JP2540180B2 - Sludge dewatering method and apparatus using decanter type centrifuge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention uses a decanter-type centrifuge to
The present invention relates to a sludge dewatering method and device for more efficiently dehydrating various sludges generated in human waste and industrial wastewater treatment processes.

[Conventional technology]

Generally, a decanter-type centrifuge has been used for concentrating and dewatering various sludges generated in sewage, human waste, industrial wastewater treatment process and the like.

As shown in FIG. 4, the decanter centrifuge described above includes a rotating cylinder 1 that is supported by bearings 2 and 2 and rotates at a high speed, an inner cylinder 5 that rotates in the same direction as the rotating cylinder 1, and A screw conveyor composed of screw blades 6 is provided concentrically, and a sludge supply pipe 11 is arranged at the center of the rotating shaft.

The rotating cylinder 1 and the inner cylinder 5 are provided with a required rotation difference by the differential gear 7, and the screw conveyor conveys the concentrated sludge 19 toward the settling sludge discharge port 3. Further, the rotary cylinder 1 is composed of a conical portion 1a and a cylindrical portion 1b, and at the end of the conical portion 1a, a settled sludge discharge port for discharging concentrated dehydrated sludge conveyed through a dry beach section 17 by a screw conveyor. 3 is provided, and a dam 4 for discharging the separated separation liquid 18 is provided at the end of the cylindrical portion 1b on the opposite side.

In the decanter type centrifugal separator having the above-mentioned configuration, the sludge supplied to the sludge supply unit 8 in the separator inner cylinder 5 through the sludge supply pipe 11 passes through the sludge discharge nozzle 14 provided on the cylindrical wall and is adjacent to the conical portion 1a. The sludge is discharged to the pool inside the portion 1b, and subjected to the centrifugal action of the rotating cylinder 1 rotating at a high speed to be separated into the settled sludge and the separated liquid, and the settled sludge discharge port 3 and the dam 4 respectively.
And is discharged from the machine.

When dewatering sludge with a decanter type centrifuge
A method of adding a polymer coagulant or the like to the supplied sludge and conditioning the sludge by a method as shown in FIGS. (A), (b) and (c) is generally used. The sludge added with the coagulant using one of these sludge refining methods forms a floc and is separated into a separated liquid 18 and a concentrated sludge 19 by the centrifugal force generated by the high speed rotation of the rotary cylinder 1. The concentrated sludge 19 is conveyed by a screw conveyor composed of the inner cylinder 5 and the screw blades 6 and discharged to the outside of the rotary cylinder 1, and the separated liquid 18 flows down along the screw blades 6 and from the dam 4 to the rotary cylinder 1.
Is discharged to the outside.

Among the conventional sludge refining methods shown in FIGS. 5 (a), (b) and (c), those shown in (a) and (b) of FIG.
In each case, one kind of polymer coagulant is added to the supply sludge to condition the sludge, and (a) is an example of supplying sludge previously conditioned with the polymer coagulant to a centrifuge, (b) ) Shows an example in which the sludge and the polymer coagulant are separately supplied into the centrifuge, and the polymer coagulant is added to the sludge in the region between the rotating cylinder and the inner cylinder of the separator. In addition, (b) is Japanese Patent Publication No. 52-1626
This is described in detail in Japanese Patent Publication No. 8.

The example shown in FIG. 5 (c) is one in which two types of flocculants are added to sludge.
In 87500 and JP-A-57-32797, an example of adding two kinds of polymer flocculants is disclosed as a similar technique.
JP-A-257256 discloses an example in which one kind of polymer coagulant and one kind of inorganic coagulant are added together.

[Problems to be solved by the invention]

In recent years, with the development of the decanter type centrifuge, sludge can be concentrated without adding a coagulant.
However, if the sludge is not conditioned by the coagulant, the recovery rate of the substances suspended in the supplied sludge is only about 90 (%). Therefore, as described with reference to FIGS. 5 (a), (b), and (c), when dewatering sludge with a decanter-type centrifuge, sedimentation / consolidation / dehydration of sludge by centrifugal force inside the centrifuge rotary cylinder is performed. For the purpose of promoting the action, a coagulant is added to condition the sludge.In this case, regardless of whether the coagulant is one kind or two kinds, the coagulant is settled / consolidated, It is added to the sludge supply for the purpose of collectively promoting the dehydration action, and it is considered that separation and concentration in the centrifuge rotating cylinder to sedimentation / consolidation and subsequent dehydration are performed separately. However, these conventional methods have the following problems.

That is, in the example shown in FIGS. 5 (a) and 5 (b), since it is a refining method in which one type of polymer flocculant is added to sludge, it has the advantages of low cost and easy handling, There is a drawback that the water content of the settled sludge discharged to is high and the cost required for post-treatment processes such as disposal, landfill, drying, incineration, etc. is relatively high.

Further, the sludge refining method of adding two kinds of coagulants as shown in FIG. 5 (c) is more effective than the sludge refining method of FIGS. 5 (a) and (b) in the sediment discharged from the rotary cylinder. Although it has the effect of reducing the water content of sludge, it uses two types of coagulant, so it is necessary to install separate coagulant supply equipment for supplying each coagulant to the decanter centrifuge. Therefore, there is a drawback that not only the construction cost of the entire equipment becomes high, but also the operating cost becomes high because the amount of the flocculant used increases. Further, the technique disclosed in the above-mentioned JP-A-57-32797 uses acetic acid or hydrochloric acid to dissolve a natural polymer flocculant.
Since the technology disclosed in the publication uses iron sulfate, there are problems such as corrosion of the equipment by strong acid and caution in handling, etc., and the water content of the sludge settles down, Although it has the effect of reducing the treatment and disposal costs of, it is not widely used.

The present invention is intended to solve the problems in the sludge dewatering technique described above.

[Means for solving the problem]

The present invention has been made to solve the problems in the conventional sludge dewatering technique as shown in Figs. 5 (a), (b) and (c). The sludge dewatering method according to the present invention is a cone Using a decanter type centrifuge equipped with a rotary cylinder composed of a cylindrical part and a cylindrical part, and a screw conveyor composed of an inner cylinder and screw blades concentrically arranged in the rotary cylinder, in operating the centrifugal separator. , Supplying the sludge to be dehydrated, and supplying the required amount of one kind of coagulant for promoting the separation / concentration / dehydration action of the supplied sludge into the centrifuge, A method for dewatering sludge in which dewatered concentrated sludge is discharged from a discharge port of a part, which is 10 (%) to 40% of the required total amount of the coagulant.
(%) Amount is supplied to the inner region of the cylindrical portion adjacent to the rotating cylinder cone portion, and the remaining 90 (%) to 60 (%) amount is supplied to the inner region of the rotating cylinder cone portion. is there.

Further, the sludge dewatering device according to the present invention includes a rotary cylinder composed of a conical portion and a cylindrical portion, an inner cylinder concentrically disposed in the rotary cylinder and driven at a rotational differential speed with the rotary cylinder, and A screw conveyor consisting of screw blades fixed to the inner cylinder, and a sludge supply pipe arranged at the center of the inner cylinder,
In the decanter centrifuge configured to discharge the concentrated sludge from the outlet of the rotary cylinder conical end, and to discharge the separated liquid from the rotary cylinder cylindrical end, a juxtaposed to the sludge supply pipe. A first coagulant supply pipe for supplying a coagulant to the inner region of the cylindrical portion adjacent to the conical portion of the rotating cylinder and a second coagulant supply pipe for supplying a coagulant to the inner region of the conical portion of the rotating cylinder. It is characterized by that.

[Action and effect]

In the present invention, 10 (%) to 40 (%) of the required total amount of one kind of coagulant is supplied to the inner region of the cylindrical portion of the decanter centrifuge which is adjacent to the conical portion of the rotating cylinder, and the remaining 90 ( %) To 60 (%) is supplied to the inner region of the conical portion of the rotating cylinder, so that the separation / concentration action is promoted by the coagulant in the inner region of the cylindrical portion, and the dehydration is performed by the coagulant in the inner region of the conical portion. The action is promoted, and compared with the conventional dehydration technology in which the required amount of one type of coagulant is added all at once, the facility construction cost and operation cost are almost the same, but it is discharged to the outside of the rotating cylinder. It was possible to keep the water content of the settled sludge to be 2 (%) to 3 (%) low.

〔Example〕

Next, the embodiment of the present invention shown in FIGS. 1, 2 and 3 (a), (b) will be described.

The decanter type centrifugal separator used in the present invention shown in FIG. 1 is basically the same as that shown in FIG.
And a rotary cylinder 1 which is supported by the rotary cylinder 1 and rotates at high speed.
The rotary cylinder 1 is provided with a rotary cylinder 1 driven by a differential gear 7 at a differential rotation speed, a concentric inner cylinder 5 and a screw conveyor composed of screw blades 6 fixed to the inner cylinder 5.
Comprises a conical portion 1a and a cylindrical portion 1b which are integrally connected to each other, a discharge port 3 for discharging settling sludge at the end of the conical portion 1a, and a separation liquid at the end of the cylindrical portion 1b. A dam 4 for discharging is provided.

The inside of the inner cylinder 5 is divided into a sludge supply unit 8, a separation / concentration coagulant supply unit 9 and a dehydration coagulant supply unit 10, and at the center of the inner cylinder 5, a sludge supply pipe 11 is provided. A concentration coagulant supply pipe 12 and a dehydration coagulant supply pipe 13 are provided.

Sludge supplied to the operating decanter centrifuge through the sludge supply pipe 11 enters the sludge supply unit 8 through the end opening 11a of the supply pipe 11, and the sludge discharge nozzle 14 provided on the cylinder wall of the inner cylinder 5 Is introduced into the cylindrical portion 1b of the rotary cylinder 1 and is subjected to the separation / concentration action by the centrifugal separator.

Similarly, the coagulant supplied through the separation / concentration coagulant supply pipe 12 enters the separation / concentration coagulant supply unit 9 from the end opening 12a of the supply pipe, and is separated on the cylinder wall of the inner cylinder 5.・
It is introduced into the cylindrical portion 1b adjacent to the conical portion 1a through the condensing agent discharge nozzle 15 for concentration, promotes the sedimentation / consolidation action of the sludge supplied by the centrifugal separator, and is further supplied through the coagulant supply pipe 13 for dehydration. The agent enters the dehydration coagulant supply unit 10 through the end opening 13a of the supply pipe and is introduced into the conical portion 1a of the rotary cylinder 1 through the dehydration coagulant discharge nozzle 16 provided on the cylinder wall of the inner cylinder 5, Accelerating the dehydration action of concentrated sludge by the centrifuge.

The sludge supply pipe 11, the separation / concentration coagulant supply pipe 12 and the dewatering coagulant supply pipe 13, which are arranged in the center of the inner cylinder 5 of the centrifuge, are as shown in FIGS. 1 and 2. Although it may be configured as a triple tube, it may be configured as a multiple tube as shown in each of FIGS. 3 (a) and 3 (b).

The sludge dewatering method according to the embodiment of the present invention using the decanter type centrifugal separator as described above is carried out as follows. First, the sludge discharged from the end opening 11a of the sludge supply pipe 11 is rotationally accelerated by the sludge supply unit 8, and the sludge discharge nozzle 14
Is supplied to the inside of the cylindrical portion 1b of the rotary cylinder 1 from the separation / concentration coagulant discharge nozzle 15 provided near the sludge discharge nozzle 14, and is 10% to 40% of the total amount used, typically Is 20
(%) Mixed with the supplied flocculant to form the flocs necessary for separation.

The sludge forming the flocs is separated by the centrifugal force and settles on the inner wall of the rotary cylinder 1. The water separated from the sludge flows down inside the rotary cylinder 1, and is discharged as a separated liquid from the dam 4 at the end of the cylindrical portion 1b. The sludge that has settled is conveyed to the settling sludge discharge port 3 side while being concentrated by a screw conveyor. Since the concentrated sludge that has been transported still has fluidity, it causes a slip phenomenon due to centrifugal force at the beach portion in the conical portion 1a of the rotating cylinder, and is vigorously stirred by the transport force and the slip component force of the screw conveyor. In this way, the remaining coagulant is supplied from the dewatering coagulant discharge nozzle 16 to the agitated portion of sludge in an amount of 90 (%) to 60 (%) of the total amount used, typically 80 (%). Therefore, the dehydration action of concentrated sludge will be further promoted.

As a comparative example, the examples shown in FIGS. 5 (a), 5 (b) and 5 (c) are used to carry out the present invention in which a polymer coagulant is dispensed in two parts, a cylindrical part and a conical part of a decanter centrifuge. Comparing with the example, the addition rate of each polymer flocculant and the water content of the discharged settled sludge are as shown in the following table.

The addition amount of the polymer flocculant is the weight (%) with respect to the dry solid (absolutely dry solid) DS.

Experiment target sludge …… Sewage digestion sludge Experimental machine …… Decanter type centrifuge Rotating cylinder inner diameter 356mm Experimental machine Centrifugal effect …… 2,100G Screw conveyor rotation differential speed …… 5rpm Supplied sludge volume …… 4m ³ / h From the above table As you can see, if no coagulant is added,
While the sludge recovery rate is usually 50 (%) to 90 (%), by adding a polymer flocculant, in the comparative examples (a), (b), (c) and in the examples, sludge is obtained. The recovery rate is high at 98%, and there is no significant difference in sludge recovery rate between the comparative example and the example. However, as can be seen from the comparison between the comparative examples (a) and (b) in which one kind of polymer flocculant is added and the examples of the present invention, the water content of discharged sedimentation sludge is 2.4 according to the present invention.
(%) To 2.6 (%) are also low values, and considering that lowering the water content of this type of sludge by 1 (%) has a great influence on the subsequent treatment of sedimented sludge, the water content of the sludge according to the present invention. It should be said that the effect of reducing the above is remarkable.

In the comparison between the example of the present invention and the comparative example (c), there is no great difference in the sludge recovery rate and the discharged sludge water content. However, the comparative example (c) requires equipment for separately supplying two types of high-core coagulant, so that not only the construction cost of the sludge dewatering apparatus as a whole increases, but also the use of the polymer coagulant is used. The amount is 2.5 times that of the embodiment of the present invention, and the operating cost is high. Therefore, according to the present invention, a significant reduction in construction cost and operating cost can be expected compared to the comparative example (c).

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of a sludge dewatering apparatus using a decanter type centrifugal separator for carrying out the sludge dewatering method of the present invention, and FIG. 2 is a sludge taken along the line AA of FIG. A cross-sectional view of a triple pipe consisting of a supply pipe, a separation / concentration flocculant supply pipe, and a dehydration flocculant supply pipe, and FIGS. 3 (a) and 3 (b) are sludge supply pipes different from FIG. A sectional view of a collecting pipe comprising a flocculating agent supply pipe for concentration and a flocculating agent supply pipe for dehydration, Fig. 4 is a side sectional view of a decanter type centrifuge, and Figs. 5 (a) and 5 (b).
(C) is explanatory drawing of the conventional sludge conditioning method. 1 ... Rotary cylinder 2 ... Bearing 3 ... Settled sludge discharge port 4 ... Dam 5 ... Inner cylinder 6 ... Screw blade 7 ... Differential machine 8 ... Sludge supply unit 9 ... Coagulant for separation / concentration Supply unit 10 …… Dehydration coagulant supply unit 11 …… Sludge supply pipe 12 …… Separation / concentration coagulant supply pipe 13 …… Dehydration coagulant supply pipe 14 …… Sludge discharge nozzle 15 …… Separation and concentration Flocculant discharge nozzle 16 …… Drainage flocculant discharge nozzle 17 …… Dry beach

Claims (4)

(57) [Claims] 1. A decanter-type centrifuge equipped with a rotary cylinder composed of a conical part and a cylindrical part, and a screw conveyor composed of an inner cylinder and screw blades concentrically arranged in the rotary cylinder. When operating the centrifuge, while supplying the sludge to be dehydrated, separation and
The amount of one type of coagulant required to accelerate the concentration / dehydration action is supplied into the centrifuge, and the dehydrated concentrated sludge is discharged from the discharge port at the end of the rotating cylinder cone. A dehydration method, wherein 10 (%) to 40 (%) of the required total amount of the coagulant is supplied to the inner region of the cylindrical portion adjacent to the conical portion of the rotating cylinder, and the remaining 90 (%) to 60 (%) ) A method of dewatering sludge using a decanter centrifuge, characterized in that the amount is supplied to the inner region of the conical portion of the rotating cylinder. 2. The coagulant is a polymer coagulant, and the polymer coagulant is provided in an amount of 20 (%) of the total amount required for the inner region of the cylindrical portion adjacent to the conical portion of the rotary cylinder, and the rotary cylinder. The method for dewatering sludge using a decanter-type centrifuge according to claim 1, wherein the remaining 80 (%) amount is supplied to the area inside the conical portion. 3. A rotary cylinder comprising a conical portion and a cylindrical pinion, an inner cylinder concentrically arranged in the rotary cylinder and driven at a rotational differential speed with the rotary cylinder, and a screw fixed to the inner cylinder. A screw conveyor composed of blades and a sludge supply pipe arranged in the center of the inner cylinder are provided, concentrated sludge is discharged from an outlet at the end of the conical portion of the rotary cylinder, and a dam at the end of the rotary cylinder. A decanter-type centrifuge configured to discharge more separated liquid, wherein a first coagulant supply pipe for arranging the sludge supply pipe in parallel and for supplying a coagulant to an inner region of a cylindrical portion adjacent to the rotating cylinder conical portion And a second coagulant supply pipe for supplying a coagulant to the inner region of the conical portion of the rotating cylinder. 4. The inside of the rotary cylinder is divided into a sludge supply unit, a separation / concentration coagulant supply unit, and a dehydration coagulant supply unit from the rotary cylinder cylindrical portion side to the conical portion side, and the sludge supply pipe. The sludge supplied from is supplied to the inner region of the rotating cylinder through the sludge supply nozzle and a sludge discharge nozzle provided in the inner cylinder.
The coagulant supplied from the first coagulant supply pipe is
It is supplied to the inner region of the cylindrical portion adjacent to the conical portion of the rotating cylinder via the coagulant supply unit for concentration and the separation and concentration coagulant discharge nozzles provided in the inner cylinder, and further from the second coagulant supply pipe. The supply coagulant is supplied to the inner region of the conical portion of the rotating cylinder via the dehydration coagulant supply unit and the dehydration coagulant discharge nozzle provided in the inner cylinder. Sludge dewatering equipment.