JPS58143898A - Treatment of sludge - Google Patents

Abstract

PURPOSE:To conserve the consumption amounts of a flocculant and auxiliary fuel in an incinerator, in the course of treatments for dehydrating and burning sewage sludge, by circulating incineration ash discharged from an incinerator to the side of a dehydrator to use it as a dehydrating assistant. CONSTITUTION:Sewage sludge is poured into a mixer 5, mixed with FeCl3 as an inorganic flocculant at a ratio of about 10% on the basis of the sewage sludge and then sufficiently agitated. In succession, the sludge is transferred to a mixing tank 4, and incineration ash discharged from an incinerator 1 in the following step is concurrently added through a hopper 3 to the sludge at an approximately equal ratio and mixed with the sludge. Thereafter, the mixture is charged in a filter press dehydrator 2, compressed and dehydrated therein, supplied as dehydrated cake having a small water-retaining ratio to a fluidized-bed oven 1, and burnt by adding a small amount of auxiliary fuel. Since the incineration ash is utilized as a dehydrating assistant, the reduction of the capacity of the dehydrator into a small size, the save of the flocculant and the remarkable savings of the auxiliary fuel in the incinerator can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a treatment method comprising a dehydration step using a flocculant and a dewatered cake incineration step.

The dehydrated sewage sludge cake is disposed of by incineration [6] The moisture content of the dehydrated cake is about 75% to 85%, and it has the disadvantage of requiring auxiliary fuel for incineration.

The present invention has been developed to solve the above-mentioned drawbacks in an integrated system of dehydration and incineration, and to reduce the moisture content of the dehydrated cake to near the self-combustion range during dehydration treatment using a dehydrator, thereby reducing the amount of auxiliary fuel necessary for incineration treatment. This is a proposed method in which a flocculant is added to sludge, J dehydration treatment is performed, and then incineration treatment is performed, in which the incineration ash of the sludge discharged in the incineration treatment step is recycled to the dehydration treatment step, and dewatering A is used as a dehydration aid.
Provided is a sludge treatment method characterized by adding i+ to sludge.

According to the present invention, in an integrated dehydration-incineration treatment system for sewage sludge, incineration ash of sludge discharged from an incinerator such as a fluidized bed furnace is recycled to the dehydrator side and used as a dehydration aid.

It is possible to reduce the size of the dehydrator container, reduce the amount of flocculant, and significantly reduce the amount of auxiliary fuel used in the incinerator.

Next, an embodiment of the method of the present invention will be described based on the drawings.

Figure 1 shows the processing flow when a filter press or empty dehydrator is used as the dehydrator, and the sludge is transferred to the mixing tank 5 and ferric chloride (approximately 10% of the sludge solid content) as an inorganic flocculant.
At the same time, approximately the same amount of incinerated ash as the solid content of the sludge is added from the incinerated ash hopper 3 to the mixing tank 4, and after sufficient stirring, the incinerated ash is supplied to the dehydrator 2. The sludge dehydrated cake dehydrated in the dehydrator 2 is incinerated in the fluidized bed furnace 1, and the required amount of incinerated ash (the same amount as the sludge solid content) is transferred IJ-IJ to the incinerated ash hopper 3, and the remaining amount is dispose.

Figure 2 shows the case where a belt press dehydrator is used as the dehydrator (~Add the same amount of incinerated ash as solid sludge from the sludge and incinerated ash hopper 13 to the mixing tank 14, mix thoroughly, and then mix. Transfer to tank 15.

In the mixing tank 15, the solid content in the sludge (original sludge) is approximately 0.7 to 0.
Approximately 9% polymer flocculant is injected and thoroughly stirred to generate flocs, which are then supplied to the belt press dehydrator 12. The following is the same as in FIG.

According to these methods, the strength of the floc increases (-9) by adding incinerated ash, which reduces the moisture content of the dehydrated cake and improves the processing speed.Furthermore, in filter presses and vacuum dehydrators that use inorganic flocculants, slaked lime (sludge) Solid content approximately 20
%) is no longer necessary, and the dehydration cake is now in the self-combustion range.

Filter press (pressure dehydrator) of the first embodiment (Fig. 1)
In a vacuum dehydrator (belt filter), the former has a squeezing force of 5 to 20 ky/cA, which is above the cylinder pressure.

In order to prevent the destruction of cohesive flocs, it is necessary to form dense flocs with strong floc strength. The latter is low pressure (
-500 to 600m+nH20), but it is necessary to form a dense floc with good water drainage.

When flocculated with an inorganic flocculant, the floc diameter is small (05
The sludge (below) is ideal for these dewatering machines because it is dense and has strong flocs and creates gaps (water passages) between the sludge.

After adding incinerated ash to sludge, it is flocculated using a polymer flocculant.This method involves adding incinerated ash to raw sludge to increase the ratio of inorganic to organic content in the raw sludge, and dewatering the sludge. This is to promote sexual improvement.

In the belt press dehydrator of the second embodiment (Fig. 2), it is important to separate a large amount of free water in the gravity dehydration section at the beginning of the dehydration process, so the diameter of the flocs is large (usually 4 to 5 k). degree) A polymer flocculant that forms flocs from which free water can be easily separated is most suitable.

'Also, inorganic flocculant ferric chloride is used to flocculate the sludge and then incineration ash is added.This ferric chloride neutralizes the surface charge of fine particles in the sludge and binds the attraction between the nine particles. It has the function of forming agglomerated flocs as a force, and then performing filter filtration using the incinerated ash as a core, and the function of further increasing the strength of the floc.

Next, the range of suitable addition amounts of the inorganic flocculant and the polymer flocculant will be explained.

+Il Inorganic flocculant The suitable addition amount varies depending on the properties of sewage sludge, but according to experiments, ferric chloride is 5 to 10% per solid matter in sludge.
Slaked lime is 10-40%. The standard amount of ferric chloride added to sewage sludge (digested sludge) is 10%.

It is 20% slaked lime.

The properties of the sewage digested sludge used in this experiment are shown in the table below.

Table 1 (2) Polymer flocculant A cationic flocculant is effective for sewage sludge, and Figure 3 shows that the gravity is 1.
The amount added is preferably 0 to show the relationship between the amount of 1 and the aggregation effect.
In the range of 5%788 to 14%/BB, the optimal point is 08 to 0
It is 9% 78B.

Here, the O8T value is OaI: 111ary 5ucti
In terms of on-time value, the lower the Sea value, the better the filterability. The floc strength is the value obtained by pressurizing the flocculated slurry at a constant pressure and dividing the spread area by the pressure, so the larger the absolute value, the stronger the floc strength.

However, the degree of cationicity depends on the properties of the sewage sludge.

Since the mol% also changes, it is necessary to select the flocculant and measure the optimum amount added each time. This is because polymer flocculants have stronger selectivity with respect to sludge in floc formation than inorganic flocculants.

Next, the effects of the method of the present invention will be specifically explained using experimental data. The results are shown in Tables 1 and 2.

The cake moisture was 645% under the conditions of normal chemical dosing of ferric chloride 10%/S8° and slaked lime 20%/ss in a filter press, but the cake moisture was 645% with ferric chloride 10%/6S and incinerated ash 100%/sB.
Under the conditions of , the cake moisture was 478%, and in the belt press, under the conditions of polymeric injection 09% HaS, when no incineration ash was added, the moisture was 767%, and when 100%/ss was added, the moisture was 616%, and the processing speed was 17%. % to 26%.

(1) When using a filter press (Table 1) (2
) When using a belt press (Table 2) (c) Total dry net calorific value of 1 raw sludge 3.110 kJ "9, auxiliary light 1
! Net calorific value IQ of 4, QQQKcal/9. The latent heat of vaporization of water was determined to be 660 Kcal/9H20, and the incinerator efficiency was 45%.

2 Sewage sludge was incinerated in a fluidized bed furnace (CTl' furnace) as incineration ash (average particle size: 50 μm), heavy oil was used as auxiliary fuel, and Himorok MP-473E was used as a polymer flocculant.

[Brief explanation of drawings]

FIG. 1 shows a flowchart showing the first embodiment of the method of the present invention.
-7-), Figure 2 is a flow sheet showing the second embodiment of the method of the present invention, and Figure 3 is a diagram showing the relationship between the amount of polymer flocculant added, the floc strength number, and the O8'l' value. be. 1.11・Fluidized bed furnace, 2.12...Dehydrator, 3.1
3... Incineration ash hopper, 4.14... Mixing tank, 5.1
5...Mixing tank. Agent Akira Sakama 1st figure 2nd area,, Ikukatatami (%15) Kuzu 3rd figure 502-

Claims (1)

[Claims] In the method of adding a flocculant to sludge, dehydrating it, and then incinerating it, the incineration ash of the sludge discharged in the incineration process is recycled to the dewatering process and added to the sludge before dewatering as a dewatering aid. Characteristic sludge treatment method.