JPH03238058A - Screw decanter type centrifugal concentrator - Google Patents

Abstract

PURPOSE:To prevent the lowering of separation capacity by providing a plurality of pickets to the body part of a screw conveyor so as to radially extend the same toward the inner surface of a bowl. CONSTITUTION:The sludge entering a bowl 1 from a sludge supply port 4 through the hollow shaft part of a screw conveyor 2 settles on the inner wall surface of the bowl 1 to form a sludge compact layer. The pickets 10 provided to the conveyor body part 2a transfer so as to stirr and shear the sludge compact layer at the slow speed corresponding to the rotation difference from the bowl 1. By this action, the solid particle group of the sludge compact layer is rearranged to be dehydrated by squeezing effect. The separated liquid passes through a route separate from the passage of the screw conveyor 2 from a take-in port 7 to be discharged to the outside of the machine from a separating discharge port 8. By this method, water content can be efficiently lowered and the volume reduction of sewage sludge can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a screw decanter type centrifugal concentrator that is applied to the concentration, dehydration, and recovery of solids such as industrial wastewater and sewage.

[Conventional technology]

With the spread of sewage facilities, the amount of sludge generated is increasing. Particularly in recent years, the content of organic matter in sewage sludge has increased, and it has been reported in various places that the sludge concentration has decreased and dewatering performance has deteriorated. In the treatment of this sludge, it is important to efficiently lower the water content in order to reduce the volume and weight of the sludge, and attempts have been made to improve the solids content using various mechanical thickeners. Among these, centrifugal thickeners have excellent operability and a large processing capacity per unit, so together with the development of energy-saving models, centrifugal thickeners are attracting attention as they are being applied as effective mechanical thickeners for difficult-to-separate sludge.

Figure 7 shows one such conventional centrifugal concentrator,
FIG. 2 is a longitudinal cross-sectional view showing an example of a screw decanter type centrifugal concentrator. In the figure, 01 is a cylindrical bowl, and a hollow shaft 01a fixed to both ends is rotatably supported by a rotary bearing 03, and rotates in one direction at high speed. Inside the bowl 01, there is a screw conveyor 0 coaxially with the bowl 01.
2 is provided and rotated in the same direction as the bowl 01 while maintaining a rotational difference.

This gives a centrifugal effect to the solid matter suspension such as sludge (hereinafter referred to as sludge) supplied from the sludge supply port 04 into the rotating bowl, causing the solid particles in the sludge to settle and separate. The sludge is transferred to one end (right end in the illustrated example) of the bowl 01 by the screw conveyor 02 and discharged from the discharge port 06 as thickened sludge with increased solids concentration.
The separated liquid after solids have been separated is discharged outside the machine through a discharge route 08 that is separate from the concentrated sludge. 09 is a cover.

Here, it is thought that the solid particles in the sludge supplied into the bowl 01 rotating at high speed obtain a centrifugal effect and settle on the inner wall of the bowl to form a consolidated layer. That is, the pore water and wedge water of the solid particles in the sludge are removed from the solid particles in the sludge by centrifugal force, and the solids concentration increases. In order to effectively separate and remove the solid particles in the sludge and water, the sludge compaction layer is slowly stirred to separate and diffuse the air bubbles attached to the solid particles in the sludge, and the solid particles are regenerated. Arrangements have been made to enhance the effect of concentrating solid particles.

FIG. 8 shows an example of such a means. In order to improve the solid concentration of the solid particles in the sludge, which forms a sedimentation compaction layer under the centrifugal effect, the inner wall surface of the bowl 01 is A large number of long steel bars 01b (strips) are installed in a convex shape, and solid particles in the sludge are slid and transferred during movement by a screw conveyor, with the intention of rearranging the solids. Also,
Some attempts have been made to create a reverse sliding effect on solid particles by providing a large number of concave grooves on the inner wall surface of the bowl, similar to when a convex bar is provided.

[Problem to be solved by the invention]

The conventional means for slowly stirring the sludge compacted layer are:
Since the inner surface of the bowl is uneven, the gap between the conveyor blade and the edge of the conveyor that conveys the settled solid particles becomes large, causing the solids being conveyed to slip and fall, resulting in a decrease in separation performance. This is particularly noticeable in gel-like solids such as activated sludge, proteins, and metal hydroxides.

[Means to solve the problem]

In order to solve the above-mentioned conventional problems, the present invention provides a cylindrical bowl that is supported by a hollow shaft fixed at both ends and rotates in one direction, and a cylindrical bowl that is coaxially arranged within the bowl and rotates at a different rotational speed than the bowl. A screw conveyor that rotates in the same direction is provided, and solids are separated and settled by centrifugal force from the solid suspension supplied into the rotating bowl, and the solids are transferred to one end of the bowl by the screw conveyor. death,
The solid concentrate liquid and the remaining separated liquid are discharged through separate routes, characterized by a plurality of pickets extending radially from the body of the screw conveyor toward the inner surface of the bowl. This paper proposes a screw decanter type centrifugal concentrator.

[Effect]

In the present invention, the screw blades of the screw conveyor transport concentrated sludge while suitably maintaining a gap between the blade tip and the bowl inner wall surface without stirring the sludge compacted layer formed on the inner surface of the bowl.

On the other hand, a plurality of pickets installed in the body of the screw conveyor and extending radially toward the inner wall of the bowl shear the compacted sludge layer formed on the inner surface of the bowl by the differential speed of rotation with the bowl, rearranging the solid particles. Do this. Then, the pore water and interparticle wedge water between the solid particles are removed, and the solid concentration in the sludge compaction layer is effectively increased.

〔Example〕

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged side view of the picket, and FIG. 3 is a view taken along arrows 1--2 in FIG.

First, in FIG. 1, reference numeral 1 denotes a cylindrical bowl, and raw air shafts 1a fixed to both ends are rotatably supported by rotary bearings 3, and rotate at high speed in one direction. 2 is a screw conveyor having a conveyor body 2a and screw blades 12b, and is disposed coaxially within the bowl 1. Then, it rotates in the same direction as the bowl 1 while maintaining a rotational difference with the bowl 1, that is, at a rotation speed different from that of the bowl 1. A plurality of pickets 10 extending radially toward the inner surface of the bowl 1 are provided in the body 2a between the screw blades 2b of the screw conveyor 2.

4 is a sludge supply port, 6 is a concentrated sludge discharge port, 8 is a separated liquid discharge port, and 9 is a cover.

Next, in FIGS. 2 and 3, IO is a square prism-shaped picket made of structural mesh, and is welded and fixed to the conhair body 2a via a picket mounting seat 10a. 10b
is a bucket cover that is placed over the tip of the bucket 10 and is made of ceramic.

The sludge that enters the bowl 1 from the sludge supply port 4 through the hollow shaft of the screw conveyor 2 settles on the inner wall surface of the bowl 1 due to the centrifugal force generated by the rotation of the bowl 1, forming a sludge compaction layer. The picket lO provided on the conveyor body 2a moves at a speed corresponding to the rotation difference with the bowl 1 so as to slowly stir and shear this sludge compacted layer. This action rearranges the solid particles in the sludge compaction layer and provides a squeezing effect for dewatering. In this way, in the concentrated sludge, the shearing water extraction effect by the picket is added to the centrifugal effect, the solids concentration increases, and the solids accumulate in the lower layer of the sludge compaction layer. The sludge is then raked to one end (the right end in the illustrated example) of the bowl 1 by the screw blade 2b having a minute and appropriate gap between it and the inner wall of the bowl 1, and then pumped up by the skimmer pipe (thickened sludge skimming port) 5. , and is taken out of the machine from the concentrated sludge discharge port 6 through the inside of the hollow shaft. On the other hand, the separated liquid after the solids in the sludge have been separated passes from the separated liquid intake lower to the outside of the machine from the separated liquid outlet 8 through a route different from the above-mentioned thickened sludge passage in the hollow shaft of the screw conveyor 2. It is discharged. As described above, in this example, in addition to the centrifugal effect due to high-speed rotation, the picket shear water squeezing effect is added, making it possible to efficiently increase the solids concentration of sewage treatment sludge, which is difficult to dewater. .

The action of the picket 10 in this embodiment will be described in more detail. FIG. 4 is a diagram schematically showing the bonding state of particles in sludge (sludge solids) and water. In the figure, a represents solid particles and b represents free water. C is a large and small solid particle a (including particle groups)
The majority of this water is water that can be removed relatively easily by gravity settling. In addition, d is capillary bound water, and the wedge-shaped water that exists where the solid particles a touch each other is particularly called wedge water), and forces that act opposite to the surface tension and cohesive force of the capillary, such as centrifugal water. It can be removed by applying force or filtration pressure. e is internally retained water inside solid particle a, and f is surface-adhered water, both of which have a strong binding force with solid particle a and are difficult to remove mechanically.

In this example, the sedimentation and consolidation layer of sludge was collected using a picket 10.
The sludge particles are sheared to rearrange the sludge particles, and the above-mentioned pore water C and capillary bound water d (wedge water) are removed. In other words, picken number 0 is interposed in the sludge compaction layer with an appropriate length that does not disturb the bottom of the sludge compaction layer formed on the inner surface of the bowl 1, and rotates inside the sludge compaction layer at a rotational speed difference with the bowl. acts to shear the solid particles. Then, the picket 10, which moves slowly within the sludge compaction layer at a rotational differential speed, separates and disperses the air bubbles attached to the solid particles, eliminates the bling phenomenon formed by the solid particle groups, and eliminates the particle group in the sludge compaction layer. are rearranged, and the interstitial water C between the solid particles and the wedge water d are separated. In this way, the dewatering effect is enhanced and thickened sludge with a high solids concentration can be obtained at a high recovery rate.

As for the shape of the picket 10, although the effect of shearing the sludge particle group can be expected even if it is a simple round rod shape, in order to enhance the effect, a rectangular rod shape with corners (quadrangular prism shape) is preferable. Since the picket shears the sludge layer at its tip, a ceramic cover 10b is attached to the tip.
It is desirable to add WI abrasion resistance by covering the material with

Next, a test conducted to confirm the effects of the present invention will be described. Using sewage sludge with the properties shown in Table 1, the finished thick sludge concentration was determined when the effect of shearing the sludge layer and squeezing water by the biket was added to the centrifugal effect. The specifications of the centrifugal concentrator used are shown in Table 2. FIG. 5 is a diagram comparing the relationship between centrifugal effect G and separation characteristics of treated sludge in centrifugal thickeners with and without pickets.

Here, the sludge supply amount was 20 m3/h. From Figure 5,
The concentration effect of picket installation is clearly recognized. In addition, looking at the degree to which the centrifugal effect G affects the sludge shearing water extraction effect of the picket, the centrifugal effect G is shown in Table 2 and Figure 6 shows that the sludge shear rate of the picket when the concentration of thickened sludge is 4% (in other words, This is a diagram showing the relationship between the rotational speed difference between the bowl 1 and the screw conveyor 2) and the finished concentration of treated sludge. In order to effectively shear the sludge and rearrange the solid particles, the sludge shearing speed should be between 7 and 100 m/mi.
It was confirmed from FIG. 6 that a range of n, particularly 7 to 30 m/m1n (5 to 2 Orpm), is effective.

〔Effect of the invention〕

In the present invention, a screw conveyor body of a screw decanter type centrifugal concentrator is provided with pickets that extend radially toward the inner wall of the bowl to shear the sludge compaction layer and rearrange the solid particles in the sludge. By adding the water squeezing effect to the centrifugal effect caused by the rotation of the bowl,
The moisture content of sewage sludge, which is difficult to dewater, can be efficiently reduced, and effective volume reduction of sewage sludge can be achieved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged side view of the picket, and FIG. 3 is a view taken along arrows 1--2 in FIG. FIG. 4 is a diagram schematically showing the bonding state of particles in sludge (sludge solids) and water. Figure 5 shows a comparison of the relationship between the centrifugal effect G and the separation characteristics of treated sludge in a centrifugal thickener with and without pickets, and Figure 6 shows the relationship between the sludge shear rate of the picket and the finished concentration of treated sludge. FIG. FIG. 7 is a longitudinal sectional view showing an example of a conventional screw decanter type centrifugal concentrator, and FIG. 8 is a diagram showing an example of means for slowly stirring the sludge compacted layer. 01.1...bowl; Ola, la...
・Bowl hollow shaft; 01b...Strip io2.2・
...Screw conveyor; 2a...Conveyor body; 2
b...Screw blade; 03.3...Rotating bearing;
04,4...Sludge supply port;5...Thickened sludge skimmer pipe;06.6...Thickened sludge discharge port;7...Separated liquid outlet;08.8... Separated liquid outlet, 09,9...cover; 10...bicket; 10a...picket mounting seat; 10b...picket cover; a...solid particles; b...free water; d. ... Capillary bound water; f... Water attached to the surface. C... Pore water; e... Internally retained water;

Claims (1)

[Claims] It is equipped with a cylindrical bowl that is supported by hollow shafts fixed at both ends and rotates in one direction, and a screw conveyor that is arranged coaxially within the bowl and rotates in the same direction at a different rotation speed than the bowl. The solids are separated and settled by centrifugal force from the solids suspension supplied into the bowl, and transferred to one end of the bowl by the screw conveyor to separate the solids concentrate and the remaining separated liquid, respectively. A screw decanter type centrifugal concentrator configured to discharge from a separate route, characterized in that a plurality of pickets are provided that extend radially from the body of the screw conveyor toward the inner surface of the bowl.