JP3650571B2 - Drain purification device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drain purification device, and more particularly, to a drain purification device suitable for separating and recovering oil from drain discharged from an air compressor and discharging clean water to a public sewer.
[0002]
[Prior art]
In air compressors that are widely used in the industry, moisture in the air is condensed during the compression process, and the lubricating oil of the compressor is suspended in the water and mixed with the drain. Discharged.
[0003]
Large reciprocating compressors and oil-cooled screw compressors, etc., have high oil concentrations in the drain, and releasing this drain into the general sewer causes water pollution and contamination. This would violate the wastewater standards of the Pollution Control Act (n-hexane content of 5 ppm or less). Therefore, the oil, which is the main harmful substance in the drain, is separated from water and collected, treated for recycling and incineration, and only purified water (with n-hexane content of 5 ppm or less) is discharged into the general sewer. It will be necessary.
[0004]
Conventionally, a gravity separation method using a specific gravity difference between water and oil has been used.
[0005]
In gravity separation, since the oil separation speed is proportional to the square of the oil droplet diameter, the oil droplet diameter that can be floated and separated, that is, can be released without mixing with water is 60 μm or more, and emulsification is performed when the oil droplet diameter is 60 μm or less. It becomes the state of. In particular, in the case of an oil droplet diameter of 1 to 5 μm, it hardly floats and maintains the emulsified state.
[0006]
As an oil-water separation method for emulsified oil with very small oil droplets in water, there is an electrolytic flotation method (“Wastewater Treatment Technology Facility Management Manual-Oil-Containing Drainage” published by Kanagawa Prefectural Environment Department, Showa 57-3-31).
[0007]
A conventional electrolytic cell that performs oil-water separation by the electrolytic levitation method will be described with reference to FIG.
The drain D discharged from the air compressor flows from the lower part of the electrolytic cell 1. A plurality of pairs of positive and negative electrodes 2, 3 are disposed opposite to each other in the electrolytic cell 1, and oil components are aggregated by electrolysis, and the aggregated oil components and generated hydrogen gas adhere to the cream-like scum 4. And emerge.
[0008]
The floating scum 4 is scraped intermittently to the scum receiver 6 by the schema 5 and is periodically discharged (Ex) as waste 7. Further, the electrolyzed drain Da is pushed by the newly flowing drain D and enters the specific gravity difference separation tank 8 from the electrolytic cell 1.
[0009]
An aluminum alloy is used as the electrode metal of the positive electrode because the aluminum ions dissolved by electrolysis have the effect of destroying the emulsified oil and aggregating the oil.
[0010]
Aluminum ions eluted during electrolysis then become aluminum oxide, and if discarded together with oil separated from water (electrolyzed drain Da), it becomes environmental pollution. A floating object (hereinafter abbreviated as SS) 9 in which aluminum oxide and oil are mixed is precipitated at the bottom of the difference separation tank 8 and discharged (Ex). Moreover, since SS10 also precipitates at the bottom of the electrolytic cell 1, it is discharged (Ex) together with SS9 in the specific gravity difference separation tank 8 and disposed.
[0011]
The drain (water) Da in the specific gravity difference separation tank 8 is discharged (Ex) from the purified water intake port 11 provided at the upper part of the specific gravity difference separation tank 8, and is discarded through a post-treatment adsorption / filter unit. Stainless steel is often used as the negative electrode.
[0012]
[Problems to be solved by the invention]
In the specific gravity difference separation tank 8 of the above-described conventional apparatus, water and aluminum oxide are precipitated and separated using the specific gravity difference, so that time is required for reliable separation.
For this purpose, the specific gravity difference separation tank 8 has a U-shaped (reverse siphon-shaped) space configuration, and receives electrode metal from the electrolytic cell at the upper part of one vertical space and dissolves electrode metal that melts from the water during the electrolysis process. The water is drained from the upper part of the other vertical space by being deposited on the downward flow, and the flow path is lengthened so that the residence time of the water in the specific gravity difference separation tank 8 is given so that the coagulation effect is produced. ing.
[0013]
SS accumulates on the bottom of the tank over time. However, when the amount of the drain D to be processed is large, since it takes the shape of a reverse siphon, discharge from the clean water intake port 11 increases, the flow velocity in the specific gravity difference separation tank 8 increases, and the residence time is short. Not only is the separation from water using the specific gravity difference insufficient, but SS has a specific gravity close to that of water, so the fine one is a water stream and is discharged from the clean water intake port 11 and is shown in the subsequent figure. The amount to reach the suction / filter section increases, the suction / filter section becomes clogged, and the filter must be replaced.
In particular, if the specific gravity difference separation tank 8 is made smaller for miniaturization, the fine SS deposited on the bottom of the tank is easily sprinkled with running water, and is likely to be clogged in the adsorption / filter section downstream. Become.
[0014]
Therefore, an object of the present invention is to provide a drain purifying apparatus capable of reliably separating and recovering a mixture of dissolved electrode metal and oil that cannot be recovered even in a specific gravity difference separation tank.
[0015]
[Means for Solving the Problems]
A feature of the drain purification apparatus of the present invention that solves the above-described problem is that at least a pair of positive and negative electrodes that electrolyze the drain to separate oil and water and float on the top during the electrolysis process An electrolyzer having a schema for discharging scum and a U-shaped space, and water separated in the electrolyzer at the top of one of the vertical spaces is received in the process of electrolysis from the water. In the drain purification device having a specific gravity difference separation tank for precipitating the electrode metal to be melted and discharging water from the upper part of the other vertical space, the drain wall has an inlet for water discharged from the specific gravity difference separation tank in the middle of the tank wall. A precipitation tank having a discharge port for discharging water in the tank is provided above the inlet.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an overall configuration of a drain purifying apparatus according to an embodiment of the present invention, and FIG. 2 shows an enlarged main part of FIG.
In addition, the same code | symbol is used for the same thing as what was shown in FIG. 4, or an equivalent thing, and duplication of description is avoided.
[0017]
The drain D discharged from the compressor 21 is supplied to the electrolytic cell 1 by the pump 22. The supplied drain D is electrolyzed between the electrodes 2 and 3 by supplying a current from the DC power source 23 in the electrolytic cell 1. The scum 4 separated and levitated by electrolysis is scraped out of the electrolytic cell 1 by the schema 5 and is periodically discharged as waste 7 through the scum receiver 6. The drain Da having a low oil concentration after separation enters the specific gravity difference separation tank 8 and is introduced into the filter unit 41 from the purified water intake port 11 through the precipitation tank 31.
The filter unit 41 is filled with an oil adsorbent, and the remaining oil is removed and the purified water W is discharged.
[0018]
Next, the structure of the electrolytic cell 1 and the specific gravity difference separation tank 8 will be described.
The flow path P between the electrolytic cell 1 and the specific gravity difference separation tank 8 is located at the upper middle position of the partition plates of both tanks 1 and 8. The scum 4 that floats up while the lower layer of the scum 4 that floats and accumulates on the liquid surface of the electrolytic cell 1 does not reach the upper part of the flow path P is scraped out by the schema 5. Therefore, the scum 4 that has floated to the liquid surface of the electrolytic cell 1 does not spread to the liquid surface of the specific gravity difference separation tank 8. The cross section of the flow path P is such that the flow velocity here is slower than the flying speed of the scum 4. Then, the floating scum 4 does not flow directly into the specific gravity difference separation tank 8, and the scum 4 does not spread over the liquid surface of the specific gravity difference separation tank 8.
[0019]
The drain D supplied to the electrolytic cell 1 by the pump 22 is from a pipe 26 provided in a linear shape, a cross shape, or a radial shape so as to face the lower ends of the positive and negative electrodes 2 and 3 at a position floating from the bottom of the electrolytic cell 1. Supply evenly. Accordingly, the flow rate of the drain D that blows out from the pipe 26 to the electrolytic cell 1 is reduced, and the precipitated aluminum oxide 10 is settled and deposited on the bottom of the electrolytic cell 1 below the pipe 26 without being rolled up.
[0020]
In the specific gravity difference separation tank 8, the amount of oil contained in the drain Da is small, and the amount of SS9 mixed with aluminum oxide is less than that of the conventional apparatus and settles on the tank bottom.
Even if the drain amount D increases, the amount of SS contained in the drain Db discharged from the clean water intake port 11 to the settling tank 31 is significantly reduced.
[0021]
As shown in FIG. 2, the sedimentation tank 31 has an inlet 32 for water discharged from the specific gravity difference separation tank 8 in the middle of the tank wall, and discharges water in the tank above the inlet 32. A discharge port 33 is provided. Further, a baffle plate 34 is provided between the inlet and the outlet 33 to obstruct the water flow toward the outlet 33.
[0022]
Reference numeral 35 denotes an inclined tank bottom, 36 denotes a discharge pipe provided at the lowest part of the tank bottom 35, and 37 denotes a closing valve provided on the discharge pipe 36.
[0023]
In the sedimentation tank 31, the inflow port 32 opens laterally in the tank wall, and the drain Db that flows in flows horizontally in the tank. The shut-off valve 37 is closed and the flow disappears toward the drain bottom Dc between the inlet 32 and the tank bottom 35 as it goes to the tank bottom 35, so to speak, it is in a so-called dead water state. For this reason, the SS in the drained drain Db slowly aggregates and settles over time and accumulates as SS38.
[0024]
The flow in the settling tank 31 becomes an upward flow from the inflow port 32 toward the discharge port 33 existing above. If this flow is generated immediately from the inlet 32, the SS flowing out from the outlet 33 increases, so that the baffle plate 34 that becomes an obstacle to the upward flow causes a downward flow, and the drain Db in the sedimentation tank 31 flows. The residence time is further increased.
[0025]
When a certain amount of SS 38 is accumulated, the shut-off valve 37 is opened to remove SS, but since the tank bottom 35 is inclined toward the discharge pipe 36, most of the SS can be recovered.
[0026]
According to the experiments by the present inventors, about the raw drain water having an n-hexane content of about 50 ppm, the n-hexane content was 5 ppm or more at the inlet of the adsorption / filter unit in the conventional apparatus of FIG. In the apparatus of the present invention shown in FIG. 1, the n-hexane content is about 2 ppm at the inlet of the filter unit 41 and 1 ppm or less at the outlet of the filter unit 41, and it is confirmed that the drainage standard of the water pollution control method can be sufficiently satisfied. ing.
[0027]
Moreover, when the component analysis of the wastewater containing SS taken out through the shut-off valve 37 was performed, the oil content was 30% by weight, the aluminum oxide was 20%, the remaining water, and the like. Was also confirmed. Therefore, the frequency of adsorbent replacement in the filter unit 41 is remarkably reduced, and there is an effect of reducing running costs.
[0028]
FIG. 3 shows a case where the inclined tank bottom of the settling tank 31 shown in FIG. In addition to the reliable discharge of SS9, the amount of fine SS wound up by the flow is reduced and it is difficult to flow out into the sedimentation tank 31.
[0029]
In the specific gravity difference separation tank 8, the inclined tank bottom is good in a single flow going downstream as shown in FIG. 3, but in the sedimentation tank 31, a funnel shape may be used. It doesn't matter.
[0030]
The operation of the shut-off valve may be automatic opening / closing using a timer as an electromagnetic valve or manual opening / closing.
[0031]
【The invention's effect】
As described above, according to the drain purification device of the present invention, it is possible to reliably separate and recover the dissolved electrode metal and oil that cannot be recovered even in the specific gravity difference separation tank.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a drain purification apparatus according to an embodiment of the present invention.
2 is a cross-sectional view of a sedimentation tank in the drain purification device of FIG.
FIG. 3 is a cross-sectional view of a specific gravity difference separation tank in the drain purification device of FIG. 1;
FIG. 4 is an enlarged view showing a main part of a conventional drain purification device.
[Explanation of symbols]
D, Da to Dc ... Drain P ... Flow path 1 ... Electrolytic cell 2, 3 ... Electrode 4 ... Scum 5 ... Schema 8 ... Specific gravity difference separation tank 9, 10, 38 ... Melted electrode metal oxide and oil mixture (SS)
DESCRIPTION OF SYMBOLS 11 ... Purified water intake port 31 ... Precipitation tank 32 ... Inlet port 33 ... Discharge port 34 ... Baffle plate 8a, 35 ... Tank bottom 36 ... Drain pipe 37 ... Shut-off valve 41 ... Filter unit

Claims (4)

An electrolyzer having at least one pair of positive and negative electrodes for electrolyzing the drain to separate oil and water, and a schema for discharging a scum generated and floated in the upper part of the electrolysis process; It has a space and receives the water separated in the electrolytic cell at the upper part of one vertical space, precipitates the electrode metal that melts from the water during the electrolysis process, and discharges the water from the upper part of the other vertical space. In a drain purification device having a specific gravity difference separation tank
A drain purification apparatus comprising a precipitation tank having an inlet for discharging water from the specific gravity difference separation tank in a middle stage of the tank wall and having an outlet for discharging water in the tank above the inlet. . 2. The drain purifier according to claim 1, wherein the settling tank is provided with a baffle plate between the inlet and the outlet, which obstructs the water flow toward the outlet. 2. A drain purifier according to claim 1, wherein a discharge pipe having a shut-off valve communicates with the bottom of the specific gravity difference separation tank or the settling tank, and the tank bottom has an inclination toward the discharge pipe. apparatus. 4. The drain purifier according to claim 3, wherein the discharge pipe in the specific gravity difference separation tank communicates with a lower portion of the other vertical space.

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