JP2001137839A - Method for treating waste water containing solid content - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating waste water for efficiently removing solid contents from waste water in which solid contents are diffused, especially, waste water containing oil in which the solid contents are diffused in a stable state like fine grains. SOLUTION: In this method for treating waste water, hydrocarbon oil is mixed to waste water containing solid contents and then statically placed so as to be divided into a water layer and an oil layer. As a result, it is possible to efficiently remove the solid contents from the waste water, and to surely treat waste water containing oil in which the solid contents are diffused in a stable state like fine grains.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wastewater treatment method for removing solids from wastewater, and more particularly to a method for removing solids from oil-containing wastewater containing fine solids generated from a petroleum refining process or the like. The present invention relates to a method for treating wastewater.

[0002]

2. Description of the Related Art Conventionally, solids in waste water have been removed by a method such as filtration, centrifugation, or standing, and most of them have been removed by such a method. However, when the solid content is in the form of fine particles, the solid content is stably dispersed in the waste water, and aggregation or precipitation is not obtained even when left for a long period of time. In addition, even if filtration or centrifugation is performed, it is efficiently and sufficiently removed. It is very difficult. In particular, wastewater from the desalting step of crude oil in petroleum refining, or wastewater generated from various contact treatment steps, etc., contains mineral oil as oil along with fine solids. Are dispersed in a more stable state due to the interaction of Further, in the case of food processing, wastewater from the processing step or the like has a similar problem because some fats and oils are contained as solids and oils.

[0003]

The wastewater containing solids in a stable dispersed state as described above does not sufficiently separate solids and oil even if left in a sedimentation basin for a long period of time. Separate high-cost treatment had to be performed, increasing the overall burden on wastewater treatment. Accordingly, there is a need for a method for treating wastewater that can efficiently separate solids even with such wastewater. The present invention solves the above-mentioned problems, and efficiently removes solids from wastewater containing solids dispersed therein, particularly oil-containing wastewater dispersed in a stable state in the form of fine particles. It is an object to provide a method for treating wastewater.

[0004]

Means for Solving the Problems In the course of research on a wastewater treatment method for efficiently removing solids, the present inventors have found that when hydrocarbon oil is mixed into the wastewater, the solids are removed from the water layer into an oil tank. And found the present invention, and came to the present invention. That is, the method for treating wastewater containing solid content according to the present invention is characterized in that hydrocarbon oil is mixed with wastewater containing solid content in a dispersed state, and then separated into an aqueous layer and an oil layer by standing. According to the present invention, the wastewater in which the solid content is dispersed,
After the hydrocarbon oil is mixed, the mixture is allowed to stand and separated into an aqueous layer and an oil layer.The solid content is selectively transferred to the hydrocarbon oil side, and an oil layer containing the transferred solid content in a dispersed state, It can be easily separated into the water layer of the waste water from which the waste has been removed.
In particular, when the particulate solids are more stably dispersed and contained in the waste water by interaction with oil-soluble impurities such as oil and phenol, the stability is lost by mixing the hydrocarbon oil. Since oil and impurities in the wastewater migrate to the hydrocarbon oil, the concentrations of the oil and impurities in the wastewater also decrease with the solid content.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The solid content referred to in the present invention is a solid insoluble component contained in a dispersed state in waste water. The method of the present invention can be effectively applied to any type of industrial wastewater containing solids. Specific examples include insoluble organic and inorganic substances, a mixture thereof (eg, sludge), and crushed powder of a catalyst contained in crude oil in a petroleum refining process. The present invention
Although the size of the solid content is not particularly limited, it is preferable that the average particle size is 100 μm or less, and particularly 1 to 10 μm.
m are difficult to settle and difficult to filter,
It can be applied effectively to these. The amount of the solid content in the wastewater is preferably 10 ppm or more, and when the amount is 100 ppm or more, the present invention is particularly effective. In addition, the weight of the solid content can be quantified as a component remaining after filtration with a 10 μm filter and washing with toluene, for example.

The wastewater to be treated in the present invention is not particularly limited as long as it contains the above-mentioned solid content. The present invention is more effective especially when the drainage contains oil. For example, oils and fats and oils entrained in the wastewater of the oil refining process and the wastewater of the food processing process have an effect of dispersing solid components in the wastewater in a stable state. For this reason, it is generally more difficult to separate solids from wastewater containing such oils and the like, but according to the present invention, solids can be easily separated from wastewater. Specifically, the present invention is effective when the effluent contains 0.001% by weight or more, particularly 0.01 to 1% by weight of a lipophilic component such as an oil component or a fat component. The present invention is also effective for wastewater treatment containing oil-soluble organic substances such as phenol, and can reduce the concentration of these substances.

The specific gravity of the hydrocarbon oil used in the present invention is 0.95 in order to allow the waste water and the oil component to stand and separate efficiently.
The following are preferable, and it is particularly preferable to use a hydrocarbon oil of 0.90 or less. Not very light hydrocarbon oils
From the viewpoint of safety, those having a specific gravity of 0.70 or more are preferable. It is not necessary to use a refined hydrocarbon oil, and the hydrocarbon oil may contain solids and moisture. Specific examples of such oils include crude oils in petroleum refining, heavy naphtha, kerosene, light oil, heavy oil, lubricating oils, and intermediate products or by-products of the corresponding petroleum fractions or mixed oils thereof. And the oil recovered from washing and recovery of crude oil tankers and waste oil generated in the oil refining process.
Slop oil, washing oil and the like can also be used.

In the present invention, mixing of the waste water and the hydrocarbon oil may be performed by any method, for example, a method using a stirring blade or a jet flow in a stirring tank, a method using a mixing valve, an in-line mixer, or the like. Such a known method may be appropriately selected and performed. As the temperature at the time of mixing, in order to lower the viscosity and increase the efficiency of mixing, the wastewater and / or the hydrocarbon oil may be heated and mixed at 40 to 90 ° C, further 50 to 70 ° C. preferable. The mixing time depends on the mixing method, but is 1 minute or more, especially 3 to 20 minutes.
The amount is preferable in order to make sufficient contact between the waste water and the hydrocarbon oil. The mixing ratio of the wastewater and the hydrocarbon oil is such that the hydrocarbon oil is at least 0.1 part by volume, especially 0.2 part
It is preferred to mix up to 0.6 parts by volume.

The mixture of the waste water and the hydrocarbon oil is separated by gravity into an aqueous layer and an oil layer by standing. The stationary separation can be performed using a method of separating the oil tank or the like while keeping it batchwise for a certain period of time, or a continuous method of separating the oil tank while passing through an inlet and an outlet at a certain interval. . Examples of a separation apparatus using a continuous method include a stationary separation tank such as an API oil separator, a PPI oil separator, and a CPI oil separator. In addition,
Forcible separation by centrifugal force is not preferred in the present invention, which aims at removing solids from wastewater, since the solids once transferred to the oil side may return to the water side. Further, an emulsion breaker can be added to facilitate separation of the water layer and the oil layer. As the emulsion breaker, a cationic breaker is preferable.

The wastewater treated by the method of the present invention is separated as an aqueous layer, contains almost no solid matter, and has a low concentration of oil-soluble organic impurities (such as oil, fat and phenol). Is declining. On the other hand, the mixed hydrocarbon oil is separated and recovered as an oil layer. The recovered hydrocarbon oil is (1) recycled and reused for wastewater treatment. (2) Refined by mixing with petroleum refining raw materials such as crude oil to obtain petroleum products. (3) Heating furnace for petroleum refining It can be used as fuel for boilers and boilers (self-consumed fuel), or as a raw material for pyrolysis equipment. Since the solid content has moved to an oil layer having a relatively small specific gravity, it can be easily concentrated and separated by centrifugation or the like. When the hydrocarbon oil is recycled, it can be repeatedly used except for the solid content. Also, when refining hydrocarbon oil recovered as an oil layer, even if it contains solids, it will migrate to heavy oil when distilled, and will be contained in asphalt and heavy oil. It is not particularly necessary to remove solids. Needless to say, purification treatment may be performed after removing solids by centrifugation.

[0011]

Hereinafter, the present invention will be described more specifically based on examples.

(Example) 100 ppm by weight of a solid having an average particle diameter of 10 μm, 100 ppm by weight of an oil component, and 10% by weight of other organic substances as phenols are contained in a wastewater of a crude oil desalination tank. Light oil was placed in a stirring tank at a ratio of 0.2 part by volume to 1 part by volume of the drainage, and mixed and stirred by a stirring blade for 15 minutes. The temperature of the stirring tank is about 60 ° C
And held. Next, the mixture of the water from the desalination tank and light oil was sent to a CPI oil separator and separated by standing to obtain an aqueous layer and an oil layer. The solid content contained in the treated wastewater of the aqueous layer was 5 ppm by weight, the oil content was 10 ppm by weight, and the phenols were 1 ppm by weight, and the removal rate was 90% to 95%.
On the other hand, the solid content in the oil layer was 500 ppm by weight, and the water content was 1% by weight.

In the above Examples and Comparative Examples described later, the solid content was measured for solids contained in water.
After filtration through a 0 μm fluoropore filter, the substance captured on the filter was washed with a sufficient amount of pure water at 80 ° C. and then with a sufficient amount of toluene at 80 ° C., and the residue was quantified as a solid content. In the case of the solid content contained in the oil, the oil is dissolved in a sufficient amount of toluene at 80 ° C.
The solution was filtered through a 0 μm fluoropore filter, the substance captured on the filter was washed with a sufficient amount of pure water at 80 ° C., and the residue was quantified as a solid content.

(Comparative Example) The wastewater from the desalination tank used in the above example was mixed with hydrocarbon oil without mixing and stirring.
It was sent to an I oil separator and separated by standing. The solid content in the treated waste water collected from the water layer outlet of the CPI oil separator was 100 ppm by weight, which was the same as that in the desalination tank waste water before the CPI oil separator was charged, and the solid content could not be removed.

[0015]

According to the wastewater treatment method of the present invention, a hydrocarbon oil is mixed with a wastewater containing a solid content, and the mixture is allowed to stand and separated into an aqueous layer and an oil layer. This makes it possible to efficiently remove solids from the wastewater, and is particularly effective in treating oil-containing wastewater in which the solids are dispersed in a fine and stable state.

Continued on the front page (72) Inventor Mitsuhiro Ohashi 25th Kitahama-cho, Chita-shi, Aichi Japan Energy Co., Ltd. F-term (reference) 4D037 AA12 AB02 BA11 BB04 BB08 4D051 AA01 BA09

Claims (1)

[Claims] 1. A method for treating wastewater containing solids, comprising mixing hydrocarbon oil with wastewater containing solids in a dispersed state, and separating the mixture into an aqueous layer and an oily layer by standing.