JP2005111374A - Organic sludge treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic sludge treatment method which is a method for treating organic sludge, such as sewage sludge, by burning in a firing furnace for cement clinker or the like, is free from a large fluctuation in temperature etc. in a furnace, such as the firing furnace, due to organic sludge moisture etc. even when the amount of treated organic sludge is relatively large, and does not require the enlargement, complication, etc. of devices attached to the firing furnace. <P>SOLUTION: The organic sludge treatment method comprises a process for mixing the organic sludge with wood waste, a process for fermenting the obtained mixture under an aerobic atmosphere to obtain the mixture of which the mass has been reduced, a process for feeding the obtained fermented mixture 12 into a rotary kiln 6 from the raw material inlet side of the kiln and burning the mixture with raw material 1 of the cement clinker. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for treating organic sludge such as sewage sludge, and more particularly to a method for treating organic sludge by fermenting it and then putting it in a firing furnace such as cement.

Sewage sludge generated at sewage treatment plants is mainly disposed of by being dumped in landfills or incinerated in an incinerator. In recent years, a technique for burning sewage sludge in a cement clinker manufacturing facility and treating it from the viewpoint of lack of landfill or prevention of environmental pollution has been developed.
For example, water-containing sludge such as sewage sludge is directly introduced into the kiln bottom part of a dry kiln or calcining furnace that produces cement clinker by burning cement raw material or incinerated by directly using a pump through piping. Has been proposed (Patent Document 1).

Further, there is provided a method for using sewage sludge, characterized in that sewage sludge is dehydrated and dried, and the dried sludge is mixed with quicklime to obtain a dry powder, and the powder is used as a raw material and fuel for cement production. It has been proposed (Patent Document 2). Here, as a specific example of means for dewatering and drying sewage sludge, a dryer having a special structure for drying while dewatering sludge is listed. Further, it is described that high-temperature steam generated from a boiler is used as a heat source for the dryer.
Further, a method for producing a cement is proposed in which sludge containing an odorous compound is brought into contact with a cement raw material in the drying step and / or pulverizing step of the cement raw material and then supplied to the firing step together with the cement raw material. (Patent Document 3).
Japanese Patent No. 3344448 JP-A-9-248600 JP 11-116290 A

In the technique of Patent Document 1, the hydrated sludge is introduced into the dry kiln in the form of a hydrated slurry. Therefore, if the amount of hydrated sludge introduced is large, the amount of heat energy consumed for the evaporation of moisture from the hydrated sludge is reduced. As a result, there is a problem that the quality of the resulting cement clinker becomes unstable due to large fluctuations in the kiln furnace temperature.
In the technique of Patent Document 2, a dryer is required to dehydrate and dry sewage sludge, and a boiler must be provided as a heat source for the dryer. There's a problem.

In the technique of Patent Literature 3, when the sludge is brought into contact with the cement raw material in the drying step and / or the pulverizing step of the cement raw material, a large amount of heat energy is required to remove the moisture of the sludge. Therefore, there exists a problem that the processing efficiency in the drying process etc. of a cement raw material falls compared with the case where a cement raw material is dried and grind | pulverized independently.
Therefore, the present invention is a method for treating organic sludge such as sewage sludge by burning it in a firing furnace such as cement clinker, and even if the amount of organic sludge treated is relatively large, It is possible to obtain a high-quality cement clinker, etc., without greatly changing the temperature in the furnace of the firing furnace, etc., and an organic device that does not require an increase in size or complexity of the equipment attached to the firing furnace. It aims at providing the processing method of sludge.

  As a result of intensive studies to solve the above problems, the present inventor fermented organic sludge in an aerobic atmosphere to obtain organic sludge having a reduced mass. If the material is introduced into the furnace from the raw material inlet side of a kiln such as a rotary kiln and burned together with the calcined raw material such as a cement clinker raw material, the object of the present invention can be achieved, and organic sludge is fermented. When processing, adding a breathability improving material such as wood chips and mixing, the mass of organic sludge can be greatly reduced in a short period of time, and more efficient processing can be achieved. completed.

That is, the organic sludge treatment method of the present invention (Claim 1) includes a fermentation process in which organic sludge is fermented in an aerobic atmosphere to obtain organic sludge having a reduced mass, and the organic sludge having a reduced mass. And a combustion step in which the material is introduced into the furnace from the raw material inlet side of the firing furnace and burned together with the fired raw material.
A preferred embodiment of the method for treating organic sludge according to the present invention is a mixing step of mixing organic sludge and an air permeability improving material to obtain an organic mixture, and subjecting the organic mixture to a fermentation treatment in an aerobic atmosphere. A fermentation process for obtaining a reduced organic mixture, and a combustion process in which the reduced organic mixture is introduced into the furnace from the raw material inlet side of the firing furnace and combusted together with the fired raw material (Claim 2). .

Here, in the mixing step, the moisture content of the air permeability improving material is preferably 50% by mass or less (Claim 3).
Examples of the air permeability improving material include wood waste, fiber waste, rubber waste, waste paper, waste plastic, waste tire, waste PET bottle, plastic container packaging, polystyrene foam, rice straw, sawdust, rice husk, bark, perlite, vermicul One or more selected from the group consisting of light, lightweight aggregate, and waste ALC can be used.
As a pre-process of the mixing process, a process of crushing or pulverizing the air permeability improving material can be included (claim 5).
In the mixing step, the blending amount of the air permeability improving material with respect to 100 parts by mass of the organic sludge is preferably 1 to 500 parts by mass (Claim 6).
In the method for treating organic sludge according to the present invention, in the fermentation step, the fermentation treatment is preferably performed until the mass of the organic sludge is reduced by 10% or more with respect to the mass of the organic sludge before fermentation (Claim 7). .
The organic sludge is, for example, sewage sludge (claim 8).
An example of the organic sludge treatment method of the present invention is such that, for example, the firing furnace is a rotary kiln, and the firing raw material is a cement clinker raw material (claim 9).

According to the organic sludge treatment method of the present invention, even if the amount of organic sludge treated is relatively large, the moisture and solid content (combustible organic matter) contained in the fermented organic sludge that is put into the firing furnace. The amount of the component etc.) is greatly reduced compared with that before fermentation, so that the furnace temperature and the like of the firing furnace do not fluctuate greatly depending on the moisture and solid content derived from organic sludge.
In addition, according to the organic sludge treatment method of the present invention, it is not necessary to provide a dryer or the like that requires a large amount of thermal energy. Organic sludge can be treated with the cement production equipment as it is or with some modifications.
Furthermore, if air permeability improving materials such as wood chips are used, the amount of moisture and solids contained in the organic sludge can be greatly reduced in a short period of time, increasing the throughput of organic sludge and improving the treatment efficiency. Can be achieved.

  A preferred embodiment of the method for treating organic sludge according to the present invention includes (A) a mixing step of mixing organic sludge and an air permeability improving material to obtain an organic mixture, and (B) fermentation of the organic mixture in an aerobic atmosphere. A fermentation process to obtain an organic mixture having a reduced mass, and (C) a combustion process in which the organic mixture having a reduced mass is introduced into the furnace from the raw material inlet side of the firing furnace and combusted together with the fired raw material. Is included. Hereinafter, these steps will be described in detail.

[A. Mixing process]
The mixing step is a step of mixing the organic sludge and the air permeability improving material to obtain an organic mixture.
Examples of the organic sludge include sewage sludge, human waste sludge (septic tank sludge, agricultural settlement drainage sludge), food wastewater sludge, auko and bottom mud, and the like. In addition, the food processing residue can be treated in the same manner. Examples of food processing residue include beer residue, shochu residue, okara (tofu residue), sugar residue, fruit juice residue, coffee residue, tea residue, livestock residue and the like.
The sewage sludge is a treated product obtained after treating sewage at a sewage treatment plant.
The sewage sludge used as a raw material in the mixing step (A) is dehydrated sludge after dehydration by a machine such as vacuum dehydration, pressure dehydration, and centrifugal separation. The dewatered sludge contains about 55 to 85% by mass of water and about 15 to 45% by mass of solids. The content of organic matter in the solid content differs depending on whether or not anaerobic digestion treatment is performed, about 40% by mass in the case of digested sludge subjected to anaerobic digestion, and about 60% in the case of raw sludge not subjected to anaerobic digestion. %.
The air permeability improving material may be any material that can promote fermentation in an aerobic atmosphere of organic sludge and can be fired in the combustion step (C), which is a subsequent step. Textile waste, rubber waste, paper waste, waste plastic, waste tires, waste PET bottles, plastic containers and packaging, polystyrene foam, rice straw, sawdust, rice husk, bark, perlite, vermiculite, lightweight aggregate, waste ALC, etc. It is done. These materials are preferably crushed or pulverized to an appropriate size in advance.
As the air permeability improving material, a material that is not affected by fermentation and does not substantially decrease in mass even when fermented together with organic sludge is used. By not being affected by fermentation in this way, the role as an air permeability improving material can be maintained during the fermentation period.
The moisture content contained in the air permeability improving material is preferably 50% by mass or less, more preferably 30% by mass or less, and particularly preferably 10% by mass or less. When the moisture content exceeds 50% by mass, the amount of heat energy used for evaporation of moisture in the breathability improving material increases in the subsequent combustion step (C), and the temperature in the firing furnace is maintained. It is not preferable because it may adversely affect the above.
The maximum dimension of the breathability improving material (for example, the maximum diameter in the case of a spherical shape) is preferably 0.5 to 150 mm, more preferably 2.0 to 100 mm, and particularly preferably 10 to 100 mm. If the maximum dimension is less than 0.5 mm, the effect of improving air permeability may be insufficient, and if the maximum dimension exceeds 150 mm, the mixing property with organic sludge may deteriorate.

Among the breathability improving materials, wood scrap can be easily obtained in a shape and size suitable for promoting the fermentation of organic sludge, and it becomes a heat source by itself without generating harmful gases during combustion. It is preferably used from the viewpoint of generating thermal energy.
The shape of the wood chips is preferably a rod shape. When the wood chips are rod-shaped, a larger number of voids having good air circulation can be formed when mixed with organic sludge, compared to other shapes (such as lumps) of the same mass.

The blending amount of the air permeability improving material is preferably 1 to 500 parts by mass, more preferably 5 to 300 parts by mass, and particularly preferably 10 to 200 parts by mass with respect to 100 parts by mass of the organic sludge. If the blending amount is less than 1 part by mass, the effect of improving the air permeability may be insufficient, and the efficiency of the fermentation treatment may be reduced. Even if the blending amount exceeds 500 parts by mass, the fermentation treatment can be suitably performed, but since the amount of the air permeability improving material with respect to the organic sludge treatment amount is remarkably increased, the scale of the facility with respect to the organic sludge treatment amount is increased, It is not preferable in terms of processing efficiency.
As a means for mixing the organic sludge and the air permeability improving material, for example, a mixer having a stirring blade is used.
In addition, in this invention, even if it does not use a breathability improving material, use of a breathability improving material is abbreviate | omitted when fermentation in aerobic atmosphere in the fermentation process (B) of the next process progresses favorably. be able to.
The content of water contained in the organic mixture obtained by mixing the organic sludge and the air permeability improving material is preferably 60% by mass or less, more preferably 55% by mass or less, and particularly preferably 50% by mass or less. If the content is 60% by mass or less, the temperature fluctuation in the firing furnace in the subsequent combustion step (C) can be suppressed to a small level, and a high-quality cement clinker or the like can be obtained.

[B. Fermentation process]
In this step, the organic mixture obtained in the mixing step (A) is fermented in an aerobic atmosphere to obtain an organic mixture having a reduced mass.
This step is performed, for example, by depositing an organic mixture in a layered form so as to have an appropriate thickness in the presence of microorganisms necessary for fermentation in a place where air circulation is good. It is carried out by leaving it for a predetermined period while appropriately switching back. By this fermentation treatment, self-heating that reaches 60 ° C. or more at the maximum temperature occurs, evaporation of water due to self-heating, and decomposition of organic matter by microorganisms proceed, and the mass of moisture and solids contained in organic sludge increases. Both are greatly reduced.
The thickness of the organic mixture deposit is, for example, about 30 to 300 cm.
When the thickness of the deposit exceeds 100 cm, the amount of air inside the deposit may be insufficient. In this case, it is necessary to supply air to the inside of the deposit with a blower or the like as appropriate. When air is sufficiently supplied to the inside of the deposit, it is not particularly necessary to turn over, but it is preferable to turn over once every 1 to 7 days in order to further promote the fermentation process.
In this step, an inoculum can be used as appropriate in order to improve the efficiency of the fermentation treatment. Examples of the fungus used as inoculum include, for example, Azotobacter, Pseudomonas, Bacillus, Micrococcus, Penicillium, Aspergillus, Cochilioborus, Actinomycetes, Streptomyces, Actinomyces, Actinoplanes, etc. Is mentioned.
As a form of use of the inoculum, in addition to a use form in which the inoculum is preliminarily supported on a breathability improving material, a use form in which a liquid containing the inoculum is directly mixed is also possible.
As the inoculum, a commercially available one may be used, or a processed product in an aerobic fermentation treatment facility other than the fermentation treatment facility used in the treatment method of the present invention may be used.
When performing this process repeatedly, the organic mixture after the fermentation process of this process can be used as an inoculum.

The fermentation time of the organic mixture (the time for which the sediment is left) is preferably 10% by mass or more, more preferably 30% of the mass of the organic sludge in the fermentation process compared to before the start of fermentation due to evaporation of water and decomposition of the organic matter. It is defined as the time until the mass is reduced by mass% or more, particularly preferably 50 mass% or more.
Specifically, the fermentation time is preferably 2 days or longer, more preferably 5 days or longer, and particularly preferably 8 days or longer, although it varies depending on the type of organic sludge, the presence / absence and type of the air permeability improving material. Although the upper limit of fermentation time is not specifically limited, From the viewpoint of processing efficiency, it is usually within 20 days.
The organic mixture after the fermentation treatment in the fermentation process is less septic and less odorous than the organic mixture before the treatment due to the reduction of moisture and the decomposition of easily decomposable organic matter. This improves the performance, enables long-term storage, and eliminates the need for transportation in a sealed container.
The air permeability improving material can be reused by sieving from the organic mixture after completion of the fermentation process in the fermentation step. As a sieving method, trommel or the like is preferably used. At this time, since the organic matter adhering to the surface of the air permeability improving material contains the inoculum and can improve the efficiency of the fermentation treatment, it is not necessary to completely remove it from the air permeability improving material and can be reused.

[C. Combustion process]
In this process, an organic mixture having a reduced mass (specifically, a mixture of organic sludge and air permeability improving material fermented) is introduced into the furnace from the raw material inlet side of the calcining furnace, together with the calcined raw material. It is a process of burning.
As the firing furnace, either a batch type or a continuous type may be used, but a continuous type is preferable from the viewpoint of processing efficiency. Examples of the continuous firing furnace include a rotary kiln.
Examples of the firing raw material include a cement clinker raw material. The raw material of cement clinker is a mixture of limestone, clay, iron slag (iron oxide) and the like.

As an example of a suitable aspect of the present invention, there may be mentioned one in which the firing furnace is a rotary kiln and the firing raw material is a cement clinker raw material. In this case, the ash content of the organic sludge is taken in as part of the cement clinker component. Since the ash content of organic sludge is composed of components that are almost the same as the raw material of cement clinker, the quality of cement clinker is not deteriorated.
The organic mixture and the firing raw material are charged into the furnace from the raw material inlet side of the firing furnace. At this time, the organic mixture may be added after being mixed with the firing raw material, or may be introduced alone via a supply path different from that of the firing raw material. The place where the organic mixture is charged is arbitrary as long as it is on the raw material inlet side of the firing furnace. For example, when the firing furnace is a rotary kiln, it is on the kiln bottom side of the rotary kiln.

An example of a firing furnace and its auxiliary equipment used in the present invention is shown in FIG.
In FIG. 1, the cement clinker raw material 1 is supplied to the upper portion of the suspension preheater 3 through the raw material supply pipe 2, then descends while being heated in the suspension preheater 3, and is guided to the calcining furnace 4. After being heated in the furnace burner, it is fired in the rotary kiln 6 via the raw material inlet side hood 5. The cement clinker 9 generated by the firing is discharged from the raw material outlet side (front side of the kiln) where the burner 7 is disposed, and is recovered after being cooled in the cooler 8 through which cooling air flows. The cement clinker 9 is pulverized after adding a small amount of gypsum to become cement. The exhaust gas 11 generated in the rotary kiln 6 rises in the suspension preheater 3, is then processed by an exhaust gas purification device (not shown) through the pipe 10, and is discharged into the atmosphere.

The fermented organic mixture 12 may be supplied via the raw material supply pipe 2 after being mixed with the raw material of the cement clinker 1 as indicated by the arrow A in FIG. As indicated by an arrow B, it may be supplied separately from the cement clinker raw material 1 via a pipe line 13 disposed so as to penetrate the raw material inlet side hood 5.
The organic sludge that has been fermented in the organic mixture is vaporized by combustion in the rotary kiln, and the combustible organic component becomes a gas such as carbon dioxide, and the ash, which is the combustion residue, constitutes the cement clinker. Become part of the material. In this way, the treatment of organic sludge is completed without generating residues or the like that need to be disposed of in landfills.
On the other hand, breathability improving materials such as wood chips in an organic mixture generate thermal energy by combustion in a rotary kiln and contribute to maintaining the furnace temperature, and ash as a combustion residue is a constituent material of cement clinker. Become part.

[Example 1]
The wood was crushed to obtain wood chips containing rod-shaped pieces of wood having a length in the range of 10 to 70 mm at a ratio exceeding 80% by mass.
Next, 100 parts by mass of sewage sludge, 15 parts by mass of wood waste, and an appropriate amount of inoculum used for the production of compost were mixed to obtain an organic mixture. In addition, the component composition of the sewage sludge was a water | moisture content of 73 mass% and solid content of 27 mass%. The moisture content of the wood waste was 10% by mass.
The obtained organic mixture was put in a 1.5 m ³ grid to form a deposit having a thickness of about 120 to 130 cm. 100 liters / minute of air was sent from a portion 20 cm below the deposit with a blower, and turned over once a day to advance the fermentation.

At each time point 4 days, 8 days, and 13 days after the formation of sediment (at the start of fermentation), the mass of water derived from sewage sludge (part by mass) and the residual rate from the start of fermentation (mass%), and The mass (part by mass) of the solid content derived from sewage sludge and the residual rate (% by mass) from the start of fermentation were measured.
Moreover, the residual rate (mass%) from the start of fermentation was computed regarding content of the water | moisture content contained in a deposit (organic mixture).
In addition, the mass of the wood waste remained unchanged over the fermentation treatment period.

The results are shown in Table 1. From Table 1, in 13 days after the start of fermentation, the mass of sludge decreased from 100 parts by mass to 41 parts by mass (59% by mass reduction rate), and the moisture derived from sludge decreased from 73 parts by mass to 27 parts by mass. It can be seen that the solid content derived from sludge was reduced from 27 parts by mass to 14 parts by mass, the moisture contained in the deposit (organic mixture) was reduced to 51% by mass, and the like.
The deposit after 13 days from the start of fermentation was charged into the rotary kiln through a pipe line provided in the raw material inlet side hood of the rotary kiln at a ratio of 2 parts by mass per 100 parts by mass of the cement clinker. As a result, the cement clinker could be manufactured under stable conditions without any significant fluctuations in the furnace temperature or the like. Moreover, there was no problem in the quality of the obtained cement clinker.

[Example 2]
The experiment was performed in the same manner as in Example 1 except that the wood waste used in Example 1 was crushed to 5 mm or less by a pulverizer.
The results are shown in Table 2. From Table 2, the mass of sludge decreased from 100 parts by mass to 63 parts by mass (mass reduction rate of 37%) and the moisture derived from sludge decreased from 73 parts by mass to 45 parts by mass in 13 days after the start of fermentation. It can be seen that the solid content derived from sludge has been reduced from 27 parts by mass to 18 parts by mass, the moisture contained in the deposit (organic mixture) has been reduced to 60% by mass, and the like.
The deposit after 13 days from the start of fermentation was charged into the rotary kiln through a pipe line provided in the raw material inlet side hood of the rotary kiln at a ratio of 2 parts by mass per 100 parts by mass of the cement clinker. As a result, the cement clinker could be manufactured under stable conditions without any significant fluctuations in the furnace temperature or the like. Moreover, there was no problem in the quality of the obtained cement clinker.

It is the schematic which shows an example of the rotary kiln used with the processing method of the organic sludge of this invention, and its attachment equipment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cement clinker raw material 2 Raw material supply path 3 Suspension preheater 4 Calciner 5 Raw material inlet side hood 6 Rotary kiln 7 Burner 8 Cooler 9 Cement clinker 10 Pipe line 11 Exhaust gas 12 Fermented organic mixture including sewage sludge 13 Pipe line

Claims (9)

A fermentation process in which organic sludge is fermented in an aerobic atmosphere to obtain organic sludge having a reduced mass;
Combusting step in which the organic sludge having a reduced mass is introduced into the furnace from the raw material inlet side of the baking furnace and burned together with the baking raw material;
A method for treating organic sludge, comprising: Mixing step of mixing organic sludge and air permeability improving material to obtain an organic mixture;
Fermenting the organic mixture in an aerobic atmosphere to obtain an organic mixture having a reduced mass; and
A combustion process in which the reduced organic mixture is introduced into the furnace from the raw material inlet side of the firing furnace and burned together with the fired raw material;
A method for treating organic sludge, comprising:   The method for treating organic sludge according to claim 2, wherein in the mixing step, the moisture content of the air permeability improving material is 50 mass% or less.   The above air permeability improving material is made of wood waste, fiber waste, rubber waste, waste paper, waste plastic, waste tire, waste PET bottle, plastic container packaging, polystyrene foam, rice straw, sawdust, rice husk, bark, perlite, vermiculite, The organic sludge treatment method according to claim 2 or 3, wherein the organic sludge is one or more selected from the group consisting of lightweight aggregates and waste ALC.   The processing method of the organic sludge of any one of Claims 2-4 including the process of crushing or grind | pulverizing the said air permeability improvement material as a pre-process of the said mixing process.   In the said mixing process, the compounding quantity of the said air permeability improvement material with respect to 100 mass parts of said organic sludge is 1-500 mass parts, The processing method of the organic sludge of any one of Claims 2-5.   The processing method of the organic sludge of any one of Claims 1-6 which performs a fermentation process in the said fermentation process until the mass of the said organic sludge reduces 10% or more with respect to the mass of the organic sludge before fermentation. .   The said organic sludge is a sewage sludge, The processing method of the organic sludge of any one of Claims 1-7. The method for treating organic sludge according to any one of claims 1 to 8, wherein the firing furnace is a rotary kiln, and the firing raw material is a cement clinker raw material.

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