JPH02160063A - Method and apparatus for dehydration - Google Patents

Abstract

PURPOSE: To promote the dehydration by supplying a sludge to be dehydrated and a flocculant to a centrifugal separator and mixing them with conc. sludge. CONSTITUTION: A first flocculant is added, and the conditioned sludge is accelerated by the inner cylinder and rotary cylinder 1 of a centrifugal separator and separated into a separated liq. 20 and conc. sludge 19. The separated liq. 20 flows down in the rotary cylinder 1, overflows a dam 4 for discharging the separated liq. and is discharged outside the rotary cylinder 1. The concd. sludge 19 separated in the cylindrical part 1b is conveyed to a conical part 1a by a screw conveyor, and a second flocculant is sprinkled from a nozzle 14. The materials are mixed by an impeller inserted into the sludge to promote the dehydration of the concd. sludge, and the sludge lowered in water content is discharged outside the rotary cylinder 1 from an outlet 3. The dehydration is further promoted in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a decanter-type centrifuge to dewater various types of sludge generated in water, sewage, human waste, industrial wastewater treatment processes, etc. more efficiently than ever before. The present invention relates to a sludge dewatering method and device.

[Conventional technology]

Conventionally, decanter-type centrifuges have been generally used to concentrate and dewater various types of sludge generated in water, sewage, human waste, industrial wastewater treatment processes, and the like.

As shown in Fig. 5, the decanter type centrifuge described above has the following features:
A screw conveyor consisting of a rotating cylinder 1 supported by a bearing 2.2 and rotating at high speed, an inner cylinder 5 rotating in the same direction as the rotating cylinder 1, and a spiral screw blade 6 fixed to the inner cylinder is provided concentrically. It has a structure in which a sludge supply pipe 11 is arranged at the center of the rotating shaft.

The rotary cylinder 1 and the inner cylinder 5 are given a required rotational difference by a differential 7, and the screw conveyor conveys the concentrated sludge 1.9 to the precipitated sludge I-no outlet 3. The rotary cylinder 1 is composed of a conical part 1a and a cylindrical part 1b, and the distal end of the conical part 1a is provided with a settled sludge drain for discharging the concentrated dehydrated sludge conveyed via the dry beach part 17 by a screw conveyor. The cylindrical part 1 opposite to the outlet 3 is provided with an outlet 3.
A dam 4 for discharging the separated liquid 20 is provided at the end of b.

In the decanter-type centrifugal separator having the above configuration, the sludge supplied to the sludge supply section 8 in the separator inner cylinder 5 through the sludge supply pipe 11 passes through the sludge discharge nozzle 14 provided on the inner cylinder wall and is adjacent to the conical part 1a. It is discharged into the pool inside the cylindrical part 1b, but in this case, Figs. 6(a), (b) and (C)
Using the method shown in Figure 1, the supplied sludge is tempered by adding a polymer flocculant, etc., and forms flocs, which are separated by the centrifugal force caused by the high speed rotation of the rotary tube 1.
It is separated into 0 and dark 1ii dirt and 19. Thickened sludge 19
is conveyed by a screw conveyor and discharged to the outside of the rotary cylinder 1 through the precipitated sludge discharge port 3, and the separated a liquid 20 flows down along the spiral screw blades 6 and is discharged from the dam 4 to the outside of the rotary cylinder 1.

(Problem to be solved by the invention) When treating sludge with a dehydrator such as a vacuum dehydrator, belt press, pressure dehydrator, etc., a common method is to add a flocculant, refine the sludge, and dehydrate it. However, it is known that sludge conditioning has a considerable influence on the dewatering effect, and sludge I
jI The device that adds the concentration agent is for the purpose of promoting the dehydration effect.
The sludge and flocculant are thoroughly mixed, and the resulting flocs are given appropriate agitation by rapid or slow stirring to give consideration to their quality.

Even when dewatering sludge using a decanter-type centrifuge, initially a mixing tank for flocculant and sludge was installed, or as shown in Figure 6.
a) A flocculant was added to the sludge supply pipe using the method shown in 1986-11, but centrifugal separation was A method as shown in Figure 6 (b) has been developed in which sludge is tempered by injecting a flocculant into the machine, and has achieved some results in improving the recovery rate and reducing the amount of flocculant added. . However, in such conventional thermal refining methods, the moisture content of the cake after separation and dehydration is still high, and the post-treatment process involves dumping and
The disadvantage is that the costs required for disposal such as landfilling, drying, and incineration are relatively high.

Therefore, in order to further reduce the moisture content of the cake after separation and dehydration, Japanese Patent Publication No. 56-87500 and Japanese Patent Application Laid-Open No. 57-3
As disclosed in Japanese Patent Publication No. 2797 and Japanese Patent Application Laid-Open No. 61-257256, a method of adding two types of flocculants to accelerate the dewatering of sludge was developed, and in a centrifugal separator, the method shown in Fig. 6 (c) Methods such as the one shown in Figure 1-2 have been adopted in which two types of flocculants or the same type of flocculant are divided into two stages and added to the feed sludge or inside the centrifuge.
Among them, a part of the flocculant is passed through the flocculant supply pipe attached to the sludge supply pipe to the conical part 1 of the centrifuge rotating tube shown in Fig. 5.
It was found that the method of adding a to A was quite effective and considerably reduced the moisture content of the cake after separation and dehydration.

However, if we carefully observe the cake that has been dehydrated by the above-mentioned method of adding a flocculant in the conical part 1a and discharged from the centrifuge, we find that it is still insufficient in terms of uniform dehydration, and that the cake surface has the following characteristics: The flocculant added in the conical part 1a may have adhered to the cake, resulting in a relatively high moisture content in some parts of the cake, or the flocculant added in the conical part 1a in Fig. 5 may not have been sufficiently mixed inside the cake. A phenomenon can be seen. If the dehydrated cake discharged in this state is picked up and squeezed lightly, a considerable amount of water can still be removed, so there is room to further reduce the water content of the discharged sludge.

Therefore, the present inventor proposed that if a mechanism was developed to mix the flocculant uniformly and well with the thickened sludge when adding the flocculant in the conical part la of the centrifuge rotating cylinder shown in Fig. 5, the moisture content of the cake could be further reduced. Based on this idea, the present invention was conceived to solve the problems of the sludge dewatering technology described above.

[Means for solving problems]

The sludge dewatering method according to the present invention includes a rotating cylinder consisting of a conical part and a cylindrical part, an inner cylinder arranged concentrically within the rotating cylinder and rotating at a rotation speed different from that of the rotating cylinder, and a rotating cylinder fixed to the inner cylinder. When operating a decanter-type centrifuge equipped with a screw conveyor consisting of spiral screw blades, sludge to be dehydrated is supplied, and the sludge is separated and
The required amount of flocculant to promote concentration and dehydration is supplied into the centrifuge, and the dehydrated sludge is discharged from the outlet at the end of the conical part of the rotating cylinder, and separated from the dam at the end of the cylindrical part of the rotating cylinder. T! A sludge dewatering method in which Ri& is discharged, wherein a first flocculant is supplied to the cylindrical region of the rotating cylinder, a second flocculant is supplied to the conical region of the rotary cylinder, and the inner cylinder The second flocculant and the thickened sludge were mixed in the conical region using a stirring blade attached to the cone.

Further, the sludge dewatering device according to the present invention includes a conical portion and
a screw conveyor consisting of a rotating cylinder consisting of a cylindrical portion, an inner cylinder arranged concentrically within the rotating cylinder and rotating at a rotational speed different from that of the rotating cylinder, and a screw blade fixed to the inner cylinder, and a screw conveyor comprising a screw blade fixed to the inner cylinder; A decanter type centrifugal separator comprising a sludge supply pipe disposed on a shaft, concentrated sludge is discharged from an outlet at the end of the conical part of the rotary cylinder, and separated liquid is discharged from a dam at the end of the cylindrical part of the rotary cylinder. In the machine, an eleventh agent collection supply pipe is provided alongside the sludge supply pipe for supplying a first flocculant to the cylindrical region of the rotating cylinder, and a second flocculant is supplied to the conical region of the rotating cylinder. A second flocculant supply pipe was provided to mix the second flocculant supplied to the conical region with the thickened sludge, and stirring blades were disposed on the outer diameter of the inner cylinder in the conical region.

[Function] In the present invention, the I5 mud supplied to the decanter type centrifuge is tempered by adding a first flocculant in the supply pipe or the cylindrical part of the rotating tube, and then the slurry is heated in the centrifugal separator rotating at high speed. The flocs are accelerated by the rotating cylinder and inner cylinder of the separator, and the centrifugal force separates the flocs into separated liquid and precipitated thickened sludge. A second flocculant is guided into the inside of the centrifugal concentrator screw conveyor by a system different from the first flocculant, and is discharged by centrifugal force from a supply nozzle in the inner cylinder of the screw conveyor, and is conveyed by the screw conveyor. The second flocculant, which is sprinkled on the surface of the thickened sludge and added to the conical part due to the stirring effect of the stirring blades attached to the inner cylinder of the screw conveyor according to the present invention, is well mixed with the sludge and significantly accelerates the dewatering effect. It happens.

(Example b8) Next, the embodiment of the present invention shown in FIGS. 1 to 4 will be described.

The decanter type centrifuge used in the present invention shown in FIG.
Basically, it is similar to the one shown in FIG. 5, which includes a rotating cylinder 1 supported by bearings 2, 2 and rotating at high speed, and a differential gear 7 driving the rotating cylinder 1 at a differential speed. The rotary cylinder 1 is equipped with a screw conveyor consisting of a rotating cylinder 1, a concentric inner cylinder 5, and a spiral screw blade 6 fixed to the inner cylinder 5, and the rotating cylinder 1 consists of a conical part 1a and a cylindrical part 1b integrally connected. A discharge port 3 for discharging settled sludge is provided at the distal end of the conical portion 1a, and a dam 4 for discharging separated liquid is provided at the distal end of the cylindrical portion lb.

A portion of the inner cylinder 5 located in the conical part 1a of the rotary cylinder 1 is provided with a second flocculant supply nozzle 14 and an agitator for promoting mixing of the thickened sludge and the second flocculant conveyed by the screw conveyor. A vane 15 is provided.

A sludge dewatering method according to an embodiment of the present invention using the decanter type centrifuge as described above is carried out as follows.

The sludge that has been tempered by adding the first flocculant by the method illustrated in FIG. 6(a) or FIG. 6(b) is transferred to the inner cylinder 5 and rotating cylinder 1 of a centrifuge that rotates at high speed. The sludge is accelerated by centrifugal force and separated into Rj liquid 20 and concentrated sludge 19, and separated (Pi 20 flows down inside the rotating cylinder 1, overflows from the dam 4 for discharging the separated liquid, and is discharged to the outside of the rotating cylinder 1. The thickened sludge 19 separated in the cylindrical part 1b is conveyed to the conical part 1a by a screw conveyor, and the surface of the thickened sludge in the conical part 1a is coated with a second flocculant supply provided alongside the sludge supply pipe. The second flocculant is supplied through the pipe 13 and the second flocculant supply section 1o provided in the inner cylinder 5 through 2 to 10, typically 4, nozzles 14 provided at equal intervals on the outer diameter of the inner cylinder. 2 to 10 pieces, typically 4 pieces, are installed at equal intervals in the inner cylinder 5 and mixed by stirring blades inserted into the sludge at least 2 a+m below the liquid level, further promoting the dewatering effect of thick 1II sludge. The sludge is discharged from the discharge port 3 to the outside of the rotary cylinder i as sludge with a low moisture content.

Note that the tip of the stirring blade 15 is desirably located at a distance of 2a++n or more from the inner surface of the rotating cylinder of the conical portion.

In addition, the surface of the stirring blade 15 that contacts the sludge forms an angle of 20" to 120 degrees with respect to the sludge conveying surface of the screw conveyor, and the width of the surface that contacts the sludge is 2% to 2% of the pitch width of the screw conveyor. If it is 30%, a sufficient stirring effect can be obtained.

Taking the flocculant addition method shown in FIG. 6(b) and (c) as an example, Comparative Example 1 using one type of flocculant, Comparative Example 2 using two types of flocculant, and Example 2 of the present invention. Comparing the three, the sludge dewatering performance of each centrifuge is shown in the table below.

The flocculant addition rate is the weight (%) of the flocculant relative to the bone dry solid content of the sludge.

Sludge to be tested - - - Experimental machine using sewage digested sludge -
−−−1−−−−Decanter type centrifuge, inner diameter of rotating cylinder−
250 (mm) Experimental machine centrifugal effect---2,100 (G) Screw conveyor rotation differential speed---3 (rpm) Amount of sludge supplied------1,0 ( rr1''/h) As can be seen from the above example, by using two types of flocculants, the water content of the sludge discharged from the centrifuge is approximately 3% lower than that of the method using i1m type flocculants. However, by installing the agitation blade of the present invention, it is further reduced by about 3%.Therefore, according to the present invention, compared to the conventional method using one type of polymer flocculant, it is about 6%. It became possible to reduce the water content of sludge.

(Effect of the invention) It is known that lowering the moisture content of this type of sludge by 1% has a great impact on subsequent treatment such as sludge incineration, but according to the present invention, compared to the conventional method, 3% to 6
% in the sludge water content, and a significant reduction in operating costs can be expected.When considering sludge treatment systems that include sludge incineration, the effect of reducing the sludge water content by the present invention is remarkable. It should be called a thing.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing an embodiment of a sludge dewatering device using a decanter-type centrifugal machine for carrying out the sludge dewatering method of the present invention, and FIG. A side view showing an embodiment in which a stirring blade and a second flocculant supply nozzle are provided in a cylinder, FIG. 3 is a partial side cross-sectional view showing an example of the installation of the stirring blade and the position in the radial direction, and FIG. 4 shows the stirring blade Fig. 5 is a side sectional view of a decanter type centrifuge, Fig. 6 (a), (b),
(c) is an explanatory diagram of the flocculant addition method. 1...Rotating tube 2...Bearing 3...Sludge discharge port 4...Dam 5...Inner cylinder 6...Spiral screw blade 7...Differential 8...Sludge supply section 9 ...
First flocculant supply section 0...Second flocculant supply section 1...Sludge supply pipe 2...First flocculant supply pipe 3...Second 81 collection agent supply pipe 4. ...Second coagulant supply nozzle 5...Agitating blade 6...First coagulant supply nozzle 7...Sludge supply nozzle 8...Beach section 9...Thickened sludge 20...Separation Liquid l...Liquid level (dam height) Subagent Honda Koe Misaki...j Figure 2 Figure 3 Figure 1 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1. A rotating cylinder consisting of a conical part and a cylindrical part, an inner cylinder arranged concentrically within the rotating cylinder and rotating at a rotation speed different from that of the rotating cylinder, and a helical screw fixed to the inner cylinder. When operating a decanter-type centrifugal separator equipped with a screw conveyor consisting of blades, the sludge to be dehydrated is supplied, and an appropriate amount of flocculant is supplied to promote the separation, concentration, and dewatering of the sludge. A method for dewatering sludge, wherein the dewatered sludge is supplied into a centrifugal separator, the dehydrated sludge is discharged from an outlet at the end of the conical part of the rotary cylinder, and the separated liquid is discharged from a dam at the end of the cylindrical part of the rotary cylinder, the method comprising: A first flocculant is supplied to the cylindrical region of the rotary cylinder, a second flocculant is supplied to the conical region of the rotary cylinder, and the second flocculant is supplied to the conical region of the rotary cylinder using a stirring blade attached to the inner cylinder. A method for dewatering sludge using a decanter-type centrifugal separator characterized by mixing sludge with thickened sludge. 2. The decanter according to claim 1, wherein the first flocculant supplied to the cylindrical region of the rotating cylinder and the second flocculant supplied to the conical region of the rotary cylinder are both polymeric flocculants. A method for dewatering sludge using a type centrifuge. 3. A first flocculant supplied to the cylindrical region of the rotary cylinder is a polymer flocculant, and a second flocculant supplied to the conical region of the rotary cylinder is an inorganic flocculant. 1. A method for dewatering sludge using the decanter centrifuge according to 1. 4. A screw conveyor consisting of a rotating cylinder consisting of a conical part and a cylindrical part, an inner cylinder arranged concentrically within the rotating cylinder and rotating at a rotation speed different from that of the rotating cylinder, and a screw blade fixed to the inner cylinder; and a sludge supply pipe arranged on the central axis of the inner cylinder, the concentrated sludge is discharged from an outlet at the end of the conical part of the rotary cylinder, and the separated liquid is discharged from a dam at the end of the cylindrical part of the rotary cylinder. In the decanter type centrifuge, a first flocculant supply pipe is provided alongside the sludge supply pipe for supplying a first flocculant to the cylindrical region of the rotary cylinder, and a second flocculant supply pipe is provided in the conical region of the rotary cylinder. A second flocculant supply pipe was provided for supplying the flocculant, and stirring blades for mixing the second flocculant supplied to the conical region with the thickened sludge were arranged on the outer diameter of the inner cylinder in the conical region. A sludge dewatering device characterized by: 5 The interior of the rotating cylinder is divided into a sludge supply section, a first flocculant supply section, a second flocculant supply section, and a mixing stirring blade section from the cylindrical part of the rotary cylinder to the conical part, and the sludge supply pipe is separated from the sludge supply pipe. The supplied sludge is supplied to the inner region of the cylindrical part of the rotary cylinder through a sludge supply part and a sludge discharge nozzle provided in the inner cylinder, and the first flocculant is supplied through a first flocculant supply part and a discharge nozzle provided in the inner cylinder. The second flocculant is supplied into the cylindrical part, and the second flocculant is supplied into the conical part through a second flocculant supply part and a discharge nozzle provided in the inner cylinder, and the stirring blade mixes the concentrated sludge and the second flocculant into the conical part. 5. The sludge dewatering apparatus according to claim 4, wherein the sludge is agitated and mixed in one part. 6. The sludge dewatering device according to claim 4, wherein the tip of the stirring blade is inserted 3 mm or more deeper than the separated liquid interface in the circumferential direction and is located 2 mm or more away from the inner surface of the conical rotating cylinder. . 7. The sludge dewatering device according to claim 4, wherein the surface of the stirring blade that contacts the sludge forms an angle of 20° to 120° with respect to the sludge conveying surface of the screw conveyor. 8. The sludge dewatering apparatus according to claim 4, wherein the width of the surface of the stirring blade that contacts the sludge is 2% to 30% of the pitch width of the screw conveyor. 9. Claim 4, characterized in that 2 to 10 stirring blades are provided along the surface of the spiral screw blade.
The sludge dewatering equipment described. 10. The sludge dewatering device according to claim 4, wherein 2 to 10 second flocculant discharge nozzles are provided along the spiral screw blade surface.