JP2010116283A - Apparatus and method for processing exhaust gas of cement kiln - Google Patents

Abstract

Mercury is efficiently removed from combustion exhaust gas discharged from a cement kiln.
SOLUTION: A dust collector 2 that collects dust contained in a cement kiln exhaust gas, a heating device 3 that heats the dust collected by the dust collector 2, and an exhaust gas that includes dust discharged from the heater 3 Treatment of cement kiln exhaust gas comprising a solid-gas separation device 6 having a ceramic filter for solid-gas separation and a mercury recovery device 8 for collecting mercury present on the gas phase side of the gas separated by the solid-gas separation device 6 Device 1. The heating device 3 can directly heat the dust with gas. The temperature of the exhaust gas containing the dust discharged from the heating device 3 can be set to 250 ° C. or higher and 800 ° C. or lower. A classification device 22 for classifying the dust collected by the dust collector 2 or a granulating device 32 for granulating the collected dust is provided, and the heating device 3 is provided on the fine dust side dust side classified by the classification device 22. The granulated product obtained by the dust or granulating device 32 may be heated.
[Selection] Figure 1

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.

  Cement kiln exhaust gas contains a trace amount of metallic mercury (Hg). Its origin is not only mercury contained in natural raw materials such as limestone, which is the main raw material of cement, but also mercury contained in a wide variety of recycled resources such as fly ash. In recent years, the recycling of wastes as cement raw materials and fuels has been promoted, and as the amount of waste processed 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 cement kiln at a low concentration from a large amount of exhaust gas, and if the mercury in the exhaust gas of cement kiln increases, it may cause air pollution, There is also a risk of hindering the expansion of the use of recycled resources such as fly ash.

  Therefore, for example, Patent Document 1 discloses that a cement kiln is used to efficiently remove mercury and the like contained in exhaust gas discharged from a cement manufacturing process, and to recycle dust collection dust from which mercury and the like are removed as a cement raw material. Cement production that removes exhaust gas with a dust collector, then guides the collected dust to a heating furnace, heats the mercury in the dust to a volatilization temperature and volatilizes it, and then adsorbs it with an adsorbent and removes it. An exhaust gas treatment method has been proposed.

  However, although the above document describes that the volatilized mercury is recovered using an absorbing solution or an adsorbent, the temperature of the gas containing the volatile mercury to be treated and the treatment for the recovery of the mercury Details of the recovery method are not mentioned, such as whether or not dust is removed in advance from the target gas.

  On the other hand, in Patent Document 2, in order to prevent the accumulation of harmful substances such as mercury and dioxin in the cement manufacturing facility, after being discharged from the preheater for preheating the cement raw material, the time until the chimney is reached. A method of extracting a part of exhaust gas having a temperature of 350 ° C. or higher circulating in the pipe or the apparatus and condensing and removing harmful substances such as mercury and dioxin contained in the gas is described.

Japanese Patent Laid-Open No. 2002-355531 JP 2005-97005 A

  However, in the method described in Patent Document 2, dust is collected from the exhaust gas by the preheater cyclone, but the uncollected dust is guided to the condensing device together with mercury in the exhaust gas, and thus recovered from the condensing device. The dust that is produced is in a state where mercury and a substance other than mercury are mixed. For this reason, an operation for taking out only mercury from the collected dust is required separately, which causes a problem that the processing cost increases and the processing efficiency decreases.

  Then, this invention is made | formed in view of the problem in the said prior art, Comprising: It aims at efficiently removing mercury from the combustion exhaust gas discharged | emitted from a cement kiln.

  In order to achieve the above object, the present invention is a cement kiln exhaust gas treatment apparatus, which collects dust contained in cement kiln exhaust gas, and heats the dust collected by the dust collector. Present on the gas phase side of the gas separated by the solid-gas separation device, the solid-gas separation device comprising a ceramic filter for solid-gas separation of the exhaust gas containing the dust discharged from the heating device And a mercury recovery device for recovering mercury.

  According to the present invention, mercury contained in the dust in the exhaust gas of the cement kiln is volatilized by heating the dust, and after removing the high-temperature dust after heating, the mercury present on the gas phase side is removed. It can be recovered. Therefore, mercury can be efficiently removed from the exhaust gas of the cement kiln while preventing dust from entering the mercury recovery apparatus.

  In the cement kiln exhaust gas treatment device, the heating device can directly heat the dust collected by the dust collector with gas. Since the dust is directly heated by the gas, the dust can be heated uniformly and efficiently, and mercury in the dust can be efficiently removed.

  In the cement kiln exhaust gas treatment device, the temperature of the exhaust gas containing the dust discharged from the heating device can be 250 ° C. or more and 800 ° C. or less. In this temperature range, most of the mercury in the exhaust gas is contained. Since it is volatilized, mercury can be recovered efficiently.

  Further, in the cement kiln exhaust gas treatment apparatus, a classification device for classifying the dust collected by the dust collection device is provided, and the heating device heats the dust on the fine powder side classified by the classification device. it can. According to this, dust is classified in the cement kiln exhaust gas, so that dust with a high mercury content is selectively taken out, and the mercury removal process is performed on the dust, which is unnecessary for mercury removal. The removal process can be performed with the dust removed in advance. Therefore, a large amount of cement kiln exhaust gas can be processed in a short time, or the facility scale can be reduced, so that it is possible to improve the processing efficiency and reduce the processing cost.

  Further, in the cement kiln exhaust gas treatment apparatus, a granulation device for granulating the dust collected by the dust collector is provided, and the heating device heats the granulated material obtained by the granulation device. be able to. According to this, since the dust in the exhaust gas is heated after being granulated, even when a heating device with a small equipment capacity is used, a sufficient heating time for volatilization of mercury can be ensured. Mercury can be volatilized without leakage, and since the dust is granulated, the amount of dust to be processed in the subsequent stage is reduced, and the burden on the subsequent dust processing process can be reduced.

  The present invention also relates to a method for treating a cement kiln exhaust gas, the dust contained in the exhaust gas of the cement kiln is collected, the collected dust is heated, and the exhaust gas containing the heated dust is provided with a ceramic filter. Solid-gas separation is performed using a solid-gas separation device, and mercury present on the gas phase side of the gas separated by the solid-gas separation is recovered. According to the present invention, mercury can be efficiently removed from the exhaust gas of the cement kiln as in the above-described invention.

  As described above, according to the present invention, mercury can be efficiently removed from the combustion exhaust gas discharged from the cement kiln.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a first embodiment of a cement kiln exhaust gas treatment apparatus (hereinafter referred to as “treatment apparatus” as appropriate) according to the present invention. The treatment apparatus 1 collects dust contained in the cement kiln exhaust gas. An electric dust collector 2, a heating device 3 that heats dust collected by the electric dust collector 2 (hereinafter referred to as “EP dust”), a hot air generator 4 that supplies hot air H to the heating device 3, A cyclone 5 that collects the exhaust gas G1 containing dust heated by the heating device 3, a solid-gas separator 6 that collects the exhaust gas G2 of the cyclone 5, and a heat exchange that recovers heat from the exhaust gas G3 of the solid-gas separator 6 And a mercury recovery device 8 that recovers mercury from the exhaust gas G4 that has passed through the heat exchanger 7.

  The electric dust collector 2 is provided for collecting dust contained in the cement kiln exhaust gas discharged from the preheater attached to the cement kiln, and is usually used in cement firing equipment. Mercury in the exhaust gas is selectively and efficiently attached to this dust collection dust, and removal of mercury in the dust is the most effective for removing mercury in the cement manufacturing system. is there.

  The heating device 3 is provided to heat the EP dust using the hot air H from the hot air generator 4 and volatilize the mercury contained in the EP dust.

  The hot air generator 4 is provided to generate hot air as a heat source of the heating device 3 and generates hot air by burning predetermined fuel. From the viewpoint of reducing fuel costs and effectively using resources, the hot air generator 4 uses combustible waste such as waste oil and waste solvent as the main fuel, and uses only natural fuels such as heavy oil and kerosene as an auxiliary. It is desirable.

  The cyclone 5 is provided for collecting the exhaust gas G1 containing the EP dust heated by the heating device 3 and separating the coarse powder side dust D1 in the EP dust contained in the exhaust gas G1.

  The solid-gas separation device 6 is a bag filter equipped with a ceramic filter and has heat resistance up to 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. As long as the fine powder D2 contained in the exhaust gas G2 can be collected, the type of the filter is not particularly limited.

  The heat exchanger 7 is provided to effectively use the sensible heat of the exhaust gas G3 of the solid-gas separation device 6. Since volatilized mercury is present in the exhaust gas G3, it is necessary to use a heat exchanger of a type that does not contact the exhaust gas G3 as the heat exchanger 7 in order to avoid recondensation of mercury. The heat recovered by the heat exchanger 7 can be used as a heat source for a steam boiler or a heat source for air preheating.

  The mercury recovery device 8 is provided to remove mercury in the exhaust gas G4. As the mercury recovery device 8, either a dry type or a wet type recovery device can be used. In the case of using a dry adsorption device as the mercury recovery device 8, particularly activated carbon as the adsorption medium, it is necessary to lower the temperature of the exhaust gas G4 through the heat exchanger 7 to a temperature at which the activated carbon can be passed (for example, about 100 ° C.). On the other hand, when a wet gas absorption device is used as the mercury recovery device 8, the exhaust gas G3 does not necessarily have to pass through the heat exchanger 7, and can be directly introduced into the mercury recovery device 8.

  Next, the operation of the processing apparatus 1 having the above configuration will be described with reference to FIG.

  During operation of the cement kiln, the cement kiln exhaust gas is collected by the electric dust collector 2 and transferred to the heating device 3 to remove mercury contained in the collected EP dust.

  Next, the hot dust H from the hot air generator 4 is used to heat the EP dust conveyed from the electrostatic precipitator 2 in the heating device 3 to volatilize the mercury in the EP dust. Here, the temperature of the exhaust gas G1 from the heating device 3 is controlled to be 250 ° C. or higher and 800 ° C. or lower. Since most of the mercury in the exhaust gas volatilizes in this temperature range, the mercury can be recovered efficiently.

  Next, exhaust gas G1 containing heated EP dust and volatilized mercury is introduced into the cyclone 5, and the recovered coarse powder side dust D1 is returned to the cement kiln raw material system. Furthermore, the exhaust gas G2 of the cyclone 5 is introduced into the solid-gas separation device 6, and the collected fine powder side dust D2 is used as a raw material for the cement kiln or supplied to the heating device 3 to be reheated.

  Next, after introducing the exhaust gas G3 of the solid-gas separation device 6 into the heat exchanger 7 and effectively utilizing the sensible heat of the exhaust gas G3, the exhaust gas G4 of the heat exchanger 7 is introduced into the mercury recovery device 8, and the exhaust gas G4 Remove mercury. It is also possible to remove mercury by directly introducing it into the mercury recovery device 8 using a gas absorption device without introducing the exhaust gas G3 into the heat exchanger 7. The mercury G5 removed from the mercury recovery device 8 and detoxified is discharged into the atmosphere or returned to the kiln system.

  As described above, according to the present embodiment, high-temperature exhaust gas G2 containing volatile mercury is introduced into the solid-gas separation device 6 and fine powder side dust D2 is removed, and then the volatile mercury is recovered as it is. Since mercury is introduced into the apparatus 8 to recover the mercury, most of the volatilized mercury can be recovered by heating the EP dust, and mercury can be efficiently removed from the combustion exhaust gas discharged from the cement kiln. it can.

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

  The processing device 21 includes a classification device 22 between the electrostatic precipitator 2 and the heating device 3 in the processing device 1 shown in FIG. 1, and other components are the same as those of the processing device 1.

  The classifier 22 is provided for separating the dust collected by the electric dust collector 2 into the coarse powder side dust C and the fine powder side dust F, and includes a centrifugal force classifier, an inertial force classifier, and the like. Can be used. Preferably, for example, it is better to provide a centrifugal classifier having a built-in cage rotor having higher classification performance than a general cyclone air separator or the like. Further, the classification device 22 has a performance such that the particle size at which the partial classification efficiency is 50% is at least 10 μm or less.

  The coarse powder side dust C collected by the classifier 22 is reused as a cement raw material and the fine powder side dust F is introduced into the heating device 3 to remove mercury. This treatment is based on the knowledge that most of the mercury is unevenly distributed on the fine dust side of the EP dust, and only the portion containing a large amount of mercury is selectively extracted from the EP dust by the classification process. can do.

  According to this embodiment, in order to selectively take out the fine dust side dust F having a high mercury content from the EP dust collected by the electric dust collector 2, and to introduce only the fine dust side dust F into the heating device 3, When removing mercury, the heat treatment can be performed in a state in which those that do not require heat treatment are removed in advance. Accordingly, more dust can be introduced into the heating device 3 or the equipment scale can be reduced, so that it is possible to improve the processing efficiency and reduce the processing cost.

  Next, a third embodiment of the cement kiln exhaust gas treatment apparatus according to the present invention will be described with reference to FIG.

  This processing apparatus 31 includes a granulating device 32 between the electrostatic precipitator 2 and the heating device 3 in the processing apparatus 1 shown in FIG. 1, and other components are the same as those of the processing apparatus 1.

  The granulator 32 is provided for granulating the EP dust collected by the electric dust collector 2 to generate a granular material having a predetermined particle size (for example, 2 to 3 mm). The method of granulating EP dust is not particularly limited, and various granulators such as a compression molding granulator and an extrusion molding granulator can be used as the granulating device 32.

  In the present embodiment, it is preferable to use a fluidized bed type heating furnace as the heating device 3. In the fluidized bed type heating furnace, hot air having a predetermined temperature generated by the hot air generator 4 is blown from the bottom of the furnace to form a fluidized bed in the furnace, and the granulated product P that is charged is heated while flowing. For this reason, even if it is a small scale fluidized-bed-type heating furnace, the heating time of the granulated material P can fully be taken, and mercury can be volatilized efficiently.

  Moreover, it is preferable to use limestone for the auxiliary fluidizing material used in the fluidized bed heating furnace from the viewpoint of promoting fluidization of the granulated material P and desulfurization of exhaust gas.

  According to the present embodiment, since the EP dust collected by the electric dust collector 2 is granulated, each volume and weight is larger than the EP dust immediately after collection, and the heating device 3 for the granulated product P Spattering of the granulated material P in the furnace is suppressed at the time of charging into the container or at the time of heating by the heating device 3. For this reason, even when a small-scale furnace is used, the heating time of the granulated product P can be increased, mercury in the collected dust can be volatilized without leakage, and the dust is granulated. In addition, the amount of dust to be processed in the subsequent stage is reduced, and the burden on the subsequent dust processing process can be reduced. Moreover, since the apparent bulk density of the granulated product P after granulation is larger than that of the EP dust collected by the electric dust collector 2, the equipment capacity can be reduced.

  In the first to third embodiments, the EP dust collected by the electrostatic precipitator 2 is heated, but a bag filter, a cyclone, a mobile dust collector and the like are arranged instead of the electrostatic precipitator. The dust contained in the exhaust gas of the cement kiln may be collected by these dust collectors and conveyed to the heating device 3.

  Moreover, in the said embodiment, although the gas absorption apparatus etc. which use an absorption liquid were illustrated as the mercury collection | recovery apparatus 8, the gas adsorption apparatus which adsorbs and removes mercury with adsorption agent can be used, and, specifically, a cartridge type | formula A 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. In this case, an adsorbent is blown into the exhaust gas G4 of the heat exchanger to adsorb and remove the gasified mercury and remove the mercury from the exhaust gas G4. The adsorbent that has adsorbed mercury is collected and subjected to an appropriate final treatment. As a preferable final processing method, for example, consignment processing to a company or an organization that specializes in mercury recycling processing can be mentioned.

  Furthermore, by using a device that uses activated carbon or activated coke as the mercury recovery device, in addition to mercury, it decomposes and removes trace amounts of harmful substances typified by organic chlorine compounds such as dioxins and PCBs contained in the exhaust gas G1. You can also

  In the above embodiment, the temperature of the exhaust gas G2 is controlled in the range of 250 ° C. to 800 ° C., but the temperature of the exhaust gas G2 is more preferably 300 ° C. or more and 600 ° C. or less. When the temperature of the exhaust gas G2 is less than 300 ° C., the rate at which once volatilized mercury is reattached to the dust side increases. On the other hand, when the temperature of the exhaust gas G2 is higher than 600 ° C., the rate at which once volatilized mercury is reattached to the dust side hardly changes, and the burden on the facility increases.

It is a flowchart which shows 1st Embodiment of the processing apparatus of the cement kiln exhaust gas concerning this invention. It is a flowchart which shows 2nd Embodiment of the processing apparatus of the cement kiln exhaust gas concerning this invention. It is a flowchart which shows 3rd Embodiment of the processing apparatus of the cement kiln waste gas concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cement kiln exhaust gas treatment device 2 Electric dust collector 3 Heating device 4 Hot air generator 5 Cyclone 6 Solid-gas separation device 7 Heat exchanger 8 Mercury recovery device 21 Cement kiln exhaust gas treatment device 22 Classification device 31 Cement kiln exhaust gas treatment Device 32 Granulator C Coarse powder side dust F Fine powder side dust D1 Coarse powder side dust D2 Fine powder side dust H Hot air G1-G5 Exhaust gas

Claims (6)

A dust collector for collecting dust contained in the exhaust gas of the cement kiln;
A heating device for heating the dust collected by the dust collector;
A solid-gas separation device comprising a ceramic filter for solid-gas separation of the exhaust gas containing the dust discharged from the heating device;
A cement kiln exhaust gas treatment apparatus, comprising: a mercury recovery device that recovers mercury present on a gas phase side of the gas separated by the solid-gas separation device.   The cement kiln exhaust gas treatment apparatus according to claim 1, wherein the heating device directly heats the dust collected by the dust collector with a gas.   The cement kiln exhaust gas treatment device according to claim 1 or 2, wherein the temperature of the exhaust gas containing the dust discharged from the heating device is 250 ° C or higher and 800 ° C or lower.   4. The apparatus according to claim 1, further comprising a classification device that classifies dust collected by the dust collection device, wherein the heating device heats dust on a fine powder side classified by the classification device. The cement kiln exhaust gas treatment apparatus as described.   It comprises a granulator for granulating the dust collected by the dust collector, and the heating device heats the granulated material obtained by the granulator. 3. The cement kiln exhaust gas treatment apparatus according to 3. Collect dust contained in the exhaust gas of cement kiln,
Heat the collected dust,
The exhaust gas containing heated dust is solid-gas separated using a solid-gas separator equipped with a ceramic filter,
A method for treating a cement kiln exhaust gas, comprising recovering mercury present on the gas phase side of the gas separated by the solid-gas separation.

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