JP5868729B2 - Chlorine bypass exhaust gas treatment device and treatment method - Google Patents

Description

  The present invention relates to an apparatus and a method for treating a gas discharged from a chlorine bypass system for extracting a part of combustion gas and removing chlorine from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone. About.

  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.

  The chlorine bypass system is, for example, as described in Patent Document 1, after cooling the extracted combustion gas, the dust in the combustion gas is separated into coarse powder and fine powder by a classifier, and separated chlorine This equipment collects fine powder (chlorine bypass dust) that contains a large amount of water (potassium chloride / KCl).

  In this type of chlorine bypass system, for example, as shown in FIG. 3, the combustion gas G extracted from the kiln exhaust gas passage from the bottom of the kiln 21 to the lowermost cyclone (not shown) is The probe 22 is cooled by cold air (atmosphere) from the cooling fan 23, and the extracted gas G1 from the probe 22 is introduced into the cyclone 24 and separated into coarse powder D1 and exhaust gas G2 containing fine powder D2.

  The coarse powder D1 is returned to the cement kiln system, while the fine powder D2 and the exhaust gas G2 are cooled to 150 ° C. to 250 ° C. by the cool air from the cooling fan 26 in the cooler 25 and then introduced into the bag filter 27. . In the bag filter 27, the fine powder D2 is collected, and the fine powder (chlorine bypass dust) D2 collected in the dust tank 28 together with the dust collected from the cooler 25 is added to the cement grinding mill system. On the other hand, the exhaust gas G3 from the bag filter 27 is returned to the preheater attached to the cement kiln 21 via the exhaust fan 29 or the outlet side of the attracting fan installed downstream of the preheater.

International Publication No. 97/21638 Pamphlet

  However, in the chlorine bypass system 20, in order to rapidly cool the high-temperature combustion gas G extracted from the cement kiln 21, cold air having an amount 3 to 4 times the amount of extracted gas is injected from the cooling fan 23. Therefore, the air volume (amount of exhaust gas G3) at the outlet of the chlorine bypass system 20 is 4 to 5 times the extraction air volume (amount of extracted combustion gas G).

  The exhaust gas from the chlorine bypass system 20 (hereinafter referred to as “chlorine bypass exhaust gas”) G3 is finally returned to the kiln firing system. For example, when returning to the preheater attached to the cement kiln 21, Since it is necessary to raise the temperature of the exhaust gas G3 at about 850 ° C. to 850 ° C. to 1100 ° C., a large heat loss occurs. Further, when the preheater is returned to the outlet side of the fan that attracts exhaust gas, the heat loss is small, but the unit of air volume at the outlet of the subsequent electrostatic precipitator or bag filter increases by about 10%. Therefore, returning the exhaust gas G3 from the chlorine bypass system 20 to the kiln firing system has caused a decrease in the production amount of cement clinker by the cement kiln 21, a deterioration in fuel consumption, and an increase in power consumption.

  Then, this invention is made | formed in view of the problem in the said prior art, Comprising: It aims at processing a chlorine bypass waste gas, suppressing the influence on a cement clinker production amount, a fuel consumption, and power consumption small. .

In order to achieve the above object, the present invention is configured to extract air while cooling a part of the combustion gas from the kiln exhaust gas passage from the bottom of the kiln of the cement kiln to the lowermost cyclone, and dry the chlorine bypass dust from the extracted gas. A device for treating the dust collector outlet gas after collecting the chlorine bypass dust, which is discharged from the chlorine bypass system for collecting the dust, and a cooling device for cooling the dust collector outlet gas after collecting the chlorine bypass dust; A circulation route for returning 75% or more and 80% or less of the dust collector outlet gas cooled by the cooling device to the probe for extracting while cooling a part of the combustion gas, and the remainder of the dust collector outlet gas cooled by the cooling device , said cement kiln to attached the preheater, or an exhaust fan back to the outlet side of the induction fan disposed downstream of the preheater Characterized in that it obtain.

  And according to the present invention, the amount of chlorine bypass exhaust gas returned to the kiln firing system can be reduced by cooling the extracted gas after collecting the dust by the cooling device and returning it to the probe via the circulation route. it can. Thereby, compared with the cement kiln in which the conventional chlorine bypass is installed, the influence on the cement clinker production amount, the fuel consumption, and the power consumption can be suppressed.

In addition to the above, according to the present invention, by returning most of the dust collector outlet gas after collecting the dust to the probe, the O ₂ concentration, for example, the O ₂ concentration is as low as 3 to 4%. The extraction gas is cooled with a gas having an oxygen concentration. In other words, since the O ₂ concentration of the gas in the chlorine bypass system is as low as 3 to 4%, the oxychlorination reaction is suppressed and the production of harmful organic chlorine compounds such as dioxins is effectively prevented. Can do.

  In the chlorine bypass exhaust gas treatment apparatus, the cooling device may be a heat exchanger that performs heat exchange between the dust collector outlet gas after collecting the dust and the low temperature gas.

In the chlorine bypass exhaust gas treatment apparatus, the cooling device may be a gas cleaning tower that sprays water onto the dust collector outlet gas after collecting the dust to wash the dust collector outlet gas. This absorbs or recovers chlorine components that have passed through the dust collector, improves chlorine removal efficiency, and in the gas extracted by adding hydroxides, carbonates, etc. of alkaline components such as calcium, magnesium, and sodium. The dust collector outlet gas can be cooled while desulfurizing the SO ₂ .

Further, the present invention provides a chlorine bypass for extracting a portion of combustion gas from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a lowermost cyclone while cooling, and recovering chlorine bypass dust from the extracted gas in a dry manner. A method for treating a dust collector outlet gas discharged from a system after recovering the chlorine bypass dust, wherein the dust collector outlet gas after recovering the chlorine bypass dust is cooled, and 75 of the cooled dust collector outlet gas is recovered. % To 80% or less for cooling the extracted combustion gas, and the remaining part of the cooled dust collector outlet gas is a preheater attached to the cement kiln, or an induction fan installed downstream of the preheater. It returns to the exit side . According to the present invention, similarly to the above-described invention, by reducing the amount of chlorine bypass exhaust gas, the chlorine bypass exhaust gas is suppressed while minimizing the influence on the clinker production amount, fuel consumption and power consumption of the cement kiln to which the chlorine bypass exhaust gas is returned. Can be treated, the oxychlorination reaction can be suppressed, and the production of dioxins can be effectively prevented.

  In the chlorine bypass exhaust gas treatment method, the dust collector outlet gas after collecting the dust can be cooled to 15 ° C. or more and 60 ° C. or less and used for cooling the extracted combustion exhaust gas. When the dust collector outlet gas after collecting the dust is cooled to 15 ° C or lower, the cooling efficiency in cooling the dust collector outlet gas deteriorates, and in cooling to 60 ° C or higher, a part of the combustion gas is cooled from the kiln exhaust gas flow path. This is not preferable because the amount of the low-temperature gas to be increased increases or the cooling to the desired temperature is impossible.

  As described above, according to the present invention, it is possible to treat chlorine bypass exhaust gas while minimizing the influence on cement clinker production, fuel consumption and power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows the chlorine bypass system provided with 1st Embodiment of the processing apparatus of the chlorine bypass exhaust gas which concerns on this invention. It is a whole block diagram which shows the chlorine bypass system provided with 2nd Embodiment of the processing apparatus of the chlorine bypass exhaust gas which concerns on this invention. It is a whole block diagram which shows an example of the conventional chlorine bypass system.

  Next, modes for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a chlorine bypass system including a first embodiment of a chlorine bypass exhaust gas treatment apparatus according to the present invention. The chlorine bypass system 1 is a dry chlorine bypass system, and is a kiln bottom of a cement kiln 2. The probe 3 that cools the combustion gas G from the kiln exhaust gas flow path from the first to the lowest cyclone (not shown) while cooling with the low-temperature gas, the extraction gas G1 from the probe 3 includes the coarse powder D1 and the fine powder D2. A cyclone 4 as a classifier that separates into exhaust gas G2, a first cooler 5 that cools the exhaust gas G2 containing fine powder D2 from the cyclone 4 with cold air from the cooling fan 6, and exhaust gas discharged from the first cooler 5 A bag filter 7 that collects the fine powder D2 from G2 and a dust filter 2 that stores the fine powder D2 from the bag filter 7 together with the dust collected from the first cooler 5. A second cooler (heat exchanger) 10 that cools the exhaust gas G3 discharged from the tank 8 and the bag filter 7 with cold air from the cooling fan 9, and an exhaust gas G4 that is a part of the exhaust gas of the second cooler 10. The preheater attached to the cement kiln 2, the exhaust fan 11 for returning to the outlet side of the induction fan installed downstream of the preheater, and the remaining exhaust gas G5 discharged from the second cooler 10 are returned to the probe 3. And a circulation route 12.

  Next, the operation of the chlorine bypass system 1 will be described with reference to FIG.

  The exhaust gas G5 returned from the second cooler 10 through the circulation route 12 while extracting the combustion gas G from the kiln exhaust gas flow path from the bottom of the kiln 2 of the cement kiln 2 to the lowermost cyclone, Rapid cooling to 700 ° C. or lower, which is the melting point of the chlorine compound. Next, in the cyclone 4, the extracted gas G1 exhausted from the probe 3 is separated into the coarse powder D1 and the exhaust gas G2 containing the fine powder D2, and the coarse powder D1 is returned to the cement kiln system.

  On the other hand, the fine powder D2 and the exhaust gas G2 are cooled to 150 ° C. to 250 ° C. by the cool air from the cooling fan 6 in the first cooler 5 and then introduced into the bag filter 7. In the bag filter 7, the fine powder D2 is collected, and the fine powder (chlorine bypass dust) D2 collected in the dust tank 8 together with the dust collected from the first cooler 5 is discharged out of the cement firing process and processed. .

  The exhaust gas G3 discharged from the bag filter 7 is cooled to 15 ° C. to 60 ° C. by the cool air from the cooling fan 9 in the second cooler 10, and the exhaust gas G4 which is a part of the exhaust gas of the second cooler 10 is exhausted to the exhaust fan. 11 is returned to the outlet side of the preheater attached to the cement kiln 2 and the induction fan installed downstream of the preheater. Further, the remaining exhaust gas G5 of the second cooler 10 is returned to the probe 3 via the circulation route 12 and used for cooling the combustion gas G. Here, the ratio of the air volume of the exhaust gas G4 and the exhaust gas G5 is set to 1: 3-4.

  As described above, according to the present embodiment, the exhaust gas G3 is cooled by the second cooler 10, and the exhaust gas G5 is returned to the probe 3 via the circulation route 12, so that the amount of the exhaust gas G4 is extracted. Same amount as G. As a result, when the exhaust gas G4 is returned to the preheater attached to the cement kiln 2, it is necessary to raise the temperature of the exhaust gas G4. Can be greatly reduced. Further, when the exhaust gas G4 is returned to the outlet side of the attracting fan installed on the downstream side of the preheater, the unit of air volume at the outlet of the subsequent electric dust collector or bag filter is not increased. Therefore, even if the exhaust gas G4 is returned from the chlorine bypass system 1 to the kiln firing system, it is possible to suppress a decrease in the production amount of cement clinker by the cement kiln 2, a deterioration in fuel consumption, and an increase in power consumption.

Further, according to the present embodiment, by returning the exhaust gas G5 to the probe 3, the kiln exhaust gas G is cooled with a gas having an O ₂ concentration of about 3 to 4%, so that the oxychlorination reaction is suppressed. The production of dioxins can be effectively prevented.

  Next, a second embodiment of the chlorine bypass exhaust gas treatment apparatus according to the present invention will be described with reference to FIG.

  The chlorine bypass system 15 provided with this chlorine bypass exhaust gas treatment device includes a gas cleaning tower 16 instead of the cooling fan 9 and the second cooler 10 of the chlorine bypass system 1 shown in FIG. This is the same as the chlorine bypass system 1 in the first embodiment.

The gas cleaning tower 16 is provided for spraying water W onto the exhaust gas G3 having a temperature of about 150 ° C. to 250 ° C. discharged from the bag filter 7 to cool it to 15 ° C. to 60 ° C. and cleaning the exhaust gas G3. By spraying water W onto the exhaust gas G3, it absorbs or recovers chlorine components, operation-inhibiting components, and harmful components that have passed through the dust collector, improving chlorine removal efficiency, and hydroxylating alkaline components such as calcium, magnesium, and sodium. The exhaust gas G3 can be cooled while desulfurizing SO ₂ contained in the exhaust gas G3 by adding substances, carbonates and the like. Other operations of the chlorine bypass system 15 are the same as those of the chlorine bypass system 1, and also in the present embodiment, as in the first embodiment, a decrease in the production amount of cement clinker by the cement kiln 2, deterioration of fuel consumption, and The increase in power consumption can be kept small.

DESCRIPTION OF SYMBOLS 1 Chlorine bypass system 2 Cement kiln 3 Probe 4 Cyclone 5 1st cooler 6 Cooling fan 7 Bag filter 8 Dust tank 9 Cooling fan 10 2nd cooler 11 Exhaust fan 12 Circulation route 15 Chlorine bypass system 16 Gas washing tower D1 Coarse powder D2 Fine powder G Combustion gas G1 Extraction gas G2 to G5 Exhaust gas

Claims (5)

Extracting while cooling a part of the combustion gas from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the lowermost cyclone, and exhausting it from the chlorine bypass system that collects chlorine bypass dust dry from the extracted gas, A device for treating a dust collector outlet gas after collecting the chlorine bypass dust,
A cooling device for cooling the dust collector outlet gas after recovering the chlorine bypass dust;
A circulation route for returning 75% or more and 80% or less of the dust collector outlet gas cooled by the cooling device to a probe that bleeds while cooling a part of the combustion gas ;
An exhaust fan that returns the remaining portion of the dust collector outlet gas cooled by the cooling device to a preheater attached to the cement kiln or an outlet side of an induction fan installed on the downstream side of the preheater is provided. Chlorine bypass exhaust gas treatment equipment.   2. The chlorine bypass exhaust gas treatment device according to claim 1, wherein the cooling device is a heat exchanger that performs heat exchange between a dust collector outlet gas after collecting the dust and a low-temperature gas.   2. The chlorine bypass exhaust gas treatment device according to claim 1, wherein the cooling device is a gas cleaning tower that sprays water onto a dust collector outlet gas after collecting the dust to wash the extracted gas. Extracting while cooling a part of the combustion gas from the kiln exhaust gas flow path from the bottom of the kiln of the cement kiln to the lowermost cyclone, and exhausting it from the chlorine bypass system that collects chlorine bypass dust dry from the extracted gas, A method of treating a dust collector outlet gas after collecting the chlorine bypass dust,
Cooling the dust collector outlet gas after collecting the chlorine bypass dust,
75% to 80% of the cooled dust collector outlet gas is used for cooling the extracted combustion gas ,
A method for treating a chlorine bypass exhaust gas , wherein the remaining portion of the cooled dust collector outlet gas is returned to the outlet side of a preheater attached to the cement kiln or an induction fan installed downstream of the preheater .   The method for treating a chlorine bypass exhaust gas according to claim 4, wherein the dust collector outlet gas after collecting the dust is cooled to 15 ° C or more and 60 ° C or less.

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