JPS6342799A - Sludge treatment by fine coke powder - Google Patents

Abstract

PURPOSE:To recover dehydrated sludge cake having a low moisture content and high calorific value by adding and mixing fine coke powder to and with excessive sludge, etc., generated in the treatment stage, etc., of factory waste water, etc., and resting the water, then separating and dehydrating the thickened sludge. CONSTITUTION:The fine coke powder 2 is mixed at 5-30wt% with the sludge 1 discharged at the time of the treatment of factory waste water or other waste water and is agitated in a mixer 3. The mixture 4 composed thereof is rested in a resting and sepn. tank 5 and is separated to supernatant liquid 9 and the thickened sludge 6. The thickened sludge 6 is dehydrated by a dehydrator 7. As a result, the dehydrated cake 8 having the low moisture content and high calorific value is recovered and the effective utilization of the by-product of iron works is possible.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention provides a method for treating wastewater that is a source of environmental pollution such as factory wastewater.
The present invention relates to a sludge treatment method in which coke fine powder is added to excess sludge etc. generated as a result of this, and the mixture is concentrated and separated.

(Prior art) Generally, the solid content of surplus sludge discharged from an aerated activated sludge treatment facility for factory wastewater, etc. is between 5,000 and 20,000.
00 PI)m.

Conventionally, this type of surplus sludge treatment involves adding a polymer flocculant or iron chloride to the sludge at a ratio of 5 to 30% by weight based on the solid content of the sludge, and then dewatering this using various dewatering devices. ,
A method was used to collect the dehydrated sludge cake.

However, since the solid content in sludge exists in an extremely close affinity with water as a dispersion medium, the above sludge concentration/separation method does not allow for the close relationship between the solid content in sludge and water. Difficult to destroy.

That is, in the above method, since the water content in the sludge is very high and the dewatering property is poor, the water content of the dehydrated sludge cake can only be expected to be about 80%.

Therefore, for example, if sludge is put into an incinerator as it is and incinerated, it is extremely uneconomical due to the large amount of heat required, and since the sludge is semi-fluid, the handling and other aspects of the incineration process are There are also many problems.

As a countermeasure for this, for excess sludge or chain line sludge generated accompanying sewage and other sewage treatment, pulverized coal or A method of mixing, agglomerating and dewatering crushed peat (Japanese Patent Publication No. 13957/1989), in which the fine particles with a particle size of 100 mesh or less are 30 to 50% by weight m1, and the coarse particles larger than the above particle size are 70 to 50% by weight. Particle size adjustment, which has two peaks in the particle size distribution curve with respect to the fine powder and coarse particles, and contains particles with a particle size of 16 to 150 mW% less than 60 mW%. A method in which pulverized coal or lignite powder is mixed and stirred at a ratio of 2 to 10% by weight, separated and dehydrated (Tokuko Kokō 5
Proposals such as 1-3130 Sokka) have also been proposed.

(Problems to be Solved by the Invention) However, the moisture content of the dehydrated sludge cake collected by the above-described surplus sludge treatment method is about 75%, which is not satisfactory.

(Means for Solving the Problems) The present invention, as a result of exploratory research on coagulation and sedimentation agents, uses coke fine powder as a coagulation and sedimentation agent when treating the above-mentioned surplus sludge. Sedimentation occurs quickly, and the resulting chain-line sludge has excellent filterability and can be dehydrated to an extremely low moisture content of 45 to 60% by weight, and the collected dehydrated sludge cake The lower calorific value (true heat generation i) of is 3,000 kca
t/kl? It has also been found that adding and mixing fine coke powder to excess sludge has a deodorizing effect on excess sludge.

Further, although the present invention is applicable not only to surplus sludge but also to activated sludge, the following explanation will be made regarding surplus sludge.

That is, the present invention mixes and stirs coke fine powder with a particle size containing 50% by weight or more of particles with a particle size of 0.125 or less into surplus sludge generated in conjunction with the treatment of factory wastewater and other sewage. This is a method for concentrating and separating solid content of sludge, which comprises: then allowing the above-mentioned mixture to stand still, separating it into a supernatant liquid and a coke-containing #condensed sludge, and dewatering the separated coke-containing chain-line sludge. If the particle size of the fine coke powder exceeds Q, column 125 or is less than 50 by weight, the 'a condensation separation effect will be reduced, so the above range is suitable.

The present invention is useful for treating various types of sludge, such as surplus sludge or activated sludge discharged during sludge treatment of industrial wastewater in steel works, urban wastewater, and other general industrial wastewater.

Excess sludge discharged from these sewage treatment plants generally has a moisture content of 90 to 99%, with the remainder consisting of solids (ash and combustibles).

As mentioned above, these solid contents exist in a stable sol state that is very closely compatible with water as a dispersion medium. As a result, after separating and dewatering this excess sludge using a known method, the moisture content of the dehydrated sludge cake was 70 to 90 cm, and the lower calorific value was -200 to 1,000 kcat/kl? It is.

According to the present invention, coke fine powder with poor porosity (Table 1)
By mixing this into excess sludge, the solid content present in a stable dispersed state in the sludge can be quickly and effectively separated.

Table 1 As the fine coke powder for the flocculant, fine coke powder (CDQ powder) generated as a by-product from the coke dry extinguishing equipment of the coke production equipment in the steel works can be effectively used.

Furthermore, as shown in Table 1, fine coke powder has a higher porosity than coal powder, and therefore has excellent ability to coagulate solids in sludge.

The amount of fine coke that should be mixed into surplus sludge varies depending on the amount of solid content in the sludge, and also varies depending on the type of solid-liquid separation method such as centrifugal dewatering and sedimentation. Further, the amount of coke fine powder to be added can be determined by a person skilled in the art through simple experiments. - For boat fishing, it is preferable to add and mix fine coke powder to excess sludge at a ratio of 5 to 30% by weight, preferably 10 to 20% by weight.

Generally, if the addition ratio of fine coke powder is 5% by weight or less,
Since the flocculation and sedimentation effects are small and sufficient dewatering cannot be expected, it is difficult to reduce the water content of the dehydrated sludge cake to 60% by weight or less.

Further, even if the addition ratio of coke fine powder is increased to 30jl:1 or more, the rate of increase in the coagulation/sedimentation effect of the solid content in the sludge is small, and the degree of decrease in the water content cannot be expected to be that great.

Furthermore, as the particle size of fine coke powder increases, the effect of coagulation and sedimentation of solids in sludge tends to decrease.

(Function) When surplus sludge and coke fine powder are mixed, the gas contained in the pores of the coke fine powder is replaced by water, and a double potential layer is formed on the entire surface with a water film, which increases the dielectric constant. is enhanced. It is presumed that the electric charge of the coke powder particles induces a polarization phenomenon, destroying the equilibrium between the solid content and water in the excess sludge, and causing adsorption and aggregation due to electrophoresis.

As a result, the solid content in the excess sludge improves its settling properties, resulting in effective dewatering. By simply adding and mixing only fine coke powder to excess sludge, solids in the sludge coagulate and settle quickly.

Incidentally, the coagulation/sedimentation effect is further promoted by mixing a polymer flocculant, iron chloride, etc. in other than the fine coke powder.

(Example) In the embodiment shown in FIG. 1, excess sludge 1 generated from activated sludge treatment equipment for factory wastewater treatment contains 20,000 ppm of solid content.

First, surplus sludge 1 and coke fine powder 2 generated from coke dry extinguishing equipment are placed in a mixing tank 3 and mixed and stirred. Next, the mixture 4 of excess sludge and coke fine powder is transferred to a static separation tank 5
sent to. The solid content of organic matter and microorganisms in sludge is
The adsorption properties of fine coke powder and the flocculation properties of sludge itself work synergistically to cause adsorption and flocculation, centering on fine coke powder. In this state, fc chain line sludge 6
is sent to a dehydrator 7 and recovered as a dehydrated sludge cake 8. In addition, the supernatant liquid 9 generated from the static separation tank and dehydrator
and F liquid 1o are returned to the activated sludge treatment equipment.

Table 2 shows the moisture content and lower calorific value of the dehydrated sludge cake recovered by the above method. As illustrated in Table 2,
By coagulating and separating excess sludge and then dewatering it using the method of the present invention, the moisture content of the dehydrated sludge cake is as low as 40 to 6% by weight, and the lower calorific value is 30,000%.
It became clear that a very high kcat/ of 9 could be obtained. As a result, it is clear that the dewatered sludge cake is not only extremely easy to incinerate, but can even be used satisfactorily as a fuel.

(Effects of the Invention) As described above, the method of the present invention adds and mixes coke fine powder to excess sludge generated from an aerated activated sludge facility such as factory wastewater, and then separates and dehydrates the excess sludge to increase the moisture content. It is possible to recover dehydrated sludge cake with low heat value and high calorific value, and effective use of steelworks by-products is achieved.
This has great economic effects.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the equipment flow for implementing the present invention. l...Excess sludge 2...Coke fine powder 3...
・Mixing tank 4... Mixture 5... Stationary separation tank 6... Chain line sludge 7... Dehydrator 8.
...Dehydrated sludge cake 9...Supernatant liquid 10...
Offshore liquid Figure 1 1 Surplus 75 sludge 2 Coke fine powder 3: Mixing tank 4: Mixture 5: Static separation tank 6: Chain line sludge 7: Dehydrator 8: Dehydrated sludge cake 9: Clear liquid 10 Filtrate procedure amendment book Showa 83, 9878, 1947 Relationship with the case of the person making the amendment Applicant 4 Agent Address 2-6-2 Marunouchi, Chiyoda-ku, Tokyo 37J11 explanation of the investigation into the details of the Chyusu Pill 33C Go to JL Column Amendment The following matters in the specification of the application are amended and omitted. Note 1, page 9, line 9, [30,000 kca & A7 j] was replaced with “3.00
Correct it to 0 kcal 8 l.

Claims (1)

[Claims] Mixing and stirring coke fine powder with sludge discharged from factory wastewater and other sewage treatment, allowing the mixture to stand, separating it into supernatant liquid and chain line sludge, and dewatering the chain line sludge. A sludge treatment method using fine coke powder, characterized by comprising: