JP2011045846A - Method and apparatus for treating wastewater containing oil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for treating wastewater containing oil capable of treating the wastewater containing the oil to obtain fuel oil at a low cost without requiring many chemicals or heat energy. <P>SOLUTION: The wastewater containing the oil produced in a cold rolling process of a steelmaking plant is introduced into a flotation separation pond 3 and separated into floatable oil-containing scum and settleable oil-containing sludge. The oil-containing scum is separated from water through a plurality of stages of vibration sieves 15 to make dehydrated scum, which is charged into a mixed solution tank 14 with the oil-containing sludge and mixed with calorie adjusting oil for adjusting the calorie thereof to make mixed solution. Then the mixed solution is subjected to a particle pulverizing and viscosity adjusting process by means of a vibrating mill 17 having many vibrating rods to obtain the fuel oil. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to an oil-containing wastewater treatment method and treatment apparatus, and more particularly to an oil-containing wastewater treatment method and treatment apparatus suitable for the treatment of wastewater containing rolling oil generated from a cold rolling process. is there.

  Oil-containing wastewater containing a large amount of rolling oil is discharged from the cold rolling process of the steel factory. As the rolling oil, for example, oil obtained by mixing vegetable oil palm oil or mineral oil is used. In addition, iron powder is mixed in the oil-containing waste water.

  As a treatment method for such oil-containing wastewater, Patent Document 1 discloses that a cationic polymer flocculant is added to oil-containing wastewater to agglomerate oil to form oil-containing scum, and the oil-containing scum is stirred in a stirring tank to remove mud. And a method for recovering oil is disclosed. However, this method increases the cost of the drug, and the heat value of the recovered oil is low and unstable. Therefore, it is difficult to reuse the recovered oil as fuel.

  Patent Document 2 discloses a method in which activated carbon and an inorganic flocculant are added to oil-containing wastewater and the oil is precipitated and separated together with COD and the like. However, this method also increases the chemical cost, and it is difficult to reuse the recovered oil as fuel.

  In addition, an incineration method in which oil-containing scum separated from oil-containing wastewater by natural flotation is dried to the extent that viscosity can be secured with a steam indirect dryer and incinerated using a rotary kiln is also being carried out. However, since steam dryers can reduce the moisture content of oil-bearing scum to about 75% in the case of waste oil mixed with vegetable oil, etc., rotary kilns use a lot of subsidies to evaporate moisture in oil-bearing scum. Fuel is needed. Moreover, since the gas volume is increased by water vapor, there is a problem that the exhaust gas treatment facility is enlarged.

  In addition to this, a method of reducing the water content of the oil-containing scum by using a centrifugal dehydrator is also conceivable, but centrifugal dehydration is expensive due to high equipment cost and operation cost.

Japanese Patent No. 4246087 Japanese Patent No. 4169614

  Therefore, the object of the present invention is to solve the above-mentioned conventional problems, and to treat the oil-containing wastewater at low cost without requiring a large amount of chemicals and thermal energy, and to treat the oil-containing wastewater and take out the fuel oil. Is to provide.

  An oil-containing wastewater treatment method according to the present invention made to solve the above-mentioned problems is directed to separating the oil-containing wastewater into a floating oil-containing scum and a sedimentary oil-containing sludge by guiding the oil-containing wastewater to a floating separation pond. In addition to separating water into dehydrated scum, it is put into a mixing dissolution tank together with oil-containing sludge, mixed with calorie adjustment oil to adjust calorie, and then passed through a vibration mill to refine particles and adjust viscosity, It is characterized by obtaining fuel oil.

  Note that, as in claim 2, the oil-containing wastewater can be wastewater containing rolling oil generated from a cold rolling process in a steel factory. Further, as in claim 3, it is preferable to perform the floating separation in two stages of natural floating and pressurized floating. Moreover, it is preferable to return the water | moisture content isolate | separated by the vibrating sieve to a floating separation pond like Claim 4.

  The oil-containing wastewater treatment apparatus of the present invention includes a floating separation pond that separates oil-containing wastewater into oil-containing scum and oil-containing sludge, a vibrating sieve that separates moisture from the separated oil-containing scum, and uses the dehydrated scum. And an oil-containing sludge mixed with a calorific value adjusting oil to adjust the calorific value, and a vibration mill that refines particles in the mixed solution taken out from the mixed dissolving tank and uses it as fuel oil. It is a feature.

  In addition, it is preferable that the floating separation pond is composed of a natural levitation pond and a pressurized levitation pond as in claim 6, and the vibration sieve in the previous stage having a large opening and a mesh opening as in claim 7 It is preferable to use a combination with a subsequent vibration sieve having a small size. Further, as in claim 8, it is preferable that the vibration mill has a structure having a large number of vibrating rods inside a cylindrical mill body.

  According to the present invention, oil-containing wastewater can be separated into oil-containing scum and sedimentary oil-containing sludge, and the moisture of the oil-containing scum that has floated can be separated by a vibrating sieve without using heat energy. Moreover, the separated oil can be reused as fuel oil by the addition of the calorific value adjusting oil and the refinement of the particles by the vibration mill. For this reason, it is possible to treat oil-containing wastewater at a lower cost than the conventional method.

It is a flowchart which shows embodiment of this invention. It is explanatory drawing of a vibration sieve. It is a front view of a vibration mill. It is a top view of a vibration mill. It is sectional drawing of a vibration mill.

Hereinafter, preferred embodiments of the present invention will be described.
As shown in FIG. 1, the oil-containing wastewater is first guided to a floating separation pond 3 composed of a natural floating pond 1 and a pressurized floating pond 2. In this embodiment, the oil-containing wastewater is oil-containing wastewater containing rolling oil generated from the cold rolling process of the steel mill, but is not necessarily limited thereto. As described above, the rolling oil is an oil obtained by mixing a mineral oil with a vegetable oil called palm oil.

  In the natural levitation pond 1, the oil content in the oil-containing wastewater floats and separates on the water surface due to the difference in specific gravity. In the pressurized levitation pond 2, the floating separation of the oil is promoted using the levitation force of the air bubbles supplied from the bottom. That is, fine oil droplets float on the surface of the water adhering to or accompanying the rising bubbles. In these floating separation ponds 3, the oil-containing wastewater is separated into a floating oil-containing scum, a sedimentary oil-containing sludge, and water. In this embodiment, since the oil-impregnated scum floated and separated in the natural levitation pond 1 has a large amount of oil, it is directly taken out to the draining tank 4 where the water is separated and sent to the oil tank 5. Along with the oil-impregnated scum that is floated and separated in the pond 2, it can be sent to the scum receiving tank 6.

  Since the water in the natural levitation pond 1 contains a relatively large amount of oil, it is sent to the pressure levitation pond 2, but the water from which the oil-impregnated scum has been separated in the pressure levitation pond 2 is returned to the natural levitation pond 1 by the return pipe 7. Is done. Similarly, the water separated in the draining tank 4 is returned to the natural floating pond 1 by the return pipe 8.

  The oil-impregnated scum separated in the floating separation pond 3 as described above is collected in the scum receiving tank 6 and heated by the heater 9, and then the water is separated by the vibrating sieve 10. The oil-impregnated scum is heated in order to adjust the viscosity so that oil and water can be easily separated by the vibrating sieve 10, and in this embodiment, it may be heated to about 30 to 50 ° C.

  As shown in FIG. 2, the vibrating sieve 10 is provided with a vibrating sieve plate 12 inside the can body 11, and it is preferable to arrange a plurality of stages of vibrating sieves 10 in series. The first-stage vibrating screen 10a has a large opening, and the second-stage vibrating screen 10b has a small opening. For example, the aperture of the front vibrating screen 10a may be 1.0 to 0.6 mm, and the aperture of the rear vibrating screen 10b may be 0.5 to 0.2 mm. In addition, as shown in FIG. 3, the latter vibration sieve 10b can be two or three stages. When the oil-impregnated scum is applied to such a vibrating sieve 10, moisture is dropped and separated through the sieve plate 12, and the dehydrated scum can be taken out from the sieve plate 12.

  Although the dewatering rate by the vibrating sieve 10 reaches about 40%, the dewatering rate by the conventional steam type indirect dryer is only about 20%. If a centrifugal dehydrator is used, the dehydration rate reaches about 40%, but the equipment cost and operation cost become high. On the other hand, if the multistage vibrating sieve 10 is used, the equipment cost and the operation cost are low, and the dehydration rate equivalent to that of the centrifugal dehydrator can be achieved. It seems that there is no example of dehydrating oil-impregnated scum using the vibrating sieve 10 in this way. The dewatered scum from which the water has been separated is sent to the receiving pit 11. The separated water is returned to the natural levitation pond 1 through the return pipe 13.

  The oil-containing sludge settled and separated at the bottom in the natural levitation pond 1 and the pressure levitation pond 2 described above has more oil than oil-containing scum. For this reason, it is sent to the receiving pit 11 as it is. In this way, the receiving pit 11 is supplied with dewatered scum and oil-containing sludge. In addition, if there is a highly viscous waste oil such as recovered grease, it may be supplied to the receiving pit 11 together.

  The oil tank 5 is supplied with oil-impregnated scum having a large amount of oil from the draining tank 4, but in addition to that, calorific adjustment oil is supplied. The calorific value adjustment oil may be any oil with a large calorific value, but for example, B heavy oil can be used. The amount may be appropriately adjusted depending on the properties (components and oil content) of the oil-containing wastewater. The contents of the oil tank 5 and the contents of the receiving pit 11 are agitated and mixed in the mixing dissolution tank 14. The mixing dissolution tank 14 is also provided with a heater. In this mixing and dissolving tank 14, the oil-containing sludge and the dewatered scum are heated and stirred with the oil-containing scum and the calorific value adjusting oil having a large amount of oil, and adjusted so as to have a predetermined heat generation amount and a predetermined viscosity.

  Thereafter, the slurry-like mixed solution taken out from the mixed dissolution tank 14 is passed through the vibration sieve 15 to remove foreign matters, heated to 30 to 60 ° C. in the heating tank 16, and sent to the vibration mill 17. The vibrating sieve 15 is not essential in the present invention.

  The vibration mill 17 is a facility for finely pulverizing solids and particles in the sludge with a vibrating rod. An example thereof is as shown in FIGS. 3 to 5, and a cylindrical mill body 20 in which a large number of rods 21 are housed is vibrated by a vibration shaft 23 driven by a motor 22. In this embodiment, the mill body 20 has two upper and lower stages, and the mixed solution is introduced from the inlet 24 located at the front end of the upper mill body 20, and flows into the lower mill body 20 at the rear end. It is discharged from a discharge port 25 located at the front end of the mill main body 20.

  The upper and lower two-stage mill main body 20 is supported at two places on the front and rear by a support frame 27 supported by a spring 26. Then, the mill main body 20 is vibrated vigorously by bringing the bearing portions 28 of the two vibration shafts 23 disposed on both sides thereof into contact with the support frames 27. The amplitude is 8 mm, for example, and the frequency is 1200 times per minute. The rod 21 is made of steel and contains hundreds of rods having a diameter of 25 mm and a length of 3 m, and the mixed solution has an impact force between the rods 21 that vibrate while flowing inside the mill body 20. The solids and particles are pulverized.

Since such fine pulverization proceeds and the viscosity of the mixed solution also decreases, it is preferable to operate the vibration mill 5 so that the viscosity at 30 to 60 ° C. falls within the range of ²⁰ to 1000 mm ² / s. . Note in the range of viscosity of 20~1000mm ² / s, this becomes costly and not easy to reduce the viscosity than the viscosity conversely becomes difficult to use as a fuel exceeds 1000 mm ² / s It is. More preferably, it is preferable to set it as the range of 20-100 mm < ² > / s.

  By passing through the vibration mill 17, the mixed solution becomes a fuel oil having an appropriate viscosity. The obtained fuel oil can be used as it is, or can be further added with a calorific value adjusting oil as needed, and sold as an alternative fuel for heavy oil, or used as an auxiliary fuel oil for a rotary kiln for waste incineration.

  As described above, according to the present invention, oil-containing wastewater can be processed at low cost without requiring a large amount of chemicals and thermal energy, and fuel oil can be taken out.

  The oil-containing wastewater containing the rolling oil generated from the cold rolling process of the steel factory was treated with the equipment shown in FIG. The oil-containing scum separated in the floating separation pond contained 70 to 90% moisture and 5 to 10% oil. The oil-containing sludge contained 35% oil, and its lower heating value was 4000 kcal / kg. When this oil-impregnated scum was dehydrated with the three-stage vibrating screen shown in FIG. 2, the water content was reduced to 40% and became dehydrated scum. Note that the opening of the first stage vibrating screen was 0.8 mm, and the opening of the second and third stage vibrating screens was 0.3 mm. These oil-impregnated sludge and dewatered scum are mixed with B heavy oil or high-calorie waste oil (for example, hydraulic oil waste oil) as a calorie adjusting oil in a mixing and dissolving tank, and further passed through a vibration mill shown in FIGS. Got oil. This fuel oil was used as an auxiliary fuel for a rotary kiln for waste incineration.

  According to the present invention, the incineration amount of waste derived from oil-containing wastewater can be reduced by 95% compared to the conventional case. In addition, the amount of auxiliary fuel used in the rotary kiln for waste incineration was reduced by about 40% compared to the prior art. In addition, when the fuel oil obtained by the present invention was added as an auxiliary fuel, the incineration capacity of the rotary kiln could be increased by a factor of about 2.

DESCRIPTION OF SYMBOLS 1 Natural floating pond 2 Pressurized floating pond 3 Floating separation pond 4 Drain tank 5 Oil tank 6 Scum receiving tank 7 Return pipe 8 Return pipe 9 Heater 10 Vibrating sieve 10a Vibrating sieve 10b of the former stage Vibrating sieve 11 Can body 12 Sieve Plate 13 Water return pipe 14 Mixing dissolution tank 15 Vibrating sieve 16 Heating tank 17 Vibrating mill 20 Mill body 21 Rod 22 Motor 23 Vibrating shaft 24 Input port 25 Outlet port 26 Spring 27 Support frame 28 Bearing part

Claims (8)

  Oil-containing wastewater is led to a floating separation pond and separated into floating oil-containing scum and sedimentary oil-containing sludge. The oil-containing scum is separated into water by a vibrating sieve to form dehydrated scum, and is added to the mixing and dissolution tank together with the oil-containing sludge. A method for treating oil-containing wastewater, characterized by mixing with calorific value adjusting oil, adjusting the calorific value, and then passing through a vibration mill to refine particles and adjust viscosity to obtain fuel oil.   The method for treating oil-containing wastewater according to claim 1, wherein the oil-containing wastewater is wastewater containing rolling oil generated from a cold rolling process of a steel factory.   The method for treating oil-containing wastewater according to claim 1, wherein the flotation separation is performed in two stages of natural flotation and pressurized flotation.   The method for treating oil-containing wastewater according to claim 1, wherein the water separated by the vibrating sieve is returned to the floating separation pond.   A floating separation pond that separates oil-containing wastewater into oil-containing scum and oil-containing sludge, a vibrating sieve that separates moisture from the separated oil-containing scum to form dehydrated scum, and the dehydrated scum and the oil-containing sludge are mixed with calorific value adjusting oil An oil-containing wastewater treatment apparatus comprising: a mixing dissolution tank that adjusts the amount of heat; and a vibration mill that refines particles in the mixed solution taken out from the mixing dissolution tank and uses the fuel as a fuel oil.   6. The apparatus for treating oil-containing wastewater according to claim 5, wherein the levitation separation pond comprises a natural levitation pond and a pressurized levitation pond.   6. The apparatus for treating oil-containing wastewater according to claim 5, wherein the vibration sieve is a combination of a front-stage vibration sieve having a large mesh opening and a rear-stage vibration sieve having a small mesh opening.   6. The apparatus for treating oil-containing wastewater according to claim 5, wherein the vibration mill has a structure having a large number of vibrating rods inside a cylindrical mill body.

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