JP6370237B2 - Mercury recovery system and mercury recovery method - Google Patents

Description

  The present invention relates to an apparatus and method for recovering mercury from a substance containing mercury such as dust and coal ash recovered from 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 the heating device, the cyclone 14 and the bag filter 15 as the dust collector, and the activated carbon adsorption tower 19 as the mercury adsorption 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, which indirectly heats a substance containing mercury to volatilize mercury contained in the substance, and discharges a carrier gas containing the volatile mercury. An auxiliary carrier gas adding device for adding an auxiliary carrier gas to the carrier gas discharged from the indirect heating device, a dust collector for collecting dust from the carrier gas and the auxiliary carrier gas, And a mercury recovery device for recovering mercury contained in the exhaust gas of the dust collector.

  According to the present invention, since a substance containing mercury can be uniformly heated without using a large amount of gas by using an indirect heating device, the amount of transport gas discharged from the indirect heating device can be reduced. It is possible to reduce the size of related equipment such as an indirect heating device, a dust collector, and a mercury recovery device. 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, by adding auxiliary transport gas to the transport gas discharged from the indirect heating device, dust contained in the transport gas accumulates inside the piping from the indirect heating device to the dust collector. Can be prevented and stable operation can be achieved.

  In the mercury recovery system, the indirect heating device includes a gas discharge unit that discharges the carrier gas containing the volatile mercury, and a substance discharge unit that discharges a mercury removal material generated by removing mercury from the mercury-containing substance. Can be provided. Thereby, since only the volatile mercury has to be transported without transporting the mercury removing substance by the transport gas, the transport gas can be further reduced. Further, the indirect heating device can be an external heat kiln.

  Furthermore, the present invention is a mercury recovery method, wherein the substance containing mercury is indirectly heated to volatilize the mercury contained in the substance, and the auxiliary carrier gas is added to the carrier gas containing the volatile mercury, Dust is collected from the carrier gas and the auxiliary carrier gas, and mercury contained in the exhaust gas after the dust collection is collected.

  According to the present invention, as in the case of the above-mentioned invention, since the substance containing mercury can be heated uniformly by performing indirect heating without using a large amount of gas, the amount of gas for transportation can be reduced. The cost required for indirect heating, dust collection, and mercury adsorption can be reduced. Further, contact of the substance containing mercury with the heating medium can prevent the heating medium from containing mercury, and the heating medium can be easily processed.

  Furthermore, by adding an auxiliary carrier gas to the carrier gas, dust contained in the carrier gas is prevented from accumulating inside the piping from the indirect heating device to the dust collector, and stable operation is ensured. Can be planned.

  In the mercury recovery method, the gas containing volatile mercury generated by the indirect heating and the mercury removing substance are separated from each other, and the gas containing volatile mercury can be used as the carrier gas. Thereby, since only the volatile mercury has to be transported without transporting the mercury removing substance by the transport gas, the transport gas can be further reduced.

  Further, by adding the auxiliary carrier gas to the carrier gas, the flow rates of the carrier gas and the auxiliary carrier gas can be adjusted to 0.5 m / second or more and 20 m / second or less. Further, the mercury-containing substance can be dust or coal ash recovered from cement kiln exhaust gas. Further, the temperature of the auxiliary transport gas can be set to 20 ° C. or more and 500 ° C. or less, and the temperature of the volatile mercury is lowered by increasing the temperature of the transport gas, thereby preventing the volatile mercury from adhering to dust. be able to.

  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 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 fan 5 that adds auxiliary transport air A2 to the transport gas G1 discharged from the external heat kiln 4, a transport gas G1, and an auxiliary transport Bag filter 6 that separates air A2 into mercury-containing gas G2 and mercury-removed dust D2, and contained in mercury-containing gas G2. And a activated carbon adsorption tower 7 to recover adsorbed silver.

  The external heat kiln 4 as an indirect heating device includes a rotary kiln 4a, a jacket 4b that surrounds the kiln 4a and into which high-temperature gas is introduced, a dust supply unit 4c that supplies mercury-containing dust D3, and air A1. It has a gas introduction part 4d to be introduced, a gas discharge part 4e for discharging the carrier gas G1, and a dust discharge part 4f for discharging the mercury removal dust D4.

  For the bag filter 6 as a dust collector, a high heat-resistant bag filter having heat resistance up to about 900 ° C. or a normal heat-resistant bag filter can be used. As described above, the external heat kiln 4 separately discharges the transfer gas G1 and the mercury removal dust D4. However, since a part of the mercury removal dust D4 is mixed in the transfer gas G1, the bag filter 6 is provided. Yes.

  The activated carbon adsorption tower 7 as a mercury adsorption device is provided for adsorbing and recovering mercury in the mercury-containing gas G2. 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.

  Hot gas is introduced into the jacket 4b of the external heat kiln 4 to heat the inside of the kiln 4a, and the kiln dust D1 is supplied to the kiln 4a via the screw conveyor 3 and indirectly heated. The kiln dust D1 is heated in contact with the inner surface of the kiln 4a having a high temperature, and mercury is volatilized. On the other hand, the mercury-removed dust D4 from which mercury has been removed is discharged out of the system from the dust discharge part 4f and used as a cement raw material or the like.

  Mercury volatilized by the air A1 introduced from the gas introduction part 4d is transported, and a transport gas G1 containing volatile mercury is discharged from the gas discharge part 4e. The auxiliary transfer air A2 is added from the fan 5 to the transfer gas G1, and the flow rates of the transfer gas G1 and the auxiliary transfer air A2 are adjusted to 0.5 m / second or more and 20 m / second or less. Thereby, it can prevent that the dust contained in the gas G1 for conveyance accumulates in the inside of piping from the external heat kiln 4 to the bag filter 6, etc. FIG.

  The temperature of the auxiliary transfer air A2 can be set to 20 ° C. to 500 ° C. However, by setting the auxiliary transfer air A2 to a high temperature, the temperature of the volatile mercury contained in the transfer gas G1 decreases, and the volatile mercury is reduced. It is preferable because it can be prevented from adhering to dust.

  Next, the carrier gas G1 and the auxiliary carrier air A2 are introduced into the bag filter 6 and separated into the mercury-containing gas G2 and the mercury removal dust D2. Then, the mercury in the mercury-containing gas G2 is adsorbed and recovered by the activated carbon adsorption tower 7. The mercury removal gas G3 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-described embodiment, since the mercury-containing dust D3 can be uniformly heated by the jacket 4b without using a large amount of gas by using the external heat kiln 4, the gas of the external heat kiln 4 is used. The amount of the transfer gas G1 discharged from the discharge unit 4e can be reduced, and the related equipment such as the external heat kiln 4, the bag filter 6, 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 the contact between the mercury-containing dust D3 and the heating medium (in this embodiment, the high temperature gas introduced into the jacket 4b), and the heating medium processing apparatus can be simplified. Can be.

  Further, by adding the auxiliary transport air A2 to the transport gas G1, dust contained in the transport gas G1 is prevented from accumulating inside the piping from the external heat kiln 4 to the bag filter 6 and the like. , Stable operation 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 4d of the external heat kiln 4, can also use an inert gas, and can also use an inert gas other than the auxiliary conveyance air A2 as an auxiliary conveyance gas. Moreover, the heated air A1 can also be introduce | transduced into the gas introduction part 4d of the external heat kiln 4, and the air A1 can also be retained in the kiln 4a and can be 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.

  Furthermore, instead of the external heat kiln 4, the bag filter 6 and the activated carbon adsorption tower 7 in the mercury recovery system 1, other types of indirect heating devices, dust collectors, and mercury recovery devices can be used. Even if the concentration of mercury removal dust in the carrier gas is increased using an indirect heating device that has a common discharge section for the carrier gas and mercury removal dust, the dust collector collects the mercury removal dust. It can cope with dust.

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

Claims (8)

An indirect heating device that indirectly heats a substance containing mercury to volatilize mercury contained in the substance, and discharges a carrier gas containing the volatile mercury;
An auxiliary carrier gas addition device for adding an auxiliary carrier gas to the carrier gas discharged from the indirect heating device;
A dust collector for collecting dust from the carrier gas and the auxiliary carrier gas;
A mercury recovery system comprising: a mercury recovery device that recovers mercury contained in the exhaust gas of the dust collector.   The indirect heating device includes a gas discharge unit that discharges the carrier gas containing the volatile mercury, and a substance discharge unit that discharges a mercury removing substance generated by removing mercury from the mercury-containing substance. The mercury recovery system according to claim 1.   The mercury recovery system according to claim 1, wherein the indirect heating device is an external heat kiln. Indirectly heating a substance containing mercury to volatilize mercury contained in the substance,
An auxiliary carrier gas is added to the carrier gas containing volatile mercury,
Collecting dust from the carrier gas and the auxiliary carrier gas;
A method for recovering mercury comprising recovering mercury contained in exhaust gas after dust collection.   The mercury recovery method according to claim 4, wherein the gas containing volatile mercury and the mercury removing material generated by the indirect heating are separated from each other, and the gas containing volatile mercury is used as the carrier gas.   6. The auxiliary gas is added to the carrier gas to adjust the flow velocity of the carrier gas and the auxiliary carrier gas to 0.5 m / second or more and 20 m / second or less. The mercury recovery method as described.   The mercury recovery method according to claim 4, 5 or 6, wherein the substance containing mercury is dust or coal ash recovered from a cement kiln exhaust gas.   The mercury recovery method according to claim 4, wherein the temperature of the auxiliary carrier gas is 20 ° C. or more and 500 ° C. or less.

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