JPH06198300A - Method and apparatus for dehydrating sludge - Google Patents

Abstract

PURPOSE:To perform a new dehydration method and apparatus for sludge removed from a waste water purifying tank on the basis of high frequency. CONSTITUTION:In a sludge dehydration apparatus, an induction coil 9 is wound around a dehydrating pipe 4 internally provided with a dehydrating conveyor 6 moving sludge from the inlet of the pipe 4 to the outlet thereof and having the wide contact area with sludge so as to allow a high frequency current to flow to the pipe 4 and both of or either one of the dehydrating pipe 4 and the dehydrating conveyor 6 is formed from a metal material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dewatering method for sludge (sludge) removed in a waste water purification tank or the like and an apparatus therefor.

[0002]

2. Description of the Related Art As a pollutant in waste water, solid substances are mixed as dissolved substances. The sludge containing a large amount of solids obtained by purifying this, that is, solid-liquid separation, is generally called sludge. The solid content of this sludge is about several% and most of it is water. In other words, the water content is 95 to 9%.
It often reaches as high as 9%.

The sludge is disposed of at an appropriate place, is buried, is dumped in the sea, or is incinerated. However, in the case of disposal, disposal or landfill, so-called pollution is apt to occur,
Therefore, the standards are strictly regulated by the law, and such means should be avoided as much as possible.

Therefore, in order to rationalize the treatment, it is necessary to remove water as much as possible and concentrate it. And, as the sludge dehydration method, there are natural dehydration, vacuum dehydration, pressure dehydration, centrifugal separation method, heat treatment method and the like. Among them, the heat treatment method is extremely effective.

By the way, conventional heat treatment methods include various methods such as burning heavy oil and directly heating the sludge with the combustion heat, or heating the sludge with the combustion heat. Although they exist, they are common in that they utilize combustion heat.

[0006]

As described above, in the method of utilizing the combustion heat, not only the temperature cannot be finely adjusted, but also the entire work place is exposed to a high temperature atmosphere due to the dissipation of the combustion heat. Therefore, the work environment was inevitably deteriorated. In addition, the complication of regular maintenance and inspection, such as cleaning of the combustion device, was involved.
The present invention provides a novel sludge dehydration method and apparatus for solving such conventional problems.

[0007]

The present invention employs, as a heating means for sludge, a heating method based on an induction heating action by a high frequency coil in place of the conventional combustion method. It is a solution to the problem.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A sludge dehydration method according to the present invention is characterized in that a moving path for dehydrating a sludge is positioned inside an induction coil in which magnetic lines of force are generated by passing a high frequency current. The required member that controls the service route is made of a metal material or a material mainly composed of a metal, and the sludge is heated by the induction heating action of the metal member based on the above magnetic force lines so as to evaporate and remove the contained water. It is a thing.

The figure represents an apparatus for carrying out the method according to the invention described above. In the figure, 1 is a sludge storage tank, 2 is a sludge supply pipe, and the sludge appropriately removed in the septic tank is accommodated in the sludge storage tank 1 through the supply pipe 2.
Further, the sludge storage tank 1 is formed in a funnel shape, and a sludge outlet 1a is formed in a small diameter portion below the sludge storage tank 1. Reference numeral 1b is an opening / closing valve interposed in the outlet 1a.

The sludge contained in the sludge storage tank 1 is set in such a manner that the solid content thereof gradually sinks and is concentrated. Then, the concentrated sludge is supplied to the supply pipe 3
Tube 4 for dehydration in the dehydrator A relying on high frequency through
It is configured to be sent to the upper part of the.

The dewatering device A which depends on the above-mentioned high frequency is provided with a dewatering pipe 4 and a transfer pipe 5 for moving the dehydrated sludge to the sludge reservoir B in the illustrated embodiment. There is as a thing. A dehydration conveyor 6 such as a screw conveyor that rotates via a motor 6a is housed inside the dehydration pipe 4, and the sludge supplied from above the dehydration pipe 4 is It is configured so that it can be gradually moved downward by a conveyor.

The dehydration conveyor 6 is not limited to the screw conveyor shown in the drawing, but may be a paddle conveyor formed by connecting disc-shaped transfer plates at a predetermined interval and angle. good. In other words, any form may be used as long as the sludge supplied from above can be slowly lowered over a predetermined period of time and the conveyor is made of a metal-based material. . That is, for example, a so-called pan conveyer in which only a container portion for containing a transferred product is made of a metal material and a large number of the containers are connected by a non-metal material, or a metal material is stretched over the surface of the non-metal material, or a metal The present invention can be implemented even with a conveyor in which a non-metallic material is stretched on the surface of the material.

Reference numeral 7 denotes a transfer screw conveyor housed in the transfer pipe body 5, which is rotated by a motor 7a.

Although the above-mentioned transfer tube body 5 is provided, the transfer tube portion 5 does not necessarily have to be provided. That is,
It is also possible to install the sludge reservoir B directly below the dewatering pipe 4, or to transfer the sludge through an appropriate conveyor provided separately.

Reference numeral 8 is a high-frequency current generator, 9 is an induction coil positioned so as to be wound around the dehydrating tube 4, and the induction coil 9 applies a high-frequency current to the induction coil 9, This is for causing the wound metal object to have an induction heating action. The high frequency applied to the induction coil 9 is appropriately set based on the amount of sludge and the moving speed, such as 1 kilohertz to 400 kilohertz.

Therefore, since the dehydrating pipe 4 and the dehydrating conveyor 6 are used as the object of induction heating based on the high frequency, that is, the object to be heated, the dehydrating pipe 4 and the dehydrating conveyer 6 are connected to each other. It is essential to form both or either of them with a metal material.

By the way, induction heating by high frequency has a great feature in that the object to be heated itself generates heat. That is, when a metal object to be heated made of a metal material is appropriately positioned in the induction coil and a high-frequency current is applied to the coil, magnetic lines of force generated by the induction coil penetrate through the metal object to be heated. At this time, an electric force that acts to prevent the magnetic line of force acts on the heated metal object, and a current in the direction opposite to the coil current is induced in the heated metal object. Such an action is called an electromagnetic induction action, and the induced current induced during the electromagnetic induction action flows through the heated metal object and causes a heat generation action due to its resistance loss. The method of returning electrical energy to thermal energy and utilizing it as described above is called induction heating. The present invention utilizes such induction heating due to high frequency.

In FIG. 2, reference numeral 10 denotes a steam removing pipe provided above and below the dehydrating pipe body 4 for discharging steam generated from the heated sludge.

In the state shown in the drawings, the sludge contained in the sludge storage tank 1 is gradually concentrated as the solid content thereof sinks. And the concentrated sludge is
It is sent to the upper portion of the dehydrating pipe body 4 in the dehydrating apparatus A via the supply pipe 3. The sludge sent into the dehydration pipe body 4 is slowly moved downward by the dehydration conveyor 6.

On the other hand, when a high-frequency current is applied to the induction coil 9 through the high-frequency current generator 8, magnetic lines of force are generated in the induction coil 9 and, therefore, an induction heating action on the metal article wound around the induction coil 9, That is, the dehydration tube 4
Then, the dehydration conveyor 6 generates heat. Therefore,
As described above, the sludge, which is being slowly fed, is heated, and the moisture contained in the sludge is removed by evaporation.

By the way, when both the dehydrating pipe 4 and the dehydrating conveyor 6 are heated, surface contact heating based on the goodness of contact between the screw surface of the conveyor and the sludge (wide contact area), and the dehydrating pipe Due to both the envelopment heating by the body 4 and the very good heat dehydration action on the sludge.

When the dehydration conveyor 6 is made of a metal material and the dehydration tube 4 is made of a ceramic material, the dehydration conveyor 6 generates heat, but the dehydration tube 4 does not generate heat. The problem of bad conditions at the work site due to is solved.

Further, although not general, the dehydration pipe 4 is made of a metal material and the dehydration conveyor 6 is made of a ceramic material, so that a variety of conveyors can be used.

Further, the dehydration pipe 4 is formed in a vertically long shape in order to stabilize the feed of the sludge and to improve the escape of steam generated from the sludge in the illustrated embodiment. I am doing it. However, the heating may be performed while moving the slug laterally.

[0025]

According to the method of the present invention, a moving path for dehydrating sludge is located inside an induction coil in which magnetic field lines are generated by passing a high frequency current, and the moving path is moved. Since the required member for controlling the sludge is made of a metallic material and the sludge is heated by the induction heating action of the metallic member based on the magnetic force lines to evaporate and remove the contained water, heating for sludge dewatering is performed. Is
Compared to the conventional case of relying on combustion of heavy oil, etc., it will be significantly rationalized.

That is, according to the method of the present invention, the heating temperature of the sludge is proportional to the strength of the high frequency current flowing in the induction coil. Therefore, not only the heating temperature can be finely adjusted but also combustion can be performed. Since it is not accompanied, the inspection and cleaning management of the device is significantly simplified. In addition, there is a problem of difficulty in uniform heating (temperature unevenness occurs) in the case of direct heating with a burner, and a problem of long time required for temperature rise required with heated air. In the method of the present invention, it is completely eliminated.

The apparatus according to the present invention comprises a dehydration pipe body 4 which is constructed by moving the accommodated sludge from the inlet side to the outlet side and accommodating therein a dehydration conveyor 6 having a wide contact surface for the sludge. Since the induction coil 9 configured to pass a high-frequency current is wound around, and both or either one of the dehydration pipe body 4 and the dehydration conveyor 6 is formed of a metal material, The implementation of the method according to the invention described above is enabled.

Further, in the apparatus according to the present invention, the sludge is heated and dehydrated while moving the sludge by the dehydration conveyor 6, so that the sludge is continuously dehydrated. That is, in the conventional apparatus for heating and dehydrating, the sludge is stored in the apparatus, taken out after the processing, and then the next sludge is stored. Unfortunately, the present invention solves this problem altogether.

Further, according to the present invention, as described in claims 3 and 4, by using the screw conveyor or the paddle conveyor as the dehydration conveyor 6, the contact surface with respect to the sludge can be widened, and accordingly, The heating for dehydration of the sludge can be performed extremely well.

Further, as described in the fifth aspect, by making the dehydration pipe body 4 vertically long, the sludge transfer and the discharge of the dewatered water vapor can be carried out very stably.

The heating data of the sludge according to the present invention is as follows. Experimental example Heating temperature: 500 ° C. High frequency: 20 kilohertz 70% water content State after heating Output / min 500 g 90.5 g 4 KW 421 g 86.1 g 4 KW 510 g 92.5 g 4 KW 411 g 84.5 g 4 KW Experimental example Heating temperature: 600 ° C. High frequency : 20 kilohertz 70% hydrated state after heating Output / min 421g 53.0g 5KW 410g 52.5g 5KW 400g 51.2g 5KW 500g 54.5g 5KW As mentioned above, 70% hydrated state after heating It has been confirmed that the weight of the slag has been significantly reduced, and that the water in the sludge has been removed, and almost all the solid matter remains. It is confirmed that the higher the heating temperature is, the higher the dehydration effect is. In addition, the reason why the heating temperature in the experimental example is set to a relatively low temperature is that, for example, in the case of high temperature heating such as high temperature of 1000 ° C., the solid matter itself is burned to generate toxic substances such as dioxins. Therefore, in the test data, combustion was limited to a relatively low temperature.

By the way, as a heating and dehydrating apparatus utilizing high frequency, a method of dehydrating by directly applying high frequency to the sludge, in other words, a method of vibrating water by high frequency to remove heat generation like a so-called microwave oven is also considered. However, as a result of experiments, it was found that this method not only significantly increases the manufacturing cost, but also involves various problems such as problems in processing the generated X-rays. On the other hand, the method based on the induction heating action by the induction coil as in the present invention is not accompanied by such a problem,
It can be said that it is an extremely excellent method suitable for practical use.

[Brief description of drawings]

FIG. 1 is an explanatory block diagram showing the present invention.

FIG. 2 is an explanatory sectional view showing an apparatus according to the present invention.

[Explanation of symbols]

 1 Sludge storage tank 1a Sludge outlet 1b Open / close valve 2 Sludge supply pipe 3 Supply pipe A Dewatering device B Sludge reservoir 4 Dehydration pipe 5 Transfer pipe 6 Dehydration conveyor 6a Motor 7 Transfer screw conveyor 7a Motor 8 High frequency current generator 9 Induction coil 10 Water vapor removal pipe

Claims (6)

[Claims] 1. A moving path for dehydrating sludge is located inside an induction coil in which magnetic lines of force are generated by passing a high-frequency current, and a required member for controlling the moving path is provided. A method for dehydrating a sludge, which is made of a metal material or a material mainly composed of a metal, and heats the sludge by an induction heating action of the metal member based on the magnetic lines of force so as to evaporate and remove contained water. 2. A dewatering pipe body (4) comprising a dewatering conveyor (6) for moving the contained sludge from the inlet side to the outlet side and having a wide contact surface for the sludge therein. In addition, the induction coil (9) configured to pass a high-frequency current is wound, and at least one of the dehydration pipe (4) and the dehydration conveyor (6) is formed of a metal material. A sludge dewatering device characterized in that 3. The sludge dewatering device according to claim 2, wherein a screw conveyor is used as the dewatering conveyor (6). 4. The sludge dewatering device according to claim 2, wherein a paddle conveyor is used as the dewatering conveyor (6). 5. The sludge dewatering device according to claim 2, wherein the dewatering pipe (4) is vertically long. 6. The sludge according to claim 2, wherein a transfer pipe body (5) in which a transfer conveyor is properly housed is connected to an outlet portion of the dehydration pipe body (4). Dehydrator.