JP2010227860A - Method for treating oil-impregnated granular material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce expenses required for chemicals and water treatment in a treatment method for removing oil from oil-impregnated granular material (such as oil-impregnated sludge or oil-contaminated soil) consisting of aggregate of coarse grains and fine grains and containing oil to recover the granular material at a reusable state. <P>SOLUTION: In this invention, treatment of oil-impregnated sludge is performed using treatment equipment consisting of a two-shaft stirring device (grinding apparatus) 1, a cyclone classifier (classifier) 2, a two-shaft stirring device (washing apparatus) 3, and a solid-liquid separator 4. Classification is performed after grinding the oil-impregnated sludge, and grains with particle diameters of 20 μm or less contained in the coarse grains become 20 mass% or less. After the coarse grains are washed by washing liquid to move oil contained in the grains to the liquid side, solid-liquid separation is performed to recover the grains from which oil is removed as purified sludge. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a treatment method in which oil is removed from an oil-containing granular material (oil-containing sludge, oil-contaminated soil, etc.) composed of coarse and fine aggregates and containing oil, and recovered in a reusable state.

Conventionally, a method has been proposed in which oil-containing sludge, contaminated soil, and the like generated during wastewater treatment in various factories are cleaned and recovered in a reusable state.
As a method of cleaning the oil-containing sludge and collecting it in a reusable state, there is a method described in Patent Document 1 below. In this method, oil-containing sludge is brought into contact with a solvent to dissolve the oil in the solvent, and then solid-liquid separation is performed, and the solid is washed with water containing a surfactant to recover the purified sludge. . In this method, a solvent and a surfactant are used according to the amount of oil-containing sludge, so when processing a large amount of oil-containing sludge, the cost of chemicals is increased and the amount of wastewater is also increased, so the water treatment cost is also increased. The site area of the equipment will also increase.

  On the other hand, in the following Patent Document 2, since the fine particles have a larger surface area per unit volume than the coarse particles, the degree of contamination is higher than the coarse particles. A method is described in which a fine particle (silt) is classified and only the fine particle is washed with a liquid that elutes contaminants. It is described that the coarse particles are further classified after being crushed, and the particles which have become coarse particles by this classification can be used for backfilling soil and the like after washing with circulating water.

  If this method is used to classify and only the fine particles are washed, the cost for chemicals and water treatment can be reduced compared to the method of washing without classifying. However, in this method, secondary particles in which fine particles are firmly attached to the coarse particles are included in the coarse particles after classification. Therefore, when the target value of the degree of cleanliness of particles that can be reused is high, this method is not suitable as a method for treating oil-containing granular materials.

JP 9-176659 A JP-A-2005-238102

  The subject of this invention is the processing method which removes oil from the oil-containing granular material (oil-containing sludge, oil-contaminated soil, etc.) which consists of an aggregate | assembly of a coarse grain and a fine grain and contains oil, and collect | recovers in a reusable state It is to provide a method that can be applied even when the target value of the degree of cleanliness of particles that can be reused is high, while reducing costs for chemicals and water treatment.

  In order to solve the above-mentioned problems, the method for treating oil-containing granular materials according to the present invention is a treatment for reducing particles by friction between particles against oil-containing granular materials comprising an aggregate of coarse particles and fine particles and containing oil. And the oil-containing granular material after the grinding step (for example, the range of 25 μm to 30 μm as a classified particle size) is classified into a coarse particle and a fine particle, and the particle size contained in the coarse particle A classifying step in which particles of 20 μm or less become 20% by mass or less, and a washing in which the coarse particles after the classification step are washed in a liquid, and the oil contained in the particles constituting the coarse particles is transferred to the liquid side And a recovery step of recovering the particles from which oil has been removed by solid-liquid separation of the liquid containing the particles after the cleaning step.

  According to this method, secondary particles contained in the oil-containing granular material (particles firmly adhered to each other) are separated into primary particles in the grinding step (for example, fine particles become coarse particles). The secondary particles that are firmly attached are separated into fine and coarse particles), so that the fine particles enter the coarse particles in the classification process compared to the case where the grinding process is not performed before the classification process. Probability can be lowered. On the other hand, when the grinding step is not performed before the classification step, fine particles constituting the secondary particles enter the coarse portion.

Also, since the oil adhering to the surface of the coarse particles in the grinding process is transferred to the fine particles, the oil content on the fine particle side is higher and the oil content on the coarse particle side is lower than when the grinding process is not performed. can do.
In this method, since the coarse particles having a low content of fine particles are washed and collected, the target value can be achieved even when the target value of the degree of cleaning of particles that can be reused is high. In addition, the amount of drug used in the washing step can be significantly reduced by setting the particles having a particle size of 20 μm or less contained in the coarse particles in the classification step to 20 mass% or less.

  Since the sludge of process wastewater at steelworks is composed of iron oxide scales and metal aggregates with a particle size of about 40 μm to 100 μm and fine particles with a particle size of about 1 μm to 10 μm, the oil-containing granule is a process at the steelworks In the case of wastewater sludge, the coarse particles and fine particles can be separated in the range of 10 μm to 30 μm. And the amount of chemicals used in the washing process is remarkably reduced by setting the classified particle size in the range of 25 μm to 30 μm so that the particles having a particle size of 20 μm or less contained in the coarse particles are 20% by mass or less. can do.

  The method of the present invention is a method for removing oil from an oil-containing granule comprising an aggregate of coarse particles and fine particles and containing the oil, and recovering it in a reusable state. Even when the target value of the degree of cleanliness of particles that can be reused is high, it can be applied.

It is process drawing explaining the processing method of the oil containing sludge corresponded to one Embodiment of this invention. It is a graph which shows the result of having investigated the particle size distribution about the oil-impregnated sludge before and behind a grinding process, and the coarse-grained part and fine-grained part after a classification process regarding sample No. 1 of an Example. It is a graph which shows the relationship between the content rate of the particle | grains with a particle size of 20 micrometers or less contained in the coarse particle part after a classification process, and surfactant concentration required in order for the oil content rate of the collect | recovered purification sludge to become a target value. is there.

Embodiments of the present invention will be described below.
The processing method of the oil-containing sludge of this embodiment consists of a grinding process, a classification process, a washing process, and a recovery process. As shown in FIG. 1, this method includes a biaxial agitator (grinding device) 1, a cyclone classifier (classifier) 2, a biaxial agitator (cleaning device) 3, a solid-liquid separator 4 and Can be carried out using a processing facility consisting of

In the grinding step, the oil-impregnated sludge is introduced into the biaxial agitator 1, and a process of reducing the particles by friction between the particles constituting the oil-impregnated sludge is performed, and the secondary particles contained in the oil-impregnated sludge are converted into primary particles. To be separated. Therefore, the secondary particles in which the fine particles are firmly attached to the coarse particles are separated into fine particles and coarse particles. Further, the oil adhering to the surface of the coarse particles is transferred to the fine particles.
The oil-containing sludge after the grinding step is introduced into the cyclone classifier 2 and classified into a coarse particle and a fine particle according to the set conditions. In this classification step, the classified particle diameter is set in the range of 25 μm to 30 μm so that the particles having a particle diameter of 20 μm or less contained in the coarse particles are 20% by mass or less.

Since the fine-grained fraction after the classification step has a high oil content, it is dehydrated and then disposed of by incineration or landfill.
The coarse particles after the classification step are introduced into the biaxial stirring device 3 and the washing step is performed. An aqueous solution containing a surfactant and sodium hydroxide as a cleaning agent is injected into the biaxial stirring device 3 from the cleaning agent injection tube 31. In the biaxial agitator 3, the particles constituting the introduced coarse particles are washed with a surfactant and sodium hydroxide, and the oil moves to the liquid side.

The contents of the biaxial agitator 3 are introduced into the solid-liquid separator 4 after the washing step, the water containing the oil is discharged, and the solid (particles from which the oil has been removed) is recovered as the purified sludge. After the oil is removed, the water containing the discharged oil can be circulated and used as water for imparting appropriate fluidity to the object to be treated in the grinding process, classification process, and washing process.
According to the method of this embodiment, by performing the grinding step before the classification step, it is possible to reduce the probability that the fine particles enter the coarse particles in the classification step, and are included in the coarse particles in the classification step. By making the particles having a particle size of 20 μm or less 20% by mass or less, the amount of the chemicals (surfactant and sodium hydroxide) used in the cleaning process can be significantly reduced.

In addition, as a grinding apparatus used at a grinding process, the crusher etc. which equipped the eccentric double drum other than a biaxial stirring apparatus can be used.
As a classification device used in the classification process, in addition to the cyclone classifier, a sedimentation separation device, a vibration sieve device, and the like can be used.
As the cleaning agent used in the cleaning step, in addition to an aqueous solution containing a surfactant and sodium hydroxide, water containing a surfactant, an alkaline aqueous solution such as an aqueous sodium hydroxide solution or an aqueous calcium hydroxide solution, or the like can be used. As the surfactant, nonionic or anionic surfactants can be used.

Nonionic surfactants have high oil detergency, and anionic surfactants are suitable for washing not only oil components but also complex contaminants. Alkaline aqueous solution has high detergency of animal and vegetable oils and fats due to saponification. In particular, by using a mixture of an alkaline aqueous solution and an anionic surfactant as a cleaning agent, an excellent cleaning action is exhibited.
The solid-liquid separation device used in the recovery process is a device that can efficiently perform solid-liquid separation when the concentration of the separation target is relatively high and the specific gravity is relatively large, such as a dehydrator such as a filter press, and a scraper type such as a classifier. Examples thereof include a solid-liquid separator and a sedimentation separator. Examples of the apparatus that can efficiently perform solid-liquid separation when the concentration of the separation target is relatively low and the specific gravity is relatively small include a centrifugal separator, a flotation separator, a filter separator using a strainer and a filter medium, and the like.

Using the treatment facility shown in FIG. 1, oil-containing sludge generated from the process wastewater of an ironworks was treated by the method described in the embodiment.
A twin screw paddle mixer “SD-55” manufactured by Taiheiyo Kiko Co., Ltd. was installed as the twin screw stirring device 1 serving as a grinding device, and a liquid cyclone “SC-150” manufactured by Murata Industrial Co., Ltd. was used as the cyclone classifier 2. Was installed. The hydrocyclone has a top nozzle diameter of 28 mm and a bottom nozzle diameter of 13 mm. A twin-screw paddle mixer “SD-55” manufactured by Taiheiyo Kiko Co., Ltd. was installed as the twin-screw agitator 3 serving as a cleaning device, and a scraping-type solid-liquid separation manufactured by Saiko Co., Ltd. was used as the solid-liquid separator 4. The device “High Mesh Separator” was installed.

  In sample No. 1, the oil-containing sludge was first introduced into the biaxial paddle mixer, and the grinding process was performed by operating for 10 minutes. Next, the ground oil-containing sludge is introduced into a cyclone classifier, and industrial water is added so that the solid content of the oil-containing sludge is 10% by mass. The inlet pressure of the cyclone: 0.20 MPa, the outlet pressure: 0 The classification step was performed by operating at 0.005 MPa (condition 1).

  The coarse particles were taken out from the bottom nozzle, the fine particles were taken out from the top nozzle, and each particle size distribution was measured. The particle size distribution of the oil-containing sludge was measured before and after the grinding process. These results are summarized in the graph of FIG. In addition, the ratio of the coarse particles to the fine particles after the classification step was 90% by mass for the coarse particles and 10% by mass for the fine particles. Furthermore, when the oil content after the classification step was measured, the coarse particle content was 2.2% by mass and the fine particle content was 22% by mass.

  Next, the coarse particles taken out from the bottom nozzle are introduced into a cleaning biaxial stirrer, and the content of “Pelesoft 207” manufactured by Miyoshi Oil & Fats Co., Ltd. as a nonionic surfactant is determined from the cleaning agent injection tube. Washing comprising an aqueous solution having 0.3% by mass, “Spamin S” manufactured by Miyoshi Oil Co., Ltd. as an anionic surfactant, 0.3% by mass, and sodium hydroxide content of 0.8% by mass After injecting the agent, the cleaning process was performed by operating the biaxial agitator for 20 minutes. Thereby, the oil which the particle | grains which make a coarse particle part contained moves to the liquid side.

Next, the contents of the biaxial agitator were introduced into a scraping type solid-liquid separator and operated until the solid-liquid separation was completed, and then the solid content (particles from which oil was removed) was taken out. The solid matter taken out was rinsed twice with industrial water and then recovered as purified sludge. It was 0.26 mass% when the oil content rate of the collect | recovered purification sludge (coarse grain content) was measured.
As can be seen from the graph of FIG. 2, the oil-containing sludge (raw sludge) before treatment is mainly composed of particles having a particle size of 5 to 20 μm, but the particles having a particle size of about 10 μm increase after the grinding step. ing. This indicates that the secondary particles are separated into primary particles by the grinding treatment. The fine particles after the classification step account for 80% of particles having a particle size of 20 μm or less, and the coarse particles have a content of particles having a particle size of 20 μm or less of 10%.

In sample No. 2, the grinding step was not performed, and the oil-containing sludge was directly introduced into the cyclone classifier, the classification step was performed under the same conditions as in No. 1, and the subsequent steps were also performed in the same manner.
In sample No. 2, the ratio of the coarse particles to the fine particles after the classification step was 91% by mass for the coarse particles and 9% by mass for the fine particles. The oil content after the classification step was 3.7% by mass for the coarse particles and 7.8% by mass for the fine particles. Moreover, it was 3.2 mass% when the oil content rate of the collect | recovered purified sludge (coarse part) was measured.

In sample No. 3, the cleaning agent injected from the cleaning agent injection tube in the cleaning step is 1.0% by mass of the same nonionic surfactant as in No. 1, and the same anionic surfactant as in No. 1. The aqueous solution was 1.0% by mass and the sodium hydroxide content was 2.4% by mass. Except for this, the treatment was performed in the same manner as in No. 2.
In sample No. 3, the ratio of the coarse particles to the fine particles after the classification step was 91% by mass for the coarse particles and 9% by mass for the fine particles. The oil content after the classification step was 3.7% by mass for the coarse particles and 7.8% by mass for the fine particles. Moreover, it was 0.38 mass% when the oil content rate of the collect | recovered purification sludge (coarse particle content) was measured.

  In sample No. 4, in the classification process performed after the grinding process was performed in the same manner as in No. 1, the operating conditions of the cyclone classifier were the conditions of cyclone inlet pressure: 0.25 MPa and outlet pressure: 0.04 MPa. (Condition 2). In addition, the cleaning agent injected from the cleaning agent injection tube in the cleaning process has a nonionic surfactant content of 0.60% by mass as in No. 1 and an anionic surfactant content as in No. 1. It was set as the aqueous solution which is 0.60 mass% and sodium hydroxide content rate is 1.5 mass%. Except for these, the treatment was performed in the same manner as in No. 1.

  In the sample No. 4, the ratio of the coarse particles to the fine particles after the classification step is 93% by mass for the coarse particles, 7% by mass for the fine particles, and particles having a particle size of 20 μm or less in the coarse particles. The content rate was 25%. The oil content after the classification step was 3.2% by mass for the coarse particles and 17% by mass for the fine particles. Moreover, it was 0.62 mass% when the oil content rate of the collect | recovered purified sludge (coarse part) was measured.

In sample No. 5, the cleaning agent injected from the cleaning agent injection tube in the cleaning step is 0.75% by mass of the same nonionic surfactant as No. 1 and the same anionic surfactant as No. 1 In an aqueous solution having a sodium hydroxide content of 1.8% by mass. Except for this, the treatment was performed in the same manner as in No. 4.
In the sample No. 5, the ratio of the coarse particles to the fine particles after the classification step is 93% by mass for the coarse particles, 7% by mass for the fine particles, and the particles having a particle size of 20 μm or less in the coarse particles. The content rate was 25%. The oil content after the classification step was 3.2% by mass for the coarse particles and 17% by mass for the fine particles. Moreover, it was 0.35 mass% when the oil content rate of the collect | recovered purification sludge (coarse grain part) was measured.

  These results are summarized in Table 1 below.

  In sample No. 1, the grinding step was performed, and the content of particles having a particle size of 20 μm or less contained in the coarse particles after the classification step was 10% by mass. Therefore, the nonionic surfactant content was 0. 3% by mass, anionic surfactant content is 0.3% by mass, sodium hydroxide content is 0.8% by mass, and the aqueous solution content is low. The target value of the purification sludge was 0.40% by mass or less.

In sample No. 2, since the grinding process is not performed, the coarse particles after classification include secondary particles in which fine particles having a high oil content are firmly attached to the coarse particles. As a result of performing the washing process with an aqueous solution having the same detergent concentration, the oil content of the coarse particles after washing became 3.2% by mass which does not satisfy the target value of purified sludge of 0.40% by mass or less. .
In order to achieve an oil content of 0.40% by mass or less after washing with a method that does not perform a grinding process, the concentration of the detergent is high as in sample No. 3 (nonionic surfactant) It is necessary to use an aqueous solution having an agent content of 1.0 mass%, an anionic surfactant content of 1.0 mass%, and a sodium hydroxide content of 2.4 mass%.

In Sample No. 4, the grinding process was performed, but the content ratio of particles having a particle diameter of 20 μm or less contained in the coarse particles after the classification process was 25% by mass. As a result of performing the washing process with an aqueous solution having a detergent concentration almost twice that of No. 1, the oil content of the coarse particles after washing does not satisfy the target value of purified sludge of 0.40% by mass or less. It was .62% by mass.
In order to achieve the oil content of 0.40% by mass or less in the coarse particles after washing by performing the classification process under the same conditions as in sample No. 4, the detergent concentration is higher as in sample No. 5. It is necessary to use a high aqueous solution (nonionic surfactant content is 0.75% by mass, anionic surfactant content is 0.75% by mass, and sodium hydroxide content is 1.8% by mass).

  Moreover, the classification | category process with respect to the oil-containing sludge which performed the grinding process on the same conditions is performed on various conditions, The content rate of the particle | grains with a particle size of 20 micrometers or less contained in the coarse-grain fraction after a classification | category process is each 9.5. The mass%, 16 mass%, 19 mass%, 23 mass%, and 25 mass% were set. The washing process of these coarse particles is made of the same nonionic surfactant as No. 1, the same anionic surfactant as No. 1, and sodium hydroxide, and the sodium hydroxide concentration is 0.8% by mass. And using an aqueous solution in which the concentrations of the nonionic surfactant and the anionic surfactant were varied. Nonionic surfactant and anionic surfactant were changed at the same concentration.

  And the critical value of surfactant concentration required in order for the oil content rate of the collect | recovered purification sludge to become a target value (0.40 mass% or less) was investigated. The result is shown in the graph of FIG. As can be seen from this graph, the required concentration of the surfactant is 0.3% by mass when the content of the particles having a particle size of 20 μm or less contained in the coarse particles after the classification step is 20% by mass or less, The amount of surfactant used in the cleaning process can be significantly reduced.

1 Biaxial stirring device (grinding device)
2 Cyclone classifier (classifier)
3 Biaxial stirring device (cleaning device)
31 Cleaning agent injection tube 4 Solid-liquid separator

Claims (2)

A grinding process for reducing the size of particles by friction between particles for oil-impregnated granular materials containing oil consisting of coarse and fine aggregates;
Classifying the oil-containing granular material after the grinding step into coarse and fine particles so that the particles having a particle size of 20 μm or less contained in the coarse particles are 20% by mass or less;
A washing step of washing the coarse particles after the classification step in a liquid, and transferring the oil contained in the particles constituting the coarse particles to the liquid side;
A recovery step of solid-liquid separation of the liquid containing the particles after the cleaning step, and recovering the particles from which oil has been removed;
The processing method of the oil-containing granular material characterized by having.   The method for treating oil-containing granules according to claim 1, wherein the oil-containing granules are sludge of process waste water in an ironworks.

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