JPH09192699A - Treatment of sludge and treated matter of sludge for cement starting material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use effectively and stably a sludge while reducing an energy cost and a usage of calcium oxide by mixing calcium oxides to the sludge containing more than specified amount water content to reduce the water content of the mixture to a specified range. SOLUTION: At the time of treating an org. sewerage sludge, the calcium oxides are mixed to the sludge having <=60% water content to control the water content of the mixture in >=15% and <=60%, preferably in >=20% and <=35%, and the mixture controlled the water content is heat treated to control the water content in <=10%. At the time of treating a treated matter of the sludge for a cement starting material, the calcium oxides are mixed to the sludge to control the water content of the mixture in >=15% and <=60%, preferably in >=20% and <=35%, and the obtained mixture is heat treated. The treated matter of the sludge treated in such a way is used as the cement starting material, that is, an org. matter in the treated matter is used effectively as a part of a fuel and an inorg. matter is used effectively as a part of the starting material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating sludge, particularly organic sewage sludge, and a treated sludge for cement raw material used as a part of a raw material for cement production.

[0002]

2. Description of the Related Art In recent years, the amount of sludge generated has been increasing with the expansion of sewer network. Conventionally, as a method of treating sewage sludge, it has been common to add incinerator fuel such as heavy oil to incinerate, and to dispose of incinerated ash in landfill.
It is becoming difficult to secure landfill sites for final disposal, and development of effective utilization methods for sewage treatment products is desired.

[0003] In such a situation, a technique of mixing sludge with quick lime and the like, dehydrating it by utilizing the heat of dehydration of quick lime, and then using it as a raw material for cement or a sintering raw material for iron making (Japanese Patent Laid-Open No. 3-98700) No. 3-207497). 10 in cement manufacturing process or iron manufacturing process
The raw materials are sintered in a furnace at a temperature of 00 ° C or higher, and when the sludge / lime mixture is put into these furnaces, the organic substances in the mixture are effectively used as a part of the fuel, and the inorganic substances are effectively used as a part of the raw material. Moreover, there is an advantage that existing cement manufacturing equipment and steelmaking equipment can be used as they are, and a large amount of sludge can be treated.

[0004]

However, in the above-mentioned treatment method, sludge is generally treated as sludge cake in the treatment plant through steps such as mechanical concentration and dewatering. The sludge cake mechanically dewatered in this way is used. Has a water content of 6 due to its nature.
The water content can be reduced only to 0 to 100%, usually to a water content of 70 to 90% (% indicates weight%, the same applies hereinafter). That is, in the dehydration step of separating water from the concentrated sewage treatment precipitate to form a cake, various dehydrators such as a vacuum dehydrator, a filter-press, a belt press, and a centrifugal dehydrator are used. It is very difficult to reduce the water content to 80% or less by merely mechanical dehydration. It is considered that this is mainly due to the large amount of internal water, organic water adhering to the surface, and capillary condensed water in the organic matter (about 90% or more of the solid content of the sewage sludge). It is said that the dehydration property is extremely deteriorated compared to the power cost.

On the other hand, it is known that the water forming the colloidal particles (water adhering to the surface) and the water existing inside the flocs of the activated sludge can improve the filtration performance by adding an appropriate dehydrating auxiliary. It is possible to reduce the water content by adding slaked lime, ferric chloride or the like as an inorganic auxiliary agent or an organic polymer coagulant to cause coagulation. However, polymer flocculants are expensive, and in the case of slaked lime, it is necessary to add a large amount, and since the amount of sludge is significantly increased, there is a tendency to avoid its use in recent years. There is a limit in treating the water content to less than 60%.

Therefore, in order to add quicklime to a high-moisture content sludge cake and to dry the sludge due to its heat of dehydration, a large amount of quicklime must be added, and the amount of produced sludge relative to the amount of sludge to be treated must be increased. Although the cement manufacturing equipment and steelmaking equipment described above can be used as they are, the sludge treatment efficiency and use efficiency are poor, and not only the cost of the quicklime to be added itself but also the transportation cost of the generated treated product. This also raises the overall processing cost and hinders the popularization of the technology.

For this reason, the Applicant has proposed that the moisture content of the incinerator exhaust gas, digestive gas, hot air drying using combustion exhaust gas, etc.
A sewage sludge was dried to a range of 0% by weight or less, preferably 20 to 50% by weight, and then mixed with quicklime, thereby proposing a sludge treatment method and a treatment apparatus with a reduced mixed amount of quicklime (special feature: Japanese Patent Application No. 7-136035). However, also in this case, drying in a high water content state was not always satisfactory in terms of thermal efficiency.

The present invention eliminates the above-mentioned drawbacks, greatly reduces the amount of quicklime used with a very small amount of energy cost, and reduces the weight of the produced product, thereby significantly reducing the running cost, Effective sludge,
It is an object of the present invention to provide a sludge treatment method and a sludge treated product for cement raw material that can be stably and effectively utilized.

[0009]

According to the sludge treatment method of the present invention to achieve the above object, the water content is 60%.
Mix the above sludge with quicklime and adjust the water content of the mixture to 1
5% or more and less than 60%, preferably 20% or more, 35
% (Claim 1), quicklime is mixed with sludge having a water content of 60% or more, and the water content of the mixture is 15% or more and less than 60%, preferably 20% or more and less than 35%. After that, the mixture is heat treated to reduce the water content to 10% or less (Claim 2), and the heat treatment is any one of drying, incineration and heat melting treatment (Claim 3). To do.

According to the treated sludge for cement raw material of the present invention, quicklime is mixed with the sludge and the water content of the mixture is 15% or more and less than 60%, preferably 20% or more and less than 35%. (Claim 4), in sludge,
Quicklime is mixed and the water content of the mixture is 15% or more, 60
%, Preferably 20% or more and less than 35%, and the mixture is heat-treated (Claim 5).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The sludge treated according to the present invention is mainly sludge generated in a sewage treatment plant.
Includes sludge generated from domestic wastewater and industrial wastewater treatment. As described above, these sludges are generally dehydrated in the treatment plant to a water content of 60 to 100%, usually 70 to 90%, and the present invention uses this sewage sludge.

In the present invention, quicklime is mixed with the dehydrated sludge having a water content of 60% or more. Quicklime is Ca
It contains O as a main component and takes in the water of the sewage sludge to form slaked limes. Specifically, quick lime, calcined dolomite, blast furnace slag, concrete pulverized fine powder and the like are included. The particle size of quicklime is 70 mm or less, preferably 3
It may be about 0 mm or less.

The mixing amount of quicklime depends on the water content of the sludge, but is 10% by weight or more and less than 50 parts at maximum (for example, the sludge having a water content of 80% is 100 parts by weight of the sludge.
0 parts to 40 parts of quick lime), and the water content of the mixture is 15% or more and less than 60%, preferably 20% or more,
Keep within the range of less than 35%. That is, a sludge treated product in which the amount of water is regulated by the soaking reaction between CaO and sludge moisture and the heat generated during the soaking is obtained. The sludge treated product whose water content is regulated in this range can be sufficiently used as a cement raw material to be described later, and is a treated product that is sterilized at high temperature by heat of soaking and has a high alkali content and is not deteriorated. If the water content of the sludge treatment product is higher than this range, there is no effect of adding quick lime, the treatment product may be spoiled, and the water reduction treatment in the next step becomes large. Further, if the residual water content of the sludge is less than this range, the amount of quick lime added becomes too large, and the quick lime cost increases more than the water reduction effect of the produced treated product, and the weight of the treated product increases, which is not preferable. .

In addition, in adding and mixing quicklime to the sewage sludge, the surface of the sewage sludge becomes hard when the surface is dried, and the water remains inside. Therefore, simply mixing with the quicklime removes the residual water and quicklime. The sum reaction is not enough.
Therefore, the dry sludge and the quick lime are preferably mixed together and pulverized to sufficiently bring the quick lime into contact with the residual water to form a granular material. For the pulverization, various pulverizers such as a ball mill, a vertical mill and a medium stirring mill can be used.

The sludge-treated product thus treated can be suitably used as a raw material for cement. That is, the organic matter in the treated material is effectively used as a part of the fuel, and the inorganic matter is effectively used as a part of the raw material, and the existing cement production equipment can be used as it is. As the cement, it is possible to use various kinds of cement raw materials such as portland cement, alumina cement, and allinite cement whose main raw material is municipal waste ash as a main raw material.

In the existing cement manufacturing facility,
We already have crushing equipment, mixing equipment, and drying equipment for cement raw materials such as limestone, clay, and iron source materials. Utilizing these equipment, the sludge treated material whose water content is regulated is used as the cement raw material. be able to. For example, in crushing equipment, the water content of sludge treatment product is 15% or more, 60%
If it is less than 20%, preferably less than 35%, it is not necessary for the treated material to adhere to the mill side wall or the grinding ball, and the existing limestone or clay in the drying equipment is not required. Energy cost similar to drying.

As described above, the sludge treated product has a water content of 15% or more and less than 60%, preferably 20% or more,
By restricting the content to less than 35% and applying it to the existing cement manufacturing equipment, it can be sufficiently treated as a sludge for cement raw material, but the mixture is further dried to obtain a water content of 10%. It is also possible to use a sludge treated product as a raw material for cement at a content of not more than%. In other words, the water content of the sludge mixture in which quicklime is mixed is already regulated, and the water content can be reduced to 10% or less with a small amount of heat. It can be transported to the cement factory in the form of powder. As a drying means, a hot air drying method using exhaust gas from an incinerator, a digestive gas, or a combustion exhaust gas, a temperature of steam or the like of 200
Drying using a heating medium at about ℃ or less is preferably used.

In many sewage treatment plants, incinerators and heating / melting equipment for dehydrated sludge are already owned or are planned to be installed. It is also possible to treat a sludge mixture in which the substances are mixed and the water content is regulated. In the incineration and heat melting treatment of sludge mixture, SOx and NOx are less generated in the presence of Ca component in the mixture and can be effectively treated. The obtained incinerated ash or molten ash (slag ) Can be transported to a cement factory in a further reduced form, and can be suitably used as a cement raw material. Especially in the melting treatment, after heating and melting the sludge mixture, the glassy treated product obtained by quenching is of course utilized as the cement raw material, and already has the mixing material characteristics of blast furnace slag, It can be used as a cement admixture or a mixed cement.

[0019]

【Example】

(Example 1) 100 parts by weight of dehydrated sludge having a water content of 80% was mixed with 12 parts by weight of quick lime and 36 parts by weight (addition ratios of 15% and 45% with respect to the amount of water) with a Henschel mixer to prepare a cement raw material of the present invention. Sludge treatment product A: 76 parts by weight (water content 58%) and B: 85 parts by weight (water content 34%)
%) Was obtained. Next, 100 parts by weight of the cement compounding raw material was added to 50 parts by weight of each of the obtained treated products A and B, and the mixture was ground for 20 minutes with a ball mill. Upon pulverization, the treated products A and B were sufficiently practical because there was little adhesion of the treated products to the mill side wall or ball. As a comparative example, the water content is 80%.
5.6 parts by weight of quicklime and 8 parts by weight of dehydrated sludge of
8 parts by weight (addition ratio to water content 7%, and 110
%), And the mixture C: 94 parts by weight (water content 73
%) And D: 120 parts by weight (water content 10%), 100 parts by weight of the cement compounding raw material was added to 50 parts by weight of each of the mixtures C and D, and the mixture was ground in the same manner. Mixture C is
The amount adhering to the side wall of the mill and the ball was as much as 32 parts by weight, and a practical crushing operation could not be performed. In addition, although the mixture D was less attached to the mill, the amount of quick lime added was too large, the quick lime cost increased more than the moisture reduction effect, and the weight of the treated product increased.

(Example 2) Next, 15 parts by weight of each of the mixtures A and B obtained in Example 1 were mixed with 85 parts by weight of a cement compounding raw material, and the mixture was fired in an electric furnace at 1450 ° C to obtain a cement clinker. Got Gypsum was added to this clinker and mixed and pulverized to obtain a cement having a brain specific surface area of 3000 cm ² / g. A cement test was carried out in accordance with JIS R 5201. It was as good as that.

Example 3 Mixtures A and C obtained in Example 1 were heat treated and then melted and solidified. While the organic components of the mixture C are decomposed at the decomposition point of 550 ° C., the mixture A is mixed.
The decomposition point of was reduced by 300 ° C and 250 ° C. Then, in the melting step of the mixture A, vitrification at 1600 ° C is usually 1
It was possible to reduce the temperature to 450 ° C., and the crushed product of the molten glass exhibited the characteristics of a cement mixture similar to that of blast furnace slag (98 days old strength ratio 98%).

[0022]

According to the present invention, the following excellent effects can be obtained. (1) Mixing quicklime and the like into sludge to produce a sludge treated product having a regulated water content, which enables treatment that does not interfere with the cement resource recycling process with an extremely small energy cost. (2) By reducing the amount of quicklime and reducing the weight of the processed product, it is possible to significantly reduce the cost. (3) Incinerated ash, molten slag, etc. can be effectively recycled as cement resources, and can be recycled in various fields, and sludge can be used effectively and stably.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yu Shirasaka 2-4 Daisaku, Sakura City, Chiba Prefecture Chichibu Onoda Central Research Institute

Claims (5)

[Claims] 1. Sludge having a water content of 60% or more is mixed with quicklime, and the water content of the mixture is 15% or more and less than 60%, preferably 20% or more and less than 35%. Sludge treatment method. 2. A sludge having a water content of 60% or more is mixed with quicklime, and the water content of the mixture is adjusted to 15% or more and less than 60%, preferably 20% or more and less than 35%, and then the mixture is heated. A method for treating sludge, which comprises treating the treated water to a water content of 10% or less. 3. The method for treating sludge according to claim 2, wherein the heat treatment is any one of drying, incineration, and heat melting treatment. 4. A sludge treated product for cement raw material, characterized in that quick limes are mixed with sludge, and the water content of the mixture is 15% or more and less than 60%, preferably 20% or more and less than 35%. . 5. The sludge is mixed with quicklime, the water content of the mixture is adjusted to 15% or more and less than 60%, preferably 20% or more and less than 35%, and the mixture is heat-treated. Sludge treatment product for cement raw material.