JP4032673B2 - Sludge treatment method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sludge treatment method in which sludge is introduced into a cement firing process and incinerated.
[0002]
[Prior art]
Most of the sludge discharged from sewage treatment plants is disposed of by land reclamation and ocean dumping. However, sewage sludge emissions from sewage treatment plants are increasing steadily, especially in urban areas, and due to the shortage of landfills for land reclamation and ocean dumping, as well as restrictions on preventing environmental pollution, At present, sludge treatment has shifted to incineration. As a method for incinerating this sludge, recently, a method of putting it into a firing process of a cement manufacturing plant has attracted attention. In this case, the ammonia component contained in the sludge has a function of reducing and decomposing nitrogen oxides contained in the exhaust gas when it is introduced into the exhaust gas of the rotary kiln from a high temperature part such as a kiln bottom in the cement firing process. Yes, the effect is also attracting attention.
[0003]
[Problems to be solved by the invention]
However, as the amount of sludge to be treated increases, the ammonia component in the sewage sludge input to the kiln bottom is not completely decomposed, but rides on the kiln exhaust gas flowing from the bottom to the top of the preheater. There was a phenomenon of going out of the preheater. This gas was discharged from the chimney after the electrostatic precipitator through the raw material mill and dryer to the outside air, and it was found that the exhaust concentration also fluctuated. As countermeasures, atomization of sludge and dispersed input were attempted. However, although these methods had some effects, they did not achieve complete ammonia decomposition. For this reason, in order to treat a large amount of sludge, it is necessary to directly contact the higher-temperature kiln exhaust than to treat the sludge in the housing or the preheater, or to ensure that the sludge incineration process is performed in the kiln. It turns out that is important.
[0004]
In view of the above circumstances, the present invention provides a method for treating sludge that can completely decompose the ammonia component in the sludge that has been input to the cement firing step and that does not cause the ammonia component to leak out of the preheater. Objective.
[0005]
[Means for Solving the Problems]
According to the first aspect of the present invention, in the sludge treatment method for producing cement clinker by introducing sludge into the cement firing step, the sludge introduction point is set in the middle of the raw material chute of the lowermost cyclone of the preheater in the cement firing step. The sludge is placed on the cement raw material flowing through the raw material chute .
[0006]
In this invention, in the middle of the raw material chute of the lowermost cyclone of the preheater, since the sludge is directly put on the cement raw material flowing through the raw material chute , the sludge can be burned quickly at high temperature, The ammonia component can be easily decomposed. In this case, the residence time can be increased and the decomposition of the ammonia component can be promoted as the sludge charging place is lowered. Here, the introduction of the sludge may be performed in a state of being dispersed using a dispersion medium such as air, or may be performed in a lump without being dispersed. In the latter case, the sludge lump can be dropped onto the raw material flowing on the bottom of the housing, and the sludge lump remaining on the raw material reaches directly inside the kiln at 1100 ° C or higher rotating from the kiln bottom of the kiln. It is also possible to increase the ratio to be generated. Thus, combustion of the ammonia component can be promoted, and leakage of the ammonia component from the preheater to the outside can be prevented.
[0010]
Further, in order to have set-up point of the sludge in the middle of the raw material chute lowermost cyclone, even when charged with sludge granular or massive, sludge can be a place smoothly on top of the raw material flowing in the kiln It becomes possible to enter.
[0013]
The invention according to claim 2 is characterized in that, in the invention according to claim 1, the input points of the sludge are provided dispersedly at a plurality of locations.
[0014]
By dispersing and introducing sludge at a plurality of input points as in the present invention, the combustion conditions at each input location can be increased, and complete decomposition of the ammonia component can be promoted.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing an outline of a cement production facility for carrying out the treatment method of the present invention. In the figure, this cement production facility includes a raw material storage 1 for storing cement raw materials made of limestone, clay, silica, and iron raw materials, a raw material mill 2 for pulverizing and mixing raw materials, an electrostatic precipitator 3, a clay dryer 4, and a raw material mixing storage silo 5 , Preheater 6, rotary kiln 7, clinker cooler 8, clinker silo 9, finishing mill 10, cement silo 11, and the like.
[0016]
Cement raw materials (limestone, clay, silica stone, and iron raw materials) are introduced into the raw material mill 2 through a dryer 4 as necessary. These raw materials are pulverized by the raw material mill 2 and introduced into the raw material mixing and storage silo 5, and then preheated by the preheater 6, and then put into a rotary kiln 7 for cement firing and fired to become a cement clinker, After being cooled by the clinker cooler 8, it is introduced into the clinker silo 9.
[0017]
The preheater 6 is of a multistage cyclone type in which a plurality of cyclones are connected in multiple stages, and preheats the crushed cement raw material to a predetermined temperature (800 to 900 ° C.) using the exhaust of the rotary kiln 7. The rotary kiln 7 has a horizontal cylindrical kiln shell that is slightly inclined downward to the downstream side. While rotating the kiln shell around its central axis, the fuel kiln is heated with a burner using heavy oil or fine coal as a fuel. The cement raw material is heated to a temperature of 1450 ° C. or higher and subjected to a firing reaction to produce a cement clinker.
[0018]
As shown in FIG. 2, the collected raw material of the second cyclone 34 from the bottom of the preheater 6 enters the riser duct 32 through the raw material chute 31. Here, the riser duct 32 joins with the kiln exhaust flowing upward from below, enters the lowest cyclone 33, and the raw material powder is separated and collected, and the inclined surface of the housing 20 through the raw material chute 30. And enter the kiln bottom 7a of the kiln 7. The clinker fired in the rotary kiln 7 is then cooled by a clinker cooler 8 connected to the front of the kiln 7 of the rotary kiln 7, stored in the clinker silo 9, and then sent to the finishing mill 10 in the finishing process.
[0019]
The finishing mill 10 finely pulverizes the clinker while mixing gypsum into the cement clinker produced in the firing step, and discharges the cement. Then, the cement discharged from the finishing mill 10 is introduced into the cement silo 11 and then sent to the supplier.
[0020]
Next, a method for treating sludge will be described.
As shown in FIG. 1 and FIG. 2 in which the main part is enlarged, this method is characterized in that sludge input points A to E are used for cement calcination when sludge K is added to the cement calcination process to produce cement clinker. That the raw material chute 31 of the second cyclone 34 from the bottom of the preheater 6 in the process includes the position where it joins with the riser duct 32 and is set to the range from below to the inside of the kiln bottom 7a of the rotary kiln 7 is there.
[0021]
Among the plurality of candidate charging points A to E, the charging point A includes a position where the raw material chute 31 of the second cyclone 34 from the bottom of the preheater 6 in the cement firing step is joined to the riser duct 32. This is either one of the surfaces of the riser duct 32 or the vertical surface of the housing 20 set in a range from the bottom to the inside of the kiln bottom 7 a of the rotary kiln 7. Further, the insertion point B is set on the inclined lower surface side of the bent portion 21 of the housing 20. The charging point C is set in the middle of the raw material chute 30 from the lowest cyclone. The charging point D is set on the upper surface side of the bent portion 21 of the housing 20. The charging point E is set inside the kiln bottom portion 7 a of the rotary kiln 7.
[0022]
As for the charging point A, sludge can be directly charged by opening a charging port on the wall of the riser duct 32 or the vertical wall of the housing 20. In addition, since the introduction point B is on the lower surface side of the housing 20 through which the raw material flows, the sludge K (indicated by an arrow) is introduced through the conduit 25 as shown in FIG. Also good. With respect to the charging point C, the raw material chute of the lowermost cyclone is directly provided with the charging port. Further, since the injection point E does not reach directly, as shown in FIG. 3B, a conduit 25 is provided in the housing 20, and sludge K (indicated by an arrow) is introduced through the conduit 25.
[0023]
Further, the insertion point D can be set to any point D1 to D3 on the upper surface side of the bent portion 21 of the housing 20, as shown in FIG. Also in this case, the sludge may be introduced by providing an opening directly on the wall of the housing 20, or the conduit may be attached to the housing 20 and introduced from the tip of the conduit. In addition, as shown in FIG. 4B, it is possible to set the input points at points D4 and D5 close to both sides.
[0024]
In addition, when introducing sludge, it is possible to completely decompose the ammonia component by dispersing with a dispersion medium in a high temperature region of 1000 ° C. or higher. It is preferable to lead to a high temperature region of 1100 ° C. or higher to gradually decompose the ammonia component. In addition, as the charging point is set to the low temperature region side, that is, within a range of 1000 ° C. or lower and 800 ° C. or higher, the closer to the point where the raw material of the second-stage cyclone enters the riser duct 32, It is preferable that the sludge is dropped to the housing 20 as a lump and is introduced into the kiln bottom 7a of the kiln 7 in a state where it is placed on the raw material flowing on the bottom surface.
[0025]
By introducing the sludge from the input points A to E as described above, the introduced sludge can be suddenly decomposed under high temperature conditions. Therefore, leakage of the ammonia component from the preheater 6 to the outside can be prevented. In particular, when the sludge is charged at the charging point D, the charged sludge can be brought into contact with a higher-temperature gas different from that in the preheater 6 and the decomposition of ammonia can be promoted. In addition, when the sludge is introduced at the input points B and C, even if the sludge is introduced in a granular or lump state, the sludge can be smoothly placed on the flowing raw material. It is possible to quickly enter the high temperature rotary kiln 7 and promote the decomposition of ammonia. In addition, when the sludge is introduced through the conduit 25 at the introduction point E, the introduced sludge is directly introduced into a rotating environment having an internal temperature of 1100 ° C. or higher, so there is no possibility of reverse scattering due to kiln exhaust. The ammonia component can be thermally decomposed under very high temperature conditions.
[0026]
【The invention's effect】
As described above, according to the first or second aspect of the invention, the introduced sludge can be suddenly decomposed under high temperature conditions, so that leakage of the ammonia component from the preheater to the outside can be reliably prevented. it can.
[0027]
In particular, even when granular or massive sludge is charged, the sludge can be smoothly put on the flowing raw material, and the charged sludge can be immediately reached to the high temperature region in the rotary kiln. It can be completely decomposed quickly. In addition, by dispersing and introducing sludge at a plurality of input points as in the invention of claim 2 , the combustion conditions at each input location can be increased, and the complete decomposition of the ammonia component can be further promoted. .
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic configuration diagram of a cement production facility for carrying out a treatment method of the present invention.
FIG. 2 is a diagram showing a sludge charging point in the present invention.
3A is a diagram showing an example in which sludge is supplied to a charging point B in FIG. 2 through a conduit, and FIG. 3B is a diagram in which sludge is supplied to a charging point E in FIG. 2 through a conduit. It is a figure which shows the example in the case of doing.
4A is a diagram showing the position of the insertion point D in FIG. 2 on the cross section of the housing, and FIG. 4B is a diagram showing a modification of the insertion point D. FIG.
[Explanation of symbols]
A to E Sludge input point K Sludge 6 Preheater 7 Rotary kiln 7a Kiln bottom 20 Housing 21 Curved portion 30 Lowermost cyclone raw material chute 31 Lower cyclone raw material chute 32 Riser duct 33 Lowermost cyclone 34 Lower 2nd cyclone from

Claims (2)

In the sludge treatment method for producing cement clinker by introducing sludge into the cement firing step, the sludge charging point is set in the middle of the raw material chute of the lowermost cyclone of the preheater in the cement firing step, and the sludge is used as the raw material. A method for treating sludge, characterized in that it is placed on a cement material flowing through a chute . The sludge treatment method according to claim 1, wherein the sludge charging points are distributed at a plurality of locations .

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