JPS60221200A - Belt press type dehydrator - Google Patents

Abstract

PURPOSE:To decrease remarkably the water content of dehydrated cake in a belt press type dehydrator consisting of a primary flocculation part, primary gravity dehydration part and compression dehydration part by providing a secondary flocculation part and secondary gravity dehydration part between the primary gravity dehydration part and the compression dehydration part. CONSTITUTION:The belt press type dehydrator is constituted of the primary flocculation part in which a flocculating agent is usually added into the unflocculated sludge, the primary gravity dehydration part in which the water in the primarily flocculated sludge is dehydrated by the own weight and the compression dehydration part in which the sludge after the primary gravity dehydration is pressed by the belts. The secondary flocculation part 4 in which the flocculating agent is again added to the sludge after the primary gravity dehydration and the secondary gravity dehydration part 6 in which the moisture in the secondarily flocculated sludge is again dehydrated by the own weight are provided between the primary gravity dehydration part 6 and the compression dehydration part consisting of an upper filter cloth belt 7 and a lower filter cloth belt 8.

Description

DETAILED DESCRIPTION OF THE INVENTION [1] Field of the Invention In the present invention, water-containing sludge is sandwiched between endless filter cloth belts, and the sludge is compressed by the tension of the filter cloth heald.

"2" Prior art and its problems In the belt press type dehydrator described above, a coagulant is added to prevent sludge from easily leaking from the belt holding the sludge and to speed up water removal from the sludge. However, since such flocculants are expensive, reducing the amount of coagulants mixed in to the necessary minimum has a great effect in reducing the operating cost of the dehydrator.

In addition, the sludge treated by these dehydrators is often disposed of after being incinerated, but in order to minimize the fuel cost for incineration, the moisture content of the dehydrated cake taken out from the dehydrator should be kept as low as possible. It is known that a slight decrease in water content significantly reduces the fuel consumption for incineration.

To do this, in general, a large amount of flocculant is mixed in, the amount of sludge supplied is set to a low level for safety, the running speed of the filter cloth belt is increased, and the thickness of the trapped sludge is made thinner than necessary. However, the moisture content of the dehydrated cake obtained with the addition rate of the flocculant has a relationship as shown in Figure 1, and adding a large amount of flocculant does not necessarily reduce the moisture content of the dehydrated cake. It is known that the relationship between the chemical injection rate and the moisture content of the dehydrated cake varies depending on the concentration of sludge solids and other sludge properties, as shown in the figure. It is being Therefore, adding an excessive amount of flocculant in consideration of safety not only increases the cost of the flocculant, but also deteriorates the moisture content of the dehydrated cake and increases the fuel consumption for incineration.

``3'' Purpose of the Invention Accordingly, the purpose of the present invention is to provide a device that can reduce the water content of a dehydrated cake with the same amount of flocculant used in a sludge flocculant in a conventional held press type dehydrator. It is.

``4'' Structure of the Invention In order to achieve the above-mentioned object, the present invention has a primary flocculation section that adds a flocculant to uncoagulated sludge, and a primary flocculation section that dewaters the water in the coagulated sludge by its own weight. In a heddle press type dewatering machine, the held press type dewatering machine has a press dewatering section that dewaters the sludge after gravity dehydration and after the second gravity dehydration by sandwiching the sludge between the healds and pressurizing the sludge, the second gravity dewatering section and the press dewatering section. A secondary flocculation section that adds a flocculant again to the sludge after the primary gravity dewatering, and a secondary gravity dewatering section that dehydrates the water in the secondary flocculated sludge again by its own weight are provided between the sludge and the sludge. This is a summary.

``5'' Embodiment Next, an embodiment embodying the present invention will be described with reference to the attached drawings to provide an understanding of the present invention.

Here, FIGS. 2, 3, and 4 are schematic side views of held press type dehydrators in the first, second, and third embodiments of the present invention, and FIG. 5 is a schematic side view of the held press type dehydrator used in the above embodiments. 6 and 7 are side views and side sectional views of the stirring tank, Figure 8 is a partial front view of the stirring shaft that can be used in the stirring tank, and Figure 9 is a partial front view of the stirring shaft that can be used in the stirring tank. Side view of the same stirring shaft, 1st
Figure 0 is a partial front view of an injection trough that can be used in the stirring tank.

In FIG. 2, the dehydrator 1 is roughly constituted by a coagulation tank 2 as a primary coagulation section, a secondary filter cloth belt device W3, a secondary coagulation section 4, and a secondary filter cloth belt device 5.

The primary filter cloth helt device 3 is composed of a relatively thin endless filter cloth heald, and has a primary gravity dewatering device 6 in part that dewaters the supplied primary flocculated sludge containing a large amount of water by its own weight. . Further, the secondary filter held device 5 includes a relatively thin endless upper filter cloth belt 7 suitable for gravity dehydration,
The sludge sandwiched between both healds 7 and 8 is compressed and dehydrated by passing through the outer periphery of a large number of rollers in a state in which a strong thick endless lower filter cloth heald 8 is overlapped. A secondary gravity dewatering section 9 is formed on the upper filter cloth belt 7 for subjecting the sludge discharged from the filter cloth belt device 3 to gravity dewatering again.

The pair of filter cloth healds 7 and 8 are overlapped as they pass through the confluence section 10 and travel in the direction of arrow 11i, and drive roller 11. It passes through the squeeze rollers 12a and 1.12h and reaches the high-pressure dewatering section 13, where it is strongly squeezed, and then passes over the circumference of the squeeze roller 121 and is separated by the separation roller 14, after which it is passed through the lower filter. The cloth belt 8 has an intermediate roller 15
□, 15b, 15- to return to the merging section 1.0, and the upper wave cloth heald 7 passes through intermediate rollers 16a, 161.
.

16, and then returns to the merging section 10.

The structure of the high-pressure dewatering section 13 is already well known, and includes upper and lower filter cloth healds 7.8 which are overlapped, and a steel mesh heald 17.
It has a structure that can be pressed to strengthen the pressing force against the pressing roller 18.

Unagglomerated sludge is introduced into the flocculation tank 2 through a pipe 19, and a flocculant is introduced through a piping 20. The flocculant and sludge are mixed by a stirrer 21 driven by a motor M, and a flocculation reaction proceeds. The flocculated sludge, in which the flocculation reaction has proceeded in this way, is supplied to the upper filter cloth belt 7 in fixed quantities through the sludge feeder 22, which constitutes a kind of hopper, and is then fed to the upper filter cloth belt 7 in fixed quantities. , -徨～1-线力1ii17L passes through the draw 6, at which time a considerable amount of water is dehydrated.

Normally, unflocculated sludge is sludge-like sludge with a solids concentration of 2 to 4%, but when primary gravity dewatering of flocculated sludge, in which a polymer flocculant has been added to promote the flocculation reaction, solids concentration is is improved to about 7-10%.

A flocculant is injected into the sludge which has been subjected to gravity dewatering in this manner by the secondary flocculating section 4 at the end of the primary gravity dewatering section 6. The secondary flocculation section 4 is usually constituted by a gutter-like trough with many notched grooves formed on the side surface, and the flocculant supplied to this trough is transferred from the notched grooves to the primary filter cloth helt device 3 by the primary gravity. It is dripped and injected into the dewatered sludge. The structure of such a trough is similar to the injection trough shown in FIG. In this way, the flocculant dripped from the secondary flocculation section 4 penetrates into the sludge that has been subjected to gravity dewatering.
In this part, the flocculation reaction takes place again, and the free water in the sludge is separated. The separated free water is dehydrated by its own weight in the subsequent secondary gravity dehydration section. At this time, as a matter of course, water contained in the flocculant injected from the secondary coagulation section 4 is also dehydrated in the secondary gravity dehydration section 9.

Generally, the moisture content of the dehydrated cake relative to the addition rate of the flocculant is:
As shown in FIG. 1, it depends on the sludge concentration before adding the flocculant. For example, as shown in FIG. 1, when the addition rate of flocculant is the same, the moisture content of the commercial dehydrated cake decreases within a certain range of sludge concentration. Figure 1 shows cases where the sludge concentration is 2% and 3%.
The case of adding flocculant to sludge with a solids concentration of 3% is better than the case of adding the same amount of flocculant to sludge with a solids concentration of 2%. More efficient dehydration. The re-addition of the flocculant in the secondary flocculant section 4 shown in Fig. 2 above is based on this perspective, and the flocculant is added again to the sludge whose solid content concentration has been improved by gravity dewatering. This is intended to further reduce the moisture content of the dehydrated cake. Therefore, in the present invention, the addition rate of the flocculant injected into the flocculating tank 2 is generally lower than the conventional case in which the flocculant is injected only once, and in short, it is sufficient to appropriately promote gravity dewatering in the primary gravity dewatering section 6. It is sufficient if the addition rate is as follows.

In this way, the sludge that has been subjected to gravity dewatering for the second time in the secondary gravity dewatering section 9 is conveyed to the upper filter cloth heald 7 which is reversed through the outer periphery of the intermediate roller 16c, falls onto the lower filter cloth heald 8, and joins the sludge. In section 10, upper and lower filter cloth healds 7 and 8
The driving roller 11 and the pressing roller 128 are sandwiched between
to 12. The filter fabric passes through the outer periphery of the rollers, and is compressed by the tension of the filter cloth belt pressed against the outer peripheral surface of each roller, thereby performing compression dewatering. The sludge sandwiched between the two cloth belts 7 and 8 is further strongly squeezed and dewatered by passing through the high-pressure dewatering section 13. In the high-pressure dewatering section 13, a squeezing force of 2 kg/cd or more is applied to the sludge, and the sludge squeezed to the limit passes through the intermediate roller 12L and is separated by the separation roller 14 between the upper and lower filter cloth healds 7 and 8. A dehydrated cake 23 is released from between. After releasing the dehydrated cake, the lower filter cloth heald 8 passes through the intermediate rollers 15a, 15b, and 15c to the confluence section 12 as described above.
The upper filter cloth belt 7 passes through the intermediate rollers 16° and 16 and returns to the secondary dewatering section 9. In the belt press type dehydrator that performs secondary flocculation as described above, the water contained in the secondary flocculant must be dehydrated by gravity prior to compression dehydration, so the secondary flocculant is added at the primary After completion of gravity dehydration, it is limited to the part where gravity dehydration is possible until the start of compression dehydration. Therefore, it is appropriate to add the secondary flocculant at the end of the primary gravity dewatering section 6 as shown in FIG. However, in this device, the effect of adding a secondary flocculant cannot be fully exhibited in the following two points.

One point is that when a secondary flocculant is simply dropped onto the sludge on a filter cloth heald that can be gravity dewatered as shown in Figure 2,
The secondary flocculant and sludge are not sufficiently mixed, and there are parts of the sludge that cannot mix and react with the secondary flocculant, resulting in partial agglomerates. In order to eliminate this inconvenience, if the amount of flocculant added from the secondary flocculation section 4 is increased, the flocculant will spread to every corner of the sludge and the flocculation reaction bed will be considerably resolved, but the reaction lumps will be eliminated. If too much flocculant is added, the addition of excessive flocculant may actually reduce the dewatering rate, cause sludge to overflow from the sides of the filter belt, and cause so-called re-leakage. An increase in the amount of coagulant injected results in extremely uneconomical operation.Secondly, the addition of the secondary coagulant is carried out on a thin filter cloth heald that can be dewatered by gravity. Even if a flocculant is added, some or most of the flocculant does not react with the sludge and is dehydrated by gravity from the filter belt, so that the effect of the flocculant addition is not fully exhibited.

In view of this, it is also conceivable to provide a mechanism that plows back the sludge immediately after adding the secondary flocculant to promote mixing of the secondary flocculant and sludge. Such a sludge plowing mechanism can use, for example, a baffle plate described in Japanese Patent Application Laid-Open No. 58-125398. However, even when such a plowing mechanism is used, it is difficult to completely stir the secondary flocculant and sludge, and some unreacted secondary flocculant is dehydrated by gravity from the filter cloth belt. It is also difficult to avoid this.

An embodiment improved in this respect is shown in FIG. In this case, a stirring tank 42 as an embodiment of the secondary coagulation part is provided between the secondary gravity dewatering section 6 and the secondary gravity dewatering section 9, and the sludge subjected to the gravity dewatering is transferred to the stirring tank 41. The flocculated sludge is mixed and stirred with the secondary flocculant that is injected again, and the flocculated sludge that has undergone the flocculation reaction again is supplied to the secondary gravity dewatering section 9 of the upper filter cloth heald 7.

Since such a stirring tank 4a is used to stir highly viscous sludge that has already been subjected to primary heavy dewatering and has an increased solid content concentration, it is necessary to have a special structure to prevent fibers such as hair from becoming entangled. , such examples are shown in Figures 5 to 1.
It is shown in Figure 0.

That is, as shown in FIGS. 5 and 7, the stirring tank 41 has one or more horizontal stirring shafts 25 rotatably attached to the stirring tank main body 24 having a substantially semicircular side cross-sectional shape. is rotationally driven by a hydraulic motor 26,
The stirring tank main body 24 has a sludge outlet 27 formed on one side thereof, and is fixed to a horizontal shaft 28 provided in the width direction of the belt.

This horizontal shaft 28 is rotatably attached to a frame 29. The angle of inclination of the handle 30 fixed to the horizontal shaft 28 can be set appropriately using a plurality of positioning holes 32 formed in a positioning plate 31 fixed to the frame 29. The entirety of the sludge 24 is fixed to the frame 29 while being tilted at a certain angle, and the amount of sludge stored in the stirring tank 48, that is, the sludge stirring time can be adjusted. An injection trough 33 is provided in the upper part of the stirring tank body 24 in the width direction of the belt, and this injection trough 33 has a pipe shape as shown in FIG. 10, and a plurality of notches 34 are carved in the upper part. The flocculant flowing from the population 35 of the injection trough 33 flows into the notched groove 3.
4 overflows little by little and drips almost evenly over the entire width of the stirring tank main body 24.

The stirring shaft 25 has an outer diameter of 100 mm as shown in FIG.
It is larger than U, and has a plurality of mountain-like protrusions 36 on its outer periphery as shown in FIGS. 8 and 9, and the tip is rounded into a spherical shape with the length larger than this dragon. The fibers in the sludge contain many hairs, and such hairs do not get entangled with the agitation shaft 25 and the above-mentioned ridge protrusion 36, and even if they do get entangled, they quickly come off, and the highly viscous sludge is stirred. The outer diameter of the stirring shaft 25 and the dimensions and shape of the mountain-like projections 36 are determined so as to have sufficient rigidity. Although it is conceivable that only one stirring shaft 25 as described above is provided in the stirring tank body 24, it is preferable to improve the stirring effect by providing two or more, and in that case, the rotation direction of each stirring shaft is It is desirable that the rotation speed can be set in the same direction or in different directions depending on the properties of the sludge, and it is also desirable that the rotation speed can be changed in accordance with the properties of the sludge.

Further, a chute 37 parallel to the injection trough 33 is provided in the upper part of the stirring tank main body 24, so that the sludge scraped off from the filter cloth belt device 3 by the scraper 38 is quickly introduced into the stirring tank main body 24. It is desirable to configure the

In such a stirring tank 41, the sludge scraped off by the scraper 38 as described above is supplied into the stirring tank main body 24 through the chute 37. Further, the flocculant supplied into the injection trough 33 is dripped from the notch groove 34 over the entire width of the stirring tank main body 24.
It is injected into the sludge inside. Uniform mixing of the injected flocculant and sludge is achieved by the stirring action of the stirring shaft 25 rotationally driven by the hydraulic motor 26 and the protrusion 36 attached thereto, and by adding a small amount of flocculant, the entire sludge is cause a uniform aggregation reaction. The flocculated sludge in which the flocculation reaction has progressed and liberated free water is supplied from the sludge outlet 27 to the secondary gravity dewatering section 9 on the filter cloth heald 7, where gravity dewatering of the liberated free water is performed.

In the belt press type dehydrator as shown in FIG. 3 having the above-mentioned secondary filter cloth belt and secondary cloth belt device, the stirring tank forming the secondary agglomeration section as described above is the secondary gravity dewatering section 6.
However, in a belt press type dehydrator as shown in FIG. 4 which does not have such a filter cloth belt device, the secondary gravity dewatering section 6 □ and
A stirring tank 4I that can temporarily store the sludge discharged from the primary gravity dewatering section 61 at an intermediate point between the confluence section 10 and the confluence section 10, mix and stir the sludge, and then supply the sludge to the confluence section 10.

can be provided. In this case, since it is necessary to perform secondary gravity dehydration at the confluence section 10a, it is desirable that the length l of the confluence section 10a be relatively long. Also, regarding the stirring tanks 4 shown in FIG. 4 above, the stirring tanks 4 shown in FIG.
It has the same configuration as @, and by tilting the stirring tank main body 24 using the handle 30, the residence time of sludge in the stirring tank main body 24 can be set appropriately, and the stirring time can be adjusted. . This makes it possible to obtain optimal aggregation conditions.

In any of the above examples, the type of flocculant added in the primary flocculation section and the type of flocculant added in the secondary flocculation zone can be the same or different. be. When using the same type of flocculant,
As shown in FIG. 3, it is possible to branch the flocculant addition pipe 20 and use it for primary and secondary flocculation. Such flocculants can be polymer flocculants, inorganic ferric chloride, slaked lime, incinerated ash, etc. Polymer flocculants are used as the primary flocculant, and secondary flocculants are used as the secondary flocculant. It is also conceivable to use other flocculants as a coagulant, and vice versa.

``6'' Experimental Examples Table 1 shows experimental examples using the belt press type dehydrator shown in FIG. 3 and the conventional belt press type dehydrator using only primary agglomeration.

The dewatering conditions in this case are that mixed raw sludge is used as the target sludge, TS = 3.8%, VTS = 77.7%, and the filtration rate is 1.
20 kg-DS/m-h. In addition, the addition rate of the coagulant to be injected is 1% (relative to DS) in the case of conventional equipment, and in the equipment of the present invention, it is 1% in total in the first and second stages, and in the coagulation tank 2, 43% of it was injected into the stirring tank 411 days and '-'r which is the secondary agglomeration part.
As is clear from Table 1, compared to the moisture content of the dehydrated cake in the conventional device, the moisture content in the device of the present invention is approximately 1.5 to 2% lower, indicating a significant decrease in the moisture content. I can understand. The difference in the amount of heavy oil used for incineration due to such a decrease in moisture content is significant. For example, when a dehydrated cake whose lower calorific value of the cake solid is 3000 Kcal/kf-DS is incinerated in a fluidized bed incinerator, the amount of heavy oil used While the cake moisture content was 72% and 18ff/l,
When the water content reaches 70%, it becomes 8 Il/l, and by reducing the cake water content by 2%, 10 n of heavy oil is saved per 1 ton of dehydrated cake.

Furthermore, as is clear from Table 1, as the maximum compression pressure by the high-pressure dehydration section 13 increases, the moisture content of the dehydrated cake decreases.
In the case of the present invention, it is possible to use a lower maximum pressing pressure than in the conventional apparatus to obtain the same cake moisture content. For example, in order to make the moisture content of the cake about 67%, a maximum compression pressure of 8 kg/c+a is required in the case of a conventional device, whereas 5 kHz/c-a is sufficient in the present invention. By lowering the maximum squeezing pressure in this way, the structure of the high-pressure dewatering section can be simplified, and there is no need to increase the rigidity so much, so it is possible to reduce the weight of the equipment and equipment costs.

"7" Effects of the present invention As described above, the present invention has a primary coagulation section that adds a coagulant to uncoagulated sludge, and a primary gravity dewatering section that dewaters water in the coagulated sludge by its own weight. In the heald press type dewatering machine, the held press type dewatering machine includes a press dewatering section that dewaters the sludge after the above-mentioned gravity dewatering by sandwiching it between healds and pressurizing it, in which the above-mentioned sub-gravitational dewatering section and the press dewatering section are combined. In between, a secondary coagulation section is provided in which a flocculant is added again to the sludge after the primary gravity dewatering, and a secondary gravity dewatering section is provided in which water in the secondary coagulated sludge is dehydrated again by its own weight. Since it is a belt press type dehydrator, when the addition rate of flocculant and the maximum pressing pressure are kept the same, the water content of the dehydrated cake can be dramatically lowered compared to conventional equipment.
The fuel consumption required for incineration of the dehydrated cake can be significantly reduced. In addition, the above effects can be achieved without increasing the addition rate of the flocculant, so the cost required for the flocculant can be minimized, side leaks can be prevented, and continuous operation can be achieved through automation. .

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the flocculant addition rate and the water content of the dehydrated cake, and FIGS. A schematic side view of the held press type dehydrator in the second and third embodiments, FIG. 5 is a front view of a stirring tank that can be used in the above embodiments, and FIGS. 6 and 7 are side views of the same stirring tank. and a side sectional view, FIG. 8 is a partial front view of a stirring shaft that can be used in the stirring tank, FIG. 9 is a side view of the stirring shaft, and FIG. 10 is an injection trough that can be used in the stirring tank. FIG. (Explanation of symbols) 1...Dehydrator 2...-Secondary agglomeration tank 3...-Secondary filter cloth belt device 4.4a+ 4b...Secondary agglomeration section 5...Secondary filter cloth belt device 6... -Next gravity dewatering section 7... Upper filter cloth heald 8... Lower filter cloth heald 9.
...Secondary gravity dehydration section 13...High pressure dehydration section 24...Stirring tank body 25...
- Stirring shaft 27...Sludge outlet 28...Horizontal shaft 3
0... Handle 31... Positioning plate 33... Injection trough 34... Notch groove 34... Yamabushi projection. Applicant: Kobe Steel Corporation, Masataka, Agent, Patent Attorney: Takeo Honjo, Procedural Author: May 22nd, 1985 2, Name of Invention: Heald Breath Dehydrator 3, Relationship to the Amendment Case Patent Applicant Address: 1-3-1 Wakihama-cho, Chuo-ku, City 651?111
No. 8 Name (119) Co., Ltd.? Shinto Seitaokasho Representatives: 14 each, 4 agents, Address: 6, Tominaga Building, 2-3-36 Minamimorimachi, Kita-ku, Osaka, Japan.
Target of amendment “Column for detailed description of the invention in the specification” 7. Contents of amendment 1: “Re-leak” in the second to third lines of page 11 of the specification is corrected to “side leak” do.

Claims (1)

[Claims] (1) A primary flocculation section that adds a flocculant to uncoagulated sludge;
- A belt comprising a primary gravity dewatering section that dewaters water in the coagulated sludge by its own weight, and a press dewatering section that dewaters the sludge after the secondary gravity dewatering by sandwiching it between the belts and pressurizing it. In a press-type dehydrator, there is a secondary coagulation section between the secondary gravity dewatering section and the compression dewatering section that adds a coagulant again to the sludge after the primary gravity dewatering, and a secondary coagulation section that adds a flocculant again to the sludge after the primary gravity dewatering, and a secondary coagulation section that re-adds the coagulant to the sludge after the primary gravity dewatering. A held press type dewatering machine characterized by being equipped with a secondary gravity dewatering section that dewaters by its own weight.