JPS5990687A - Pressure flotation device - Google Patents

Abstract

PURPOSE:To eliminate the adverse influence occuring in the shearing force, etc. generated as a result of nonuniform swirling flow, turbulence, vortex flow, etc. by constituting a pressure flotation device which maintains the water depth in the flotation section at 40-60cm and flows waste water from the central part toward the outside circumferential part. CONSTITUTION:Pressurized water in which air is dissolved under high-pressure conditions flows through a pipe 9 into a reducing valve 10, where the pressure is reduced and said water is joined with an introducing pipe 8 for waste water. A flocculating agent is added to the water from a pipe 11 right after the joining of the waste water and the pressurized water, then the water flows through an adjusting valve 12 for an inflow rate and an inflow port 13 into an annular water passage 14 around a pipe 18 from the direction tangetial. The inflow water arrives at the top end of the passage 14 while swirling and ascending in the passage 14, then it flows while swirling downward in the annular water passage 19 between partition walls 15 and 16 and when the water arrives at a bottom plate, it ascends in the annular water passage 20 between the partition walls 16 and 17 while swirling upward until it arrives at the water surface where the water is admitted gently into the flotation section on the outside of the wall 17.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure flotation separation device, and in particular, when solid particles suspended in wastewater are separated and removed by a pressure flotation method, the flotation effect is promoted. This invention relates to a pressurized flotation separation device that maximizes separation efficiency.

Generally, 5-12% (volume ratio) of air can be dissolved in water under high pressure of 3-6 kg/crtt. High pressure water that dissolves this air (hereinafter referred to as pressurized water)
When the pressure is reduced to atmospheric pressure or close to it, the air dissolved in the rice field becomes supersaturated, so the diameter becomes 50 to 100 mm.
Micron (micron) microbubbles are deposited in the water. The pressure flotation method is a method in which these microbubbles are attached to solid particles floating in water, and the buoyancy of the bubbles is used to float and separate and remove the solids.

Here, a conventional circular pressurized flotation separation device is shown in FIG. The wastewater is mixed with pressurized water containing a large amount of microbubbles, then a flocculant is added, and the wastewater flows into the pressure flotation device through pipe 1. Further, the tube 2 having a large diameter at the center is ascended and flows into the flotation separation tank from the top, and the floating figures in the water with attached microbubbles rise toward the water surface and are separated. The water depth of conventional pressurized flotation tanks is 2-3 m, and the water depth of large equipment is 3 m.
．． It may reach 5711, and the residence time is 40-60
However, since wastewater containing a large amount of microbubbles has a small average density, it becomes a density flow 40 to 60 cr below the water surface.
It flows between rL from the center toward the outer circumference at high speed. When it reaches the partition wall 3, it flows downward, and when it reaches the lower end of the partition wall 3, it rises through the channel 4 between the partition wall 3 and the inner wall of the water tank, falls through the overflow weir 5 into the water channel 6, and flows into the water discharge pipe 7. It will be drained out.

In flowing water, local turbulence and eddy currents always occur to a greater or lesser degree, which prevent the natural floating of solids in the water, but in conventional flotation separation devices, the density currents mentioned above are the cause. hand,
As shown in the figure, a swirling flow is generated in the flotation separation tank. This swirling flow accelerated the density flow, and the shearing force generated by the non-uniform flow velocity within the bed removed air bubbles attached to solids in the water, and destroyed flocs υ.
Alternatively, there has been a phenomenon in which the solid particles once floated and separated are transported downward near the entire partition wall 3, deteriorating the quality of the treated water and producing fc9 and precipitates.

The present invention was born out of analysis of the operating conditions of many production equipment with a processing water volume of 2,000 m/day to 2,000 m/day, and research using several types of experimental equipment.
By performing flotation separation only in the density flow part, that is, within the water depth range of 40 to 60α, the problems caused by the swirling flow, turbulence, eddy current, and non-uniformity of flow velocity observed in conventional flotation separation equipment. This eliminates the negative effects of shearing forces, etc., and enables flotation separation under conditions close to laminar flow.

With conventional pressurized flotation devices, 4 to 4.8 per 1 mf of flotation area
It was possible to process only rm:/hour, and the residence time in the processing device was 40 to 60 minutes, but due to inventiveness, the processing rate was 97 to 10 g/hour per 1 m of floating area, which is about the same as that of the conventional device. Double processing is possible υ, residence time in the processing equipment is 3 to 5 minutes, i.e.
The time was reduced to about one-tenth (1/10) of conventional equipment.

Regarding water quality, suspended solids (5 uspen) in treated water
ded5olid) was reduced by 30-50% compared to conventional flotation equipment.

The second feature of the present invention is that it focuses on the 5tokes law regarding the floating speed of suspended solids in wastewater.

The 5tokes law is expressed by the following equation.

μ vf: Floating speed g Gravitational acceleration D = Diameter of solid particles ρl: Liquid density of wastewater ρS° Density of solid particles (if bubbles are attached) Average density including bubbles μ: Liquid viscosity of wastewater In this case, g is a constant, and ρ4 and μ can hardly be changed in practice. When trying to increase the floating speed Vfi by water treatment technology, the most effective method is to increase the diameter of the particles. This is because the floating speed is proportional to the square of the particle diameter. Usually, polymer flocculants (,
Polymer) is added, but an optimum stirring speed is required to maximize its effect. Although there are some differences depending on the type of wastewater, water temperature, and type of flocculant used, first stir at medium speed, then stir at slow speed, and gently pour into the flotation separation section so as not to destroy the generated flocs. It is necessary to introduce With conventional equipment,
As shown in Figure 1, in many cases there is no agitation mechanism, and if a flocculation reaction tank is specially provided, a flocculation reaction tank equipped with an agitator is installed outside the flotation separator, and the wastewater after the flocculation reaction is piped. It is installed in the flotation separation tank. In this case, the flow rate in the introduction tube is 15 to 2. sm/sec, the coagulated flocs (Floc) once generated are destroyed within the tube, so it was necessary to add a large amount of coagulant to prevent this. Therefore, the second feature of the present invention is that a bypass type flocculation reaction tank is provided near the center of the circular pressurized flotation device, making it possible to introduce wastewater into the flotation separation section at a slow speed. There it is. Furthermore, since a bypass type stirring method was adopted, power such as a stirrer was not required.

The third feature of the present invention relates to the shape of the bypass type aggregation reaction section, which is the second feature of the present invention. Cylindrical bulkhead (baffle plate) 15 in FIGS. 2 and 3. ．． The wastewater detours through the annular waterway 14.19.20 divided by 16.17, the optimum stirring conditions for the flocculation reaction are satisfied, and the wastewater is introduced slowly and uniformly into the surrounding flotation separation section. This made it possible.

In addition, large-scale treatment equipment (the amount of water treated per unit is 10.0
00 m3/day or more), the cylindrical partition wall may be provided with notches 32a and 33b to form a slit-shaped partition wall. This is shown at 32.33 in FIGS. 4 and 5.

A fourth feature of the present invention relates to a method for introducing wastewater into the flocculation reaction section according to the third aspect of the present invention. That is, as shown in FIG. 5, an inlet is provided for the annular waterway closest to the center among the plurality of annular waterways so as to introduce wastewater in the direction of the liquid glands. Therefore, according to the third feature of the present invention, in addition to vertical stirring, horizontal rotational stirring can be performed, and the partition wall (baffle plate) required for stirring using only the bypass method can be reduced to about 3. We succeeded in reducing the number to one-third (1/3). It has been confirmed through experiments that an inflow velocity of 1 to 3 m/sec is most effective.

These 4 of the present invention? By combining these features, we succeeded in reducing the consumption of flocculant by 30-60%.

Next, the present invention will be explained based on drawings showing examples.

2 and 3 show the flow of water according to the present invention, and FIGS. 6 and 7 show the method of discharging the removed solid particles.

In FIG. 2, pressurized water containing air under high pressure passes through pipe 9 to a friction valve (Friction V).
The wastewater flows to a pressure reducing valve 10 called an alve, where the pressure is reduced and it joins the wastewater inlet pipe 8. Immediately after the wastewater and pressurized water are combined, a flocculant is added through the pipe 11, and flows into the annular waterway 14 around the circumference of the pipe 18 from the inlet 13 through the inflow speed control valve 12 in the rim direction. The inflow water rises while swirling in the annular waterway 14f, and when it reaches the upper end of the annular waterway 14, it flows downward in the annular waterway 19 between the partition wall 15 and the partition wall 16 while swirling, and when it reaches the bottom plate, it flows between the partition wall 16 and the partition wall 1.
It ascends while turning upward in the annular waterway 20 between 70 and 70, and when it reaches the water surface, it gently flows into the flotation separation section outside the partition wall 1Y.

The width of the annular waterway 14.19.20 is that the swirling and rising and falling flow speeds are outside! Since it is designed to become smaller as it advances, the annular waterway 14 is agitated at medium speed, and the annular waterway 20 is agitated at a slow speed. Furthermore, since the optimum agitation speed varies somewhat depending on the type of wastewater, water temperature, type of flocculant added, etc., it is preferable to control the inflow flow rate of wastewater using the inflow speed control valve 12. In the flocculation reaction part arranged in the annular waterway 14.19.20, the suspended solids in the wastewater grow into flocs with a large diameter, and the fine air bubbles precipitated from the Caro pressure water are A large amount of it adheres, and it flows into the flotation separation section 21 in the form of floating particles. Therefore, suspended solids in the wastewater quickly rise and collect on the water surface, and collect on the water surface of the flotation separation section between the partition wall 17 and the partition wall 22. This aggregate of solid particles or flocs (FloC) that meets the water surface is called floating sludge. Now, the solid matter in the wastewater is separated between the partition wall 17 and the partition wall 22, and the purified water flows through the rectifying hole 22 drilled in the lower part of the partition wall 22.
It reaches the waterway 24 through the waterway 24, and from the waterway 24 there is an overflow tank (Overflow Tank) 25
be collected. The treated water overflows through the water channel 27 towards the inside of the annular overflow weir 28 and is discharged through the outlet pipe 31 of the treated water.

The purpose of the straightening holes 23 is to uniformly collect the treated water over the entire circumference of the partition wall 22 from the water flowing out from the coagulation reaction section, thereby preventing the occurrence of drift in the flotation separation section. For this reason, the number and diameter of the rectifying holes 23 are determined by the height of the water surface of the water channel 24.
It is designed to be 20 to 40 mra lower than the water surface height of the flotation separation section 21. Also, overflow tank (Ov
The erflow tank is installed for the purpose of adjusting the water surface height of the flotation separation section for the purpose of controlling the sludge concentration during floating sludge discharge using a spiral scoop (5piral 5coop), which will be described later. When the handle 29 is rotated, a screw-processed shaft 30 moves up and down, and although not shown, since this shaft 30 is connected to the overflow base 28, the height of the overflow base 28 also changes up and down. do. Therefore, the waterway 2Y, that is, the waterway 24
The height of the liquid surface in the flotation separation section 21 can also be adjusted through the rectification hole 23.

Now, the floating solids floating on the water surface in the flotation separation section, that is, the floating sludge, are removed by the spiral scoop (
5piral 5coop) It is scooped up from the water surface by 34. The spiral scoop has blades 35, and the cross section of the part with the blades is as shown in Figure 8, with a notch provided in a part of the pipe. (a) (b) (C) (d
) and scoop it up by rotating it in this order.

The pipe part of the spiral scoop is tilted 2 to 4 degrees, and the central part is low, so the floating sludge that is scooped out is
The sludge is lowered into the cylindrical sludge drop tank 36 in the center of the flotation separator,
It is discharged from the floating sludge discharge port 3.

In addition, spiral scoop (5piral 5coop
) not only rotates as shown by the arrows in Figures 6 and 8, but also revolves as shown by the arrows in Figure 7, and is structured to remove all of the floated sludge inside the flotation separator. . Some amount of sedimentable solids such as sand grains are mixed in the wastewater, and even in extremely small amounts, they settle at the bottom of the flotation tank. This sediment is raked up with a rake 38 shown in FIG.
is opened intermittently and discharged.

As explained above, according to the present invention, by setting the water depth of the flotation separation section of the pressure flotation device to 40 to 60 cIrL,
Compared to conventional flotation separation equipment, the installation area of V2 and 1
By installing an appropriate flocculation reaction section inside the flotation separator, it is possible to reduce the consumption of flocculant by 30 to 60%, and the quality of the treated water is also significantly improved. improves.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a conventional circular pressurized flotation device, showing the flow of water inside the flotation tank. FIGS. 2 and 3 are a sectional view and a plan view, respectively, of the circular caloric flotation separation apparatus of the present invention, illustrating the flow of water within the apparatus. FIG. 4 and FIG. 5 each show the shape of the aggregation reaction part of the present invention. FIGS. 6 and 7 are a cross-sectional view and a plan view of the circular pressurized flotation separator of the present invention, respectively, illustrating a method for discharging floated sludge and settled sludge. Figure 8 shows the Sunoku Iran scoop (5) for floating sludge cultivation.
FIG. 5 is a diagram illustrating a cross-section of a piral 5 coop and its function. Agent Patent Attorney Moritani-O Figure 1 Figure 2 Figure 3 Figure 5 Procedure amendment band (method) 1. Indication of the case Patent Application No. 57-200931 2. Name of the invention Pressurized flotation separation device , Relationship with the case of the person making the amendment Patent Applicant Nichols Co., Ltd. - Agent Address: 3-9-5 Nihonbashi Honmachi, Chuo-ku, Tokyo 103 February 22, 1981 (Shipping date) Subject of the amendment

Claims (1)

[Claims] 1. A pressurized flotation separator in which wastewater flows from the center toward the outer periphery, characterized in that the water depth of the flotation section is set in a range of 40 to 60 cm. . 2. The pressurized flotation separation device according to claim 1, which has a bypass type aggregation reaction section in the center. 3. Pressurized flotation according to claim 2, characterized in that the aggregation reaction section is composed of a plurality of annular waterways defined by a plurality of cylindrical partition walls (baffle plates) or an annular waterway with incisions. Separation device. 4. The pressurized flotation separation device according to claim 3, wherein an inlet is provided so that the wastewater flows tangentially into the annular waterway on the center side.