JP2003010896A - Sludge treatment method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To completely decompose ammonia components in sludge fed into a cement firing process. SOLUTION: In a method for treating sludge, in which sludge is put into a cement firing step to produce a cement clinker, sludge feeding points A to E are set such that a raw material chute 31 of the second cyclone 34 from the bottom of the preheater in the cement firing step.
Of the rotary kiln 7 was set so as to extend from the lower portion to the inside of the kiln butt 7a of the rotary kiln 7 including the position where it was joined to the riser duct 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sludge treatment method in which sludge is put into a cement burning step and incinerated for disposal.

[0002]

Most of the sludge discharged from a sewage treatment plant is disposed of by land reclamation and dumping at sea. However, sewage sludge emissions from sewage treatment plants are increasing steadily, especially in urban areas, and due to lack of landfills for land reclamation and dumping at sea, and restrictions on environmental pollution, The present situation is that sludge treatment is shifting to incineration. As a method of incinerating this sludge, a method of putting it into the firing process of a cement manufacturing plant has recently been attracting attention. In this case, the ammonia component contained in the sludge has an action of reducing and decomposing the 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 drawing attention.

[0003]

However, as the amount of sludge to be treated increases, the ammonia component in the sewage sludge introduced into the kiln tail is not completely decomposed even though it is a trace amount, and the preheater is operated from the bottom to the top. There was a phenomenon of getting out of the preheater by riding on the exhaust gas of the kiln flowing toward. It was found that this gas was exhausted to the outside air from the chimney after the electrostatic precipitator through the raw material mill and dryer, and the exhaust concentration also fluctuated. As a countermeasure, atomization of sludge and dispersion injection were tried. However, although these methods had some effects, they did not reach the point where ammonia decomposition was carried out completely. Therefore, in order to treat a large amount of sludge, it is necessary to directly contact the kiln exhaust with a higher temperature than to treat sludge in the housing or in the preheater, or to ensure that sludge incineration treatment is performed in the kiln. It turned out to be important.

In consideration of the above circumstances, the present invention provides a sludge treatment method capable of completely decomposing the ammonia component in sludge introduced into the cement burning step and preventing the ammonia component from leaking to the outside from the preheater. The purpose is to do.

[0005]

According to a first aspect of the present invention, there is provided a sludge treatment method for producing cement clinker by introducing sludge into a cement calcination step, wherein the sludge input point is under a preheater in the cement calcination step. It is characterized in that it is set in the range from below to the inside of the kiln bottom of the rotary kiln, including the position where the second raw material chute of the cyclone is joined to the riser duct.

[0006] In the present invention, sludge is introduced to a range from below to the inside of the kiln bottom of the rotary kiln including the position where the second raw material chute of the cyclone from the bottom of the preheater in the cement firing process joins the riser duct. Since it is directly charged, the sludge can be quickly burned at a high temperature, and the ammonia component can be easily decomposed. In this case, the lower the sludge charging place is, the longer the residence time can be and the more the decomposition of the ammonia component can be promoted. Here, the sludge may be charged in a state of being dispersed using a dispersion medium such as air, or may be in the form of lump without being dispersed. In the latter case, sludge lumps can be dropped onto the raw material that flows through the bottom of the housing, and the sludge lumps that remain on the raw material can reach the inside of the kiln at 1100 ° C or higher that is rotating from the kiln bottom of the kiln. It is also possible to increase the ratio.
In this way, combustion of the ammonia component can be promoted, and leakage of the ammonia component from the preheater to the outside can be prevented.

According to a second aspect of the present invention, in the first aspect, the sludge charging point is set on the upper surface side of the bent portion of the housing from the lowermost portion of the preheater to the kiln bottom portion of the rotary kiln.

In the kiln exhaust flowing from the rotary kiln to the preheater through the housing, the temperature of the upper surface of the bent portion of the housing becomes higher than that of the lower surface. In the invention of claim 2, since the sludge charging point is set in the high temperature region, it is possible to bring the charged sludge into contact with a higher temperature gas different from that in the preheater, and promote decomposition of ammonia. Can be made. Further, at this time, it was found that in this temperature range, the decomposition of ammonia also greatly progressed by dispersing sludge, but good results were obtained even in the lump form. This is because the distance from the drop point to the bottom of the housing to the raw material inlet of the kiln is small, and the massive sludge that has been introduced enters the kiln immediately after it has dropped to the bottom of the housing and gradually burned at high temperatures. Is.

According to a third aspect of the present invention, in the first aspect, the sludge charging point is the lower surface side of the inclined portion of the bent portion of the housing from the lowermost portion of the preheater to the kiln bottom portion of the rotary kiln, or the lowermost cyclone of the preheater. The feature is that it was set in the middle of the raw material chute.

The raw material exiting from the lowermost cyclone of the preheater moves through the raw material chute and slides on the inclined lower surface of the bent portion of the housing to enter the rotary kiln. On the lower surface,
Alternatively, a sludge injection point is set in the middle of the raw material chute of the bottom cyclone. Therefore, even when granular or massive sludge is added, the sludge can be smoothly placed on the flowing raw material and can be made to enter the kiln.

According to a fourth aspect of the present invention, in the first aspect, the sludge charging point is set inside the kiln bottom of the rotary kiln, and the bottom of the preheater and the kiln bottom of the rotary kiln are set up to the charging point. It is characterized by guiding sludge through a conduit attached to the housing between.

The point of introducing sludge is better in a high temperature range, and is best if it can be set inside the rotary kiln. Therefore, in the invention of claim 4, a sludge feeding point is set inside the kiln bottom of the rotary kiln, and the sludge is guided to the feeding point through a conduit attached to the housing. In this case, since the sludge that has been input can be directly input into the rotating kiln having an internal temperature of 1100 ° C. or higher, there is a possibility that the sludge will be scattered backward by the kiln exhaust as compared with the above three methods. It is small and pyrolyzes at high temperature with very high ammonia content. In this case, the sludge may be put in the kiln in a state of being dispersed by the dispersion medium, or may be put in the kiln as a lump. The surface of the conduit is coated with a refractory material to protect it from high temperatures.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the sludge feeding points are provided at a plurality of points dispersedly.

By dispersing and charging sludge at a plurality of charging points as in the present invention, the combustion conditions at each charging point can be increased and the complete decomposition of the ammonia component can be promoted.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an outline of cement manufacturing equipment for carrying out the treatment method of the present invention. In the figure,
This cement manufacturing facility includes a raw material storage 1 for storing a cement raw material made of limestone, clay, silica stone, and an iron raw material, a raw material mill 2 for pulverizing and mixing the raw materials, an electric dust collector 3, a clay dryer 4, a raw material mixing and storing silo 5, and a preheater 6. , Rotary kiln 7, clinker cooler 8, clinker silo 9, finishing mill 10, cement silo 11 and the like.

Cement raw materials (limestone, clay, silica stone, iron raw materials) are introduced into the raw material mill 2 via the dryer 4 as required. These raw materials are crushed by the raw material mill 2 and introduced into the raw material mixing / storing silo 5, after which they are preheated by the preheater 6 and then put into the rotary kiln 7 for cement firing and fired to form cement clinker, After being cooled by the clinker cooler 8, it is introduced into the clinker silo 9.

The preheater 6 is a multi-stage cyclone type in which a plurality of cyclones are connected in multiple stages, and the crushed cement raw material is preheated to a predetermined temperature (800 to 900 ° C.) using the exhaust gas of the rotary kiln 7. . The rotary kiln 7 has a horizontally-oriented cylindrical kiln shell that is slightly inclined downward toward the downstream side. While rotating this kiln shell around its central axis, it heats heavy oil or pulverized coal as a fuel with a burner, and the preheater 6 The cement raw material is heated to a temperature of 1450 ° C. or higher to cause a firing reaction to produce a cement clinker.

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 merges with the kiln exhaust flowing upward from below the riser duct 32, rises, enters the lowermost cyclone 33, the raw material powder is separated and collected, passes through the raw material chute 30, and the inclined surface of the housing 20. Flow into the kiln butt 7a of the kiln 7. The clinker fired in the rotary kiln 7 is then cooled by the clinker cooler 8 connected to the kiln front part of the rotary kiln 7, and the clinker silo 9
After being stored in the finishing mill 10, it is sent to the finishing mill 10 in the finishing process.

The finishing mill 10 finely grinds the clinker while mixing the gypsum with 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 supply destination.

Next, a method for treating sludge will be described. The characteristic of this method is that, as shown in FIG. 1 and FIG. 2 in which the main part is enlarged, when sludge K is put into a cement firing step to produce a cement clinker, the sludge feed points A to E are set to The preheater 6 of the process has a range from the bottom of the preheater 6 including the position where the raw material chute 31 of the cyclone 34 is joined to the riser duct 32 to the inside of the kiln bottom 7a of the rotary kiln 7. is there.

Of the plurality of candidate input points A to E, the input point A is the raw material chute 3 of the second cyclone 34 from the bottom of the preheater 6 in the cement firing process.
One of the surfaces of the riser duct 32 or the vertical surface of the housing 20, which is set in a range including a position where the riser duct 32 is joined to the riser duct 32 and extending from the bottom to the inside of the kiln butt portion 7a of the rotary kiln 7. The surface.
In addition, the loading point B is the bent portion 2 of the housing 20.
1 is set on the inclined lower surface side. Input point C
Is set in the middle of the raw material chute 30 from the lowermost cyclone. The closing point D is set on the upper surface side of the bent portion 21 of the housing 20. Input point E
Is set inside the kiln butt portion 7a of the rotary kiln 7.

Regarding the input point A, the sludge can be directly input by opening an input port in the wall of the riser duct 32 or the vertical wall of the housing 20. In addition, since the input point B is on the lower surface side of the housing 20 through which the raw material flows, sludge K (indicated by an arrow) may be introduced through the conduit 25 as shown in FIG. Good. Regarding the charging point C, a charging port is directly attached to the raw material chute of the lowermost cyclone. Further, since the input point E does not reach directly, the conduit 25 is provided in the housing 20 as shown in FIG. 3B, and the sludge K (indicated by an arrow) is introduced through the conduit 25.

The input point D is shown in FIG.
As shown in (a), it can be set at arbitrary points D1 to D3 on the upper surface side of the bent portion 21 of the housing 20.
Also in this case, an opening may be provided directly in the wall of the housing 20 to introduce the sludge, or a conduit may be attached to the housing 20 and introduced from the tip of the conduit. In addition, FIG.
It is also possible to set injection points at points D4 and D5 that are close to both sides, as shown in FIG.

When adding sludge, 100
In the high temperature range of 0 ° C or higher, it is possible to completely decompose the ammonia component by dispersing with a dispersion medium, but basically, the ammonia component is charged as a lump and introduced into the high temperature range of 1100 ° C or higher in the kiln. It is preferable to gradually decompose the ammonia component. It should be noted that, as the charging point is set to the low temperature region side, that is, in the range of 1000 ° C. or lower and 800 ° C. or higher, the closer to the point where the second stage cyclone raw material enters the riser duct 32, It is preferable that the sludge is dropped into the housing 20 in a lump form and is guided to the inside of the kiln butt portion 7a of the kiln 7 while being placed on the raw material flowing on the bottom surface thereof.

By introducing the sludge from the above-mentioned introduction points A to E, the introduced sludge can be suddenly decomposed under high temperature conditions. Therefore, it is possible to prevent leakage of the ammonia component from the preheater 6 to the outside. In particular, when the sludge is fed at the feeding point D, the fed 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. Also, input points B and C
When sludge is thrown in, even if sludge is thrown in the form of granules or lumps, the sludge can be smoothly placed on the flowing raw material, so the sludge can be quickly put in the high temperature rotary kiln 7 together with the raw material. It can be introduced, and the decomposition of ammonia can be promoted. In addition, when sludge is input at the input point E through the conduit 25,
Since the introduced sludge is directly introduced into a rotating environment having an internal temperature of 1100 ° C. or higher, the ammonia component can be thermally decomposed under a very high temperature condition without the possibility of backscattering due to the kiln exhaust.

[0026]

As described above, according to the first to fifth aspects of the present invention, since the sludge that has been introduced can be decomposed suddenly under high temperature conditions, the leakage of ammonia components from the preheater to the outside can be reliably prevented. can do.

In particular, by setting the sludge charging point as in the inventions of claims 2 and 4, it is possible to suddenly thermally decompose the injected sludge under high temperature conditions. Further, by setting the charging point as in the invention of claim 3, even when granular or massive sludge is charged, the sludge can be smoothly placed on the flowing raw material, and Can immediately reach the high temperature region in the rotary kiln, and can be completely decomposed quickly. In addition, as in the invention of claim 5, by dispersing sludge at a plurality of charging points and charging the sludge, the combustion conditions at each charging point can be increased, and the complete decomposition of the ammonia component can be further promoted. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a cement manufacturing facility for carrying out a treatment method of the present invention.

[Fig. 2] Fig. 2 is a diagram showing a point of introducing sludge in the present invention.

3 (a) is a diagram showing an example of supplying sludge to the input point B of FIG. 2 via a conduit, and FIG. 3 (b) is a diagram of supplying sludge to the input point E of FIG. 2 via a conduit. It is a figure which shows the example at the time of doing.

4A is a view showing a position of a loading point D in FIG. 2 on a cross section of the housing, and FIG. 4B is a loading point D.
It is a figure which shows the modification of.

[Explanation of symbols] A to E Sludge input points K sludge 6 preheater 7 Rotary kiln 7a Kiln buttocks 20 housing 21 bend 30 Cyclone material chute at the bottom 31 Second material cyclone from the bottom 32 riser duct 33 Cyclone at the bottom 34 Second cyclone from the bottom

Claims (5)

[Claims] 1. A method for treating sludge for producing cement clinker by introducing sludge into a cement calcination step, wherein the sludge input point is the second cyclone raw material chute from the bottom of the preheater in the cement calcination step as a riser duct. The sludge treatment method is characterized in that it is set in a range from a position below that to the inside of the kiln bottom of the rotary kiln including a position where the sludge is joined with. 2. The sludge treatment method according to claim 1, wherein the sludge feeding point is set on the upper surface side of the bent portion of the housing from the lowermost portion of the preheater to the kiln bottom portion of the rotary kiln. 3. The sludge charging point is set on the inclined lower surface side of the bent portion of the housing from the lowermost portion of the preheater to the kiln bottom portion of the rotary kiln, or in the middle of the raw material chute of the lowermost cyclone. The method for treating sludge according to claim 1. 4. The sludge charging point is set inside the kiln bottom of the rotary kiln, and sludge is passed up to the charging point through a conduit attached to a housing between the bottom of the preheater and the kiln bottom of the rotary kiln. The sludge treatment method according to claim 1, wherein the sludge is guided. 5. The sludge treatment method according to any one of claims 1 to 4, wherein the sludge charging points are provided at a plurality of points in a dispersed manner.