JPH028761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a flocculation reaction device in which sludge and a flocculant are placed at the bottom of a treatment tank and are agitated with a stirring blade to flocculate and granulate the sludge and flocculant.

<Prior art> In JP-A-54-1961, JP-A-54-153374, and JP-A-61-810 proposed by the present applicant, sludge and flocculant are received at the bottom and flocculated. BACKGROUND ART A flocculation reaction apparatus is known that includes a treatment tank from which sludge is discharged from the upper part, and agitation blades that are vertically mounted in multiple stages on a rotating shaft installed vertically in the center of the treatment tank.

<Problem to be solved by the invention> In the flocculation reaction, the sludge introduced into the tank is quickly mixed with a flocculant (such as a polymer) to form a floc, and a part of this floc is brought into contact and aggregated. It is preferable to form a mass into a mass, use this mass as a core, attach a floc to it, and granulate it into large particles.

However, the stirring blades installed radially on the rotating shaft of conventional reaction tanks are flat plates with a constant width in the height direction of all tanks, both the upper and lower ones. Only horizontal swirl flow occurs in the upper part, and the function of quickly mixing, contacting, and aggregating the introduced sludge and flocculant is insufficient, requiring a long residence time in the treatment tank, and The overall volume cannot be used effectively.

<Means for Solving the Problems> Therefore, the present invention provides a structure in which the lower stage of the stirring blades, which are attached to the rotating shaft in multiple stages in the vertical direction, has a base that is attached to the rotating shaft and has a width in the height direction of the processing tank. The blade is narrow, the tip is wide in the height direction of the tank, and it is shaped like a battledore curved so as to recede in the direction of rotation, and the upper stirring blade is a flat plate with a constant width in the height direction of the processing tank. Additionally, a guide plate is provided on the inner periphery of the bottom of the processing tank so as to gradually move away from the inner periphery of the tank in the direction of rotation of the stirring blade.

<Operation> As a result, the battledore-shaped stirring blades rotate at the bottom of the treatment tank where new sludge and flocculant are introduced, and the flat-plate type stirring blades rotate at the top of the treatment tank, creating a horizontal swirling flow.

The tip of the battledore-shaped stirring blade is wider than the base and is bent so as to move backward in the direction of rotation, so that the sludge in the center of the bottom of the tank is forcefully squirted outward. This flow then swirls and separates into an upward flow and a downward flow near the inner circumference of the processing tank, and the upward flow comes into contact with the horizontal swirling flow caused by the flat stirring blades at the top of the tank, and the flow reaches the center of the bottom of the processing tank. The vehicle is encouraged to descend while turning towards the target. Further, the downward flow swirls along the bottom surface of the processing tank and rises toward the center. Then, the guide plate promotes the downward flow to ascend toward the center while swirling. Thus, at the bottom of the tank, the same degree of vertical swirling circulation flow is generated by the battledore-shaped stirring blades, and these upper and lower swirling circulation flows mix in the center and then separate.

<Example> In the illustrated example, 1 is a cylindrical granulation processing tank, 2 is a rotating shaft installed vertically in the center of the processing tank 1 and rotationally driven by a motor and a transmission, 3 and 4 5 shows a sludge supply pipe and a chemical injection pipe that supply sludge and flocculant to the inner bottom of the treatment tank, and 5 shows an outlet for flocculating sludge.

In this embodiment, stirring blades are attached radially to the rotating shaft 2 in two stages, upper and lower, with a phase of 180°. The width of the base part 6a is narrow in the height direction of the tank, and the width of the remaining tip part 6b is in the shape of a battledore, which is wide in the height direction of the tank. Specifically, the battledore-shaped stirring blade 6
The length ratio of the base portion 6a to the tip portion 6b is approximately 1:1 in the radial direction of the blade, and the width ratio is approximately 1:3 in the height direction. Further, the upper stirring blade 7 that rotates in the upper part of the tank has a wide flat plate shape with a constant width in the height direction of the tank over the entire length.

Therefore, when the rotating shaft 2 is driven, a horizontal swirling flow a is generated by the flat stirring blades 7 in the upper part of the processing tank.
At the bottom of the treatment tank, the battledore-shaped stirring blades generate the vertical swirling circulation flows b and b' described in the section of the above-mentioned function. As a result, the new sludge and flocculant introduced into the bottom of the treatment tank from the sludge supply pipe 3 and the chemical injection pipe 4 ride on the upper and lower swirling circulation flows b and b', are sufficiently mixed, grow into flocs, and grow into flocs. The flocs in this area form a lump together with the contact, and are gradually pushed up by the subsequent sludge and coagulant to the upper part of the treatment tank where the flat stirring blade 7 rotates, and the flocs adhere to the lump formed together. The granules roll on the inner circumferential surface of the processing tank on the horizontal swirling flow a, become dense and granulated with increasing strength, and successively flow out from the outlet 5.

As shown in the figure, the wide tip 6b of the battledore-shaped stirring blade 6 is bent at an angle of, for example, 45 degrees so as to move backward with respect to the rotating direction of the blade. The flocs are strongly pushed toward the inner periphery of the flocs to thoroughly mix the sludge and flocculant, and to encourage the flocs to come into contact with each other.

Furthermore, at the lower end of the inner periphery of the processing tank, a guide plate 8 is provided that extends in the direction of rotation of the stirring blade 6 and is linear or curved as shown in the figure and gradually moves away from the inner periphery toward the tip. The circulating flow b' is encouraged to move upward toward the center while swirling along the bottom of the tank. Incidentally, the upper swirling circulation flow b contacts the horizontal swirling flow generated by the flat stirring blade and is urged to descend toward the center while swirling. As a result, the upper and lower swirling circulation flows b and b' mix vigorously, improving the mixing effect of the sludge and flocculant, and further promoting contact and association between the flocs.

In this embodiment, the stirring blades 6 and 7 in the upper and lower stages are
The number of sheets attached to the rotating shaft 2 is two, but three or more sheets may be installed at equal intervals. Further, the number of upper and lower stages is not limited to two, but may be three or more.

Furthermore, although the sludge supply pipe 3 and the chemical feed pipe 4 are shown to supply sludge and flocculant to the center of the bottom, they may be supplied into the tank from the lower end of the inner circumference of the tank.

As a result of processing using the aggregation tank as described above, specifically, a processing tank under the following conditions, dense, strong, and large granules were obtained. Tank capacity: 100,
Rotation speed of rotating shaft: 40 rpm, length of both stirring blades 6, 7: 40 cm, width of flat stirring blade: 8 cm, length of base 6a of battledore type stirring blade: 10 cm, length of base 6a of battledore type stirring blade. Width: 4cm, length of tip 6b of battledore-shaped stirring blade: 10cm, width of tip 6b of battledore-shaped stirring blade: 12cm, terminal speed of both stirring blades: 50
m/min, sludge retention time: 6 minutes. Note that this is an example when the tank capacity is assumed to be 100, and if the tank is made larger, the stirring blades etc. may be made similarly larger.

However, since granulation is affected by the speed at the end of the stirring blade, it is important to vary the rotational speed so that the speed is about 40 to 60 m/min.

<Effects of the Invention> According to the present invention, the entire volume of the tank is effectively utilized, the sludge and flocculant introduced into the bottom of the tank are sufficiently mixed to form a floc, and the flocs are brought together. It is possible to produce granulated sludge with large particle size and strength by forming sludge into clumps and then contacting the sludge with flocs, and it has excellent effects such as good drainage in the subsequent dewatering process and a lower water content. Demonstrate.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a partially cut away treatment tank according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along the - line in FIG. Rotating axis, 6
indicates a battledore type stirring blade, 7 indicates a flat plate type stirring blade, and 8 indicates a guide plate.

Claims (1)

[Scope of Claims] 1. A treatment tank that receives sludge and flocculant at the bottom and discharges granulated sludge from the top, and a rotating shaft vertically installed in the center of the treatment tank, which is installed in multiple stages in the vertical direction. In a flocculation reaction device equipped with rotating stirring blades, the lower stirring blade has a base portion attached to the rotating shaft that is narrow in the height direction of the processing tank, and a tip portion that is narrow in the height direction of the tank. The upper stirring blade is shaped like a flat plate with a constant width in the height direction of the processing tank. A flocculation reaction apparatus characterized in that a guide plate is provided that gradually moves away from the inner periphery of the tank in the rotating direction of the stirring blade.