been separated and collected has a higher bromine compound concentration ratio relative to the chlorine compound concentration than the exhaust gas from the preheater rising duct 7, and therefore bromine in the exhaust gas. And / or bromine compounds can be selected and collected.

DESCRIPTION OF SYMBOLS 4 Subsidence preheater 4a-4d Cyclone 5 Calcining furnace 6 Cement kiln 7 Preheater rising duct 8 Burner 9 Clinker cooler 14 Suction fan 15 Cooling fan 23 Cement clinker conveyance line 24 Combustion air duct 25 Suspension preheater exhaust gas line 41 Exhaust gas treatment device 42 Probe 43 Cooling fan 44 Dust collecting device 45 Exhaust gas line 46 Circulating dust air transport device 47 Circulating dust supply line 48 Dust silo 51 Exhaust gas treatment device 52 Exhaust gas line 53 Suction fan

Claims (4)

A method for treating exhaust gas in a cement firing facility that extracts a part of exhaust gas generated when firing a cement raw material in a cement firing facility and removes volatile components from the extracted exhaust gas,
An extraction process for extracting a part of exhaust gas discharged from any one of a preheater for calcining the cement material and a cement kiln for calcining the calcined cement material;
A cooling step of reducing the extracted exhaust gas to 600 ° C. to 700 ° C. or less of a melting point of a volatile component contained in the exhaust gas, and attaching the volatile component to dust contained in the exhaust gas;
A dust collecting step of collecting the dust to which the volatile component is adhered in a high temperature state of 300 ° C. or higher;
An exhaust gas treatment process for returning the exhaust gas from which the dust has been removed to the exhaust gas induction means of the pre-heater, and
A dust circulation step in which the dust collected in the dust collection step is circulated and used as a cooling medium in the cooling step together with air for conveyance;
A method for treating exhaust gas in a cement firing facility, comprising:   The method for treating exhaust gas in a cement firing facility according to claim 1, wherein the extraction step is a step of extracting a part of the exhaust gas from the kiln bottom of the cement kiln.   The method for treating exhaust gas in a cement firing facility according to claim 1, wherein the extraction step is a step of extracting a part of the exhaust gas from a cyclone at the lowest stage of the preheater. An exhaust gas treatment apparatus in a cement firing facility for extracting a part of exhaust gas generated when firing a cement raw material in a cement firing facility and removing volatile components from the extracted exhaust gas,
An extraction means for extracting a part of exhaust gas discharged from any one of a preheater for calcining the cement raw material and a cement kiln for calcining the calcined cement raw material;
A cooling means for reducing the extracted exhaust gas to 600 ° C. to 700 ° C. or less of the melting point of the volatile component contained in the exhaust gas, and attaching the volatile component to the dust contained in the exhaust gas;
Dust collecting means for collecting the dust to which the volatile component is adhered in a high temperature state of 300 ° C. or higher;
Exhaust gas treatment means for returning the exhaust gas from which the dust has been removed to the exhaust gas induction means after the preheater, and
A dust circulating means for circulating and using the dust collected by the dust collecting means as a cooling medium of the cooling means together with air for conveyance;
An exhaust gas treatment apparatus in a cement firing facility, comprising:

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