JP6066193B2 - Cement kiln exhaust gas treatment apparatus and treatment method - Google Patents

Description

  The present invention relates to an apparatus and a method for removing mercury from combustion exhaust gas discharged from a cement kiln constituting a cement firing facility.

  Since natural materials such as limestone, which is the main raw material for cement, and a wide variety of recycled resources such as fly ash contain mercury, the exhaust gas from cement kiln contains trace amounts of metallic mercury (Hg). . In the future, recycling of wastes as cement raw materials and fuels will be promoted, and as the amount of waste processing increases, the mercury concentration in the cement kiln exhaust gas may increase.

  However, it is extremely difficult to remove the mercury contained in the exhaust gas of the cement kiln at a low concentration from a large amount of exhaust gas, and if the mercury in the exhaust gas of the cement kiln increases, there is a risk of causing air pollution, There is also a risk of hindering the expansion of the use of recycled resources such as fly ash.

  Therefore, Patent Document 1 discloses a dust collector that collects dust contained in cement kiln exhaust gas, a heating device that heats the dust collected by the dust collector and volatilizes mercury in the dust, and a heating device. Cement comprising a solid-gas separation device comprising a ceramic filter for solid-gas separation of exhaust gas containing dust discharged from the gas, and a mercury recovery device for collecting mercury present on the gas phase side of the gas separated by the solid-gas separation device A kiln exhaust gas treatment device is described.

  Patent Document 2 discloses a dust collector that collects dust contained in exhaust gas from a cement kiln, and an extractor that volatilizes mercury by heating the dust with the heat of exhaust gas discharged from a clinker cooler in a cement firing facility. A cement kiln exhaust gas treatment apparatus comprising a duct, a solid-gas separation device that separates dust and gas discharged from the extraction duct, and an activated carbon adsorption tower that collects mercury contained in the gas discharged from the solid-gas separation device. Have been described.

JP 2010-116283 A JP 2011-88770 A

  However, in the cement kiln exhaust gas treatment apparatus described in Patent Documents 1 and 2, a heating device for heating the dust collected by the dust collector and a gas discharged from the solid-gas separator are introduced into the mercury recovery device. Since it is necessary to install a heat exchanger or the like for cooling before starting, it is required to keep equipment costs and operation costs of these devices low.

  Then, this invention is made | formed in view of the said prior art, Comprising: It aims at removing mercury from a cement kiln combustion exhaust gas efficiently, restraining equipment cost and operation cost low.

To achieve the above object, the present invention, a gas containing a heating device Ru evaporate the mercury in the dust by heating the dust contained in the exhaust gas of the cell Mentokirun, and mercury was the volatilized with the heated dust A cement kiln exhaust gas treatment device comprising: a solid-gas separation device for solid-gas separation; and a mercury recovery device for collecting mercury contained in the gas separated by the solid-gas separation device. The dust before being supplied to the heating device using the separated gas as a heat source is preheated, and the gas separated by the solid-gas separation device after being used as the heat source for the preheating is supplied to the mercury recovery device. A preheating device is provided .

According to the present invention, by preheating the dust contained in the exhaust gas of the cement kiln with the preheating device, the amount of heat required for heating can be reduced, the heating device and the like can be reduced in size, and the equipment cost and operation cost can be reduced. Can be kept low. In addition, since the temperature of the gas after being used as a heat source has decreased, the heat exchanger and the like provided in the front stage of the mercury recovery apparatus can be reduced in size, and the equipment cost and operation cost can be further reduced. It becomes.

  The preheating device can be an indirect heating device, and the indirect heating can prevent the mercury contained in the exhaust gas of the heating device from condensing. Moreover, the sensible heat of the exhaust gas discharged | emitted from the said solid-gas separation apparatus can be utilized for the preheating in a preheating apparatus.

Further, the present invention is that the dust contained in the exhaust gas of the cell Mentokirun by heating pressurization to volatilize the mercury in the dust, separated solid feeling a gas containing a mercury above volatilized with the heated dust, solid gas separation A method of treating a cement kiln exhaust gas for recovering mercury contained in the gas , wherein the dust before heating is preheated using the solid-gas separated gas as a heat source and used as a heat source for the preheating. Mercury contained in the gas separated after the solid-gas separation is recovered .

  According to the present invention, by preheating the dust contained in the exhaust gas of the cement kiln, the amount of heat required for heating can be reduced, the heating device and the like can be reduced in size, and the equipment cost and operation cost can be kept low. It becomes possible.

  As described above, according to the present invention, mercury can be efficiently removed from cement kiln combustion exhaust gas while keeping facility costs and operation costs low.

BRIEF DESCRIPTION OF THE DRAWINGS It is a whole block diagram which shows one Embodiment of the processing apparatus of the cement kiln exhaust gas which concerns on this invention.

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

  FIG. 1 shows an embodiment of a cement kiln exhaust gas treatment device according to the present invention. The exhaust gas treatment device 1 is a cement kiln dust (hereinafter referred to as “kiln dust”) recovered by a dust collector or the like of the cement kiln exhaust gas. .) Heated by an external heat kiln 5 as a preheating device for preheating D1, a hot air furnace 2 as a heating device for heating dust D2 preheated by the external heat kiln 5, and a hot gas G1 from the hot air furnace 2 A cyclone 3 for primary collection of dust (dust contained in the exhaust gas G2), a bag filter 4 for secondary collection of heated dust, exhaust gas G5 and air A discharged from the external heat kiln 5 The heat exchanger 6 that performs the heat exchange of the above, the mercury recovery device 8 that recovers the mercury contained in the exhaust gas G6 cooled by the heat exchanger 6, and the like.

  The external heat kiln 5 is provided for preheating the kiln dust D1, and preheats the kiln dust D1 passing through the inside of the inner cylinder by the exhaust gas G4 from the bag filter 4 at 350 ° C. to 450 ° C. passing through the outer cylinder.

  The hot stove 2 is provided for volatilizing mercury in the preheated dust D2, and the dust D2 is heated by the hot gas G1 of about 600 ° C. from the hot stove 2. Air may be introduced into the hot stove 2 to burn the fuel to generate hot gas, or clinker cooler exhaust in the cement firing process may be introduced.

  The cyclone 3 is provided to primarily collect dust heated in the hot stove 2 from the exhaust gas G2 and separate it into the exhaust gas G3 and mercury-excluded dust D3. Mercury-excluded dust D3 is used as a cement raw material. An apparatus other than the cyclone can be used as the solid-gas separation apparatus.

  The bag filter 4 is provided to separate the exhaust gas G3 after primary dust collection into exhaust gas G4 and mercury-excluded dust D4. The mercury-excluded dust D4 is used as a cement raw material, and the exhaust gas G4 is used for preheating the kiln dust D1 in the external heat kiln 5. The temperature of the exhaust gas G4 is about 350 ° C. to 450 ° C.

  The bag filter 4 is preferably a high heat resistant type having a heat resistance of about 900 ° C. Various types of bag filters have been developed, such as those in which a plurality of rod-shaped ceramic tubes formed into honeycomb cells are arranged, and those using sheet-like ceramic filters. The type of the filter is not particularly limited as long as it can collect fine particles contained in the exhaust gas G1. The cyclone 3 and the bag filter 4 constitute a high-temperature solid-gas separation device.

  The heat exchanger 6 is provided to exchange heat between the exhaust gas G5 and the air A from the fan 9. Since mercury is present in the exhaust gas G5, it is necessary to use a non-contact type heat exchanger with the exhaust gas G5 in order to avoid recondensation of mercury. The high-temperature air H generated by heat exchange in the heat exchanger 6 can be used in the hot stove 2, and can also be used as a heat source for a steam boiler or a heat source for air preheating.

  The mercury recovery device 8 is provided for recovering mercury from the exhaust gas G6 introduced from the heat exchanger 6 via the fan 7. As the mercury recovery device 8, a gas adsorption device that adsorbs and removes mercury with an adsorbent can be used. Specifically, a cartridge-type stationary phase adsorption device, a continuous cross-flow type bed-transfer adsorption device, or the like can be used. At this time, as the adsorbent, it is preferable to use sulfur or a metal sulfide, an adsorption medium carrying activated carbon or activated carbon, an adsorption medium carrying a metal that reacts with mercury or mercury, or the like. As the activated carbon used in the mercury recovery apparatus, it is desirable to select an activated carbon that is more excellent in mercury removal ability than commercially available activated carbon. In particular, activated carbon that has been subjected to sulfur impregnation treatment adjusted for mercury adsorption is preferred.

  By using a device using activated carbon, activated coke, or the like for the mercury recovery device 8, in addition to mercury, it decomposes and removes harmful substances typified by organochlorine compounds such as trace amounts of dioxins and PCBs contained in the exhaust gas G6. You can also.

  Next, operation | movement of the waste gas processing apparatus 1 which has the said structure is demonstrated, referring FIG.

  The kiln dust D1 recovered by a dust collector or the like of the cement kiln exhaust gas is put into the external heat kiln 5 and preheated using the exhaust gas G4 at 350 ° C. to 450 ° C. from the bag filter 4. As a result, the kiln dust D1 is heated to 100 ° C. to 350 ° C.

  Next, the dust D2 from the external heat kiln 5 is further heated with a high-temperature gas G1 of about 600 ° C. from the hot stove 2 to volatilize most of the mercury in the dust contained in the exhaust gas G2. The exhaust gas G2 is separated into mercury-excluded dust D3 and exhaust gas G3 by the cyclone 3. The exhaust gas G3 is separated by the bag filter 4 into mercury-excluded dust D4 and exhaust gas G4. The mercury-excluded dusts D3 and D4 are used as cement raw materials, and the exhaust gas G4 is used for preheating the kiln dust D1.

  The exhaust gas G5 discharged from the external heat kiln 5 is heat-exchanged with the air A from the fan 9 by the heat exchanger 6. The exhaust gas G6 after the heat exchange becomes 70 ° C. to 80 ° C., and the high temperature air H is generated using the sensible heat of the exhaust gas G5 recovered by the heat exchanger 6, and the high temperature air H is used in the hot air furnace 2.

  The exhaust gas G6 heat-exchanged by the heat exchanger 6 is introduced into the mercury recovery device 8 and mercury is recovered. Mercury recovery is disposed of, and the exhaust gas after mercury is recovered is released into the atmosphere or returned to the kiln system.

  As described above, in the present embodiment, the kiln dust D1 is preheated by the external heat kiln 5, thereby reducing the amount of heat required for heating the dust D2 in the hot stove 2 and reducing the size of the hot stove 2 and the like. By using the exhaust gas G4 discharged from the bag filter 4 as a heat source for the external heat kiln 5, the temperature of the exhaust gas G5 can be lowered, the heat exchanger 6 and the like can be downsized, and the cement kiln exhaust gas treatment device 1 equipment cost and operation cost can be reduced.

  In the above embodiment, the external heat kiln 5 is used to preheat the kiln dust D1, but other types of preheating devices may be used, and the heat source of the preheating device is limited to the exhaust gas G4 of the bag filter 4. Alternatively, other heat sources can be used.

DESCRIPTION OF SYMBOLS 1 Cement kiln exhaust gas processing apparatus 2 Hot-blast furnace 3 Cyclone 4 Bag filter 5 External heat kiln 6 Heat exchanger 7 Fan 8 Mercury recovery apparatus 9 Fan A Air D1 Kiln dust D2 Dust D3, D4 Mercury exclusion dust G1 Hot gas G2-G6 Exhaust gas H Hot air

Claims (4)

A heating device Ru evaporate the mercury in the dust by heating the dust contained in the exhaust gas of the cement kiln,
A solid-gas separation device for solid-gas separation of the gas containing the heated dust and the volatilized mercury ;
A cement kiln exhaust gas treatment device comprising a mercury recovery device for recovering mercury contained in the gas separated by the solid-gas separation device ,
The dust separated by the solid-gas separation device is used as a heat source to preheat dust before being supplied to the heating device, and the gas separated by the solid-gas separation device after being used as the heat source for the preheating is used as the heat source. A cement kiln exhaust gas treatment device comprising a preheating device for supplying to a mercury recovery device. The cement kiln exhaust gas treatment apparatus according to claim 1, wherein the preheating device is an indirect heating device. The cement kiln exhaust gas treatment apparatus according to claim 2 , wherein sensible heat of the exhaust gas discharged from the solid-gas separation device is used for preheating in the preheating device. The dust contained in the exhaust gas of the cement kiln by heating pressurization to volatilize the mercury in the dust,
Solid-gas separation of the gas containing the heated dust and the volatilized mercury ;
A method for treating a cement kiln exhaust gas for recovering mercury contained in the gas separated into solid and gas ,
Preheating the dust before being heated using the solid-gas separated gas as a heat source, and collecting mercury contained in the solid-gas separated gas after being used as the heat source for the preheating. Cement kiln exhaust gas treatment method.

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