JPH11253705A - Solid-liquid separation method and apparatus for watercontaining solid matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of significantly heightening the dewatering efficiently by the same solid-liquid separation apparatus as a conventional one by improving the gel property of precipitated solid matter and to provide an apparatus for carrying out the method, regarding a solidliquid separation apparatus for sludge. SOLUTION: Suspended solids in an object liquid to be treated are flocculated and precipitated and the resultant precipitated solids are heated and then separated into solids and a liquid. In a screw decanter type centrifugal separator comprising a bowl 1 rotated at high speed and a screw conveyer 3 installed coaxially with the bowl and rotating in the same direction at a different rotation speed, a heating apparatus 5 is installed in the outer wall of the bowl in the deposition region of solids 4 near a discharge outlet, so that solids deposited in the bowl inner wall can be separated by solid-liquid separation while being heated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-liquid separation method and apparatus for increasing the solid-liquid separation rate of water-containing solids, and more particularly to a solid-liquid separation rate for solids discharged from a centrifuge or the like. The present invention relates to a method and an apparatus for solid-liquid separation.

[0002]

2. Description of the Related Art A processing apparatus for separating a solid content from a liquid to be treated in which the solid content is suspended is widely used, for example, in the field of sewage treatment. In Japan, in large-scale treatment plants, dewatering sludge by a centrifugal separator is the mainstream. However, this dewatered sludge has a water content of about 85%, and it is necessary to further pass through a drying step in order to incinerate and melt, or to use or landfill green farmland. In addition, these dewatered sludges have a problem that they have a high moisture content, are heavy in weight, and have a strong odor.

[0003] For example, a centrifugal separator known as a screw decanter type has a conical portion at one end, a bowl rotating at high speed, and a screw conveyer arranged coaxially therewith and rotating at a slightly different rotation speed from the bowl. Become 1000
The suspended solid is settled on the inner surface of the bowl with a centrifugal force of up to 3000 g. The precipitated solids are transferred by a screw conveyor to the bowl cone. It is well known as a general property of colloids that when a suspension is concentrated, it becomes a jelly-like gel containing water, but in the case of sludge treatment, etc., it promotes precipitation. It is common to add a polymer flocculant to flocculate the suspended solids for treatment. For this reason, there is a strong tendency that the moisture content of the precipitated solid content is further increased.

For this reason, in a screw decanter type centrifugal separator, one end of a bowl is formed in a conical shape, and the sediment is transferred to a position higher than the water surface in a bowl called a beach by a screw conveyor, and centrifuged in a position free of moisture. Attempts have been made to reduce the water content by consolidation by applying a force or forcibly reducing the volume by reducing the pitch of the screw. However, despite these attempts, it was practically difficult to reduce the water content to 85% or less as described above.

[0005] In recent years, a method of heating all of the liquid to be treated has been adopted overseas in the case of separating digested sludge of sewage by a centrifugal separator. It is reported that this method can reduce the water content by about 5%. This method is not limited to the treatment of digested sludge. However, since the entire liquid volume is heated, a large heat source is required. In addition, there is a problem that a strong odor is generated from the separated liquid discharged from the solid-liquid separator, and is actually used only for treating digested sludge. Because digested sludge is subjected to anaerobic treatment, it has an advantage that it has less odor than mixed sludge and that digestive gas generated in the treatment process can be used as a heat source. However, in Japan, mixed sludge equipment, which has a stronger odor than digested sludge equipment, is the mainstream, and residents have a strong rejection of sewage odor.

[0006]

An object of the present invention is to provide a method capable of remarkably increasing the dehydration rate by a solid-liquid separation apparatus similar to the conventional one by improving the properties of the precipitated solid, and a method for the same. It is intended to obtain a device to be implemented.

[0007]

According to the solid-liquid separation method of the present invention, the suspended solids in the liquid to be treated are treated with a physical force such as centrifugal force or gravity by using or not using a polymer flocculant. Agglomeration and sedimentation by the action of, and the resulting solid precipitate is heated and solid-liquid separated. The sediment solids may be sediment solids due to natural gravity like sediment sludge in a sedimentation basin, or solids dehydrated by a solid-liquid separation device such as a centrifuge or a filter press. And
The solid-liquid separator may be heated in the solid-liquid separator during the solid-liquid separation process, or the solid-liquid separator may be divided into two stages and separated as a separate device after dehydration in the first stage. May be heated and dehydrated in the second solid-liquid separation device. Further, the heating is desirably in the range of 40 ° C to 70 ° C. At 40 ° C. or lower, almost no improvement in the dehydration rate due to heating is observed. Further, in the microbial treatment of wastewater, nutrients in water are eaten by microorganisms to solidify or gasify, and the cell membrane of microorganisms plays a major role in the composition of solids. However, at 70 ° C. or higher, there is a danger that the cell membrane is destroyed and the cell fluid is washed away.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As an apparatus for advantageously carrying out the solid-liquid separation method of the present invention, a screw decanter type centrifuge can be mentioned. A bowl having a conical portion at one end and rotating at high speed, and a screw conveyer arranged coaxially with the screw conveyor and rotating in the same direction with a difference in rotational speed, are supplied into the rotating bowl. A screw decanter centrifuge that separates and sediments solids from the suspension by centrifugal force and accumulates the solids on one side of the bowl by a screw conveyor, and discharges the solids with a high moisture content from the vicinity of one end of the bowl. In the above, the present invention can be practiced by providing a heating device for the outer wall of the bowl in the solid deposition area near the discharge port, thereby performing solid-liquid separation while heating the solid deposited on the inner wall of the bowl. As the heating device, an appropriate type of heating device such as an electric heating device arranged outside the bowl, a heating device by flowing a high-temperature gas along the bowl outer wall, a direct heating by a burner or a heating device by frictional heat is used. Can be.

The present invention is not limited to the above screw decanter centrifuge, but can be implemented in various solid-liquid separation devices such as a filter press device. In addition, the centrifugal separator having the conventional structure is used as a first-stage solid-liquid separator, and the solid content containing a large amount of water from the centrifuge is heated and dehydrated in a second solid-liquid separator, which is a separate device. You may. According to this method, the solid-liquid separation capability of the existing equipment can be increased by attaching only the second solid-liquid separation device to the existing centrifuge.

[0010]

The test results for the change of the dehydration rate by the method of the present invention are shown. Test 1 Dewatered sludge was collected from the centrifugal concentrator. 84.9 moisture content
%Met. A hand squeeze test was performed on the sludge at room temperature, but no water was removed. When this sludge was heated and dehydrated by sandwiching it with a Kim towel, water oozed out, and a decrease in water content was observed. The results were as follows.

[Table 1]

Test 2 The test was performed using a screw decanter centrifuge in which the outer wall of the bowl was directly heated by a burner.

[Table 2] The stock solution had an inorganic coagulant PAC of 2000 PPM added thereto. From the results, it has been clarified that the water content of the solid content can be easily reduced by 5 to 10% according to the present invention.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention; FIG. 1 is a partial cross-sectional view showing the vicinity of a solids discharge port of a centrifugal separator embodying the present invention. In the vicinity of the solids discharge port 2 of the bowl 1 of the centrifugal separator, a sedimentary layer 4 of solids separated from the liquid to be processed, which is transported by the screw conveyor 3, is formed. A heating device 5 using a heater or a heat pipe is provided on the outer wall of the cone portion of the bowl, and heats the bowl directly by obtaining energy supply (arrow) from a power source or a heat source. In this embodiment, the screw conveyor 3 is also provided with a heating device 6 for heating the solid content deposited layer 4 as a whole. Reference numeral 7 denotes a casing, and A denotes a heating range.

In the embodiment of FIG. 2, the heating device 16 is located slightly away from the bowl 1 and indirectly heats the bowl 1. In this embodiment, the heating device can be fixed to the casing 7, and the structure of the device, such as energy supply, can be greatly simplified. Also, in this embodiment and the following embodiments, only the bowl 1 is heated, but it goes without saying that a heating device may be provided on the screw conveyor 3 as needed.

The embodiment shown in FIG. 3 uses a heating device 26 using a heating fluid such as a high-temperature gas. The flow path 21 for the heating fluid is formed by an annular wall 22 fixed to the outer surface of the bowl 1 and an annular wall 23 having a U-shaped cross section fixed to the casing 7 with a slight gap therebetween. An appropriate number of nozzles 24 are provided on the annular wall 23, and the high-temperature fluid B is supplied from the nozzles 24 into the channel 21. 25 is a fluid outlet. Further, in the same structure, a burner may be provided instead of the nozzle 24, and the bowl 1 may be directly heated by the burner flame.

FIG. 4 shows an embodiment in which a heating device 36 using frictional heat is used. A ridge 31 is provided on the outer surface of the bowl 1, and a friction piece 32 is engaged with the ridge 31. Friction piece 3
2 is fixed to the casing 7, and the ridge 3 is
1 is pressed. Due to the high-speed rotation of the bowl, frictional heat is generated, and the ridge 31 is strongly heated.

FIG. 5 shows an embodiment using a press solid-liquid separator. A sludge stock solution or a sludge solid content containing a large amount of water is supplied through a valve 42 into a press chamber formed by the filter cloth 41, and depressurized and dewatered by a pressurizing device 43. Reference numeral 44 denotes an outlet for the separated liquid. In this embodiment, heating devices 46 such as heaters are arranged above and below the press chamber, and pressurized and dehydrated while heating the liquid to be treated.

[0017]

As described above, the solid-liquid separation method and apparatus of the present invention can reduce the water content to about 75% by heating the water-containing solid to a temperature of 70 ° C. or less. This makes it extremely easy to handle the discharged solids. In addition, when implemented in a centrifugal separator, the heating portion may be only the solid deposit in the apparatus, and the low energy temperature, combined with the low heating temperature, does not result in high energy consumption. Also, even when used for sludge treatment,
Since the discharged liquid is not heated and remains almost at room temperature,
The generation of odor is almost the same as the treatment at room temperature, and has a remarkable effect that it can be carried out without any problem under special conditions in Japan.

[Brief description of the drawings]

FIG. 1 shows a configuration of a first embodiment of a solid-liquid separation device of the present invention, wherein (a) is a partial cross-sectional view and (b) is a cross-sectional view taken along line AA.

FIGS. 2A and 2B show a configuration of a second embodiment of the solid-liquid separation device of the present invention, wherein FIG. 2A is a partial cross-sectional view and FIG.

3A and 3B show a configuration of a third embodiment of the solid-liquid separation device of the present invention, wherein FIG. 3A is a partial cross-sectional view, and FIG. 3B is a cross-sectional view taken along line CC.

FIGS. 4A and 4B show the configuration of a fourth embodiment of the solid-liquid separation device of the present invention, wherein FIG. 4A is a partial cross-sectional view, and FIG.

FIG. 5 is a conceptual diagram showing a configuration of a fifth embodiment of the solid-liquid separation device of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 bowl 2 solids discharge port 3 screw conveyor 4 solids deposition layer 5, 6 heating device 7 casing 16, 26, 36, 46 heating device 21 heated fluid flow path 22, 23 annular wall 24 nozzle 25 fluid discharge port 31 protrusion Article 32 Friction piece 33 Spring 41 Filter cloth 42 Valve 43 Pressurizing device 44 Separated liquid outlet

Claims (5)

[Claims] 1. A method for solid-liquid separation of hydrated solids, which comprises coagulating and precipitating suspended solids in a liquid to be treated, and heating the resulting solids for solid-liquid separation. 2. A suspended solid content in a low-concentration liquid to be treated is precipitated and dehydrated by the action of a physical force such as a centrifugal force, with or without the use of a polymer flocculant. 2. The method for solid-liquid separation of water-containing solids according to claim 1, wherein the solid is separated by heating. 3. The method according to claim 1, wherein the heating temperature is in a range of 40 ° C. to 70 ° C. 4. A solid-liquid separation device for precipitating and dewatering suspended solids in a low-concentration liquid to be treated by the action of a physical force such as centrifugal force, wherein the solid-liquid separation device has a heating device for the generated water-containing solids. Solid-liquid separation device characterized by the following 5. A suspension fed into a rotating bowl, comprising a bowl rotating at a high speed, and a screw conveyor arranged coaxially with the screw conveyor and rotating in the same direction with a rotation speed difference. In a screw decanter-type centrifuge that separates and sediments solids from a liquid by centrifugal force and accumulates the solids on one side of a bowl by a screw conveyor, and discharges the water-containing solids from near one end of the bowl, 5. A solid-liquid separation device according to claim 4, wherein a heating device for the outer wall of the bowl is provided in the area where the solid content is deposited, whereby the solid content deposited on the inner wall of the bowl is separated while heating.