JPH08299997A - Treatment of sludge and device therefor - Google Patents

Abstract

PURPOSE: To decrease the consumption of quicklime and the weight of the treatment product to reduce the running cost and to effectively and stably utilize sludge by mixing quicklime in the sludge with the water content previously specified. CONSTITUTION: A sludge 1 is the cake dehydrated in a sewerage disposal plant, etc., and the sludge 1 is introduced into a drying means 2 to obtain a dried sludge 6 contg. <=60wt.% water. The dried sludge 6 is mixed in a mixing means 7 with 100 to 200wt.% quicklime 8, based on the water content of the sludge. The quicklime 8 is slaked by the water remaining in the dried sludge 6, and the sludge is further dried by the heat generated in the slaking to obtain a mixed sludge 9. The mixed sludge 9 is crushed by a means 10 to slake the quicklime 8 by the internal water, and a dry crushed sludge 11 is obtained. The sludge 11 is classified by a means 12, the coarse powder is returned 13 to the crushing means 10 and again crushed, and the fine powder is recovered as a treated sludge 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for treating sludge, particularly organic sewage sludge.

[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). 100 in cement manufacturing process or steel manufacturing process
The raw materials are sintered in a furnace at 0 ° 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 7 due to its nature.
The water content can be reduced only to about 0 to 90% by weight. Therefore, in order to add quicklime to a high-moisture content sludge cake and to dry the sludge due to its heat of slaking, a large amount of quicklime has to be added, and the weight of the produced treated product is greater than the treated sludge amount. Although the cement production 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 quick lime itself to be added but also the transportation cost of the produced product increases. However, the overall processing cost becomes high, which is a cause of hindering the spread of the technology.

The present invention eliminates the above-mentioned drawbacks, greatly reduces the amount of quicklime used, and also reduces the weight of the product to be treated, thereby significantly reducing the running cost and effectively and stably sludge. It is an object of the present invention to provide a sludge treatment method and a treatment device that can be effectively used for the above.

[0006]

In order to achieve the above object, according to the sludge treatment method of the present invention, quicklime is mixed with sludge having a water content of 60% by weight or less (claim 1). ), Mixing sludge and quicklime while crushing (claim 2), and drying sludge in advance so that the water content of sludge is 60% by weight or less, preferably 20 to 50% by weight (claim 3). , Quicklime is 10 against the water content of sludge
According to the sludge treatment apparatus of the present invention, a mixing means for preliminarily setting the water content of the sludge to 60% by weight or less, dry sludge and quick lime is used. And a sludge / lime mixture crushing unit (Claim 5) and a crushed product classification unit (Claim 6). The present invention will be described in detail below.

The sludge treated by the present invention is mainly sludge generated in a sewage treatment plant, but in addition to this, sludge generated by human waste, domestic wastewater, industrial wastewater treatment and the like is included. These sludges generally have a water content of 70-90% at the treatment plant.
It has been dehydrated to some extent, and the present invention uses this sewage sludge.

The sewage sludge is dried to a water content of 60% by weight or less, preferably 20 to 50% by weight. Drying is preferably performed using hot air drying using exhaust gas from an incinerator, digestion gas, combustion exhaust gas, or drying using a heating medium such as steam. A heating medium with a temperature of about 200 ° C or less is used and the residence time in the dryer is reduced. It is desirable that the time is about one hour or less.
As a drying method, either an indirect steam heating and stirring type or a direct hot air rotating type can be applied. If the water content of the dried sludge exceeds 60% by weight, a large amount of quicklime is required to dry the sludge due to the heat of quenching the quicklime, which will be described later,
Also, to dry until the water content falls below 20% by weight,
Since it is necessary to prolong the residence time in the dryer or to dry at a higher temperature, it is uneconomical because it is more economical than reducing the amount of quicklime to be used.

Next, quicklimes are added to and mixed with the dried sewage sludge. The quicklimes are those which have CaO as a main component and take in the water of sewage sludge to become slaked limes, and specifically include quicklime, calcined dolomite, blast furnace slag and the like. The particle size of quicklime is 70 mm or less, preferably about 30 mm or less. By mixing quicklime with 100 to 200% by weight of the water content in the dried sludge, the water content is 15% by weight by drying due to the hydration reaction between CaO and the water content of the sludge and the heat generated during the hydration.
Below, preferably 10% by weight or less of a treated product is obtained. When the amount of quick lime added is less than this range, the residual water content of the sludge is large, a bad odor remains, and there is a possibility of spoilage, which is not preferable. Further, if the amount of quick lime added is too large, the cost will increase including the effect of reducing the weight of the produced product, which is not preferable.

When adding quick limes to the sewage sludge, the surface of the pre-dried sewage sludge is dry and hard, and the moisture remains inside. Insufficient reaction of residual water with quicklime. 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.

[0011]

[Function] The addition rate of quick lime is drastically reduced by treating the sludge with the hydration reaction between quick lime and the water in the sludge which has been dried in advance to reduce the water content and the heat generated during the hydration.
As a result, the amount of water in the treated sludge produced can be significantly reduced, and the granular material with good fluidity and excellent handling can be obtained, and at the same time, the running cost can be significantly reduced.

[0012]

EXAMPLE In FIG. 1, a sludge 1 is a dehydrated cake that has been dehydrated to a water content of about 70 to 90% at a sewage treatment plant or the like.
Up to and including 20% to 50% by weight of dried sludge 6
Get. As an example of the drying means 2, an indirect steam heating and stirring type is used, and the heating medium, for example, the steam 3 indirectly heats the sludge 1. Reference numeral 4 denotes discharge of a drain formed by heat exchange of the heat medium 3 and sludge 1 and condensation, and reference numeral 5 denotes exhaust gas mainly composed of water vapor generated when the sludge 1 is heated. Etc. and is released to the atmosphere. As the drying means 2, various types such as an indirect steam heating and stirring type and a direct hot air rotating type can be used.

The dry sludge 6 is mixed in a mixing means 7 such as a Henschel mixer in an amount of 100 to 200% by weight based on the water content of the sludge.
By mixing with the quick lime 8 of the above, the quick lime 8 causes a soaking reaction with the water remaining in the dried sludge 6. Although the mixed sludge 9 can be further dried by the heat generated at this time, the mixed sludge 9 is dried by the drying means 2 even though the water content is lowered by the reaction with the drying means 2 and the quick lime 8. The surface of the sludge 6 may be hard,
Water still remains inside.

Therefore, preferably, the mixed sludge 7 is crushed by the crushing means 1
It is crushed with 0 and more preferably with a classifying means 12. That is, the mixed sludge 9 is crushed by the crushing means 10, and the water inside and the quick lime 8 sufficiently undergo a soaking reaction to be further dried to obtain the crushed sludge 11. The crushed sludge 11 is classified into coarse powder and fine powder by the classification means 12, and the coarse powder is returned powder 1
3 is pulverized again by the pulverizing means 10 and fine powder is collected as treated sludge 14.

The treated sludge 14 thus treated is a granular material which has a significantly reduced addition rate of quick lime, is sufficiently dried and has good fluidity, and is excellent in handling. It is effectively used as a part of raw materials.

Next, a conventional example (comparative example 1) in which quick lime is added to the sludge cake having a high water content without drying it
According to the present invention, the sludge cake according to the present invention is dried and quicklime is added and mixed (Example 1), and the sludge cake is dried and quicklime is added and mixed, and pulverized (Example 2). Table 1 shows an example of sludge treatment. Table 1
As is clear from the above, according to the present invention, the amount of added quick lime can be significantly reduced, and the effect of reducing the weight of the produced sludge mixture is remarkable, and the sludge treatment can be effectively performed.

[0017]

[Table 1]

[0018]

According to the present invention, the following excellent effects are obtained. (1) By drying sludge with a heating medium before mixing it with quick lime, the amount of water to be dried with quick lime is significantly reduced, and the amount of quick lime used can be greatly reduced, and the treatment cost is also significantly reduced. To do. (2) Since the mixing amount of quick lime can be reduced, the volume of the mixer can be reduced and the power required for stirring can be reduced. (3) Since the amount of slaked lime in the generated treated sludge is small and the content ratio of the organic component is high, the calorific value is increased and the value as a fuel is increased. (4) Since the amount of quicklime used is small and the amount of sludge produced is small, it is possible to reduce the costs required for transportation and storage costs.

[Brief description of drawings]

FIG. 1 is a flow chart showing sludge treatment of the present invention.

[Explanation of symbols]

 1 Sludge 2 Drying means 3 Steam 4 Drain 5 Exhaust gas 6 Drying sludge 7 Mixing means 8 Quicklime 9 Mixed sludge 10 Grinding means 11 Grinding sludge 12 Classification means 13 Return powder 14 Treated sludge

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenji Nozaki, Kenji Nozaki 2-4, Daisaku, Sakura-shi, Chiba Chichibu Onoda Central Research Institute Co., Ltd. (72) Takao Tanozaki 2-4-2, Daisaku, Sakura-shi, Chiba No. Chichibu Onoda Central Research Institute (72) Inventor Keiichi Usura 2-14-1, Nishishimbashi, Minato-ku, Tokyo Chichibu Onoda Co., Ltd.

Claims (6)

[Claims] 1. A method for treating sludge, which comprises mixing quicklime with sludge having a water content of 60% by weight or less. 2. The method for treating sludge according to claim 1, wherein sludge and quicklime are mixed while being crushed. 3. The sludge is dried in advance so that the water content of the sludge is 60%.
The sludge treatment method according to claim 1 or 2, wherein the content is not more than 20% by weight, preferably 20 to 50% by weight. 4. A quick lime content of 100 relative to the water content of sludge.
% To 200% by weight are mixed.
The method for treating sludge according to any one of 1. 5. An apparatus for treating sludge, comprising: a drying means for preliminarily setting the water content of sludge to 60% by weight or less; a mixing means for mixing dried sludge and quick lime; and a crushing means for sludge / lime mixture. 6. The sludge treatment device according to claim 5, further comprising a crushed material classification means.