JP2002336841A - Method for vaporizing and treating oily waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To vaporize and treat oily waste water containing oil such as water soluble cutting oil while keeping environmental pollution low. SOLUTION: The oily waste water is introduced into a vaporizer 4 kept in reduced pressure lower than atmospheric pressure, heated and vaporized. The concentrated oily waste water is withdrawn from the vaporizer 4. The steam generated by the vaporization is condensed in a condenser 15. The oil content of the condensed water is separated in an oil separator 18 and removed. The oil-removed condensed water is then purified by a biological water treating apparatus 19.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating oil-containing wastewater containing oil such as water-soluble cutting oil by evaporation.

[0002]

2. Description of the Related Art One of the treatments of oil-containing wastewater containing oil such as a water-soluble cutting oil is a method of treating the wastewater by evaporation.

Japanese Patent Application Laid-Open No. 11-649 as a prior art proposes that oil-containing wastewater is introduced into an evaporator open to the atmosphere, heated in the evaporator, and concentrated by evaporating water. I have.

[0004]

However, the prior art evaporating method is to release steam heated and evaporated in an evaporator to the atmosphere, and this steam contains oil volatilized from oil-containing wastewater and water. Since the oil-containing wastewater contains oil scattered as a mist, releasing this water vapor into the atmosphere has a problem that it emits a bad smell to the surroundings and pollutes the atmosphere. Evaporation of the wastewater is carried out at approximately atmospheric pressure, so that its boiling point is about 1
Since the temperature is as high as 00 ° C. and the scale components in the oil-containing wastewater adhere firmly to the heat transfer surface, there is also a problem that a large amount of trouble is required to remove the scale of the heat transfer surface.

[0005] It is a technical object of the present invention to provide an evaporation method which does not cause these problems.

[0006]

In order to achieve this technical object, claim 1 of the present invention is directed to an evaporator in which oil-containing wastewater containing oil such as a water-soluble cutting oil is kept at a reduced pressure below atmospheric pressure. While heating and evaporating, and taking out the concentrated oil-containing wastewater from the evaporator, the water vapor generated by the evaporation is condensed, and then the condensed water is separated and removed in an oil separator. Water treatment by living organisms is performed. "

A second aspect of the present invention is characterized in that "in the first aspect, the heating and evaporating in the evaporator is performed at a temperature of 40 to 60 ° C.".

Further, claim 3 of the present invention provides:
A feature of the present invention is that, in the above-mentioned claim 1, the inside of the evaporator is maintained at a reduced pressure of less than the atmospheric pressure by a liquid ring vacuum pump.

[0009]

As described above, the oil-containing wastewater is introduced into the evaporator kept under reduced pressure, heated and evaporated, and the water vapor is condensed. In addition, low-pollution can be achieved without releasing odors and the like into the atmosphere, and by performing the evaporation of the oil-containing wastewater at a reduced pressure, that is, at a temperature lower than 100 ° C., the scale of the oil-containing wastewater can be reduced. Since the components can be prevented from firmly adhering to the heat transfer surface, the scale can be easily removed.

[0010] In addition, the condensed water may be separated and removed in an oil separator, and then subjected to water treatment by a living organism, thereby recovering as contaminated water or industrial water having a low oil content, COD and BOD. You can.

Further, according to the present invention, the water treatment by the living organism of the condensed water can be stably performed at a high level irrespective of summer and winter.

Further, according to the third aspect, it is possible to reduce the pressure in the evaporator below the atmospheric pressure while reducing the emission of harmful gases and odors into the atmosphere.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawing of FIG.

In this figure, reference numeral 1 denotes a raw water tank storing oil-containing wastewater containing oil such as water-soluble cutting oil, and reference numeral 2 denotes a self-vapor-compression evaporative concentrator for the oil-containing wastewater.

The evaporating and concentrating apparatus 2 includes the raw water tank 1
Evaporator 4 into which oil-containing wastewater is supplied via supply line 3
It has.

The interior of the evaporator 4 is maintained at a reduced pressure below the atmospheric pressure, as will be described later. Above the evaporator 4, a plurality of horizontally extending heat transfer tubes 5 are provided in a multi-stage manner. One end is at the entrance header 6 and the other end is at the exit header 7
Each has an opening.

The oil-containing wastewater supplied to the bottom of the evaporator 4 is pumped out by a circulation pump 8 and sent to a nozzle 9 disposed above the heat transfer tube 5 via a pipe 10. After being sprayed on the outer surface of the heat transfer tube 5, it is circulated so as to return to the bottom in the evaporator 4 again.

During this circulation, the oil-containing wastewater is removed from each of the heat transfer tubes 5.
It is heated and boiled on the surface of the slag, and is so-called evaporatively concentrated so that the water evaporates, becomes concentrated oil-containing wastewater having a high concentration, and is discharged from a pipe 11 to a storage tank 12 of the concentrated oil-containing wastewater.

On the other hand, steam generated during heating and evaporation in the evaporator 4 is supplied from a boiler (not shown) to a pipe 1.
After being sucked and compressed by an ejector 14 driven by steam as a heat source sent in 3, the heat is supplied into the heat transfer tubes 5 from an inlet header 6 at one end thereof, and the evaporator 4 To heat the circulating oil-containing wastewater in the furnace.

A part of the water vapor generated in the evaporator 4 is guided to the condenser 15 by the cooling water to condense the condensed water in the condenser 15 and the outlet header 7.
The condensed water is taken out by the drain pump 16 and the non-condensable gas in the condenser 15 and the outlet header 7 is sucked by the liquid ring type vacuum pump 17 so that the evaporator 4 and the The inside of the condenser 15 and the inside of the outlet header 7 are kept at a reduced pressure below the atmospheric pressure.

In this case, the degree of pressure reduction is determined by the condenser 1
The temperature of the condensed water taken out from 5 is set to be about 40 to 60 ° C.

The condensed water taken out of the condenser 15 by the drain pump 16 contains oil which volatilizes and scatters from the oil-containing wastewater during evaporation in the evaporator 4 and has a high BOD and COD value. The condensed water is led to a conventionally well-known adsorption type or membrane type oil separator 18 using activated carbon or the like, where the oil component is separated,
This is also guided to a well-known water treatment apparatus 19 for living organisms, where the water treatment for lowering the BOD and COD values is performed, and then the water is sent out from a pipeline 20.

By the way, the biological water treatment apparatus 19
Prior to this, a pH adjusting means 19a using an alkali and an acid, a means 19b for adding a nutrient for bacteria,
Needless to say, an air blowing unit 19c for aeration and a sterilizing agent adding unit 19d after the treatment are provided.

In addition, in the water treatment by living organisms, the temperature of the condensed water taken out from the condenser 15 is set to about 40 to 60 ° C., so that the water is most suitable for water treatment by living organisms regardless of summer and winter. Temperature, for example, 2
Since the temperature can be maintained at 0 to 30 ° C., water treatment by living organisms can be stably performed at a high level.

The oil separated from the condensed water in the oil separator 18 is put into the storage tank 12 for the concentrated oil-containing wastewater through a pipe 21.

The non-condensable gas sucked from the condenser 15 into the liquid ring type vacuum pump 17 contains harmful gases and odorous components accompanying the evaporation. In the liquid ring vacuum pump 17,
Since the liquid can be absorbed by the liquid sealing liquid to the liquid ring vacuum pump 17, harmful gases and odorous components released into the atmosphere together with the non-condensable gas can be reliably reduced.

The gas-liquid discharged from the discharge side of the liquid ring vacuum pump 17 is led to a gas-liquid separator 22, where it is separated into a non-condensable gas and a liquid for liquid consolidation. Is released into the atmosphere through a pipe 23, and the liquid for liquid sealing is returned to the suction side of the liquid ring vacuum pump 17 by a pump 24 and circulated for repeated use.

Since the liquid sealing liquid for the liquid ring vacuum pump 17 is circulated and used repeatedly as described above, the concentration of impurities becomes high. Replace with liquid or replace with little by little.

The raw water tank 1 and the evaporator 4
An oil / water separator 25 may be provided in the supply line 3 of the oil-containing wastewater to remove as much oil as possible. The oil separated in the oil-water separator 25 is supplied to the storage tank 1 of the concentrated oil-containing wastewater via a pipe 26.
Put in 2. A demister 27 for collecting mist accompanying the water vapor is provided inside the evaporator 4.

Next, the present inventors conducted an experiment of evaporating and concentrating the oil-containing wastewater containing water-soluble cutting oil to 10% in the apparatus having the above-mentioned configuration and having a daily throughput of 10 cubic meters. The results were as shown in Table 1.

[0031]

[Table 1]

The condensed water taken out of the condenser 15 is led to an oil separator 18 where oil is separated therefrom.
By performing water treatment with the biological water treatment device 19, the condensed water can be recovered as miscellaneous water and industrial water in toilets and the like, and the concentrated oil-containing wastewater in the storage tank 12 can be subjected to various types of incineration. It could be burned as auxiliary fuel in furnaces or boilers.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 Raw water tank of oil-containing wastewater 2 Evaporator 3 Supply line of oil-containing wastewater 4 Evaporator 5 Heat transfer tube 8 Circulation pump 15 Condenser 17 Liquid ring vacuum pump 18 Oil separator 19 Biological water treatment device

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) C02F 3/12 C02F 3/12 F (72) Inventor Kei Katayama 6-7-5 Motejima, Nishiyodogawa-ku, Osaka Co., Ltd. F-term in Sasakura (reference) 4D028 AA03 AB00 AC04 BA02 BB06 BC13 BD06 CD01 4D034 AA26 BA01 CA12 CA21 4D058 QA03 SA15 UA01 4D076 AA16 BA02 BA12 BA24 BB13 EA12Z HA06 JA01

Claims (3)

[Claims] An oil-containing wastewater containing an oil such as a water-soluble cutting oil is introduced into an evaporator maintained at a reduced pressure below atmospheric pressure, heated and evaporated, and the concentrated oil-containing wastewater is taken out from the evaporator. A method for evaporating oil-containing wastewater, comprising condensing water vapor generated by the evaporation, separating and removing the condensed water in an oil separator, and then subjecting the condensed water to biological water treatment. 2. The method for evaporating oil-containing wastewater according to claim 1, wherein the heating and evaporating in the evaporator is performed at a temperature of 40 to 60 ° C. 3. The method for evaporating oil-containing wastewater according to claim 1, wherein the inside of the evaporator is maintained at a pressure lower than the atmospheric pressure by a liquid ring vacuum pump.