JP2009227531A - Method for reducing organic contaminant discharge amount and cement production unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for reducing an organic contaminant discharge amount by which the discharge of an organic contaminant from a cement production unit is reduced without deteriorating the heat efficiency of the cement production unit and the cement production unit applicable for the method. <P>SOLUTION: The method for reducing the organic contaminant discharge amount is carried out by treating dust contained in a waste gas from the cement production unit 10 by flotation to separate unburnt carbon contained in the dust and charging the unburnt carbon to a high temperature part (a part exhibiting ≥800°C) such as a third cyclone 3c, a forth cyclone 3d, a calcining furnace 4 or a rotary kiln 5 of the cement production unit 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for reducing the discharge amount of organic pollutants (POPs, persistent organic pollutants) such as dioxins from a cement manufacturing apparatus and a cement manufacturing apparatus to which the method can be applied.

  In recent years, wastes containing organic pollutants such as coal ash, dust (fly ash), burning husk (main ash), sludge, slag and the like have been used as a part of cement raw materials. Among these wastes, those having a relatively high content of organic pollutants are placed in the kiln bottom of the calcining furnace 4 or rotary kiln 5 in the cement manufacturing apparatus 10 shown in FIG. 1 and can decompose organic pollutants. Used below. On the other hand, since other wastes are put into the preheater 3 together with other cement raw materials, the organic pollutants contained in these wastes are not completely decomposed and partly volatilize in the exhaust gas. Will remain. Even if the organic pollutant is once decomposed, it may be re-synthesized between the outlet of the preheater 3 and the dust collector 7.

  Thus, most of the organic pollutants in the undecomposed or re-synthesized exhaust gas are adsorbed on the surface of the dust contained in the exhaust gas as the temperature of the exhaust gas decreases. And the dust which the organic pollutant adsorb | sucked to the surface is collected by the dust collector 7, is supplied to the preheater 3 as a cement raw material, and one part is decomposed | disassembled by the temperature. That is, some of the organic pollutants generated during the manufacture of cement are decomposed in a high temperature range, and most of the undecomposed organic pollutants circulate in the cement manufacturing apparatus 10 using dust in the exhaust gas as a medium. Yes. However, a small amount of organic pollutants and gaseous organic pollutants that are not adsorbed by dust have been discharged into the atmosphere together with exhaust gas. For this reason, it is considered desirable to further reduce the emission of these organic pollutants.

Under such circumstances, various techniques for decomposing organic pollutants such as POPs contained in the exhaust gas from the cement manufacturing apparatus have been proposed. For example, dust containing organochlorine compounds in exhaust gas from a cement manufacturing apparatus is collected by a dust collector, and a part of the dust is heated to a high temperature part of 800 ° C. or higher such as a kiln bottom of a rotary kiln, a calcining furnace, a suspension preheater, etc. A method for promoting the decomposition of an organic chlorine compound by introducing it into the water has been proposed (see Patent Document 1).
JP 2004-244308 A

  The cement production equipment preheats the cement raw material using waste heat from the firing of the cement to improve thermal efficiency and save energy. However, the dust collected by the dust collector is at room temperature. For this reason, in the method described in Patent Document 1, normal temperature dust is put into a high-temperature part of 800 ° C. or higher, and the original material of the cement manufacturing apparatus that preheats the cement raw material using waste heat of cement firing is used. There is a problem that the system cannot be used and the thermal efficiency is lowered.

  In view of such a problem, the present invention provides an organic pollutant emission reduction method capable of reducing the discharge amount of organic pollutants from the cement manufacturing apparatus, without reducing the thermal efficiency of the cement manufacturing apparatus, and It aims at providing the cement manufacturing apparatus which can apply the said method.

  In order to solve the above problems, the present invention is a method for reducing the discharge amount of organic pollutants from a cement production apparatus, wherein dust contained in exhaust gas from the cement production apparatus is treated by flotation, An organic pollutant emission reduction method is provided, wherein unburned carbon contained in the dust is separated, and the unburned carbon is introduced into a portion of the cement manufacturing apparatus at 800 ° C. or higher (Claim 1). .

  Most of the organic pollutants volatilized in the cement production apparatus are deposited on the surface of unburned carbon in the dust contained in the exhaust gas from the cement production apparatus. Therefore, according to the said invention (invention 1), the unburned carbon in the dust contained in the exhaust gas is separated by flotation, and the separated unburned carbon is separated into the high temperature part of the cement manufacturing apparatus (site reaching 800 ° C. or higher). ), The decomposition of organic pollutants deposited on the surface of unburned carbon can be promoted, and the amount of organic pollutants discharged from the cement manufacturing apparatus can be reduced. Moreover, since the unburned carbon burns in the high temperature part by putting unburned carbon separated from the dust into the high temperature part of the cement manufacturing apparatus, there is also an effect that the thermal efficiency of the cement manufacturing apparatus is not lowered. .

  Here, in this specification, examples of the organic pollutant include organic chlorine compounds such as dioxin, polychlorinated biphenyl, and hexachlorobenzene.

  In the said invention (invention 1), it is preferable to isolate | separate the said unburned carbon by processing a part of said dust by flotation (invention 2), In this invention (invention 2), It is preferable that 5% by mass or more of the dust is treated by flotation to separate the unburned carbon (Claim 3).

  According to the above inventions (inventions 2 and 3), by separating unburned carbon from a part of the dust, the amount of organic pollutants in the circulation system of the cement manufacturing apparatus can be sufficiently reduced. There is no need to treat the entire amount of dust by flotation, and organic pollutant emissions can be reduced with simple operations.

  In the said invention (Inventions 1-3), the said cement manufacturing apparatus calcinates the preheater which has a some cyclone which preheats a cement raw material, the calcining furnace which calcines the cement raw material, and the cement raw material A kiln that generates a clinker, and the unburned carbon is selected from the group consisting of a cyclone located at the second and bottom stages of the preheater, the calciner, and the kiln. It is preferable to put it into the region (claim 4).

  The cyclones, calcining furnaces and kilns located in the second and bottom stages from the bottom of the preheater are high-temperature parts that reach 800 ° C. or higher in the cement production apparatus. According to the above invention (invention 4), Injecting unburned carbon into any of these parts can accelerate the decomposition of organic pollutants adsorbed on the surface of unburned carbon, reducing the amount of organic pollutants emitted from cement production equipment can do.

  The present invention also includes a preheater having a plurality of cyclones for preheating cement raw material, a calcining furnace for calcining the cement raw material, a kiln for firing the cement raw material to produce clinker, and an exhaust gas from the kiln. A dust collector that collects dust in the exhaust gas, and a flotation separator that separates unburned carbon from the dust collected by the dust collector, wherein the unburned carbon is the unburned carbon. Is supplied to at least one portion selected from the group consisting of the cyclone located at the second and lowermost stages from the bottom of the preheater, the calcining furnace, and the kiln. (Claim 5).

  According to the above invention (invention 5), the unburned carbon in the dust contained in the exhaust gas is separated by flotation, and the separated unburned carbon is the high temperature part (a part reaching 800 ° C. or more) of the cement manufacturing apparatus. For example, it is possible to promote the decomposition of organic pollutants deposited on the surface of unburned carbon by introducing them into the second and lowermost cyclones, calcining furnaces, kilns, etc. from the bottom of the preheater. It is possible to reduce the amount of organic pollutants discharged from the cement manufacturing apparatus. Moreover, since unburned carbon thrown into the high temperature part burns in the said high temperature part, there also exists an effect that the thermal efficiency of a cement manufacturing apparatus is not reduced.

  According to the organic pollutant emission reduction method and the cement manufacturing apparatus of the present invention, the organic pollutant emission from the cement manufacturing apparatus can be reduced without lowering the thermal efficiency of the cement manufacturing apparatus.

Hereinafter, an organic pollutant emission reduction method according to an embodiment of the present invention will be described.
In the organic pollutant emission reduction method according to this embodiment, first, dust contained in the exhaust gas of the cement manufacturing apparatus is collected.

  As shown in FIG. 1, the cement manufacturing apparatus 10 includes a dryer 1 for drying a cement raw material, a pulverizer 2 for pulverizing the cement raw material dried by the dryer 1, and a pulverizer 2 pulverizing to a predetermined particle size. Preheater 3 having first to fourth cyclones 3a to 3d for preliminarily heating the cement raw material, calcining furnace 4 for calcining the cement raw material, and preheated and calcined cement raw material From a rotary kiln 5 that produces clinker by baking, a finishing mill 6 that produces cement from the clinker produced by the rotary kiln 5, a dust collector 7 that collects dust contained in exhaust gas from the rotary kiln 5, and a cement production apparatus 10 A chimney 8 that discharges the exhaust gas of the gas and a flotation beneficiation tank 9 that performs a flotation process on the dust collected by the dust collector 7. In FIG. 1, an arrow indicated by a broken line indicates a flow of exhaust gas from the preheater 3.

  The dust collector 7 is a device for collecting dust contained in the exhaust gas from the cement manufacturing apparatus and adsorbed on the surface thereof, and examples of the dust collector 7 include an electric dust collector, a gravity dust collector, an inertial dust collector, A centrifugal dust collector, a filtration dust collector, etc. are mentioned.

  In such a cement manufacturing apparatus 10, a cement raw material partially containing waste containing organic pollutants is dried by a dryer 1 as necessary and pulverized to a predetermined particle size by a pulverizer 2. Examples of the waste containing organic pollutants include, but are not limited to, coal ash, dust, burned husk, sludge, and mines.

  The cement raw material pulverized by the pulverizer 2 is put into the upper portion of the preheater 3 (a duct connecting the first cyclone 3a and the second cyclone 3b). The cement raw material charged into the upper portion of the preheater 3 is preliminarily heated through the first to third cyclones 3 a to 3 c, the calcining furnace 4 and the fourth cyclone 3 d and supplied to the rotary kiln 5.

  The cement raw material supplied into the rotary kiln 5 is fired at a temperature of about 1500 ° C., thereby generating a clinker. The produced clinker is discharged from the rotary kiln 5 and crushed in the finishing mill 6 after gypsum and the like are added. Thereby, a desired cement is manufactured.

  Exhaust gas generated when the cement raw material is fired in the rotary kiln 5 is discharged from the rotary kiln 5, the calcining furnace 4, the fourth cyclone 3 d of the suspension preheater 3 to the first cyclone 3 a, the pulverizer 2 or the dryer 1. Then, it is introduced into the dust collector 7 (see broken line arrow in FIG. 1).

  The exhaust gas from the rotary kiln 5 contains a part of the organic pollutant contained in the cement raw material without being completely decomposed and volatilized, and also contains dust. The organic pollutant in the exhaust gas is adsorbed on the surface of the dust as the temperature of the exhaust gas decreases, and the dust on which the organic pollutant is adsorbed on the surface is introduced into the dust collector 7 together with the exhaust gas.

  The dust introduced into the dust collector 7 is collected by the dust collector 7 and the exhaust gas is discharged from the chimney 8. The dust collected by the dust collector 7 is temporarily stored in a dust storage tank (not shown).

  Part of the dust collected in this way is introduced into the flotation tank 9, and processing by flotation is performed. Specifically, water is added to a part of the collected dust and stirred to prepare a slurry. A trapping agent is added to the slurry and further stirred. Thereby, the surface of the unburned carbon in the dust can be modified and hydrophobized. In addition, what is necessary is just to use what is generally used as a collection agent in a flotation process, such as kerosene (kerosene), light oil, and heavy oil, as a collection agent.

  The amount of the collecting agent added to the slurry is not particularly limited and can be appropriately changed according to the amount of dust in the slurry. For example, 0.1 to 0.1 g of dust in the slurry. What is necessary is just to add 2 mL.

  It is also considered that the amount of organic pollutant discharged from the cement manufacturing apparatus 10 can be further reduced by performing the flotation process on the total amount of dust collected by the dust collector 7 in the flotation tank 9. However, generally, in the dust collector 7 of the cement manufacturing apparatus 10, a large amount of dust of 20 to 50 t is collected per hour. Therefore, when the total amount of dust is the target of the flotation process, the amount of dust to be processed is large. It may increase, and the flotation process may become complicated. Therefore, it is preferable to perform the flotation process on a part of the collected dust, specifically at least 5% by mass, preferably 10-30% by mass. If it is less than 5% by mass, the amount of organic pollutants in the circulation system of the cement production apparatus may not be effectively reduced.

  The slurry to which the scavenger is added is introduced into the flotation tank 9 and a foaming agent such as methyl isobutyl carbinol (MIBC) is added. As a result, bubbles are generated in the flotation tank 9, and unburned carbon adheres and floats on the bubbles, and the remaining dust settles without adhering to the bubbles. In this way, unburned carbon can be separated and recovered.

  The amount of the foaming agent added to the slurry is not particularly limited as long as it is an amount capable of generating bubbles to the extent that unburned carbon in the slurry can be attached and floated. For example, 1000 mL of water and dust What is necessary is just to add 0.1-1 mg foaming agent with respect to a 100-g slurry.

  The unburned carbon separated in this way is put into a high temperature part that reaches 800 ° C. or higher. Specifically, it is preferable to put into at least one portion selected from the group consisting of the third cyclone 3c, the fourth cyclone 3d, the calcining furnace 4, and the rotary kiln 5 of the preheater 3. Since most of the organic pollutants that have been volatilized in the exhaust gas are adsorbed on the surface of the separated unburned carbon, by introducing the unburned carbon separated into these high-temperature parts, The decomposition of organic pollutants adsorbed on the surface of unburned carbon can be promoted, and the amount of organic pollutants in the circulation system of the cement manufacturing apparatus 10 can be reduced. Organic pollutant emissions can be reduced. In particular, when the separated unburned carbon is reused as fuel in the cement manufacturing apparatus 10, it is preferable to put the unburned carbon into the calcining furnace 4 and / or the rotary kiln 5.

  The remainder of the dust settled in the flotation tank 9 (the remainder after separation of unburned carbon) and the remainder of the dust that has not been subjected to the flotation process are dried as necessary, and then the first of the cement production apparatus 10. The cyclone 3a and the second cyclone 3b are reintroduced as part of the cement raw material.

  According to the organic pollutant emission reduction method according to the present embodiment described above, most of the organic pollutants contained in the exhaust gas are adsorbed on the surface of the unburned carbon, and the unburned carbon is absorbed in the high temperature part of the cement manufacturing apparatus. It is possible to accelerate the decomposition of organic pollutants and reduce the amount of organic pollutants discharged from the cement manufacturing apparatus. In particular, since it is only necessary to perform flotation processing on part of the dust collected by the dust collector, the amount of dust to be processed is small, the flotation processing is not complicated, and organic pollutants are efficiently removed. Can do. Furthermore, since the unburned carbon is burned in the high temperature portion by introducing unburned carbon into the high temperature portion, there is also an effect that the thermal efficiency of the cement manufacturing apparatus is not lowered.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

[Example 1]
In the cement manufacturing apparatus 10 shown in FIG. 1, cement is manufactured using waste (coal ash, dust, sludge, slag, etc.) as part of the cement raw material, and the exhaust gas is discharged from the dust collector 7 of the cement manufacturing apparatus 10. The dust contained in was collected. In addition, when the density | concentration of PCB contained in the extract | collected dust was measured according to JIS-K0311, it was 500 ng / g.

  To 100 g of the dust collected as described above, 1000 mL of distilled water was added with stirring to prepare a slurry. 1 mL of kerosene was added to this slurry and stirred with a mixer to make the surface of unburned carbon in the dust hydrophobic. After hydrophobization, the slurry was introduced into a flotation machine, 0.1 mg of MIBC (methyl isobutyl carbinol) was added as a foaming agent to generate bubbles, and the unburned carbon that adhered to and floated on the generated bubbles, Recovered as an overflow. The collected levitated matter (unburned carbon) and the remainder remaining in the floatation machine were dried.

The PCB concentration was measured in accordance with JIS-K0311 for each of the floated material (unburned carbon) obtained by the flotation treatment and the remainder after the flotation treatment.
The results are shown in Table 1.

  As shown in Table 1, it was confirmed that PCB was concentrated to a high concentration in the unburned carbon separated by subjecting the dust to the flotation process. Moreover, since the unburned carbon contained in the dust is about 1% by mass of the total amount of dust, by putting the separated unburned carbon into the high temperature part of the cement manufacturing apparatus 10, the amount of input to the high temperature part can be reduced. It can be suppressed to a minimum, and the decomposition of organic pollutants adsorbed on the surface of dust can be promoted, so that it is considered that the amount of organic pollutants discharged from the cement manufacturing apparatus can be reduced.

[Examples 2 and 3, Comparative Example 1]
About 5% by mass of the dust collected by the dust collector 7 of the cement manufacturing apparatus 10 shown in FIG. 1, the flotation process is performed in the same manner as in Example 1 to separate the unburned carbon, and the separated unburned carbon is removed. It put into the calcining furnace 4 of the cement manufacturing apparatus 10. Then, the residue settled in the flotation machine is put into the upper part of the preheater 3 (the duct connecting the first cyclone 3a and the second cyclone 3b) of the cement manufacturing apparatus 10 shown in FIG. About 95 mass%, without performing any process, it injected into the preheater 3 upper part of the cement manufacturing apparatus 10 shown in FIG. 1, and measured the PCB density | concentration in waste gas based on JIS-K0311 (Example 2).
The results are shown in Table 2.

Except that 10% by mass of dust collected by the dust collector 7 of the cement manufacturing apparatus 10 shown in FIG. The PCB concentration was measured (Example 3).
The results are shown in Table 2.

As a comparative example, the total amount of dust collected by the dust collector 7 of the cement manufacturing apparatus 10 shown in FIG. 1 is used to treat the upper part of the preheater 3 of the cement manufacturing apparatus 10 (the first cyclone 3a and the second cyclone) without any treatment. 3b), and the PCB concentration in the exhaust gas was measured in the same manner as in Example 2 (Comparative Example 1).
The results are shown in Table 2.

  As shown in Table 2, unburned carbon was separated by flotation treatment with respect to 5% by mass of the dust collection dust as in Example 2, and the unburned carbon was separated from the high temperature portion (the third portion of the cement manufacturing apparatus 10). Cyclone 3c, fourth cyclone 3d, calcining furnace 4, rotary kiln 5, etc.) were confirmed to be able to effectively reduce organic pollutant emissions from cement manufacturing equipment. Moreover, it was confirmed that the amount of organic pollutants discharged from the cement manufacturing apparatus can be more effectively reduced by setting the amount of dust subjected to the flotation treatment to 10% by mass as in Example 3. In this way, only a part of the dust collected by the dust collector is subjected to the flotation process to separate the unburned carbon, and the separated unburned carbon is put into the high temperature part of the cement manufacturing apparatus, so that the cement manufacturing apparatus It is considered that the amount of organic pollutants in the circulation system can be sufficiently reduced.

  The organic pollutant emission reduction method of the present invention can efficiently remove organic pollutants contained in exhaust gas by simple processing, and can reduce the amount of organic pollutants discharged from a cement manufacturing apparatus. Useful for.

It is a schematic block diagram which shows the cement manufacturing apparatus which concerns on one Embodiment of this invention.

Explanation of symbols

3 ... Preheater 3c ... 3rd cyclone (the cyclone located in the 2nd stage from the bottom)
3d ... Fourth cyclone (the cyclone located at the bottom)
4 ... Calciner 5 ... Rotary kiln (kiln)
7 ... Dust collector 9 ... Flotation tank 10 ... Cement production equipment

Claims (5)

A method for reducing organic pollutant emissions from cement manufacturing equipment,
Treating the dust contained in the exhaust gas from the cement production apparatus by flotation, separating unburned carbon contained in the dust,
An organic pollutant emission reduction method, wherein the unburned carbon is introduced into a portion of the cement manufacturing apparatus at 800 ° C. or higher.   The organic pollutant emission reduction method according to claim 1, wherein a part of the dust is treated by flotation to separate the unburned carbon.   The organic pollutant emission reduction method according to claim 2, wherein 5% by mass or more of the dust is treated by flotation to separate the unburned carbon. The cement manufacturing apparatus includes a preheater having a plurality of cyclones for preheating the cement raw material, a calcining furnace for calcining the cement raw material, and a kiln for firing the cement raw material to generate a clinker,
The unburned carbon is charged into at least one portion selected from the group consisting of the cyclone located at the second and bottom stages of the preheater, the calcining furnace, and the kiln. The organic pollutant discharge | emission reduction method in any one of 1-3. A preheater having a plurality of cyclones for preheating the cement raw material, a calcining furnace for calcining the cement raw material, a kiln for firing the cement raw material to generate clinker, and an exhaust gas path from the kiln, A dust collector that collects dust in the exhaust gas, and a floatation machine that separates unburned carbon from the dust collected by the dust collector,
The cement is characterized in that the unburned carbon is charged into at least one part selected from the group consisting of the cyclone located in the second and bottom stages from the bottom of the preheater, the calciner, and the kiln. Manufacturing equipment.

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