JP2016108606A - Mercury recovery system and mercury recovery method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently recover mercury from a material containing mercury, at low cost.SOLUTION: A mercury recovery system 1 comprises: an external heat kiln 4 for putting in a mercury-containing dust D3 from a dust supply part 4d, indirectly heating it for volatilizing the mercury contained in the mercury-containing dust D3, discharging transport gas G1 including volatilized mercury from a gas discharge part 4f, and discharging a mercury-removed dust D4 from a dust discharge part 4g, comprising a low temperature side jacket 4b and a high temperature side jacket 4c along an axial direction of the external heat kiln 4, and heating temperature by the low temperature side jacket 4b positioned on the dust supply part 4d side is set to become lower than heating temperature by the high temperature side jacket 4c disposed on the dust discharge part 4g; and an active carbon absorption tower 7 for collecting the mercury contained in the transport gas G1 discharged from the external kiln 4. As a heat source of the low temperature side jacket 4b disposed on the dust supply part 4d side, discharge gas of the high temperature side jacket 4b can be used.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a system and method for recovering mercury from a substance containing mercury such as dust and coal ash recovered from a cement kiln exhaust gas.

  Cement kiln exhaust gas contains mercury contained in natural raw materials such as limestone, which is the main raw material of cement, and trace amounts of mercury derived from mercury contained in recycled resources such as fly ash. If the mercury in the cement kiln exhaust gas increases, it may cause air pollution, which may hinder the expansion of the use of recycled resources such as fly ash.

  Therefore, in Patent Document 1, as shown in FIG. 2, a hot air furnace 12 for heating air A11 and a kiln dust D11 containing mercury recovered from cement kiln exhaust gas and directly heated with gas G11 from the hot air furnace 12 are extracted. Duct 13, cyclone 14 that collects carrier gas G 12 containing volatile mercury and separates it into mercury-containing gas G 13 and mercury removal dust D 12, and mercury-containing gas G 13 that collects mercury-containing gas G 14 and removes mercury Bag filter 15 separated into dust D13, heat exchanger 16 for recovering heat from mercury-containing gas G14, activated carbon adsorption tower 19 for recovering mercury contained in mercury-containing gas G15, and heat generated in heat exchanger 16 A cement kiln exhaust gas treatment device 11 including a fan 18 for supplying the hot air furnace 12 to the hot air furnace 12 has been proposed.

JP 2011-88770 A

  However, in the processing method described in Patent Document 1, it is not easy to uniformly heat the kiln dust D11, and in order to volatilize the mercury in the kiln dust D11 without leakage, a large amount of gas G11 used for heating must be used. I didn't get it. For this reason, the amount of the transfer gas G12 increases, and the related equipment such as the extraction duct 13 as a heating device, the cyclone 14 and the bag filter 15 as a dust collecting device, and the activated carbon adsorption tower 19 as a mercury recovery device are enlarged. Inevitably, there was a problem that the equipment cost and the operating cost were increased.

  Therefore, the present invention has been made in view of the above problems in the prior art, and an object of the present invention is to efficiently recover mercury from a substance containing mercury at a low cost.

  In order to achieve the above object, the present invention is a mercury recovery system, in which a substance containing mercury is introduced from one open end, and the indirect heating is performed to volatilize the mercury contained in the one open end. An external heat kiln for discharging a gas containing volatile mercury from the other open end and discharging a mercury removing substance from the other opening end, and having a plurality of heat sources for indirect heating along the axial direction of the external heat kiln, An external heat kiln in which the heating temperature by the heat source located on the opening end side of the other is set lower than the heating temperature by the heat source located on the other opening end side, and mercury contained in the gas discharged from the external heat kiln is recovered And a mercury recovery device.

  According to the present invention, since an external heating kiln that is an indirect heating device can be used to uniformly heat a substance containing mercury without using a large amount of gas, downsizing of related equipment such as a mercury recovery device can be achieved. Is possible. Further, contact between the substance containing mercury and the heating medium can prevent mercury from being contained in the heating medium, and the heating medium processing apparatus can be simplified.

  Furthermore, the low-temperature heat source located on one opening end side where the mercury-containing substance is placed, removes moisture and adhesive components contained in the mercury-containing substance, thereby improving the fluidity of the mercury-containing substance. The high-temperature heat source located on the open end side of the metal can effectively volatilize mercury while preventing the mercury-containing material from becoming granular, thus improving mercury removal efficiency and reducing heat loss Can do.

  In the mercury recovery system, the heat gas used as the heat source located on the other opening end side can be used as the heat source located on the one opening end side, thereby reducing the operating cost of the external heat kiln. Can do.

  Also, two heat sources for indirect heating are provided, the heating temperature by the heat source located on the one opening end side is 100 ° C. or more and 300 ° C. or less, and the heating temperature by the heat source located on the other opening end side is 380 ° C. or more. It can be set to 500 ° C. or lower. The other open end side is heated by heating the substance containing mercury at a temperature above the boiling point of water so that the mercury-containing substance does not become granular by a heat source located on one open end side where the mercury-containing substance is introduced. Mercury can be effectively volatilized by heating a mercury-containing substance at a temperature not lower than the boiling point of mercury by a heat source located in the area. In addition, by setting the upper limit value of the heating temperature to 500 ° C. in the heat source on the other opening end side, it is possible to maintain a stable operation of the external heat kiln and prevent overheating.

  And a dust collecting device that collects the gas discharged from the external heat kiln and a dilution gas adding device that adds a dilution gas to the exhaust gas of the dust collecting device, and is included in the diluted exhaust gas. Mercury can be recovered by adsorption with the mercury recovery device. When volatile mercury is transported from an external heat kiln with a small amount of transport gas, the concentration of mercury in the transport gas is reduced to a concentration suitable for adsorption. The mercury recovery efficiency in the mercury recovery device can be improved.

  Further, the present invention is a mercury recovery method, in which a substance containing mercury is introduced from one opening end, and the mercury contained in the substance is volatilized by indirect heating, and volatile mercury is contained from the one opening end. In the external heat kiln that discharges gas and discharges the mercury removing material from the other opening end, the heating temperature of the one opening end side region is set lower than the heating temperature of the other opening end side region, Mercury contained in the gas discharged from the external heat kiln is recovered.

  According to the present invention, similarly to the above-described invention, since an external heat kiln that is an indirect heating device can be used to uniformly heat a substance containing mercury without using a large amount of gas, the incidental equipment can be reduced in size. It is possible to simplify the processing of the heating medium by preventing mercury from being contained in the heating medium due to contact between the substance containing mercury and the heating medium, and the heating temperature of the external heat kiln can be reduced. By adjusting, it is possible to improve the mercury removal efficiency and reduce heat loss.

  As described above, according to the present invention, mercury can be efficiently recovered from a substance containing mercury at low cost.

1 is an overall configuration diagram showing an embodiment of a mercury recovery system according to the present invention. It is a whole block diagram which shows an example of the conventional mercury collection | recovery system.

  Next, an embodiment for carrying out the present invention will be described in detail with reference to the drawings. In the following, a case where dust collected from cement kiln exhaust gas is treated by the mercury recovery system according to the present invention will be described as an example.

  FIG. 1 shows an embodiment of a mercury recovery system according to the present invention. This mercury recovery system 1 is supplied from a hopper 2 for storing a kiln dust D1 containing mercury recovered from a cement kiln exhaust gas and a hopper 2. The screw conveyor 3 that conveys the mercury-containing dust D3 in which the kiln dust D1 and the mercury removal dust D2 to be described later are mixed, and the mercury-containing dust D3 supplied from the screw conveyor 3 is indirectly heated and contains the volatilized mercury by the indirect heating. An external heat kiln 4 that separates the gas and the mercury removal dust D4 from each other; a bag filter 5 that separates the carrier gas G1 discharged from the external heat kiln 4 into the mercury-containing gas G2 and the mercury removal dust D2; A fan 6 for adding a dilution air A2 to the mercury-containing gas G2 discharged from 5 to form a mercury dilution gas G3; And a activated carbon adsorption tower 7 to recover adsorbed mercury contained in the silver diluent gas G3.

  The external heat kiln 4 as an indirect heating device surrounds the kiln 4a so as to be adjacent to the rotary kiln 4a, the high temperature side jacket 4c which surrounds the kiln 4a and introduces high temperature gas, and the high temperature side jacket 4c. A low temperature side jacket 4b into which a gas having a temperature lower than that of the high temperature side jacket 4c is introduced, a dust supply part 4d for supplying mercury-containing dust D3, a gas introduction part 4e for introducing air A1, and a carrier gas G1. It has a gas discharge part 4f for discharging and a dust discharge part 4g for discharging the mercury removal dust D4. The low temperature side jacket 4b is located on the dust supply part 4d side, and the high temperature side jacket 4c is located on the dust discharge part 4g side. Moreover, the gas discharged | emitted from the high temperature side jacket 4c can be utilized for the low temperature side jacket 4b.

  As the bag filter 5 as a dust collector, a high heat-resistant bag filter having heat resistance up to about 900 ° C. or a normal heat filter can be used.

  The activated carbon adsorption tower 7 as a mercury recovery device is provided for adsorbing and recovering mercury in the mercury dilution gas G3. As the activated carbon used in the activated carbon adsorption tower 7, it is desirable to select an activated carbon that is particularly excellent in mercury recovery ability from among commercially available activated carbons. Specifically, a sulfur impregnation treatment adjusted for mercury adsorption is performed. Activated carbon is preferred.

  Next, the operation of the mercury recovery system 1 having the above configuration will be described with reference to FIG.

  High temperature gas is introduced into the high temperature side jacket 4 c of the external heat kiln 4, exhaust gas of the high temperature side jacket 4 c is introduced into the low temperature side jacket 4 b, the inside of the kiln 4 a is heated, and the kiln dust D 1 is kiln via the screw conveyor 3. Indirect heating by supplying to 4a. The kiln dust D1 is heated in contact with the inner surface of the kiln 4a heated by the low temperature side jacket 4b, and moisture, adhesive components and the like are volatilized. Next, the kiln dust D1 is heated in contact with the inner surface of the kiln 4a heated by the high temperature side jacket 4c, and mercury is volatilized. On the other hand, mercury-removed dust D4 from which mercury has been removed is discharged out of the system from the dust discharge section 4g and used as a cement raw material or the like.

  Mercury volatilized by the air A1 introduced from the gas inlet 4e is transported, and a transport gas G1 containing volatile mercury is discharged from the gas discharger 4f. The carrier gas G1 is introduced into the bag filter 5 and separated into the mercury-containing gas G2 and the mercury removing dust D2.

Dilution air A2 is added to the mercury-containing gas G2 from the fan 6 so that the mercury concentration of the mercury-containing gas G2 becomes a concentration suitable for adsorption in the activated carbon adsorption tower 7 (1,000 mg / m ³ or less). After that, mercury in the mercury dilution gas G3 is adsorbed by the activated carbon adsorption tower 7 and recovered. Here, by setting the temperature of the dilution air A2 to 20 ° C. to 80 ° C., the mercury-containing gas G2 can be cooled as well as being diluted, and the adsorption efficiency in the activated carbon adsorption tower 7 can be increased. The mercury removal gas G4 discharged from the activated carbon adsorption tower 7 is discharged into the atmosphere after appropriate exhaust gas treatment. On the other hand, the mercury removal dust D2 is returned to the screw conveyor 3 and supplied to the kiln 4a as the mercury-containing dust D3 together with the kiln dust D1.

  As described above, in the above embodiment, the mercury-containing dust D3 can be uniformly heated without using a large amount of gas by using the external heat kiln 4 as an indirect heating device. The amount of the transfer gas G1 discharged from the gas discharge unit 4f can be reduced, and the related equipment such as the bag filter 5 and the activated carbon adsorption tower 7 can be downsized. Further, it is possible to prevent mercury from being contained in the heating medium due to contact between the mercury-containing dust D3 and the heating medium (in this embodiment, the high temperature gas introduced into both jackets 4b and 4c). The apparatus can be simplified.

  Furthermore, by heating by the low temperature side jacket 4b located on the dust supply part 4d side where the mercury-containing dust D3 is charged, the moisture, adhesive components, etc. contained in the mercury-containing dust D3 are volatilized, thereby being located on the dust discharge part 4g side The high-temperature heating by the high-temperature side jacket 4c that prevents the mercury-containing dust D3 from granulating can effectively volatilize the mercury contained in the mercury-containing dust D3, increase the mercury removal efficiency, and reduce the heat loss Can be achieved.

  In addition, although the said embodiment demonstrated the case where the dust collect | recovered from cement kiln exhaust gas was processed, if it is a substance containing mercury, such as coal ash, another substance can also be processed.

  Moreover, it can replace with the air A1 introduce | transduced into the gas introduction part 4e of the external heat kiln 4, can also use an inert gas, and can also use an inert gas other than the dilution air A2 as a dilution gas. Furthermore, the heated air A1 can be introduced into the gas introduction part 4e of the external heat kiln 4, and the air A1 can be retained in the kiln 4a and heated. In heating the inside of the kiln 4a of the external heat kiln 4, a heating medium other than the high temperature gas may be used for the low temperature side jacket 4b and the high temperature side jacket 4c, and three or more jackets may be used as a heat source. .

  Furthermore, instead of the bag filter 5 and the activated carbon adsorption tower 7 in the mercury recovery system 1, other types of dust collectors and mercury recovery devices can be used. The external heat kiln 4 has a gas discharge part 4f for discharging the transfer gas G1 and a dust discharge part 4g for discharging the mercury removal dust D4, and discharges the transfer gas G1 and the mercury removal dust D4 separately. However, since part of the mercury removal dust is mixed in the transfer gas G1, the bag filter 5 is provided. Even if the concentration of the mercury removal dust in the transport gas increases, the dust collection device collects the transport gas using an external heat kiln that has a common discharge section for the transport gas and mercury removal dust. Can respond.

DESCRIPTION OF SYMBOLS 1 Mercury recovery system 2 Hopper 3 Screw conveyor 4 External heat kiln 4a Kiln 4b Low temperature side jacket 4c High temperature side jacket 4d Dust supply part 4e Gas introduction part 4f Gas discharge part 4g Dust discharge part 5 Bag filter 6 Fan 7 Activated carbon adsorption tower A1 Air A2 Air for dilution D1 Kiln dust D2 Mercury removal dust D3 Mercury-containing dust D4 Mercury removal dust G1 Transport gas G2 Mercury-containing gas G3 Mercury dilution gas G4 Mercury removal gas

Claims (5)

A substance containing mercury is introduced from one open end, the mercury contained in the substance is volatilized by indirect heating, a gas containing volatile mercury is discharged from the one open end, and a mercury removing substance is discharged from the other open end. An external heat kiln that has a plurality of heat sources for indirect heating along the axial direction of the external heat kiln, and the heating temperature by the heat source located on the one opening end side is set to the other opening end side An external heat kiln set lower than the heating temperature by the heat source located at
A mercury recovery system comprising: a mercury recovery device that recovers mercury contained in gas discharged from the external heat kiln.   The mercury recovery system according to claim 1, wherein a hot gas used as a heat source located on the other opening end side is used for the heat source located on the one opening end side.   Two heat sources for indirect heating are provided, the heating temperature by the heat source located on the one opening end side is 100 ° C. or more and 300 ° C. or less, and the heating temperature by the heat source located on the other opening end side is 380 ° C. or more and 500 ° C. The mercury recovery system according to claim 1 or 2, wherein the mercury recovery system is set as follows.   A dust collecting device for collecting the gas discharged from the external heat kiln; and a dilution gas adding device for adding a dilution gas to the exhaust gas of the dust collecting device, wherein the mercury contained in the diluted exhaust gas is removed. The mercury recovery system according to claim 1, 2 or 3, wherein the mercury recovery device is used for adsorption and recovery. A substance containing mercury is introduced from one open end, the mercury contained in the substance is volatilized by indirect heating, a gas containing volatile mercury is discharged from the one open end, and a mercury removing substance is discharged from the other open end. In the external heat kiln that discharges, the heating temperature of the region on the one opening end side is set lower than the heating temperature of the region on the other opening end side,
A method for recovering mercury comprising recovering mercury contained in a gas discharged from the external heat kiln.