JPH07239118A - Treating method for sludge - Google Patents

Abstract

PURPOSE:To reduce nitrogen oxide in exhaust gas by treating sludge to sludge dry powder in which generation of offensive odor is suppressed and incinerating it by a cement burning furnace. CONSTITUTION:The method for treating sludge comprises the steps of adding quick lime of 300-1000wt.% by solid content of dehydrated sludge to the dehydrated sludge containing 40-85% of water content obtained by dehydrating organic waste water, mixing, agitating and ripening it to sludge dry powder containing 10% or less of water content, supplying it to a cement burning furnace, burning it, and passing gas generated in the burning step through a high temperature part of 500 deg.C or higher of the furnace, thereby reducing nitrogen oxide in exhaust gas.

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 by incinerating it in a cement burning furnace, and more particularly to a method for treating sludge while reducing nitrogen oxides generated during cement burning.

[0002]

2. Description of the Related Art Disposal of sludge has conventionally been carried out in the form of dehydrated sludge, dried sludge, composting, etc., in the form of liquid sludge, dumped into the ocean, returned to farmland, and landfilled. However, when sludge is disposed in these forms, it emits offensive odor gas and, at present, it is difficult to secure a disposal site. For this reason, the method of incineration and reducing the volume without producing odor is gradually becoming the main treatment method.
Even in such cases, the generation of NO _{X in} the combustion exhaust gas, the use of a large amount of auxiliary fuel, the maintenance of the incineration facility, and the disposal of incineration ash have become new problems.

Therefore, the dehydrated sludge is transported to a cement factory, where quick lime is mixed with the dehydrated sludge to be dried, and the gas generated at this time is supplied to a firing furnace to be used as a denitration agent, and the dried sludge is also used. Has been proposed to be supplied to a cement firing furnace (JP-A-3-98700).
However, this method requires that the dewatered sludge generated at the sewage treatment plant be supplied to the cement factory as it is by freight vehicle, which causes problems such as bad odor during transportation, sludge deterioration due to fermentation, and gas / leakage water generation. There was a difficult situation for practical application.

[0004]

DISCLOSURE OF THE INVENTION The present invention intends to reduce nitrogen oxides in exhaust gas by making sludge dry powder in which generation of odor is suppressed and incinerating it in a cement burning furnace. Is.

[0005]

The present invention relates to dehydrated sludge having a water content of 40 to 85% obtained by treating and dehydrating an organic wastewater, and adding quicklime to the dehydrated sludge in a solid content weight ratio of 300 to 100.
Add 0%, mix and stir to aged to obtain a sludge dry powder with a water content of 10% or less, supply this to a cement firing furnace and burn it, and generate gas during the combustion process at a high temperature of 500 ° C or higher in the firing furnace. Method for treating sludge, characterized by reducing nitrogen oxides in the exhaust gas (claim 1), and supplying the sludge dry powder to a high temperature part of a cement calcination furnace at a temperature of 500 ° C or higher. The method for treating sludge according to claim 1 (claim 2) and the dried sludge powder, wherein brown coal is further dried and finely pulverized to form brown coal (A).
The brown coal processing powder which mixed the brown coal (B) which carried out the dry distillation of brown coal at 900 degreeC or less and 0-90 weight part is added to 10-100 weight part, and 1-10% is added, The 1 or 2 characterized by the above-mentioned. It is the sludge treatment method (claim 3). These inventions will be further described below.

The dewatered sludge used in the present invention is a treatment residue of organic wastewater discharged from factories in addition to municipal wastewater,
The water content is 40 to 85%. The water content cannot be reduced to less than 40% by conventional mechanical dehydration, and drying is required to reduce the water content to less than this, and dehydration treatment is expensive. A large amount of quick lime is required to achieve the necessary drying even after aging.

Next, the solid content weight ratio of the dehydrated sludge was 3%.
Add 0 to 1000% of quicklime and mix and stir to ripen.
As a result, quicklime becomes slaked lime, and the heat of the water removes the water content of the sludge to obtain a dried sludge powder having a water content of 10% or less. The quicklime used here has CaO of 70
% Or more, preferably soft-calcined quicklime is used. If the amount used is less than 300% with respect to the solid content of dehydrated sludge, the required drying cannot be performed, and the malodor will be insufficiently removed.
If the quick lime is added in excess of 1000%, the quick lime becomes excessive, causing an unnecessary increase in cost.

The water content of sludge is reduced to 10% or less by the above treatment. If the water content exceeds 10%, a foul odor may be generated, and the sludge may become sticky, resulting in trouble in handling. A more preferable water content is 5%.

The dried sludge dry powder having a water content of 10% or less is then incinerated. In the present invention, this is carried out in a cement firing furnace, and the gas generated at that time is 500 ° C. or more in the firing furnace. Try to pass through the high temperature part. As a result, the gas generated here reacts with the nitrogen oxides in the gas generated during cement firing, and contributes to the reduction of nitrogen oxides. The reaction here requires that the gas temperature be 500 ° C. or higher. The temperature is preferably 550 ° C or higher, more preferably 600 ° C or higher. Therefore, it is preferable to supply the dried sludge powder from the fuel supply section of the kiln calcination furnace, which is a high temperature section of the cement calcination furnace of at least 500 ° C (claim 2).

The invention of claim 3 relates to the sludge dry powder,
Further, lignite (A) 10 to 100 obtained by drying and finely pulverizing lignite
1 to 1 of a brown coal processed powder in which 0 to 90 parts by weight of brown coal (B) obtained by dry-distilling brown coal at 900 ° C. or less is mixed in parts by weight.
0% is added. This is because there is still a small amount of ammonia odor and other bad odors remaining in the sludge dry powder, so it is intended to further improve the working environment and use this odor component to reduce nitrogen oxides in the cement burning exhaust gas,
The above-mentioned brown coal processing powder is added to this to prevent the generation of odor.

The lignite (A) used here is 100 lignite.
Drying at ~ 200 ℃ pressure 500 ~ 1000kg /
It is preferable to apply a pressure of cm ² and finely pulverize. It is preferable that the brown coal is dried at about 80 ° C. using 100 to 200 heating steam. Further, by pressurizing the dried brown coal with the above-mentioned pressure, the pores of the brown coal become finer and the adsorption of basic malodorous gases such as ammonia and trimethylamine becomes more excellent, and the handling is also good. become.

The brown coal (B) is obtained by dry distillation of the brown coal obtained above at 600 to 900 ° C. In this treated brown coal (B), oxygen in the molecule is CO ₂ , CO, H ₂ O.
As degassed, the surface comes to exhibit a reduced state. Therefore, excellent deodorization can be expected for acidic malodorous gases such as hydrogen sulfide and methyl mercaptan.

In the present invention, the above lignite (A) 10 to 10 is used.
A brown coal processed powder in which 0 to 90 parts by weight of brown coal (B) is mixed is used. That is, although brown coal (A) may be used alone,
A mixture of 10 to 100 parts by weight of brown coal (A) and less than 90 parts by weight of brown coal (B) may be used.

Such brown coal processing powder is added to the sludge dry powder in an amount of 1 to 10%, and the addition amount of the brown coal processing powder is 1%.
If it is less than 10%, it is difficult to recognize the effect of addition, and it is not necessary to add more than 10%.

Since the odor of the sludge dry powder before the addition of brown coal has already been significantly reduced, almost all the residual ammonia odor is removed by adding brown coal (A) alone to this, but further brown coal is added. When (B) is used together, not only the ammonia odor but also the sulfide odor is removed, and it can be said that the deodorization of the sludge is almost fully achieved.

The blending ratio of lignite (A) and lignite (B) was set to 0 to 90 parts by weight with respect to 100 parts by weight of the former because the odor of sulfide is weak and the removal thereof is not necessary in many cases. In addition, even if this is removed, less than 90 parts by weight of brown coal (B) is sufficient for 100 parts by weight of brown coal (A). The sludge dry powder to which the above-mentioned brown coal processed powder is added is subjected to combustion treatment in the cement burning furnace in the same manner as described above.

[0017]

The present invention uses the water content of dehydrated sludge to dry the dehydrated sludge by the heat generated when reacting this with quick lime to obtain a sludge dry powder, which improves the handling property and at the same time significantly reduces the malodor. In addition, the brown coal processing powder is added to this to prevent the bad odor more reliably, and it is supplied to the cement firing furnace for incineration and the nitrogen oxide in the exhaust gas is removed by the gas generated at that time. It is what The present invention will be further described below with reference to examples.

[0018]

【Example】

(Examples 1 to 4) Two kinds of dehydrated sludge having a water content of 76.5% were obtained by dehydrating the sewage treatment concentrated sludge into various kinds using a filtration tester.
Two kinds of dehydrated sludge having a water content of 85.5% were prepared. These two
The seed dewatered sludge was divided into two and made 1 kg each. To this, quick lime JIS special product was added at a ratio shown in Table 1, and rapidly stirred for 5 minutes with an experimental stirrer, followed by slow stirring for 1 hour, respectively, and mixed and aged. As a result, a sludge dry powder having a water content as shown in Table 1 was obtained. The odor of this dry sludge powder was small, and when it was transported or incinerated by the usual method, it did not cause any troubles in the working environment, but some odor still remained.

50 g of each 200 g of these sludge dry powders
The mixture was placed in a 0 cc poly bottle, the lid was closed, and the bottle was shaken for 2 minutes to mix. After 10 minutes, the lid was opened, the gas was sampled, and the concentrations of ammonia and methyl disulfide were measured by gas chromatography. The results are shown in Table 1.

(Comparative Examples 1 and 2) The weight ratio of quicklime to dehydrated sludge was outside the upper and lower limits defined by the present invention, and other conditions were the same as those of Examples 1 to 4. Comparative Example 1 had tackiness and was not suitable for pressure feeding.

[0021]

[Table 1]

(Examples 5 to 7) Lignite (A) and brown coal (B) were added to the dried sludge powders of Examples 1 to 3 in a weight ratio of 10:
0% (Example 5), 6: 4 (Example 6), and 1: 9 (Example 7) were mixed, and 1% of the processed brown coal powder was added. Ammonia and methyl disulfide of this product were measured in the same manner as in Example 1. The results are shown in Table 2.

[0023]

[Table 2]

(Embodiment 8) Sewage was dehydrated and water content was 8
9 kg of quicklime JIS special product was added to 10 kg of 0.5% dehydrated sludge, which was rapidly stirred for 5 minutes by a horizontal axis stirrer, and then slowly stirred for 1 hour for mixed aging. The sludge dry powder obtained here was 16 kg, and the water content was 8.3%,
The total nitrogen content was 0.44% and the ammoniacal nitrogen content was 0.02%.

The dried sludge powder 200 was put into a 500 cc poly bottle and the lid was closed, and the mixture was mixed for 2 minutes. After 10 minutes, the lid was opened and the ammonia concentration was measured with a detector tube. As a result, 28 ppm was detected.

Next, 200 g of this sludge dry powder was divided into four 500 cc polybottles, and various commercially available deodorizing agents and the same brown coal-processed powder used in Example 5 were added at the ratio shown in Table 3. Mixed. The ammonia concentration of this product was measured and is shown in Table 3. It should be noted that when 3% of the brown coal-processed powder shown in Table 3 was added and mixed, each was placed in a poly bottle and the ammonia concentration was measured after 3 days and 7 days, and all were zero.

[0027]

[Table 3]

(Examples 9 to 10) Quicklime JIS special product was added to 100 kg of dehydration treatment obtained by dehydrating sewage to obtain a water content of 85.5%, total nitrogen of 5.6%, and ammoniacal nitrogen of 1.5%. 1
After adding 00 kg and stirring rapidly with a pug mill for 5 minutes, 1
The mixture was aged for slow mixing for a period of time. The sludge dry powder thus obtained weighed 165 kg and had a water content of 5.
6%, total nitrogen 0.44%, ammoniacal nitrogen 0.0
It was 2%.

Thereafter, this sludge dry powder was divided into 80 kg each for 2 minutes, one of them was left as it was, and the other 80 kg was mixed with 8 kg of the same brown coal used in Example 5 and subjected to a suitability test as a denitration agent. It was carried out using a cement firing miniplant having a raw material preheating device with a 4-stage cyclone calcining furnace.

In the experiment, the conventional operation in which no sludge was added was used as Comparative Example 3, and about 10 in the lower part of the cyclone calcination furnace was used.
The sludge dry powder was supplied to the site of 00 ° C. at a ratio of 4.5% with respect to the cement raw material and operated (Example 9). Further, the powder obtained by adding and mixing the brown coal dry powder used in Example 5 to the sludge dry powder was added to the cyclone calcination furnace at about 10
The sludge dry powder was supplied to the site of 00 ° C. at a ratio of 4.5% with respect to the cement raw material and operated (Example 9). The nitrogen oxides in the exhaust gas during operation were measured and are shown in Table 4.

[0031]

[Table 4]

(Example 10) In a demonstration plant (capacity, dehydrated sludge 200 kg / hr) consisting of a mixing stirring tank and an aging tank,
A dehydrated sludge having a water content of 85.5% and lime were mixed and aged to produce 54 t of sludge dry powder. The ratio of the dry sludge powder in the lime raw material was set to 2.3%, and 40% of kiln kiln
About 1000 at the bottom of 4-t cyclone calciner at 00t / day
When supplied to the site of ℃, ammonia, aldehyde,
Hydrogen cyanide was not detected at all as in the conventional method, but at the same time, the concentration of nitrogen oxides in the exhaust gas was reduced by up to 20%.

When the above sludge dry powder was supplied to the uppermost cyclone of the cement burning furnace having the raw material preheating device at the lower part of the four-stage cyclone calcining furnace, ammonia and aldehyde were discharged in the EP outlet exhaust and the main stack exhaust. However, the concentration of hydrogen cyanide tended to increase slightly.

[0034]

INDUSTRIAL APPLICABILITY According to the present invention, since dehydrated sludge is made into a dry powder by heat generated by digestion of quick lime, a dry powder having a water content of 10% or less can be obtained by a simple method, and its handling is remarkably improved. In addition, it has become possible to easily burn this in a cement firing furnace and use the residue as a cement raw material.

By burning this in a cement burning furnace, nitrogen oxides in exhaust gas can be reduced by the organic nitrogen and ammonia contained in the sludge dry powder, which is a secondary effect. Also found that you can expect. Furthermore, by adding a small amount of brown coal processing powder to the sludge dry powder, an ammonia odor,
The smell of sulfide can now be reliably prevented.

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Claims (3)

[Claims] 1. A dehydrated sludge having a water content of 40 to 85% obtained by treating and dehydrating an organic wastewater is added with quick lime in an amount of 300 to 1000% by weight of the solid content of the dehydrated sludge, and the mixture is agitated and aged to obtain a water content. Dry sludge powder of 10% or less was supplied to the cement burning furnace and burned, and the gas generated in the burning process was passed through the high temperature section of 500 ° C or higher in the burning furnace, whereby nitrogen oxidation in the exhaust gas was carried out. A method for treating sludge, which is characterized by reducing waste. 2. The dried sludge powder is mixed in a cement baking furnace at 50
The liquid is supplied to a high temperature part of 0 ° C. or higher.
The described sludge treatment method. 3. A brown coal (B) obtained by dry-distilling the brown coal at 900 ° C. or lower to 0 to 90 parts by weight of the brown coal (A) obtained by further drying and finely grinding the brown coal with respect to the dry sludge powder.
The method for treating sludge according to claim 1 or 2, wherein 1 to 10% of the brown coal processed powder mixed in parts by weight is added.