JPH02120B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an efficient dewatering device for various types of sludge using a screw press.

The sludge to be dehydrated in the present invention is anaerobic or aerobic digested sludge of human waste or night soil, human waste septic tank sludge, sewage or human waste digested liquid, surplus sludge in activated sludge treatment of various industrial wastewater, and initial sedimentation of sewage. It is a type or mixture of pond sludge, coagulated sludge of various industrial wastewater, and coagulated sludge generated in tertiary treatment of human waste, sewage, etc.

A rotating screw is housed in an outer cylinder made of a punching plate, and sludge is supplied to one end of the outer cylinder, and as the screw rotates, the sludge is moved inside the outer cylinder toward the other end, while the moisture in the sludge is removed from the outer cylinder. A screw press is conventionally known in which a dehydrated cake is obtained at the other end of an outer cylinder. This screw press transports sludge in an outer cylinder,
The pressure increase in the outer cylinder, which is the pressurizing force for dewatering, depends on the rotation of the screw, so if the sludge is suitable for the screw press, the pressure will increase smoothly, dewatering can be carried out efficiently, and the structure is In addition to being simple and easy to manage, it has the advantages of not generating noise and lowering the moisture content of sludge by heating the screw.
If the strength of the sludge is weak, that is, if the sludge is not suitable for the screw press, the sludge will slip even if the screw rotates, the screw will simply rotate idly, and the pressure will not increase, or the sludge will be stuck to the punching plate of the outer cylinder. There is a problem that the sludge cannot be sufficiently dehydrated due to leakage from the pores.

Therefore, in the present invention, in order to efficiently dewater sludge using a screw press as a dehydrator, a flocculant is added to the sludge to be dewatered, and the sludge is flocculated in a flocculation tank to increase the strength of the floc. This flocculated sludge was dewatered by being forced into a screw press using a positive displacement screw pump. The present invention will be described below with reference to the drawings.

1 indicates a flocculation tank, and sludge is supplied to the flocculation tank 1 through a supply pipe 2, where a flocculant is added from a chemical injection device 3.

The flocculant to be added may be either an inorganic flocculant or an organic flocculant, but both can also be used in combination. Inorganic flocculants include aluminum chloride, polyaluminum chloride, aluminum sulfate, iron chloride (), iron sulfate (), iron chloride (), iron sulfate (),
Copperus chloride, polyferric chloride, polyferric sulfate, etc. are available, and one or more of them can be used.

In addition, as the cationic organic flocculant, chitosan aminoalkyl acrylate or aminoalkyl methacrylate homopolymers or copolymers with acrylamide or other monomers, Mannitz modified polymers containing acrylamide or methacrylamide as a constituent unit, or Hoffman decomposition products, polyamide polyamines, polyvinylimidazolines, polyethylene imines, polydialkyl diallylammonium salts, etc. can be used, and one or more types of these can be used.

When these inorganic flocculants and/or cationic organic flocculants are added to sludge and stirred in tank 1, flocculation occurs and flocs are produced. At this time, in order to grow flocs, it is preferable to further add a nonionic or anionic organic flocculant and stir. Nonionic or anionic organic flocculants include polyacrylamide,
Examples include polyacrylamide partial hydrolyzate and atrium polyacrylate.

In the case of inorganic flocculants, the amount of flocculant added depends on the amount of sludge.
1 to 5% by weight of SS, 1 to 3% by weight for cationic organic flocculants, and 0.3 to 1% by weight for nonionic or anionic organic flocculants added later for floc growth. .

The flocs produced by flocculating sludge containing a large amount of fiber, such as surplus sludge from activated sludge treatment of human waste or paper pulp wastewater, are hard to break and strong, so flocculation treatment as described above is sufficient. be. However, even if excess sludge such as sewage or food wastewater is flocculated, the strength of the resulting flocs is weak, so the flocculation treatment is carried out in two stages using a primary flocculation tank 1 and a secondary flocculation tank 1'.

That is, the above-mentioned cationic organic flocculant is added to the sludge, and strong stirring is performed using the primary flocculant. This strong stirring allows the sludge to react uniformly and sufficiently with the flocculant,
This is to neutralize the electric charge and facilitate the formation of flocs in the next secondary flocculation tank, and it is desirable that the agitation be strong enough not to generate flocs with a diameter exceeding 2 mm.

The sludge whose charge has been neutralized in the primary flocculation tank is supplied to the secondary flocculation tank 1', where an anionic organic flocculant is added by the chemical injection device 3' and slowly stirred to form flocs. let Examples of anionic flocculants to be added include sodium polyacrylate or sodium polymethacrylate, partial hydrolysates of polyacrylamide or polymethacrylamide, copolymers of acrylic acid or methacrylic acid and acrylamide or methacrylamide, acrylic acid or methacrylate. One or more types can be used, such as a terpolymer of acid, acrylamide or methacrylamide, and 2-acrylamido-2-methylpropanesulfonic acid or vinylsulfonic acid, sodium carboxymethyl cellulose, and the like.

When slow stirring is performed in this secondary flocculation tank 1', the sludge particles whose charge has been neutralized by reacting with the cationic polymer flocculant are coagulated by the crosslinking action of the anionic polymer flocculant into a strong and large size. , and the dehydration properties are extremely good.

In this manner, the sludge is flocculated in the flocculation tank to produce strong flocs, which are then forced into the sludge feed port at one end of the screw press 5 using the positive displacement screw pump 4.

Figures 2 and 3 show an example of a positive displacement screw pump, which includes a stator 7 made of synthetic rubber and having a double-threaded hollow part 6 with an oval or oval cross section, and a stator 7 that passes through the hollow part of the stator and rotates eccentrically. The rotor 8 has a single-threaded metal rotor 8 with a circular cross section, and a gap 6' with a constant volume is formed in the hollow part of the stator between the stator and the rotor. moves along the axis to perform a pumping action,
Discharge port 9' of tip tube 9 connected to the front end of the stator
Discharge from.

A rear cylinder 10 is connected to the rear end of the stator, and sludge is supplied to a supply port 10' in the rear cylinder. Further, a drive shaft 11 driven by a motor to rotate the rotor 8 is supported by a bearing in a bearing box at the rear of the rear cylinder, enters the rear cylinder, and is connected to the rotor through universal joints 11a and 11b. Connect with the rear end. The stator 7 is vulcanized onto the inner periphery of a metal outer tube 7' and is integrated with the outer tube 7'.

In this way, a positive displacement screw pump is formed between the double-threaded hollow part of the stator and the single-threaded rotor that passes through it and rotates eccentrically according to the inner shape of the hollow part. Since the moisture of the sludge and the flocs floating in the moisture are transferred in the gap 6' of a constant volume that moves spirally toward the 9', there is no pulsation in the transfer and no impact is applied to the transferred material. Therefore, even if the flocculated sludge is transferred, the flocs in the sludge can be press-fitted into the screw press with almost no disintegration, and the flocculant and other chemicals added in advance with the chemical injection device will mature during the transfer. The water content of the sludge is lowered through secondary flocculation.

The flocs thus discharged from the discharge port 9' of the screw pump are led to the slurry supply port of the screw press 5 through the pipe 12 and press-fitted therein. At that time, a pressure detector (not shown) is installed in the mud feed port of the screw press 5, and the screw pump 4 is controlled by the pressure signal.
It is preferable to adjust the pressure inside the slurry inlet to 0.2 to 1.5 Kgf/cm ² G.

FIG. 4 is a longitudinal cross-sectional view of the screw press, which has a mud feed port 14 at the upper end of one end of an oblong cylinder 13 made of a perforated punching plate with a hole diameter of about 1 mm. Inside the cylinder, a tapered rotor 15 connects the small diameter part to one end of the cylinder.
It is installed concentrically with the large diameter part facing the other end of the cylinder, and is rotated by a motor or the like. On the outer periphery of the rotor 15 is a spiral blade 1 whose outer diameter matches the inner diameter of the cylinder 13.
6 is provided, and the helical blade 1 is formed by the rotation of the rotor.
Numeral 6 is a slurry feed port 14 which propels the floc supplied to one end of the cylinder toward the other end.

In this way, the rotor has a taper, and the annular gap between the outer periphery of the rotor and the inner periphery of the horizontally long cylinder becomes gradually narrower from one end of the horizontally long cylinder to the other end.

Therefore, the floc supplied inside one end of the horizontally long cylinder moves toward the other end under low pressure while dehydrating water through the holes of the cylinder at the one end side where the annular gap is wide, and in the middle part of the horizontally long cylinder, the annular gap is wide. As it narrows to a certain extent, it is pressurized to a medium level and dehydrated in the same way, and at the other end it is pressurized to the maximum and dehydrated in the same way, and finally it is discharged from the other end of the oblong cylinder as a dehydrated cake. Ru.

Moreover, since the flocs are continuously press-fitted into the screw pump 4 through the piping 12 and supplied to the slurry supply port 14, the flocs move while being dehydrated while filling the inside of the screw press tightly.

The flocs have strength due to the coagulation process and will not be destroyed by the pressure inside the screw press, so the screw press dewaters the flocs under an ideal pressure rise, greatly improving the efficiency of sludge dewatering. improves.

Note that the rotor may be heated by supplying steam to the inside of the rotor, if necessary.

In this way, according to the present invention, sludge is coagulated into a strong floc, which is continuously press-fitted into a screw press using a positive displacement screw pump, and the function of the screw press is maximized to dewater the sludge. Can be done.

[Brief explanation of drawings]

Fig. 1 is a flow sheet showing an embodiment of the present invention, Fig. 2 is a longitudinal cross-sectional view of an example of the positive displacement screw pump used above, Fig. 3 is a cross-sectional view taken along the - line in the same above, and Fig. 4 is a cross-sectional view of an example of the positive displacement screw pump used above. This is a vertical cross-sectional view of an example of the screw press used in Figure 1. In the figure, 1 and 1' are the flocculation tank,
4 is a positive displacement screw pump, and 5 is a screw press.

Claims (1)

[Claims] 1. A sludge dewatering device comprising a coagulation tank for coagulating sludge, a screw press for dewatering the coagulated sludge, and a positive displacement screw pump for pressurizing the coagulated sludge from the coagulation tank into the screw press. .