JPH10316962A - Gelling agent for wastewater containing oily scum and method for treating oily scum using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a treatment chemical and a treatment method capable of easily collecting and treating oily scum in sewage discharged from homes and factories. A urethane obtained by subjecting an ethylene oxide-propylene oxide random copolymer having the following characteristics (i) to (iii) to an addition reaction of an aromatic diisocyanate with an NCO- / OH-equivalent ratio of 3.5 to 8: A gelling agent consisting of a prepolymer is used. With this gelling agent,
The wastewater containing oily scum is solidified. (I) the weight ratio of ethylene oxide units to propylene oxide units is 70/30 to 90/10, (ii) the starting material for the addition reaction of ethylene oxide and propylene oxide is triol, and (iii) the triol is determined from the hydroxyl value. The average molecular weight is 6,000-9000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solidifying agent for recovering oily scum from sewage discharged from homes and factories, and a method for treating an oily scum-containing liquid using the same.

[0002] Oily scum is a liquid or solid viscous floating substance in sewage, which is composed of vegetable and animal fats and oils.

[0003]

2. Description of the Related Art Various edible fats and oils are dispersed and suspended in sewage discharged from a dining room or a kitchen at home. Examples of the edible fats and oils include vegetable oils such as sesame oil used for tempura and fried foods, and beef fat and lard contained in meat and instant noodles.

[0004] These fats and oils float up and stay near the water surface in places where the flow velocity is low, such as a headrace of a sewage treatment plant or a first sedimentation tank. If the wastewater containing such oily scum is allowed to stand for a long time, a layer of oil and fat is formed on the surface layer. Since oily scum floats on the surface layer, it is difficult to treat it with a water treatment agent or activated sludge. For this reason, they are usually collected manually, and in some cases, are further separated and then landfilled.

[0005] However, oil-based scum has a large viscosity and tackiness and is extremely difficult to handle, so that the recovery operation is extremely difficult. In addition, as regulations on landfill disposal and the resilience of local residents have become stronger, it has become increasingly difficult to secure land for disposal.

It is also conceivable to add a dispersant to wastewater containing oily scum, emulsify the wastewater and burn it together with fuel oil. However, there is a problem that not only a large-scale dedicated facility is required, but also a supply pipe to the boiler is clogged by solid fats and oils and other solid refuse.

On the other hand, Japanese Patent Application Laid-Open No. 53-108070 discloses a method of solidifying waste oil by adding water of the same weight or less and polyisocyanate of the same weight (polymeric MDI in the example) together with an amine catalyst and stirring. Is disclosed. However, when such a method of treating waste oil is applied to wastewater in which a relatively low concentration of fats and oils floats, strong stirring and mixing is required to disperse the polyisocyanate in water, and special equipment is required. I do. Further, the use of a large amount of polyisocyanate not only increases the cost but also makes it difficult to dispose of the obtained solid by burning without generating harmful gases and soot. The solid formed by the reaction between the polyisocyanate and water has a high nitrogen composition and is apt to cause carbonization, and complete combustion is not easy without external heating.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and is directed to a chemical and a method for treating oily scum in sewage, which has been extremely difficult to recover. The present invention provides a solid which can be easily converted into a solid which is easy to dispose, and which can be easily disposed of, and which does not require special equipment.

[0009]

The gelling agent for wastewater containing oily scum according to claim 1 is added to and mixed with wastewater containing oily scum having a concentration of 50% by weight or less to gel this wastewater. A gelling agent, comprising the following (i) to (ii)
A polyisocyanate is added to an ethylene oxide-propylene oxide random copolymer having the characteristic of i) by NCO
A gelling agent for wastewater containing oily scum made of a urethane prepolymer obtained by carrying out an addition reaction at − / OH− equivalent ratio of 3.5 to 8.

(I) the weight ratio of ethylene oxide units to propylene oxide units is 70/30 to 90/10, and (ii) the starting material for the addition reaction of ethylene oxide and propylene oxide has 2 to 4 active It is a low molecular weight compound having a hydrogen group, and (iii) the average molecular weight determined from the hydroxyl value is 6,000 to 9000.

[0011] With the above configuration, the wastewater containing oily scum can be easily converted into a gel that can be easily handled.

[0012] In the gelling agent for oily scum-containing wastewater according to claim 2, in the gelling agent for oily scum-containing wastewater according to claim 1, the low molecular weight compound having an active hydrogen group is triol; It is characterized in that the polyisocyanate is an aromatic diisocyanate.

[0013] The gelling agent for oily scum-containing wastewater according to claim 3 is added to the gelling agent for oily scum-containing wastewater according to claim 1 and added to wastewater containing oily scum having a concentration of 50% by weight or less. It is characterized by being performed.

[0014] In the method for treating oily scum according to claim 4, the ethylene oxide-propylene oxide random copolymer having the following features (i) to (iii):
The polyisocyanate is converted to an NCO- / OH-equivalent ratio of 3.5 to 3.5.
The wastewater is gelled by mixing and adding 5 to 100 parts by weight of a gelling agent comprising a urethane prepolymer obtained by the addition reaction in 8 with respect to 100 parts by weight of the wastewater containing oily scum. I do.

(I) the weight ratio of ethylene oxide units to propylene oxide units is 70/30 to 90/10; (ii) the starting material for the addition reaction of ethylene oxide and propylene oxide is triol; The average molecular weight determined from the value is from 6,000 to 9000
It is.

According to a fifth aspect of the present invention, there is provided a method for treating oily scum according to the fourth aspect, wherein the oily scum contained in the wastewater at a concentration of 50% by weight or less is treated. Features.

According to a sixth aspect of the present invention, there is provided a method for treating oily scum according to the fourth aspect, wherein the gelling is followed by combustion and disposal.

According to the above configuration, the gelled material can be easily discarded.

[0019] In the method for treating oily scum according to claim 7, in the method for treating oily scum according to claim 6, drying is performed to a water content of 30% or less, and the obtained solid is used as a fuel. It is characterized by using.

The hydrated urethane gel or hydrophilic urethane gel according to claim 8 is characterized in that oily scum is captured in a network structure.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, waste water containing oily scum is gelled by a gelling agent comprising a hydrophilic urethane prepolymer obtained by adding a polyisocyanate to an ethylene oxide-propylene oxide random copolymer. I do. As a result, the oily scum is captured in the hydrous urethane gel.

The wastewater containing oily scum which is suitable for the treatment according to the present invention has an oily scum concentration of 0.3 to 50% by weight.
, Especially those having a concentration of 1 to 40% by weight.

According to the method of the present invention, even if the oily scum is not only composed of vegetable and animal fats and oils such as sesame oil and tallow but also composed of engine oil, gear oil, grease, lubricating oil waste oil, etc. Can be processed. In addition, even if a large amount of solid waste is mixed in addition to such fats and oils, the same treatment can be performed.

In the present invention, the starting material of the polyaddition reaction for forming the ethylene oxide-propylene oxide random copolymer (initiator for forming the polyether polyol) may be a compound having 2 to 4, preferably 3 active hydrogen groups at the terminals. Is used (molecular weight: 1000 or less). Particularly, triol is preferable. Triols include triols having a simple structure such as glycerin, trimethylolpropane, trimethylolethane, and 1,2,6-hexanetriol, and triols obtained by partially esterifying polyhydric alcohols such as sorbitol and pentaerythritol with fatty acids. And compounds such as triethanolamine. In some cases, diols such as ethylene glycol and diethylene glycol, and tetraols such as pentaerythritol can be used.

In a polyaddition reaction for producing an ethylene oxide-propylene oxide random copolymer,
The weight ratio of ethylene oxide to propylene oxide is
70/30 to 90/10. When the weight ratio of ethylene oxide to propylene oxide is less than 70/30, that is, when the weight percent of ethylene oxide in the total amount of alkylene oxide is less than 70%, the resulting urethane prepolymer has poor diffusibility in water, Gelation performance is poor. On the other hand, when the weight ratio of ethylene oxide to propylene oxide exceeds 90/10,
% By weight of ethylene oxide in the total amount of alkylene oxide
Exceeds 90%, the resulting urethane prepolymer has a high freezing point and a high viscosity, so that it is difficult to mix and diffuse with water and to handle the urethane prepolymer. Also, the production cost of the random copolymer itself increases.

The average molecular weight of the ethylene oxide-propylene oxide random copolymer is 6,000-9000. If the average molecular weight is less than 6000, the gelling performance when the obtained hydrophilic urethane prepolymer (gelling agent) is mixed with oily scum-containing wastewater is low, and only a partial gelation is obtained to obtain a uniform gel body. I can't. Therefore, the effect of trapping and solidifying oily scum is insufficient. On the other hand, when the average molecular weight exceeds 9000, when the obtained gelling agent is mixed with oil-based scum-containing wastewater, the mixing and diffusion properties are poor and the gelation time is extremely short, so that handling is difficult. On the other hand, when the average molecular weight exceeds 9000, filtration becomes difficult and industrial production costs increase.

Here, the average molecular weight is a number average molecular weight calculated from the hydroxyl value. The hydroxyl value is measured by a known general method.

In producing the gelling agent (hydrophilic urethane prepolymer) of the present invention, if necessary, an acetalized polyol can be added to the ethylene oxide-propylene oxide random copolymer.

Examples of the acetalized polyol to be added include glycerin, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, pentaerythritol, sorbitol, and sucrose (sucrose).
And aldehydes such as acetaldehyde, propylaldehyde, butyraldehyde, and benzaldehyde. Representative acetalized polyols include mono, di, and triacetals of sorbitol with benzaldehyde, 1,
Benzaldehyde acetal of 2,6-hexanetriol and acetaldehyde acetal of trimethylolpropane.

By adding the acetalized polyol, the viscosity of the gelling agent can be reduced, and the affinity with the oily scum can be improved. In particular, since the initial viscosity of the liquid mixture when the gelling agent is added to the wastewater containing oily scum can be reduced, it is effective when treating wastewater with a high concentration of oily scum and high viscosity.

In such a case, the acetalized polyol is used in an amount of 0.5 to 10%, preferably 1 to 10%, based on the ethylene oxide-propylene oxide random copolymer.
Add ~ 3%.

As the polyisocyanate for producing the gelling agent of the present invention, any polyisocyanate that has not been derivatized such as urethane prepolymerization can be used. In particular, TDI-80 (tri- Range isocyanates wherein the ratio of 2,4-TDI to 2,6-TDI is 80/20, NDI (naphthalene diisocyanate), pure MDI (pure diphenylmethane diisocyanate), polymeric MDI (polymethylene polyisocyanate) In addition to aromatic polyisocyanates such as phenyl isocyanate) and XDI (xylene diisocyanate), HDI (hexamethylene diisocyanate), trimethylhexamethylene diisocyanate, IPDI
Aliphatic polyisocyanates such as (isophorone diisocyanate), and mixtures thereof. Particularly preferred are aromatic diisocyanates.

The isocyanate / hydroxyl group (NCO / OH) equivalent ratio in the reaction for producing a polyurethane prepolymer from the above ethylene oxide-propylene oxide random copolymer and polyisocyanate is from 3.5 to 3.5.
8 If the NCO / OH equivalent ratio is less than 3.5, the resulting polyurethane prepolymer will have poor storage stability. On the other hand, if the NCO / OH equivalent ratio exceeds 8, it is difficult to form a uniform gel because the diffusibility into water is poor.

As the inert solvent used in the present invention, xylene, toluene, hexane, heptane, isoparaffin, n-paraffin, acetone, methyl ethyl ketone,
Dioxane, dimethylformamide (DMF), dibutyl phthalate (DBP), dioctyl phthalate (DO
P), methylene chloride, 1,1,1-trichloroethane, perchloroethylene and the like are preferred.

By adding the inert solvent as described above, the solubility and dispersibility of the obtained polyurethane prepolymer in water can be remarkably increased. In particular, when acetone, methyl ethyl ketone, dimethylformamide (DMF) or the like is used, the effect is remarkable, and a uniform gel can be obtained by simply dispersing in waste water with little stirring.

[0036]

【Example】

<Synthesis example of urethane prepolymer (gelling agent)> One synthesis example (synthesis example 2) of the urethane prepolymer used in the present invention will be described below.

0.8% by weight of potassium hydroxide is added to glycerin, and dehydration and nitrogen replacement are performed under reduced pressure. A mixed alkylene oxide obtained by mixing ethylene oxide and propylene oxide at a weight ratio of 80/20 is reacted at a reaction temperature of 100 to 13
At 0 ° C. and at a reaction pressure of 1-4 kg / cm 2,
The reaction is completed in 5 hours.

To the reaction product is added 3% by weight of synthetic magnesium silicate, and the mixture is neutralized under reduced pressure at a temperature of 110 to 120 ° C. for about 1 hour. Thereafter, the mixture is filtered with a filter to obtain a highly pure and transparent ethylene oxide-propylene oxide random copolymer. The product after filtration has a heavy metal content of 10 ppm or less and a water content of 0.5% or less. If necessary, the above-mentioned acetalized polyol is added.

Next, TDI-80 was added, and the temperature was 80 ° C.
The reaction is completed by stirring in a stream of nitrogen for 2 hours.

The obtained urethane prepolymer is suitable for a solidifying agent because it is water-soluble and has a viscosity that is easy to handle. The content of the free isocyanate group in the obtained urethane prepolymer is 3 to 8% by weight.

The inert solvent can be added to the urethane prepolymer after completion of the reaction at 15 to 70% by weight, if necessary, at a stage where the temperature is lowered to 50 ° C.

The following Table 1 summarizes Synthesis Examples 1 to 9 obtained in the same manner as in Synthesis Example 2.

[0043]

[Table 1] <Oil-based scum-containing wastewater> The oil-based scum-containing wastewater used in the test is shown in Table 2 below.

The concentration of the oily scum was measured by removing the water by heating and drying the wastewater containing oily scum collected in the beaker at 105 ° C. for 8 hours.

In Table 2, the concentration of oily scum in wastewater examples 5 to 8 was carried out by a physical method such as normal pressure or pressure flotation, or centrifugation.

When the concentration of the wastewater containing oily scum is increased to 50% or more, the fluidity is extremely low, so that it becomes difficult to mix the wastewater with the gelling agent. In addition, the process operation itself for concentration becomes very difficult.

[0047]

[Table 2] <Gelling of oily scum-containing wastewater and its evaluation> To 100 parts by weight of the oily scum-containing wastewater of the above wastewater example, 5 to 100 parts by weight of the urethane prepolymer of the above synthesis example was added,
After mixing with a stir bar or spatula until uniform,
It was allowed to stand until it solidified. The temperature during the stirring and standing is 20 to 25 ° C.

Evaluation of gelation was performed as follows.

(Shape Retention) The obtained gel was cut into a cube of 3 cm square or 5 cm square, or a short cylinder having a diameter of 5 cm and a height of 5 cm, and was checked for any change in shape when allowed to stand on a flat plate for one day. Observed. A sample in which no deformation was observed was evaluated as ○, a device in which the bottom surface was slightly expanded was evaluated as △, and an image in which it was clearly deformed was evaluated as ×.

(Adhesion Resistance) When the obtained gel was cut with scissors, it was observed whether or not the scissors adhered to the blade. A sample in which no adhesion was observed was evaluated as ○, a sample in which adhesion was partially observed was evaluated as Δ, and a sample in which adhesion was significantly observed was evaluated as ×.

(Oil Separation Resistance) The presence or absence of seepage of the oil component on the surface of the gelled product cut out at the time of evaluation of the shape retention is judged by a tactile sensation by hand and visual observation. The case where it was determined that no bleeding was observed was evaluated as ○, and the case where it was determined that there was bleeding was evaluated as x.

(Measurement of Gelation Time) After mixing the wastewater containing oily scum and the urethane prepolymer (gelling agent), the time until the whole became a gel was measured.

Table 3 below summarizes the gelling conditions and evaluation results.

[0054]

[Table 3] As is known from Examples 1 to 8 in the above table, 5 parts by weight or more of the gelling agent (urethane prepolymer) obtained in Synthesis Examples 1 to 7 was added to 100 parts by weight of oily scum-containing wastewater. It was possible to convert it into a gelled material that was easy to handle simply by leaving it to stand.

In all of Examples 1 to 8, the mixing of the wastewater and the gelling agent was achieved with a slight stirring using a stirring rod. The obtained gel was in the form of a purine to konjac, and was easy to handle because there was no stickiness on the gel surface.

As can be seen from the gelation time measurement results for Examples 1 to 8, the greater the amount of the gelling agent added to the wastewater, the faster the gelation. However, as is known from the results of Example 2, the addition amount of the gelling agent was 5 phr (waste water 1
Gelation was completed within a sufficiently short time even with a relatively small amount (5 parts to 00 parts).

As can be seen from Comparative Examples 1 to 3 in the above table, when the gelling agents of Synthesis Examples 8 to 9 were used, no easily handled gel was obtained. In all of Comparative Examples 1 to 3, the gelation time was extremely short, but the mixing and diffusibility with wastewater was poor, and a uniform gelled product could not be obtained. As shown in Table 1, in the gelling agent of Synthesis Example 8, the number of functional groups of the starting material was 6, and it is considered that an excessively large number of functional groups caused gelation failure. The gelling agent of Synthesis Example 9 has the same starting material as that of Example (Synthesis Examples 1 to 7), but the average molecular weight of the base ethylene oxide-propylene oxide random copolymer is 10,000.
0, which is considered to be the cause of poor gelation when the molecular weight is too high.

When the gel obtained in the above example was left in the open air, water was gradually separated. Further, concentration by forced drying such as heating and blowing drying was easy, and coarse pulverization was also possible to promote such concentration. No reattachment was observed after grinding.

The gels obtained in Examples 1 to 8 were cut into 1 to 2 cm squares and dried at 105 ° C. for 5 hours to obtain solids having a water content of 30% or less and easier to handle. . When the match fire was brought close to this, it ignited easily and burned smoothly.

The solid obtained by drying the gelled product obtained in the examples has an oil content of 2% or more, and the polymer structure forming the solid mainly consists of ethylene oxide and propylene oxide (70% or more). It is. Also,
The nitrogen composition ratio in the element composition is 4% or less. It is considered that combustion and disposal are easy for such a reason.

That is, the gelled substance produced by the method of the present invention can be easily burned and discarded. For this reason, it is not necessary to use a method such as landfill disposal which has a large burden on the environment and a large cost for implementation. Further, a special combustion device is not required for the combustion and disposal. Therefore, it is possible not only to cope with environmental problems but also to reduce costs for disposal.

Since the combustible solid after drying is easy to store and transport, it can be used as a solid fuel.

[0063]

According to the present invention, wastewater containing oily scum, which is extremely difficult to handle as it is, can be easily converted into solid matter which can be easily handled. Moreover, the obtained solid can be easily burned and discarded. Therefore, not only can environmental problems be addressed, but also the cost for treating oily scum can be significantly reduced.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09K 3/00 103 C09K 3/00 103L C10L 5/46 ZAB C10L 5/46 ZAB 5/48 ZAB 5/48 ZAB

Claims (8)

[Claims] 1. A gelling agent which is added to and mixed with wastewater containing oily scum to gel the wastewater, wherein the ethylene oxide-propylene oxide random copolymer has the following features (i) to (iii): A gelling agent for oily scum-containing wastewater comprising a urethane prepolymer obtained by subjecting a polyisocyanate to an addition reaction at an NCO- / OH-equivalent ratio of 3.5 to 8. (I) the weight ratio of ethylene oxide units to propylene oxide units is 70/30 to 90/10, and (ii) the starting material for the addition reaction of ethylene oxide and propylene oxide has 2 to 4 active hydrogen groups at its terminals. (Iii) an average molecular weight determined from the hydroxyl value of 6000.
９9000. 2. The gelling agent according to claim 1, wherein the low molecular weight compound having an active hydrogen group is a triol, and the polyisocyanate is an aromatic diisocyanate. 3. The gelling agent according to claim 1, which is added to and mixed with wastewater containing oily scum having a concentration of 50% by weight or less. 4. An ethylene oxide-propylene oxide random copolymer having the following features (i) to (iii): a polyisocyanate and an NCO- / OH-equivalent ratio of 3.
A gelling agent comprising a urethane prepolymer obtained by performing an addition reaction at 5 to 8 is applied to a wastewater 100 containing oily scum.
A method for treating oil-based scum, wherein the wastewater is gelled by mixing and adding 5 to 100 parts by weight with respect to parts by weight. (I) the weight ratio of ethylene oxide units to propylene oxide units is 70/30 to 90/10; (ii) the starting material for the addition reaction of ethylene oxide and propylene oxide is triol; Average molecular weight of 6000
９9000. 5. The method for treating oily scum according to claim 4, wherein oily scum contained in wastewater at a concentration of 50% by weight or less is treated. 6. The method for treating oily scum according to claim 4, wherein the waste is burned after the gelation. 7. The method for treating oily scum according to claim 6, wherein drying is performed to a water content of 30% or less, and the obtained solid is used as a fuel. 8. A hydrous urethane gel or a hydrophilic urethane gel, wherein oily scum is captured in a network structure.